The oxidation of aniline with silver nitrate to polyaniline–silver composites

Silver nitrate oxidizes aniline in the solutions of nitric acid to conducting nanofibrillar polyaniline. Nanofibres of 10–20 nm thickness are assembled to brushes. Nanotubes, having cavities of various diameters, and nanorods have also been present in the oxidation products, as well as other morphologies. Metallic silver is obtained as nanoparticles of ∼50 nm size accompanying macroscopic silver flakes. The reaction in 0.4 M nitric acid is slow and takes several weeks to reach 10–15% yield. It is faster in 1 M nitric acid; a high yield, 89% of theory, has been found after two weeks oxidation of 0.8 M aniline. The emeraldine structure of polyaniline has been confirmed by FTIR and UV–vis spectra. The resulting polyaniline–silver composites contain 50–80 wt.% of silver, close to the theoretical expectation of 68.9 wt.% of silver. The highest conductivity was 2250 S cm−1. The yield of a composite is lower when the reaction is carried out in dark, the effect of daylight being less pronounced at higher concentrations of reactants.