RESEARCH PAPER

Electron beam patterning for writing of positively chargedgold colloidal nanoparticles

Hadar Zafri & Jonathan Azougi & Olga Girshevitz &

Zeev Zalevsky & David Zitoun

Received: 10 September 2017 /Accepted: 12 January 2018# Springer Science+Business Media B.V., part of Springer Nature 2018

Abstract Synthesis at the nanoscale has progressedat a very fast pace during the last decades. The mainchallenge today lies in precise localization toachieve efficient nanofabrication of devices. In thepresent work, we report on a novel method for thepatterning of gold metallic nanoparticles into nano-structures on a silicon-on-insulator (SOI) wafer. Thefabrication makes use of relatively accessible equip-ment, a scanning electron microscope (SEM), andwet chemical synthesis. The electron beam implantselectrons into the insulating material, which furtheranchors the positively charged Au nanoparticles byelectrostatic attraction. The novel fabrication methodwas applied to several substrates useful in micro-electronics to add plasmonic particles. The resolu-tion and surface density of the deposition weretuned, respectively, by the electron energy (acceler-ation voltage) and the dose of electronic irradiation.We easily achieved the smallest written feature of68 ± 18 nm on SOI, and the technique can be

extended to any positively charged nanoparticles,while the resolution is in principle limited by theparticle size distribution and the scattering of theelectrons in the substrate.

Keywords Microfabrication . Patterning . Electronbeam . Colloids . Nanoparticle . Gold . Self-assembly .

Surface potential . Nanoscale patterns

Introduction

In recent years, there has been outstanding progressin the development of lithography techniques for thefabrication of nanosized objects (Vitor et al. 2013).An alternative approach for device fabrication usesnanoparticles (NPs) as the material of choice for thedevice fabrication (Limon et al. 2009; Shahmoonet al. 2010a). NPs are widely used in a large varietyof nanodevices such as single nanoparticle-basedelectronic transistors (Junno et al. 1999; Shahmoonet al. 2010b), electro-optical modulators (Limon et al.2009), diodes (Yoshida et al. 1998), and logic circuits(Korotkov 1995). Their synthesis, conjugation, andassembly are now well known, making them poten-tially inexpensive and easy to produce. Another rea-son that NPs attract broad interest is related to theirsize, which is now close to the resolution limit ofpatterning techniques. Additional important proper-ties are their photo- and chemical stability. The phys-ical and chemical properties of NPs depend upontheir size, shape, aspect ratio, internal and external

J Nanopart Res (2018) 20:34 https://doi.org/10.1007/s11051-018-4129-2

H. Zafri :D. Zitoun (*)Department of Chemistry, Bar-Ilan University, 5290002 RamatGan, Israele-mail: David.Zitoun@biu.ac.il

H. Zafri : J. Azougi : Z. Zalevsky (*)Faculty of Engineering, Bar-Ilan University, 5290002 Ramat Gan,Israele-mail: zeev.zalevsky@biu.ac.il

H. Zafri :O. Girshevitz : Z. Zalevsky :D. ZitounBar Ilan Institute of Nanotechnology and Advanced Materials,Bar-Ilan University, 5290002 Ramat Gan, Israel

chemistry, and dielectric constant (Eustis and el-Sayed 2006), which can bring new features to thedevice. In order to fabricate a device, one needs toreproducibly synthesize the NPs on the device, or tocontrol the organization of NPs within a large areainside the device, and thus, high-resolution tech-niques are required.

A few methods based on electrostatic interactionshave been proposed in order to deposit and organizeNPs on surfaces, mainly Si wafers or glass slides.One major advance is based on the concept of scan-ning force microscopy, where the conductive tipinduces a local charge on the substrate, which elec-trostatically attracts the charged NPs. Such a tech-nique allows nanoscale patterning on the substrateon a rather small scale (Mesquida and Stemmer2002; Mesquida and Stemmer 2001; Naujoks andStemmer 2003).

