the effect of peg encapsulated silver

ORIGINAL PAPER

The effect of PEG encapsulated silver nanoparticleson the thermal and electrical property of sonochemicallysynthesized polyaniline/silver nanocomposite

Satyendra Mishra & Navinchandra G. Shimpi & Tanushree Sen

Received: 25 June 2012 /Accepted: 7 December 2012 /Published online: 19 December 2012# Springer Science+Business Media Dordrecht 2012

Abstract An investigation of microstructure of polyanilinenanocomposite is presented. The highly stable, semicon-ducting polyaniline/silver nanocomposites are prepared in-situ, employing the acoustic cavitation mechanism to obtainthe composite in nanophase. The materials are characterizedby UV-visible spectroscopy (UVvis), transmission electronmicroscopy (TEM), thermogravimetric analyzer (TGA) andfourier transform infrared spectroscopy (FTIR). The poly-aniline nanocomposites have an extended conformation inN-methyl-2-pyrrolidinone (NMP), as seen from UVvisspectra. The plasmon resonances for silver nanoplates arealso seen. A high thermal stability is observed for the poly-aniline/silver nanocomposites which increased with increas-ing silver content. The TEM studies show that thepolyaniline is formed as nanofibers, with plate-like metallicsilver nanoparticles (50 nm35 nm in dimension) embed-ded into them. From the electrical conductivity measure-ments of pure polyaniline and its nanocomposites it wasfound that incorporation of polyethylene glycol stabilizedsilver nanoparticles leads to increased intermolecular chargehopping that results in enhanced electrical conductivity ofthe nanocomposites. TGA and DSC results indicated greaterthermal stability for the nanocomposites along with highercrystallinity. A study of spreading resistance of the materi-als, done using scanning spreading resistance microscope,revealed localized sites of high and low conductivity withinthe polyaniline. The low conducting sites were fewer in thecase of nanocomposites.

Keywords Polyaniline nanocomposite . Ultrasound . Silvernanoparticle . Electrical conductivity . Spreading resistance

Introduction

Polyaniline (PAni) has been the subject of enormous interestdue to its reversible doping/dedoping character and modifi-able electrical conductivity that is found to be dependent onits molecular weight [1, 2], type of dopant [3] and pH of themedium [4]. These also results in microstructural changes inPAni, which have a pronounced effect on the polymersphysical and chemical properties [5, 6]. Chen CH has stud-ied the morphological changes in PAni by variation indopant [7]. Microstructural changes in PAni arising fromsynthetic method have also been reported by Zuev VV [8].Apart from changes in synthetic methods in terms of dop-ants and oxidants, nanocomposites of PAni with noble met-als like silver, gold and platinum [9, 10] have also beeninvestigated in an attempt to increase the stability and con-ductivity of the material. Silver, in particular, has been thechoice of metal for many because of its wide range ofapplications in biomedical, industrial and electronics. Suchnanocomposite systems have the potential for applicationsin rechargeable batteries [11], printed circuit boards [12],sensors [13], biological templates [14], as supercapacitors[15] and in electromagnetic interference (EMI) shielding[16, 17]. However, an understanding of structurepropertycorrelation is crucial to application of these materials in realdevices. Mishra et al. have already reported the effect ofmicrostructure on the physical properties of commercialpolymers [1831]. In the present study, we investigated theeffect of incorporated silver nanoparticles on polyanilinesmicrostructure, and consequently on its thermal and electri-cal properties. Numerous methods can be found in literaturefor introduction of silver nanoparticles into the polyanilinematrix [1, 3235]. We report a facile, in-situ preparation ofpolyaniline/silver nanocomposite systems assisted by ultra-sound. The silver nanoparticles were stabilized by polyeth-ylene glycol (PEG). Structural characterization was done by

S. Mishra (*) :N. G. Shimpi : T. SenUniversity Institute of Chemical Technology, North MaharashtraUniversity, Post Box No. 80, Jalgaon 425001, Indiae-mail: [email protected]

J Polym Res (2013) 20:49DOI 10.1007/s10965-012-0049-5

FTIR and UV-visible spectroscopy. TGA and DSC wereemployed for the thermal analysis. TEM was used todetermine the size and morphology of the preparednanocomposite, which reveals the effectiveness of ultra-sound in producing nanostructured materials. The electricalconductivity of the nanocomposites was determined usingfour-point probe technique and scanning spreading resistancespectroscopy (SSRM). The SSRM provided a newer perspec-tive for evaluating the electrical properties of PAni/Agnanocomposites.

