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Effects of C60 on the Photochemical Formation of Reactive Oxygen Species from Natural Organic Matter
journal contribution
posted on 2016-10-06, 00:00 authored by Lijuan Yin, Huaxi Zhou, Lushi Lian, Shuwen Yan, Weihua SongBuckminsterfullerenes (C60) are widely used nanomaterials
that are present in surface water. The combination of C60 and humic acid (HA) generates reactive oxygen species (ROS) under
solar irradiation, but this process is not well understood. Thus,
the present study focused on the photochemical formation of singlet
oxygen (1O2), hydroxyl radical (HO•)-like species, superoxide radicals (O2•–), hydrogen peroxide (H2O2), and triplet excited
states (3C60*/3HA*) in solutions
containing both C60 and HA. The quantum yield coefficients
of excited triplet states (fTMP) and apparent
quantum yields of ROS were measured and compared to the calculated
values, which were based on the conservative mixing model. Although
C60 proved to have only a slight impact on the 1O2 formation from HA, C60 played a key role
in the inhibition of O2•–. The
photochemical formation of H2O2 followed the
conservative mixing model due to the reaction of C60•– with HO2•/O2•–, and the biomolecular reaction
rate constant has been measured as (7.4 ± 0.6) × 106 M–1 s–1. The apparent fTMP was significantly lower than the calculated
value, indicating that the steric effect of HA was significant in
the reaction of 3C60* with the TMP probe. In
contrast, C60 did not have an effect on the photochemical
formation of HO• from HA, suggesting that HO• is elevated from the hydrophilic surface of HA. The
aforementioned results may be useful for predicting the photochemical
influence of C60 on aqueous environments.