Mechanism of C60 photoreactivity in water: fate of triplet state and radical anion and production of reactive oxygen species.
The mechanism involved with (1) energy and electron transfer by C60 in the aqueous phase during UV irradiation and (2) subsequent production of reactive oxygen species (ROS) such as singlet oxygen and superoxide radical anion was investigated. Electron paramagnetic resonance (EPR) study showed that C60 embedded in micelles of nonionic surfactant (Triton X 100) or anionic surfactant (sodium dodecylbenzenesulfonate) produced ROS, but aggregated C60 did not, consistent with our earlier findings made using indicator chemicals. Nanosecond and femtosecond laser flash photolysis showed that the aggregation of C60 significantly accelerates the decay of excited triplet state C60, which is a key intermediate for energy and electron transfer, thus blocking the pathway for ROS production. This finding suggests that C60 clusters will not contribute to oxidative damage or redox reactions in natural environment and biological systems in the same way molecular C60 in organic phase reportedly does. In contrast, C60 embedded in surfactant micelles produces ROS and the evidence is presented for the formation of C60 radical anion as an intermediate.
Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Jaesang
J
Lee
Yoko
Y
Yamakoshi
Joseph B
JB
Hughes
Jae-Hong
JH
Kim
D000838:Anions; D002250:Carbon Radioisotopes / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D037741:Fullerenes / Q000737:chemistry*; D007700:Kinetics; D008823:Micelles; D017830:Octoxynol / Q000494:pharmacology; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species; D013481:Superoxides / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry*
D000838:Anions; D002250:Carbon Radioisotopes; D005609:Free Radicals; D037741:Fullerenes; D008823:Micelles; D017382:Reactive Oxygen Species; D013501:Surface-Active Agents; D014867:Water; D013481:Superoxides; D017830:Octoxynol; C069837:fullerene C60