Surface morphology of the prepared samples was investigated through SEM studies (Fig. 2). It is evident from Figs. 2(a) and (b) that PPy nanofibers of diameters about 63 and 51 nm are formed in the presence of HCl and HNO3, respectively. The PPy nanofibers formed in the presence of HCl (A1) are quite uniform and longer than the nanofibers prepared with HNO3 (A2), whereas, agglomerated structures without any definite shape and size have been observed with HClO4 (A3) and H2SO4 (A4). This indicates that the shape and size of the nanostructures strongly depend on the type of acidic media or their acidic character [10, 15-17]. The acidic character of the acids used is in the order of HClO4 > H2SO4 >HCl >HNO3, and the nanofibers were formed with lower strength acids (HCl, HNO3). Stamenov et al. [10] also observed acid dependent surface morphology of polyaniline in the presence of these acids. They observed smooth nanofibers with HCl but some globular structures along with some fibular structures were observed in the H2SO4 medium.
Fig. 3 shows the FTIR spectra of all the prepared samples (A1–A4) comprising of all the characteristic bands of PPy. The N–H stretching vibration band of PPy is observed at ~3434 cm-1 in the samples A1 and A4 which shifts towards lower wavenumbers side at ~3404 and 3412, in the sample A2 and A3, respectively [4,8,18,19]. In the sample A3, one more significant band is present at ~3126 cm-1, which may be attributed to O–H group. The doublet observed at ~2855 and ~2926 cm-1 in all the spectra is attributed to C-H stretching vibration mode of methyl and methylene group, respectively. Along with this doublet, one more band at ~2950-2958 cm-1 is observed in all the samples which can be ascribed to C-...
... middle of paper ...
.... Soc. 112 (1990) 1757-1768.
[33]. H. Yoon, M. Chang, J. Jang, Sensing behavior of polypyrrole nano tubes prepared in reverse micromulsions: effects of tranducers size and transduction mechanism, J. Phys. Chem. B 110 (2006) 14074-14077.
[34]. N. T. Kemp, A. B. Kaiser, H. J. Trodahl, B. Chapman, R. G. Buckley, A.C. Partridge, P. J. S. Foot, Effect of ammonia on the temperature-dependent conductivity and thermopower of polypyrrole, J. Polym. Sci., Part B: Polym. Phys. 44, 1331 (2006).
[35]. H. Kate, O. Nisbikawa, T. Matsui, S. Honmal, H. Kokado, Fourier transform infrared spectroscopy study of conducting polymer polypyrrole: higher order structure of electrochemically synthesized film, J. Phys. Chem. 95 (1991) 6014-6016.
[36]. F.W. Zeng, X.X. Liu, D. Diamond, K.T. Lau, Humidity sensors based on polyaniline nanofibers, Sens. Actuators B 143 (2010) 530–534.