Experimental

Materials

Analytical grade aniline and ammonium persulphate(APS) were purchased from Fisher Scientific (Mumbai,India). Silver nitrate was procured from s. d. fine chem-icals ltd. Polyethylene glycol (Mw06,000), sodium bo-rohydride and and N-methyl-2-pyrrolidone (NMP) werepurchased from Qualigens Fine Chemicals, Loba Chemie andMerck (Mumbai, India), respectively. Deionized waterwas used for preparation of all solutions and for washingpurposes.

Synthesis

Aqueous solution of silver nitrate (1.4 mM) with PEG(0.05 gm wt%) was sonicated using an ultrasonic probe(BO3 Ultrasonic Processor UP1200, Cromtech India) for15 min. This was followed by dropwise addition of NaBH4solution, under ultrasound at room temperature. The silvernitrate to NaBH4 mole ratio was kept at 1. The pale greycoloured solution obtained was centrifuged at 20,000 rpmfor 10 min, washed with water and re-dispersed inaniline solution by sonication. Oxidative polymerizationof aniline was carried out by addition of APS with anoxidant to aniline mole ratio of 1.25. The solutions ofboth aniline and APS were prepared in 1 M HCl. Thetemperature of the reaction mixture was maintained at20 C till completion of addition, after which it was leftto stand for 13 h at room temperature (this is not theoptimum time for the reaction to complete, but the onetaken in this experiment). The dark green precipitatewas filtered using Buchner funnel and repeatedlywashed with 1 M HCl solution followed by water untilthe filtrate obtained was colourless. The composite pow-der was first air-dried, and then dried under vacuum at60 C for 6 h.

Eight separate batches of PAni/Ag composites were pre-pared in which the silver content in the composites werevaried by weight as 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75 and

2 wt.%. Pure polyaniline was also prepared which isdenoted as 0 wt.% in the text. Pure polyaniline and itscomposites were all in emeraldine salt form.

Characterization

Fourier transform infrared (FTIR) spectroscopy

Fourier transform infrared (FTIR) spectra of pure PAniand its composites were recorded on FTIR-8400 spec-trophotometer (Shimadzu, Tokyo, Japan) within thewave number range of 4004,000 cm1. The sampleswere prepared in the pellet form by mixing with potas-sium bromide.

Transmission electron microscopy

A transmission electron microscope (TEM) (PhilipsCM200, The Netherlands) was used to assess the morphol-ogy and size of PAni and its composites at a resolution of2.4 A. The samples were dispersed in water and depositedon a copper grid before viewing under the microscope.

UV-visible spectroscopy

UVvis absorption spectra of the samples dissolved inNMP were recorded on a Double Beam UV 1800 spec-trophotometer (Shimadzu, Tokyo, Japan) in the range of2001,000 nm.

Thermogravimetric analysis

The TGA experiment was performed under nitrogen gaspurge (50 ml/min.) over a temperature range of 30600 Cat a heating rate of 10 C/min. on a TGA50 thermogravi-metric analyzer (Shimadzu, Tokyo, Japan).

Differential scanning calorimetry

Phase transitions were investigated over the range of 35300 C at 10 C/min. heating rate under nitrogen atmosphereon a DSC60 differential scanning calorimeter (Shimadzu,Tokyo, Japan).

Electrical conductivity measurements via four-point probemethod

The conductivity of pure PAni and composite sampleswere measured by four-point probe method on pelletscompressed to a thickness of about 1 mm at 500 MPawith a hydraulic press, using a current source (CCS-01)and microvoltmeter (DMV-001) from Scientific Equip-ments, Roorkee, India. The variation in electrical

49, Page 2 of 10 J Polym Res (2013) 20:49

conductivity with temperature was also studied. A PIDcontrolled oven (PID-200) was used for simultaneous heatingof the pellets.

Scanning spreading resistance microscopy (SSRM)

Spreading resistance studies were done on sample films castfrom NMP on glass substrates using Solver Pro 47 atomicforce microscope (NTMDT, Moscow, Russia) and Novasoftware. The AFM was operated in scanning spreadingresistance microscope (SSRM) mode by measuring the localresistance over the sample surface using a TiN coated con-ducting probe.

