Preparation And Optical Properties Of TiO₂ Based Composite Semiconductor Materials

With the rapid increase of population and the improvement of industrialization and urbanization level,as well as the transformation of agricultural production methods,environmental pollution has become a major problem of human society at this stage.Among them,organic pollutants are a common kind of environmental pollutants,while most of them are hardly degraded by the earth.Photocatalysis and piezoelectric catalysis can effectively degrade organic pollutants,which is a new type of pollution treatment method that has attracted much attention.The performance of photocatalysts and piezoelectric catalysts plays a key role during the process and has become a hot research topic.Layered nanomaterials with many interesting properties have wide application prospects.For exsample,the specific layered TiO₂ has large surface area.Besides,the recombination rate of the photogenerated electron-hole pairs is low,so the photogenerated electron-holes have higher redox ability than that of the anatase TiO₂.However,the band gap of the layered TiO₂ is too large,which is disadvantageous for the absorption of visible light.Combining TiO₂ with MoS₂ is a decent solution to address above problems as it can facilitate the absorption of visible light,prolong the lifetime of electron-hole pairs,resulting in the reduction of recombination rate of photogenerated electron-hole pairs.improving the photocatalytic activity of visible light and adsorption capacity of organic pollutants.In addition,the thin layer MoS₂ has good piezoelectric catalytic properties.The magnetic properties of low-dimensional materials have important research value.Layered materials provide a good platform for studying two-dimensional magnetic properties.The existing theoretical calculations indicate that ferromagnetism with Curie temperature higher than room temperature can be obtained in layered TiO₂materials.So far,no relevant experiments have been reported.The main results obtained in this paper are listed as follows:?1?Layered TiO₂ and TiO₂-MoS₂ samples were successfully prepared by hydrothermal method.The microstructure,light absorption,photoluminescence,photocatalysis and piezoelectric catalytic properties of layered TiO₂ and TiO₂-MoS₂were studied,and the growth mechanism of the sample was illustrated.The results show that the layered TiO₂-MoS₂ samples have higher visible light absorption capacity,better organic pollutant adsorption capacity,stronger photocatalysis and piezoelectric catalytic activity than that of P25-TiO₂ and layered TiO₂.?2?The thermal stability of the layered TiO₂-MoS₂ was studied.It was found that the heat treatment can destroy the layered structure and reduce the adsorption capacity and photocatalytic ability of the sample to organic matter.?3?The relationship between magnetic properties and temperature?M?T??of layered TiO₂?LT?,anatase TiO₂?AT?and amorphous TiO₂?AMT?were compared.At room temperature,LT and AT samples have ferromagnetism,and AMT samples have diamagnetic resistance.The saturation magnetic moment of LT is about 3 times longer than that of AT.The M?T?of LT,AT and AMT have the characteristics of convex,linear and concave,respectively,which indicates that the free carrier density and mean free path of LT are larger than that of AT and AMT.Structural defects such as oxygen vacancies in LT cause magnetic moment and ferromagnetic interaction.