research article synthesis of conductive ppy/sio 2 aerogels...

Research ArticleSynthesis of Conductive PPySiO2 Aerogels Nanocomposites byIn Situ Polymerization of Pyrrole

Daliana Muller1 Geneviegraveve K Pinheiro2 Tatiana Bendo1 Alberto J Gutieacuterrez Aguayo2

Guilherme M O Barra1 and Carlos R Rambo2

1Polymer and Composites Laboratory Department of Mechanical Engineering Federal University of Santa Catarina88040-900 Florianopolis SC Brazil2Laboratory of Electrical Materials Department of Electrical Engineering Federal University of Santa Catarina88040-900 Florianopolis SC Brazil

Correspondence should be addressed to Carlos R Rambo carlosramboufscbr

Received 11 January 2015 Revised 2 April 2015 Accepted 4 April 2015

Academic Editor Ungyu Paik

Copyright copy 2015 Daliana Muller et alThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Electrical conductive nanocomposite aerogels were synthesized through in situ oxidative polymerization of pyrrole (Py) usingammonium persulfate (APS) as an oxidizing agent in SiO

2gels The effect of Py concentration on the electrical conductivity and

physical and morphological properties of aerogels SiO2PPy was evaluated BET analysis indicated that the surface area of the

composite SiO2PPy decreases with increasing concentration of Py CHN analysis showed an increase in the amount of PPy from

13wt to 23wt with increasing concentration of pyrrole synthesis FTIR-ATR analysis of the composites revealed bands inthe region of 1500ndash1400 cmminus1 indicating the presence of the conductive polymer in the silica aerogel as well as the characteristicbands of Si-O-Si and Si-OH covalent bonds TEMmicrographs revealed the presence of particles of PPy with the increased size ofthe nanoparticles The composites were successfully applied as passive components in RC circuits for low-pass frequency filtersThe filters exhibited a cutoff frequency at approximately 435Hz The aerogels obtained in this work exhibited suitable electricalconductivity for use in various other applications in electronics

1 Introduction

In recent years silica aerogels have been used as advancedmaterial in various applications such as thermal insulationelectric batteries nuclear waste storage catalysis acousticinsulation and adsorbents [1]These materials which exhibitporosity between 95 and 99 are comprised of amesoporousnanostructure of interconnected particles having uniquecharacteristics such as high surface area low density andlow thermal conductivity [1 2] Various strategies have beenused to develop composites of silica aerogels with a varietyof dispersed nanostructures such as TiO

2 Pt Au RuO

2

SnO2 and carbon nanotubes [3ndash5] Therefore it is possible

to design new materials for a given application combiningthe properties of silica aerogel with the desirable propertiesof the embedded material Such class of composites is usuallyprepared through the dispersion of solid particles in a sol

state SiO2matrix before gelation or through impregnation

of suspensions into an already synthesized aerogel [1]Recent works have reported interesting results concern-

ing the incorporation of intrinsically conducting polymers(ICPs) into mesoporous silica (MCM-41) and SiO

2aerogels

[6ndash12] Such class of nanocomposites exhibits a unique com-bination of chemical and physical properties including a highspecific surface area (SSA) and improved mechanical ther-mal and electrical properties which make them suitable fora large variety of technological applications such as sensorsphotovoltaic devices supercapacitors catalysis and elec-trorheological fluids [11ndash14] Polymers such as polypyrrole(PPy) polyaniline (PAni) poly(34-ethylenedioxythiophene)(PEDOT) and polythiophene (PT) are studied most fre-quently especially due to their stability at room temperaturehigh electrical conductivity and ease of synthesis whencompared to other ICPs [15 16]

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2015 Article ID 658476 6 pageshttpdxdoiorg1011552015658476

2 Journal of Nanomaterials

1 cm

Figure 1 Photographs of SiO2(left) and SiO

2PPy aerogels (right)

Several methods were developed to incorporate con-ductive polymers into aerogels including dispersion ofpolyaniline nanofibers into silica sol prior to gelation [6]polymerization of aniline and chitosan in silica aerogels[7] and incorporation of polypyrrole into TiO

