Optical band gap and conductivity measurements of polypyrrole-chitosan composite thin films

Abstract

Electrical conductivity and optical properties of polypyrrole-chitosan (PPy-CHI) conducting polymer composites have been investigated to determine the optical transition characteristics and energy band gap of composite films. The two electrode method and I–V characteristic technique were used to measure the conductivity of the PPy-CHI thin films, and the optical band gap was obtained from their ultraviolet absorption edges. Depending upon experimental parameter, the optical band gap (Eg) was found within 1.30–2.32 eV as estimated from optical absorption data. The band gap of the composite films decreased as the CHI content increased. The room temperature electrical conductivity of PPy-CHI thin films was found in the range of 5.84 × 10−7–15.25 × 10−7 S·cm−1 depending on the chitosan content. The thermogravimetry analysis (TGA) showed that the CHI can improve the thermal stability of PPy-CHI composite films.