title: Effects of C60on the Photochemical Formation of Reactive Oxygen Species from Natural Organic Matter.
abstract: Buckminsterfullerenes (C60) are widely used nanomaterials that are present in surface water. The combination of C60and 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 C60and 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 C60proved to have only a slight impact on the1O2formation from HA, C60played a key role in the inhibition of O2•-. The photochemical formation of H2O2followed 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) × 106M-1s-1. The apparent fTMPwas significantly lower than the calculated value, indicating that the steric effect of HA was significant in the reaction of3C60* with the TMP probe. In contrast, C60did 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 C60on aqueous environments.
authors.affiliation: Department of Environmental Science & Engineering, Fudan University , Shanghai 200433, P. R. China.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Yin
authors.affiliation: Department of Environmental Science & Engineering, Fudan University , Shanghai 200433, P. R. China.
authors.forename: Huaxi
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Department of Environmental Science & Engineering, Fudan University , Shanghai 200433, P. R. China.
authors.forename: Lushi
authors.initials: L
authors.lastname: Lian
authors.affiliation: Department of Environmental Science & Engineering, Fudan University , Shanghai 200433, P. R. China.
authors.forename: Shuwen
authors.initials: S
authors.lastname: Yan
authors.affiliation: Department of Environmental Science & Engineering, Fudan University , Shanghai 200433, P. R. China.
authors.forename: Weihua
authors.initials: W
authors.lastname: Song
mesh_terms: D006861:Hydrogen Peroxide; D017665:Hydroxyl Radical / Q000737:chemistry; D055668:Photochemical Processes; D017382:Reactive Oxygen Species; D026082:Singlet Oxygen / Q000737:chemistry
chemical_list: D017382:Reactive Oxygen Species; D026082:Singlet Oxygen; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide