ABSTRACT

Sol gel spin coating method has been successfully employed for the deposition of nanocrystalline nickel oxide (NiO) thin films. The films were annealed at 400°C - 700°C for 1 h in an air and changes in the structural, morphological, electrical and optical properties were studied. The structural properties of nickel oxide films were studied by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis shows that all the films are crystallized in the cubic phase and present a random orientation. Surface morphology of the nickel oxide film consists of nanocrystalline grains with uniform coverage of the substrate surface with randomly oriented morphology. The electrical conductivity showed the semiconducting nature with room temperature electrical conductivity increased from 10^-4 to 10^-2(Ωcm)^-1 after annealing. The decrease in the band gap energy from 3.86 to 3.47 eV was observed after annealing NiO films from 400^oC - 700^oC. These mean that the optical quality of NiO films is improved by annealing

The performance at room temperature of nanostructured polyaniline (PANi)-titanium dioxide (TiO 2 ) ammonia gas sensors was investigated. The PANi-TiO 2 thin-film sensors were fabricated with a spin-coating method on glass substrates. PANi-TiO 2 (0-50%) sensor films were characterized for their structural, morphological, optical, and various gas-sensing properties. The structural analysis showed the formation of nanocrystalline TiO 2 , whereas PANi exhibited an amorphous nature. Morphological analysis of the PANi-TiO 2 nanocomposites film revealed a uniform distribution of TiO 2 nanoparticles in the PANi matrix. The absorption peaks in the Fourier transform infrared spectra and ultraviolet-visible spectra of the PANi-TiO 2 composite film were found to shift to higher wave numbers compared to those observed in pure PANi. The observed shifts were attributed to the interaction between the TiO 2 particles and the PANi molecular chains. The gas-sensing properties showed that the sensors exhibited selectivity to ammonia (NH 3 ) at room temperature.

No abstract

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.