Microporous and Mesoporous Materials 156 (2012) 121–126

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Microporous and Mesoporous Materials

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Soft-templating synthesis of ordered mesoporous carbons in the presenceof tetraethyl orthosilicate and silver salt

Laura Sterk a, Joanna Górka a,1, Ajayan Vinu b,c, Mietek Jaroniec a,⇑a Department of Chemistry, Kent State University, Kent, OH 44240, USAb International Center for Materials Nanoarchitectonics, WPI Research Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305 0044, Japanc Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, #75 Corner Cooper and College Road, Brisbane 4072, QLD, Australia

a r t i c l e i n f o

Article history:Received 21 December 2011Received in revised form 14 February 2012Accepted 15 February 2012Available online 24 February 2012

Keywords:Mesoporous carbonsNitrogen adsorptionSilver nanoparticlesSoft-templating synthesis

1387-1811/$ - see front matter � 2012 Elsevier Inc. Ahttp://dx.doi.org/10.1016/j.micromeso.2012.02.028

⇑ Corresponding author. Tel.: +1 330 672 3790; faxE-mail address: jaroniec@kent.edu (M. Jaroniec).

1 Present address: Oak Ridge National Laboratory,Nanomaterials Chemistry Group, 1 Bethel Valley RoadRidge, TN 37831-6201, USA.

a b s t r a c t

Soft-templating synthesis of ordered mesoporous carbons (OMCs) in the presence of tetraethyl orthosil-icate (TEOS) and silver nitrate was carried out in order to introduce silver nanoparticles and to createadditional microporosity in these materials. This strategy was employed to obtain the phenolic resin-based OMCs with two different loadings of silver. Also, this approach was used to obtain silver-containingmesoporous carbon–silica hybrids, which after dissolving silica with NaOH solution gave microporous–mesoporous carbons with Ag particles. Nitrogen adsorption, small and wide angle X-ray diffraction,transmission electron microscopy and thermogravimetric analysis showed good adsorption and struc-tural properties of the aforementioned OMC materials.

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1. Introduction

Carbon-based materials are commonly used in industrial appli-cations because of their low cost and commercial availability. Forinstance, activated carbons are produced at very low cost for vari-ous applications ranging from adsorption, catalysis, purificationand separation processes to capacitors; they have high surfaceareas due to the presence of micropores (pore widths below2 nm) but broad pore size distributions and disordered porosity.Thus, these materials have several shortcomings: slow mass trans-port due to complex microporosity, low conductivity due to surfacegroups and defects, and tendency for pore structure collapse uponhigh temperature heating under neutral atmosphere (graphitiza-tion) [1]. In the late 1990s, nanocasting strategy, often referred toas hard-templating named because of using sacrificial siliceoustemplates, yielded first carbons with ordered and tunable porousstructures [2–4]. Even though the hard-templating became verypopular way to produce mesoporous carbons, it is consideredunfeasible because of high cost, laborious process and environmen-tal risk associated with using HF or NaOH for the removal of sili-ceous templates. In 2006, the soft-templating strategy wasdeveloped on the basis of organic–organic self-assembly of block

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copolymers (soft templates) and polymeric-type carbon precursors[5–9]. This one-pot synthesis affords carbons possessing high sur-face areas and large mesopores with narrow pore size distributions.

Nanoporous carbons because of their high stability in acidic andbasic media are attractive supports for the development of variouscatalysts. Chen et al. [10] reported the preparation of silver–carbonmesoporous materials as catalysts for fuel cell applications. Prefer-ential oxidation of CO to CO2 inhibits the poisoning effect of CO onthe fuel cell catalyst. Using carbon as a support allows for a moreefficient single stage cell configuration due to the conductive prop-erties of carbon. Also, silver is an inexpensive alternative to its pre-cious metal congeners, which is an important feature, related tothe common effort to replace the use of Pt-based catalysts withthose containing semi-precious metals.

Other possible applications of silver-containing carbons arebased on silver antibacterial properties and include materials usedfor water purification and treatment [11–14]. Although not fullyunderstood, silver species inhibit the replication of the bacteriaand yeast fungus such as Escherichia coli, Staphylococcus aureusand Candida albicans making silver-containing materials ideal forsuch as applications as a water treatment [13]. Interestingly, thestrongest antibacterial activity was exhibited by carbons justdoped with silver [14]. Another work reported that the silver-loaded carbons exhibit much higher adsorption towards metal-cyanide complexes from aqueous solutions than activated carbonsalone [15].

