Development of polyaniline sensor for sulfurdioxide detection

Abstract

Polyaniline emeraldine base (EB) powder, which is the nonconductive form of polyaniline, was synthesized by chemical oxidative polymerization using ammonium peroxydisulfate as an oxidant. In this work, EB solution prepared by dissolving EB powder in N-methypyrrolidone was converted to emeraldine salt solution (conductive form) using the acid doping process. The ES films were prepared by evaporating solvent in order to study the film electrical conductivity. Three different types of acid dopant; hydrochloric acid, eamphorsulfonic acid and ethanesulfonic acid were used to investigate the effect of acid dopant and concentration on the electrical conductivity of polyaniline films. In addition, polyaniline films were exposed to SO2 gas to study the effect of the gas on the electrical conductivity of the films. The electrical conductivity of the CSA-doped polyaniline films increased when exposed to SO2 at 1000 ppm whereas the HCl-doped polyaniline films did not show any response. The electrical conductivity of the CSA-doped polyaniline films varied linearly with doping ratio when exposed to SO2. Furthermore, the percentage change in electrical conductivity after exposure to SO2 gas of CSA-doped polyaniline films increased with SO2 gas concentration.