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Single ZnO Hexagonal Nanodisk Photodetectors

Mohammad R. Alenezi,1 Talal H. Alzanki,1 Abdullah S. Alshammari,2 Simon J. Henley,3 S. R. P. Silva 3

[1] College of Technological Studies, PAAET, P.O. Box 42325 Shuwaikh, (Kuwait) [2] Department of Physics, College of Science, University of Hail, P.O. Box 2440, Hail, (KSA) [3] Advanced Technology Institute, University of Surrey, Guildford, GU2 7XH (UK)

[email protected]

Abstract Nanostructured photodetectors have been reported extensively in the last ten years with a great focus on single nanowire photodetectors. The reason behind this focus on nanowire based devices could be related to the challenges facing the synthesis of nanostructures with different morphologies. Using nanostructures in photodetectors is advantageous and expected to enhance the photosensitivity greatly due to two key aspects. The first aspect is that nanostructures usually have a significantly large surface to volume ratio as well as high density of deep level surface trapping states. Both of these properties allow longer lifetime for the photogenerated carriers in the nanostructure. The other aspect is the decreased transit time of carriers because of the reduction in dimensionality of the active area in nanostructured devices. Truthfully, combining these two aspects together may lead to a significant photoconductive gain. [1] For nanostructured photodetectors, the performance depends greatly on the morphological properties of nanostructures. [2-3] Therefore, it is essential to develop well-controlled synthesis techniques to fabricate highly functional materials for practical devices. Controlled hydrothermal method to produce single crystal ZnO hexagonal nanodisks using a mixed solution of zinc sulphate and hexamethylenetetramine without the need of catalysts, substrates, or templates at low temperature

-semiconductor-metal photodetectors were fabricated based on individual single crystal ZnO hexagonal nanodisks (Figure 1). The fabricated photodetectors show high photosensitivity and fast response and recovery times. The enhancement in the device performance is attributed to the absence of grain boundaries in the single crystal ZnO nanodisk, high surface to volume ratio, and the polar exposed facets. References [1] C. Soci, A. Zhang, B. Xiang, S. A. Dayeh, D. P. R. Aplin, J. Park, X. Y. Bao, Y. H. Lo, D. Wang, Nano Lett. 7, (2007) 1003 1009. [2] M. R. Alenezi, S. J. Henley, N. G. Emerson, S. R. P. Silva, Nanoscale, 6, (2014) 235 247. [3] M. R. Alenezi, A. S. Alshammari, K. D. G. I. Jayawardena, M. J. Beliatis, S. J. Henley, S. R. P. Silva J. Phys. Chem. C, 117, (2013) 17850 17858

Figure 1: (a) Schematic and (b) SEM image of the hexagonal nandisk photodetector (2.5 µm space between the electrodes)

Influence of plasma reactor parameters on carbon coating of iron nanoparticle

M. Reza Sanaee, O. Arteaga, E. Bertran

FEMAN Group, Institute of Nanoscience and Nanotechnology (IN2UB), Dep. Applied Physics

and Optics, Universitat de Barcelona, Martí Franquès, 1, E08028 Barcelona, Spain

[email protected]

Despite of numerous interests in iron nanoparticles (INPs), its rapid environmental degradation is still a serious problem; which limits the advantages of superparamagnetic properties and its potential applications. To overcome this difficulty, carbon coating is one of the best solutions for protecting INPs. Furthermore, carbon coating can improve electrical conductivity, mechanical performance and biocompatibility of the materials [1]. In this research, plasma method is used to synthesize carbon coated iron nanoparticle (CCINPs). The effective parameters on morphologies and carbon shell protection were studied. Based on the images taken by transmission electron microscopy (TEM), INPs were produced and partially coated (Figure 1). By increasing current and pressure condition up to atmospheric pressure and despite of increasing iron precursor concentration from 0.5% to 3.5% (seven times), we observed that INPs were completely coated by carbon shell. Figure 2 Illustrate complete coating of a single INPs. Besides, the absence of oxygen in the nanoparticles has been determined by energy-dispersive X-ray analysis reported results of the magnetic characterization of CCINPs show their superparamagnetic nature and the total absence of oxidation due to the high sealing efficiency of carbon shell.

Figure 1. TEM image of partially coated INPs

Figure 2. TEM image of a CCINPs

Figure 3. The absence of oxygen in the spectrum confirms the protection of the nanoparticles from oxidation. Reference: 1- S. Liu, X. Tang, Y. Mastai, I. Felnerc and A. Gedanken, Nanoscale, 2 (2010) 2281-2285.

Wet-Spinning Multifunctional Carbon Nanotube/Polymer Composite Fibers

José Antonio Benedico1, Rebeca Marcilla2, Eneko Azaceta3, Andrés Seral-Ascaso1, Enrique García-

Bordejé1, Vicente L. Cebolla1, Rosa Garriga4, Edgar Muñoz1

1 Instituto de Carboquímica ICB-CSIC, C/Miguel Luesma Castán 4, 50018 Zaragoza, Spain 2 Electrochemical Process Unit, Institute IMDEA Energy, Avda. Ramón de la Sagra 3, 28935 Móstoles,

Madrid, Spain 3 IK4-CIDETEC, Parque Tecnológico de San Sebastián, Paseo Miramón 196, 20009 Donostia-San

Sebastián, Spain 4 Departamento de Química Física, Universidad de Zaragoza, 50009 Zaragoza, Spain

[email protected]

Abstract Remarkable progress in the fabrication of carbon nanotube composite fibers has resulted through the development of the wet-spinning technique pioneered by Vigolo et al. [1] This process implies the fabrication of gel fibers as a result of the collapse of surfactant-stabilized carbon nanotube dispersions when injected into a coagulation bath. When dried, those gel fibers become solid fibers with high carbon

technologies, such as melt-spinning or electrospinning. We here report how this wet-spinning method provides carbon nanotube composite fibers with tunable properties, which mainly depend on the composition of the coagulation bath used. Polymers such as polyvinyl alcohol (PVA) [2-5], polyethylenimine (PEI) [6], and a polymeric ionic liquid [7] have been here investigated as coagulants. Remarkable transport-, supercapacitor- and electrochemical actuation properties are demonstrated for these coagulation wet-spun fibers, which offer promise for a variety of applications [2-4]. This work has been funded by the Fundación Domingo Martínez (Ayuda a la Investigación 2013). References [1] B. Vigolo, A. Pénicaud, C. Coulon, C. Sauder, R. Pailler, C. Journet, P. Bernier, P. Poulin, Science,

290 (2000) 1331. [2] A. B. Dalton, S. Collins, E. Muñoz, J. M. Razal, V. H. Ebron, J. P. Ferraris, J. N. Coleman, B. G.

Kim, R. H. Baughman, Nature, 423 (2003) 703. [3] A. B. Dalton, S. Collins, J. Razal, E. Muñoz, V. H. Ebron, B. G. Kim, J. N. Coleman, J. P. Ferraris, R.

H. Baughman, J. Mater. Chem., 14 (2004) 1. [4] E. Muñoz, A. B. Dalton, S. Collins, M. Kozlov, J. Razal, J. N. Coleman, B. G. Kim, V. H. Ebron, M.

Selvidge, J. P. Ferraris, R. H. Baughman, Adv. Eng. Mater., 6 (2004) 801. [5] J.M. Razal, J.N. Coleman, E. Muñoz, B. Lund, Y. Gogotsi, H. Ye, S. Collins, A.B. Dalton, R.H.

Baughman, Adv. Funct. Mater., 17 (2007) 2918. [6] E. Muñoz, D.-S. Suh, S. Collins, M. Selvidge, A. B. Dalton, B. G. Kim, J. M. Razal, G. Ussery, A. G.

Rinzler, M. T. Martínez, R. H. Baughman, Adv. Mater., 17 (2005) 1064. [7] R. Marcilla et al., submitted.

Etch-free method to prepare nanoporous metal layers using directed self-assembly

M. Bernal Salamanca

a, C. Simaoa, Marianna Sledzinskaa and C. M Sotomayor Torresa,b

a Catalan Institute of Nanoscience and Nanotechnology ICN2, Campus de la UAB, Barcelona 08193,

Spain b Catalan Institute of Research and Advanced Studies, Barcelona 08010 , Spain;

[email protected]

Abstract The self-assembly of block copolymers (BCPs) as thin films on substrates is a simple and cost-effective method to obtain high density arrays of lines or dots with lateral dimensions below 20 nm and it is compatible with standard lithography techniques.[1, 2] The directed self-assembly of the BCPs can provide extensive control of the level of order of the nanostructures arrays[3] but also on their orientation and alignment.[4] Such characteristics make the directed self-assembly (DSA) of BCPs a valuable methodology for cost-effective nanofabrication compatible with the semiconductor industry.[5] Being synthetically tuneable molecules, block copolymers can be modified with functional groups selectively, i.e., functionalise one of the polymer block backbone, to interact specifically with particles or dyes. Then, upon DSA, the particles or dyes are confined to one of the phases.[6] Recently, the incorporation of inorganic or metal nanoparticles with BCPs led to an increased chemical contrast needed, e.g., to improve the lithographic yield of the BCPs systems.[2] Nevertheless, this application usually requires the selective removal of one of the blocks of the BCP.

In the present work, aluminium and chromium nanoporous layers were fabricated by metal evaporation on the block copolymer poly(styrene-b-ethylene oxide) thin film. It was observed that aluminium and chromium atoms deposit selectively on the PS block of the BCP surface, thus the latter acted as scaffold surface without the need of an etch step. The chosen polymer templates have three different molecular weights to reach different lateral dimensions and permitted the fabrication of periodic nanopores hexagonal arrays with a pitch ranging from 40 nm to 150 nm and pore diameters of 18 to 90 nm, respectively. The metal layers were fabricated in polymer templates supported in quartz substrates, to study the effect of the metal nanostructuration on the optical properties, and silicon substrates for lithographic applications.

The research leading to these results received funding from the European Union FP7 project LAMAND under grant agreement n° 245565 and the Spanish MINECO under the project TAPHOR (contract nr. MAT2012-31392).

References

[1] M. Salaun, M. Zelsmann, S. Archambault, D. Borah, N. Kehagias, C. Simao, O. Lorret, M. Shaw, C. M. Sotomayor Torres, M. A. Morris, Journal of Materials Chemistry C (2013) 1 3544.

[2] T. Ghoshal, R. Senthamaraikannan, M. T. Shaw, J. D. Holmes, M. A. Morris, Nanoscale (2012) 4 7743.

[3] D. Borah, C. D. Simao, R. Senthamaraikannan, S. Rasappa, A. Francone, O. Lorret, M. Salaun, B. Kosmala, N. Kehagias, M. Zelsmann, C. M. Sotomayor-Torres, M. A. Morris, Eur. Polym. J. 49 3512.

[4] C. Simão, A. Francone, D. Borah, O. Lorret, M. Salaun, B. Kosmala, M. T. Shaw, B. Dittert, N. Kehagias, M. Zelsmann, M. A. Morris, C. M. Sotomayor-Torres, J. Photopolym. Sci. Technol. (2012) 25 239.

[5] J. Bang, U. Jeong, D. Y. Ryu, T. P. Russell, C. J Hawker, Adv. Mater. (2009) 21 4769; M. R. Jones, K. D. Osberg, R. J. MacFarlane, M. R. Langille, C. A. Mirkin, Chem. Rev. (2011) 111 3736.

[6] M. J. Pavan, R. Shenhar, J. Mater. Chem. (2011) 21 2028.

Figures

Figure 1. SEM images of nanoporous aluminium and chromium layers template by three different PS-b-PEO molecular weights.

0 1 2 3 4 5

30

40

50

60

70

80

90

Po

re s

ize

(n

m)

Metal Thickness (nm)

Al-102K Al-227K

0 1 2 3 4 5

10

20

30

40

50

60

70

80

90

Po

re s

ize

(n

m)

Metal Thickness (nm)

Cr-42K Cr-102K Cr-227K

Figure 2. Dependence of the nanoporous lateral size on the nominal Al and Cr layer thickness templated by different PS-b-PEO molecular weights.

Electrical model for characterizing Chemical Vapour Deposition graphene

Alberto Boscá, Jorge Pedrós, Javier Martínez, Thorben Casper, Fernando Calle.

Instituto de Sistemas Optoelectrónicos y Microtecnología, UPM, E.T.S.I. de Telecomunicación, Av. Complutense 30, Madrid 28040, Spain

[email protected]

Abstract

Due to its extremely small thickness (0.35 nm), graphene is an intrinsic 2D nanomaterial. As in many other nanomaterials, its unique properties are derived from its exceptional dimensions. One of these properties is its linear dispersion equation that implies charge carriers with extraordinary high mobility. Therefore, the electronic properties of the material can lead to a big improvement in the performance of known electronic devices, or even result in novel devices for a post-silicon era.

In this work, we explain a method to characterize graphene using electrical measurements in graphene field-effect transistors (GFET) devices. Our goal is to obtain the material electronic properties from the output characteristics of one GFET. For the previous purpose, we will need to apply a physical model that allows us to correlate the electronic behavior of a GFET with the material properties.

There are several models used for graphene. Some of them are based strongly on solid state physics [1], [2], including even quantum effects at high magnetic fields. Others are more focused on FET devices [3]. The model used in this work is based on first principles and is described thoroughly in [4]. The main advantage of this model is that most of the equations are directly derived from the energy-momentum dispersion relation from graphene, so it is straightforward to obtain the carrier concentration and the current in terms of the gate voltage (Vg) of the transistor, and even local characteristics along the channel. Also, the temperature is an explicit parameter on the equations, and the shifts in the Dirac point are explained with a fixed surface charge. With this model we are able to obtain a quick characterization of the material electrical properties from just a transistor structure (Fig. 1).

The fitting to this model is done by using the measured IDS vs. VG curves of a real device. All the relevant parameters, such as the oxide capacitance (Cox), voltage applied (VDS), gate metal work function, gate length (Lg), and width (w), among others must be introduced in the model. For fitting the experimental measurements into the model, we work with the transconductance (gm

We have used different measurements from previous publications, like suspended devices [5] (see Fig. 3), and CVD graphene transistors [3] (see Fig. 4).

), in order to extract some fundamental values from the shape, such as the maximum and minimum transconductance, the Dirac point, or the curve slope in several voltage ranges, as detailed in Fig.2. Using these parameters from real data, we use the model to obtain the electron and hole mobilities, the total serial resistance and the total density of fixed charge.

Effects due to scattering produced by defects in the surface, either from the material or due to processing, are not included in this model, somewhat limiting its validity for some devices. Also, large differences between electron and hole mobilities cannot be explained properly in this theoretical framework. More work is underway to increase the physical effects taken into account, and therefore to improve the results and widen the range of devices to which the explained procedure is applicable.

Acknowledgements

Ministerio de Economía y Competitividad, Projects TEC 2010-19511 Readi and CSD 2009-00046 RUE

References

[1] K.S. Novoselov, A.K. Geim et al., Nature, 438 (2005) 197.

[2] S. Adam, E. Hwang et al., PNAS, 104 (2007) 18392.

[3] H. Wang, A. Hsu et al., IEEE Transactions on Electron Devices, 58 (2011) 1523 .

[4] J. Champlain, Journal of Applied Physics, 109 (2011) 084515.

[5] K. Bolotin, K. Sikes et al., Physical Review Letters, 101 (2008) 1.

Figures

Fig. 4: Model applied to a CVD graphene transistor from reference [3]

Fig. 3: Fit for a suspended graphene device in [5] at low temperature.

Fig. 2: Relevant parameters obtained from real data transconductance.

Fig. 1: Sample with CVD-graphene transistor devices used for batch-fitting to the model.

Aqueous colloidal processing and liquid-phase assisted spark plasma sintering of nanostructured SiC reinforced with carbon nanotubes

Víctor M. Candelario

a,b, Zhijian Shen c, Rodrigo Moreno b, Ángel L. Ortiz a

a Departamento de Ingeniería Mecánica, Energética y de los Materiales, Universidad de

Extremadura, 06006 Badajoz, Spain. b Instituto de Cerámica y Vidrio, Consejo Superior de Investigaciones Científicas, 28049 Madrid,

Spain. c Department of Materials and Environmental Chemistry, University of Stockholm, 10691

Stockholm, Sweden

[email protected]

Liquid-phase-sintered (LPS) SiC is a very hard ceramic with great potential for its use in tribological applications. Several processing strategies have been developed to improve the wear resistance of the LPS SiC ceramics, namely, reduction in the content of sintering additives, hardening of the intergranular phase through in-situ nitriding, reduction in the cation size of rare-earth oxides used as sintering additives, refinement of the grain size, and grain lengthening. Also, carbon nanotubes (CNTs) are being introduced in a variety of polycrystalline ceramic matrices to improve the wear performance, as they act as reinforcements while reducing the friction coefficient. A critical step in this area is the preparation of homogeneous dispersions of CNTs among the ceramic particles without CNTs agglomeration, especially if the ceramic particles have nanometre sizes.

With these premises in mind, here we have studied the aqueous colloidal processing of powder mixtures of SiC and Y3Al5O12 nano-powders with carbon nanotubes. The study involves both the rheological characterization of aqueous suspensions and the microstructural characterization of the resulting powder mixtures obtained by the freeze-drying of the suspensions. Then was densied by spark plasma sintering under different conditions of temperature, pressure and holding time.

References [1] V.M. Candelario, R. Moreno, A.L. Ortiz, J Eur Ceram Soc, 34 (2014) 555-63. [2] N.P. Padture, Adv Mater 17 (2009) 1767-70. [3] O. Borrero-López, A. Pajares, A.L. Ortiz, F. Guiberteau, J Eur Ceram Soc, 11 (2007) 3359-64. [4] R. Moreno, A. Salomoni, S.M. Casthano, J Eur Ceram Soc, 4 (1998) 405-16. [5] V.M. Candelario, M.I. Nieto, F. Guiberteau, R. Moreno, A.L. Ortiz, J Eur Ceram Soc, 10 (2013) 1685-94. [6] T.S. Suzuki, Y. Sakka, K. Nakano, K. Hiraga, J Am Ceram Soc 9 (2001) 2132-4. Figures

Figure 1.- Sintered materials (A) SiC without CNTs and (B) SiC with CNTs by spark plasma sintering

Processing of SiC nano-ceramics with multilayed architecture

Víctor M. Candelario a,b, Zhijian Shen c, Rodrigo Moreno b, Ángel L. Ortiz a

a Departamento de Ingeniería Mecánica, Energética y de los Materiales, Universidad de

Extremadura, 06006 Badajoz, Spain. b Instituto de Cerámica y Vidrio, Consejo Superior de Investigaciones Científicas, 28049 Madrid,

Spain. c Department of Materials and Environmental Chemistry, University of Stockholm, 10691

Stockholm, Sweden

[email protected]

Silicon carbide is one of the most promising materials for thermal protection system (TPS) of future reusable spacecraft because of its low density, excellent high temperature mechanical properties and self passivating behavior in oxidizing environment. However, its low fracture toughness remains a major concern for its widely application in severe environment. The key factor for improving toughness is the presence of weak interfaces or interlayers which allow energy dissipation before fracture through mechanisms of crack deflection, pull-out and bridging of fibre or whisker, and interface delamination. For these reasons SiC-based composites with different types of carbon display improved toughness. In this study we use three different reinforcements, namely carbon nanotubes, graphene and carbon black and present a microsturctural architecture based on the stacking of different layer alternating layers of nano-SiC without reinforcement and of nano-SiC layers with carbon nanotubes, graphene or carbon black.

References [1] V.M. Candelario, R. Moreno, A.L. Ortiz, J Eur Ceram Soc, 34 (2014) 555-63. [2] N.P. Padture, Adv Mater 17 (2009) 1767-70. [3] O. Borrero-López, A. Pajares, A.L. Ortiz, F. Guiberteau, J Eur Ceram Soc, 11 (2007) 3359-64. [4] R. Moreno, A. Salomoni, S.M. Casthano, J Eur Ceram Soc, 4 (1998) 405-16. [5] O. Borrero-López, A.L. Ortiz, F. Guiberteau, N.P. Padture. J Am Ceram Soc, 8 (2005) 2159 63. [6] V.M. Candelario, M.I. Nieto, F. Guiberteau, R. Moreno, A.L. Ortiz, J Eur Ceram Soc, 10 (2013) 1685-94. [7] T.S. Suzuki, Y. Sakka, K. Nakano, K. Hiraga, J Am Ceram Soc 9 (2001) 2132-4. [8] E. Ciudad, O. Borrero-López, F. Rodríguez-Rojas, A.L. Ortiz, F. Guiberteau. J Eur Ceram Soc. 2 (2012) 511 6. [9] W.S. Yang, S. Biamino, E. Padovano, L. Fuso, M. Payese, S. Marchisio, D. Vasquez, C. Vega bolívar, P. Fino, C. Badini. Comp Scienc and Techno. 72 (2012) 675-80.

Nanostructured epoxy based thermosetting systems modified with poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymer to enhance fracture toughness

L. Cano, D. H. Builes, A. Tercjak

Group `Materials + Technologies´. Dpto. Ingeniería Química y del Medio Ambiente. Escuela Politécnica/Eskola Politeknikoa. Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU).

Plaza Europa 1, 20018 Donostia-San Sebastián, Spain. [email protected]

Abstract

Epoxy resins are one of the most widely used thermosetting polymers due to their good mechanical and thermal properties, high chemical and corrosion resistance and low shrinkage during curing. These properties lead to their several applications in adhesives, surface coatings, moulds, and aerospace and electronics industries, among others [1]. However, one of their main drawbacks is their low toughness. There have been many studies in which rubbers and thermoplastics were employed in order to increase the toughness of thermosets. In this field, one of the most effective methods to improve epoxy toughness is their modification with block copolymers, which also create thermosetting materials with ordered microphase-separated structures [2-4].

The triblock copolymer poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (EPE) has already been used before to modify phenolic, unsaturated polyester and epoxy resins. Already published studies about the blend of DGEBA epoxy resin with poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymer revealed that different macro- or microseparated morphologies were obtained depending on the content of block copolymer in the matrix, molar ratio between blocks, molecular weight of the block copolymer and the curing cycle carried out [5-9]. In our work, the EPE triblock copolymer was employed as modifier of a DGEBA based epoxy matrix with the aim to obtain nanostructured thermoset systems with improved mechanical properties. Different contents of a triblock copolymer up to 50 wt % were added to the matrix in order to study the influence of the content of block copolymer on the morphology, mechanical and surface properties of the epoxy system.

The morphology of the blends and the size of the microseparated phase were investigated by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The optical transparency was investigated by UV-vis spectroscopy. The mechanical properties measurements were carried out by the universal testing machine (MTS) performing flexural and fracture toughness tests. The glass transition temperatures as well as the curing behavior were determined by differential scanning calorimeter (DSC).

Epoxy based nanostructured thermosetting systems modified with different contents of poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymer were successfully synthetized. The curing process was carried out at 25 ºC owing to the lower critical solution temperature (LCST) behavior of the EPE block copolymer. The addition of the triblock copolymer to the epoxy resin caused a delay on the time of the curing reaction as well as a decrease in the Tg of the systems compared to the neat epoxy resin Tg, due to the plasticization effect provoked by the addition of the block copolymer. This indicated the partial miscibility between EPE block copolymer and DGEBA epoxy resin and in particular between PEO block and DGEBA resin.

As was confirmed by AFM (Figure 1) and TEM, the cured samples showed well nanostructured morphologies up to 25 wt % EPE content. As a result of the interactions between PEO block and epoxy resin, this block is miscible with epoxy resin and consequently PPO appeared as a microseparated phase. The morphology obtained resulted to be dependent on the EPE block copolymer content as it changed from spherical structure to worm-like structure with the content of block copolymer. In the case of 50 wt % EPE content, a macroseparated morphology could be observed. Regarding the mechanical properties (Figure 2), both flexural modulus and fracture toughness (in terms of critical stress intensity factor, K IC) were analyzed. The flexural modulus decreased whereas the toughness improved considerably with 5 and 15 wt % EPE block copolymer content and it almost remained the same with 25 wt % content if compared with neat epoxy system. UV-vis measurements mainly indicated a decrease in the transmittance with the increase of EPE block copolymer content. This decrease of transmittance was also reflected in the visual appearance of the samples, although all samples except for 50 wt % EPE sample remained transparent.

References

[1] D Ratna, Handbook of thermoset resins, iSmithers Rapra Technology, Shrewsbury, 2009 [chapter 3].[2] E Girard-Reydet, H Sautereau, JP Pascault, Polymer, 40 (1999) 1677.[3] JM Dean, NE Verghese, HQ Pham, FS Bates, Macromolecules, 36 (2003) 9267.[4] J Liu, ZJ Thompson, HJ Sue, FS Bates, MA Hillmyer, M Dettloff, G Jacob, N Verghese, H Pham,Macromolecules, 43 (2010) 7238. [5] Q Guo, R Thomann, W Gronski, Macromolecules, 35 (2002) 3133.[6] P Sun, Q Dang, B Li, T Chen, Y Wang, H Lin, Q Jin, D Ding, Macromolecules, 38 (2005) 5654. [7] M Larrañaga, N Gabilondo, G Kortaberria, E Serrano, P Remiro, CC Riccardi, I Mondragon, Polymer,46 (2005) 7082. [8] M Larrañaga, E Serrano, MD Martin, A Tercjak, G Kortaberria, K De la Caba, CC Riccardi, IMondragon, Polymer International, 56 (2007) 1392. [9] L Cano, DH Builes, A Tercjak, Polymer, (2014), DOI: 10.1016/j.polymer.2014.01.005.

