CRYSTAL-STRUCTURES OF RU COMPLEX SENSITIZERS OF TIO2 ANATASE NANOPOWDERS

The crystal structure of a new Ru complex sensitizer is determined (C2 9H30N5O4S2Ru, monoclinic, space group P2(1)/b, a = 11.400(4), b = 15.2 36(6), c = 18.748(7) Angstrom, gamma = 85.17(3)degrees, Z = 4). The cr ystal structure of three efficient Ru sensitizers of TiO2 anatase nano crystalline powders are discussed in terms of formation of two-dimensi onal molecular packing which could also exist on the dye-coated anatas e surfaces. The surface areas of sensitizers on the hat semiconductor surface are determined. The atomic structure of the (001) and (101) su rface of naturally grown TiO2 anatase have been investigated using low -energy electron diffraction (LEED) and the technique of secondary-ele ctron imaging (SEI). The structure of both surfaces is found to be ver y sensitive to external physical influences; even a mild sputtering wi th He+ ions results in a destruction of the surface structure in sever al atomic layers. The anatase surface was found to be covered with les s than one atomic layer thicker contamination. The results of LEED and SEI studies could be well reproduced by model calculation based on th e atomic structure of nonreconstructed surface. Thus, it is concluded that the bulk crystalline structure of naturally grown anatase continu es up to the surface without modification. The first results on the or ientation 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 nanocrysta ls in thin colloidal TiO2 anatase films could be estimated using cryst al structural data of both the sensitizer and the anatase surface. (C) 1997 Academic Press.