Interfacial Electron Transfer in FeII(CN)6 4- Sensitized TiO2 Nanoparticles: A Study of Direct Charge Injection by Electroabsorption Spectroscopy

M. KHOUDIAKOV; A. R. PARISE; B. S. BRUSCHWIG

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY

AMER CHEMICAL SOC

Año: 2003 vol. 125 p. 4637 - 4642

0002-7863

Electroabsorption (Stark) spectroscopy has been used to study the dye sensitized interfacial electron transfer in an FeII(CN)64- donor complex bound to a TiO2 nanoparticle. The average charge-transfer distance determined from the Stark spectra is 5.3 Å. This value is similar to the estimated distance between the FeII center of the complex and the TiIV surface site coordinated to the nitrogen end of a bridging CN ligand in (CN)5FeII−CN−TiIV(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(Δα), between the ground and the excited states of the FeII(CN)64-−TiO2(particle) system is 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.