Figures

Figure 1. AFM phase images (1 µm x 1 µm) of a) neat epoxy, b) 5 wt % EPE/epoxy and c) 25 wt % EPE/epoxy systems.

Figure 2. Critical stress intensity factor (K IC) of the cured neat epoxy system and all EPE/epoxy systems.

The Effect of Varying Injection Volumes of Surfactant and Polymer on Oil Recovery

Bo Hyun Chon, Sung Bum Jang

INHA University, Incheon 402-751, Korea

[email protected]

Abstract Surfactant-polymer flooding, a kind of chemical flooding to produce residual oil after waterflood, is designed to increase additional oil recovery from the reservoir. In this study, a laboratory surfactant-polymer flooding experiment was performed to investigate the effect of injection volume of each solution on the oil recovery. A series of surfactant-polymer flooding experiments have been performed to find the optimal recovery efficiency condition. When a surfactant and polymer combination is injected progressively into the reservoir through injection wells the slug moves towards the production well by water drive. In these processes, several interactions between the surfactant and reservoir fluids (crude oil, brine, etc.) such as the creation of a microemulsion phase, adsorption to the rock, wettability alteration, and reduction of interfacial tension occur because of the injection [1,2]. The surfactant helps oil recovery through oil solubilization and mobilization. The injection of a surfactant lowers the interfacial tension between crude oil and formation water and decreases the capillary forces inside the pore. The surfactant is dissolved in either water or oil at the reservoir to form a microemulsion, which forms an oil bank [3]. The formation of an oil bank and subsequent maintenance of sweep efficiency and pressure gradient by injection of a polymer and chase water increase the oil recovery significantly [4-6]. The polymer controls water-oil mobility ratio to achieve a favorable value such that the injected fluid does not bypass the displaced fluid. By adding polymer to water, the viscosity of water is increased and aqueous phase permeability is decreased. The reduction of water mobility improves the displacement conditions for increasing the oil recovery. The phase behavior test was carried out to observe the conditions required to generate a microemulsion system between surfactant and crude oil. A combination of a 2.5 wt% surfactant solution with 1.5 wt% of salinity was found to be optimal for injection experiments. In the surfactant-polymer flooding test, approximately 0.6 pore volume (PV) of slug was injected into the core. The injected volumes of the surfactant and polymer were varied in each test. The oil recovery after water flooding by the surfactant-polymer injection ranged from 13.6% to 28.6%. The highest oil recovery of 28.6% was obtained by injecting 0.1 PV of surfactant and 0.5 PV of polymer. Acknowledgement The authors thank the financial support by the Ministry of Trade, Industry and Energy (MOTIE) for the Korea Energy and Mineral Resources Engineering Program and the Special Education Program for Offshore Plant for this project. References

[1The SPE/DOE 14th Symposium on Improved Oil Recovery (2004).

[2] L.L. Schramm, Surfactants: Fundamentals and Applications in the Petroleum Industry, Cambridge University Press, Publications, New York (2000).

[3] S. Abhijit, O. Keka, S. Ashis, M. Ajay, Adv. Pet. Explor. Dev., 2, 13 (2011).

[4] D.O. Shah, R.S. Schechter, Improved Oil Recovery by Surfactant and Polymer Flooding, Academic Press Inc., Publications, New York (1997).

[5] A. M. Michels, R. S. Djojosoeparto, H. Haas, R. B. Mattern, P. B. van der Weg, W. M. Schulte, SPE Reserv. Eng., 11, 189 (1996).

[6] T. Austd, J. Milter, (1997).

Figures

Fig. 1. The effect of surfactant concentration on the phase behavior at 60 °C. The solutions consisted of 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 wt% dodecyl alkyl sulfate and VGH crude oil.

Fig. 2. Production performance of surfactant-polymer flooding after water flooding.

Nano-patterning on Graphite by cobalt oxides

Daniel Díaz Fernández1, Javier Méndez2, Angel Adolfo del Campo3, Miguel Angel Rodríguez3, Guillermo Dominguez1, Oscar Bomatí1, Alejandro Gutierrez1, Leonardo Soriano1.

1Departamento de Física Aplicada and Instituto de Ciencia de Materiales Nicolás Cabrera, Universidad

Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain

2ESISNA Group, Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, Campus de Cantoblanco 28049 Madrid, Spain

3Instituto de Cerámica y Vidrio CSIC, Campus de Cantoblanco, 28049 Madrid, Spain [email protected]

Nano-patterning of graphite by metal particles based on their catalization of the gasification reaction of carbon is a well-known phenomenon studied since the 1960s [1,2]. This has seen a rising interest in recent times because of its promising applications in graphene cutting and nanolithography [3,4,5]. It has been shown that graphite nano-patterning can be done using different gases (H2, O2) and metallic particles (Ag, Pd, Ni, Co), but all of these experiments need heating of graphite/graphene to temperatures over 500ºC in air or CVD reactors with a fairly high gas flow. In this work we report the formation of nano-channels by thermal oxidation of cobalt oxide, instead of metallic nanoparticles, at lower temperatures and oxygen pressure than in previous experiments. Due to the lack of studies of the growth of this material on graphite, we first present results on the characterization of the early, intermediate and final stages of this growth of cobalt oxide on Graphite at room temperature by XPS and AFM. Then, the results for different processes of further re-oxidation of the former cobalt oxide are presented. Finally, we have studied the nano-channels formed after the above processes by means of micro-Raman spectroscopy and AFM. The results reveal that the nanochannels consist of defective graphite. Also the formation of ripples on the non-covered graphite surface are observed.

References [1] G. R. Hennig. Journal of Inorganic Nuclear Chemistry, 24 (1962), 1129-1137 [2] R. T. K. Baker, J. A. France, L. Rouse and R. J. Waite. Journal Of Catalysis, 41 (1976), pp. 22-29 [3] L. C. Campos, V. R. Manfrinato, J. D. Sanchez-Yamagishi, J. Kong and P. Jarillo-Herrero. Nano Letters, 9 (2009), pp 2600 2604 [4] T. J. Booth, F. Pizzocchero, H. Andersen, T. W. Hansen, J. B. Wagner, J. R. Jinschek, R. E. Dunin-Borkowski, O. Hansen and P. Bøggild. Nano Letters, 11 (2011), pp 2689 2692 [5] L. Bulut and R. H. Hurt. Advanced Materials, 22 (2010), pp 337 341

Figures

Fig. 1: CoO/HOPG, AFM images (2.5x2.5 µm), coverage as labeled.

Fig. 2: (a)-(d): AFM images. (a) and (b): Nanochannels examples, CoO/HOPG, reoxidized, 400 ºC, 1 h, 2·10-3 mbar. (a): 2 ML; (b)

4 ML. (c) and (d): examples of rippled zones. (e): QMS measurements during a reoxidation process

Impact of the leads on the bound states in the continuum in double quantum dots

C. Álvarez, F. Domínguez-Adame and E. Díaz

Departamento de Física de Materiales, Universidad Complutense, E-28040 Madrid, Spain [email protected]

Abstract Bound states in the continuum (BICs) are truly localized states lying in the continuum energy spectrum of a quantum system. They were postulated by von Neumann and Wigner already in 1929 [1] and the advent of nanofabrication techniques has made it possible to devise and fabricate quantum devices to experimentally validate their existence. Capasso et al. measured the absorption spectrum at low temperature of a GaInAs quantum well with Bragg reflector barriers produced by a AlInAs/GaInAs superlattice [2]. A narrow line in the absorption spectrum was attributed to electron excitations from the ground state of the quantum well to a localized level well above the AlInAs band edge. Nevertheless, this state cannot be regarded as a true BIC but a bound state above the barrier since it is a defect mode residing in the minigap of the superlattice, as pointed out by Plotnik et al. [3]. Electronic transport in mesoscopic and nanoscopic systems can be also influenced by the occurrence of BICs [4]. González et al. have demonstrated that quantum dots based on semi-conductor materials and graphene can support BICs [5]. Furthermore, Dutta and Roy have shown that BICs may arise in heterogeneous nanostructures by engineering the spatial dependence of the effective mass of carriers [6]. Recently, González-Santander et al. extended the notion of BIC to the domain of time-dependent potentials [7]. To this end, they considered a quantum ring connected to two leads. An AC side-gate voltage controlled the interference pattern of the electrons passing through the system. The transmission probability displayed Fano antiresonances when the Fermi energy matches the driving frequency, signaling the presence of BICs. All these features stimulate the interest of BICs to develop new applications in nanoelectronics. In this work we consider two quantum dots, tunnel-coupled to left (L) and right (R) leads, as shown in Fig. 1. The energy levels of the dots, i, can be shifted by two side electrodes. In addition, electrons of

each dot interact with a local vibrational mode with frequency 0. The Hamiltonian describing the

system is (we set = 1)

0 H.c.k k k i i i i i i i ki k i

k i k

H c c a a a a d d V c d

where c k destroys an electron with wave number k and energy k in the lead (L or R), di is the

destruction operator in the ith dot and ai a local vibrational mode at the dots. Here V ki is the tunneling matrix element between the dots and the leads and is the electron-phonon coupling constant. We closely follow Ref. [8] and compute the electric current using the nonequilibrium Keldysh formalism.

Tr ( ) ( ) ( ) Tr ( )2

L R L R

L R

eI d f f A iG

h

where f is the Fermi distribution function, ( ) ( ) ( )A i G G is the spectral function and the

describes the tunneling coupling between the dots and the leads

0 0

1

1

L R

Here 0 is a constant, describes the difference in the coupling of the electrodes to different dots and stands for the asymmetry in the coupling of the QDs to the left and right leads.

In our calculations we take 0 as the unit of energy and work at T = 0. In addition, we consider 0 = 0.02, = 0.1, = 0.4 and = 1, and calculated the spectral function ( )A . Figure 2 shows the results for

asymmetric leads, namely taking L =

R, and symmetric leads. In both cases the results for 1 = 2 and 1

= 2 = -0.02 are shown. When the leads are asymmetric, the spectral function is rather insensitive to variations of the energy levels of the dots. On the contrary, the spectral function when the lead are

symmetric reveals the existence of the BICs as well defined Fano resonances, as expected in this system [7]. References

[1] J. von Neumman and E. Wigner, Z. Phys. 30 (1929) 465.

[2] F. Capasso, C. Sirtori, J. Faist, D. L. Sivco, S. Chu and A. Y. Cho, Nature 358 (1992) 6387.

[3] Y. Plotnik, O. Peleg, F. Dreisow, M. Heinrich, Matthias, S. Nolte, A. Szameit and M. Segev, Phys. Rev. Lett. 107 (2011) 183901.

[4] J. U. Nöckel, Phys. Rev. B 46 (1992) 15348.

[5] J. W. González, M. Pacheco, L. Rosales and P. A. Orellana, EPL 91 (2010) 66001.

[6] D. Dutta and P. Roy, EPL 89 (2010) 20007.

[7] C. González-Santander, P. A. Orellana and F. Domínguez-Adame, EPL 102 (2013) 17012.

[8] M. Bagheri Tagani and H. Rahimpour Soleimani, Phys. Scr. 86 (2012) 035706.

Figures

Figure 1. Schematic view of the device. Two quantum dots, labelled 1 and 2, tunnel-coupled to left (L) and right (R) leads. Two side electrodes with voltage Vg1 and Vg2 shift the energy levels of the dots.

Figure 2. Spectral function for a) asymmetric and b) symmetric leads. Parameters are given in the main text.

Spin-dependent transport through hybrid ferromagnet-graphene rings

M. Saiz, A. V.Malyshev and F. Domínguez-Adame

Departamento de Física de Materiales, Universidad Complutense, E-28040 Madrid, Spain [email protected]

Abstract Due to its large electron mobility and long coherence lengths, graphene is a material of choice to study quantum coherence phenomena, such as the Aharonov-Bohm effect. The observation of Aharonov-Bohm conductance oscillations in a graphene ring [1] suggests that quantum interference effects can be used to design novel nanodevices. In this context, Wu et al. have demonstrated theoretically that rectangular graphene nanorings pierced by a magnetic field behave like a resonant tunneling device [2]. Hung Nguyen et al. reported a numerical study on the transmission probability in rectangular rings and concluded that it can be strongly modulated and fully suppressed when tuning the magnetic field [3]. Recently, we have studied electron transport in the fully coherent regime through a quantum interference device based on a hexagonal graphene nanoring [4], in which all edges are of the same type to reduce scattering at bends [5]. We demonstrated that electron transport can be controlled by a side gate voltage applied across the nanoring. Moreover, the hexagonal ring operates as an efficient spin filter if a layer of a ferromagnetic material, such as, EuO is deposited on top of it [6]. The filtering effect results from the proximity exchange interaction between Eu2+ ions and graphene electrons [7,8]. In Ref. [6] we discussed the impact of imperfections on the spin filtering efficiency of the hexagonal ring. We also considered asymmetric rings with one arm wider than the other and found out that the polarization sign can be switched much more abruptly, making an asymmetric design more advantageous for applications. In this work we address asymmetrically connected square nanorings . The quantum transmission boundary method combined with the effective transfer matrix approach were used to calculate wave functions and spin-dependent transmission coefficients for spin up (T ) and spin down (T ) electrons (see Ref. [6] for further details). We define the degree of transmission polarization as P = (T T )/(T + T ) and it will be the figure of merit to assess the spin filtering efficiency. We compare the transmission properties of symmetric and asymmetric rings with semiconducting leads (nanoribbons with armchair borders, which have an energy gap) in the absence of proximity exchange interaction. We have numerically found that the transmission patterns can be grouped into two categories, depending on the value of the nanoribbon width w. If the number of hexagons is of the form N = 3n 2, n being an integer, the transmission coefficient presents resonant peaks whose shape is Lorentzian close to the resonance energy. A typical example is shown in Fig. 2(a) corresponding to w = 10.6 nm (N = 43), for both symmetric (dashed line) and asymmetric (solid line) rings. When N = 3n, the transmission coefficient strongly depends on the symmetry of the ring. As shown in Fig. 2(b) for w = 11.1 nm (N = 45), the transmission coefficient for symmetrically connected rings is rather smooth and increases uniformly in the one-mode energy windows (dashed line). On the contrary, if the ring is connected asymmetrically, the transmission coefficient presents Fano-like antiresonances (solid line). When the EuO layer is deposited on top of the ring, the interaction with the ferromagnet shifts the transmission curves towards upper energy for spin up electrons or towards lower energy for spin down electrons. The energy shift is of the order of 5 meV. Except for the energy shift, the transmission pattern remains qualitatively the same and is not shown here while the transmission polarization is presented in the lower panels of Fig. 2. For symmetrically connected rings, the transmission polarization P changes sign smoothly over a wide energy region. Consequently, transmission polarization remains rather insensitive to changes of the Fermi energy. On the contrary, the polarization for asymmetrically connected rings changes more abruptly, especially in the case N = 3n, and therefore it can be controlled by small changes of control parameters, which can be useful for applications. In summary, we have proposed and studied a novel spin filter which exploits quantum interference effects. The proximity induced exchange interaction between ferromagnetic ions and electrons in graphene can be exploited to obtain a spin-dependent transmission coefficient and, as a consequence, a spin-dependent conductance We found that the polarization of the transmission changes more abruptly with the Fermi energy in asymmetrically connected rings due to the occurrence of Fano-like antiresonances.

References

S. Russo, J. B. Oostinga, D. Wehenkel, H. B. Heersche, S. S. Sobhani, L. M. K. Vandersypen and A. F Morpurgo, Phys. Rev. B 77 (2008) 085413.

Z. Wu, Z. Z. Zhang, K. Chang and F. M. Peeters, Nanotech. 21 (2010) 185201.

V. Hung Nguyen, Y. M. Niquet and P. Dollfus, Phys. Rev. B 88 (2013) 035408.

J. Munárriz, F. Domínguez-Adame and A. V. Malyshev, Nanotech. 22 (2011) 365201.

H. A. Fertig and L. Brey, Phil. Trans. R. Soc. A 368 (2010) 5483.

J. Munárriz, F. Domínguez-Adame, P. A. Orellana and A. V. Malyshev, Nanotech. 22 (2012) 205202.

H. Haugen, D. Huertas-Hernando and A. Brataas, Phys. Rev. B 77 (2008) 115406.

A. G. Swartz, P. M. Odenthal, Y. Hao, R. S. Ruoff and R. K. Kawakami, ACS Nano 6 (2012) 10063.

Figures

Figure 1. Schematic view of graphene nanorings connected symmetrically or asymmetrically to two armchair nanoribbons. The ferromagnetic insulator layer is grown on top of the nanorings.

Figure 2. Upper panels show the transmission coefficients in the absence of ferromagnetic layer for two different values of the nanoribbon width (given in the plot). Lower panels show the transmission polarization when the ferromagnetic layer is grown on top on the nanoring. Solid and dashed lines correspond to asymmetric and symmetric rings, respectively..

Reprogrammable two-dimensional surface patterns using multifunctional polymers

André Espinha, María Concepción Serrano, Álvaro Blanco, Cefe López

Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Calle Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049 Madrid, Spain

[email protected]

Abstract

Multifunctional materials (MFMs) play a key role in technological applications due to their capacity to respond to different physical, chemical and/or biological stimuli. This characteristic allows them to be simultaneously implemented both as sensors and actuators, in a wide range of systems, and therefore, higher levels of performance may be attained - smaller, lighter and smarter devices can be fabricated. Within MFMs, polymers are particularly attractive as in general they are inexpensive and amenable to high throughput. Additionally, their properties can be easily tailored by introducing modifications at their synthesis. A notable feature which is being gradually incorporated in this kind of MFMs is the shape memory effect (SME) [1], for example for the development of self-healing devices. The so-called shape memory polymers (SMPs) present the ability to switch from a temporary to a permanent shape, generally in response to heat. In later years, SMP properties such as strength, elasticity or thermal-conductivity have been extensively explored [2]. Importantly, the phenomenon of SME in polymers has been also demonstrated at the micro- and nanoscale [3]. Therefore it is feasible to control the topology of the SMP surface and take advantage of its reprogrammable character.

In this work, a material system consisting of a two-dimensional pattern imprinted in the surface of a SMP is reported. It integrates several interesting features such as thermoresponsivity, elasticity, shape memory and read/write capability. As revealed by atomic force microscopy (Figure 1), the pattern was composed by a hexagonal array of nanobowls. A colloidal crystal was used as a template and the pattern was transferred to the SMP using a soft lithography-based procedure [4]. The polymer selected belonged to the family of polydiolcitrates which have been recently identified as thermoresponsive elastomers presenting SME [5]. Additionally, they are biocompatible and biodegradable and present drug delivering capabilities, all features which clearly underline their multifunctional nature. From the structural point of view, the surfaces were characterized with atomic force and scanning electron microscopies. From the optical point of view, the characterization of the first order Bragg diffraction angle was carried out.

By heating the sample above the melting transition of the SMP and applying mechanical stress, it was possible to set a new temporary surface topology which, on its turn, was fixed after cooling. Re-heating the sample allowed the recovery of the initial pattern. In this way, a proof of concept was introduced to demonstrate the direct impact of SME on the topology of the sample. It corresponded to a systematic study of the diffraction angle of the radiation impinging the structure as a function of the programmed elongation. This analysis was performed by monitoring the projected spots in a far field positioned screen. Examples for the sample at the initial state and after 15% of deformation are shown in Figure 2 (left and right images, respectively). Up to thirty five heat-stretch-cool-relax followed by heat-relax cycles were achieved.

Previous works introduced analogue systems based on SMPs as switching membranes with programmable color [6] or as time-temperature integrators [7]. The proposed system might find application in areas such as food packaging or biomedicine. Active research is being carried out for exploring the possibility of fabricating disposable, self-healing and low-cost photonic devices. References [1] A. Lendlein, S. Kelch, Angewandte Chemie, 12 (2002) 2034-2057. [2] B. Behl, M. Razzaq, A. Lendlein, Advanced Materials, 31 (2010) 3388-3410. [3] T. Altebaeumer, B. Gotsmann, H. Pozidis, Nano Letters, 12 (2008) 4398-4403. [4] Y. Xia, G. Whitesides, Angewandte Chemie International Edition, 5 (1998) 550-575. [5] M. Serrano, L. Carbajal, G. Ameer, Advanced Materials, 19 (2011) 2211-2215. [6] J. Li, J. Shim, J. Deng, J. Overvelde, K. Bertoldi, S. Yang, Soft Mater, 40 (2012) 10322-10328. [7] D. Davies, A. Vaccaro, S. Morris, N. Herzer, A. Schenning, C. Bastiaansen, 21 (2013) 2723-2727.

Figures

Figure 1. Contour plot representing the topology of the SMP surface after imprinting the pattern, as measured by atomic force microscopy.

Figure 2. Diffraction patterns projected in a far field screen for the initial state of the pattern (left) and after 15 % of deformation of the sample (right).

Ecotoxicological effects of the application to soil of sewage sludge contaminated with ZnO nanoparticles

Fernández, MD; García-Gómez, C; Alonso-Blázquez, N.; Del Rio, C; Alonso, D; Pareja, JL; Babin MM.

.

INIA. Department of Environment. Crta de La Coruña Km 7. 28040 Madrid. Spain [email protected]

Introduction Zinc oxide nanoparticles (ZnO-NPs) are widespread and are increasingly applied in various commercial products, such as personal care products or pharmaceuticals. These products go to sewage waters and during wastewater treatment, nanoparticles may be integrated into the sewage sludge matrix. Consequently, land application of these residues may be an important pathway of ZnO-NPs into soils, with consequences to terrestrial and aquatic species. Because the properties of the nanomaterial differ from those associated with bulk material, the potential toxicological effects of these products must be determined. Data concerning the potential impact of these NPs in the environment is still emerging. Specially, data on the ecotoxicity of metal oxide NPs remain scarce. Ecotoxicological assessment of sewage sludges contaminated with NPs may provide a significant complement to chemical studies and may also permit the estimation of toxicity resulting from interactions among NPs and the particular contaminants present in the sludges. The present work investigates the effects on soil and aquatic organisms of ZnO-NPs contaminated sewage sludge, using a -3) [1]. Materials and Methods Control soil, sludges and nanoparticles Soil was collected from a superficial layer of a field located near Madrid (Spain). Soil was air dried and sieved (2-mm mesh). Main physicochemical characteristics of this soil were: clay 7.8%, silt 18.8%, sand 73.4 %; pH 7.27 and organic C 1.09%. Sewage sludge samples (SS) were supplied from two municipal waste water treatment plants located in the north of Spain. Their characteristics were: SS1: pH, 7.0; electric conductivity (EC), 1669 -1; total organic matter (TOM), 28.29%; oxidizable organic matter (OOM), 20.43%; total nitrogen (TN), 3.09 %; ammonia-nitrogen (NH4

+), 0.57%; Phosphorous (P2O5), 1.02%; potassium (K2O), 1.13%; Zn, 868 mg kg-1 S cm-1; TOM, 61.72%; OOM, 7.12%; TN, 0.76%; ammonia-nitrogen NH4

+, 0.08%; P2O5, 0.59%; K2O, 0.62%; Zn, 110.99 mg kg-1 d.w. ZnO-NPs ( 100 nm) were obtained from Sigma-Aldrich (Germany) with a nominal primary particle size

Treatments Sludges were spiked with ZnO-NPs (nominal range 2500-20000 mg ZnO-NPs kg-1 sludge), thoroughly mixed to obtain homogeneity, and were then equilibrated for 7 d at 70% humidity. These sludges were mixed with the soil at a 5% w/w ratio to have 125, 250, 500, and 1000 mg Zn kg-1 soil. Ecotoxicity assays Sludge amended soils were assessed on the Multispecies Soil System MS-3 [1]. Briefly, samples were placed in 15 cm height x 15 cm diameter methacrylate columns and ten adult Eisenia fetida (Oligochaeta: Lumbricidae) were added on day 0 to each soil microcosm. Seven seeds of three plant species (i.e. wheat, Triticum aestivum; radish, Rabanus sativus and vetch, Vicia sativa) were sown on to the soil in each microcosm. Three replicates for each treatment were carried out. Columns were incubated in a climate room at controlled temperature (20 2ºC) and illumination (16:8 h; 3000-4000 lux). Columns were watered 5 days a week with 50 ml of dechlorinated water and the leachates were collected. After 21 days, MS-3 columns were opened and toxicity tests were performed to assess the effects of amended soils and their leachates to soil (earthworms, microorganisms and plants) and aquatic organisms (algae and Daphnia), respectively. Procedures were accomplished following principles of standardized methods (OECD). SPAD (soil-plant analysis development) index was measured to estimate the chlorophyll state in plants using a Minolta Chlorophyll Meter SPAD-502. Enzymatic activities on microorganisms, earthworms and plants In microorganisms dehydrogenase [2] and acidic phosphatase[3] activity were measured in soils.

