The development of gas sensor for carbon monoxide monitoring using nanostructure of Nb–TiO₂

The development of titanium dioxide (TiO2) as a gas sensor for combustion and exhaust air pollutants monitoring is strongly dependent on its properties such as thermal stability, grain size and surface area. In this study, nanostructure TiO2 with its thermal stability enhanced by niobium dopant (Nb–TiO2) was synthesized using the water-in-oil (w/o) microemulsion system of n-heptane/water/sodium bis (2-ethylhexyl) sulfosuccinate (AOT) surfactant and was compared with undoped TiO2. It was found that the synthesized powder was of uniform size (14 nm) and high surface area (80 m2/g). Nb-doped TiO2 at a level of 3–5 mole% clearlyhinders the anatase to rutile phase transformation and inhibits the grain growth in comparison with pure TiO2. The nanostructure of anatase was maintained even after the powder was fired at 850 °C. The result indicates that sensitivity of CO is significantly increased with an increase of thermal stability of Nb-doped TiO2 in comparison with those of undoped TiO2 and thus is useful for CO sensing studies at high temperatures.