化学
电子顺磁共振
可见光谱
光催化
二氧化钛
杂质
光化学
抗磁性
兴奋剂
带隙
顺磁性
离子
辐照
无机化学
核磁共振
催化作用
化学工程
材料科学
光电子学
凝聚态物理
核物理学
生物化学
物理
有机化学
量子力学
磁场
工程类
作者
Stefano Livraghi,Maria Cristina Paganini,Elio Giamello,Annabella Selloni,Cristiana Di Valentin,Gianfranco Pacchioni
摘要
Nitrogen-doped titanium dioxide (N-TiO2), a photocatalytic material active in visible light, has been investigated by a combined experimental and theoretical approach. The material contains single-atom nitrogen impurities that form either diamagnetic (Nb-) or paramagnetic (Nb•) bulk centers. Both types of Nb centers give rise to localized states in the band gap of the oxide. The relative abundance of these species depends on the oxidation state of the solid, as, upon reduction, electron transfer from Ti3+ ions to Nb• results in the formation of Ti4+ and Nb-. EPR spectra measured under irradiation show that Nb centers are responsible for visible light absorption with promotion of electrons from the band gap localized states to the conduction band or to surface-adsorbed electron scavengers. These results provide a characterization of the electronic states associated with N impurities in TiO2 and, for the first time, a picture of the processes occurring in the solid under irradiation with visible light.
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