In whole worms and plant leaves the following enzymatic activities were determined: Catalase (CAT) [4], Glutathione-S-transferase (GST) [5], Superoxide Dismutase (SOD) [6], Ascorbato peroxidasa (APX) [7], and Guaiacol peroxidase (POD) [8]. Total protein [9] and L-Glutathione reduced (GSH) contents [10] were also measured. Results The toxicity of ZnO-NPs to soil and aquatic organisms was influenced by the sludge´s chemical characteristics. In general, the toxicity of soil amended with SS1 spiked with ZnO-NPs was higher than the observed in soil amended with SS2 spiked with same concentration of NPs. SS1-soil caused a 43 4% of mortality on earthworms exposed to the highest dose (1000 mg kg-1 soil d.w.) whereas effects on weight were not detected. Regarding biochemical parameters, the only significant effect was a enhancement of GSH content from 1.9 0.1 in untreated SS1-soil to 2.3 0.1 µmol g-1 worm in SS1-soil spiked with 1000 mg Zn kg-1 soil. By contrast, in SS2-soil no effects were observed in any lethal or sublethal parameters at all doses tested. ZnO-NPs did not affect seedling emergence. However, samples exposed to treated SS1-soil exhibited a inhibition of growth. Radish was the most sensible species showing a dose dependent decrease of wet weight with inhibitions of 47 10 and 54 12% at 500 and 1000 mg Zn kg-1 soil, respectively. SS2-soil did not produce adverse effects in seedling germination or plant growth in any of the three plant species. Effects on chlorophyll content measured as SPAD index were observed only for wheat exposed to ZnO-NPs in both sludges. Effects on enzymatic activities, and GSH and protein content varied between plant species and sludges (See figure). For microorganism inhibition of carbon mineralization (34 3%) and dehydrogenase activity (56 6%) of ZnO-NPs were observed only for SS1-soils, at 1000 mg Zn kg-1 soil. However, both sludges inhibited acidic phosphatase activity in a dose dependent manner with an EC50=984(702-2244) for SS1-soil and EC20=817(631-1135) mg Zn kg-1 soil d.w. for SS2-soil. For aquatic organisms, leachates from both sludges-soil mixes did not produce effect on algae growth. However, inhibition of daphnia mortality was observed for ZnO-NPs spiked SS1-soil with EC50=477(416-559) mg Zn kg-1 soil d.w. In summary, the addition to soil of sewage sludges contaminated with ZnO-NPs can cause effects in soil and aquatic organisms which depend on the physicochemical characteristics of the sludges. These findings are important with respect to the consideration of the environmental risk of routine additions of sewage sludge amendments to soil. However, the levels of ZnO-NPs causing toxicity were very elevated compared to expected sludge concentrations of NPs and consequently, immediate effects of sewage sludges for ecosystems should not be expected. Acknowledgments This research was funded by the RTA2010-00018-00-00 and EIADES S-2009/AMB/1478 projects. References [1] Fernández, M.D. Cagigal, E. Vega, M.M. Urzelai, A. et al. Environ. Ecotox. Saf. 62 (2005) 174-184. [2] Carbonell G, Pablos MV, Garcia P, Ramos C, Sanchez P, et al.Sci Total Environ 247 (2000) 143-50. [3] Freeman C, Liska G, Ostle NJ, Jones SE, Lock MA. Plant Soil 175 (1995) 147-52. [4] Aebi H. In Methods in enzymology. Vol 105. Ed. Academic Press, Inc. New York 1984. [5] Habig W., Pabst M., Jakoby W. The Journal of Biological Chemistry vol. 249, 22 (1974) 7130-9. [6] Peskin AV, Winterbourn CC. Clinica Chimica Acta 293 (2000) 157-66. [7] Gupta, AM., Ahmad M. Toxicol Environ Chem, 93 (2011) 1166-1179. [8] El-Shabrawi, H, Kumar B, Kaul, T, Reddy, MK, et al. Protoplasma, 245 (2010) 85 96. [9] Bradford MM. Analytical Biochemistry 72 (1976) 248-54. [10] Hissin PJ, Hilf RA Anal Biochem 74 (1976) 214 226. Figures

Effects on plants of sewage sludges contaminated with ZnO-NPs (only parameters significantly differences from control at p<0.05 by the LSD procedure are shown).

Nanoparticle formation and emission mechanisms during laser melting and ablation of industrial ceramic tiles

A. S. Fonseca

1,*, M. Viana1, I. de Francisco2, G.F. de la Fuente2, C. Estepa2, X. Querol1

1 Institute of Environmental Assessment and Water Research (IDAEA-CSIC), C/ Jordi Girona 18, 08034 Barcelona, Spain 2 Instituto de Ciencia de Materiales de Aragón (ICMA - Universidad de Zaragoza), María de Luna 3, E-50018 Zaragoza, Spain

*Corresponding author: [email protected]

Abstract

During the last few years, there has been increasing evidence that workers in tile and ceramic industry

are exposed to a considerable amounts of harmful airborne particles especially from the manufacturing

of ceramics in furnaces [1-3].

In order to assess exposure to nanoparticle (NPs) emissions and their involved risks, particles emitted

during the tile sintering using laser irradiation in a high-temperature furnace (continuous laser furnace)

and during laser ablation were characterized. Six typical industrial tiles were selected, corresponding to

commercial raw porcelain tile (#1), porcelain tile with frit (#2), porcelain tile with frit and colored

decoration (#3), raw red clay tile (#4), red clay tile with frit (#5) and red clay tile with frit and colored

decoration (#6). Seven experiments using two different laser technologies were made: (i) laser

treatment of each ceramic material (from #1 to #6) and (ii) laser ablation of #1 (corresponding to

experiment #7). Quantitative NP levels were studied by monitoring real-time size-resolved aerosol

concentrations in the size range of 5 nm to 2 at the emission source (ES) and the breathing zone

(BZ). Offline techniques such as transmission electron microscopy (TEM) and Energy-Dispersive X-ray

(EDX) spectroscopy were used to characterize the particles collected and determine their corresponding

elemental composition.

Figure 1 shows the time series of the particle number concentrations and size of the particles emitted

during each experiment both at the emission source and in the breathing zone. Figure 2 shows

micrographs from the particles sampled at the emission. The results evidenced that:

The red clay tiles emitted higher particle number and mass concentrations in comparison with porcelain tiles during the laser melting process;

Emissions in terms of particle number concentration from tiles with frit (especially red clay; #5) were higher than from raw tiles or with decoration;

Two different emission behaviors were detected, between porcelain and red clay tiles, strongly linked to T and composition;

New particle formation processes (nucleation) were detected during thermal sintering of the tiles;

Nanoparticle emission processes were detected during laser melting of the tiles;

Spherical particles originated from fusion were observed by TEM images;

NP emissions in terms of mass were highest during ablation process;

The highest concentrations of potentially harmful metals were found in the ultrafine fraction < 0.25 µm.

It is recommended that pre-cautionary and protective actions should be undertaken based on the high

NP concentrations recorded.

References

1. Bache, C.A., et al., Epidemiologic study of cadmium and lead in the hair of ceramists and dental

personnel. J Toxicol Environ Health, 1991. 34(4): p. 423-31. 2. Hirtle, B., et al., Kiln emissions and potters' exposures. Am Ind Hyg Assoc J, 1998. 59(10): p. 706-

14. 3. Taylor, J.R., A.C. Bull, and I.o. Ceramics, Ceramics Glaze Technology1986: Institute of Ceramics

by Pergamon Press.

Figures

Figure 1. Particle size diameter and particle number concentrations measured during each experiment in ES and BZ. The two different series in each plot represent number concentration of particles (solid lines) and corresponding particle size diameter (dashed lines).

Figure 2. TEM images of particles collected in ES during: (a) and (b) porcelain and red clay tile with frit manufacturing using laser melting technique in a high-temperature furnace (#2 and #5 respectively) and (c) raw porcelain tile manufacturing using laser ablation (#7).

Optimization of a nanoparticle nebulization system to fight insect pests

J. Querol-Donata, M.A. Ochoa-Zapater

a, F.M. Romero

b, A. Ribera

b, A. Torreblanca

a, G.

Gallelloc, M.D. Garcerá

a,*

aDepartamento de Biología Funcional y Antropología Física, Universitat de València, Dr.

Moliner 50, 46100 Burjassot, Valencia, Spain.bInstituto de Ciencia Molecular, Universitat de València, Catedrático José

Beltrán, 2. 46980, Paterna, Valencia, Spain.c

Departamento de Química Analítica, Universitat de València, Dr. Moliner 50, 46100 Burjassot, Valencia, Spain.*[email protected]

Abstract

Introduction

Nanotechnology is a new field of research with great potential that can contribute with great

benefits in electronics, optics, medicine, and agriculture. One of the most interesting agricultural

uses would be in the fight against pests. Nanoparticles (NPs) can serve as a vehicle for

insecticides, reducing both the amount of active compound required and waste generated in the

environment. The NPs could facilitate a more direct penetration into the individuals and their

target organs, and limit or delay the emergence of resistance to these compounds. One of the

main entry routes of the current insecticides is the airway. The aim of this study is to observe if

there is penetration of NPs by nebulization, in order to study the possibilities of employing NPs

functionalized with insecticides. Our aim is to develop a methodology to nebulize NPs to treat

insects.

Methodology

Gold nanoparticles (AuNPs, average size of 21,8 nm) were synthetized as described by Bastús

et al. [1] and were characterized by UV-Vis and Transmission Electron Microscopy (TEM). The

nebulization system used is the "Mass Dosing System" from Buxco®

Electronics, Incorporated,

Wilmington, NC, USA, a system originally designed for small mammals. Adult Blattella

germanica individuals (15 males and 15 females, aged 1-6 days) were exposed to nebulized

AuNPs and kept inside the nebulization chamber for periods of time ranged between 15 and 90

minutes. Blattella can keep closed its spiracles and its tracheal system for 20-30 minutes so a

minimum time of exposure is required to secure that cockroaches inhale the nebulized AuNPs

[2]. Volumes of 1 and 2 mL of AuNPs in sodium citrate (2,2�10-4

± 7�10-6

g Au/L), with variable

percentages of duty (percentage of nebulized solution per cycle, one cycle is 6 seconds)

between 5% and 100% were studied. Half of individuals were frozen for the measurement of

the amount of gold penetration at time 0 while the other half was monitored to control mortality

rates for 96 hours and frozen as well at the end of the bioassay. ICP-OES technique

(Inductively Coupled Plasma Optical Emission Spectroscopy) was used to measure gold intake

in treated cockroaches.

Results

With this nebulization system we could study the differences in nebulization times depending on

duty percentages and volumes used. Also, we could observe that AuNPs nebulization times

were longer than control nebulization times (figure 1). Although mortality rates were not

significant, treated individuals showed hyperactivity and an increase of voracity [4]. The ICP-

OEs technique results showed that for any time and percentage of duty tested, gold was

detected in all treated insects at time 0, indicating that this system is suitable for the

administration of nanoparticles to the insects’ tracheal system [3]. However, gold was not

detected after 96h after treatment. A higher amount of accumulated gold was observed when

the nebulized volume of AuNPs solution was increased (Fig. 2).

Acknowledgements: this work has been supported by grant AGL2010-21555 from the

Ministerio de Economía y Competitividad.

References

[1] N.G. Bastús, J. Comenge, V. Puntes, Langmuir, 27 (2001) 11098-11105.

[2] G.K. Snyder, B. Sheafor, D. Scholnick, C Farrelly, J. theor Biol., 172 (1995) 199-207.

[3] R. Posgai, M.G. NielseN, S.M. Hussain, J.J. Rowe, M. Ahamed, Science Toxicology

Environmental 408 (2009) 439-443.

[4] Z. Yann, A. Rocha, C.J. Sanchez, H. Liang, Nanoparticles in Biology Medicine 906 (2012)

423-433.

Figures

Figure 1: Total nebulization time depending on the treatment

(control or nanoparticle) and the percentage of duty.

Figure 2: Quantity of gold in µg Au/gr insect compared to

nebulized volume (mL) and duty (%).

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Tailoring the size and shape of a new type of Silver Nanostars with outstanding plasmonic properties

Adianez Garcia-Leis, Irene Rivera, Jose V. Garcia-Ramos, Santiago Sanchez-Cortes

Instituto de Estructura de la Materia, IEM-CSIC. Serrano 121, 28006 Madrid, Spain

[email protected]

Abstract Branched metal nanoparticles (NPs) such as nanostars and nanoflowers are exciting plasmonic and catalytic platforms on account of their often large surface areas, multiple high angle edges, and sharp tips [1]. The small radius of curvature of sharp tips can concentrate electromagnetic fields at these features of Au and Ag nanostructures to achieve high sensitivity in plasmon-enhanced surface spectroscopy [2]. Also, through size controlled syntheses of branched metal nanoparticles, the extinction features of their localized surface plasmon resonance (LSPR) can be tuned. The fabrication of silver nanostars (AgNS) should be of high interest in spectroscopy and, therefore, in the optical detection field, due to the better optical properties of this metal in comparison to gold, taking into account the LSPR properties of each metal. In addition, AgNPs displays higher SERS enhancement factors (EF) in comparison to gold ones [3]. In this work, a reduction in two steps method, using hydroxylamine and citrate to obtain AgNS is reported. This method can be modulated to give rise to NPs of different morphological features, the diameter, as well as the length and the tip width of arms. The Principal Component Analysis (PCA) was used to identify the morphological features in 24 samples and to correlate them to the different experimental conditions employed in their fabrication.

Figure 1: PCA graphic of scores and loadings of data obtained from morphological features of 24 AgNS samples. Loadings: d-diameter, a-arm length and b-tip width. Scores: 24 samples of AgNS obtained by different experimental conditions.

The oxidation-reduction method described in reference [3] was used to fabricate 24 samples, but changing the values of the experimental conditions. A colloidal suspension of AgNS was prepared by chemical reduction of Ag+ in two steps using as reduction agent a neutral hydroxylamine solution (HA) in a first step and a citrate solution (CIT) in the second one. The combination of these two reduction agents affords the necessary conditions to induce the growth of the spiked and the stabilization of nanoparticles. The resulting NPs were characterized by Transmission Electron Microscopy (TEM) and extinction spectra. Finally, the morphological features derived from the TEM analysis were used to carry out the corresponding PCA study. TEM images corresponding to 24 AgNS samples were analyzed by PCA with the ImageJ software to obtain the diameter (d), arm length (a) and tip width (b) data of nanostars. As can be seen, Figure 1 shows that the data can be classified in seven groups formed by samples with similar features depending of: size (bigger or smaller), type of arm (longer or shorter) and type of tip (spiky or rounded). As can be seen from Figure 1, d and a are the most influencing parameters on the NPs morphology, because they are placed far away from the center. This indicate a significant separation of NPs into larger ones (on the right side, sample 705), and the smaller ones (left side, samples 160, 260, 360, 460, 560 and 660). The extinction and surface-enhanced Raman scattering (SERS) spectra were measured from all these samples and the enhanced factors were calculated from the SERS spectra using thiophenol as probe molecule. References [1] DeSantis C.J., Skrabalak S., J. Am. Chem. Soc., 135 (2013) 10. [2] Rodrí - nchez-Gil J. A., Opt. Express, 20 (2012) 621. [3] Garcia-Leis A., Sanchez-Cortes S., Garcia-Ramos J.V., J. Phys. Chem. C 117 (2013) 7791. Acknowledgment This work has been supported by the Spanish Ministerio de Economía y Competitividad (MINECO, Grant FIS2010-15405). A.G.-L. acknowledges CSIC and FSE for a JAE-CSIC predoctoral grant.

Carbon Nanotube/ -Cross Sheet Peptide Biohybrids: Dispersive Properties, Assembly, and Potential Applications

Rosa Garriga

1, Anju Sreelatha2, Ray H. Baughman3,4, Edgar Muñoz5, Warren J. Goux3

1 Departamento de Química Física, Universidad de Zaragoza, 50009 Zaragoza, Spain 2 Department of Molecular Biology, UT Southwestern Medical Center, Texas, USA

3 Department of Chemistry, The University of Texas at Dallas, USA 4 The Alan G. MacDiarmid NanoTech Institute, The University of Texas at Dallas, USA

5 Instituto de Carboquímica ICB-CSIC, Miguel Luesma Castán 4, 50018 Zaragoza, Spain [email protected]

Abstract The ability of selected peptides to efficiently disperse carbon nanotubes in aqueous media [1] may eventually facilitate carbon nanotube processing and their incorporation in biological systems, as well as their use as components for a variety of technological bioapplications[2]. Moreover, peptide self-assembly eventually enable the incorporation of carbon nanotubes into supramolecular architectures and hierarchical superstructures, therefore opening fascinating routes for directed carbon nanotube manipulation [3]. We here report on the abilities of a family of tau-protein-related amphiphilic peptides (N-acetyl-VQIVXK-NH2 (X = F, L, V, W, Y, A, K)) to disperse SWCNTs.[4] Circular dichroism (CD) spectra of one of the peptides having a high propensity to form an amyloid (N-acetyl-VQIVYK-NH2 (AcPHF6)) showed that

-sheet conformation when sonicated with SWCNTs. To date, our hexapeptides based on the AcVQIVXK framework are structurally the simplest peptides that have been found to disperse CNTs. Additionally, we have shown that the amyloidogenic propensity and hydrophobicity weigh nearly equally in determining their efficiency to disperse CNTs, and these findings may be used to design even more efficient peptides for these purposes. Further processing of stable peptide/SWCNT dispersions led to the formation of singular, unique supramolecular network architectures. An understanding of the interactions which determine the ability

-sheet peptides to disperse SWCNTs may open new opportunities for use of these biohybrids as scaffolds, the development of new functional materials (such as supercapacitors and artificial muscles), or their incorporation into carbon nanotube-based devices [4]. References [1] G. R. Dieckmann, A. B. Dalton, P. A. Johnson, J. Razal, J. Chen, G. M. Giordano, E. Muñoz, I.

H. Musselman, R. H. Baughman, R. K. Draper, J. Am. Chem. Soc., 125 (2003) 1770. [2] M. in het Panhuis, S. Gowrisanker, D.J. Vanesko, C.A. Mire, H. Jin, H. Xie, R.H. Baughman,

I.H. Musselman, B.E. Gnade, G.R. Dieckmann, R.K. Draper, Small, 1 (2005) 820. [3] A.B. Dalton, A. Ortiz-Acevedo, V. Zorbas, E. Brunner, W.M. Sampson, S. Collins, J.M. Razal,

R.H. Baughman, R.K. Draper, I.H. Musselman, M. Jose-Yacaman, G.R. Dieckmann, Adv. Funct. Mater., 14 (2004) 1147.

[4] E. Muñoz, A. Sreelatha, R. Garriga, R.H. Baughman, W.J. Goux, J. Phys. Chem. B, 117 (2013) 7593.

FINE TUNING OF SIZE AND POLYDISPERSITY OF HOLLOW CARBON SPHERES

Luz Carime Gil-Herrera,a Beatriz H. Juárez,b,c Cefe Lópeza

aInstituto de Ciencia de Materiales de Madrid, Consejo Superior de InvestigacionesCientíficas (CSIC), C/Sor Juana Inés de la Cruz 3, 28049 Madrid (Spain).

bIMDEA Nanociencia, Faraday 9, Campus de Cantoblanco, 28049 Madrid (Spain). cDepartamento de Química-Física Aplicada, Universidad Autónoma de Madrid, Cantoblanco, 28049

Madrid (Spain). [email protected]

Due to their morphology, low density and high surface area hollow carbon spheres have attracted much attention in several fields for applications in catalysts, energy storage-media, or drug delivery. Furthermore, their use as building blocks to produce high ordered structures is also an appealing feature in photonics. [1, 2] In this work the optimized conditions for the preparation of hollow carbon spheres have been studied by means of a 2-step method. This method involves the use of polystyrene beads as seeds and glucose as precursor in a hydrothermal treatment [3] followed by further carbonization at high temperatures. [4] The concentration of polystirene beads, size, polystyrene/glucose ratio, hydrotermal and carbonization temperatures as well as reaction time allow for a fine tuning of the size (100-1000 nm) and monodispersity (<4%) of the final carbon shell structures. Figure 1a show a SEM image of carbon spheres produced with initial 260 nm polystyrene beads as seeds where broken spheres evidence the empty cores (Figure 1b).

References

[1] T. Zhang, Q. Zhang, J. Ge, J. Goebl, M. Sun, Y. Yan, Y. Liu, C. Chang, J. Guo, and Y. Yin, J. Phys. Chem. C., 113 (2009) 3168.

[2] M. Goodman, K. Arpin, A. Mihi, N. Tatsuda, K. Yano, and P. Braun, Adv. Optical Mater., 1 (2013) 300.

[3] R. White, K. Tauer, M. Antonietti, and M. Titirici, J. Am. Chem. Soc.,132 (2010) 17360. [4] Q. Wang, H. Li, L. Chen, X. Huang, Carbon, 39 (2001) 2211.

Figure 1a) Hollow carbon spheres obtained from polystyrene beads as seeds. b) Broken spheres evidencing empty cores.

Influence of metal properties on the effectiveness of zero valent iron nanoparticles for soil remediation

Gil-Díaz M., Alonso J., Guerrero A.M., Lobo M.C.

IMIDRA, -2, km 38,2 28800 Alcalá de Henares (Madrid). Spain. [email protected]

Abstract The advances in nanotechnology have induced an increase in the use of nanomaterials in every sector of society, ranging from enhanced drug delivery to new methods for the treatment of polluted soil and groundwater (nanoremediation). In recent years, the environmental application of nanoscale zero-valent iron (nZVI) has generated a great deal of attention due to its potential for cost reduction compared to other in situ treatments, higher reactivity and broader applications. Several recent studies provided valuable insights into key nZVI properties associated with the potential to transform chlorinated organic compounds, metal ions such as Cd, Ni, Zn, As, Cr, Ag, and Pb, as well as notorious inorganic anions like perchlorate and nitrate [1]. Although most studies have focused on using nZVI to remove metals and metalloids from water and groundwater, metal immobilization in soils using nZVI has recently attracted attention [2-3]. In the present work, the effectiveness of nZVI for reducing the availability of heavy metals (Cr, Pb and Zn) in soils was evaluated. The influence of the nZVI dose and the chemical characteristics of the metal was also determined. The soil used in the present study was collected from the surface layer (0 30 cm depth), from an agricultural field at the East of Madrid Community. It was a loam soil, with acidic pH (5.3) and a low concentration of organic matter (0.61%) and nitrogen (0.03%). Samples of this soil were artificially polluted with K2Cr2O7, Pb(NO3)2 and ZnSO4, separately, around 200 mg/kg. The spiked soils were treated with different doses (1%, 5% and 10%) of commercial stabilized water dispersion of nZVI (NANOFER 25S, NANO IRON Rajhrad, Czech Republic). The mixtures were shaken for 72 hours. Control tests without nZVI were carried out in parallel. Three independent vials were used per treatment. Then, the relative metal availability in the soil was evaluated according the sequential extraction procedure developed by Tessier et al. [4]. Extractions with solutions of increasing strengths are sequentially added to the soil sample, and five fractions are obtained defined as exchangeable (EX), carbonate-bound (CB), Fe/Mn oxides-bound (OX), organic matter-bound (OM), and residual (RS) (in decreasing order of availability). Figure 1 shows the sequential chemical distribution of Cr (A), Pb (B) and Zn (C) in the soil at the different nZVI doses. In general, the application of nZVI induced a significant decrease of metal concentration in the most available fraction (EX and CB), and an increase of the least available forms. Differences in the metals distribution in the soil fractions were observed, in function of the metal. In the case of Cr, the EX fraction decreased by 55% after the addition of commercial nZVI at 1%, and nearly 100% at the doses of 5% and 10%; accordingly, the OX fraction increased significantly but no differences were detected for OM and RS fractions between treated and untreated soil samples. The removal mechanism probably is reduction, Cr(VI) is reduced to Cr(III) and immobilized on the iron nanoparticle surface, into the iron oxyhydroxide shell [5]. In the case of Pb and Zn, the treatment with nZVI decreased the metal in the most available fractions (EX and CB) and increased their concentrations in RS and OX fractions; higher dose of nanoparticles showed better immobilization results. The treatment was more effective for Pb than for Zn, and this can be due to the different chemicals properties of these metals; the removal mechanism for Pb, slightly more positive than Fe, is sorption and reduction, while for Zn which has a standard potential more negative than Fe, the main mechanism is sorption or surface complex formation [2]. Thus, the use of nZVI to remediate soils polluted with Cr, Pb or Zn in soils is a promising in situ strategy; the proper nanoparticle dose and the effectiveness of the immobilization depend on the metal properties. References [1] Li X, Elliott DW, Zhang W. Critical Reviews in Solid State and Materials Sciences 31 (2006) 11. [2] Gil-Díaz M, Pérez-Sanz A, Vicente MA, Lobo MC. CLEAN Soil, Air, Water (2014) DOI: 10.1002/clen.201300730. [3] Singh R, Misra V, Singh RP. Bulletin of Environmental Contamination and Toxicology 88 (2012) 210. [4] Tessier A, Campbell PGC, Bisson M. Analytical Chemistry 51 (1979) 844. [5] Li X, Cao J, Zhang W. Industrial & Engineering Chemistry Research 47 (2008) 2131.

Figure 1. Sequential chemical distribution of Cr (A), Pb (B) and Zn (C) in the soil untreated and treated with nVZI (exchangeable, EX; carbonate-bound, CB; Fe/Mn oxides-bound, OX; organic matter-bound, OM; residual, RS).

