Selective optical detection of H2 and CO with SiO2 sol-gel films containing NiO and Au nanoparticles

NiO is a p-type semiconductor widely studied for its promising implementation in chemo-optical gas sensors. Reducing/oxidizing gases induce a change in optical absorption of NiO. It has been found that Au doping induces a remarkable increase in the NiO sensitivity, and at the same time silica films obtained by the sol-gel technique have been demonstrated to be a suitable support matrix for gas-sensitive materials due to their extremely high specific surface area (up to 600 m(2) g-(1)). The aim of this work is the synthesis of SiO2 films containing both NiO and Au nanoparticles and their morphological and functional characterization as active gas-sensing materials suitable for optical detectors. The possibility to selectively recognize H-2 and CO is studied exploiting the wavelength dependence of the gas-induced transmittance variation.