Optical recognition of CO and H-2 by use of gas-sensitive Au-Co3O4 composite films

Gold-cobalt oxide (Au-Co3O4) composite films have been prepared by the sputter-deposition of gold onto a glass plate substrate followed by pyrolysis of spin-coated cobalt 2-ethylhexanoate. The films comprise small Au particles and Co3O4 nanocrystals, and exhibit different and independent optical responses to CO and H-2 in air. Carbon monoxide caused only a decrease in absorbance, while H-2 caused both a decrease and an increase in absorbance at different wavelengths. Among solid-state gas sensor materials, this Au-Co3O4 composite film is probably the first example of an inorganic material which can be used for the recognition of CO and H-2 molecules through optical absorbance changes.