Polyaniline (PANI) nanostructures with a high conductivity (10-2~10-1 S/cm) were synthesized by template-free method in the presence of different kinds of ferric salts

such as FeCl3

Fe(NO3)3

Fe2(SO4)3

FePO4 as oxidants.The ferric salts

acting as strong acidic salts

will produce protons via hydrolysis

which could be used as dopant for PANI.The nanostructures characterized by FTIR

UV-Visible absorption and XRD spectra are identical to the emeraldine salt state of PANI.This method is more simple and cheap because ferric salts could act as both oxidant and dopant at the same time

resulting in omitting external dopant.Moreover

the resulting nanostructures show thinner diameter and higher crystallinity than those of the nanofiers oxidized by ammonium persulfate (APS) perhaps due to the low redox potential of ferric salts.It is found that the ratios of oxidant to aniline affected strongly the morphology and conductivity of PANI.The counter-anions have some influences on the PANI morphology

however have little effects on the structure and properties of PANI.