Location of Hole and Electron Traps on Nanocrystalline Anatase TiO2

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• 作者：Candy C. Mercado ; Fritz J. Knorr ; Jeanne L. McHale ; Shirin M. Usmani ; Andrew S. Ichimura ; Laxmikant V. Saraf
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：May 17, 2012
• 年：2012
• 卷：116
• 期：19
• 页码：10796-10804
• 全文大小：423K
• 年卷期：v.116,no.19(May 17, 2012)
• ISSN：1932-7455

文摘

The defect photoluminescence from TiO₂ nanoparticles in the anatase phase is reported for nanosheets which expose predominantly (001) surfaces and compared to that from conventional anatase nanoparticles which expose mostly (101) surfaces. Also reported is the weak defect photoluminescence of TiO₂ nanotubes, which we find using electron backscattered diffraction to consist of walls which expose (110) and (100) facets. The nanotubes exhibit photoluminescence that is blue-shifted and much weaker than that from conventional TiO₂ nanoparticles. Despite the preponderance of (001) surfaces in the nanosheet samples, they exhibit photoluminescence similar to that of conventional nanoparticles. We assign the broad visible photoluminescence of anatase nanoparticles to two overlapping distributions: hole trap emission associated with oxygen vacancies on (101) exposed surfaces, which peaks in the green, and a broader emission extending into the red which results from electron traps on undercoordinated titanium atoms, which are prevalent on (001) facets. The results of this study suggest how morphology of TiO₂ nanoparticles could be optimized to control the distribution and activity of surface traps. Our results also shed light on the mechanism by which the TiCl₄ surface treatment heals traps on anatase and mixed-phase TiO₂ films and reveals distinct differences in the trap-state distributions of TiO₂ nanoparticles and nanotubes. The molecular basis for electron and hole traps and their spatial separation on different facets is discussed.