2aerogels by

sol-gel process [8] Cheng et al [10ndash12] produced meso-porous material with conducting polypyrrole confined inmesoporous silica through adsorption of pyrrole gas andsubsequent oxidative polymerization All in situ productionmethods showed to improve dispersion and uniformity ofthe dispersant in the aerogelmatrix resulting in homogenousand isotropic mesoporous nanocomposites

In this work we report a one-step sol-gel process forthe synthesis of nanocomposite SiO

2PPy aerogels through

in situ polymerization of different concentrations of pyrrolein silica gels The nanostructure composition and electricalconductivity of the composites were also evaluated and thecomposites were applied as passive elements in low-passfrequency filters

2 Experimental

Pyrrole monomer (Merk analytic) was distilled under vac-uum and stored at 8∘C Oxidizing agent ammonium per-sulfate (APS) (Vetec) was used as received Polypyrrole wasincorporated into SiO

2aerogels through in situ polymeriza-

tion of pyrrole as follows The silica gels were prepared atroom temperature using Py concentrations of 02ndash04molL(023ndash046 g) in a solution (sol) containing 55mL of ethanoland 25mL of tetraethyl orthosilicate (TEOS) under stirringA second solution was prepared containing 014 g of APS55mL of ethanol 35mL of distilled water and 02mL ofammonium fluoride as catalyst The two solutions were thenmixed under stirring and placed into cylindrical PVC moldsfor gel formation

After gelation several solvent changes were performedto substitute ethanol by acetone in the alcogel After solventchanges the gels were submitted to a dryingsolvent extrac-tion process under supercritical CO

2(Supercritical System

Quorum Technologies) at 80 bar for four days The formedSiO2aerogels are translucent white colored as shown in

Figure 1 left while the SiO2PPy (prepared with 04molL

Py) aerogels exhibited a dark grey color (Figure 1 right) andwere mechanically stable to handling

Fourier transform infrared spectroscopy (FTIR) was per-formedwith a Shimadzu model IR PRESTIGE-2 instrumentwith an ATR (attenuated total reflectance) accessory and

Table 1 Polypyrrole content andmicropore volume of the SiO2PPyaerogels prepared with different initial pyrrole concentrations

Composition PPy-content () Pore volume (cm3g)SiO2 00 20 times 10minus1

SiO2PPy [02] 131 10 times 10minus1



ZnSe crystal (ATR Smart Performance module) Spectra ofpure silica aerogels PPy and nanocomposites were recordedin the range of 4000 to 600 cmminus1 by accumulating 64scans at a resolution of 4 cmminus1 Samples were previouslypowdered and analyzed in form of pellets Specific surfacearea and total micropore volume were measured by BETmethod (Quantachrome Nova 1200E) using powdered sam-ples The amount of polypyrrole incorporated in the silicaaerogels was determined by CHN analysis (PerkinElmer2400 series III) X-ray diffraction (XRD) measurements wereobtained at room temperature using a Philips diffractometermodel XrsquoPert with CuK120572 radiation Dried silica aerogels andSiO2PPy composites were placed on an aluminum plate and

scanned over 2120579 interval of 5∘ to 90∘ with steps of 1∘minThenanomorphology of the aerogels was evaluated by transmis-sion electron microscopy (TEM JEOL-JEM 1011) operatingat 100 kV The samples for TEM analysis were prepared bydispersing powdered aerogels on carbon grids The aerogelscontaining polypyrrole in three different concentrations werefragmented in smaller parts and placed between two flexiblemetal electrodes for electrical characterization and testingas low-pass filter components The electrical conductivity ofthe SiO

2PPy aerogels was measured using a high precision

semiconductor analyzer (Agilent B2912A)The aerogels wereused as resistive elements (119877) in RC circuit operating asfrequency filters The low-pass filters were tested by applyinga sinusoidal wave form using a UniSource FG-8102 2MHzSweep Function Generator and the results were registeredusing a Tektronix TDS2000C Digital Storage OscilloscopeThe stimulus for each filter was a sinusoidal signal with2V peak-to-peak and the time constant (120591 in seconds) wasobtained using a ceramic capacitor (119862 = 10 pF)

3 Results and Discussion

Table 1 shows the polypyrrole content determined by CHNand micropore volume obtained by BET of the SiO

2PPy

aerogels prepared with different initial pyrrole concentra-tions

It is observed that with increasing concentration of Pyto be polymerized in the SiO

