Preparation of poly(o-toluidine)/TiO2 nanocomposite films and application for humidity sensing

Conducting poly(o-toluidine) (POT)/titanium dioxide (TiO2) nanocomposite films have been synthesized by in situ chemical oxidation polymerization of o-toluidine in the presence of TiO2 nanoparticles. The nanocomposite films were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The characterization results confirmed the polymerization of o-toluidine and the strong interaction between POT and TiO2 nanoparticles. The humidity-sensing property of the films was tested by measuring the direct current electric resistance at two relative humidity (RH) values, 11 and 97 %, respectively. The POT/TiO2 nanocomposite films exhibited quick response and recovery times, which were about 38 and 6 s, respectively. Both the response and recovery time are faster than those of pure POT films. The results indicate that the POT/TiO2 nanocomposite films have better sensing property than pure POT films. The increasing humidity sensitivity of the POT/TiO2 nanocomposite films attributes to the synergic adsorption of the water molecules from both POT and TiO2, and the high surface areas of nanocomposite films.