A facile method for the synthesis of polyaniline nanospheres and the effect of doping on their electrical conductivity

The synthesis of polyaniline (PANI) nanospheres using a simple template-free method is described. The polymerization of aniline in aqueous medium was accomplished using ammonium persulfate without any protonic acid. The UV-visible spectrum of the PANI nanospheres displayed the characteristic absorption peak of the pi-pi* transition of the benzenoid ring at 355 nm. The oxidation state of the PANI nanospheres was identified with Fourier transform infrared spectroscopy by comparing the two bands at 1582 cm(-1) (ring stretching in quinoid unit) and 1498 cm(-1) (ring stretching in bezenoid unit). X-ray diffraction patterns demonstrated the low crystallinity of the PANI nanospheres. Themorphology of the PANI nanospheres was spherical and their mean diameter was found to be in the range 3-12 nm. The thermal behavior of the PANI nanospheres was studied using thermogravimetric analysis. The effect of doping of HCl and H2SO4 on the PANI nanospheres was studied by measuring the current as a function of time of exposure. A high electrical conductivity of 6 x 10(-2) S cm(-1) was obtained for the PANI nanospheres doped with 100 ppm HCl, their optimum doping state. (C) 2011 Society of Chemical Industry