First-principle Calculations And Preparation Of Titanate And TiO₂Monolayer

In recent years, the two-dimensional material has attracted more and more attention.Titanates have a layered structure similar to graphene, but there is little study about how toisolate them to two-dimensional materials. This paper focuses on the possibility of obtainingtwo-dimensional monolayer structure titanate and TiO2, their structural characteristics alsostudied.The geometry, the electronic properties, the binding force between the layers ofNa2Ti3O7and NaKTi3O7has been investigated by the first principles method. In the electronicstructure calculations, the band structure, density of states, charge density were investigated.From the results we conclude that:(1) The strong bonding force of Ti atom and O atoms inthe layer mainly stabilized titanate;(2) In NaKTi3O7structure, the binding force between Na,K atoms and ipsilateral (Ti3O7)2-layer enhanced, helping form a independent monolayerstructure;(3)The interlayer adhesion of the calculation showed that the binding force betweenlayers NaKTi3O7smaller than Na2Ti3O7,which helps the formation of a monolayer structure.The stable structure of anatase TiO2(101) and the optical and electronic properties of theTiO2ultra-thin film have been investigated by plane-wave ultrasoft pseudopotential method.The total energy and the surface energy were calculated, the most stable surface atomstermination structure of TiO2(101) surface was found according to the principle of theminimum energy. Based on the stable structure, changing the film thickness(0.23~1.56nm),the influence of thickness to energy band structure, density and optical properties werestudied. The calculated results show that，with the increase of the thickness of the surfacestructure, the conduction band down，the occupy width and the band gap decreases; Opticalabsorption peak intensity decreases, and the absorption edge appears a redshift.TiO2as precursor, NaOH and KOH as mineralizing agent, the filling degree of68%,hydrothermal reaction at140℃for24h, titanate were prepared. Preliminary analysis wereperformed by XRD and TEM, and they show that titanate can exist in the form of monolayer.Titanic acid was obtained by treatment in the solution of HCL acidification at room temperature, then heated at different temperatures to obtain nano TiO2thin film The opticalabsorption characteristics of TiO2prepared was measured. The results showed that the strongabsorption appears in the ultraviolet region, the absorption peak about270nm, and the opticalband gap is about3.7eV. It indicates that, compared with material, the band gap width ofanatase TiO2monolayer has a significantly larger.