The commonly used method for silver loading is a simpleimpregnation of amorphous carbon powders, graphitic fibers or

122 L. Sterk et al. / Microporous and Mesoporous Materials 156 (2012) 121–126

monoliths with silver salts [12,16–19]. An interesting synthesisroute towards the preparation of high surface area and high porevolume carbons with silver nanoparticles was reported by Jaroniecet al. [20]. In this case, silica colloids used as a hard template werepressed with silver nanoparticles together to form a monolith. Theimpregnation of the latter with a phenolic resin-type carbon pre-cursor and subsequent carbonization and silica removal led tothe final mesoporous carbons with silver nanoparticles. The advan-tage of this synthesis route is the possibility to precisely control thesize of mesopores formed and the size of silver nanoparticlesembedded in the carbon framework [21].

Here we report the synthesis of ordered mesoporous carbons(OMCs) with embedded silver nanoparticles by self-assembly of atriblock copolymer and phenolic resin precursors in the presenceof AgNO3. Also, the reaction mixture was supplied with tetraethylorthosilicate (TEOS) in order to improve microporosity and specificsurface area of the final materials. The whole synthesis procedurewas analogous to that demonstrated earlier for the preparation ofnickel-containing carbons [22] in order to determine the effect ofmetal salt on the mesostructure formation.

2. Materials and methods

2.1. Chemicals

Poly(ethylene oxide)-poly(propylene oxide)-poly(ethyleneoxide) triblock copolymer (EO106PO70EO106; Pluronic F127) was pro-vided by BASF Corp. Resorcinol, (C6O2H6; 98%), formaldehyde(HCHO; 37%), silver nitrate (AgNO3; 99%) and tetraethyl orthosili-cate (TEOS, 98%) were purchased from Arcos Organics. HCl (35–38%) was acquired from Fischer and ethanol from Pharmco.

2.2. Materials

The carbon samples studied were synthesized by using aslightly modified recipe reported by Wang et al. [23]. Initially,1.25 g of Pluronic F127 block copolymer, 1.25 g of resorcinol andthe specified amount of AgNO3, (1 or 2 mmol) were dissolved inwater/ethanol solution; the weight ratio of water to ethanol was5.5:10. After a complete dissolution 1.1 ml of HCl was added undercontinuous stirring for another 30 min. Then 1.25 ml of formalde-hyde was introduced to the reaction mixture and stirred until mix-ture turned milky. Additional 30 min of stirring was applied toensure the phenolic resin formation. At this time, the mixing wasstopped and the solutions remained undisturbed until a phase sep-aration took place. The upper phase, which consisted mostly ofethanol and water, was removed and the lower phase was trans-ferred onto a Pyrex dish to evaporate the solvent for 16 h underambient conditions followed by aging at 100 �C for 24 h. In the caseof SiO2-containing samples, TEOS in the amounts of 40 and 60 wt.%with respect to the carbon precursor were added about 30 minafter formaldehyde addition.

A tube furnace was used to carbonize the resulting samples un-der nitrogen atmosphere with the heating rate of 2 �C /min up to180 �C and keeping at the target temperature for 5 h, resumingheating with the same rate up to 400 �C and with 5 �C/min up to800 �C followed by keeping them at 800 �C for 2 h. In order to re-move silica, samples were soaked with 3% sodium hydroxide(10 ml per gram of the sample) and kept at 70 �C for 16 h followedby washing with DI water.

The final samples were denoted according to the formula: M-xAgyT, where M stands for the type of material (CS = carbon–silicacomposite, C = carbon), x indicates the amount of silver salt added(1 or 2 mM) and y refers to wt.% of TEOS (T) in the sample.

2.3. Measurements

Nitrogen adsorption isotherms were measured at �196 �C onASAP 2020 volumetric analyzer (Micromeritics, Inc., GA). Sampleswere outgassed at 200 �C for 2 h prior to adsorptionmeasurements.

Wide angle X-ray diffraction analysis was performed on PANa-lytical X’Pert PRO MPD X-ray diffraction system using Cu Ka radi-ation (40 kV, 40 mA). All patterns were recorded using 0.02� stepsize and 4 s per step in the range of 15� 6 2h 6 80�. Small angleXRD data were measured in the range of 0.4� 6 2h 6 5�.

