Optical gas sensing properties of silica film doped with cobalt oxide nanocrystals

SiO2 sol-gel films doped with cobalt oxide nanocrystals have been fabricated. The nanocrystals precipitate in the glass film at 500 °C, while the film is still porous. The nanocomposite films showed a reversible change in the optical transmittance when exposed to CO in the 250<λ<850 nm range. The effects of the residual porosity and testing temperature have been studied. The gas sensing properties of the cobalt oxide nanocrystals doped films are compared with those of nickel oxide nanocrystals doped silica film, previously reported.