Control of Electron Transfer from Lead-Salt Nanocrystals to TiO₂

The roles of solvent reorganization energy and electronic coupling strength on the transfer of photoexcited electrons from PbS nanocrystals to TiO₂ nanoparticles are investigated. We find that the electron transfer depends only weakly on the solvent, in contrast to the strong dependence in the nanocrystal–molecule system. This is ascribed to the larger size of the acceptor in this system, and is accounted for by Marcus theory. The electronic coupling of the PbS and TiO₂ is varied by changing the length, aliphatic and aromatic structure, and anchor groups of the linker molecules. Shorter linker molecules consistently lead to faster electron transfer. Surprisingly, linker molecules of the same length but distinct chemical structures yield similar electron transfer rates. In contrast, the electron transfer rate can vary dramatically with different anchor groups.