Acknowledgements. This work has been supported by Project CTM 2010-20617-C02-02 and EIADES PROGRAM S2009/AMB-1478 (www.eiades.org).

A

B

C

Fuel dyes detection by SERS

Manuel Gómez, Massimo Lazzari

CIQUS, Center for Research in Biological Chemistry and Molecular Materials

Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain [email protected]

Abstract Markers and tracers added to hydrocarbons are fluorescent dyes incorporated to fuels for differentiation, leak detection purposes and probably more important to tax them with different fees according to their use. These dyes should be easy to detect at naked eye and also by spectroscopic techniques, usually UV-spectroscopy, but also Raman spectroscopy is a useful technique and especially when the signal is enhanced by plasmonic effects related to structured surfaces (SERS). The difference on taxes that exist between automotive gasoil and heating gasoil for instance is so big, that fraud can happen, usually by laundering the original dye of a cheap fuel and changing it by a dye of an expensive one. So to avoid it a reliable control protocol able to detect low concentrations of dyes would be useful. Here we propose to use a new kind of structured SERS substrates made of fuel-insoluble polymers (perfluoropolyether derivates and ormocers) [1] and metal (usual SERS metals like Au, Ag and also Al) [2]. Preliminary results using this kind of SERS substrates will be shown. References [1] M. Gómez and M. Lazzari, Microelectronic Engineering,97, (2012), 208-211 [2] M. W. Knight, N. S. King, L. Liu, H. O. Everitt, P. Nordlander, and N. J. Halas Aluminum for Plasmonics, ACS Nano, Just Accepted Manuscript Figures

Fig 1: Automotive gas-oil SERS spectra with three different SERS substrates.

Subwavelength diffraction for quality control in nano fabrication processing

Jordi Gomis-Bresco, Claudia Simao, Martin Kreuzer, Clivia Sotomayor-Torres

Catalan Institute of Nanoscience and Nanotechnology (ICN2), Bellaterra, Barcelona, Spain.

[email protected]

Optical means cannot image the critical dimensions that nanofabrication accesses. Nevertheless, optical techniques can control nanometer scale dimensions, like scatterometry controls thin films thickness, by monitoring the changes of a particular optical property. The link between the nanometer scale critical dimension and the optical property can be done by tracing back the optical property change or by comparing with a previously acquired/calculated library. In the last years, we have developed a methodology for controlling the fidelity of nanoimprinting lithography: subwavelength diffraction (SWD)1.the shape of the motive (the cell that repeats) one can select the light intensity distribution. In particular, to maximize the light filtered out by a monocromator, blazed grating are designed to distribute most of the light in the +1 diffraction order, reducing the losses (light diffracted in the other diffraction orders). The critical dimensions of that repeated cell lay already in the nanometer scale, and if repeated with fidelity in all of the periods determine the intensity distribution of the light diffracted by the grating. In the same way that scatterometry and ellipsometry relay on libraries to detect critical dimension changes, we can establish a univocal relation between the diffraction pattern of a grating (the intensity versus collected angle measurement) and the nanometer scale critical dimensions of the repeated cell. Using this concept, in periodic structures (diffraction gratings) dimensional sub-wavelength features can be detected from the diffraction pattern (or diffractogram), given that enough orders of diffraction are measured and that the accuracy of the measurement allows distinguishing deviations from a reference. Most of the mass production nanofabrication processes, like nanoimprinting lithography, consist in reproducing a cell with nanometer scale features at least hundreds of times in a repetitive continuous way. The results of such approaches are periodic arrays of cells with well defined nanometer scale critical dimensions. The periodicities are normally in the micrometer range, and because of that, the periodic arrays constitute themselves good diffraction gratings for optical light. Once we defined the magnitude to measure (diffractogram) we focused in making the metrology compatible with the fabrication process. Diffractograms are normally collected by repositioning the wave source and the detector (what determines the diffraction angle) in a sequential way. Standard X ray machines are a good example. Sequential acquisition is slow by nature and does not allow monitoring more than one order of diffraction at a time. We have developed a diffractometer that allows implementing inline SWD as a metrology tool for inline nano fabrication. The optical design (patent pending) allows measuring at once (ms acquisition times) the diffraction pattern of an optical diffraction grating without movable parts and with high accuracy. The illuminated zone can be made as small as few 10ths of microns, improving the contrast for local defectivity, or arbitrarily big. References: 1 a)Kehoe, T., Reboud, V., Kehagias, N., & Torres, C. S. (2011). Characterization of Nanoimprinted Line Profile

using Subwavelength Optical Diffraction. Proceedings of the 11th euspen International Conference. b) Kehoe, T.,

Reboud, V., & Torres, C. S. (2009). Inline metrology configuration for sub-wavelength diffraction using

microscope optics. Microelectronic Engineering, 86(4-6), 1036 1039.

Ab Initio Simulation Study of Interfaces in Nanostructured Tungsten

Carlo L. Guerrero C.1, C. González2, R. Iglesias2, N. Gordillo1, A. Rivera1, R. Gonzalez-

Arrabal1 and J.M. Perlado1

1Universidad Politécnica de Madrid, Instituto de Fusión Nuclear, Jose Abascal 2, Madrid, Spain 2Universidad de Oviedo, Facultad de Ciencias, c/ Calvo Sotelo s/n Oviedo, Spain

[email protected]

Abstract

In both, inertial and magnetic confinement fusion, reactors, the walls have to withstand high thermal loads and radiation fluxes. This work reports on a first principles study of the light atoms behavior (H , H-isotopes and He) in nanostructured tungsten. In order to carry out this work we present the approximation of the necessary foundations for the analysis using the SIESTA code [1]. The results are compared to data [2-3] obtained with a more precise plane wave code as VASP [4]. Moreover, the work is aimed to interpret experimental results on structural and mechanical properties measured by the Materials group at the Institute of Nuclear Fusion. The obtained results are valuable for subsequent simulations on a larger scale, such as kinetic Monte Carlo [3] or Molecular Dynamics. This complete analysis allows having a nanoscopic view of phenomena leading to bubble formation and eventual trapping of light atoms at vacancies and in the bulk of tungsten, as well as at the interfaces.

References

[1] Soler J. Artacho E. Gale J. Garcia A. Junquera J. Ordejon P. and Sanchez-Portal D., J. Phys. Condens. Matter, 14 (2002) 2745. [2] Becquart C. and Domain C., Nucl. Instrum. Meth. Phys. Res. B 255 (2007) 23-26. [3] Gonzalo Valles, Antonio Rivera, Cesar González et al (for publishing) [4] Kresse G and Hafner J. Phys. Rev. B 47 (1993) R558 ; Kresse G, Furthmuller J. J, Phys. Rev. B 54 (1996) 11169; Kresse G, Joubert D. Phys. Rev. B 59 (1999) 1758.

Graphene growth on Pt(111) and Au(111) using a MBE solid carbon source

Irene Hernández-Rodríguez

1, J. M. García2, R. Aceituno1, J A Martín-Gago1, 3, P. L. de Andrés1 and Javier Méndez1,*

1Instituto de Ciencia de Materiales de Madrid (CSIC), 28049, Madrid, Spain

2MBE Lab, Instituto de Microelectronica de Madrid (CSIC), 28760 Madrid, Spain 3Centro de Astrobiología (CSIC-INTA), 28850 Torrejón de Ardoz Madrid, Spain

* [email protected]

Graphene is considered a prototype material with interesting technological applications and properties [1]. Preparation methods greatly varies from exfoliation mechanical transfer [2] (widely used in research laboratories), to Chemical Vapor Deposition (CVD) [3] (more appropriate for industrial applications). When this later method is used, the catalytic properties of the metallic substrate play a fundamental role during decomposition (cracking of C-H bonds) of hydrocarbons.

In this work, we present a Molecular Beam Epitaxy (MBE) method to obtain graphene [4] on

Pt(111). This procedure uses evaporation of carbon atoms from a carbon solid-source in ultra-high vacuum conditions. We have tested the formation of graphene on several surfaces: from a well establish substrate as platinum, to substrates where graphene can be formed using innovative methods as gold [5]. For the characterization of the graphene layers we have used several in situ surface science techniques as low energy electron diffraction (LEED), auger electron spectroscopy (AES) and scanning tunneling microscopy (STM).

The successful evaporation of carbon has been probed on different substrates as platinum, HOPG, and gold. By annealing a Pt(111) and Au(111) surfaces up to 600ºC and 450ºC respectively during carbon evaporation, we have observed a characteristic LEED diagram attributed to graphene [6]. STM images (see figure) display long range ordering of carbon monolayers showing several moirés patterns characteristic of graphene on Pt(111) [7] and islands of dendrites of Au(111) [8], further proving the formation of graphene. This method opens up new possibilities for the formation of graphene on many different substrates with potential technological applications. [1] Castro Neto, A.H. et al., Rev. Mod. Phys., 81 (2009) 109. [2] Geim, A.K. and Novoselov, K.S. Nature Mater., 6 (2007) 183. [3] Kim, K.S, et al., Nature, 457 (2009) 706-710. [4] Garcia, J.M. et al., Solid State Commun. 152 (2012) 975-978. [5] Martinez-Galera, A.J. et al., Nano Lett., 11 (2011) 3576. [6] Sutter, P. et al., Phys. Rev. B, 80 (2009) 245411. [7] Merino, P. et al., ACS Nano, 5 (2011) 5627. [8] Nie, Shu et al., Phys. Rev. B, 85 (2012) 205406

STM image of graphene on Pt(111) showing long range moirés patterns and atomic resolution (Bias Voltage = -35.7mV, Current set-point = 0.04nA).

70nm

STM image of graphene on Au(111) showing long dendritic islands at both sides of the steps. For this tip-state, graphene appears as a depression area (Bias Voltage = -12141.7mV, Current set-point = 4 A).

Detection of gases using an array of Love-wave sensors prepared through a combination of nanoparticles of oxides and different

metals

M.C. Horrillo1, D. Matatagui

1, M.J. Fernández

1, J. Fontecha

1, I. Sayago

1, J.P. Santos

1, I. Gràcia

2,

C. Cané2

1 GRIDSEN, Instituto de Seguridad de la Información, CSIC, Serrano 144, 28006 Madrid, Spain

2 Instituto de Microelectrónica de Barcelona, CSIC, Campus UAB, 08193 Bellaterra, Spain

[email protected]

Abstract A novel array comprised of eight Love-wave sensors based on ZnO and TiO2 nanoparticles with different metals as active centers has been developed to detect, classify, and discriminate gases. These films work as guide and sensitive layer of every Love-wave sensor. The interaction with gases changes the electrical properties and the density of the different layers of nanoparticles, and consequently each sensor suffers a different frequency shift. So far, the array has been tested with different concentrations of toluene and ammonia. Very low concentrations of these gases have been detected and discriminated by principal component analysis.

Introduction The efficiency of the devices based on surface acoustic waves (SAW) as gravimetric sensors for gases has been proved in the last decades. In literature, many reports proposed the use of polymers as sensitive layers [1]. However, recent reports showed that the oxide thin films used as sensitive layers of SAW devices have advantages such as their long term reliability and stability [2]. A novel idea is to use layers of nanoparticles of oxides due to their high surface area, and to dope them with different metals as active centers to change the selectivity to the gases. In this way, devices sensitive to mass-loading and electrical changes are obtained. These array of sensors combined with pattern recognition techniques are able to discriminate and classify different gases.

Materials and Methods The Love-wave sensors developed in this work are based on a shear horizontal surface acoustic wave (SH-SAW) propagated onto ST-cut quartz. This wave, with a wavelength of =28 m, is generated and detected by interdigital transducers (IDTs). To obtain a Love-wave sensor, a film of metal oxide nanoparticles has been deposited by spinning, thereby obtaining a composite film of nanoparticles capable of guiding the SH-SAW and also performs the functions of sensing layer. In order to obtain different responses of each sensor, two different layers of nanoparticles have been used (ZnO and TiO2), and three different metals (Co, Cu and Pt) have been added to generate different active centers in the oxides. Therefore, an array of eight sensors has been obtained (Table 1).

Results The sensor array has been tested with different concentrations of ammonia and toluene, obtaining a fast detecting and recovery response (Fig. 1a and 1b). In addition, each concentration was measured four times, being the repetitive responses for each array sensor. Each sensor showed a different frequency shift, sometimes with a response in opposite sense, due to the change in the different properties (electrical and gravimetric ones) of the layer of nanoparticles doped with the metals. Figure 2a shows the maximum frequency shift for the exposure of each sensor of the array to 100 ppm of ammonia and toluene. The different response of each array sensor did possible to use the principal component analysis (PCA) to discriminate different concentrations of each compounds (Fig. 2b).

Conclusions Sensitive layers of nanoparticles have certain advantages over continuous films, such as the ease of preparation (deposition by spinning) and their increased sensitivity due to their high surface area. The results show that the Love wave sensor array is highly effective in detecting gases due to the change in electrical properties and density in the layers of the nanoparticles of the oxides. In addition, the response of each oxide changes dramatically when different metallic center actives are incorporated. It has been proved that the Love wave sensor array and the choice of materials for this present study have been effective in obtaining high sensitivity, selectivity, and reproducibility. Fast detection and

recovery responses have been achieved as well, detecting concentrations as low as 5 ppm of toluene and 10 of ammonia.

References [1] Adeel Afzal, Naseer Iqbal, Adnan Mujahid, Romana Schirhagl, Analytica Chimica Acta 787, (2013),36-49[2] V. Bhasker Raj, Harpreet Singh, A.T. Nimal, M.U. Sharma, Vinay Gupta, Sensors and Actuators B 178, (2013), 636-647

Table 1: Sensor array composition.

Sensor S1 S2 S3 S4 S5 S6 S7 S8

Metal Oxide ZnO TiO2 ZnO TiO2 ZnO TiO2 ZnO TiO2

Active Centers -- -- Co Co Cu Cu Pt Pt

Fig. 1: Real time response of a) sensor S8 to different concentrations of ammonia and b) sensor S2 to different concentrations of toluene.

Fig. 2: a) Sensor response to 100 ppm of ammonia and toluene. b) Representation of the first two principal component of the PCA to discriminate different compounds and different concentrations.

(Two pages abstract format: including figures and references.

Please follow the model below.)

Raman, SERS and DFT study of chemically-adsorbed thiobenzoic acid on silver nanoparticles

M.R. Lopez-Ramirez, J.F. Arenas, J.C Otero and J.L. Castro

Universidad de Málaga, Facultad de Ciencias, Departamento de Química Física, Campus de Teatinos s/n, 29071 Málaga, España

[email protected]

AbstractThiocarboxylic acids are organosulphur compounds with general formula RC(O)SH. They are related to carboxylic acids by the replacement of one oxygen by sulphur. Two tautomers are possible, written as RC(S)OH and RC(O)SH. The second one is the majority species in solid state and solution of thiobenzoic acid (TBA) at room temperature [1], but derivatives from both tautomers are known so that the SERS spectrum can be originated by either one. Taking advantage of the fact that SERS spectroscopy is both surface selective and highly sensitive we have attempted to determine the molecular structure of TBA once it is adsorbed on the metal surface. To accomplish this SERS spectra of TBA have been recorded on different silver colloids. A combination of layer-by-layer method with spin-coating deposition of silver nanoparticles have been used to prepare SERS active substrates on which the homogeneity of the SERS signal of TBA has been analyzed. Fig. 1 (I) shows the Raman spectra of TBA in the neat liquid (a), 1 M aqueous solution at pH 14 (b), SERS spectrum of a 5x10

-4 M silver colloid prepared by reduction of silver nitrate with sodium

borohydride at pH 7 (c) and SERS spectrum of a 5x10-4

M silver colloid prepared by reduction of silver nitrate with hydroxylamine hydrochloride (d). The assignment of the Raman spectra has been based on the present work as well as on previous studies [2-4]. The two bands recorded at 1662 and 2572 cm

-1 in

Fig.1a, are assigned to ν(C=O) and ν(SH) modes, what confirms that the Raman spectrum in the neat liquid is due to the thiolic specie of TBA, RC(O)SH. In the Raman spectrum of the solution (Fig. 1b) a

significant redshift of ν(C=O) mode of 52 cm-1

and the absence of the ν(SH) band are detected in agreement with the behavior observed in the SERS spectrum (Fig. 1c). The latter confirms that the thiol tautomer of thiobenzoate anion, RC(O)S

-, is adsorbed on silver nanoparticles. Other important SERS

enhancements have been registered for the following vibrational modes: 8a;νring, ν(C=O) and ν(CS)

recorded at 1592, 1554 and 928 cm-1

in Fig. 1c and 1d, respectively. The last two modes, ν(C=O) and

ν(CS), undergo wavenumber shifts of +40 and -40 cm-1

respectively, which are closely related with the coordination of thiobenzoate anion to the metal surface [5]. The analysis of the vibrational wavenumber of these modes suggests that this molecule shows unidentate coordination through the sulphur atom to the metal surface. In order to confirm this fact DFT calculations have been carried out for different silver complexes: I) bridging bidentate ligand, (II) chelating ligand and (III and IV) unidentate ligand (Fig. 2). Theoretical wavenumber of representative bands of these compounds have been compared to the experimental one concluding that the behavior of the unidentate ligand (III) is the most probably coordination type of TBA on the metal surface. In order to confirm these conclusions the SERS spectra of TBA on silver colloid prepared by reduction of silver nitrate with hydroxylamine hydrochloride at different concentration of analyte have been recorded as well (Fig. 1 (II)). It is well known that the SERS enhancement factor depends strongly on different factors and in particular on the adsorption properties of the probe and the analyte concentration on the surface coverage. In this sense TBA has shown a very good detection level for this particular

silver colloid it being a highly SERS active molecule. The detection limit is estimated to be 0.01 µmolar. Finally, Fig. 3 shows a representative Raman mapping of TBA adsorbed on a silver substrate prepared by spin-coating. Generally speaking, the image represents a fairly homogeneous distribution of the SERS intensity highlighting some points where the intensity is stronger as is expected in areas with heterogeneous coverage. The reproducibility of this type of substrate is under study focusing their application as reproducible and ultrasensitive sensing assemblies by using TBA as the target molecule due its good SERS sensitivity.

References [1] D. Delaere, G. Raspoet, M.T. Nguyen, J. Phys. Chem. 103 (1999) 171-177. [2] M. Pagannone, B. Fornari, G. Mattei, Spectrochim. Acta, 43A (1987) 621-625. [3] M.R. Lopez-Ramirez, C. Ruano, J.L. Castro, J.F. Arenas, J. Soto, J.C. Otero, J. Phys. Chem. C 114(2010) 7666-7672.

[4] M. Boczar, K. Szczeponek, M.J. Wójcik, C. Paluszkiewicz, J. Mol. Struct., 700 (2004) 39-48. [5] V.V. Savant, J. Gopalakrishnan, C.C. Patel, Inorg. Chem., 9 (1970) 748-751.

Figure 1. (I) Raman spectra of TBA in the neat liquid (a), 1 M aqueous solution at pH 14 (b), SERS spectrum of 5x10

-4 M of TBA on Ag NPs obtaining by reduction with sodium borohydride (c) and SERS

spectrum of 5x10-4

M of TBA on Ag NPs obtaining by reduction with hydroxylamine hydrochloride (d). (II) SERS spectrum of TBA on Ag NPs obtaining by reduction with hydroxylamine hydrochloride at different concentration of this molecule.

(I) (II)

500 1000 1500 3000

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2400 2600 2800

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10-8 M

10-7 M

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n In

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sit

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10-4 M

Figure 2. Optimized geometries of TBA Ag-complexes calculated at B3LYP/Lanl2dz level of theory.

Figure 3. Raman mapping image (30x40 µm) of TBA on silver substrate prepared by spin-coating.

1200 1400 1600 1800

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��

DEVELOPMENT AND CYTOTOXICITY OF NOVEL SILANE-MODIFIED CLAYS INTENDED TO A

NANOCOMPOSITE MATERIAL FOR THE FOOD INDUSTRY

S. Maisanaba1*

, M. Jordá-Beneyto2, N. Ortuño

2, S. Aucejo

2, A. Jos

1

1 Area of Toxicology, Faculty of Pharmacy, University of Seville, Profesor García González n°2, 41012

Seville. Spain. ([email protected])

2Packaging, Transport & Logistics Research Institute (ITENE), C/ Albert Einstein,1. Parque Tecnológico.

Paterna, Spain.

Abstract: Polymeric materials have traditionally been filled with natural or synthetic compounds to

improve their properties, such as barrier, mechanical and thermal properties. The characteristics of

particle-reinforced polymeric composites are strongly influenced by the dimensions and structure of the

dispersed phase. Nowadays, the incorporation of silane-modified clays is a great alternative, obtaining

novel nanocomposite materials with better technological profiles in comparison twith the raw polymers.

Several authors have evaluated the modification and safety of different clays [1,2, 3]. The Technological

Institute of Packaging, Transport and Logistic has developed two novel silane-modified clays, Clay3 and

Clay4, intended to be incorporated to polypropylene (PP) for their use in the food packaging area. The

incorporation of the silane-modifiers to montmorillonite has been evaluated through different methods

[4], and compared with the unmodified clay (Fig.1). Interlayer space have been enlarged with the silane

modification in clay 3. Results of interlayer space are shown in Table 1. It can be observed that the

interlayer space in clay3 is twice of the raw clay (N116). This is an important step to reach a good

exfoliation in the final nanocomposite.

Moreover, taking in account their use as food contact material, their safety to consumers should be

evaluated. In this regard, a preliminary toxicity study has been performed by means of different cell

viability biomarkers. The human liver HepG2 cell line was selected as target of toxic substances

absorbed by oral exposure. Cells were exposed to concentrations between 0 and 250µg/mL of Clay3 and

Clay4, determining total protein content (PC) and MTS tetrazolium salt reduction (MTS). Clay3 did not

show toxicity in the range of concentrations tested in both biomarkers (Fig. 3). However, HepG2

exposed to Clay4 presented significant differences in the PC in all times of exposure considered (Fig. 4).

In conclusion, novel silane-modified clays with improved properties have been obtained, but their safety

should be further studied previously to their commercial use.

The authors wish to thank Junta de Andalucía (AGR5969) and Ministerio de Ciencia e Innovacion

(AGL2010-21210) for the financial support.

References

[1] Jorda-Beneyto, M., Ortuño, N., Devis, A., Aucejo, A., Jos, A., Gutierrez-Praena, D., Puerto, M., Pichardo, S.,

Houtman, J., Maisanaba, S., 2013. Use of nanoclay platelets in food packaging materials. Technical and toxicological

aspects. Food. Addit. Contam. DOI:10.1080/19440049.2013.874045

[2] Houtman, J., Maisanaba, S., Puerto, M., Gutiérrez-Praena, D., Jordá, M., Aucejo, S., Jos,A., 2013. Toxicity

assessment of organomodified clays used in food contact materials on human target cell lines, Appl. Clay. Sci.

http://dx.doi.org/10.1016/j.clay.2014.01.009

[3] Maisanaba, S., Puerto, M., Pichardo, S., Jordá, M., Moreno, F.J., Aucejo, S., Jos, A.,2013a. In vitro toxicological

assessment of clays for their use in food packaging applications. Food Chem. Toxicol. 57, 266-275.

[4] De Paiva L.B, Morales A.R., Díaz F.R.V. 2008. Organoclays: Properties, preparation and applications. Applied Clay

Science 42, 8 24.

Figures

Figure 1. X-ray spectrum of raw clay N116, and organosilane-modified clays (Clay3 and Clay4).

Muestra 2 d001 (Å)

N116 8.85 9.99

Clay3

7.29

4.70

12.13

18.80

Clay4 7.17 12.33

Table 1. Interlayer space results of raw clay N116, and organosilane-modified clays (Clay3 and Clay4).

Figure 3. Protein content, PC (a) and reduction of tetrazolium salt, MTS (b) of HepG2 cells after 24 h and 48 h of exposure to 0 250

µg/mL Clay3. All values are expressed as mean ± SD.

Figure 4. Protein content, PC (a) and reduction of tetrazolium salt, MTS (b) of HepG2 cells after 24 h and 48 h of exposure to 0 250

µg/mL Clay4. All values are expressed as mean ± SD. *p<0.05 and

**p< 0.01 significant and very significant different from control,

respectively.

0

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120

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** ** ** **

** ** **

0

20

40

60

80

100

120

140

0 1.9 3.9 7.8 15.6 31.3 62.5 125 250

% o

f co

ntr

ol

Clay4 (µg/mL)

MTS 24h 48h

MUTAGENICITY POTENTIAL OF A MODIFIED CLAY PRESENT IN A NANOCOMPOSITE MATERIAL

INTENDED TO FOOD PACKAGING AND ITS MIGRATION EXTRACT

S. Maisanaba1*

, AI. Prieto1, S. Pichardo

1, M. Jordá-Beneyto

2, A.M. Cameán

1, A. Jos

1

1 Area of Toxicology, Faculty of Pharmacy, University of Sevilla, Profesor García González n°2, 41012

Seville. Spain. ([email protected])

2

Packaging, Transport & Logistics Research Institute (ITENE), C/ Albert Einstein, 1. Parque Tecnológico.

Paterna, Spain.

