Narrowing of band gap in thin films and linear arrays of ordered TiO$_{2}$ nanoparticles

ORAL

Abstract

Utilizing ambient pressure synchrotron x-ray spectroscopies, we report the properties of thin films and linear arrays of ordered TiO$_{2}$ nanoparticles under in situ water vapor exposure and heating. Our nondestructive depth profiles indicates an enhancement of the density of states (DOS) near the Fermi level due to surface Ti$^{3+}$ states and oxygen vacancies caused by heating isolated TiO$_{2}$ nanoparticles. In contrast, introducing water on the TiO$_{2}$ interface eliminates oxygen vacancies and increase Ti$^{4+}$ configurations, thereby suppressing the DOS enhancement. Our results suggest that the TiO$_{2}$ band gap can be tuned reversibly under water exposure and heating, and isolated TiO$_{2}$ nanoparticles can potentially enhance solar absorption efficiency and the life time of electron-hole pairs for photocatalysis.

*This work is supported by the Center for Solar Energy at UC Irvine and the U.S. Department of Energy under Grant No. DE-FG02-96ER45576

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Authors

  • Yu Liu

    • Department of Physics and Astronomy, University of California, Irvine

  • James Taing

    • Department of Chemistry, University of California, Irvine

  • Cheng-Chien Chen Chen

    • Advanced Photon Source, Argonne National Laboratory
    • Argonne National Lab

  • Adam Sorini

    • Lawrence Livermore National Laboratory

  • Ming H. Cheng

    • Department of Chemistry, University of California, Irvine

  • Alexandria Margarella

    • Department of Chemistry, University of California, Irvine

  • Hendrik Bluhm

    • Lawrence Berkeley National Laboratory

  • Zhi Liu

    • Lawrence Berkeley National Laboratory

  • Thomas Devereaux

    • SLAC National Acceleratory Laboratory
    • Stanford University, Stanford CA 94305, USA
    • Stanford Institute of Materials and Energy Sciences, SLAC NATIONAL ACCELERATOR LABORATORY 2575 Sand Hill Road, Menlo Park, CA 94025
    • Stanford Institute for Materials and Energy Science, SLAC National Accelerator Laboratory
    • SLAC National Accelerator Lab and Stanford University
    • Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory

  • John Hemminger

    • Department of Chemistry, University of California, Irvine