Au and NiO nanocrystals doped into porous sol–gelSiO2 films and the effect on optical CO detection

Abstract

Thin-film composites comprised of NiO and NiO/Au nanoparticles in a porousSiO2 matrix have been prepared using the sol–gel technique. When at elevated temperatures(200 °C<T<350 °C) and exposed to carbon monoxide, the films undergo reversible changes in opticaltransmittance at wavelengths in the visible–near IR region. For NiO composite films heated at330 °C and exposed to 1% CO in air, there is an increase in transmittance which approaches 2–4%over most of the visible range. For NiO/Au composite films the transmittance increaseexhibits a wavelength dependence, with a maximum change which is close to 6% atλ≈630 nm and which is close to zero in the Au plasmon resonance range(λ≈550 nm).