Abstract: Modified clays with ammonium quaternarium salts are currently used to develop new

packaging materials for the food industry. These improved materials are known as nanocomposites. In

previous works a modified montmorillonite clay, Clay1, and the migration extract from a polylactic acid-

Clay1 nanocomposite (PLA-Clay1) have been studied in regard to their possible toxicity to the

consumers, due to their potential migration from the nanocomposite to the food [1,2]. But there is no

information about their mutagenic potential. The incorporation version of the Ames test was performed

according to the recommendations of Maron and Ames [3] and following the principles of the OCDE

guideline 471 [4]. Five Salmonella typhimurium histidine-auxotrophic strains TA97A, TA98, TA100, TA102

and TA104 were used for the assay. Five different concentrations of Clay1 (0.5-8 µg/mL) and PLA-Clay1

extract (20-100%) were assessed in three independent experiments. Each assay was conducted in

absence and presence of S9 metabolic activation system from rats livers, using triplicate plates for each

test substance concentration. Revertant colonies were counted and background lawn was inspected for

signs of toxicity or compound precipitation. 2-Nitrofluorene (2-NF) (0.1 µg/plate) and sodium azide

(NaN3) (1µg/plate), were selected as positive controls in absence of S9 metabolic fraction and 2-

Aminofluorene (2-AF) (20 µg/plate) in presence of S9 metabolic fraction. In general, Clay1 demonstrated

a mutagenic effect while PLA-Clay1 extract did not showed any mutagenic effect at the concentrations

tested (Table 1). Further safety studies should be carried out before these kinds of materials could be

widely used in the food industry.

The authors wish to thank Junta de Andalucía (AGR5969) and Ministerio de Ciencia e Innovacion

(AGL2010-21210) for the financial support.

References

[1] Houtman, J., Maisanaba, S., Puerto, M., Gutiérrez-Praena, D., Jordá, M., Aucejo, S., Jos,A., 2013.

Toxicity assessment of organomodified clays used in food contact materials on human target cell lines.

Appl. Clay. Sci. (Accepted)

[2] Maisanaba, S., Pichardo, S., Jordá-Beneyto, M., Aucejo, S., Cameán, A.M., Jos, A. 2014. Cytotoxicity

and mutagenicity studies on migration extracts from nanocomposites with potential use in food

packaging. Food. Chem. Toxicol. (Accepted).

[3] Maron, D.M., Ames, B.N., 1983. Revised methods for the Salmonella mutagenicity test. Mut. Res.

113, 173-215.

[4] OCDE., 1997. Guideline for Testing of Chemicals 471: Bacterial Reverse Mutation Test. pp 1-11.

Table 1

a C

(µg/mL) TA97A TA98 TA100 TA102 TA104

Clay1

-S9 +S9 -S9 +S9 -S9 +S9 -S9 +S9 -S9 +S9

Negative

controls 216±28 206±12 21±3 38±14 85±16 80±18 183±25 216±45 252±45 285±45

0.5 241±75 213±30 25±7 68±12* 91±26 87±17 142±45 166±12 221±51 228±54

1 236±69 254±55 29±10 144±22# 79±15 79±24 180±25 230±43 252±69 236±54

2 211±54 254±51 35±10 303±100# 70±11 88±18 189±48 173±66 270±73 367±69

4 262±70 260±87 28±8 521±26# 89±21 85±18 281±72 242±67 309±51 341±86

8 211±26 260±51 34±20 150±61# 80±15 89±32 218±84 202±41 295±47 323±83

Positive

controls 387±60

# 485±86

# >1000

# >1000

# 347±50

# 411±120

# 483±51

# 541±29

# 749±120

# >1000

#

b C (%) TA97A TA98 TA100 TA102 TA104

PLA-

Clay 1

Extract

-S9 +S9 -S9 +S9 -S9 +S9 -S9 +S9 -S9 +S9

Negative

controls 338±54 402±18 21±4 20±1 115±25 123±34 246±40 246±65 320±59 326±26

20% 368±2 286±67 23±9 22±6 100±26 104±35 221±92 236±30 349±7 320±99

40% 409±65 438±10 21±3 24±5 109±19 101±40 324±76 352±62 409±65 418±40

60% 320±11 424±11 27±4 32±2 124±20 122±1 353±120 365±57 307±16 284±22

80% 343±42 357±22 18±1 25±1 107±29 96±36 256±9 297±47 295±61 256±42

100% 271±49 342±34 21±3 30±5 154±8 143±1 272±53 260±8 266±41 286±40

Positive

controls 751±24

# 722±28

# >1000

# >1000

# >1000

# >1000

# 621±172

# 853±174

# 884±79

# >1000

#

Table 1. Results of the Ames test conducted with Clay1 (a) and PLA-Clay1 extract (b) in three

independent experiments. Water was used as negative control and DMSO as solvent for positive

controls. Data are given as mean±SD revertants/plate for three replicates for each concentration in each

experiment. Positive controls: TA97A/ TA98/ TA102/ TA104 without S9: 2-NF (0.1 µg/plate) and TA100

without S9: NaN3 (1µg/plate). 2-AF was used in presence of S9. *p<0.05 and #p< 0.01 significant and very

significant different from control, respectively.

FeNi thin films deposited onto polymer-FeNi nanoparticles composite substrates

Lourdes Marcano1, G.V. Kurlyandskaya

1, A.P. Safronov

2,3, N.S. Volodina

2, I.V. Beketov

2,3

1 Dept. Electricity and Electronics, Basque Country University UPV-EHU, Campus of Leioa, 48940,

Leioa, Spain 2 Institute of Natural Sciences, Ural Federal University, Lenin Ave 51, 620000, Ekaterinburg, Russia

3 Institute of Electrophysics UD RAS, Amundsena 16,

[email protected]

Abstract Magnetic nanoparticles (MNPs) are the subject of intensive research due to the special

properties required for technological and biomedical applications [1]. It was shown earlier that fundamental magnetic characteristics including the saturation magnetization depend on the variations of size and shape of MNPs [2-3]. MNPs embedded in polymer matrices are an excellent example of functional nanostructuers with potential for application such as biomedical sensing devices, flexible electronic, electromagnetic shielding, magnetic inks and adhesives etc. [3-4]. The composite would have a lighter weight then a purely metallic compound but may have comparable and even better electromagnetic properties, with the possibility of other multi-functionality. The compounds could be also used as covers to protect sensors or other electronics form corrosion while increasing the sensitivity of the sensor. One of the expanded areas are flexible substrates for magnetic field sensors and biosensors based on giant magnetoimpedance [5]. In this work we designed, fabricated and tested polymer/FeNi MNPs/thin FeNi film composites for electronic applications.

The electrophysical method of electric explosion of wire (EEW) was used for the fabrication of FeNi MNPs. Detailed description of EEW installation can be found elsewhere [6]. The roll of FeNi wire (Fe – 48 wt%, Ni – 52 wt% diameter 0.5 mm) was positioned at the top of the feeding mechanism which pushed the wire into the reaction chamber through a calibrated hole in the metal contact plate, playing the role of the upper electrode of a parallel plate capacitor. The electrodes were connected to a direct current high voltage source. The voltage applied to the electrodes was 30 kV and the distance between the contact plates was 70 mm. The specific surface of the permalloy MNPs was determined by low temperature nitrogen adsorption technique (BET) using Micromeritics TriStar 3000. FeNi-filled composites were prepared based on the commercially available acrylic copolymer of 95% of butyl methacrylate and 5% of methacrylic acid hereafter marked as BMK-5. Liquid casting method for the composites preparation was elaborated. Acrylic polymers are versatile and well compatible with most of the inorganic materials including metals and metal oxides due to the presence of polar ester groups inthe monomeric units. The composites containing 0 and 5 wt. % of MNPs were prepared. Fe20Ni80 thin films of 100 or 200 nm were deposited onto polymer, composite and glass substrates by rf-sputtering (Figure1).

The X-ray powder diffraction patterns were collected on a Bruker D8 Advance diffractometer equipped with a Cu tube, Ge(111) incident beam monochromator (k = 1.5406 A). The sample was mounted on a zero background silicon wafer embedded in a generic sample holder. Preliminary identification of the initial phases was evaluated using the Powder Diffraction File (PDF) database. PANalytical X’Pert High Score program was used for identification and Miller indexing of all observed maxima. Scanning electron microscopy (SEM) was done by JEOL JSM-7000F operating at 30 kV. The X-ray powder diffraction data were in good agreement with single phase FeNi cubic bcc structure The calculated average crystallite size d = 45 ± 5 nm is in a good agreement with SEM results. Comparative analysis of structural features and magnetic properties of FeNi films deposited onto polymer and polymer/FeNi MNPs substrates revealed certain advantages of composite substrates (perhaps due to the thermal and electric conductivity providing better conditions for the sputtering deposition). The next steps will be to improve adhesion between composite and metallic film, to improve magnetic anisotropy of FeNi films and to study microwave properties of obtained composites. References

[1] J. Llandro, J.J. Palfreyman, A. Ionescu, C.H.W. Barnes, Med. Biol. Eng. Comput., 48 (2010) 977. [2] Y.-W. Jun, J.-W. Seo, J. Cheon, Acc. Chem. Res., 41 (2008) 179. [3] J. Slama, R. Vicen, P. Krivošik, A. Grusková, R. Dosoudil J. Magn. Magn. Mater., 196 (1999) 359. [4] G. Jianping, L. Howon, H. Le, J. Am. Chem. Soc., 131 (2009)15687. [5] E. Fernández, A. V. Svalov, A. García-Arribas, J. Feuchtwanger, J. M. Barandiaran, G. V. Kurlyandskaya, J. Nano. Nanotech., 12 (2012) 7496. [6] G.V. Kurlyandskaya, S.M. Bhagat, A.P. Safronov, I.V. Beketov, A. Larrañaga, AIP Adv., 1 (2011) 042122

Figures:

Figure 1. Structural features of the samples studied by SEM: (a) FeNi MNPs. Polymer/5% FeNi MNPs FeNi film of 100 nm (top view): MNPs are seen through the metal film and their distribution can be studied (b). Thin FeNi film of 100nm deposited onto glass substrate has very low roughness (c). FeNi thin film of 100 nm deposited onto polymer substrate without MNPs - higher roughness and specific “wave” structure (comparing with FeNi film deposited onto substrate with FeNi MNPs) shows a disadvantage of pure polymer substrate.

Figure 2. X-ray powder diffraction pattern including (hkl) Miller Index for the EEW FeNi MNPs, composite polymer/FeNi MNPs and FeNi films deposited onto composite substrates (a). Hysteresis loops of FeNi nanoparticles and MNPs in polymer matrix (5% concentration), inset shows primary magnetization curves difference (b). Although the saturation magnetization (recalculated on the mass of the nanoparticles) is only slightly lower in the case of the composite there is a clear difference in the primary magnetization curve slope.

(a)

(b)

Anti-wetting surfaces fabricated by Reverse Nanoimprint Lithography on Silicon and metal-coated substrates

Ariadna Fernández

1, Juan Medina1, Cristian Benkel3, Markus Gutteman3, Brian Bilenberg4, Theodor Nielsen4, Clivia M. Sotomayor Torres1,2, Nikolaos Kehagias1

1Catalan Institute of Nanoscience and Nanotechnology, ICN2 Building, UAB Campus, 08193 Bellaterra,

Barcelona, Spain, 2 ICREA, Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain

3 Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1 Building 307, D-76344 Eggenstein-Leopoldshafen, Germany

4NIL Technology ApS, Diplomvej 381, DK-2800 Kongens Lyngby, Denmark

[email protected]

Reverse Nanoimprint Lithography (RNIL) is a well-established technique, which has been used to imprint selectively thin polymer films over flat and or pre-patterned surfaces1. The unique feature of this modified nanoimprint lithography technique is the possibility to control the presence or absence of a residual layer. Moreover, the capability of sequential imprinting over pre-patterned surfaces resulting in three-dimensional structuring by RNIL has been demonstrated2. In this paper we report a further development of the RNIL technique to pattern micro/nano scale polymer patterns over metal substrates without a residual layer and test them as anti-wetting surfaces. In this work we demonstrate that RNIL is a feasible and flexible lithography technique applicable to transfer micro and nanometer-scale polymer structures with no residual layer over cm2 areas on silicon and metal substrates. We used two different flexible Polydimethylsiloxane (PDMS) stamps, one with positive and the other with a negative relief, which have honey comb-like hydrophobic features. Despite the fact that our stamp has a design which repels water, we were able tofine tune the surface properties of the PDMS stamps to deposit uniformly the resist on them. In this regard, surface functionalization of the flexible stamp by organic solutions proved to be useful, reducing the contact angle between the resist and the stamps surface by 31%, leading to a clear improvement of the RNIL results (Figure 1). We present RNIL results of anti-wetting surfaces, which were imprinted using the commercial resist mr-NIL6000E (microresist technology GmbH) over silicon wafers (Figure 2) and over Nickel-coated steel wafers leaving no residual layer. Moreover, we discuss the imprinting parameters and alleviate some of the main problems previously identified, such as: residual layer or pattern distortion. Specifically, our im g = 40 oC) and the pressure was kept as low as 2 bar, reducing the undesired spread and pattern alteration. Small pressures also help to minimize the presence of residual layer3. Both positive and negative patterns of honeycomb lattice features were successfully transferred showing hydrophobic properties, with contact angles 115o and 91o, respectively. Acknowledgments

The authors acknowledge support form the EU FP7 project PLAST-4-FUTURE FP7-2012-NMP-ICT-FoF, under Grant Agreement number 314345 (www.plast4future.eu). References [1] L.-R. Bao et al., J. Vac. Sci. Technol. B 20 (2002) 2872. [2] N. Kehagias et al. J. Vac. Sci. Technol. B 24 (6) (2006) 3002. [3] B-D. Chan et al. Microelectron. Eng. 86 (2009) 586.

Figures

Figure 1: Contact angles between the resist and the PDMS stamp before (left) and after (right) the surface functionalization.

Figure 2: a) Photograph of a 1.2 x 1.2 cm2 pattern transferred on a Nickel-coated steel substrate, b) tilted scanning electron microscope (SEM) image of a positive hydrophobic pattern transferred by RNIL on a silicon wafer with no residual layer (inset: top view SEM image showing the transfer of a negative anti-wetting surface with patterned line widths of 500 nm and no residual layer).

Preparation of PtM catalysts by electrodeposition for methanol oxidation

Júlia Peraferrer-Hereu, Elisa Vallés, Elvira Gómez, Manuel Montiel

Grup d'Electrodeposició de Capes Primes i Nanoestructures, Dpto Química FísicaInstituto de Nanociencia y Nanotecnología - Universidad de Barcelona (IN2UB)

Martí i Franquès 1, 08028, [email protected]

Abstract

During the last decades fuel cells have attracted a great interest as an alternative form of energy production due to its high efficiency and low environmental impact [1]. A fuel cell is an electrochemical device that converts continuous and directly the chemical energy of a fuel source (hydrogen, alcohols…) and oxygen to electricity. These devices operate continuously while the electrodes are fed, unlike batteries, which have a limited capacity. They consist of two electrodes separated by a proton conductive membrane. At the anode occurs the oxidation of fuel and at the cathode the oxygenreduction. The direct methanol fuel cells (DMFC) are a type of polymer electrolyte membrane fuel cell (PEMFC) using aqueous solutions of liquid methanol (MeOH) as fuel. One of the advantages of the methanol compared to hydrogen is that MeOH is liquid, which allows easier handling, transportation and storage, and, moreover, it has a higher energy density and a lower price than hydrogen. The major drawback of these devices is the slow kinetics of methanol oxidation making necessary the use of catalysts. Platinum is the best metal that catalyzes the oxidation of methanol but it is easily poisoned by CO, a product resulting from the oxidation. Binary or ternary alloys of platinum such as ruthenium, cobalt or nickel decrease the poisoning and increase the catalytic activity toward complete methanol oxidation [2].

The main objective in this work was to obtain, by using electrodeposition techniques, a PtM nanoparticleseries to catalyze the methanol oxidation reaction (MOR). Electrodeposition allows obtainingnanoparticles in a quick and easy way, although the deposits can only be performed on conductive material. In our case, this need turned what looks like a disadvantage into an advantage, since our intention was the direct preparation of nanoparticles on carbonaceous supports [3]. The composition of the prepared materials and the particle size were modulated by varying applied potential and deposition method. These materials have been morphologically characterized and evaluated as electrocatalysts for methanol oxidation in half-cell. SEM micrographs of these materials deposited on glassy carbon or carbon cloth showed homogeneous and well-distributed deposits (Figure 1). Moreover, their catalytic activity toward methanol oxidation in acidic media is a promising feature (Figure 2).

Acknowledgements

Financial support from the MINECO contract CTQ2010-20726 (subprogram BQU) is grateful acknowledged. The authors wish to thank the Centres Científics i Tecnològics de la Universitat de Barcelona (CCiTUB). M. Montiel acknowledges the Generalitat de Catalunya for support in the form of a Beatriu de Pinós postdoctoral fellowship.

References

[1] Liu, X.-J.; Cui, C.-H.; Ming, G.; Li, H.-H.; Xue, Y.; Fan, F.-J.; Yu, S.-H. Chem. Commun. 49 (2013) 8704.

[2] Antolini, E.; Salgado, J. R. C. Applied Catalysis B: Envirommental, 63 (2006) 137 – 149.

[3] Zhao, Y.; E, Y.; Fan, L.; Qiu, Y.; Yang, S. Electrochimica Acta. 52 (2007) 5873 – 5878.

Figures

Figure 1.SEM micrographs of various deposits of PtM on microporous carbon cloth: PtCo; PtNi, and PtCoNi.

Figure 2. Cyclic voltammetric curve of a PtCo catalysts for MOR in 0.5 M H2SO4 + 1.0 M MeOH solution at a sweep rate of 10 mV s-1.

Amphiphilic Block Polymers based on Polypeptides as Versatile Drug Nanocarriers

V. J. Nebot, L. Conesa-Milián, A. Duro-Castaño, I. Conejos-Sánchez, M. J. Vicent.

Polymer Therapeutics Laboratory, Centro de Investigación Principe Felipe, Eduardo Primo Yúfera 3,Valencia, [email protected]

Abstract

Using polymers as drug delivery vehicles can increase the solubility of drug molecules, making itpossible to deliver them systemically, can decrease generalized toxicity effects and provide enhancedcirculation and residence times, and improve targeting within the body. Polymer-drug conjugates havedemonstrated excellent potential in this regard, with several now in the marketplace or clinical trials astreatments for cancer and other medical conditions [1]. A step further into the development of the nextgeneration of polymer conjugates for biomedical applications will be the design of self-assembled andmultifunctional architectures from amphiphilic block copolymer conjugates which would provide severalbenefits over the use of single polymers [2,3]: (i) First of all, passive targeting (EPR effect) will beachieved since most of the self-assembled nanocarriers (micelles, vesicles) can be designed in the sizerange of 10 to 200 nm without compromising the biocompatibility/biodegradability due to the smallernature of their self-assembling components; (ii) A modular and multifunctional architecture will allow tointroduce in the design active targeting moieties, therapeutics, imaging probes, stimuli responsive cross-linkers, etc....; (iii) pharmacokinetics might be modulated through an additional trigger (aside from thecleavable conjugation bonds): the disassembly of the nanocarriers in response to physiological inputs(temperature, redox, pH, enzymes, ionic strength...); (iv) hybrid nanostructures might help to move theconcept of combination therapy towards more sophisticated and tailored polymer therapeutics[4]. Anumber of new architectures based on poly-L-glutamic acid (PGA), Poly-L-leucine (PLeu) andPolyethylene glycol (PEG) including diblock and triblock (block and random) systems have beenobtained by means of the ring opening polymerisation of the γ-benzyl-L-glutamic acid and L-Leucine N-Carboxyanhydrides (NCA) by nucleophilic PEG initiators [5]. Additionally, we have modified the PGAmoieties introducing stimuli bioresponsive cross-linkers such as thiols and therefore providing aversatile platform for drug delivery. Preliminary characterizations of these systems through DynamicLight Scattering, NMR-Diffusion Ordered Spectroscopy (DOSY), Transmission Electron Microscopy(TEM) and Fluorescence have shown the adjustable critical micelle concentration and size of theassembled micelles through the molecular architecture. Moreover, thiol-functionalized triblockcopolymers have been designed for the encapsulation of a model hydrophobic drug and its releaseunder reductive environment has been tested as a proof of concept.

[1] M. J. Vicent and R. Duncan (Eds.). Polymer Therapeutics: Clinical Applications and Challenges forDevelopment. 2009 61(13), 1117.[2] J. Nicolas, S. Mura, D. Brambilla, N. Mackiewicz and P. Couvreur, Chem. Soc. Rev, 2013, 42, 1147.[3] M. Elsabahy and K. L. Wooley, Chem. Soc. Rev. 2012, 41, 2545.[4] J. Lin, J. Zhu, T. Chen, S. Lin, C. Cai, L. Zhang, Y. Zhuang and X.-S. Wang, Biomaterials, 2009, 30,108.[5] Vicent M.J., Barz M., Canal F., Conejos I., Duro A. Patent Application P201131713.

Surface modified Eu:GdVO4 nanocrystals for optical and MRI imaging

Nuria Nuñez,a Sara Rivera,b David Alcantara,b Jesus M de la Fuente,b Jorge García-Sevillanoc and Manuel Ocañaa

aInstituto de Ciencia de Materiales de Sevilla, CSIC-US, Américo Vespucio 49, 41092, Isla de la

Cartuja, Sevilla, Spain. bInstituto de Nanociencia de Aragon, Universidad de Zaragoza, Campus Rio Ebro, Edif I+D, C/ Mariano

Esquillor s/n, 50018, Zaragoza, Spain cDpto. Física de Materiales, C-04. Universidad Autónoma de Madrid, 28049 Madrid, Spain

E-mail: [email protected]

Abstract Nowadays, much attention is been paid in the biomedical field to the development of multifunctional nanoparticles suitable for both, optical and magnetic resonance (MRI) imaging applications[1-5] because they combine the high sensitivity of optical imaging for in vitro applications with the excellent spatial resolution and depth for in vivo application associated to the MRI imaging.[6-8] In this work, we have developed a simple method for the synthesis of uniform Eu-doped GdVO4 nanocrystals (70 nm) with optimised luminescent properties and their functionalization with amino (two steps procedure) and carboxylate (one-pot procedure) groups provided by amino-dextran polymers (AMD) and polyacrylic acid (PAA), respectively.[9] The luminescent and magnetic (relaxivity and phantom analyses) properties of the functionalized nanoparticles along with their negligible cytotoxicity and high colloidal stability in aqubiolabels and negative contrast agent for magnetic resonance imaging (Figure 1). References [1] G. Tian, Z. Gu, X. Liu, L. Zhou, W. Yin, L. Yan, S. Jin, W. Ren, G. Xing, S. Li and Y. Zhao, J. Phys.

Chem. C, 115 (2011) 23790. [2] J. W. Mulder, A. W. Griffioen, G. J. Strijkers, D. P. Cormode, K. Nicolay and Z. A. Fayad,

Nanomedicine, 2 (2007) 307. [3] J. Ryu, H. Y. Park, K. Kim, H. Kim, J. H. Yoo, M. Kang, K. Im, R. Grailhe and R. Song, J. Phys.

Chem.C,114 (2010) 21077. [4] M. He, P. Huang, C. Zhang, H. Hu, C. Bao, G. Gao, R. He and D. Cui, Adv. Funct. Mater., 21 (2011)

4470. [5] L. Zhou, Z. Gu, X. Liu, W. Yin, G. Tian, L. Yan, S. Jin, W. Ren, G. Xing, W. Li, X. Chang, Z. Hu and

Y. Zhao, J. Mater. Chem., 22 (2012) 966. [6] Padmanabhan, K. K Bhakoo, S.

T. Selvan and T. Y. Tan, Langmuir, 26 (2010) 8959. [7] X. Yu, Y. Shan, G. Li and K. Chen, J. Mater. Chem., 21 (2011) 8104. [8] N. J. J. Johnson, W. Oakden, G. J. Stanisz, R. S. Prosser and F. C. J. M. van Veggel, Chem.

Mater., 23 (2011) 3714. [9] N. Nuñez, J. M. de la Fuente, S. Rivera and M. Ocaña, Dalton Transactions, 42 (2013) 10725.

Figures

Figure 1. Morphology, luminescence and T2 parametric MRI phantom images of europium-doped GdVO4 nanoparticles functionalized with PAA.

