PHOTOSENSITIZATION OF NANOPOROUS TIO2 ELECTRODES WITH INP QUANTUM DOTS

Quantum dots (QDs) of InP strongly adsorb onto transparent, porous, na nocrystalline TiO2 electrodes prepared by sintering 200-250 Angstrom d iameter TiO2 colloidal particles. The interparticle space of the TiO2 electrodes is large enough to permit deep penetration of 65-Angstrom I nP QDs into the porous TiO2 film. The absorption of light increases li nearly with the thickness of the TiO2 film indicating that the InP QDs are adsorbed homogeneously on the TiO2 surface. We found that large p articles adsorb better than smaller ones probably due to less hindranc e by the stabilizer. The solid films exhibit strong photoconductivity in the visible region indicating photosensitization of TiO2 by InP QDs . The photocurrent action spectrum of the TiO2/InP QD film at a potent ial of +1 V is consistent with the absorption spectrum of the InP QDs. A photoelectrochemical cell was formed that consisted of p-type InP Q Ds loaded on TiO2, which was immersed in a I-/I-3(-) or hydroquinone/q uinone acetonitrile solution, and a Pt counter electrode. These photoe lectrochemical experiments show that electron transfer from InP QD int o TiO2 nanoparticles occurs. p-Type InP/TiO2 electrodes are stable dur ing illumination while n-type photocorrodes in an electrochemical cell .