2aerogel the pore volume

decreases by approximately an order of magnitude whichmay be an indication that polymerization occurs between thepores of the aerogel CHN analysis revealed as expected thatthe higher the concentration of pyrrole synthesis the greaterthe conducting polymer amount in the silica aerogel

Journal of Nanomaterials 3

Tran

smitt

ance

(au

)

Wavenumber (cmminus1)

SiO2

SiO2PPy [02]

SiO2PPy [03]

SiO2PPy [04]

2500 2000 1500 1000

PPy

Figure 2 FTIR (ATR) spectra (transmittance) of SiO2and SiO

2PPy

nanocomposites prepared with different initial pyrrole concentra-tions

Inte

nsity

(au

)

2120579 (deg)10 20 30 40 50 60 70 80 90

SiO2

SiO2PPy [02]

SiO2PPy [03]

SiO2PPy [04]

PPyAPS

Figure 3 X-ray diffraction spectra of PPY SiO2 and SiO

2PPy

aerogels prepared with different pyrrole concentrations

Figure 2 shows FTIR spectra of silica aerogel andSiO2PPy nanocomposites produced with different concen-

trations of pyrrole The spectrum of silica aerogel has threecharacteristic bands centered at 1060 960 and 800 cmminus1Intense vibrations of covalent Si-O bonds that appear mostlyin the regions of 1000ndash1200 cmminus1 can also be observedindicating the existence of a dense chain of silica in which theoxygen atoms play the role of bridging each of the two siliconsites Another characteristic region appears around 795 cmminus1which is related to the symmetric stretching of Si-O-Si bonds[17] The vibrations of the Si-OH bond can be visualized inthe region of 796 cmminus1

After polymerization of pyrrole in the silica aerogels thecomposites exhibit a band around 1460 cmminus1 related to theC-N bond of polypyrrole [18] With enhancing of initial pyrroleconcentration in the synthesis of the nanocomposites theintensity of this band increased indicating the increasing

content of polypyrrole in the aerogels as previously observedin Table 1

Figure 3 shows the X-ray diffractograms of SiO2and

SiO2PPy aerogels produced with different initial Py concen-

trationsThe XRD spectrum of PPy exhibits no defined narrow

diffraction peaks but a broad halo at 2120579 around 25∘ char-acteristic of amorphous polypyrrole [19] The broad peakcentered between 2120579 = 20∘ndash30∘ in the SiO

2spectrum is

characteristic of amorphous nano-SiO2[20]The structure of

silica matrix was not significantly modified that is no peakshift is observed in the SiO

2PPy composites which also

confirms the results obtained by FTIRFigure 4 shows TEM micrographs of SiO

2aerogel and

SiO2PPy nanocomposites prepared with different initial

pyrrole concentrationsIt can be seen that the silica aerogel (Figures 4(a) and 4(b))

presents interconnected particles with diameters between10 and 20 nm typical of this class of material [21] Theamorphous structure of the SiO

2particles is confirmed by

the electron diffraction halo (insert in Figure 4(a)) As theconcentration of pyrrole in a silica aerogel increases thereis an increase in particle size of the composites (Figures4(c) to 4(e)) After in situ polymerization of pyrrole in thesilica aerogel clusters randomly distributed in the aerogelmatrix were formed not altering its nanostructure Similarobservations were reported by Harreld et al [22]

Figure 5 shows the specific surface area and the electricalconductivity of the SiO

2and SiO

2PPy aerogels in function

of initial pyrrole contentThe BET analysis revealed that the surface area of the

composite SiO2PPy decreases with increasing concentration

of Py A significant reduction in the surface area of thecomposite between 48 and 65 with the concentration ofpyrrole during synthesis of aerogel was observed WhileSiO2aerogels exhibited SSA of 540m2g the SiO

2PPy

aerogels exhibited surface areas in the range between 188and 259m2g This decrease was a result of the presenceof agglomerated particles incorporated in the silica aerogelDespite this decrease the nanocomposites showed highsurface area at least the half when compared to pure SiO

2

aerogel and to other SiO2-based aerogels [23] The amount

and dispersion of polypyrrole in the silica aerogel influencedthe electrical conductivity of the nanocompositesThe higherthe initial Py concentration in the gels was and hence thepolymer content after synthesis the higher the electrical con-ductivity was achieved in the SiO

