A gas-sensing Coo/SiO2 nanocomposite

We developed a gas sensing CoO/SiO2 nanocomposite which changes its optical transmittance by nitrogen oxide. Films prepared by co-sputtering and sol-g el method showed reversible transmittance change by NO at 350 degrees C in the wavelength range from 400 to 800 nm. Nano-scale cobalt oxide dots were observed in the CoO/SiO2 nanocomposite. The sensing properties can be consi dered to be originated from nanostructures composed of (a) functional CoO n anoparticles whose optical transmittance is changed by nitrogen oxide, (b) nanopores which provide paths for gas molecules, and (c) a transparent SiO2 matrix which enables us to measure optical transmittance. The octahedral d ivalent cobalt ions confined at the interface of the composite are inferred to contribute to such transmittance change. (C) 1999 Acta Metallurgica Inc .