Toxicity of inhaled gold nanoparticles in the pest species Blattella germanica

M.A. Ochoa-Zapatera*, J. Querol-Donata, F.M. Romerob, A. Riberab, A. Torreblancaa, M.D. Garceráa.

a Departamento de Biología Funcional y Antropología Física, Universitat de València, Dr. Moliner 50,

46100 Burjassot, Valencia, Spain. b Instituto de Ciencia Molecular, Universitat de València, Catedrático José

Beltrán, 2. 46980, Paterna, Valencia, Spain. *[email protected]

Abstract The widespread application of engineered nanoparticles and nanomaterials in the development of new products raises as many doubts about environmental hazards as any new technology. Understanding and assessing the toxicity and potential environmental risks of nanomaterials, preventing thus adverse effects [1,2], is necessary to ensure the responsible development of new nano-products. Unfortunately, in most cases the in vivo toxicity profile of many manufactured nanoparticles and nanomaterials remains still unknown. In our study we investigated the toxicity effects of inhaled gold nanoparticles that could be used in the development of functionalized nanoparticles for insecticide application in the treatment of pest insects. In our case we have studied the german cockroach Blattella germanica, which is an important pest in the urban environment and represents a serious threat to public health [3]. AuNPs (average size of 21,8 nm) were synthetized as described in the article by Bastús et al. [4] and were characterized by UV-Vis and Transmission Electron Microscopy (TEM). A nebulizer based system was used to deliver 1mL and 2mL solution of AuNPs in sodium citrate (2,2·10-4 ± 7·10-6 g Au/L) to the respiratory system of adult cockroaches with times of total exposure ranged between 15 to 90 minutes (figure 1). Each bioassay was replicated three times using 30 insects (15 females and 15 males) aged 1-6 days from the same laboratory-reared population. Mortality rates were monitored post-treatment at 24h intervals during 4 days. In order to bring out possible sub-lethal effects of inhaled AuNPs, glutathione S-transferases (GSTs) and esterases (p-NPA) enzymatic activities, related to oxidative stress and insecticide resistance [5], were measured in insects frozen immediately after nebulization (table 1) and 96h post-treatment for every bioassay. The activity rates thus obtained were later compared with the results of our previous studies in tarsal contact toxicity bioassays. Finally, inductively coupled spectroscopy (ICP-OES) was performed to check inhaled AuNPs intake in treated insects and if

Acknowledgements: this work has been supported by grant AGL2010-21555 from the Ministerio de Economía y Competitividad. References [1] Y. Pan, A. Leifert, D. Ruau, S.Neuss, J. Bornemann, G. Schmid, W. Brandau, U. Simon and W. Jahnen-Dechent, Small, 3 (2007) 1941-1949. [2] S. Arora, J.M. Rajwade, K.M. Paknikar, Toxicol. Appl. Pharmacol., 258 (2012) 151-165. [3] J. Roberts, Br. Med. J., 312 (1996) 1630. [4] N.G. Bastús, J. Comenge, V. Puntes, Langmuir, 27 (2001) 11098-11105. [5] J. Hemingway, H. Ranson, Annu. Rev. Entomol., 45 (2000) 371-391.

Figures

Table 1. Au content in treated insects with nebulized AUNPs; Au content was measured at times 0h and 96h post-treatment by ICP-OES. Au was not detected at 96h after treatment with nebulized nanoparticles in any of the bioassays.

Au g /g wW a (±SD)

Duty b (%)

1mL

c 2mL

c

100 0,762±0,378 1,999±0,590

75 1,041±0,585 1,902±0,281

50 0,729±0,386 1,499±0,663

25 1,402 1,821±0,931

10 1,114 3,076±1,033

5 0,639±0,106 2,700±1,370

a, wW, wet weight b, % of nebulized solution per cycle, 1 cycle equals 6 seconds c, Volume of AuNPs solution (2,2·10-4 ± 7·10-6 g Au/L).

Figure 1. Adult individuals of Blattella germanica inside the nebulization chamber during the AuNPs inhalation bioassay.

Spanish innovation and market on nanotechnology: an analysis within the H2020 framework

Cristina Paez-Aviles1, Esteve Juanola-Feliu1, Josep Samitier1,2,3

1Department of Electronics, Bioelectronics and Nanobioengineering Research Group (SIC-BIO),

University of Barcelona, Martí i Franquès 1, Planta 2, 08028 Barcelona, Spain. [email protected] 2IBEC-Institute for Bioengineering of Catalonia, Nanosystems Engineering for Biomedical Applications

Research Group, Baldiri Reixac 10-12, 08028 Barcelona, Spain [email protected] 3CIBER-BBN-Biomedical Research Networking Center in Bioengineering, Biomaterials and

Nanomedicine, María de Luna 11, Edificio CEEI, 50018 Zaragoza, Spain [email protected]

Abstract

This document provides a broad overview of the state-of-the-art of nanotechnology innovation and market perspective in Spain, looking forward the Europe s Horizon 2020 strategy. Key Enabling

Technologies (KETs) are the priorities of this framework, and nanotechnology is considered one of the most promising KET since for many is becoming the engine of the next industrial revolution [1],[2]. The

inasmuch as Nanotechnology is a relevant strategy with high potential and scope for economic and social growth. An analysis of this KET is crucial to identify the strengths and improve weaknesses so that Spain can satisfactorily face new scientific and market challenges in the nanotech-related science. Horizon 2020 is a Framework Program based on R&D, created to redefine the cooperation in funding and scientific research of the EU countries. This 6-year proposal (2014-2020) counts with 80 billion budget, promoting economic growth by turning scientific breakthroughs into innovative products and services [3]. Innovation is considered a key element to achieve H2020 proposal goals, so six strategic KETs are priorities of this framework: nanotechnologies, micro and nano electronics, photonics, advanced materials, biotechnology industry and advanced manufacturing systems, considered as significant accelerators for innovation and competitiveness of industries [4],[5]. Technology innovation, related capital and human investment shapes the National Innovation System of a country [6]. In this regard, the Global Entrepreneurship Monitor (GEM) report (2014) state that

- -capacity/low- he Innovation Efficacy Index (IEI) [7], and classified by

European Regional Competitiveness Index (RCI). Spanish surveyed experts also agreed that the scientific and technologic potential in Spain is above the average [2]. This evidence the presence of a gap between high levels of scientific performance on one hand and the minimal contributions to industrial competitiveness and new venture entrepreneurship on the other [7] [10]. Innovative activities can be measured by patents and publications [11] [13]. Major contributors in Nanotechnology patent applications during the last decade are USA, Japan, Europe, Korea, and China [14]. Concerning the significance in total patent applications of KETs in Spain, Nanotechnology and Industrial Biotechnology are the lowest in number (Figure 1). There is also a worldwide increment of nanotechnology publications. China, USA, South Korea, India, Germany, Japan, France, the Islamic Republic of Iran, England and Spain were the top 10 countries in Nanoscience and Nanotechnology publications of 2012 [15]. In Spain, nanomaterials are considered highly attractive and specialized fields, meanwhile technologies that are below the average and demonstrate weakness are nanodevices, hardwares and techniques of analysis, control and measure, as well as nano fabrication, manipulation and integration [2]. At present, the emerging sector of applied nanotechnology is addressed to the biomedicine (nanobiotechnology and nanomedicine) [16], starting to show a promising impact in the health sciences: diagnostics and treatments of diseases, as well as the development of new drugs and novel ways of administration. In this regard, biosensors, biochips, cellular chips, active implants, bioreactors

for cellular bi and tridimentional growth, tissue engineering, drugs administration, and genetic sequencing are considered consolidated areas of specialization with the greatest projection in the future and with a prospective of commercialization in 2020 [2]. There are some nanotech products that are already in use [17], in fact, the global nanotechnology market is anticipated to grow around 19% by year during 2013-2017 [18]. According to the Phantoms Foundation (2013), there are 94 Nanoscience and Nanotechnology companies in Spain that are mostly situated in Madrid, Aragon, País Vasco, Comunidad Valenciana, Navarra, Andalucía, and Cataluña. Although the nanotech industry is growing, this document aboard some difficulties implied. Much of the science and technology developed in research labs aren t commercialized [19]. Particularly, nanomedicine firms have focused primarily on the science and less on the commercial applications resulting difficult to bring products to market [9]. Solutions are needed in this aspect through more investigation about this important gap in the development progress of the nanotechnologies industry. Furthermore, performance evaluation of this KET is imperative in order to get better insights on how to obtain an effectively approach and improvement within the H2020 framework. References [1] Authors, Journal, Issue (Year) page. [1] E Juanola-Feliu, et al., Technovation, 32 (2012) 193. [2] Observatorio de Prospectiva Tecnológica Industrial, Report (2008) 78. [3] D. Kalisz and M. Aluchna, Eur. Integr. Stud. 6 (2012) 143. [4] European Commission, Report (2009) 8. [5] ECSIP consortium, Report (2013) 10. [6] E. Milbergs and N. Vonortas, White Paper (2005) 2. [7] S. Mahroum and Y. Al-Saleh, Technovation, 33 (2013) 329. [8] J. D. Linton and S. T. Walsh, Int. Small Bus. J., 26, (2008) 83. [9] T. Flynn and C. Wei, Nanomedicine, 1 (2005) 47 51. [10] K. Debackere, R D Manag., 30 (2000) 323-328. [11] P. Mohnen and M. Dagenais, (2000) 1. [12] L. G. Zucker, M. R. Darby, J. Furner, R. C. Liu, and H. Ma. Res. Policy, 36 (2007). 850-863. [13] I. H. Lee, E. Hong, and L. Sun, J. Bus. Res., 66 (2013) 2109. [14] European Commission,Observatory NANO Factsheets ( 2011). [15] J. Hongfang and L. Lerwen, Report (2014). [16] K. Miyazaki and N. Islam, Technovation, 30 (2010) 235. [17] E. Juanola-Feliu, Manag. Int., 13 (2009) 116 [18] RNCOS, Report (2013). [19] J. D. Linton and S. T. Walsh, Technological Forecasting and Social Change 75 (2008) 583-594. Figure

Figure 1: Significance in total KETs patent applications in Spain (source: OECD KETs observatory

https://webgate.ec.europa.eu/ketsobservatory/)

The role of grain boundaries on light species behavior in nanostructured tungsten

Miguel Panizo-Laiz1,*, N. Gordillo1,2, F. Munnik3, , E. Tejado4, J. Y Pastor4, J. M. Perlado1 and

R. Gonzalez-Arrabal1

1 Instituto de Fusión Nuclear, ETSI de Industriales, Universidad Politécnica de Madrid, C/ José

Gutierrez Abascal, 2, E-28006 Madrid, Spain

2CEI Campus Moncloa, UCM-UPM, Madrid, Spain

3Helmholtz-Zentrum Dresden-Rossendorf, PO.Box 10119, D-01314 Dresden, Germany

4Departamento de Ciencia de Materiales CISDEM, ETSI de Caminos, Universidad Politécnica

de Madrid, E-28040 Madrid, Spain

*[email protected]

Abstract

A great challenge in the design of future nuclear power plants is to develop materials capable to resist the hrash conditions taken place in a nuclear fusion reactor. Nowadays, tungsten (W) is one of the most important candidates proposed to form the first wall in a nuclear fusion reactor, because of its low sputtering yield, low-activation, high melting point, high thermal conductivity and low thermal expansion [1]. Nevertheless, this material has some limitations which must be overcome in order to satisfy the specifications, among them, the light species retention. Light species (mainly H, D, T and He), which are present in the plasma in magnetic confinement fusion and which result from the explosion in inertial confinement fusion, are implanted in PFM, notably degrading its properties [2-4]. In this work we focus on the study the influence of sample microstructure and of irradiation conditions in nanostructured tungsten (NW) coatings as compared to commercial coarse grained tungsten (CGW) samples in the hydrogen behaviour. To this aim, NW and CGW samples were implanted with (i) H at an energy of 170 keV, (ii) sequentially implanted with C (665 keV) and H (170 keV) and co-implanted with C (665 keV) and H (170 keV). Implantations were carried out at a fluence of 5x1016 cm-2 and at two different temperatures RT and 400ºC. Scanning electron microscopy (SEM) images show that, after irradiation, nanostructured samples preserve its nanometric features and that there is no sign of blistering in any of the studied samples. X-ray diffraction (XRD) data indicate that all the samples keep being mono-

-W phase) after irradiation and that no secondary phases appear after the implantation of H and/or C. Resonant nuclear reaction analysis (RNRA) data reveal that H concentration for samples implanted only with H is higher for NW than for CGW, and it becomes comparable for both kind of samples after sequential implantation with C and H. Increasing the temperature during irradiation up to 400ºC leads H to completely out diffuse in NW as well as in CGW samples. The role of microstructure and radiation-induced damage on light species behaviour is discussed. References

[1] H. Bolt, V. Batrabash, W. Krauss, J. Linke, R. Neu, S. Suzuki, N. Yoshida, ASDEX Upgrade team, Journal of Nuclear Materials (2005) 329-333, 66

[2] C. Garcia-Rosales, P. Franzen, H. Plank, J. Roth and E. Gauthier, Journal of Nuclear Materials (1996) 233-237, 803 [3] P. Franzen, C. Garcia-Rosales, H. Plank and V. Kh. Alimov, Journal of Nuclear Materials (1997) 241-243, 1083 [4] O. V. Ogorodnikova, J. Roth, M. Mayer, Journal of Nuclear Materials (2003) 313-316, 469

Electronic and transport properties of graphene based systems with divacancies

Marta Pelc

1,2, Leonor Chico2 1, Andres Ayuela3

1Instytut F - 2Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid, Spain

3Centro de Física de Materiales de Madrid, CSIC-UVP/EHU, Departamento de Física de Materiales, Fac. Químicas, UPV/EHU,

and Donostia International Physics Center (DIPC), 20080 Donostia, [email protected]

Abstract

There is a growing interest on structural defects in graphene, either extended in defect lines or separated as mono- and multi-vacancies. The appearance of these defects has been experimentally observed in different graphene-based systems [1,2] and can significantly modify the electronic, magnetic and transport properties [3-6]. Such defects naturally appear during the growth process but have also been introduced on purpose using electron or ion irradiation [7]. Among those defects, vacancies are well-known to show atoms in topologies such as pentagons, heptagons and octagons. We here deal with the particular case of divacancies, where the hexagonal graphene structure usually reconstructs into an octagon accompanied by two pentagons (the so-called 5-8-5 defect), as shown in the Fig. 1. Since such defects can spontaneously appear in graphene systems or be created intentionally, we theoretically study these vacancies in semiconducting graphene nanoribbons and carbon nanotubes. We investigate the influence of such defects on the electronic and transport properties of graphene nanoribbons and carbon nanotubes. We consider the orientation of vacancies before and after reconstruction, and vary the nanoribbon width or roll up the ribbon into a zig-zag nanotube. We also consider ribbons with pairs of such defects. In our calculations, we focus on the armchair ribbons as they have no edge states that could mix with the defect-localized state. -electron tight binding approximation (TB) with hopping parameter t =-2.7 eV. For non-periodic systems, like a single defect in a perfect ribbon, we use the Green function matching technique to calculate the local density of states (LDOS) and conductance. Band structures and the corresponding wave functions are obtained for superlattices with periodical 5-8-5 defects using the TB Hamiltonian direct diagonalization. We find that the presence of divacancies leads to the appearance of gap states. In different cases, we have obtained one or two states appear in the gap. We have observed that in some particular cases, they may act as acceptor or donor states (see Fig. 2). The gap states we observe are mainly localized on the defect. By varying the hopping parameters, we investigate the source of these states, what shows that they originate from the octagonal ring states [8] References [1] A. Lherbier, S. M.-M. Dubois, X. Declerck, Y.-M. Niquet, S. Roche and J.-C. Charlier, Phys. Rev. B

86, 075402 (2012).

[2] J. M. Carlsson and M. Scheffer, Phys. Rev. Lett. 96, 046806 (2006).

[3] M.Pelc, L. Chico, A. Ayuela and W. Jaskólski, Phys. Rev. B, 87, 165427 (2013).

[4] W. Jaskólski, M. Pelc, L. Chico and A. Ayuela, IEEE Conference on Nanotechnology, 1, 1 (2012).

[5] R. R. Nair, M. Sepioni, I-Ling Tsai, O. Lehtinen, J. Keinonen, A. V. Krasheninnikov, T. Thomson, A.

K. Geim and I. V. Grigorieva, Nature Phys. 8, 199 (2012).

[6] S. Kattel, P. Atanassov, and B. Kiefer, J. Phys. Chem. C, 116, 8161 (2012).

[7] M. M. Ugeda, I. Brihuega F. Guinea and J. M. Gomez-Rodriguez, Phys. Rev. Lett. 104, 096804

(2010)

[8] M. Pelc, W. Jaskolski, A. Ayuela, and L. Chico, Acta Phys. Pol., 124, 777-780 ( 2013).

Figures

Fig. 1. A model of a graphene nanoribbon with a divacancy reconstructed into an octagonal topological defect accompanied by two pentagons.

a)

b) Fig. 2. Local density of states (LDOS) on the 5-8-5 defect introduced in a 9-AGNR (a) and CN (5,0) (b). In the case of the nanoribbon we observe only one gap state, while in the LDOS of the nanotube we observe appearance of two states, which play the role of an occupied acceptor state and an unoccupied donor state.

Magnetic solid-phase extraction based on palmitate coated magnetite nanoparticles for the analysis of PAHs in soil leachates

Rosa Ana Pérez, Beatriz Albero, José Luis Tadeo, María Victoria Fraile, Consuelo Sánchez-Brunete

Departamento de Medio Ambiente, INIA, Ctra de la Coruña, Km 7, 28040 Madrid, Spain.

[email protected]

Polycyclic aromatic hydrocarbons (PAHs) are toxic substances that are resistant to degradation and

have been included in the European Union list of priority pollutants [1]. Soil is an important reservoir of

these contaminants but, due to their hydrophobic nature and low water solubility, a measurement of

their total remaining amount in soil is a poor indicator of its potential environmental impact.

Solid-phase extraction (SPE) is the methodology most commonly used in the analysis of pollutants in

aqueous samples; nevertheless, this is a time consuming and laborious technique for large sample

volumes. Magnetic SPE (mSPE) methods using magnetic nanoparticles (MNPs) have been recently

applied to the separation and pre-concentration of pollutants in environmental matrices, mainly in water

samples. In recent years, nanoparticles of magnetite (Fe3O4) subjected to different surface modifications

(using surfactants, polymeric coating, biosorption thin-film, etc.) were assayed as new mSPE

adsorbents.

In this work, mSPE using palmitate (PA) coated magnetite NPs coupled with gas chromatography-

tandem mass spectrometry (GC-MS/MS), was developed for the extraction of 16 PAHs from soil

leachates. Finally, the developed methodology was applied to evaluate the PAHs leached from soils

with different physico-chemical characteristics.

Experimental

GC MS/MS analysis was performed with an Agilent 7890A gas chromatograph equipped with a

multimode inlet (MMI) and coupled to an Agilent Model 7000 triple quadrupole mass spectrometer

Model 7000. The MMI was operated in solvent vent mode with a liner packed with glass wool. The

optimized chromatographic program consisted on three MS/MS transitions, one quantifier and two

qualifier transitions, for most of the target compounds. Analytes were confirmed by their retention time

and the identification of target and qualifier transitions. The quantification of the studied compounds was

based on their relative response factor to seven calibration standards in the range from 2 to 80 ng mL-1.

Each calibration level was spiked with 50 ng mL-1 of labelled internal standards.

Soil Extraction. Extraction and clean-up of PAHs from soil were carried out by ultrasound assisted

extraction (UAE) following a procedure previous developed by our group for the analysis of these

compounds in soil [2].

Soil leachates were obtained by placing 5 g of soil in centrifuge tubes together with 50 mL of ultrahigh-

quality water. Samples were rotated during 24 h using an overhead shaker Heidolph at ambient

temperature. Then, the tubes were centrifuged at 4500 rpm for 30 min and supernatants were collected

and filtered through glass fibre filters, 2.1 cm dia ore size, placed at the end of 20 mL

glass columns.

Preparation and characterization of the MNPs. PA coated MNPs were obtained following the

procedure described by Ballesteros and Rubio [3]. The morphology and particle size of the coated

MNPs were examined by transmission electron microscopy (TEM) in a JEOL JEM 2100. Element

analysis was performed with a LECO CHNS-932 microanalyser. The spectroscopic study was

conducted on a Jasco FTIR-460 Plus spectrophotometer.

mSPE procedure. A 50 mL volume of soil leachate, 2.5% of acetone and 200 mg of PA-coated MNPs

were mixed in a 100 mL conical flask closed with a glass cap. The flasks were stirred for 45 min using a

Vibromatic Rocking at a vibration frequency of 370 oscillations min-1. Then, the MNPs were isolated by

placing the magnet on the wall of the flask and discarding the soil leachate. The MNPs were then

extracted twice with 2 mL of ethyl acetate and the combined extracts were concentrated to 1 mL.

Finally, the labelled standard solution was added and the extract was injected into the GC-MS/MS

system for analysis.

For recovery studies, soil leachates were spiked with the appropriate working solutions in methanol, the

fortified samples were extracted by mSPE following the procedure described above.

Results and discussion

Surface modification of the Fe3O4 NPs with PA was confirmed by TEM, element analysis and Fourier

transform infrared spectroscopy. The effect of several parameters on the extraction efficiency of 16

PAHs from soil leachates was evaluated. Firstly, the type of agitation, sample volume (50 and 100 mL),

extractive solvents of the PAHs from the MNPs (acetonitrile and ethyl acetate) were evaluated, followed

by the evaluation of the effects of different parameters that could affect the performance of the

extraction, such as the extraction time (15, 30 and 45 min), salt addition (0, 0.1 M and 0,2 M KCl),

percentage of organic solvent in the extract (from 0 to 10%) and the amount of NPs (100 and 200 mg).

The optimal extractive procedure is described in the experimental section.

Efficiency of the nanoparticles for the extraction of PAHs from soil leachates was evaluated.

Recoveries of these contaminants from soil leachates spiked at three different fortification levels, from

0.2 to 1 ng mL-1, were low for the four PAHs with lower molecular weights and satisfactory for the rest

(ranging from 68 to 120% for the others, with standard deviations < 9 %). The developed method

provided a preconcentration factor of, at least, 50 times and the limits of detection ranged from 0.8 to

5.1 ng L-1.

Finally, the developed method was successfully applied to soil leachates obtained from soils with

different physico-chemical characteristics. The amount PAHs present in the leachates may be explained

by the soil organic matter content together with other soil characteristics.

The present work demonstrates the applicability of the PA-Fe3O4 NPs for the determination of PAHs

in soil leachates, which is of interest for mobility and bioavailability studies of these pollutants in soil. As

far as we know, this is the first reported study on the application of MNPs to the analysis of

contaminants in soil leachates.

Acknowledgements

This study was financed by the Ministry of Science and Innovation-National Institute for Agricultural

-00047-00-

References [1] L. Guzzella, G. Poma, A. De Paolis, C. Roscioli and G.Viviano, Environ. Pollut. 2011, 159, 2552-

2564.

[2] C. Sánchez-Brunete, E. Miguel and J. L. Tadeo. J. Sep. Sci., 29 (2006) 2166-2172.

[3] A. Ballesteros-Gómez, and S. Rubio. Anal. Chem. 2009, 81 (2009) 9012-9020.

Localized heating of Nd

3+- doped glasses using silica microspheres as focusing lenses

C. Pérez-Rodríguez1, L. Labrador-Páez1, I. R. Martín1,2 and S. Ríos3

1 Departamento de Física Fundamental y Experimental, Electrónica y Sistemas, Universidad de La Laguna, Av. Astrofísico Francisco Sánchez, s/n, E-38206 La

Laguna, Tenerife, Spain 2 MALTA Consolider Team, Instituto de Materiales y Nanotecnología (IMN),

Universidad de La Laguna, Av. Astrofísico Francisco Sánchez, s/n, E-38206 La Laguna, Tenerife, Spain

3 Departamento de Física Básica, Universidad de La Laguna, Av. Astrofísico Francisco Sánchez, s/n, E-38206 La Laguna, Tenerife, Spain

Abstract The photonic nanojet that emerges from micrometric sized cylinders and spheres is a brand new subject of research that shows a high potential of application [1]. Basically it consists on a beam of high intensity and non-evanescent light with sub-diffraction waist that appears behind the mentioned systems under suitable illumination conditions. In previous works [2,3] we have explored the light confinement capability of silica microspheres over rare earth doped glasses and its capability to produce upconversion. The combination of the focusing properties of the microspheres and the nonlinear dependence of the upconversion intensity yield spots as narrow as 238 nm. In this work we have employed an Nd3+ doped substrate that under excitation at 532 nm shows a two band spectrum in the 780-950 nm range. Due to the thermalization of the Nd3+ levels the ratio of the intensities of these two bands (see Fig. 1) is temperature dependent. A proper thermal calibration of this ratio is possible employing a dependence that follows a Boltzmann type population distribution. This method is known as Fluorescence Intensity Ratio [4,5]. Microspheres of 2, 7 and 25 µm diameter were sparse over the substrate in order to concentrate the 532 nm laser excitation. The thermal dependence of the Nd3+ spectra can be appreciated just by tuning up the power of the laser excitation. The aim of this research is to measure the Nd3+ thermalized spectra in the focal region of each microsphere and analyze its dependence with the sphere diameter. As can be seen in Fig. 1 the microsphere with 2 µm diameter produces a greater heating in the substrate. Therefore, the thermal variation in the focal region of a 2 µm diameter silica sphere over a glass substrate doped with Nd3+ ions produce an increment about 150 K (see Fig. 2). Moreover we have performed Finite Differences Time Domain (FDTD) simulations of the electromagnetic field surrounding silica microspheres. The microspheres are in contact with the glass substrate with refractive index 1.525 under illumination at 532 nm in order to model our experimental conditions. These simulation results show a nanojet emerging from a microsphere and propagating in the bulk material with a jet width that increases with sphere diameter. This theoretical outcome led to infer that the confinement of excitation light in to the Nd3+ substrate is expected to be greater employing the smaller microspheres. Consequently, the greater heating in the substrate could be explained by the FDTD simulations. References

[1] V. B. Alexander Heifetz, Soon-Cheol Kong, Alan V Sahakian, Allen Taflove, J Comput Theor Nanosci. 6, (2009) 1979

[2] C. Pérez-Rodríguez, S. Ríos, I. R. Martín, L. L. Martín, P. Haro-González, D. Jaque, Opt. Express 21, (2013) 10667

[3] C. Pérez-Rodríguez, S. Ríos, I. R. Martín, J. Opt. Soc. Am. B 30, (2013)1392

[4] S. A. Wade, S. F. Collins, G. W. Baxter, J. App. Phys, 8 (2003) 4743

[5] C. Pérez-Rodríguez, L. L. Martín, S. F. León-Luis, I. R. Martín, K. K. Kumar, and C. K. Jayasankar, Sensors Actuators B Chem. 195, (2014) 324

Figures

780 800 820 840 860 880 900 920 9400,0

0,2

0,4

0,6

0,8

1,0

2 m

7 m

25 m

25 m

No

rmal

ized

in

ten

sity

(ar

b.

un

its)

Wavelength (nm)

x5

Fig. 1. Emission spectra obtained in the focal region emerging from different sized microspheres. The spectra shown in continuous lines were measured under excitation at 532 nm with 300 mW while the spectrum plotted with a dashed line was obtained with 12 mW. Fig. 2. Thermal variation in the focal region (shown in the inset) of a 2 µm diameter silica sphere over a glass substrate doped with Nd3+ ions.

