Redox properties of nanostructured aniline oxidation products formed under different pH conditions

A series of aniline oxidation products were produced from the chemical oxidation of aniline by ammonium persulphate under constant pH STAT conditions (pH 1 to 7). Regular granular polyaniline was obtained in the samples prepared at pH 1 to 3, with moderate to high conductivities. The presence of polyaniline was also indicated in a further sample prepared under 'falling pH' conditions. The samples prepared at pH 4 to 7 were all of a very low conductivity, while their BET surface areas were a little lower than the pH 1 sample. However, all of the samples showed a similar high ability to scavenge DPPH radicals. This oxidisability was related to oxidation and reduction peaks seen in cyclic voltammograms in 0.1 M HCl of powders dispersed on a glassy carbon electrode. With the pH 4 to 7 samples, a single oxidation peak was seen in the voltammograms at a low potential (c. 0.12 V (Ag/AgCl)), in contrast to the multiple peaks for samples with a regular polyaniline structure.