Synthesis, Characterization, Thermal Stability and D.C. Electrical Conductivity of Pani/Pbs Nanocomposite

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1 International Journal of Composite Materials 2013, 3(5): DOI: /j.cmaterials Synthesis, Characterization, Thermal Stability and D.C. Electrical Conductivity of Pani/Pbs Nanocomposite J. B. Bhaiswar 1,*, M. Y. Salunkhe 2, S. P. Dongre 3 1 Department of Physics, Nagpur institute of Technology, Nagpur 2 Department of Physics, Institute of Science, R.T. road, civil line, Nagpur 3 Department of Physics, Bhalerao Science College, Saoner, Nagpur Abstract Nanocomposite of conducting polyaniline with PbS nanoparticles have been synthesized via in situ by oxidizing technique. The effect of PbS nanoparticles on the electrical conductivity and Thermal Stability of polyaniline was discussed. The prepared products were characterized by FT -IR, XRD, Transmission electron Microscopy and TGA-DTA. FTIR absorption band at 415 cm -1 confirmed the concentration of PbS in polyaniline are low. TEM showed the PAni/PbS nanocomposite is in the nanorange.uv-vs ible spectra of PAni/PbS nanocomposite shows the different absorption wavelength. The TGA/DTA thermogram shows increased in thermal stability as compare the pure PAni. The D.C electrical conductivity of polyaniline/pbs nanocomposite increased at (25%) wt (1.66x10-3 S/cm) as compared to the pure polyaniline (10-10 S/cm), and Silicon (10-4 S/cm) semiconductors. Keywords Polyaniline, Thermal, Electrical 1. Introduction The nanocomposites of metal and semiconductor particles have several thermal, optical and electronics applications[1]. Organic inorganic nanocompos ite with an organized structure has been extensively studied because they combine the advantages of the inorganic materials, like (mechanical strength, electrical and magnetic properties and thermal stability) and the organic polymers like (Flexibility, dielectric, ductility and processibility), which are difficult to obtain from individual components[2-4]. PANI is one of the conducting polymers that has potential in the near term, due to its good processability, environmental stability and reversible control of conductivity both by charge-transfer doping and protonation[5-6]. Inorganic semiconductors CdS, ZnS and PbS nanoparticles are the most promising II-VI compound materials used in various applications like sensors, optoelectronic devices and in solar cells [7]. Studies on PANI-CdS, PANI-ZnS and PANI-PbS nanocomposite have been reported by many researchers[8-11] and focused on electrical conductivity, but little is known about the thermal thermal stability of such nanocompos ites. Along with electrical conductivity, thermal stability of the polymers plays important role to modify the polymer properties to be used for advanced applications. Hence thermal stability of conducting PANI and its composites has great importance. * Corresponding author: jitendrabbhaiswar@yahoo.co.in (J. B. Bhaiswar) Published online at Copyright 2013 Scientific & Academic Publishing. All Rights Reserved This paper present d.c electrical conductivity and thermal stability of PANI/PbS nanocomposite using fore probe technique and TGA (thermogram) with different wt % of PbS and also study thermal parameter using DTA analysis. 2. Experimental Part PbS (Aldrich) and aniline (Aldrich) were used after purification. Oxidant Ammonium per sulphate (Aldrich) was used without further purification Synthesis of Polyaniline via Chemical Oxidative Polymerization Polymerization was carried out by the chemical oxidation of aniline in the presence of H 2 SO 4 and APS (Ammonium per-sulphate) in 100ml distilled water both played the role as dopant and oxidant respectively. (0.4mol) APS was dissolved in 100ml distilled water in a four-neck round bottom reaction flask and 0.4mol H 2 SO 4 is also added under mechanical stirring for 2 hours. Aniline (0.4 mol) was stirred with 0.4mol of H 2 SO 4 in 100ml distilled water. The solution of APS in H 2 SO 4 was then added drop-wise in the solution of aniline with vigorous stirring on a magnetic stirrer for 3 hours to initiate the aniline polymerization. The reaction was later carried out at room temperature for 6-7 hours with stirring. A dark green colored PAni suspension was obtained with precipitation. The synthesized PAni was obtained as finely dispersed particles, which were recovered from the polymerization mixture by centrifugation and washed with deionized water repeatedly until the washing liquid was