0 50 100 150 200 250 300 350

300

320

340

360

380

400

420

440

460

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Maleimide-activated Carbon Nanoonion modified glassy carbon electrodes for electrochemical DNA detection

Joanne P. Bartolome1 and Alex Fragoso1*

1

Rovira i Virgili, Avinguda Països Catalans 26, 43007 Tarragona, Spain [email protected], [email protected]

Abstract

Carbon nanoonions (CNOs) are the least studied allotropes of carbon but are equally important as carbon nanotubes, graphenes and fullerenes. CNO is a multilayered fullerene concentrically arranged one inside the other and typically their size average ranges from 5nm to 50nm in diameter [1]. Similar to other carbon nanomaterials, CNOs are generally insoluble in organic and inorganic solvents thus the physical and chemical properties have not yet been well explored for many years. To improve their dispersability, CNOs were chemically functionalized [2] or incorporated in polymer composites [3] and matrices [4] to exploit their electromagnetic properties and capacitive behavior. CNOs have also been incorporated in microsupercapacitors [5] exploiting their fast charging and discharging rates and as additive in lubricant due to their tribological structure [6]. CNOs are electrically conductive and possess a much larger surface area than single-walled carbon nanotubes (SWCNTs) and are thus potential candidates for the development of miniaturized fuel cells and biosensors [7].

In this work, we have been used pristine CNOs to modify the surface of glassy carbon electrode (GCE) activated with electrografted diazonium salts bearing phenylmaleimide groups. The unmodified CNOs were purified with hydrogen peroxide, dispersed in DMF by tip sonication and characterized by TEM. Subsequently, the solution has been drop-casted into the surface of GCE and characterized by AFM. The modified surface was electrografted with N-(4-aminophenyl)maleimide diazonium salt and used to immobilize 6-(ferrocenyl)-hexanethiol and thiolated DNA probes. The modified surfaces were characterized by cyclic voltammetry in terms of surface coverage and the results were compared with GCE modified only with diazonium salt. The presence of CNO provoked a significant enhancement of current intensity, higher surface coverage area and a decrease in detection limits.

References

[1] (a) Sano, N. et al. Nature,414( 2001) 506. b) Roy, D. et al. Chem. Phys. Lett., 373(2003) 52 c) Delgado, JL. et al. J.Mater.Chem.,18(2008)1417. [2] Georgakilas, V. et al. J. Am. Chem. Soc.,125(2003)14428. [3] Breczko, J. et al. J. Mater. Chem.,20(2010)7761. [4] (a) Shenderova, O. et al. Diamond Relat.Mater.,16 (2007)1213. b) Macutkevic, J. et al. Diamond Relat. Mater.17(2008)1608. [5] Rettenbacher, AS.et al.Chem. Eur. J. 12 (2006)1521. [6] Pech, D. et al. Nature Nanotech., 5(2010)651. [7] Hirata, A. et al. Tribol. Int.,37(2004)899.

Figures

Figure 1: Glassy carbon electrode (GCE) surface modification with carbon nanoonions followed by electrochemical grafting of N-(4-aminophenyl)maleimide for DNA detection using a sandwich assay.

Figure 2: TEM image and size distribution chart of purified CNOs

Acknowledgement: Financial support from Ministerio de Economía y Competitividad (Spain) under the grant BIO2012-30936 is gratefully acknowledged.

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Antifouling properties of membranes containing

Metal-organic frameworks (MOFs)

Jennifer Quirós1, Sonia Aguado1, Karina Boltes1, 2, Roberto Guzmán3, Juan J. Vilatela3, Roberto Rosal1, 2

1Department of Chemical Engineering, University of Alcalá, 28871 Alcalá de Henares, Madrid, Spain 2Madrid Institute for Advanced Studies of Water (IMDEA Water Institute), E-28805, Alcalá de Henares,

Madrid, Spain 3 Madrid Institute for Advanced Studies of Materials (IMDEA Materials Institute), C/ Eric Kandel 2,

Tecnogetafe, 28906, Getafe, Madrid, Spain Email contact: [email protected]

Introduction

Membrane technologies have been used for the production of drinking water and wastewater treatment in order to meet the stringent regulatory requirements for drinking water and the discharge limits related to nutrient discharge. In spite of their widespread use, the industrial application of membrane processes is hindered by the control of membrane fouling [1].

Fouling is caused by the accumulation of organic and inorganic substances, as well as biofilm formation due to the deposition or growth of microorganisms. Some recent works has been oriented to the inclusion of antimicrobial substances to prevent biofilm growth [2-3].

This work presents a new approach to prepare composite polymeric membranes for water filtration that include metal organic frameworks (MOFs), an important class of hybrid organic-inorganic crystalline porous materials [4]. Two cobalt imidazolate MOFs and one Ag coordination polymer (AgTAZ) as comparison were evaluated as a bactericidal material before being introduced in the spun membranes. The control of release of metal gives excellent antibacterial activities and durability against gram negative bacteria and yeast.

Evidence of high antimicrobial activity on bacterial growth on membranes loaded with different MOFs will be presented. Our data show that MOFs produced with simple, cheap and commercially accessible linkers are suitable for use in membrane technology for cleaning water with reduced biofilm formation.

Keywords: fouling; membranes; metal-organic frameworks

1. MATERIALS AND METHODS

AgTAZ is prepared with a polyazaheteroaromatic compounds, 1, 2, 4-triazole. ZIF-67 (Co(Hmim)2) is isostructural to ZIF-8,17. Co-SIM-1 (cobalt-based Substituted Imidazolate Material) is a novel analogue of its zinc-based parent SIM-1; they were synthesized by solvothermal procedure.

Electrospun was prepared with tLLC, UK, molecular weight of A NANON-01A electrospinning unit was examined using a scanning electron microscope (SEM) from Carl Zeiss (EVO MA15). A fluorometer/luminometer Fluoroskan Ascent FL was used for recorder the fluorescence emitted for bacterias over all membrane surface and grown culture. To evaluate the bacterial activity of MOFs, two commercially available strains of gram negative bacteria E. coli CECT 4102 and P. putida CECT 4584, gram positive bacteria S.aureus CECT 240 and the yeast Saccharomyces cerevisiae CECT 1170 were used as model microorganisms.

2. RESULTS AND DISCUSSION

The as-prepared microorganisms were subjected to an antibacterial experiment using a diffusion method. On an agar plate inoculated with different the strains, we place approximately 1 mg of the materials to be evaluated. Both MOFs based on cobalt ions show a significant antibacterial activity, with an inhibition diameter of around 15 mm. Surprisingly, AgTAZ appears to be the weakest to inhibit the growth of the

bacterial strains (inhibition diameter of 2 mm). This initial experiment shows that both ZIF-67 and Co-SIM-1 are able to diffuse in this medium and to inhibit the growth of all microorganisms used. We also performed tests to determine the biocidal effect of the tested materials in suspension as well as the release of free metals to the solution. These experiments were carried out after 20 h of incubation, when the bacteria are in their exponential growth phase. As shown in Figure 1, MOFs displayed interesting antimicrobial properties against bacteria and yeast.

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Fig. 1 Bactericidal performance of of AgTAZ, ZIF-67 and Co-SIM-1 against S. cerevisiae, P. putida and E. coli.

After these results we took the appropriate MOF for realize the electrospun (Co-SIM-1) according bacterial performance and showed better properties for the process of electrospinning. SEM micrographs of electrospun fibers with MOFs are shown in Figure 2. As expected, monodispersed Co-SIM-1 nanoparticles were located on the fibers. Fibers were mostly bead-less and homogeneity in diameters.

Fig. 2 SEM micrographs of (A and B) unloaded neat PLA, (C, D and E) PLA/CoSIM-1 fibers

On membranes different test were made, after 24 hours of contact with grown medium the membranes were placed in contact with agar plates and incubated approximately 20 hours. It shows less growing of bacteria the ones in contact with CoSIM-1 fibers. A process of dehydration and drying with acetone and ethanol was then carried out to analyze the membranes by SEM. The membranes without CoSIM-1 shown strong biofilms in different parts of sample, especially for S.aureus, reduction of biofilms was remarkable with MOF fibers. Another tests for quantify the biocidal effect was made by LIVE/DEAD, bacterial viability kit, and fluorescein diacetate (FDA). Two different measures were realized, solid and liquid phase, in solid phase were present the membranes after 20 hours contact with grown culture, a lecture over all surface of membrane was taken. We determinate the optimum integration time where the bacterium was in the high point of exponential growing phase in contact with blank membrane. Liquid phase was made with supernatant from the contact between bacteria and membranes. Abiotic blank was made with the objective to know if in the absence of bacteria there were fluorescence emission that is not related to the activity of the organism and a negative blank to know optimal growth conditions.

3. CONCLUSIONS

A B C

In summary, our work demonstrates that it is possible to use metal organic frameworks based on cobalt as antibacterial materials. The materials exhibit remarkable antibacterial activities and durability, due to the control of the release of cobalt ions in biocidal solutions. The incorporation of these MOFs within the polymer matrix of a fiber was successful and it shows bactericidal properties.

4. REFERENCES

[1] Kennedy, M.D., Kamanyi, J., Salinas-Rodríguez, S.G., Lee, N.H., Shippers, J.C., amy, G., Water treatment by microfiltration and ultrafiltration in N.N. Li, A.G. Fane, W.S.Winston Ho and T. Matsuura (Eds.) Advanced Membrane Technology and Applications, John Wiley & Sons, New Jersey, 2008, pp. 131 170.

[2] Feng, Q.L., Wu, J., Chen, G.Q., Cui, F.Z., Kim, T.N., Kim, J.O., 2000. A mechanistic study of the antibacterial effect of silver ions on Escherichia coli and Staphylococcus aureus, J. Biomed. Mater. Res. A. 52, 662 668.

[3] Dasari, A., Quirós, J., Herrero, B., Boltes, K., García-Calvo, E. and Rosal, R., 2012. Antifouling membranes prepared by electrospinning polylactic acid containing biocidal nanoparticles. J. Membr. Sci. 405 406, 134 140.

[4] Belser, K., Slenters, T. V., Pfumbidzai, C., Upert, G., Mirolo, L., Fromm, K.M., Wennemers, H., 2009. Silver nanoparticles formation in different sizes induced by peptides identified within slit-and-mix libraries. Angew. Chem., Int. Ed. 48, 3661-3664.

Synthesis of continuous macroscopic fibres with controlled type of CNTs

V. Reguero, B. Alemán, B. Mas, J.J. Vilatela

IMDEA Materials Institute, Eric Kandel 2, Madrid, Spain [email protected]

Abstract

Carbon nanotubes (CNTs) have exceptional mechanical, thermal and electrical properties along the tube axis and which can be exploited on a macroscopic scale by assembling these nanocarbons into a continuous fiber preferentially oriented parallel to each other and to the fibre axis. One of the methods to produce such materials is by direct spinning of CNTs from the gas phase as they grow by chemical vapour deposition (CVD) [1]. In this work, we show significant progress in the challenge of controlling this process to tailor the building blocks that make the fibre in terms of the number of layers and chiral angle of the nanotubes.

The spinning process is based on the growth of CNTs by floating catalysts CVD using an alcohol as carbon source, iron nanoparticle catalysts which then supersaturate and extrude carbon to form very long nanotubes that entangle in the gas-phase forming an aerogel which can be withdrawn continuously to form a fibre of typically 20 m diameter. Clearly, the potential to make kilometers of a macroscopic fibre made up of specific type of CNTs (metallic single-walled nanotubes, multiwalled nanotubes, etc) is interesting both from a scientific and technical view point. Although the key role of the catalyst particle during CNT growth [2] is well-known and some sulphur assisted floating catalyst growth models have been proposed [3-4], numerous aspects of the growth mechanism remain poorly understood.

This work presents results showing that through the addition of sulphur it is possible to control the type of CNTs that make up the fibre, covering the range SWNTs (Figure 1), collapsed DWNTs (Figure 2, including Moiré pattern) and MWNTs. The CNT fibres are studied by Raman spectroscopy, HRTEM, EDX and XPS, which enables us to establish a correlation between S content in the fibre and type of CNTs, and to propose a growth mechanism that explain this selectivity as well as other aspects of the direct spinning process.

References [1] YL. Li, I. A. Kinloch and A. H. Windle, Science, 304 (2004) 276 [2] KKK. Koziol, C. Ducati and A. H. Windle, Chem. Mater., 22 (2010) 4904

[3] W. Ren, F. Li and HM. Cheng, J. Phys. Chem. B, 110 (2006) 16941 [4] M. S. Motta, A. Moisala, I. A. Kinloch and A. H. Windle, J. Nanosci. Nanotechnol., 8 (2008) 1 Figures

Figure 1: High-resolution TEM image of the cross section of CNTs

Figure 2: HRTEM images of bundles of collapsed few-layer CNTs and a Moiré pattern arising from the stack of collapsed graphitic layers.

Synthesis of vertically aligned carbon nanotubes and graphite on stainless steel by chemical vapor deposition

P. Romero1, R. Oro2, M. Campos2, J. M. Torralba1,2, R. Guzman de Villoria1

1IMDEA Materials Institute, C/Eric Kandel 2, 28906, Getafe, Madrid, Spain2Department of Materials Science and Engineering, Universidad Carlos III, Av. Universidad, 30,

Leganés, Spain

[email protected]

Carbon-based nanostructures as graphene or nanotubes are currently under intense investigation due

to their exceptional combination of electrical, thermal and mechanical properties. Although they can be

synthesized by a wide variety of methods, catalytic thermal chemical vapor deposition (CVD) is probably

the most promising one due to its high control and scalability [1], [2]. It consists on the high temperature

decomposition of a hydrocarbon nearby a substrate, where these nanostructures are synthesized. The

election of this substrate is of major importance for the commercial feasibility of CNT-enhanced

materials; a low cost and flexible substrate that can be folded inside a CVD reactor will enable to scaling

up a continuous synthesis process. Thus, metallic foils have been proposed as catalytic substrates to

synthesize graphene sheets of several cm2 [3] or vertically aligned CNTs forest [4].

In this work we studied the synthesis of vertically aligned carbon nanotubes (VACNTs) and graphite by

atmospheric pressure CVD on a stainless steel flexible foil (304 grade). The stainless steel was

pretreated by air-oxidation. In order to perform fast heating and cooling ramps, the furnace was

mounted on a wheeled mobile platform sat on a pair of rails. The CVD process on the stainless steel

consisted on a first reduction step followed by a synthesis step. Both steps were carried out in a tubular

furnace at temperatures between 700ºC to 830ºC.

After the CVD process, we have studied the synthesis products. Regarding the VACNTs, two

temperature intervals were clearly observed; a low temperature interval where VACNTs of a maximum

length of 7 µm are obtained, and a high temperature where a progressive decrease in their length took

place. Raman spectra directly collected on substrates after VACNTs removal, indicated the presence of

a graphitic carbon layer deposited on its surface. In order to corroborate this result, several samples

were etched in acid, and after substrate dissolution, a floating graphite-like layer was observed. TEM

micrographs of CNTs and graphite confirmed the presence of both CNT and graphite (Fig. 1).

A study of the stainless steel at different stages of the process was carried out. The XPS spectra

showed the effect of the oxidation pretreatment, that was the incorporation of Fe2O3 in the original

passivation oxide layer of the stainless steel (Cr2O3), and the next reduction step, that partially reduced

it into metallic Fe. After synthesis at low temperature, the substrate did not substantially change its

surface composition. However, at higher temperature a significant increase of carbon incorporation into

the substrate was detected. The XRD studies showed phase transitions on its surface (martensite to

austenite), and formation of carbides, indicating the sensitization of the stainless steel during the whole

treatment. As a final result, microstructural evolution of a cross section is analyzed by SEM, showing an

acicular microstructure on the pristine stainless steel and an increase of the grains size after synthesis.

A simple and feasible method to synthesize VACNTs forests and graphite on commercially available

stainless steel foil is demonstrated. The oxidation-reduction of the stainless steel prior to the synthesis

step was necessary to obtain VACNTs. However, the VACNTs are not present at high synthesis

temperature (about 780ºC), where a significant incorporation of carbon into the stainless steel was

found, as well as microstructure evolution. Further work needs to be done in order to understand the

growth mechanisms involved in such a heterogeneous substrates so high quality and inexpensive

VACNTs and their related materials can reach the market.

References

[1] V. Jourdain and C. Bichara, “Current understanding of the growth of carbon nanotubes in catalytic chemical vapour deposition,” Carbon, vol. 58, pp. 2–39, Jul. 2013.

[2] C. Mattevi, H. Kim, and M. Chhowalla, “A review of chemical vapour deposition of graphene on copper,” J. Mater. Chem., vol. 21, no. 10, p. 3324, 2011.

[3] S. Bae, H. Kim, Y. Lee, X. Xu, J.-S. Park, Y. Zheng, J. Balakrishnan, T. Lei, H. Ri Kim, Y. I. Song, Y.-J. Kim, K. S. Kim, B. Özyilmaz, J.-H. Ahn, B. H. Hong, and S. Iijima, “Roll-to-roll production of 30-inch graphene films for transparent electrodes,” Nat. Nanotechnol., vol. 5, no. 8, pp. 574–578, Jun. 2010.

[4] R. Guzmán de Villoria, A. J. Hart, and B. L. Wardle, “Continuous High-Yield Production of Vertically Aligned Carbon Nanotubes on 2D and 3D Substrates,” ACS Nano, vol. 5, no. 6, pp. 4850–4857, Jun. 2011.

Fig. 1 Influence of the synthesis temperature on the VACNTs length. a) Low synthesis temperature

leaded to VACNTs, and high synthesis temperature leaded to no observable CNT by SEM. TEM

micrographs indicating a CNT and a graphite flake at b, c) 716ºC and d, e) 830ºC. Graphite layer

detachment during stainless steel dissolution in acid.

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Molecular Dynamics Simulation of BSA Adsorption on a Stepped Graphite Surface.

Rubio-Pereda Pa,b, Vilhena JG

b,c, Vellosillo P

b & Serena P

b.

a Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE) 3918, Código

Postal 22860, Ensenada, Baja California, México

b Instituto de Ciencia de Materiales de Madrid (ICMM) - CSIC, Cantoblanco, E-28049, Madrid, España.

c Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de

Madrid, Cantoblanco, E-28049, Madrid, España.

rubio.pereda@gmail

Abstract Carbon based structures such as pyrolitic carbon and graphene sheets are being used in the

manufacturing of implant materials and bio-inspired sensors respectively due to the apparently good

biocompatibility observed experimentally in these materials. In the case of defective surfaces composed

of atomic steps embedded in solutions with low protein concentration, SPM studies show that the

adsorption of protein occurs preferentially on the step edges, where a higher chemical reactivity is

expected. It is therefore of a fundamental importance to understand how these highly reactive sites,

influence the adsorption of protein in low concentration solutions.

To address this problem we have studied the adsorption of the serum-albumin, the most abundant

plasma protein, onto a stepped graphite surface via molecular-dynamics atomistic simulations. The level

of detail on our simulations such as the inclusion of explicit solvent and physiological ion concentrations

allow us to address several open questions such as the influence on the protein adsorption properties

(secondary structure, free energy, contact area, spreading and diffusion) upon the defect size (number

of steps) and their nature.

References

[1] Aoki, R. et al. Surf. Sci. 601 (2007) 4915-4921.

[2] Mücksch C & Urbassek HM. Langmuir. 27 (2011) 12938-12943.

[3] Allieu Y., et al. Eur. J. Orthop. Surg. Tr. 16 (2006) 1-9.

[4] Zhen L, et al. J. Photoch. Photobio. C.18 (2014) 1-17.

[5] Jarzynski C. Phys. Rev. Lett. 78 (1996) 2690-2693.

Figures

��

Figure 1. Bovine serum albumin (BSA) on top of a stepped graphite surface in explicit solvent. Atoms in

step borders are depicted in color.

Modeling of semiconductor defect properties to extend experimental

characterization capabilities

I. Santos, L. Pelaz, L. A. Marqués, M. Aboy, P. López, M. Ruiz

University of Valladolid, Dept. Electricidad y Electrónica, E.T.S.I. Telecomunicación, Paseo Belén 15, 47011 Valladolid, Spain

[email protected]

Abstract

Semiconductors are intentionally or unintentionally exposed to radiation of energetic particles during processing (ion implantation for doping or ion beam nanopatterning) or during operation (radiation detectors or devices exposed to cosmic radiation). In any case, as energetic particles enter into a crystalline solid and collide with lattice atoms, defects are generated. The interaction and accumulation of structural defects in crystalline semiconductors can lead to phase transformation (crystalline to amorphous [1]), nanostructure formation (honeycombs in germanium [2]) or dopant deactivation (via clustering or precipitation [3]). Structural defects also lead to shallow or deep levels in the gap and may also act as additional scattering centers. This often has adverse effects on the performance of logic devices (increase of leakage currents), the efficiency of solar cells (reduce the charge collection efficiency) or lifetime of radiation detectors (type inversion) [4, 5]. But some defects may also have beneficial applications such as the observed defect-induced-photoluminescence in Si [6], which can transform Si into a light-emitter material.

The understanding of properties and dynamics of defects is a key factor for defining strategies to minimize the negative effects associated to them, and enhance the positive ones. Due to the large variety of defects that can coexist in a material, experimental structural and spectroscopic characterization techniques find it difficult to assign a given signal to a specific defect. We use multi-scale scheme to simulate and model the defect generation mechanisms due to irradiation and the defect evolution upon annealing, as well as to gain insight into the structural, energetic, electrical and optical properties of defects and thus assist experimentalists to interpret their results and provide engineers with clues for process optimization.

Within this multi-scale simulation scheme we have developed an atomistic model for the formation of extended {113} defects in silicon [7], which served to validate a novel structural characterization technique known as unprocessed high-angle annular darkfield scanning TEM [8] as shown in Fig. 1.

We have used classical molecular dynamics techniques to study the imperfect regrowth of FinFET devices [9]. TEM images show the generation of line defects in the FinFET body and the formation of polycrystalline material, which degrade its performance (left side of Fig. 2). Our simulations allowed to relate the formation of such line defects during regrowth of the FinFET body with the particular orientation of the growing amorphous-crystal interface (right side of Fig. 2), and even to give technological clues about how to improve regrowth.

We have used ab initio simulations to study the relevant defects states in amorphous Si (a-Si) and at its interface with crystalline Si, and how these defects interact with charge carriers. We have identified intrinsic hole traps in a-Si associated to locally strained regions (Fig 3), and we have analyzed their interaction with boron atoms. We have found that the low doping efficiency in the case of B is an intrinsic property of amorphous silicon since, even if it is well relaxed, locally strained regions exist [10]. This fact limits the application of amorphous silicon in devices that require higher carrier densities.

References

[1] L. Pelaz, L. A. Marqués, J. Barbolla, J. Appl. Phys., 96 (2004) 5947. [2] R.J. Kaiser et al., Thin Solid Films 518 (2010) 2323 2325. [3] M. Aboy, et al.Computational Electronics, accepted for publication (2014). [4] C. Leroy and P.-G. Rancoita, Rep. Prog. Phys. 70 (2007) 493. [5] G. Lindström, Nucl. Instr. and Meth. A 512 (2003) 30. [6] J. Bao, et al., Optics Express 15 (2007) 6727. [7] L. A. Marqués et al. Phys. Rev. B, 78 (2008) 193201. [8] K. J. Dudeck, L. A. Marqués et al. Phys. Rev. Lett. 110 (2013) 166102. [9] L. A. Marqués et al., J. Appl. Phys. 111 (2012) 034302. [10] I. Santos et al., Phys. Rev. B 81 (2010) 033203.

Figures

Figure 1 - (a) TEM image is compared with (b) the structural model obtained in the simulation to

characterize a planar {113} defect [8].

Figure 2 - (left) TEM image of a FinFET after regrowth (from R. Duffy et al., Appl. Phys. Lett. 190 (2007) 241912), and (right) classical molecular dynamics simulation results showing the line defects observed

in the experiments [9].