2PPy aerogelsThe aerogels

exhibited values of conductivity close to a semiconductormaterial Comparing SiO

2PPy composites with the silica

aerogel there is an increase in conductivity of three ordersof magnitude This can be explained by the small amount ofpolymerized polypyrrole in the aerogel matrix hindering thecontact between particles of polypyrrole As the Py concen-tration increases more continuously conducting pathwaysare formed leading to an increase in the conductivity

Figure 6 shows the performance of the low-pass filtersThe frequency range was limited for the signal generator res-olution All SiO

2PPy composites exhibit cutoff frequencies


5 1nm

20nm

(a)

50nm

(b)

50nm

(c)

50nm

(d)

50nm

(e)

Figure 4 TEMmicrographs of SiO2aerogel (a and b) and SiO

2PPy nanocomposites prepared with different initial pyrrole concentrations

(c) 02molL (d) 03molL and (e) 04molL Insert in (a) is an electron diffraction pattern of a SiO2particle

of around 435Hz Signal attenuation is also present for thecomposites ranging from 30 to 50 which indicates lossesprobably due to the electrodes-sample contact resistanceTheobtained time constants for the RC circuits were 68 times 10minus423 times 10minus4 and 52 times 10minus5 for the composites prepared withPy concentrations of 02 03 and 04molL respectively

4 Conclusion

Electrical conductive SiO2PPy aerogels were prepared by in

situ polymerization of pyrrole in SiO2aerogelsThe SiO

2PPy

aerogels exhibit higher conductivity approximately three

orders of magnitude compared to pure silica aerogel Thepolymerization of polypyrrole on silica aerogel resulted inaerogels with lower BET specific surface area and largerparticle sizes but no significant changes in the structure andtypical morphology of the aerogels The electrical conductiv-ity of the mesoporous nanocomposites produced here wassuitable for application as passive component in low-passfrequency filters

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Journal of Nanomaterials 5Sp

ecifi

c sur

face

area

(m2g)

Py-content (MolL)

Elec

tric

al co

nduc

tivity

(Sc

m)

60

50

40

30

20

10

00

00 01 02 03 04 05

600

550

500

450

400

350

300

250

200

150

Surface areaConductivity

times10minus7

Figure 5 Specific surface area and the electrical conductivity of theSiO2and SiO

2PPy aerogels in function of initial pyrrole content

Vou

tV

in

Frequency (Hz)PPy [02]PPy [03]PPy [04]

08

07

06

05

04

03

02

01

101

102

103

104

105

106

Figure 6 Performance curve (119881out119881in versus frequency) of low-passfrequency filters mounted with SiO

2PPy composites with different

initial pyrrole concentrations

Acknowledgments

The authors thank the National Council for Scientific andTechnological Development (CNPq Brazil) and Coordina-tion for the Improvement of Higher Level Personnel (CAPESBrazil) for the financial support Central Laboratory ofElectronicMicroscopy (LCME-UFSC) is also acknowledged

References

[1] J L Gurav I-K Jung H-H Park E S Kang and D YNadargi ldquoSilica aerogel synthesis and applicationsrdquo Journal ofNanomaterials vol 2010 Article ID 409310 11 pages 2010

[2] Z Ulker I Erucar S Keskin and C Erkey ldquoNovel nanos-tructured composites of silica aerogels with a metal organicframeworkrdquo Microporous and Mesoporous Materials vol 170pp 352ndash358 2013

[3] M N P Weerasinghe and K J Klabunde ldquoChromium oxideloaded silica aerogels novel visible light photocatalytic mate-rials for environmental remediationrdquo Journal of Photochemistryand Photobiology A Chemistry vol 254 pp 62ndash70 2013

[4] H Ren and L Zhang ldquoIn situ growth approach for preparationof Au nanoparticle-doped silica aerogelrdquo Colloids and SurfacesA vol 372 no 1-3 pp 98ndash101 2010

[5] S V Ingale P U Sastry P B Wagh et al ldquoSynthesis andmicro structural investigations of titania-silica nano compositeaerogelsrdquoMaterials Chemistry and Physics vol 135 no 2-3 pp497ndash502 2012

[6] D J Boday B Muriithi R J Stover and D A Loy ldquoPolyanilinenanofiber-silica composite aerogelsrdquo Journal of Non-CrystallineSolids vol 358 no 12-13 pp 1575ndash1580 2012

