Meso- to macro-porous oxides as semiconductor gas sensors

The present article reviews our latest studies directed to improving gas sensing properties of semiconductor metal oxides, SnO2 and TiO2, by controlling their porous structure in the range of nano- to micro-meter size. Thermally stable mesoporous oxide powders and submicron-size porous thick films were fabricated by a templating method employing supramolecular surfactants or polymethylmethacrylate microspheres and also by a sol - gel process in a polyethylene glycol matrix. Advantages of these methods in improving the sensing properties are overviewed and then remaining problems are discussed.