Results and discussion

Mechanism of nanocomposite formation by ultrasoundinduced cavitation

Figure 1 presents a pictorial representation of scheme ofevents involved in nanocomposite formation. Ultrasoundassisted synthesis relies on cavitation mechanism to obtainnanostructured materials. Cavitation refers to the formation,growth and collapse of bubbles due to transmission ofacoustic waves through a medium which ruptures the mo-lecular structure of the medium (Fig. 1a). During cavitation,bubbles grow due to the diffusion of solute vapour into it.

Fig. 1 Pictorial representationof (a) cavitation, b nucleigrowth due to bubble collapse,c encapsulation of silvernanoparticles by PEG and (d)incorporation of silvernanoparticles betweenpolyaniline chains

J Polym Res (2013) 20:49 Page 3 of 10, 49

When non-volatile solutes are present in the liquid, as is thepresent case, they get concentrated at the interface wherethey react with the high energy species and nucleationbegins. On reaching its maximum size the bubble undergoes

implosive collapse resulting in the solution attaining veryhigh temperature (up to about 24,000 K) along with veryhigh cooling rate [36]. At such fast kinetics the growth ofthe nuclei is hindered (Fig. 1b) and consequently, nanosized

Fig. 2 TEM micrograph ofpure PAni (0 wt.%), PAni/Agnanocomposites (0.252 wt.%)and silver nanoparticles withSAED pattern (inset)


silver particles are formed. These nanoparticles have a largenumber of dangling bonds on their surface. For surfacestability bond formation is necessary which leads to growthof nuclei. But when the growth is stopped prematurely, thestabilization of the silver nanoparticles occur throughbond formation with PEG present in the solution. Theadsorbed PEG layer on the surface of nanoparticle actsas a diffusion barrier to growth species providing sur-face stability, and in the process prevents aggregation, asshown in Fig. 1c.

Further into the process, nanocomposites were preparedby incorporation of these PEG coated silver nanoparticlesinto the polyaniline matrix. When polymerization of anilinewas done it was observed that after about 20 min of soni-cation the solution started to turn green. This indicated theformation of polyaniline. Due to its chain formatting ability,polyaniline shows propensity towards directional growthwhich lends it nanofibrillar morphology. When silver nano-particles are present in the monomer solution, the nucleationtakes place on the surface of the nanoparticles as well,followed by anisotropic growth of polyaniline, and thenanoparticles get incorporated into the polymer (Fig. 1d).

Size and morphological study by transmission electronmicroscopy

Figure 2 presents the TEM micrographs of pure PAni, PAni/Ag (0.252 wt.%) nanocomposites and silver nanoparticles.Plate-like, nanosized silver with dimension of about 50 nm35 nm was formed in all the nanocomposite systems. Thesenon-aggregated silver nanoparticles were uniformly dispersedand embedded into the polymer matrix. Nanofibrillar mor-phology of polyaniline with diameter of about 905 nm canbe seen. At times, association between PEG coated silvernanoparticles arise due to polymer-polymer interaction. Thiswas, however, not seen in the nanocomposites since the pres-ence of ultrasound leads to uniform dispersion of nanopar-ticles in the medium, as evident from the micrograph. Theselected area electron diffraction (SAED) pattern of silvernanoparticles is also presented in Fig. 2. The planes (222),(400) and (331) corresponding to the halo rings can beindexed to that of face-centered cubic (fcc) structure of me-tallic silver [37]. It is thus clear that PEG encapsulation ofsilver nanoparticles prevented their oxidation. From the TEMresults it is evident that ultrasound induced cavitation pro-duced nanostructured systems, with PEG encapsulation result-ing in non-aggrgated, metallic silver nanoparticles.

