Synthesis And Humidity Sensing Properties Of Titanium Oxide And Titanium Oxide Based Composite Materials

TiO₂ is a typical n-type semiconductor material. Because of its advantages such as non-toxic, well biological compatibility, light corrosion resistance, nano-TiO₂ has been widely applied to sensors, solar cells, and other fields. Besides, TiO₂ is a humidity sensing material with good sensing properties. Its research in the field of humidity sensors have also been widely concerned. However, the high resistance of pure TiO₂, low sensitivity and long response-recovery time are still vital problems to restrict its application on humidity senors. In order to obtain excellent sensing performance, the general route is forming composites or control the morphologies of TiO₂. Forming composites with other material with excellent conductivity can decrease the resistance of TiO₂. Otherwise, control the morphologies of TiO₂ can guarantee the humidity sensing materials with large surface areas providing more adsorption sites of H₂O which can improve sensing sensitivity efficiently. For all of this, this paper designed and synthesized particle TiO₂/G ?P-TiO₂/G?, urchin-like TiO₂ ?U-TiO₂? and urchin-like TiO₂/G ?U-TiO₂/G?. The detail reseach content is as follows:?1? To decrease the resistance of TiO₂ we synthesized anatase partical TiO₂/G combining sol-gel method with hydrothermal process under the inducing of ammonia solution. Graphene can improve electrical conductivity of TiO₂. Meanwhile the large surface areas of graphene can also provide more adsorption sites of H₂O. By controling the ammonia solution we synthesized three groups products with different radio of TiO₂. The particle TiO₂ of the obtained composite is about 7?10 nm and uniformly distributed on the surface of G. Besides the obtained composite has abundant mesoporous. The experiment results show that the addition of graphene can greatly lower the resistance of the sensing material. By comparison, the P-TiO₂/G with 90 wt.% TiO₂ has the best humidity sensing characteristics, including the best linear and the highest sensitivity ?S=2223?. Besides the wet hysteresis coefficient is very small H=5%, and the stability test within 60 days show that P-TiO₂/G has good sensing stability.?2? To obtain more adsorption sites of H₂O and improve the sensitivity, we synthesized urchin-like TiO₂. To decrease the resistance of TiO₂ we further synthesized urchin-like TiO₂/G sensing materials respectively. Pure U-TiO₂ has perfect urchin structure the size of which is about 2.5?m. However, the urchin-like TiO₂ in U-TiO₂/G is uniformly distributed on the surface of G with the size is about 1.5?m smaller than pure TiO₂. By analyzing the sensing properties, the addition of graphene can lower the resistance of TiO₂ effectively. Thanks to the large surface and abundant porous structure, both TiO₂ and TiO₂/G show excellent humidity sensing properties. By comparison, urchin-like TiO₂ shows faster response time about 1 s. Thanks to the Schottky junction, urchin-like TiO₂/G shows better linear and faster recovery about 18 s. Besides, both of the humidity sensing materials show small wet hysteresis coefficient and acceptable long-time stability.