Optical properties of anatase and rutile TiO_2 studied by GGA + U

The optical properties of thermally annealed TiO_2 samples depend on their preparation process, and the TiO_2 thin films usually exist in the form of anatase or rutile or a mixture of the two phases. The electronic structures and optical properties of anatase and rutile TiO_2 are calculated by means of a first-principles generalized gradient approximation(GGA) +U approach. By introducing the Coulomb interactions on 3d orbitals of Ti atom(U~d) and 2p orbitals of O atom(U~p), we can reproduce the experimental values of the band gap. The optical properties of anatase and rutile TiO_2 are obtained by means of the GGA+U method, and the results are in good agreement with experiments and other theoretical data. Further, we present the comparison of the electronic structure, birefringence, and anisotropy between the two phases of TiO_2. Finally,the adaptability of the GGA+U approach has been discussed.     

席夫碱荧光探针用于水体系中Cu2+的高选择性测定

以8-羟基久洛尼定-9-甲醛和4-苯基氨基硫脲为原料合成了一种新的Schiff碱荧光探针(L)。在乙腈-水(1∶1,v/v,HEPES,pH=7. 4)缓冲溶液中,L与Cu~(2+)以1∶1和1∶2两种比例结合,溶液颜色由黄色变为棕黄色,荧光发生猝灭,体系的荧光强度和Cu~(2+)浓度在0～13μM的范围内呈线性关系,由此可以实现水体系中对Cu~(2+)的高选择性定量检测,检测限为6. 7×10~(-8)M。