Functional group identification by FTIR spectroscopy

The successful formation of polyaniline in all cases is evi-dent from fourier transform infrared spectra shown in Fig. 3.The main peaks (framed in red) that were observed are the

ones at 1,552 cm1 and 1,504 cm1, which can be assignedto quinoid and benzenoid ring stretching. The presence ofthese peaks shows the aromatic structure of PAni [38]. Theabsorbance peaks at 3,593 cm1 and 2,964 cm1 corre-sponds to N-H and C-H stretching vibrations, respective-ly. The band at 1,259 cm1 can be associated with bi-polaron structure related to C-N bond stretching of second-ary aromatic amine, while the band at 830 cm1 can beattributed to aromatic out-of-plane C-H bending [3, 39].Doping of PAni brings about a structural change, as can be

Fig. 3 FTIR spectra of pure PAni (0 wt.%) and PAni/Ag nanocompo-sites (0.252 wt.%). The framed peaks show the aromatic structure ofpolyaniline and its nanocomposites


seen from the shifting of bands towards longer wavelengthin Fig. 4 [40]. It also indicates an intimate interaction be-tween the nano silver and the nitrogen sites of the PAnichain. The higher intensity of peaks in the case of nano-composite systems indicates a greater conjugation length,which in turn is responsible for increased conductivity.

UV-visible spectroscopy studies

The UV-visible spectra of pure PAni and its nanocompositesystems recorded in NMP are shown in Fig. 5. Characteristic

peaks of doped polyaniline were observed at about 304 nmand 980 nm, arising due to -* and polaron transitions,respectively [41]. PAni shows an extended conformation inNMP in which the defects arising due to twisting of polymerchain are removed. Hence a strong interaction between theadjacent polarons takes place. This leads to the polaron bandbecoming more delocalized and, as a result, appearing at alonger wavelength with a decrease in exciton absorptionenergy [42]. It has been reported by Zheng et al. thatsample with smaller localized polaron peak has higherconductivity [43].

A peak around 370 nm indicates the presence ofsilver nanoparticles. This plasmon resonance peak forplate-like silver nanoparticles is because of the out-of-plane dipole resonance [44]. An inconclusive broadhump around 560 nm is observed. Generally, a peakaround this wavelength is due to the in-plane dipole ofsilver nanoparticles, but the absence of this peak insome of the nanocomposite samples rule this out. Theappearance of this slight hump can thus be attributed tothe presence of some impurity.

Fig. 6 TGA thermogram of pure PAni (0 wt.%) and PAni/Ag nano-composites (0.252 wt.%)

Fig. 7 DSC thermogram of pure PAni (0 wt.%) and PAni/Ag nano-composites (0.252 wt.%)

Fig. 5 UV-visible spectra of pure PAni (0 wt.%) and PAni/Ag nano-composites (0.252 wt.%)

Fig. 4 FTIR spectra of doped PAni and undoped PAni


Thermal analysis of polyaniline and its nanocomposites

Figure 6 shows the TGA thermogram for pure PAni andPAni/Ag nanocomposites in N2 atmosphere. Complete de-composition of material did not take place since some ma-terial was left in the pan even after 600 C. Three steps ofweight loss were seen during the heating cycle of all thesamples. Weight loss between 70 C and 100 C could beattributed to loss of adsorbed water. The second step at 220300 C could be due to loss of dopant molecules. The finalweight loss within 470600 C is associated with decom-position of PAni chain [45]. As can be seen from thethermogram, for the same onset temperature of decomposi-tion the weight loss in the samples due to degradation ofpolymer backbone is significantly reduced with increasingsilver content. While pure polyaniline shows a weight lossof about 60 %, PAni/Ag nanocomposites containing 1 wt.%and more nano silver shows a decrease of about 25 % intotal weight loss. It can be assumed that the PEG encapsu-lated nano silver are able to interact with polyaniline chains.And though weaker in nature, at nanoscale the total energyof these interacting forces can be quite large to overcome.This prevents complete degradation of polymer backbone.Consequently, lower weight loss is observed for sampleswith higher nano silver content. Since PEG is present in avery small quantity, hence weight loss associated with PEGis absent in the nanocomposites.

Phase transitions in PAni and PAni/Ag nanocompositeswere studied using DSC. From the thermogram (Fig. 7), anincrease in heat of fusion (Hf) was seen with increasingcontent of nano silver which indicates a greater crystallinityof the nanocomposites. This explains the decreased weight

loss in nanocomposites. Table 1 presents the Hf values andpercentage weight loss of polyaniline and its nanocompo-sites. Greater crystallinity of samples was observed forhigher nano silver content, which significantly improvedthe thermal stability of the nanocomposite systems. Nanosilver content of 1.75 and 2 wt.% shows almost the sameweight loss though the crystallinity of the latter is somewhathigher. This indicates that 1.75 wt.% might be the optimumamount of silver nanoparticles that can provide maximuminteraction between PEG and polyaniline chains.

