Photoinduced Electron Transfer on the Surfaces of Micelles

Abstract

Photoinduced electron transfer between N,N-dimethylaniline (DMA) and octadecylrhodamine B (ODRB) is studied on the surfaces of three alkyltrimethylammonium bromide micelles: dodecyl- (DTAB), tetradecyl- (TTAB), and hexadecyltrimethylammonium bromide (CTAB). The DMA and ODRB molecules are localized at the micelle surface. Time-resolved fluorescence and fluorescence yield data are presented and analyzed with the theoretical methods of ref 1. Lateral diffusion of the molecules over the micelle surfaces is included. Although the three micelles are structurally similar, pronounced differences in the electron-transfer kinetics are observed, with the overall amount of electron transfer increasing with alkyl chain length for the same DMA surface packing fraction. This result is attributed to differences in the solvent reorganization energy, possibly due to varying extents of water penetration into the headgroup regions of the three micelles. As the surfactant chain length increases, the solvent reorganization energy is reduced, resulting in faster electron transfer.