[7] S Zhao H Xu L Wang P Zhu W M Risen Jr and JWilliam Suggs ldquoSynthesis of novel chitaline-silica aerogels withspontaneous Au and Ag nanoparticles formation in aerogelsmatrixrdquo Microporous and Mesoporous Materials vol 171 pp147ndash155 2013

[8] J-D Kwon P-H Kim J-H Keum and J S Kim ldquoPolypyr-roletitania hybrids synthetic variation and test for the photo-voltaicmaterialsrdquo Solar EnergyMaterials and Solar Cells vol 83no 2-3 pp 311ndash321 2004

[9] Q Cheng V Pavlinek C Li A Lengalova Y He and P SahaldquoSynthesis and characterization of new mesoporous materialwith conducting polypyrrole confined in mesoporous silicardquoMaterials Chemistry and Physics vol 98 no 2-3 pp 504ndash5082006

[10] L Kavan J Rathousky M Gratzel V Shklover and A ZukalldquoMesoporous thin film TiO

2electrodesrdquo Microporous and

Mesoporous Materials vol 44-45 pp 653ndash659 2001[11] Q Cheng V Pavlinek A Lengalova C Li Y He and P Saha

ldquoConducting polypyrrole confined in ordered mesoporoussilica SBA-15 channels preparation and its electrorheologyrdquoMicroporous andMesoporousMaterials vol 93 no 1ndash3 pp 263ndash269 2006

[12] Q Cheng V Pavlinek A Lengalova C Li T Belza andP Saha ldquoElectrorheological properties of new mesoporousmaterial with conducting polypyrrole in mesoporous silicardquoMicroporous andMesoporousMaterials vol 94 no 1ndash3 pp 193ndash199 2006

[13] T Yamata H-S Zhou H Uchida et al ldquoSurface photovoltageNO gas sensor with properties dependent on the structure ofthe self-ordered mesoporous silicate filmrdquo Advanced Materialsvol 14 no 11 pp 812ndash815 2002

[14] H Kim and B N Popov ldquoCharacterization of hydrous ruthe-nium oxidecarbon nanocomposite supercapacitors preparedby a colloidal methodrdquo Journal of Power Sources vol 104 no1 pp 52ndash61 2002

[15] Y Lu A Pich H-J P Adler G Wang D Rais and SNespurek ldquoComposite polypyrrole-containing particles andelectrical properties of thin films prepared therefromrdquo Polymervol 49 no 23 pp 5002ndash5012 2008

[16] Y Yang Y Chu F Yang and Y Zhang ldquoUniform hollow con-ductive polymer microspheres synthesized with the sulfonatedpolystyrene templaterdquoMaterials Chemistry and Physics vol 92no 1 pp 164ndash171 2005


[17] R Al-Oweini and H El-Rassy ldquoSynthesis and characterizationby FTIR spectroscopy of silica aerogels prepared using severalSi(OR)

4and R10158401015840Si(OR1015840)

3precursorsrdquo Journal of Molecular

Structure vol 919 no 1ndash3 pp 140ndash145 2009[18] M Omastova M Trchova J Kovarova and J Stejskal ldquoSynthe-

sis and structural study of polypyrroles prepared in the presenceof surfactantsrdquo Synthetic Metals vol 138 no 3 pp 447ndash4552003

[19] R E Partch S G Gangoli E Matijevic W Cai and SArajs ldquoConducting polymer composites I Surface-inducedpolymerization of pyrrole on iron(III) and cerium(IV) oxideparticlesrdquo Journal of Colloid and Interface Science vol 144 no1 pp 27ndash35 1991

[20] NThuadaij and A Nuntiya ldquoPreparation of nanosilica powderfrom rice husk ash by precipitation methodrdquo Chiang MaiJournal of Science vol 35 no 1 pp 206ndash211 2008

[21] C-MWu S-Y Lin andH-L Chen ldquoStructure of a monolithicsilica aerogel prepared from a short-chain ionic liquidrdquo Micro-porous and Mesoporous Materials vol 156 pp 189ndash195 2012

[22] J Harreld H P Wong B C Dave B Dunn and L FNazar ldquoSynthesis and properties of polypyrrole-vanadiumoxide hybrid aerogelsrdquo Journal of Non-Crystalline Solids vol225 no 1ndash3 pp 319ndash324 1998

