A nanocomposite of titanium dioxide (TiO2) and polyaniline (PANi) was synthesized by in-situ chemical polymerization using aniline (ANi) monomer and TiCl4 as precursors. SEM pictures show that the nanocomposite was created in the form of long PANi chains decorated with TiO2 nanoparticles. FTIR, Raman and UV-Vis spectra reveal that the PANi component undergoes an electronic structure modification as a result of the TiO2 and PANi interaction. The electrical resistor of the nanocomposite is highly sensitive to oxygen and NH3 gas, accounting for the physical adsorption of these gases. A nanocomposite with around 55% TiO2 shows an oxygen sensitivity of 600–700%, 20–25 times higher than that of neat PANi. The n-p contacts between TiO2 nanoparticles and PANi matrix give rise to variety of shallow donors and acceptor levels in the PANi band gap which enhance the physical adsorption of gas molecules.

An experiment has been carried out to study the formation and characterisation of polyaniline (PANi) nanolayer growth directly on glass and alumina substrate by in situ chemical polymerisation. It has been found that the growth mode of the PANi nanolayer depends on the synthesis time and mechanical agitation. The difference in growth modes results in the form of granular, planar or fibrillar structure and then affects the chemical and electronic structure of the PANi nanolayer. As a result of gas-PANi chain interaction the resistance of the PANi nanolayer is highly sensitive to a variety of gases in environment such as oxygen (oxidising agent), NH 3 (reducing agent) and so forth. The feature enables PANi nanolayer made by in situ chemical polymerisation, a promising candidate for gas sensing materials.