Electronic Properties of Adjoined TiO2 Nanocrystals

  • Michael Elser, Institute of Materials Chemistry, Vienna University of Technology, Veterinaerplatz 1/GA, A-1210 Vienna, Austria, Austria
  • Nicolas Siedl, Institute of Materials Chemistry, Vienna University of Technology, Veterinaerplatz 1/GA, A-1210 Vienna, Austria, Austria
  • Johannes Bernardi, University Service Centre for Transmission Electron Microscopy, Vienna University of Technology, Wiedner Hauptstrasse 8-10/137,, Austria
  • Oliver Diwald, Institute of Materials Chemistry, Vienna University of Technology, Veterinaerplatz 1/GA, A-1210 Vienna, Austria, Austria

    • To include particle attachment and porosity in the discussion of the electronic properties of nanostructured oxide materials is indispensable for deeper insights into electronic conduction across grain boundaries and thus essential to electronics, sensor technology and photovoltaics. We investigated the condensation of isolated TiO2-nanocrystals which results from the application of a simple hydration-dehydration cycle. After contact with water and subsequent dehydration and adsorbate removal under high vacuum conditions the powder of originally isolated nanocrystals [1] is transformed into a monolithic solid which consists of a particle network with a mesoporous structure. These monoliths show significant changes in the optical absorption properties as investigated by UV-diffuse reflectance spectroscopy. In addition, polarizable conduction band electrons [2] are only observed in the network which consists of adjoined TiO2-nanocrystals [3]. Since photo-assisted tunneling between localized states in the oxide particle network represents an important conduction mechanism in dye-sensitized solar cells, UV induced charge separation processes were studied on nanocrystal aggregates using EPR and IR spectroscopy. Corresponding results will be discussed in the light of associated structural data.

    [1]T. Berger, M. Sterrer, O. Diwald, E. Knözinger, Chem. Phys. Chem. 2005 6 2104.
    [2]E. Serwicka, M. W. Schlierkamp, R. N. Schindler, Z. Naturforschung 1981, 36a, 226.
    [3]M. J. Elser, T. Berger, D. Brandhuber, J. Bernardi, O. Diwald, E. Knözinger, J. Phys. Chem. B 2006, 110, 7605.