Keywords: aniline oxidation, chemical oxidation, polyaniline, nanostructures, pH STAT, cyclic voltammetry, surface area, radical scavenging, nanotechnology, redox properties, ammonium persulphate
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.