Thermogravimetric analysis was performed on a TA InstrumentHi-Res TGA 2950 thermogravimetric analyzer from 30 to 800 �Cunder air flow with a heating rate of 10 �C/min.

TEM images of the samples were taken on a Hitachi HD-2000Scanning and Transmission Electron Microscope (STEM). The unitwas operated at an accelerating voltage of 200 kV and an emissioncurrent of 30 mA.

2.4. Calculations

The BET specific surface area [24] was calculated from nitrogenadsorption isotherms in the relative pressure range of 0.05–0.2.The total pore volume [25] was estimated from the amount ad-sorbed at a relative pressure of �0.99. The pore size distributionswere calculated from nitrogen adsorption isotherms at �196 �Cusing the improved KJS method calibrated for cylindrical mesop-ores with diameters up to 10 nm [26].

3. Results

Nitrogen adsorption and pore size distributions were used toexamine the changes in the physicochemical characteristics ofthe carbon–silica materials with incorporated silver nanoparticles.Fig. 1 shows adsorption isotherms and pore size distributions forthe silver-containing carbon materials prepared with 1 mmol load-ing of silver that includes carbon (C–Ag), carbon–silica composites(CS–AgT) and final carbons obtained after dissolving the silica com-ponent from the parent carbon–silica composites (C–AgT). All sam-ples exhibit isotherms of type IV with H1-type hysteresis loopindicating the presence of mesopores. Adsorption isotherms forthe final carbon materials (C–AgT) show the highest nitrogen up-take due to increased microporosity created by silica removal.The carbon sample synthesized without TEOS (C–Ag) shows totaladsorption lower than that obtained for the aforementioned sam-ples but higher than that for the carbon–silica composites (CS–AgT). These data stay in a good agreement, taking into account thatthe silica portion in the silver-containing composites is non-porousunlike carbon which possesses some microporosity as seen in theC–Ag carbon. The aforementioned account of microporosity is evi-dent in both final carbons containing silver, having the microporevolumes of 0.18 and 0.21 cm3/g for the C–1Ag40T and C–1Ag60Tsamples, respectively; these values are higher than those for theremaining samples in this series. This increase in microporosityis also visible on the PSD curves up to 4 nm. The specific surfacearea varies from 353 m2/g evaluated for the composite to779 m2/g for the final Ag–carbon material obtained after dissolvingsilica (see Table 1). In the case of mesoporosity, no radical changeswere observed including both the mesopore volumes and the porediameters, the latter were found to be �1 nm larger for the sam-ples synthesized with TEOS. However, the bimodal desorptionbranches suggest the existence of some pore constrictions.

Nitrogen adsorption isotherms and the corresponding pore sizedistributions for the materials synthesized with doubled loading ofsilver (2 mmol) are presented in Fig. 2. In the case of this series of

Relative Pressure (p/po)

Vol

ume

Ads

orbe

d (c

m3 ST

P/g)

0

100

200

300

400C-1AgCS-1Ag40TC-1Ag40TCS-1Ag60T C-1Ag60T

Pore Width (nm)

0.0 0.2 0.4 0.6 0.8 1.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0

PSD

(cm

3 /g.n

m)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16C-1AgCS-1Ag40TC-1Ag40TCS-1Ag60TC-1Ag60T

Fig. 1. Nitrogen adsorption isotherms and the corresponding pore size distributions for the carbons and carbon composites prepared with 1 mmol loading of silver.

Table 1Structural properties of the carbon samples studied.a

Sample SBET(m2/g) Vt (cm3/g) Vmi (cm3/g) Vme (cm3/g) wKJS (nm) RTGA% d (nm)

C–1Ag 571 0.50 0.15 0.35 7.1 23.3 10.1C–2Ag 561 0.50 0.15 0.35 7.0 25.4 10.0CS-1Ag40T 500 0.47 0.13 0.34 7.8 38.1 10.1CS-2Ag40T 364 0.32 0.05 0.27 8.0 47.8 10.0CS-1Ag60T 353 0.32 0.01 0.31 8.2 54.6 10.4CS-2Ag60T 212 0.19 0.06 0.13 8.0 70.8 11.0C–1Ag40T 779 0.65 0.18 0.47 7.6 23.9 10.4C–2Ag40T 495 0.42 0.16 0.26 8.2 47.1 10.5C–1Ag60T 712 0.57 0.21 0.36 8.2 35.5 10.7C–2Ag60T 578 0.42 0.19 0.23 8.0 52.3 10.8

Vt – single-point pore volume; Vmi – volume of fine pores defined as the difference Vt � Vme; Vme – volume of mesopores obtained by integration of PSD in the range �3.5–30 nm; wKJS – mesopore diameter at the maximum of the PSD curve; RTGA – residue obtained by the TG analysis in air.

a SBET – BET surface area.