Figure 3 Hole spatial localization in B-doped (a, b, c) and undoped (d) 64-atom cells of amorphous Si with different charge states. The dark shadowed areas show the isosurface at 50% of the maximum hole density. B atoms are black and marked by arrows, while Si atoms are white and red. It can be seen that the hole spatial localization in a-Si:B (and therefore the doping efficiency) is highly influenced by the presence locally strained regions (represented by red Si atoms). These strained regions induce around them the spatial localization of holes, independently of the position and concentration of B atoms (a, b, c), and are inherent to the a-Si matrix (d).

Green electrochemical template synthesis of CoPt nanoparticles with tunable size, composition and magnetism from microemulsions using ionic liquids

A. Serrà

1, E. Gómez 1, J.F. López-Barbera 2, J. Nogués 2,3, E. Vallés 1

1 Departament de Química Física and Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, Martí i Franquès 1, 08028, Barcelona, Spain.

2 ICN2 - Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra, Spain. 3 ICREA - Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain.

[email protected]

Abstract

In the last decades, the use of nanomaterials has become a burgeoning topic since given their extraordinary and unusual physical and chemical properties numerous potential applications in catalysis, biological labeling, photonics, optoelectronics, and information storage, among others fields are continuously emerging. It is well known that the composition, crystal phase, size and size distribution of the nanoparticles are key factors that determine their properties 1, 2. However, thermal treatments at high temperatures are often necessary in order to obtain specific crystal phases in nanoalloys. These post-synthesis treatments often affect the particle size, structural properties and particle distribution sizes 3. Therefore, the synthesis of nanoparticles of customized size, composition and shape has long been a scientific and technological challenge.

In this work, a new versatile, environmentally friendly, simple, inexpensive, easily scalable synthesis pathway is presented which combines the potential of the electrodeposition techniques with the possibility of using ionic liquid microemulsions as micro/nanoreactors (Figure 1). Notably, microemulsions are a well-established synthesis procedure to prepare homogeneous and monodisperse small nanoparticles of metals, metal oxides and other inorganic materials 4. Therefore, electrodeposition in combination with microemulsions offers both economic and environmental benefits because it is simple, easily scalable; it implies a low setup cost and avoids the use of aggressive chemical reducing agents 5.

The proposed method allows producing alloyed nanoparticles with sizes ranging from less than 10 nm to over 120 nm and excellent size distribution using different aqueous solution/ionic liquid/surfactant W/IL/S (CoPt aqueous solution/ bmimPF6/ Triton X-100) microemulsions. Importantly, the stoichiometry of the nanoparticles can be directly controlled by the Co/Pt ratio in the nanoreactors. In contrast with water-in-oil microemulsion systems, the higher conductivity of the ionic liquid compared to oil substantially increases the deposition rate when used electrochemically, hence, making the process more attractive for production. We have demonstrated that the magnetic properties of the nanoparticles can be tuned in a straight forward way by adjusting the synthesis conditions. Figure 2 shows that the magnetic response ranges from superparamagnetism (smaller nanoparticles) to hard magnetic (HC = 4100 Oe). Remarkably, these appealing magnetic properties are obtained in the as-grown state (i.e., without post-annealing) as opposed to many other hard magnetic materials. References [1] Ahmadi, T.; Wang, Z.; Green, T.; Henglein, A; El-Sayed, M., Science, 272 (1996), 1924 6. [2] Chithrani, B. D.; Chan, W. C. W., Nano Lett., 7 (2007), 1542 50. [3] Vaccaro, G.; Agnello, S.; Buscarino, G.; Gelardi, F.M., J. Phys. Chem. C., 114 (2010), 13991-7. [4] Santra, S.; Tapec, R.; Theodoropoulou, N.; Dobson, J.; Hebard, A.; Tan, W., Langmuir, 243 (2001), 2900 6. [5] Peng,Y.; Cullins,T.;. Mobus,G.; Xu, X.; Inkson, B., Nanotechno., 18 (2007), 485704-11. Acknowledgment This work was supported by contracts CQT2010-20726 and MAT2010-20616-C02 from MINECO and project 2009-SGR-1292 from the Generalitat de Catalunya. The authors wish to thank the CCiTUB for allowing us to use their equipment. Substrates have been prepared in IMB-CNM (CSIC), supported by the (CSIC) NGG-258 project. A. S would also like to thank the Ministerio de Educación, Cultura y Deporte for its financial support (FPU grant).

Figures

Figure 1: Schematic representation of electrochemical synthesis of magnetic CoPt nanoparticles in W/IL microemulsions.

Figure 2: Magnetic behavior of CoPt alloyed nanoparticles.

Characterization of supramolecular complexes formed between non-steroidal anti-inflammatory

drugs and cucurbit[n]urils adsorbed on silver nanoparticles

Paz Sevilla1,2, Elisa Corda2, Margarita Hernandez2, José V. García-Ramos2, Concepción Domingo2

1Departamento de Química Física II, Facultad de Farmacia, Universidad Complutense de Madrid,

28040 Madrid, Spain. 2Instituto de Estructura de la Materia, CSIC. Serrano 121, 28006 Madrid. Spain.

[email protected]

Abstract Design of new drug delivery systems is nowadays one of the most important topics in research fields. It is necessary that with healthy cells thus optimizing their effectiveness and avoiding secondary effects that are to a large extent undesirable. Nanomedicine has revealed a very useful tool to achieve these goals. Silver nanoparticles have very important optical properties due to the excitation of the localized surface plasmon resonances that have enabled the development of high sensitivity molecular spectroscopies like Surface-Enhanced Raman Scattering (SERS) and Surface-Enhanced Fluorescence (SEF) [1]. They can also serve as vehicle to transport drugs, directly or forming complexes with other molecules, which could be included in multi-step drug delivery systems. Cyclodextrins and calixarenes are synthetic receptors able to form inclusion complexes, but they present several disadvantages associated with their low solubility, except on strongly acid water solutions, ant the difficulty to introduce any functional group. As an alternative in supramolecular chemistry, cucurbiturils constitutes a new family of molecules with important characteristics [2]. They have a highly symmetrical and rigid structure with two identical openings and a hydrophobic defined internal cavity hindered by carbonyl groups which line two rims able to host cationic forms.

Figure 1. Molecular structure of cuburbit[6]uril, cucurbit[7]uril and cucurbit[8]uril In this work we present the characterization of several complexes formed by cucurbiturils and non-steroidal anti-inflamatory (NSAIDs) drugs in solution, as well as adsorbed on colloidal silver nanoparticles, based on our previous experience with the spectroscopic characterization of the drugs alone [3]. Guest molecules used are piroxicam (PX), indomethacin (IM) and ketorolac (KT). All the three molecules present and acid-base equilibrium and, while PX and IM are poorly soluble in water, KT exhibits high solubility. None of these extremes are desirable for the release of the drug. In the case of PX and IM, complexation increases the solubility,and in the case of KT, transportation into the host molecule avoids the loss of effectiveness caused by its binding to other molecules found in their way to diseased tissues. Our results show that PX and IM form complexes with cucurbit[8]uril, while KT does with cucurbit[7]uril. We have used the corresponding adequate spectroscopic techniques for every case: i) UV to obtain the J s plot; 1H NMR, and fluorescence lifetime to detect the presence of complexes and steady-state fluorescence to obtain the binding constant in water solution and ii) SERS and SEF in silver colloids. These studies provide preliminary results necessary to use these complexes in biotechnology and biomedicine.

a) b) c) Figure 2. Molecular structures of a) piroxicam, b) indomethacin and c) ketorolac References

[1] M. Moskovits, Phys. Chem. Chem. Phys. 15 (2013) 5301-5311.

[2] J. Lee, S. Samal, N. Selvapalam, H.-J. Kim, AND K. Kim, Acc. Chem. Res. 36 (2003) 621-63.

[3] P. Sevilla, Hernández, E. Corda, J.V. García-Ramos, C. Domingo, Opt. Pura Apl., 46 (2013) 111-

119.

Theoretical thermal rectification in Si and Ge thin films

E. Chavez-Angel1, 2,*

, F. Alzina1, C. M. Sotomayor Torres1, 3 .

1 Institut Catala de Nanociencia i Nanotecnologia, ICN2, Campus UAB, 08193 Bellaterra (Barcelona), Spain

2 Dept. of Physics, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain. 3 Institucio Catalana de Recerca i Estudis Avançats, ICREA, 08010 Barcelona, Spain.

[email protected]

A deep understanding of heat transport in low-dimensional semiconductor structures is a topic of increasing research activities driven by the need for a more energy conscious society. This is motivated, in part, by the increasing importance of thermal management as a consequence of the large power densities resulting from the continuous miniaturization of electronics components. In this sense, the thermal rectification at nano/microscale is attracting an increasing scientific attention due to its promising potential for thermal management and energy efficiency. Moreover, in analogy with the electrical diode, the thermal rectifier or diode becomes an essential building block of thermal logic circuits. In the present work, the different temperature dependence of the thermal conductivity between two materials is studied for thermal rectification. Four different combinations of silicon and germanium films had been studying. Thermal conductivities are calculated using Fuchs-Sondheimer boundary corrections. The theoretical predictions suggest values of 0.5 to 10 % of efficiency in Si-Si and 0.4 to 12 % in Si-Ge systems [1]. References 1. Chávez-Ángel, E., Alzina, F. and Sotomayor Torres, C.M.

. Heat Transfer.Authors,

Metal incorporation in block copolymer templates

Martin Kreuzer a, Claudia Delgado Simão a, Ana Diaz b and Clivia M. Sotomayor Torres a, c

a Catalan Institute of Nanoscience and Nanotechnology (ICN2), Campus UAB, 08193 Bellaterra, Spain b Paul Scherrer Institute (PSI), 5232 Villigen, Switzerland

c Catalan Institute of Research and Advanced Studies (ICREA), 08010 Barcelona, Spain

[email protected]

Abstract

Metal nanostructures exhibit a wide range of size-dependent properties and variations in fundamental

characteristics, ranging from optical properties [1] to electrical conductivity [2], which can be tuned by

controlling the nanostructure architecture. In order to integrate metal nanostructures in a form suitable

for applications, it is necessary to control the alignment and size of metal nanopaticles on a substrate.

Block copolymer (BCP) templates have attracted much attention for the organization of nanostructures

with high degree of complexity [3-5]. BCPs microphase-separate into ordered structures on a

nanometre scale and are used as templates for metal nanoparticles. However, the interaction between

metal nanoparticles and the BCP templates is poorly understood and is the subject of this paper.

We present a detailed structural analysis of evaporated titanium (Ti) with a nominal layer thickness of

2.5, 5.0, 7.5 nm on underlying BCP templates (Figure 1). The microphase separated BCP surface, with

polyethylene oxide (PEO) cylinders imbedded in a polystyrene (PS) matrix, act as a directing agent for

the evaporated titanium atoms. Using a low evaporation rate, titanium atoms preferentially cover the PS

part of the BCP film (Figure 2). X-ray reflectometry (XRR) measurements revealed that titanium also

accumulates inside the BCP film (Figure 3). Upon further deposition, a continuous titanium layer forms

on the PS matrix, which prevents the further introduction of titanium in the BCP film. We performed

grazing incidence small angle X-ray scattering (GISAXS) synchrotron experiments, which enabled us to

correlate the titanium morphology with the buried polymer structure (Figure 4). We could show that the

titanium layer forms a mesoporous structure with a periodic pore-to-pore distance of 37 nm, resulting

from the underlying PEO cylinder periodicity.

The combination of GISAXS and XRR points out to be crucial for the understanding of how titanium

nanoparticles integrate in PS polymer domains. Our results introduce the concept that titanium

accumulation is not limited to the flat polymer surface, but also includes in the matrix of insulating

polymer bulk material.

The research leading to these results received funding from the Spanish MINECO (project TAPHOR contract nr. MAT2012-31392) and the European Commission FP7 Integrated Infrastructure Initiative No. 262348 European Soft Matter Infrastructure (ESMI). References

[1] Moores, A. and Goettmann, F., New Journal of Chemistry, 30 (2006) 1121; [2] Ploog, K. H., Adv.

Sci. Inst. Ser. B, 294 (1992) 335; [3] C. Simão, A. Francone, D. Borah et al., Journal of Photopolymer

Science and Technology, 25(2012), 239; [4] M. Salaun, M. Zelsmann, S. Archambault et al., Journal of

Materials Chemistry C, 1, (2013) 3544; [5] Haryono, A. and Binder, W. H., Small, 2 (2006) 600

0.0 0.4 0.8 1.2 1.6 2.010

-6

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10-4

10-3

10-2

10-1

100

Inte

ns

ity

[a

.u.]

Qz [nm-1]

Figure 1: Schematic cross section of the sample

preparation. A microphase separated BCP film

(A), forming PEO cylinders in a PS matrix, was

used as a template and coated with Ti by

evaporating nominal 2.5 (B), 5.0 (C) and 7.5 nm

(D) on the template.

Figure 3: X-ray reflectivity data (black dots) of

the sample with nominal 2.5 nm Ti on a BCP

template. A corresponding fit is shown as a red

line.

Figure 2: SEM image of a BCP film after

evaporation of Ti with a nominal layer thickness

of 7.5 nm. The lighter areas represent the PS

block with Ti coating and the darker areas the

PEO block of the microphase separated BCP.

The scale bar corresponds to 500 nm.

Figure 4: 2D GISAXS map of. The diffraction

peaks, indicated by white dashed lines, are the

result of the periodic Ti pore-to-pore distance of

37 nm.

Assessment of molecular effects caused by magnetic hyperthermia in cultured cells and in an invertebrate animal model

Grazyna Stepien1, María Moros1, Alfredo Ambrosone2, Sara Rivera1, Valentina Marchesano2, Angela

Tino2, Claudia Tortiglione2, Jesus M de la Fuente1

1 Instituto de Nanociencia de Aragon, University of Zaragoza. C/ Mariano Esquillor s/n, Zaragoza, Spain 2 Istituto di Cibernetica "E.Caianiello", Consiglio Nazionale delle Ricerche, Via Campi Flegrei, 34, 0078, Pozzuoli, Italy

[email protected]

In recent years, nanoparticle-mediated hyperthermia has been proposed as a valid alternative to conventional thermoablation, which is currently associated to more invasive treatments for cancer therapy. So far, many nanostructured materials with adequate physical properties (optical, electrical, magnetic, thermal) have been synthesized to improve hyperthermia efficiency and targeting [1]. Noteworthy, magnetic nanoparticles (MNPs) have demonstrated superior heating capabilities, striking features for biofunctionalization together with negligible hazard effects in vitro [2,3]. Current research is focused on tuning NP heating properties, enabling controlled hyperthermia in a space and time selective fashion. While most of the studies relies only on in vitro cell culture assays, massive use of animal models with few bioethics restrictions is striving required to bridge from cell research to vertebrates and pre-clinical studies. Herein, we propose a gradual and comparative study performed on the highly metastatic murine melanoma cell line B16-F10 and the freshwater polyp Hydra vulgaris as a novel invertebrate model for reliable screening and validation of nano-heaters properties. In this study, while B16 cells are proposed as an easy model of carcinogenesis in vitro, a further step is the use of animal models. Hydras, whose body organization and the lack of organs allows easy uptake and tracking of any test NPs, may enable immediate evaluation of hyperthermia effect induced upon remote magnetic activation of the NP [5]. B16 cells as well as Hydra animals were incubated with 20nm MNPs synthetized by thermal decomposition [6]. Following NPs internalization (assessed by confocal microscopy), alternant magnetic field was applied to MNP-treated cells/animals. After the thermal treatment potential cell/tissue damages induced by local heating were monitored by a multitude of approaches: i) in vivo through optical microscopy (in case of animals) ii) in vitro on cells using apoptotic/necrosis cell markers (ex vivo on Hydra isolated cells), and iii) at molecular level, by assessment of heat shock gene expression via qRT-PCR. We provided evidences that applying alternant magnetic field does not induce any morphological changes or apoptosis/necrosis damages in case of cells and animals. Instead of that, the elevated expression of heat shock protein hsp70 was observed, showing different expression profiles in animals than in cells. What is more, it was demonstrated that increased hsp70 expression induced by magnetic hyperthermia treatment can be also obtained by incremented incubation temperature. Overall, our results indicate that at the molecular level exists a strong correlation between cells and Hydra animals. In addition, Hydras as a small, easy to handle invertebrates are excellent tools to test nanomaterials before reaching other steps as vertebrate animals. References [1] Chatterjee DK, Diagaradjane P, Krishnan S, Therapeutic Delivery 2(8) (2011) 1001 1014. [2] Laurent S, Dutz S, Häfeli UO, Mahmoudi M, Advances in Colloid and Interface Science 166 (2011) 8 23. [3] Gupta AJ, Gupta M, Biomaterials 26 (2005) 3995 4021. [4] Overwijk WW, Restifo NP, Current Protocols in Immunology 2001 May Chapter 20:Unit 20.1. [5] Galliot B, The International Journal of Develepmental Biology 56 (2012) 407-409. [6] Sun S, Zeng H, Journal of the American Chemical Society 124(28) (2002) 8204-8205.

Figures

Fig.1 Molecular analysis of heat shock protein hsp70 expression after hyperthermia treatment in B16 cells and in Hydras.

An Object Kinetic Monte Carlo comparison of helium retention in nanocrystalline

tungsten and monocrystalline tungsten

G. Valles1, I. Martín-Bragado2, C. González3, O. Peña-Rodríguez1, R. González-Arrabal1, J.M.

Perlado1, A. Rivera1

1Instituto de Fusión Nuclear, ETSI Industriales, Universidad Politécnica de Madrid, C/ José Gutierrez Abascal, 2. 28006 Madrid, Spain

2IMDEA Materials Institute, C/ Eric Kandel 2, 28906 Getafe, Madrid, Spain

3Departamento de Física, Universidad de Oviedo, Spain

[email protected]

Abstract

Tungsten is an excellent candidate for plasma facing components (PFC) in future fusion reactors since it offers several advantages: high melting point, high thermal conductivity, low sputtering coefficient and low tritium retention. However, tungsten will be exposed, among other ions, to helium irradiation. Due to helium insolubility in metals, its implantation inside vacancy-like defects leads to He bubble formation and eventually to detrimental exfoliation of the material. Nanostructured tungsten is nowadays under research because of its large grain boundary density: a high fraction of the incoming helium will be retained inside the grain boundaries. As a result of this behavior, the vacancy defects filled with helium atoms in the interior of the grains in nanocrystalline tungsten are expected to be less pressurized than in case of monocrystalline tungsten.

In this work we present OKMC (Object Kinetic MonteCarlo) simulations of helium (625 keV) pulsed irradiation (1013 cm-2 He/pulse) in both monocrystalline and nanocrystalline tungsten, following the experimental conditions carried out by Renk et al. [1]. The simulator used in this work is MMonCa, a recent developed OKMC code [2]. Nanocrystalline tungsten is formed by columnar grains of 1300 × 50 × 50 nm3. The surrounding grain boundaries are taken as perfect sinks for all defects (vacancies, SIAs, He atoms and their clusters). Comparing both monocrystalline and nanocrystalline tungsten, a clear role of the grain-boundary density in helium retention in the interior of the grain is observed: the higher the density the lower the He retention, that is, the lower the amount of He atoms inside vacancy-like defects. Also can be seen a difference in the He-V defects configuration: our results show that nanocrystalline tungsten exhibits a clear reduction in the number of undesired pressurized He-V clusters as compared to monocrystalline W. The parameterization of MMonCa code for He in W is based on previously published data [3,4] and has been tested comparing to experimental results [5].

References

[1] T.J. Renk, P.P. Provencio, T.J. Tanaka, J.P. Blanchard, C.J. Martin, T.R. Knowles, Fusion Sci. Technol., 61 (2012) 57. [2] I. Martin-Bragado, A. Rivera, G. Valles, J.L. Gomez-Selles, M.J. Caturla, Comput. Phys. Commun. 184 (2013) 2703 [3] C.S. Becquart, C. Domain, U. Sarkar, A. DeBacker, M. Hou, J. Nucl. Mater. 403 (2010) 75. [4] N. Juslin, B.D. Wirth, J. Nucl. Mater. 432 (2013) 61. [5] A. Debelle, P.-E. Lhuillier, M.-F. Barthe, T. Sauvage, P. Desgardin, Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. At. 268 (2010) 223

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Acoustic phonon dynamics in free standing group IV semiconductor membranes studied by ultra-fast pump & probe spectroscopy

M. R. Wagner

1, J. S. Reparaz1, J. Gomis-Bresco1, E. Chávez-Ángel1, B. Graczykowski1, F. Alzina1, and C. M. Sotomayor-Torres1,2

1ICN2 - Institut Catala de Nanociencia i Nanotecnologia,

Campus UAB, 08193 Bellaterra (Barcelona), Spain 2ICREA, Passeig Lluís Companys 23, 08010 Barcelona, Spain

[email protected]

Abstract The ability to control heat and phonon propagation at the nanoscale constitutes a key element for the

physical quantity determining the relaxation time of the thermal field, is still not accurately known for a wide range of technologically relevant materials such as e.g. silicon and germanium. Although some

is no conclusive evidence of its actual magnitude and temperature dependence. Furthermore, the life-time of the thermal field has been only poorly determined and even in the the technologically most relevant case of Si, measurements of phonon lifetimes are scarce [1-3]. In this work, we address these issues by the investigation of the dynamics of low and high energy acoustic phonons using a two femtosecond laser pump and probe technique. The experiment is based on the asynchronous optical sampling method (ASOPS) [4] which compared to standard pump and probe techniques provides a superior signal to noise ratio with a time resolution of about 50 fs (Figure 1). The pump beam locally creates a distribution of non-equilibrium phonons, whereas the probe beam is used to monitor the local temperature through the intensity of the transmitted light. This approach uses the large temperature dependence of the absorption coefficient exhibited by most semiconductors to investigate the decay dynamics of the thermal field. In addition, we report on the lifetime of acoustic phonon modes in Si and Ge free standing membranes as function of heating power and thickness in reflection and transmission geometry (Figure 2). In partic-ular, free standing silicon membranes are model systems for these studies, as they can be fabricated with precisely controlled dimensions and physical parameters, facilitating the comparison with theoreti-cal models. The analysis is free from any effects of a substrate. A reduction of the lifetime of the first order dilation mode in silicon and germanium membranes of up to one order of magnitude is observed with increasing the pump power due to local increase of the phonon population and increased phonon-phonon scattering (Figure 3). References [1] F. Hudert et al., modes in free-standing Si membranes co-herently 79, 201307(R) (2009).

of attenuation of longitudinal acoustic pho-nons in 80, 174112 (2009). [3] J. Cuffe, C. M. Sotomayor Torres, in ultra-thin silicon

110, 095503 (2013). [4] A. Bartels et al., Review of Scientific Instruments 78, 35107 (2007). [5] LaserQuantum gigajet TWIN 20c/20c, technical documentation, http://www.laserquantum.com.

Figures

Figure 1: Schematic illustration of an ASOPS exper-imental setup which employs two actively frequency coupled Ti-Sa lasers with a repetition rate of 1 GHz and a tunable frequency offset of 2-10 kHz to vary the temporal offset between the pump and the probe pulses [5].

Figure 2: Typical time trace of the change in reflec-tivity in a 100 nm thick Si membrane within the first nanosecond after excitation with a 50 fs pump pulse. The initial peak is caused by the electronic response of the semiconductor; the damped oscilla-tions shown in the inset after background correction represent the phonon frequency and decay time of the first order dilatational mode of the Si mem-brane.

Figure 3: Reduction of the acoustic phonon lifetime (D1 mode) as function of pump power (local heat-ing). The excitation power dependent decrease of the acoustic phonon lifetimes are shown for a 100 nm thick Si membrane (upper graph) and a 100 nm thick Ge membrane (lower graph). For low pump powers a constant plateau of the lifetime values is observed in which the effects of local heating are negligible.

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Label-free detection of DNA hybridization and single point mutations in a nano-gap biosensor

Rosa Letizia Zaffino, Mònica Mir, Josep Samitier

Ibec, C/Baldiri I Reixac 10-12 08028, Barcelona, Spain

[email protected]

Abstract We describe a conductance-based biosensor that exploits DNA-mediated long-range electron transport for the label-free and direct electrical detection of DNA hybridization. This biosensor platform comprises an array of vertical nano-gap biosensors made of gold and fabricated through standard photolithography combined with focused ion beam lithography. The nano-gap walls are covalently modified with short, anti-symmetric thiolated DNA probes, which are terminated by 19 bases complementary to both the ends of a target DNA strand. The nano-gaps are separated by a distance of 50nm, which was adjusted to fit the length of the DNA target plus the DNA probes. The hybridization of the target DNA closes the gap circuit in a switch on/off fashion, in such a way that it is readily detected by an increase in the current after nano-gap closure. The nano-biosensor shows high specificity in the discrimination of base-pair mismatching and does not require signal indicators or enhancing molecules. The design of the biosensor platform is applicable for multiplexed detection in a straightforward manner. The platform is well-suited to mass production, point-of-care diagnostics, and wide-scale DNA analysis applications. References [1] R L Zaffino et al 2014 Nanotechnology 25 105501 doi:10.1088/0957-4484/25/10/105501

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