[23] Q Tang and T Wang ldquoPreparation of silica aerogel from ricehull ash by supercritical carbon dioxide dryingrdquoThe Journal ofSupercritical Fluids vol 35 no 1 pp 91ndash94 2005

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


1 cm

Figure 1 Photographs of SiO2(left) and SiO

2PPy aerogels (right)

Several methods were developed to incorporate con-ductive polymers into aerogels including dispersion ofpolyaniline nanofibers into silica sol prior to gelation [6]polymerization of aniline and chitosan in silica aerogels[7] and incorporation of polypyrrole into TiO

2aerogels by

sol-gel process [8] Cheng et al [10ndash12] produced meso-porous material with conducting polypyrrole confined inmesoporous silica through adsorption of pyrrole gas andsubsequent oxidative polymerization All in situ productionmethods showed to improve dispersion and uniformity ofthe dispersant in the aerogelmatrix resulting in homogenousand isotropic mesoporous nanocomposites

In this work we report a one-step sol-gel process forthe synthesis of nanocomposite SiO

2PPy aerogels through

in situ polymerization of different concentrations of pyrrolein silica gels The nanostructure composition and electricalconductivity of the composites were also evaluated and thecomposites were applied as passive elements in low-passfrequency filters

2 Experimental

Pyrrole monomer (Merk analytic) was distilled under vac-uum and stored at 8∘C Oxidizing agent ammonium per-sulfate (APS) (Vetec) was used as received Polypyrrole wasincorporated into SiO

2aerogels through in situ polymeriza-

tion of pyrrole as follows The silica gels were prepared atroom temperature using Py concentrations of 02ndash04molL(023ndash046 g) in a solution (sol) containing 55mL of ethanoland 25mL of tetraethyl orthosilicate (TEOS) under stirringA second solution was prepared containing 014 g of APS55mL of ethanol 35mL of distilled water and 02mL ofammonium fluoride as catalyst The two solutions were thenmixed under stirring and placed into cylindrical PVC moldsfor gel formation

After gelation several solvent changes were performedto substitute ethanol by acetone in the alcogel After solventchanges the gels were submitted to a dryingsolvent extrac-tion process under supercritical CO

2(Supercritical System

Quorum Technologies) at 80 bar for four days The formedSiO2aerogels are translucent white colored as shown in

Figure 1 left while the SiO2PPy (prepared with 04molL

Py) aerogels exhibited a dark grey color (Figure 1 right) andwere mechanically stable to handling

Fourier transform infrared spectroscopy (FTIR) was per-formedwith a Shimadzu model IR PRESTIGE-2 instrumentwith an ATR (attenuated total reflectance) accessory and

Table 1 Polypyrrole content andmicropore volume of the SiO2PPyaerogels prepared with different initial pyrrole concentrations

Composition PPy-content () Pore volume (cm3g)SiO2 00 20 times 10minus1




ZnSe crystal (ATR Smart Performance module) Spectra ofpure silica aerogels PPy and nanocomposites were recordedin the range of 4000 to 600 cmminus1 by accumulating 64scans at a resolution of 4 cmminus1 Samples were previouslypowdered and analyzed in form of pellets Specific surfacearea and total micropore volume were measured by BETmethod (Quantachrome Nova 1200E) using powdered sam-ples The amount of polypyrrole incorporated in the silicaaerogels was determined by CHN analysis (PerkinElmer2400 series III) X-ray diffraction (XRD) measurements wereobtained at room temperature using a Philips diffractometermodel XrsquoPert with CuK120572 radiation Dried silica aerogels andSiO2PPy composites were placed on an aluminum plate and

scanned over 2120579 interval of 5∘ to 90∘ with steps of 1∘minThenanomorphology of the aerogels was evaluated by transmis-sion electron microscopy (TEM JEOL-JEM 1011) operatingat 100 kV The samples for TEM analysis were prepared bydispersing powdered aerogels on carbon grids The aerogelscontaining polypyrrole in three different concentrations werefragmented in smaller parts and placed between two flexiblemetal electrodes for electrical characterization and testingas low-pass filter components The electrical conductivity ofthe SiO