Layer-by-layer (LBL) assembly is an additional tech-nique based on electrostatic interactions between layersof oppositely charged NPs and polyelectrolytes. Thistechnique is usually achieved by the sequential deposi-tion of positively charged polyelectrolytes and negative-ly charged NPs (Liu et al. 1997; Caruso et al. 1998;Correa-Duarte et al. 1998; Rosidian et al. 1998; Storhoffet al. 1998; Aliev et al. 1999; Jacobs et al. 2002; Tsaiet al. 2005; Srivastava and Kotov 2008) to form thinfilms with nanoscale resolution in the z-axis. The in-plane resolution can only be achieved by using lithog-raphy before LBL deposition in order to write the de-signed pattern. Such a technique can be used for a singleNP layer, and by sequential deposition, it can be extend-ed to multiple layers. As an example, anionic NPs(negatively charged) can be deposited onto a layerof poly-L-lysine, a cationic organic homo-polymer(Jacobs et al. 2002; Tsai et al. 2005). This techniquehas gained vast interest, as it can also be applied tooppositely charged NPs (cationic and anionic) toform super-lattices where each layer is composed ofalternative sub-layers of cationic and anionic NPs(Walker et al. 2011).

A very recent technique, developed in the labora-tory, makes use of a focused ion beam (FIB), whichimplants cations (for instance of gallium, Gan+) inthe substrate during exposure to the ion beam(Shahmoon et al. 2010a, b). This technique has beenapplied for patterning Au-NPs with applications inthe field of nanophotonics. HF-modified Au-NPs canself-assemble in arrays with a pitch using a 30 keV

Ga+ beam (Kolíbal et al. 2012). Writing with FIB is astraightforward process. However, the FIB is onlysuitable for negatively charged NPs as the beam iscomposed of cations. The FIB is also very expensiveand has limited accessibility, limiting the applicability ofthis technique to large research and developmentcenters.

While effective, all methods described abovehave constraints in terms of limitation to specificpairs of substrates/NPs, duration of the process,complexity, and cost. In order to improve the per-formance, we propose to investigate a novel methodof self-assembly via deposition of NPs at specificareas within the substrate, on which the designeddevice is to be realized. The self-assembly conceptthat we report here is based on electrostatic interac-tions of electrons implanted in dielectric substratesand positively charged NPs. The technique is verysimilar to the ion implant technique but with anopposite charge for the NPs. This technique is inno-vative since it relies on the use of an electron beam,which is far more common than an ion beam. Elec-tron beams can be found in scanning electron mi-croscopy (SEM), transmission electron microscopy(TEM), and electron beam lithography.

Experimental section

Materials and methods

Synthesis of gold nanoparticles (Au-NPs) Hydrogentetrachloroaurate (III) hydrate, 99.999% metal basis,cysteamine hydrochloride 99%, and sodium borohy-dride (Sigma-Aldrich) were used as received. Au-NPs were synthesized using NaBH4 as a reductionagent and reduced HAuCl4 in the presence of cyste-amine (Niidome et al. 2004; Jv et al. 2010; Cao andLi 2011; Zheng et al. 2013). A cysteamine solution(0.213 M, 0.4 mL) was added to a 1.4 mM HAuCl4solution in 40 ml of distilled water under vigorousstirring. The solution was then stirred for 20 min inan ice bath in the dark. Ten microliters of a freshsolution of 0.02 M NaBH4 were added quickly tothe Au solution and stirred for 30 min. The color ofthe solution changed gradually from brownish to aclear red-wine color. After washing, the solution wasstored at − 4 °C. Silicon-on-insulator (SOI) was

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donated by SOITEC and consists in a 70-nm Silayer on a 2-μm SiO2 box.

Characterization

High-resolution scanning electron microscope (FEI,Magellan 400L) was used for the electron beam (e-beam) lithography process. The images were takenunder special conditions to prevent implantation ofadditional electrons. The spot beam was 3 nm, andthe voltage was 5 kV. In addition, the images wereacquired with a very short exposure time. SEMimages were collected on an E-SEM (QuantaFEG, FEI).