L. Sterk et al. / Microporous and Mesoporous Materials 156 (2012) 121–126 123

samples, the silver-containing carbon prepared without TEOSexhibits the highest nitrogen uptake. Surprisingly, the Ag-carbonmaterials with etched silica component are characterized by smal-ler total adsorption, which is a reverse trend to that observed forthe series with 1 mmol loading of silver. Even though the capillarycondensation steps almost overlap each other, there is an easilynoticeable difference at low p/po values revealing differentamounts of micropores created after dissolution of the TEOS-gen-erated silica. Taking this into account, it is not surprising that theisotherms for composite materials also overlap and have the low-est adsorption values. Based on the entries in Table 1 and thePSD curves one can track all changes in micro- and mesoporosity.

Relative Pressure (p/po)

Vol

ume

Ads

orbe

d (c

m3 ST

P/g)

0

100

200

300

C-2AgCS-2Ag40TC-2Ag40T CS-2Ag60T C-2Ag60T

0.0 0.2 0.4 0.6 0.8 1.0

3

Fig. 2. Nitrogen adsorption isotherms and the corresponding pore size distributions

Generally, the BET surface areas show lower values mostly dueto bigger loadings of non-adsorbing silver in the samples. For thisreason, the specific surface area even for the final carbons (C–AgT) stays close to the value obtained for the C–2Ag material,which is 560 m2/g. The same decreasing trend is also carried formicro- and mesopore volumes.

TEM images shown in Fig. 3 clearly indicate the presence of uni-form and hexagonally ordered mesopores. The carbon samplessynthesized without TEOS, C–1Ag and C–2Ag, show a very goodordering of mesopores. The periodicity of these materials wasmaintained for the silver-containing carbon samples prepared withsmaller loading of TEOS (40 wt.%). After increasing TEOS loading to

Pore Width (nm)

2.0 4.0 6.0 8.0 10.0 12.0 14.0

PSD

(cm

/g.n

m)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16C-2AgCS-2Ag40TC-2Ag40TCS-2Ag60T C-2Ag60T

for the carbons and carbon composites prepared with 2 mmol loading of silver.

Fig. 3. TEM images of the silver-containing carbon samples studied; all scale bars are 50 nm.

0.5 1.0 1.5 2.0 2.5 3.0

Inte

nsity

(a.

u.)

C-1Ag

C-1Ag40T

CS-1Ag40T

2θ(°) 2θ(°)0.5 1.0 1.5 2.0 2.5 3.0

Inte

nsity

(a.

u.)

C-1Ag

C-1Ag60T

CS-1Ag60T

2θ(°)0.5 1.0 1.5 2.0 2.5 3.0

Inte

nsity

(a.

u.)

C-2Ag

C-2Ag40T

CS-2Ag40T

2θ(°)0.5 1.0 1.5 2.0 2.5 3.0

Inte

nsity

(a.

u.)

C-2Ag

CS-2Ag60T

C-2Ag60T

Fig. 4. Small angle XRD patterns for the samples studied.

124 L. Sterk et al. / Microporous and Mesoporous Materials 156 (2012) 121–126

60 wt.% the mesoporous structure of the carbon samples becamemore worm-like as shown in the bottom panels of Fig. 3, althoughordered domains were also observed (not shown in this figure).

Periodicity was also evaluated based on small angle powder X-ray diffraction patterns (Fig. 4). The presence of an intense peak inthe range between 0.5� and 1� suggests good ordering in all sam-ples. Also, a slight shift of this peak towards smaller values of 2hdenotes a small (0.2 nm) increase in the pore diameter visible onthe PSD curves obtained from adsorption data. Based on the syn-thesis of similar materials [27,28] the expected ordering is 2D hex-agonal (p6mm). Although the symmetry group cannot bedetermined from the XRD data, TEM images suggest a hexagonalarrangement of pores (Fig. 3).

