Nanocrystalline copper oxide (CuO) thin films have been synthesized by a sol-gel method using cupric acetate Cu (CH 3 COO) as a precursor. The as prepared powder was sintered at various temperatures in the range of (300-700°C) and has been deposited onto a glass substrates using spin coating technique. The structural, compositional, morphological, electrical optical and gas sensing properties of CuO thin films have been studied by X-ray diffraction, Scanning Electron Microscopy (SEM), Four Probe Resistivity measurement and UV-visible spectrophotometer. The variation in annealing temperature affected the film morphology and optoelectronic properties. X-ray diffraction patterns of CuO films show that all the films are nanocrystallized in the monoclinic structure and present a random orientation. The crystallite size increases with increasing annealing temperature (40-45 nm). The room temperature dc electrical conductivity was increased from 10 -6 to 10 -5 (X cm) -1 , after annealing due to the removal of H 2 O vapor which may resist conduction between CuO grain. The thermopower measurement shows that CuO films were found of n-type, apparently suggesting the existence of oxygen vacancies in the structure. The electron carrier concentration (n) and mobility (l) of CuO films annealed at 400-700°C were estimated to be of the order of 4.6-7.2 9 10 19 cm -3 and 3.7-5.4 9 10 -5 cm 2 V -1 s -1 respectively. It is observed that CuO thin film annealing at 700°C after deposition provide a smooth and flat texture suited for optoelectronic applications. The optical band gap energy decreases (1.64-1.46 eV) with increasing annealing temperature. It was observed that the crystallite size increases with increasing annealing temperature. These modifications influence the morphology, electrical and optical properties.

Thin films of polyaniline (PANi) and PANi:titanium oxide (TiO 2 ) composites have been synthesized by sol-gel spin coating technique. The TiO 2 powder of particle size 50-60 nm was synthesized by sol-gel technique and the polyaniline was synthesized by chemical oxidative polymerization of aniline. The composite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) Fourier transform infrared (FTIR) and UV-vis spectroscopy, and the results were compared with polyaniline films. The intensity of the diffraction peaks for PANi:TiO 2 composites is lower than that for TiO 2 . The characteristic FTIR peaks of PANi were found to shift to a higher wave number in the PANi:TiO 2 composite. These observed effects have been attributed to the interaction of TiO 2 particles with PANi molecular chains. The room temperature resistivity of polyaniline:nano-TiO 2 composite is 3.43 Â 10 3 X cm and the resistivity of pure nano-TiO 2 particles is 1.60 Â 10 6 X cm.

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Nanocrystalline copper oxide (CuO) thin films were deposited onto glass substrates by a spin coating technique using an aqueous solution of copper acetate. These films were characterized for their structural, morphological, optoelectronic properties by means of X-ray diffraction (XRD) scanning electron microscopy (SEM), UVspectroscopy and four probe method. The CuO films are oriented along (1 1 1) plane with the monoclinic crystal structure. These films were utilized in H 2 S sensors. The dependence of the H 2 S response on the operating temperature, H 2 S concentration of CuO film (annealed at 700˚C) was investigated. The CuO film showed selectivity for H 2 S. The maximum H 2 S response of 25.2% for the CuO film at gas concentration of 100 ppm at operating temperature 200˚C was achieved.