Dynamic light scattering was measured on aSympatek Nanophox instrument with a He-Ne laser(l = 632.8 nm) based on photon cross-correlationspectroscopy (PCCS) in order to avoid multiple scat-tering. The scattering angle was set to 90°, the tem-perature was 25 °C, and the measurements wererepeated three times at two different concentrations.Hydrodynamic average diameters and polydispersitywere calculated from the non-negative least-squarefitting of the autocorrelation curve using the Stokes-Einstein equation. Zeta potential measurements werecollected on a Zetasizer Nano (Malvern Instrument).

Atomic force microscopy (AFM) measurementswere performed after the substrate irradiation, beforeand after the deposition of the NPs. All AFM mea-surements were carried out in ambient conditionsusing a Dimension ICON (Bruker AXS, SantaBarbara, CA). A conducting cantilever probe (rect-angular, platinum–iridium coated, SCM-PIT probe,Bruker, CA, USA), with force constant of 4 N/mand resonance frequency of 45–100 kHz, wasmounted in a tip holder capable of controlling thevoltage applied to the tip. We used the lift-modeKelvin probe force microscopy (KPFM) system(Park et al. 2011) based on dual-line scan imaging,where a lift height of 30 nm was used to avoidinterference from the topography. The topographyheight images were recorded simultaneously withtapping phase and surface potential maps, whichwere compiled from the amplitude-modulated(AM)-KPFM measurements. The images were cap-tured at an image resolution of 512 samples/line witha 1:1 aspect ratio. Nanoscope Analysis Software wasused for analysis of the images. Focused ion beam(Helios 600, FEI) was used to implant Ga+ ion.

Results and discussion

Colloidal synthesis

In this work, we apply this novel e-beam method to thedeposition of Au-NPs at specific areas within the device,which could enable mass production. Using an electronbeam, at a specific voltage and current, electrons areimplanted on the surface of an insulating or semi-conducting substrate in a specific spatial pattern thatfollows the structure of the nanodevice to be fabricated.This pattern is used as a platform for the electrostaticadhesion of positively charged NPs through a simplegeneric process. The substrates used in our experimentsare SOI. Positively charged spherical Au-NPs weresynthesized and displayed positive zeta potentials.

Positively charged Au-NPs were synthesized in aone-step reaction (Fig. 1a). The ligand, cysteamine,plays the dual role of reducing agent and stabilizingagent, with the thiol as the anchoring agent on the Au-NP surface and the ammonium providing the electro-static repulsion between the NPs in water dispersion atneutral pH. The surface charge was measured by zeta-potential and reaches + 35 mV, resulting from the cat-ionic ammonium of the cysteamine for a pH above thepKa, and the absolute value is large enough to stabilizethe NPs by electrostatic repulsion for months. The sizedistribution was centered around 33 ± 5 nm. Figure 1bdisplays the deposition steps using this colloidal ink.The electron beam exposure is followed by depositionof Au-NPs by drop-casting on the substrate, washing outthe non-specifically attached particles with deionizedwater, and nitrogen drying.

Electron beam patterning

Several patterns were written by electron beam irradia-tion followed by SEM imaging to validate the self-assembly process. The letter BZ^ was written in orderto investigate whether the Au-NP specifically binds tothe SOI and maintains the original template shape.Figure 2a shows the SEM imaging of the Au-NP as-sembled to form the letter Z.

In order to determine the thinnest line that can bewritten by deposition of Au-NPs, we irradiated the SOIwafer with different voltages and durations. Figure 2bdisplays a line of NPs after electron beam writing at anacceleration voltage of V = 10 kV, a current of I =22 nA, and an exposure time of t = 16 s. These

J Nanopart Res (2018) 20:34 Page 3 of 10 34

parameters result in a dose of electrons per surface unitof 26.4 nC/μm2. The SOI is electron-implanted follow-ing a 100 μm long and 100 nm wide line. After Au NPdeposition, the width of the line is on average 68 ±18 nm, very close to the initial width. The Au NP lineis not perfectly continuous and straight; the NPs deviatesfrom the original line of about 58 ± 16 nm. Interestingly,the values obtained for the line width and standarddeviation are only two times larger than the Au NPmean particle size.