The presence of silver was confirmed by wide angle XRD mea-surements (Fig. 5). The four reflection peaks (111), (200), (220),(311) appeared for each material, which were identified as silvercrystals possessing a cubic structure with Fm3m symmetry (basedon JCPDS card number 087-0597). Crystallite diameters, calculatedfrom the first (most intense) peak using the Scherrer equation,were determined to be in the range of 43–61 nm. These particlesare surrounded by porous carbon. The size of formed silver nano-particles explains the pore blockage suggested by the shape of hys-teresis loops and also justifies a considerably lower adsorptionobtained for the samples with higher silver loading (Fig. 2). More-over, it is well known that at higher temperatures metallic speciescan migrate across a surface and agglomerate creating larger parti-cles [28]. Taking this fact into account and the data obtained for thesamples prepared without TEOS, which suggest the presence ofsmaller silver nanoparticles, one can speculate that the narrowand intense wide angle XRD peaks dominate and reflect the afore-mentioned larger silver nanoparticles formed during carbonizationprocess by aggregation of a portion of smaller ones.

2θ(°)

30 40 50 60 70 80

Inte

nsity

(a.

u.)

C-2Ag

C-2Ag40T

CS-2Ag40T

∗

∗∗ ∗

∗

∗ ∗ ∗

∗

∗ ∗ ∗

2θ(°)

30 40 50 60 70 80

Inte

nsity

(a.

u.)

*

** *

CS-1Ag40T

*

*

C-1Ag40T* *

*

*

C-1Ag

* *

Fig. 5. Wide angle XRD patterns for the silver-containing carbon and silica–carbonsamples studied.

L. Sterk et al. / Microporous and Mesoporous Materials 156 (2012) 121–126 125

Thermogravimetric analysis was used to determine silver andsilica residue in the Ag-containing carbons and composite materi-als (Table 1). C–1Ag and C–2Ag show similar values of 23.3% and25.4% respectively, indicating lower than expected value of silverresidue found in the latter sample. The residue value for C–1Ag issupported by the value obtained for C–1Ag40T, 23.9%, becauseboth should be equal upon complete removal of TEOS. The samerelation does not appear at higher concentration of silver whereC–2Ag40T has a residue of 47.1% indicating that there is somenon-dissolved silica. The residue values for the composite materi-als fall in the range of 38–71% depending on the amounts of silicaand silver in the system. The final carbons obtained after removalof silica from the samples prepared with 60 wt.% of TEOS showedhigher values than their carbon counterparts (C–1Ag and C–2Ag)indicating the presence of residual silica, which can contribute tothe pore blocking mentioned above.

4. Discussion

4.1. TEOS and silver effects

It has been reported that TEOS is capable of co-assembly withphenolic-resin providing a facile method for the incorporation ofsilica species in the framework, which gives structural supportand minimizes the sample shrinkage by as much as 20% occurringunder heat treatment [27]. This is especially beneficial for the car-bons obtained under alkaline conditions, which suffer extensiveframework shrinkage during carbonization. Another benefit ofusing TEOS is the creation of an additional microporosity after dis-solution of the TEOS-generated silica [29,30]. High microporosityand surface area are very desirable for number of catalytic applica-tions. In our case, the first noticeable effect of TEOS addition is anincrease in the diameter of mesopores compared to those of C–Agmaterials, which can originate from preferential interaction of pre-hydrolyzed TEOS species with PEO blocks of the soft-template usedor may be a result of smaller framework shrinkage during carbon-ization. Also, as reported elsewhere, there are at least two possibleTEOS accumulation scenarios resulting in carbons with tuned bothmicro- and mesoporosity [31]. If TEOS is evenly distributed in thecarbon matrix, an increase in microporosity is expected. This wasobserved for all final materials, however it is especially pro-nounced for C–1Ag-40T and both carbons prepared with 60% ofTEOS. In the second case, already mentioned at the beginning, TEOSspecies exhibit favorable interactions with PEO blocks causing apore enlargement, which also translates to higher mesopore vol-ume. Interestingly, it is also possible that both phenomena occursimultaneously, as it is for C–2Ag60T material, where an increase