Study of electrical conductivity of PAni and PAni/Agnanocomposites

Four probe Van der Pauw technique [46] was employed tomeasure the electrical conductivity of the sample pellet. Thefollowing equation was used in determining the conductivity:

1 o G7 W S= f g= = :Here, is the conductivity (S/cm), o is the resistivity, W

is the thickness of the pellets, S is the probe spacing and G7is the correction factor. The electrical conductivity of purePAni and PAni/Ag nanocomposite systems, measured as afunction of temperature, is depicted in Fig. 8. All the sam-ples have almost same electrical conductivity at room tem-perature; conductivity of samples with nano silver content of1 wt.% and above is slightly higher than the rest. Anincreasing trend in electrical conductivity was seen whenthe samples are heated from room temperature to 150 C.This confirms the semiconducting nature of the samples.Nanocomposites with 0.50.75 wt.% nano silver contentshows a marginal increase in conductivity with temperature.

Table 1 Weight loss and heat of fusion data for PAni and PAni/Ag nanocomposites

Ag content in PAni (wt %) 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2

Heat of fusion, Hf (J/g) 269.45 314.57 330.10 367.60 376.45 393.77 587.05 626.90 683.03

Weight loss (%) 60.08 51.61 47.58 38.21 35.27 34.30 33.75 32.51 32.73

Fig. 8 Variation in electrical conductivity of pure PAni (0 wt.%) andPAni/Ag nanocomposites (0.252 wt.%) with temperature

Fig. 9 Mechanism of intramolecular charge transfer and intermolecu-lar charge hopping in PAni/Ag nanocomposites


A marked increase in conductivity is observed in nanocom-posites containing 12 wt.% nano silver when heated above100 C which almost levels off at 150 C. Now, althoughsilver has the highest electrical conductivity in bulk state, atnanoscale it turns into a semiconductor. This is becausemore energy states are lost due to the shrinking size result-ing in an increase in the band gap (Eg). Moreover, surfacepassivation of nano silver by PEG compromises its conduc-tivity. Despite this, an increase in electrical conductivity isseen with increasing content of nano silver. As stated inSection Thermal analysis of polyaniline and its nanocomposites, there is interaction between PEG on the surface ofsilver nanoparticles and polyaniline. This decreases the in-termolecular distance which promotes charge hopping. Thishas been depicted in Fig. 9. It has been reported that theincreased intramolecular conductivity is a result of the moreexpanded coil-like conformation of PAni chains, while theincreased intermolecular conductivity is because of thehigher crystallinity of PAni [47]. At nano silver content of1 wt.% and more, the polyaniline chains are close enough toenable intermolecular charge hopping. The intramolecularcharge transfer, on the other hand, takes place at the amor-phous regions of the PAni chain. Hence, it can be reasonablyproposed that the increased conductivity of the PAni/Agnanocomposites is due to the enhanced intermolecular

charge hopping. The two mechanism combined contributestowards increasing the overall conductivity of the material.

It was also observed that beyond 150 C there is virtuallyno increment in conductivity. Moreover, a drop in conduc-tivity was observed when samples were heated beyond200 C, which is due to loss of dopant molecules.

Spreading resistance studies of localized conducting phasesin PAni and PAni/Ag nanocomposites

Scanning spreading resistance microscopy is a very efficientmode of AFM for materials characterization in terms of localresistance. A bias voltage is applied to a conducting probe incontact with the sample surface, and the resulting current flowthrough the sample is measured as a function of the probe withsimultaneous surface topography measurements. Assumingthat there is a constant contact between the probe and thesurface, for a given bias voltage the magnitude of the mea-sured current flow is proportional to local resistance of thesample under investigation. Figure 10 shows the image forcurrent signal of pure PAni (10a) and PAni/Ag nanocompositeat 2 wt.% nano silver content (10b). The lighter areas in thesignal image correspond to higher conductivity. The denserareas, as seen in Fig. 11, corresponds to sites with very lowelectrical conductivity, and are fewer in 2 wt.% (Fig. 11b) than

Fig. 10 Current signal imageof (a) pure PAni (0 wt.%) and(b) PAni/Ag nanocomposites at2 wt.% nano silver content

Fig. 11 Current signal imageof (a) pure PAni (0 wt.%) and(b) PAni/Ag nanocomposites at2 wt.% showing localizedconducting and non-conductingphases


in 0 wt.% (Fig. 11a). It indicates that the ultrasound assistedsynthesis of polyaniline/silver nanocomposite leads to uni-form dispersion of silver nanoparticles. This corroborates thatthe interaction between PAni chains and PEG coated silvernanoparticles increases the crystallinity of PAni and also pro-motes intermolecular charge hopping; the latter contributestoward increasing the conductivity of polyaniline. Since theregion of high conductivity are localized, only a minor in-crease in the electrical conductivity of polyaniline is seen onincorporation of PEG coated silver nanoparticles.

