2.2. PANI Film Preparation
Aniline was purified by distilled under vacuum with vigorous stirring to prevent bumping. A PANI dispersion was prepared as a nanofibre using the methods described by Huang and Kaner [29]. The purified aniline (3.2 mmol or 0.3 g) was mixed with 1.0 M HCl acid solution (10 mL). Ammonium peroxydisulfate (0.8 mmol or 0.18 g) was mixed into another aliquot (10 mL) of the acid solution. The aniline-acid solution was added to the oxidant and the two solutions were rapidly mixed for 30 s and then allowed to react undisturbed overnight. The following day, the polyaniline was washed with water and centrifuged. After three washings, the supernatant liquor with a pH of 3.3 and was strongly green in colour, indicating the presence of PANI particles. Before casting, any remaining particles larger than 1 μm were removed by passing the dispersion through a 55-mm glass fiber filter (Whatman GFA, Kent, UK) attached to a vacuum source. The PANI dispersion was cast directly on a polystyrene substrate. Then the thin film of PANI on the polystyrene sheet were left overnight in the dark to dry after which individual 10 mm2 sections were cut. The ready film was then stored at 4 °C. The film thickness was determined by SEM images to be 0.7 μm. The film thickness was routinely determined for film samples to make sure that the thickness was always within in the same order of magnitude. The PANI film of similar thickness (0.7 μm) was selected and used for further experiments for good reproducibility of the PANI film fabrication.