Photoinduced Triplet State Electron Transfer Processes From Ruthenium Containing Triblock Copolymers To Carbon Nanotubes

A light-harvesting triblock copolymer incorporated with pyrene and ruthenium complex photosensitizing moieties was synthesized and integrated into the dispersion and surface functionalization of multiwalled carbon nanotubes (MWCNTs) via noncovalent pi-pi interactions. Molecular dynamics simulation results show that the copolymer interacts with MWCNTs mainly through the pyrene blocks and that the Ru complex moieties far away from the MWCNT could preserve the charge-separated states of the electron donor-acceptor system after photo excitation. This new molecular structure serves as a good model for studying the fundamental photophysics of light harvesting systems based on polymer/carbon nanotube hybrids. Results from femtosecond transient absorption spectroscopy show that the electron transfer process occurs within 383 ps from the Ru complex to MWCNT, which is much faster than the relaxation of the triplet metal-to-ligand charge transfer excited state of the Ru complex. The rapid electron injection process infers that this type of functional metalloblock copolymer/carbon nanotube hybrid material has promising application potentials in solar energy conversion or other light harvesting devices.