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Hybrid titania gel films are prepared from titanium butoxide and vinylpyrrolidone (VP). When the gel film is exposed to UV light, the CC double bond of VP in the film polymerizes and the solubility of the irradiated film decreases in HCl aqueous solution. The difference of the solubility between the irradiated and unirradiated parts makes fine patterning on the hybrid titania film whose refractive index is in the range between 1.8 and 2.1.

The influence of electrode materials on the current vs. voltage characteristics of limiting-current-type zirconia cells has been investigated systematically. The cells have one or two pairs of electrodes consisting of Pt, Pd, Au, or Ag, and a cover with a pinhole, which serves to limit gas diffusion and, therefore, the electrical current of the cells. The limiting current was found to depend definitely on the catalytic activity of the electrodes for the oxidation reaction of hydrocarbon gases in oxygen and hydrocarbon--containing gases. The results were applied to improve the sensitivity of limiting-current hydrocarbon sensors. The highest sensitivity was attained for the following combination of electrodes: Pt and Ag inner electrodes and a Au outer electrode in two-inner-electrode sensors. A preliminary examination has also been made on a three-inner-electrode sensor.