Highly-efficient photoinduced electron transfer and long-lived charge separation in a polyelectrolyte environment

ORGN 289

Hui Jiang and Guilford Jones II. Department of Chemistry, and the Center for Photonics, Boston University, 590 Commonwealth Avenue, Boston, MA 02215
A self-assembly system showing highly-efficient photoinduced electron transfer and long-lived charge separation has been developed and characterized by UV/Visible absorption, steady-state fluorescence emission, fluorescence lifetime and nano-second laser flash photolysis measurements. Upon binding to negatively charged polyelectrolyte (PE) such as Poly-L-Glutamic Acid (PLGA), positively charged Spermine-Pyrene conjugate (Sp-Py) aggregates. Addition of Viologen, especially Heptyl Viologen (HV2+), quenches the Sp-Py dimer fluorescence highly-efficiently. Laser flash photolysis results show the radical ions (Py+ and HV+) produced by photoinduced electron transfer from Sp-Py to HV2+ in this system. Decay analysis of HV+ transient indicates a long-lived charge separation state (>> 1 µs). Based on our best knowledge, this self-assembly system is the first one that shows so efficient photoinduced electron transfer in which the chromophore and electrophore are non-covalently bound to a PE environment. Further investigation should provide insights into the understanding of the natural photosynthesis system.