2 116 J. B. Bhaiswar et al.: Synthesis, Characterization, Thermal Stability and D.C. Electrical Conductivity of Pani/Pbs Nanocomposite completely colourless. Finally, the mixture was filtered using filtered assembly. After keeping overnight, the dark gray colour precipitate was obtained. A precipitate of Polyaniline was dried under at for more than 8 hours Synthesis of PAni-PbS Nanocomposites The synthesis steps of PAni/PbS nanocomposite are similar to the synthesis method of PAni. Different amount of PbS was dispersed into the APS solution and stirred for 1 hour prior to the addition of aniline. Aniline (0.4 mol) stirred with 0.4mol H 2 SO 4 in 100 ml of distilled water were added drop-wised using burette into the APS-PbS solution and stirred vigorously to form homogeneous dispersion. For convenience, PAni Composites were prepared with different weight percentages of PbS i.e. 5%, 10%, 15%, 20% & 25%%. Same synthesis conditions were maintained for all composites as that of pure PAni to compare the result. Characterizations X-RD spectra of all samples were taken on Philips PW 3071, Automatic X-ray diffractometer Using Cu-Kα radiation of wavelength Å, continuous scan of 2 o / min., with an accuracy of 0.01 at 45 KV and 40 ma. Fourier Transform Infra Red (FTIR) spectroscopy (Model: Perkin Elmer 100) of PAni: PbS nanocomposite was studied in the frequency range of cm 1. UV-spectra were recorded in the region nm at a scanning rate of 100 nm min -1 and a chart speed of 5 cm min -1. TGA thermograms of all samples were recorded on Perkin-Elmer Diamond TGA/DTA in argon atmosphere at a heating rate of 10 / min. TGA profile were taken over the temperature range of The electrical conductivity measurement were made using four probe techniques. TEM micrographs of synthesized PAni/PbS were taken on Transmission Electron Microscope PHILIPS model- CM200 with resolution 2.4Å. 3. Result and Discussion 3.1. XRD Analysis Fig. 1. Shows the XRD spectra of pure PAni, Pure PbS and PAni/PbS nanocomposite. The XRD pattern of pure PAni matchable with the JCPDS file no with 2θ=25.12 and d-spacing 3.54Å.A nanocomposite of Pani shows the greater crystallinity due to the addition of PbS in PANI matrix as compared to pure PANI and pure PbS. The crystalline size of the crystalline particle can be determined using Debye Scherer formula 0.9 λ and it is found that the βcosθ grain size of PAni/PbS nanocomposite is (82.10nm). Figure 1. XRD Pattern of pure Pani, pure Pbs and Pani/Pbs nanocomposite

3 International Journal of Composite Materials 2013, 3(5): FT-IR S pectra Figure 2. FT-IR spectra of Pure Pani, Pani/PbS and Pure PbS Fig.2. shows the FT-IR spectrum of pure polyaniline, pure PbS and PAni/PbS nanocomposite, where the % of transmittance is plotted as a function of wave number (cm -1 ). The characteristic FT-IR peak at 1566 and 1485 cm -1 are due to the presence of quinoid and benzenoid rings, respectively and are clear indication of these two states in the polymer chain. Also, The peaks at 1302 cm -1 are due to the C-N bond stretching vibration. The absorption band near 2900 cm -1 is assigned to aliphatic C H stretching of the Polymer. The peak at 819cm -1 attributes due to the para coupled ring while peak at 880 cm -1 represents the deformed vibrational mode of benzene ring, which is caused due to attachment of specific group present on the ring. The FTIR spectra of composite materials are shown in figure. The C=C vibrations of quinoid and benzenoid ring is observed at cm -1 in composites. The peak due to methyl group attached to the phenyl ring is observed at cm -1. The characteristic peaks observed at 1146 cm -1 are due to symmetric stretching vibrations of -SO 3 (polystyrene sulphonic acid). The weak vibration bond at 415 shows that concentration of PbS in the polymer is low TEM Micrograph Figure 3. TEM of Pani/PbS nanocomposite

4 Absorption 118 J. B. Bhaiswar et al.: Synthesis, Characterization, Thermal Stability and D.C. Electrical Conductivity of Pani/Pbs Nanocomposite may be due n π* transition[12]. The UV-visible spectra of PANi/PbS nanocomposite shows the bathochromic shift i.e. the shift towards the longer wavelength in which the value of λmax increases. The absorption peak at 285nm and 768nm in PAni/PbS nanocomposite matches with pure PAni and Pure PbS confirm the formation of nanocomposite. Figure 4. TEM of Pure PbS From the fig 3&4 clear that Pani/PbS nanocomposite and Pure PbS synthesized by chemical oxidation technique are in nanorange with the nanoscale of 60nm and 100nm range respectively with average diameter of 21nm UV-Visible Analysis Fig.5. Shows the UV-spectra of pure PAni, PAni/PbS nanocomposite and Pure PbS were recorded in the region nm at a scanning rate of 100 nm min -1 and a chart speed of 5 cm min -1. The Pure PAni displayed two characteristics broad band s at 285 and 375nm. The band at 375 cm -1 is the less intense band which may be accounted for a π π* transition while the more intense band at 285 nm 3.5. TGA Thermogram Fig 6. shows TG thermogram of pure Pani and Pani/PbS nanocomposite. The TG thermogram of pure Pani shows three major stages for the weight loss up to 800. The first weight loss of 23% at around 120 is due to evaporation of moisture. The second stage of weight loss starting at 150 up to 350 almost 50% substance wt loss which represents the evaporation and degradation of sulphuric acid group and low molecular weight polymers[13]. From 350 onwards, degradation of skeletal PANI Chain structure takes place[14] up to 800 in which almost 93% mass loss is observed. The TGA thermograms of PANI-Pbs nanocomposite containing different weight percentage of PbS are shown in fig.3) respectively. It was observed that PANI-PbS nanocomposite containing 5%, 10%, 15% and 20% and 25% weight of Pbs shows weight loss of 15to 8% at 120 which is less than PANI. Similarly it shows second stage of degradation between Above 300 o C, polymer degradation takes place slowly up to 800 unlike pure PANI which almost degrades at 800. Conclusively, the TGA studies point out the inference that, PANI-PbS nanocomposite are thermally more stable than pure PANI salt pure PbS PANI/PbS nanocomposite pure PANI Wavelength(nm) Figure 5. UV-Spectra of Pure Pani, Pani/PbS and Pure PbS