in micro- and mesopore volume is observed. Based on that, it is rel-atively easy to track TEOS incorporation pattern. However, it is notso simple to predict how the latter looks like in the case of silver.Data obtained from thermogravimetric analysis for the samplesprepared without TEOS show very similar residues for both car-bons (C–1Ag and C–2Ag) indicating that the use of twice higherconcentration of silver nitrate in the synthesis did not producethe sample with much higher silver loading. Note that both sam-ples, C–1Ag and C–2Ag, were synthesized under the same acidicconditions by using HCl. This synthesis results in the phase separa-tion and only the polymeric phase is subjected to carbonization.Note that the presence of Cl� ions in the synthesis mixture facili-tates the accumulation of silver in the polymeric phase. The exces-sive silver ions stay in aqueous phase; therefore, doubling theconcentration of silver nitrate did not result in doubling the silverloading in C–2Ag. However, the residue percentage obtained forthe composite materials stays pretty close to theoretical valuessuggesting that TEOS may help with silver incorporation. Thereare numerous reports showing strong interaction between silverions and silanes [32–34], which can be adapted, for example, to ob-tain uniform layers of silver nanoparticles on the desired surfaces.Despite that, silver ions also exhibit strong interactions with aryl-rings [33,34], which additionally facilitate Ag incorporation.

Also, it is noteworthy that due to high atomic weight of silver,its weight percentage in the C-AgT samples is high. This has a pro-nounced effect on the overall adsorption characteristics of the sil-ver-containing carbons due to significantly smaller amount ofhighly adsorbing carbon per unit mass of the composite sample.This explains a noticeable drop in the BET surface area, the totalpore volume and the volumes of mesopores and micropores forthe silver-containing carbons with increasing silver loading. Notethat the observed reduction in the specific surface area and porevolumes of the metal-containing samples is not solely caused bythe decrease of the carbon mass in the composite sample. An addi-tional reduction may origin from partial blockage of the pores incarbons by embedded metal nanoparticles. These effects have beenobserved for analogous systems containing nickel nanoparticles[35,36].

In our previous work [22] the generation of nickel nanoparticlesin carbon matrix in the presence of TEOS was demonstrated. Inboth cases we kept the same synthesis conditions for TEOS andmetal salt loadings to be able to determine and compare the carbonmesophase formation in relation to the amount of metal salt. Theuse of two different metal nitrates for the formation of nanoparti-cles in mesoporous carbons showed that the aforementioned ef-fects are more pronounced for silver. This is evident bycomparing the total pore volumes, which for nickel-containing car-bons are in the range 0.53–1.38 cm3/g (see Ref. [22]) and for the sil-ver-containing carbons this range consists of much smaller values,i.e., 0.19–0.65 cm3/g. The surface areas were also considerablyhigher for the nickel-containing carbons (491–1692 m2/g) thanthose for the silver-containing analogues (212–805 m2/g). Finally,the pore widths varied only slightly, where the average pore widthfor the silver-containing carbons was �8.0 nm compared to 7.5 nmfor the nickel-containing analogues. It should be noted that in thecase of high nickel loading a secondary mesoporous network wasformed, which contributed to some extraordinary high values ofthe surface area (1692 and 1273 m2/g) and pore volumes (1.59and 1.38 cm3/g) but the aforementioned trends are still observedfor the remaining nickel-containing carbons. These differencesare likely a result of greater blockage of pores by silver particles.Another mentionable topic pertains to the metals themselves (Agand Ni) and how they interact with carbon. It is well known thatnickel interaction with carbon at high temperatures often resultsin catalytic graphitization [37]. This is on account of nickel actingas a catalyst for the formation of graphite. As a prove for that, we

126 L. Sterk et al. / Microporous and Mesoporous Materials 156 (2012) 121–126

were able to find a peak at 26� in wide angle XRD patterns indicat-ing some graphitic domains in the Ni-containing materials, espe-cially those made with high concentration of nickel. This isshown in the nickel-containing etched and composite materials.This peak is not present on the wide angle XRD profiles for the sil-ver-containing samples. Silver is not a good catalyst for graphiteformation. Another difference for consideration is the migratorynature of silver on the carbon surfaces [38], which may result inhigher blockage of carbon pores.

5. Conclusions

In conclusion, the soft-templating was successfully employedfor the preparation of mesoporous carbon–silica composites con-taining Ag nanoparticles. The resulting silver-containing carbonspossess relatively high surface area and pore volume, althoughhigher values of these quantities were observed for the counter-parts prepared in the presence of nickel salts [22]. The mesoporeordering of the resulting carbons was not significantly affectedby silver loading, which is especially true at small silver loadings.

Acknowledgments

This material is based upon work supported by the National Sci-ence Foundation under CHE-0848352. The authors thank BASF forproviding the triblock polymer. The TEM imaging was performed atthe NIMS, Japan.

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