In order to evaluate the resolution limit of the writingprocess, the SOI was irradiated with a pattern of threeparallel lines 120 μm long and 50 nm wide; the distancebetween two adjacent lines in the template was 700 nm.

The irradiation dose (37.12 nC/μm2) was similar to theprevious experiments with the same voltage and current.Figure 2c shows the deposition of the NPs on the tem-plate; the three lines are clearly separated, but the spac-ing between the lines is diminished, from 700 to275 nm. This phenomenon is due to the following threereasons: (1) the NP size limits the resolution; (2) subse-quent electrons are rejected by the electrons that arealready implanted on the surface, resulting in the ob-served scattering; and (3) the potential is a function ofspace; therefore, the irradiated area has the highest po-tential, and the area surrounding it shows a potentialdecay. The NPs slightly bind also to the surroundings,which causes a slight blurring of the deposited lines.

Fig. 1 Schemes of a cationic Aucolloid (a) and of an electronbeam induced writing of cationicnanoparticles on SOI (b)

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Independent of the particle size distribution, a resolutionimprovement can be expected from fine-tuning of theirradiation parameters, mainly the electron kinetic ener-gy through the acceleration voltage and the dose ofelectrons, through the current and exposure time. Thesetwo parameters are explored in the following section.

Resolution of the process

The same deposition of Au-NPs was observed for dif-ferent acceleration voltages of the electron beam. The

pattern was irradiated with different energies over thesame duration. As a result of changing the energy, thedose was adjusted to fit the other parameters. Depositionof Au-NPs on SOI wafer was carried out by irradiationwith an electron beam at acceleration voltages between5 and 20 kV (Fig. 3a–d). For each sample, we added theoriginal Z pattern as a guideline for estimating thedistortion of the pattern at each electron beam accelera-tion voltage.

One can notice that, for high electron beam acceler-ation voltage (20 kV), the resolution is increased and the

Fig. 2 SEM images afterdeposition of Au-NPs on SOIwafer on the templated letter Z(a), on a 100 nm wide line (b),and on parallel lines 120 μm longand 50 nm wide with a distancebetween two adjacent lines in thetemplate of 700 nm (c)

Fig. 3 Colored SEM images ofthe deposition of Au-NPs on SOIfor different electron beamacceleration voltages (5, 10, 15,and 20 kV, a–d, respectively)

J Nanopart Res (2018) 20:34 Page 5 of 10 34

contrast is decreased. In other words, the pattern is betterretained for high electron beam energy, but non-specificbinding also increases.

To confirm this qualitative trend, an electron-penetration profile was modeled by a Monte-Carlo ap-proach according to the actual parameters; the simula-tion result is displayed in Fig. 4a, b. Figure 4a describesthe electron penetration profile in 2000 nm SiO2 usingan electron acceleration voltage of 10 kV. Figure 4bdescribes the electron-penetration profile in 2000 nmSiO2 using an electron acceleration voltage of 30 kV,while all other parameters were kept constant. When ahigh voltage is applied, the electrons penetrate the SiO2

surface and reach underneath the Si substrate, while atlow voltage, the electrons remain in the SiO2 box and donot reach the substrate.

This trend can be understood from known consider-ations of electron-matter interactions. The beam of elec-trons interacts with the substrate, and the electrons arescattered in a shape that resembles an onion. By increas-ing the acceleration voltage, the electron scattering oc-curs in a deeper layer, as shown in Fig. 4a, b. At higherelectron energy, there is less interaction with the SOIsurface. Furthermore, at higher voltage, the diameter ofthe electron beam is smaller. Writing at higher voltage istherefore more accurate.

On the other hand, the grafting process of Au-NPs isless effective, since the electrostatic force is decreasedfollowing Coulomb’s law. At lower acceleration volt-age, the resolution is decreased because the Bonion^ iscloser to the surface layer, which blurs the originaltemplate. In addition, the electrons diffuse to the SiO2

Fig. 4 Simulated electron-penetration profiles in SOI at 10 kV (a) and 30 kV (b). The mean penetration depths of the electron beam in SOIwere obtained using the Kanaya-Okayama model (c) (Lyman et al. 1990)

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box layer. As a result, the Z shape becomes broader.Moreover, at low acceleration voltage, the diameter ofthe electron beam is increased.