5 Heat flow % Weight(%) International Journal of Composite Materials 2013, 3(5): % PAni/PbS 10% PAni/PbS 15% PAni/PbS 20% PAni/PbS 25% PAni/PbS Pure PAni Tempreture( 0 C) Figure 6. TGA thermogram of Pani/PbS nanocomposite at different wt(5-25%) 3.6. DTA Analysis % PAni/PbS 10% PAni/PbS 15% PAni/PbS 20% PAni/PbS 25% PAni/PbS Tempreture( 0 C) Figure 7. DTA of PAni/PbS nanocomposite at different wt ratio (5-25%) Table 1. DTA result of PAni/PbS nanocomposite at different wt ratio % nanocomposite Onset temp Peak temp Enthalpy change( H) Area End temp 5% J/g mJ % J/g mj % J/g mj % J/g mj % J/g mj

6 120 J. B. Bhaiswar et al.: Synthesis, Characterization, Thermal Stability and D.C. Electrical Conductivity of Pani/Pbs Nanocomposite Fig. 7. The DSC curve peaks indicates the endothermic process where energy is required to break the bonds in the successive elimination of H 2 O, CO and CO 2. Table.1. shows DTA result of PAni/PbS nanocomposite with different wt % of PbS (5-25%). All nanocomposite has higher peak temperature than 15% nanocomposite. The increased in wt % of PbS in the PAni matrix, no significant effect on peak temperature and enthalpy change. However the onset temperature of PAni/PbS (5-25%) nanocomposite are less than pure PAni(298 0 ) that clearly indicated the thermal stability of PAni/PbS nanocomposite are greater than pure PAni D.C. Electrical Conductivity Log(6)(S/cm)x /T(K -1 ) 5% Pani/PbS 10% Pani/PbS 15% Pani/PbS 20% Pani/PbS 25% Pani/PbS Figure 8. D.C.electrical conductivity of Pani/PbS nanocomposite (5-25%) Fig.8. Shows the variation of electrical conductivity (σ) with increasing doping concentration of PbS into PANi measured according to the standard four point probe method at room temperature. It is observed that the room temperature conductivity of PANi/PbS nanocomposite increases remarkably from 4.10 x 10 5 S/cm (5%) to S/cm (25%) as doping concentration of PbS increased from 5-25 wt%. The conductivity continues to increase with increasing PbS content into PANi/PbS nanocomposite. This may be attributed to the doping effect of PbS which maximizes the number of carriers. FTIR and XRD pattern are demonstrated that PbS nanoparticles had been successfully incorporated into polymer chain. From this result it is believed that intercalation of PbS nanoparticles in polyaniline were helped to increase the conductivity due to enhancement of crystalline o f PbS nanoparticles. The conductiv ity of PbSpolyaniline (1.68x10-3 S/cm) nano-composite was greater than pure polyaniline (10-10 S/cm)[15] and Silicon (10-4 S/cm) semiconductors. 4. Conclusions Polyaniline-CdS nanocomposites have been successfully synthesized via in situ by oxidation polymerization. FT -IR, XRD and UV-Visible spectra demonstrated that the PbS nanoparticles disperse in polymer matrix.tem is clearly indicated that the nanocomposite are in nanorange. Electrical conductivity of Polyaniline PbS nanocomposites was found to be increased when compared to pure Polyaniline due to its increase in crystallinity. TGA/DTA thermogram clearly indicated increased in thermal stability of PAni/PbS nanocomposite at different % of PbS as compared to Pure PAni. REFERENCES [1] Y Wang, Herron N, Photoconductivity of CdS nanoclusterdoped polymers Chemistry and Physics letters, volumn 200, no.1-2, pp.71-75,1992. [2] A.Lagashetty and A. Venkataraman, Resonance, (2005) [3] M. D. Ventra, S. Evoy, J. R. Heflin "Introduction to Nanoscale Science and Technology", Kluwer Academic Publishers, (2004).

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