Conclusion

The acoustic cavitation mechanism is found to be effective inproducing nanostructured materials. Nanocrystalline silverwith fcc structure that are formed in presence of ultrasoundare encapsulated by polyethylene glycol which prevents theiroxidation and aggregation, and is conducive to their evendispersion within the polyaniline matrix. The presence ofplasmon resonance band confirms the presence of silver inthe nanocomposites. Incorporation of silver nanoparticles leadsto interaction between the PEG coated nano silver and thenitrogen in the PAni chain. This interaction renders the PAni/Ag nanocomposites thermally more stable and increases theelectrical conductivity of polyaniline. Since the intermoleculargap is decreased at higher nano silver content, charge hoppingbetween the PAni chains gets enhanced. The increment inelectrical conductivity is a result of this enhanced intermolec-ular charge hopping that is brought about by incorporation ofPEG coated silver nanoparticles. Spreading resistance studiesof pure PAni and PAni/Ag nanocomposites were done. It wasfound that polyaniline consists of interspersed high and lowconducting phases. It is because of this that the nanocompositesystems could not achieve very high electrical conductivity.Overall, the incorporation of PEG encapsulated silver nano-particles was found to impart higher thermal stability to poly-aniline, along with enhanced electrical conductivity.

Acknowledgments One of the authors (T. Sen) is thankful to theUniversity Grants Commission, New Delhi, India for providing finan-cial support under the RFSMS scheme. We are also thankful to theSophisticated Analytical Instrumentation Facility (SAIF), IIT Bombayfor transmission electron microscopy characterizations.

References

1. Jing X, Wang Y, Wu D, Qiang J (2007) Sonochemical synthesis ofpolyaniline nanofibers. Ultrason Sonochem 14:7580

2. Shukla SK, Bharadvaja A, Tiwari A, Pilla S, Parashar GK, DubeyGC (2010) Synthesis and characterization of highly crystallinepolyaniline film promising for humid sensor. Adv Mat Lett1:129134

3. Su B, Ton Y, Bai J, Lei Z, Wang K, Mu H, Dong N (2007) Aciddoped polyaniline nanofibers synthesized by interfacial polymeri-zation. Indian J Chem 46:595599

4. Konyushenko EN, Trchov M, Stejskal J, Sapurina I (2010) Therole of acidity profile in the nanotubular growth of polyaniline.Chem Pap 64:5664

5. Mo Z, Qiu W, Yang X, Yan J, Gu Z (2009) Morphologicalcharacterization and kinetics study of Polyaniline film formationby emulsion polymerization. J Polym Res 16:3943

6. Prathap MUA, Srivastava R (2011) Morphological controlled syn-thesis of micro-/nano-polyaniline. J Polym Res 18:24552467

7. Chen CH (2002) Thermal studies of polyaniline doped withdodecyl benzene sulfonic acid directly prepared via aqueous dis-persions. J Polym Res 9:195200

8. Zuev VV (2008) Synthesis of polyanilines with pendant fluores-cent units. J Polym Res 15:351356

9. Qiu W, Huang H, Zeng S, Xue T, Liu J (2011) A kinetic study ofinsitu polyaniline-gold composite film formation. J Polym Res18:1923

10. Barkade SS, Naik JB, Sonawane SH (2011) Ultrasound assistedminiemulsion synthesis of polyaniline/Ag nanocomposite andits application for ethanol vapor sensing. Colloids Surf A 378:9498

11. Mathai CJ, Saravanan S, Anantharaman MR, Venkatachalam S,Jayalekshmi S (2002) Characterization of low dielectric constantpolyaniline thin film synthesized by ac plasma polymerizationtechnique. J Phys D Appl Phys 35:240245

