J. Phys. Chem. C 2009, 113, 18643–18651
18643
Excited-State Electron Transfer from CdS Quantum Dots to TiO2 Nanoparticles via Molecular Linkers with Phenylene Bridges Rachel S. Dibbell, Diane G. Youker, and David F. Watson* Department of Chemistry, UniVersity at Buffalo, The State UniVersity of New York, Buffalo, New York 14260-3000 ReceiVed: August 17, 2009; ReVised Manuscript ReceiVed: September 10, 2009
We have characterized electron transfer from photoexcited CdS quantum dots (QDs) to TiO2 nanoparticles (NPs) through bifunctional phenylene-containing linkers (L). Three L were examined: 4-mercaptobenzoic acid (4MBA), 2-mercaptobenzoic acid (2MBA), and 4-mercaptophenylacetic acid (4MPAA). Only 4MBA and 4MPAA promoted the attachment of CdS QDs to TiO2 NPs. Electron injection and interfacial charge recombination were characterized by steady-state emission quenching, nanosecond time-resolved emission, and nanosecond transient absorption measurements. The electron injection efficiency was influenced by the electronic coupling through L and/or the interparticle distance. Electron injection through 4MBA occurred on multiple time scales. The fast component (