Another approach to estimate the penetration depthof the electrons can be made through the Anderson andHasler model (Lyman et al. 1990):

ZD ¼ 64E1:680

ρ; ð1Þ

where ZD is the penetration depth, E0 is the energy(keV), and ρ is the layer density. The electron energywas set between 5 and 20 keV for each set of experi-ments, and the layer density can be roughly estimated tobe 2200 kg/m3 considering an amorphous silica layer orsilicon layer (same density for both). The obtained pen-etration depth is then 1.4 μm for 10 kV. Figure 4c

displays the maximum penetration depth of the electronbeam as a function of energy (accelerating voltage). Theblue curve provides the resulting penetration depth foreach accelerating voltage (typically 5, 10, 15, or 20 kV).The thickness of each layer of the SOI was added as aguideline to roughly determine the layer in which theelectrons are mainly implanted. The two models areconsistent with implantation of electrons mainly in theSiO2 box for low voltage (5–10 kV) and in the substratefor high voltage (10–20 kV).

Smoothness of the colloidal film

The deposition technique depends also on the electrondose set to irradiate the pattern. To investigate its influ-ence on the deposition process, the surface was scannedby AFM after NP deposition. Figure 5a, b displays the

Fig. 5 AFM topography imagesof a 10 × 10 μm2 areadeposition (scale bar 1 μm) andthe respective profile of thecross section for the lowelectron dose (27.79 nC/μm2)(a, b) and high electron dose(59.09 nC/μm2) (c, d)

J Nanopart Res (2018) 20:34 Page 7 of 10 34

electron beam irradiation on SOI with a dose of27.79 nC/μm2. Figure 5c, d displays the resulting depo-sition with about twice the electron dose (59.09 nC/μm2). The dose increases linearly with the exposuretime. A larger dose leads to a higher density of the Au-NPs grafted to the SOI. The value of the root-meansquare (RMS) decreases from 4.0 to 1.7 nm for asmoother Au layer, indicating that the Au-NPs are betterpacked at a higher electron dose, with a more effectiveassembly process.

Controlled experiments

The influence of the acceleration voltage and the elec-tron dose demonstrates that the charge accumulation inthe SOI box leads to specific binding of the positivelycharged colloids on the template. To directly assess themechanism, we carried out a KPFM measurement onthe SOI after electron beam exposure.

The irradiation was performed in a SEM which im-plants the SOI wafer. We carried out the topography(AFM) and potential mapping (KPFM) on the followingday. Figure 6a displays the surface potential measuredwith KPFM; the potential difference between the irradi-ated and non-irradiated areas is − 63.4 mVon average,

which is consistent with the accumulation of electronseven after 1 day. As a reminder, the colloidal Au NPsdisplay a zeta potential of + 35 mV.

Figure 6b displays the surface topography of the SOI.The electron beam etches 7.3 nm of the surface, insig-nificantly altering the topography of the surface. How-ever, such a small difference cannot explain the specificbinding of the colloids with a diameter 4–5 times larger.In addition, the SOI wafer was stored in a desiccator for8 days after the patterning was measured in KPFM, inorder to test the decay time of the electron implantation.We could still measure a difference of potentials, albeitlower, about − 14 mV. The electrons trapped on thesubstrate had thus diffused to the surroundings with time.

To further confirm the electrostatic mechanism, weimplanted positive Ga ions with a focused ion beam.The SOI wafer was irradiated with Ga+ ion beam at twodifferent acceleration voltages (5 and 30 kV), and theresulting template was exposed to the positively chargedAu colloids and washed to remove the non-specificallybound Au colloids (Fig. 6c, d). At low voltage, the FIBpattern does not show any preferential interaction withthe colloids (Fig. 6c). At high voltage, the ion beametches the surface and implants positive Ga ions whichelectrostatically repulse the positively charged NPs

Fig. 6 Surface potential andsurface topography of anelectron beam irradiated SOI(a, b). SEM images of thewafer after Au deposition onsamples irradiated with Ga+

ions at 5 and 30 kV (c, d)

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(Fig. 6d). Interestingly, this experiment also confirmsthat the etching process cannot explain the specificbinding of the colloids and that electrostatic interactionsare the driving force for the writing process.

