Polyvinyl alcohol-In2O3 nanocomposite films: synthesis, characterization and gas sensing properties

Poly(vinyl alcohol) (PVA)-In2O3 (with 1 and 5 wt% In2O3 loading) nanocomposite films have been prepared by a solvent-casting technique. The In2O3 nanoparticles used in this work were prepared by nonhydrolytic alcoholysis ester elimination reaction of indium acetate in the presence of oleic acid and oleyl alcohol at 220 degrees C. X-Ray diffraction (XRD) patterns and transmission electron microscopy (TEM) studies indicate that the In2O3 nanocrystals obtained in this work are nearly monodisperse, highly crystalline with cubic bixbyite structure without the presence of any other impurity phase. The PVA-In2O3 nanocomposite films have been structurally characterized by XRD, Fourier transform infrared (FTIR) and Raman spectroscopy. The results confirm the incorporation of In2O3 nanocrystals in the PVA matrix and interactions between In2O3 nanocrystals and PVA molecules. The thermal properties of nanocomposite films have been investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The thermo-oxidative degradation temperature of PVA increases with the addition of In2O3 nanocrystals and the degree of crystallinity of the PVA matrix decreases in the presence of In2O3 nanocrystals in the nanocomposite films. The room temperature sensing characteristics of the naocomposite films have been studied for various gases, namely, H2S, NH3, CH3, CO, and NO. The PVA-In2O3 nanocomposite films show maximum sensitivity for H2S gas with fast response and reversibility. The response mechanism of the nanocomposite films to various gases is also proposed.