INTERACTION INDUCED TRANSITION IN THE NANOPOROUS TiO2/Pd- PORPHYRIN SYSTEM

M. FUNES, P. ZABEL, T. DITTRICH, E. DURANTINI, L. OTERO

La Plata

Jornada; Cuarto Encuentro de Física y Química de Superficies; 2009

as light receptors and for spectral sensitization of wide band gap semiconductors. For all ofthese applications, the interaction of porphyrin molecules with a metal oxide surface plays animportant role. The central metal atom of metal centred porphyrins has a strong influence onthe electronic transitions in porphyrins, especially on the Q-band and should also play anessential role for the molecule – metal oxide surface interaction. Specific interactions willlead to the formation of new electronic states at or near the surface of the metal oxide.Molecules of Pd(II) 5-(4-carboxyphenyl)-10,15,20-tris(4-methylphenyl) porphyrin wereadsorbed from highly diluted dichloromethane solution on ultra-thin layers of nanoporousTiO2 and investigated by modulated surface photovoltage (SPV) spectroscopy. The moststriking feature of the PV spectra of Pd-porphyrin deposited at surfaces of sintered TiO2nanoparticles is the appearance of an additional transition with a maximum at 2.03 eV for theQ band at lower energy after annealing. As remark, a similar new transition did not appear forporphyrins with other central atoms. Therefore we suspect that a specific interaction(formation of a new charge transfer complex) between a Pd atom in the Pd-porphyrin and a Tisurface atom is the reason for the new transition. The optical density of the new chargetransfer complex was similar to that of the Q-band of Pd-porphyrin.