12. Wessling B, Thun M, Arribas-Sanchez C, Gleeson S, Posdorfer J,Rischka M, Zeysing B (2007) An Organic Metal/SilverNanoparticle Finish on Copper for Efficient Passivation andSolderability Preservation. Nanoscale Res Lett 2:455460

13. Chaudhary A (2009) Polyaniline/silver nanocomposites: dielectricproperties and ethanol vapour sensitivity. Sens Actuators B138:318325

14. Reddy KR, Sin BC, Ryu KS, Noh J, Lee Y (2009) In situ self-organization of carbon blackpolyaniline composites from nano-spheres to nanorods: Synthesis, morphology, structure and electri-cal Conductivity. Synth Met 159:19341939

15. Sahoo S, Karthikeyan G, Nayak GC, Das CK (2012) Modifiedgraphene/polyaniline nanocomposites for supercapacitor applica-tion. Macromol Res 20:415421

16. Liu CH, Yu X (2011) Silver nanowire-based transparent, flexible,and conductive thin film. Nanoscale Res Lett 6:75

17. Perkas N, Amirian G, Rottman C, de la Vega Gedanken F (2009) ASonochemical deposition of magnetite on silver nanocrystals.Ultrason Sonochem 16:132135

18. Mishra S, Shimpi NG, Mali AD (2011) Investigation of Photo-oxidative effect on morphology and degradation of mechanical andphysical properties of nano CaCO3 silicone rubber composites.Polym Adv Technol. doi:10.1002/pat.1861

19. Mishra S, Shimpi NG, Mali AD (2011) Influence of nano inorgan-ic particles on properties of epoxy nanocomposites. Polym PlastTechnol Eng 50:758761

20. Mishra S, Shimpi NG, Mali AD (2011) Influence of stearic acidtreated nano CaCO3 filler on properties of silicone nanocompo-sites. J Polym Res 18:17151724

21. Mishra S, Shimpi NG, Mali AD (2012) Surface modification ofmontomorillonite (MMT) using column chromatography tech-nique and its application in silicone rubber nanocomposites.Macromol Res 20:4450

22. Mishra S, Sonawane SH, Singh RP (2005) Studies on character-ization of nano CaCO3 prepared by the in situ deposition tech-nique and its application in PPnano CaCO3 composites. J PolymSci Part B Polym Phys 43:107113

23. Mishra S, Shimpi NG (2005) Mechanical and flameretardingproperties of styrenebutadiene rubber filled with nanoCaCO3


as a filler and linseed oil as an extender. J Appl Polym Sci98:25632571

24. Mishra S, Sonawane SH, Badgujar N, Gurav K, Patil D (2005)Comparative study of the mechanical and flameretarding proper-ties of polybutadiene rubber filled with nanoparticles and fly ash. JAppl Polym Sci 96:69

25. Mishra S, Mukherji A (2007) Phase characterization and mechan-ical and flameretarding properties of nanoCaSO4/polypropyleneand nanoCa3 (PO4) 2/polypropylene composites. J Appl PolymSci 103:670680

26. Mishra S, Shimpi NG (2007) Studies on mechanical, thermal, andflame retarding Properties of Polybutadiene Rubber (PBR)Nanocomposites. Polym Plast Technol Eng 47:7281

27. Mishra S, Sonawane S, Mukherji A, Mruthyunjaya HC (2006)Effect of nanosize CaSO4 and Ca3 (PO4) 2 particles on therheological behavior of polypropylene and its simulation with amathematical model. J Appl Polym Sci 100:41904196

28. Mishra S, Mukherji A, Sonawane SH, Sharma DK (2006)Nonisothermal Crystallization Modeling and Simulation ofPolypropylene/Nano Ca3(PO4)2 Composites with Variation inWt.% of Loading and Reduction in Nanosize. Polym PlastTechnol Eng 45:641651

29. Sonawane SS, Mishra S, Shimpi NG, Rathod AP, Wasewar KL(2010) Comparative study of the mechanical and thermal proper-ties of polyamide-66 filled with commercial and nano-Mg (OH) 2particles. Polym Plast Technol Eng 49:474480

30. Mishra S, Chatterjee A (2011) Effect of nanopolystyrene (nPS)on thermal, rheological, and mechanical properties of polypropyl-ene (PP). Polym Adv Technol 22:15471554

