Abstract: Pure and Ag-doped TiO2 powders were prepared by sol-gel method. The crystal structure, particle size and surface properties of the samples were characterized by means of X-ray diffraction(XRD), transmissionelectron microscopy(TEM) and Brunaner-Emmett-Teller(BET) surface areas. The results revealed that the Ag dopant increased the specific surface area of TiO2 powders. The sensitive properties of the samples were also investigated. It was found that the doped sensor had a better sensitivity and higher selectivity to HCHO than the pure one. The sensitivity of the sensor , which was prepared with 5% Ag-doped TiO2 calcined at 500 ℃, was the highest. With the optimum working current of 124 mA, the sensitivity of the sensor was approximate to 4 at its detection limit of 10 μL·L-1, its recovery time was 9 s whereas response time was no more than 1 s.

Key words: Sol-gel method, TiO2/Ag2O, Nanocrystal, Formaldehyde, Sensitivity