2PPy aerogels was measured using a high precision

semiconductor analyzer (Agilent B2912A)The aerogels wereused as resistive elements (119877) in RC circuit operating asfrequency filters The low-pass filters were tested by applyinga sinusoidal wave form using a UniSource FG-8102 2MHzSweep Function Generator and the results were registeredusing a Tektronix TDS2000C Digital Storage OscilloscopeThe stimulus for each filter was a sinusoidal signal with2V peak-to-peak and the time constant (120591 in seconds) wasobtained using a ceramic capacitor (119862 = 10 pF)

3 Results and Discussion

Table 1 shows the polypyrrole content determined by CHNand micropore volume obtained by BET of the SiO

2PPy

aerogels prepared with different initial pyrrole concentra-tions

It is observed that with increasing concentration of Pyto be polymerized in the SiO

2aerogel the pore volume

decreases by approximately an order of magnitude whichmay be an indication that polymerization occurs between thepores of the aerogel CHN analysis revealed as expected thatthe higher the concentration of pyrrole synthesis the greaterthe conducting polymer amount in the silica aerogel


Tran

smitt

ance

(au

)


SiO2

SiO2PPy [02]

SiO2PPy [03]

SiO2PPy [04]

2500 2000 1500 1000

PPy


2PPy


Inte

nsity

(au

)

2120579 (deg)10 20 30 40 50 60 70 80 90

SiO2

SiO2PPy [02]

SiO2PPy [03]

SiO2PPy [04]

PPyAPS


2PPy










2spectrum is





2aerogel and







2and SiO





2PPy


2










5 1nm

20nm

(a)

50nm

(b)

50nm

(c)

50nm

(d)

50nm

(e)





4 Conclusion



2PPy






ecifi

c sur

face

area

(m2g)

Py-content (MolL)

Elec

tric

al co

nduc

tivity

(Sc

m)

60

50

40

30

20

10

00

00 01 02 03 04 05

600

550

500

450

400

350

300

250

200

150


times10minus7



Vou

tV

in


08

07

06

05

04

03

02

01

101

102

103

104

105

106




Acknowledgments


References





















4and R10158401015840Si(OR1015840)
















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Tran

smitt

ance

(au

)


SiO2

SiO2PPy [02]

SiO2PPy [03]

SiO2PPy [04]

2500 2000 1500 1000

PPy


2PPy


Inte

nsity

(au

)

2120579 (deg)10 20 30 40 50 60 70 80 90

SiO2

SiO2PPy [02]

SiO2PPy [03]

SiO2PPy [04]

PPyAPS


2PPy










2spectrum is





2aerogel and







2and SiO





2PPy


2










5 1nm

20nm

(a)

50nm

(b)

50nm

(c)

50nm

(d)

50nm

(e)





4 Conclusion



2PPy






ecifi

c sur

face

area

(m2g)

Py-content (MolL)

Elec

tric

al co

nduc

tivity

(Sc

m)

60

50

40

30

20

10

00

00 01 02 03 04 05

600

550

500

450

400

350

300

250

200

150


times10minus7



Vou

tV

in


08

07

06

05

04

03

02

01

101

102

103

104

105

106




Acknowledgments


References





















4and R10158401015840Si(OR1015840)
















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




5 1nm

20nm

(a)

50nm

(b)

50nm

(c)

50nm

(d)

50nm

(e)





4 Conclusion



2PPy






ecifi

c sur

face

area

(m2g)

Py-content (MolL)

Elec

tric

al co

nduc

tivity

(Sc

m)

60

50

40

30

20

10

00

00 01 02 03 04 05

600

550

500

450

400

350

300

250

200

150


times10minus7



Vou

tV

in


08

07

06

05

04

03

02

01

101

102

103

104

105

106




Acknowledgments


References





















4and R10158401015840Si(OR1015840)
















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




ecifi

c sur

face

area

(m2g)

Py-content (MolL)

Elec

tric

al co

nduc

tivity

(Sc

m)

60

50

40

30

20

10

00

00 01 02 03 04 05

600

550

500

450

400

350

300

250

200

150


times10minus7



Vou

tV

in


08

07

06

05

04

03

02

01

101

102

103

104

105

106




Acknowledgments


References





















4and R10158401015840Si(OR1015840)
















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





4and R10158401015840Si(OR1015840)
















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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