Laser flash photolysis study on photophysical and photochemical properties of C60 fine particles

Photophysical and photochemical properties of the C-60 fine particles (C60FP) which were prepared by the reprecipitation method were examined by the time-resolved fluorescence and laser flash photolysis methods. Fluorescence decay of the fine particles can be divided into two components: emission from free exciton and self-trapped exciton. Rapid decay of the broad absorption after nanosecond-laser excitation was attributed to triplet-triplet annihilation due to migration of energy of triplet state within the fine particle. After the annihilation, the energy of triplet state localized on C-60 molecule. Energy transfer from the localized C-60 triplet state in the fine particle was confirmed for energy accepters such as O-2 and beta-carotene. Photoexcitation of the C60FP in the presence of electron donor in solution resulted in photoinduced electron transfer. The reaction rate constant was one order smaller than that in solution, suggesting small collision frequency of the localized triplet state in C60FP Oxidation of the fine particle was also observed by using methylacridinuim ion and biphenyl as a sensitizer and a cosensitizer, respectively. (C) 2000 Elsevier Science S.A. All rights reserved.