Crystal structures of Ru complex sensitizers of TiO2 anatase nanopowders

The crystal structure of a new Ru complex sensitizer is determined (C29H30N5O4S2Ru, monoclinic, space group P2(1)/b, a = 11.400(4), b = 15.236(6), c = 18.748(7) Angstrom, gamma = 85.17(3)degrees, Z = 4). The crystal structure of three efficient Ru sensitizers of TiO2 anatase nanocrystalline powders are discussed in terms of formation of two-dimensional molecular packing which could also exist on the dye-coated anatase surfaces. The surface areas of sensitizers on the hat semiconductor surface are determined. The atomic structure of the (001) and (101) surface of naturally grown TiO2 anatase have been investigated using low-energy electron diffraction (LEED) and the technique of secondary-electron imaging (SEI). The structure of both surfaces is found to be very sensitive to external physical influences; even a mild sputtering with He+ ions results in a destruction of the surface structure in several atomic layers. The anatase surface was found to be covered with less than one atomic layer thicker contamination. The results of LEED and SEI studies could be well reproduced by model calculation based on the atomic structure of nonreconstructed surface. Thus, it is concluded that the bulk crystalline structure of naturally grown anatase continues up to the surface without modification. The first results on the orientation of sensitizer molecules on the mostly exposed surface (101) of anatase single crystal are obtained from HRTEM data. The amount of sensitizer molecules on the mostly exposed faces of anatase nanocrystals in thin colloidal TiO2 anatase films could be estimated using crystal structural data of both the sensitizer and the anatase surface. (C) 1997 Academic Press.