Electroabsorption (Stark) spectroscopy has been used to study the dye sensitized interfacial electron transfer in an Fe(II)(CN)(6)(4)(-) donor complex bound to a TiO(2) nanoparticle. The average charge-transfer distance determined from the Stark spectra is 5.3 A. This value is similar to the estimated distance between the Fe(II) center of the complex and the Ti(IV) surface site coordinated to the nitrogen end of a bridging CN ligand in (CN)(5)Fe(II)-CN-Ti(IV)(particle). This finding suggests that the electron injection is to either an individual titanium surface site or a small number of Ti centers localized around the point of ferrocyanide coordination to the particle and not into a conduction band orbital delocalized over the nanoparticle. The polarizability change, Tr(Deltaalpha), between the ground and the excited states of the Fe(II)(CN)(6)(4)(-)-TiO(2)(particle) system is approximately 3 time larger than normally observed in mixed-valence dinuclear metal complexes. It is proposed that the large polarizability of the excited state increases the dipole-moment changes measured by Stark spectroscopy.
Nanoscale Au/Fe2O3
catalysts for CO oxidation were prepared by a deposition–precipitation technique
using the thermal decomposition of urea. Freshly precipitated amorphous
Fe(OH)3
was used as a support. The resulting products were characterized by transmission electron
microscopy and x-ray powder diffraction. The catalysts in the ‘as prepared’ state
demonstrated exceptionally high activity toward CO oxidation. Compared to conventional
coprecipitation with the same amount of gold precursor, the deposition–precipitation
method was shown to produce more active catalysts because it allows complete
precipitation of gold from solution.
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