Optical CO sensitivity of Au–CuO composite film by use of the plasmon absorption change

Gold–copper oxide (Au–CuO) composite films were prepared by the sputter-deposition of gold onto a glass plate substrate followed by pyrolysis of spin-coated copper naphthenate. The films comprise small Au particles and small CuO crystals both with diameters around 20 nm, and exhibit optical response to CO in air. Carbon monoxide caused large increase in absorbance in the visible-near IR wavelength range. The absorbance change due to CO occurred near the plasmon absorption band of small Au particles with a maximum in the range of 700–800 nm, suggesting that the absorbance by small Au particles in the plasmon band was influenced by the changes in the dielectric constant and refractive index of copper oxide which surrounded small Au particles. The reversible absorbance change and the relatively fast response to CO over a concentration range from 50 to 10,000 ppm (1 vol.%) make the Au–CuO composite films to be useful for optical CO detection.