31. Rana VK, Pandey AK, Singh RP, Kumar B, Mishra S, Ha CS(2010) Enhancement of thermal stability and phase relaxationbehavior of chitosan dissolved in aqueous l-lactic acid: Usingsilver nanoparticles as nano filler. Macromol Res 18:713720

32. Kowsari E, Faraghi G (2010) Ultrasound and ionic-liquid-assistedsynthesis and characterization of polyaniline/Y2O3 nanocompositewith controlled conductivity. Ultrason Sonochem 17:718725

33. Jing S, Xing S, Yu L, Wu Y, Zhao C (2007) Synthesis andcharacterization of Ag/polyaniline coreshell nanocompositesbased on silver nanoparticles colloid. Mater Lett 61:27942797

34. Gedanken A (2007) Doping nanoparticles into polymers andceramics using ultrasound radiation. Ultrason Sonochem 14:418430

35. Sonawane SH, Chaudhari PL, Ghodke SA, Parande MG, BhandariVM, Mishra S, Kulkarni RD (2009) Ultrasound assisted synthesisof Polyacrylic Acid-Nanoclay nanocomposite and its application insonosorption studies of Malachite Green dye. Ultrason Sonochem16:351355

36. Gedanken A (2004) Using sonochemistry for the fabrication ofnanomaterials. Ultrason Sonochem 11:4755

37. Khan MAM, Kumar S, Ahamed M, Alrokayan SA, AlSalhi MS(2011) Structural and thermal studies of silver nanoparticles andelectrical transport study of their thin films. Nanoscale Res Lett6:434

38. Jang J, Ha J, Kim S (2007) Fabrication of polyaniline nanoparticlesusing microemulsion polymerization. Macromol Res 15:154159

39. Dai L, Wang Q, Wan M (2000) Direct observation of conforma-tional transitions for polyaniline chains intercalated in clay par-ticles upon secondary doping. J Mater Sci Lett 19:16451647

40. Brozova L, Holler P, Kovarova J, Stejskal J, Trchova M (2008)The stability of polyaniline in strongly alkaline or acidic aqueousmedia. Polym Degrad Stabil 93:592600

41. Nabid MR, Golbabaee M, Moghaddam AB, Dinarvand R, SedghiR (2008) Polyaniline/TiO2 nanocomposite: enzymatic synthesisand electrochemical properties. Int J Electrochem Sci 3:11171126

42. Feng J, MacDiarmid AG, Epstein AJ (1997) Conformation ofpolyaniline: effect of mechanical shaking and spin casting. SynthMet 84:131132

43. Zheng W, Min Y, MacDiarmid AG, Angelopoulos M, Liao YH,Epstein AJ (1997) Effect of organic vapors on the molecularconformation of non-doped polyaniline. Synth Met 84:6364

44. Pal S, Tak YK, Song JM (2007) Does the antibacterial activity ofsilver nanoparticles depend on the shape of the nanoparticle? Astudy of the gram-negative bacterium Escherichia coli. ApplEnviron Microbiol 73:17121720

45. Bhadra S, Khastgir D (2008) Extrinsic and intrinsic structuralchange during heat treatment of polyaniline. Polym DegradStabil 93:10941099

46. Zhang D (2007) On the conductivity measurement of polyanilinepellets. Polym Test 26:913

47. Xia Y, Wiesinger JM, MacDiarmid AG, Epstein AJ (1995)Camphorsulfonic acid fully doped polyaniline emeraldine salt:conformations in different solvents studied by an Ultraviolet/Visible/Near-Infrared Spectroscopic Method. Chem Mater 7:443445


The...AbstractIntroductionExperimentalMaterialsSynthesisCharacterizationFourier transform infrared (FTIR) spectroscopyTransmission electron microscopyUV-visible spectroscopyThermogravimetric analysisDifferential scanning calorimetryElectrical conductivity measurements via four-point probe methodScanning spreading resistance microscopy (SSRM)

Results and discussionMechanism of nanocomposite formation by ultrasound induced cavitationSize and morphological study by transmission electron microscopyFunctional group identification by FTIR spectroscopyUV-visible spectroscopy studiesThermal analysis of polyaniline and its nanocompositesStudy of electrical conductivity of PAni and PAni/Ag nanocompositesSpreading resistance studies of localized conducting phases in PAni and PAni/Ag nanocomposites

ConclusionReferences

the effect of peg encapsulated silver

Documents