Conclusion

We have reported on a novel method for placing Aucolloids on an SOI wafer. Electron beam implants elec-trons into the insulating material, which further anchorsthe positively charged Au nanoparticles by electrostaticattraction. The acceleration voltage must be tuned sothat the average electron penetration depth lies withinthe SOI box (the insulator layer). The acceleration volt-age and the electron dose respectively enhance the res-olution and smoothness of the Au colloidal deposition.The smallest written feature can reach 68 ± 18 nm onSOI. Kelvin probe measurements demonstrate the va-lidity of the electrostatic model at work for the specificbinding of the colloids. This patterning technique canbe extended to any positively charged nanoparticles,while the resolution is in principle limited by theparticle size distribution and the scattering of theelectrons in the substrate.

Acknowledgments The authors thank Shlomi Polani for hishelp with the guidance on the synthesis of Au nanoparticles.

Author contributions Themanuscript was written through con-tributions of all authors. All authors have given approval to thefinal version of the manuscript.

Funding sources This work was supported by the Israeli Min-istry of Science, Technology and Space.

Compliance with ethical standards

Conflict of interest The authors declare that they have no con-flict of interest.

References

Aliev FG, Correa-Duarte MA, Mamedov A, Ostrander JW,Giersig M, Liz-Marzán LM, Kotov NA (1999) Layer-by-layer assembly of core-shell magnetic nanoparticles: effectof silica coating on interparticle interactions and magneticproperties. Adv Mater 11(12):1006–1010. https://doi.org/10.1002/(SICI)1521-4095(199908)11:12<1006::AID-ADMA1006>3.0.CO;2-2

Cao R, Li B (2011) A simple and sensitive method for visualdetection of heparin using positively-charged gold nanopar-ticles as colorimetric probes. Chem Commun 47(10):2865–2867. https://doi.org/10.1039/c0cc05094f

Caruso F, Lichtenfeld H, Giersig M et al (1998) Electrostatic self-assembly of silica nanoparticle - polyelectrolyte multilayerson polystyrene latex particles. J Am Chem Soc 7863:8523–8524

Correa-Duarte MA, Giersig M, Kotov NA, Liz-Marzán LM(1998) Control of packing order of self-assembled mono-layers of magnetite nanoparticles with and without SiO2coating by microwave irradiation. Langmuir 14(22):6430–6435. https://doi.org/10.1021/la9805342

Eustis S, el-Sayed MA (2006) Why gold nanoparticles are moreprecious than pretty gold: noble metal surface plasmon reso-nance and its enhancement of the radiative and nonradiativeproperties of nanocrystals of different shapes. Chem Soc Rev35(3):209–217. https://doi.org/10.1039/B514191E

Jacobs HO, Campbell SA, Steward MG (2002) ApproachingNanoxerography: the use of electrostatic forces to positionnanoparticles with 100 nm scale resolution. Adv Mater14(21):1553–1557. https://doi.org/10.1002/1521-4095(20021104)14:21<1553::AID-ADMA1553>3.0.CO;2-9

Junno T, Magnusson MH, Carlsson S-B, Deppert K, Malm JO,Montelius L, Samuelson L (1999) Single-electron devices viacontrolled assembly of designed nanopart icles .Microelectron Eng 47(1-4):179–183. https://doi.org/10.1016/S0167-9317(99)00184-7

Jv Y, Li B, Cao R (2010) Positively-charged gold nanoparticles asperoxidase mimic and their application in hydrogen peroxideand glucose detection. Chem Commun (Camb) 46:8017–8019

Kolíbal M, Konečný M, Ligmajer F et al (2012) Guided assemblyof gold colloidal nanoparticles on silicon substrates pre-patterned by charged particle beams. ACS Nano 6:10098–10106

