气候变化领域集成服务门户

Effects of natural organic matter (NOM) on the photoreaction kinetics of fullerenes (i.e., C-60 and fullerenol) were investigated using simulated sunlight and monochromatic radiation (365 nm). NOM from several sources quenched (slowed) the photoreaction of C-60 aggregates in water (aqu/nC(60)), but sensitized (accelerated) photoreaction of fullerenol. Kinetic studies indicated that the quenching occurred through a static mechanism involving NOM molecules adsorbed on the aqu/nC(60) surface. Quenching constants for the photoreaction of aqu/nC(60) correlated approximately with optical parameters related to the aromaticity and molecular size of the NOM. Association of aqu/nC(60) particles with NOM was investigated indirectly via the study of the aggregation kinetics of colloidal C-60 in the presence and absence of NOM as a function of NaCl strength at pH 7. In contrast to aqu/nC(60), the photoreaction efficiencies of the hydrophilic fullerene, fullerenol, increased linearly with increasing NOM concentrations and kinetic parameters for the sensitized photoreactions increased as the spectral slope coefficients and ratio of absorption coefficients at 254 to 365 nm (E-2:E-3) of the NOM increased. The results indicate that triplet excited states of the NOM are key intermediates in the photosensitized reactions.