Distance-Dependent Electron Transfer in Tethered Assemblies of

J. Phys. Chem. C 2009, 113, 3139–3149

3139

Distance-Dependent Electron Transfer in Tethered Assemblies of CdS Quantum Dots and TiO2 Nanoparticles Rachel S. Dibbell and David F. Watson* Department of Chemistry, UniVersity at Buffalo, The State UniVersity of New York, Buffalo, New York 14260-3000 ReceiVed: October 20, 2008; ReVised Manuscript ReceiVed: NoVember 26, 2008

We have characterized electron injection from photoexcited CdS quantum dots (QDs) to TiO2 nanoparticles as a function of the interparticle separation within molecularly linked assemblies. CdS QDs were tethered to TiO2 nanoparticles through bifunctional mercaptoalkanoic acids (MAAs). Electron injection and interfacial charge recombination were characterized by steady-state emission quenching, nanosecond time-resolved emission, and nanosecond transient absorption. The electron injection yield decreased with increasing MAA chain length and interparticle separation. Electron injection occurred on multiple timescales. A fast component (