Korotkov AN (1995) Wireless single-electron logic biased byalternating electric field. Appl Phys Lett 67(16):2412–2414.https://doi.org/10.1063/1.114564

Limon O, Businaro L, Gerardino A et al (2009) Fabrication ofelectro optical nano modulator on silicon chip. MicroelectronEng 86:1099–1102

Liu Y,Wang A, Claus RO (1997) Layer-by-layer electrostatic self-assembly of nanoscale Fe3O4 particles and polyimide pre-cursor on silicon and silica surfaces. Appl Phys Lett 71:2265

Lyman CE, Newbury DE, Goldstein JI, Al E (1990) Scanningelectron microscopy, X-Ray Analysis and AnalyticalElectron Microscopy

Mesquida P, Stemmer A (2002) Maskless nanofabrication usingthe electrostatic attachment of gold particles to electricallypatterned surfaces. Microelectron Eng 61–62:671–674

Mesquida P, Stemmer A (2001) Attaching silica nanoparticlesfrom suspension onto surface charge patterns generated bya conductive atomic force microscope tip. Adv Mater 13:1395–1398 -ADMA1395>3.0.CO;2-0

Naujoks N, Stemmer A (2003) L ocalized functionalization ofsurfaces with molecules from solution using electrostaticattraction. Microelectron Eng 67–68:736–741

Niidome T, Nakashima K, Takahashi H, Niidome Y (2004)Preparation of primary amine-modified gold nanoparticlesand their transfection ability into cultivated cells ChemCommun 1978–9

J Nanopart Res (2018) 20:34 Page 9 of 10 34

Park J, Yang J, Lee G et al (2011) Single-molecule recognition ofbiomolecular interaction via kelvin probe force microscopy.ACS Nano:6981–6990

Rosidian BA, Liu Y, Claus RO (1998) Ionic self-assembly ofultrahard ZrO2 / polymer nanocomposite thin films. AdvMater 356:1087–1091

Shahmoon A, Limon O, Girshevitz O et al (2010a) Tunable nanodevices fabricated by controlled deposition of gold nanopar-ticles via focused ion beam.Microelectron Eng 87:1363–1366

Shahmoon A, Limon O, Girshevitz O, Zalevsky Z (2010b) Selfassembly of nano metric metallic particles for realization ofphotonic and electronic nano transistors. Int J Mol Sci 11:2241–52. d

Srivastava S, Kotov NA (2008) Composite layer-by-layer (LBL)assembly with inorganic nanoparticles and nanowires. AccChem Res 41(12):1831–1841. https://doi.org/10.1021/ar8001377

Storhoff J, Elghanian R, Mucic RC et al (1998) One-pot colori-metric differentiation of polynucleotides with single base

imperfections using gold nanoparticle probes. J Am ChemSoc 7863:1959–1964

Tsai D-H, Kim SH, Corrigan TD, Phaneuf RJ, Zachariah MR(2005) Electrostatic-directed deposition of nanoparticles ona field generating substrate. Nanotechnology 16(9):1856–1862. d. https://doi.org/10.1088/0957-4484/16/9/073

Vitor R, Zhang L, Su D et al (2013) Resolution limits of electron-beam lithography toward the atomic scale. Nano Lett 13:1555–1558

Walker DA, Kowalczyk B, de la Cruz MO, Grzybowski BA(2011) Electrostatics at the nanoscale. Nano 3:1316–1344

Yoshida T, Yamada Y, Orii T (1998) Electroluminescence ofsilicon nanocrystallites prepared by pulsed laser ablation inreduced pressure inert gas. J Appl Phys 83:5427

Zheng J, Zhang H, Qu J, Zhu Q, Chen X (2013) Visual detectionof glyphosate in environmental water samples usingcysteamine-stabilized gold nanoparticles as colorimetricprobe. Anal Methods 5(4):917–924. https://doi.org/10.1039/C2AY26391B

34 Page 10 of 10 J Nanopart Res (2018) 20:34