Study On Applications Of Ti-doped Tungsten Oxide Nanocrystals Prepared By Hydrothermal

As a kind of band gap(2.5~3.5e V)n-type semiconductor material, metal oxide WO3 have cubic and hexagonal and other symmetric structures. As a member of the novel semiconductor materials, WO3 has received considerable investigated because of its unique chemical-physics properties and widespread applications in various aspects, for example: photocatalytic systems, electrochromic windows and optical adjustment devices, photochromic(gasochromic/electrochromic) devices, gas sensors,and so on. With the rapid development of semiconductor materials, its properties have been depth studied by domestic and foreign scholars in recent years, especially the use of WO3 material to develop the gas sensors.In this article, different concentrations Ti-doped WO3 nanocrystals according to formula proportion of 0at%, 2at%, 4at% and 6at% of Ti and WO3 are synthesized by hydrothermal method, and part of the samples are annealed at 350℃and 450℃for 1 h.Micro-structural properties, surface morphologies and optical properties of these materials have been characterized by the X-ray diffraction instrument, the scanning electron microscopy and spectrophotometer. The results show that the amount of Ti-doped and annealing can inhibit the growth of nanocrystals, reduce the size of nanocrystals; the dispersion of nanocrystals becomes better, the crystalline phase of these materials have changed from orthorhombic phase to orthorhombic and cubic phase together after annealed at 350℃. The optical band gap of the unannealed nanomaterials change little with the doping density of titanium increased.In this paper, the gas-sensing properties to 500 ppm nitrogen dioxide at 200℃of film sensors made of the unannealed and annealed materials are studied by using the self-instrument, and the electro gas sensitivity mechanism of nano materials are discussed. The tests of the film sensors show that the amount of Ti-doped and annealing can improve the sensitivity of sensors to NO2, the film sensor made of the annealed at 350℃of the Ti-doped for 2% has a maximum sensitivity of 15.38 and agood stability and reproducibility, the response and recovery time is 2.2min and1.5min, respectively.The optical gas sensing properties of nano film materials are tested to C2H5 OH gas of 300 ppm, H2 of 300 ppm and NO2 of 300 ppm at room temperature by designing equipment, the optical gas sensitivity mechanism of nano materials are discussed. The results show that all the samples for three gases have sensitivity at room temperature,the optical gas sensing properties of these samples in H2 gas and C2H5 OH gas of300 ppm exhibit well; the sensitivity of samples which are unannealed and Ti-doped for 2% sample and the annealed at 350℃and Ti-doped for 6% sample don’t make big differences to three gases of 300 ppm, which indicate that these two samples have no good selectivity to three gases of 300ppm; the unannealed and undoped sample has excellent selectivity to H2 gas of 300ppm; the annealed at 350℃and Ti-doped for 2%sample has good selectivity to NO2 gas of 300ppm; the annealed 350℃and undoped sample, the annealed 450℃and undoped sample, the annealed at 450℃and Ti-doped for 4% sample have excellent selectivity to C2H5 OH gas of 300 ppm.