Charge Separation in Layered Titanate Nanostructures: Effect of Ion Exchange Induced Morphology Transformation

  • Alexander Riss, Institute of Materials Chemistry, Vienna University of Technology, Veterinaerplatz 1, A-1210 Vienna Austria, Austria
  • Thomas Berger, Institute of Materials Chemistry, Vienna University of Technology, Veterinaerplatz 1, A-1210 Vienna Austria, Austria
  • Hinrich Grothe, Institute of Materials Chemistry, Vienna University of Technology, Veterinaerplatz 1, A-1210 Vienna Austria, Austria
  • Johannes Bernardi, USTEM, Vienna University of Technology, Wiedner Hauptstrasse 8-10/137, A-1040, Vienna Austria, Austria
  • Erich Knözinger, Institute of Materials Chemistry, Vienna University of Technology, Veterinaerplatz 1, A-1210 Vienna Austria, Austria
  • Oliver Diwald, Institute of Materials Chemistry, Vienna University of Technology, Veterinaerplatz 1, A-1210 Vienna Austria, Austria

    • Morphology changes induced by surface chemistry can provide important insights into photoexcitation processes on solids which are critical to photovoltaic and photocatalytic applications. This opportunity region is of particular relevance for TiO2 based nano-materials which have become available as sheets, wires, and tubes since only recent.[1]We investigated charge separation processes on Na2Ti3O7 nanowires and scrolled up H2Ti3O7 nanotubes, two types of morphologies which by means of acid/base treatment can reversibly be transformed into each other [2]. Their photochemical activity depends on the branching ratio between the three pathways photoexcited states can undergo: they can deactivate under photoluminescence emission or generation of heat, become persistently trapped or undergo interfacial charge transfer at the particle surface. Some of these competitive processes can be tracked by means of EPR and photoluminescence spectroscopy. A complementarity between efficient charge separation [2], on one and, and radiative recombination of photoexcited states [3], on the other, was observed and clearly demonstrates the critical influence morphology and interlayer composition on the photoelectronic properties of layered oxide nanostructures.

    Financial support from the Austrian Fonds zur Förderung der wissenschaftlichen Forschung (FWF P17514N11) is gratefully acknowledged.

    [1](a) D.V. Bavykin, J.M. Friedrich, F. C. Walsh, Adv. Mater. 2006, 18, 2807; (b) Y. Mao Y, T.J. Park, F. Zhang, H. Zhou, S.S. Wong, Small 2007,2,1122;
    [2]A. Riss, T. Berger, S. Stankic, J. Bernardi, E. Knözinger, O. Diwald, Angew. Chem. Int Ed. 2007, anie.200703817, in press
    [3]A. Riss, T. Berger, H. Grothe, J. Bernardi, E. Knözinger, O. Diwald, Nano Lett. 2007,7, 433;