Characterizing Photochemical Transformation of Aqueous nC_(60) under Environmentally Relevant Conditions

摘要

Engineered nanomaterials may undergo transformation upon interactions with various environmental factors. In this study, photochemical transformation of aqueous nC_(60) was investigated under UVA irradiation. nC_(60) underwent photochemical transformation in the presence of dissolved O_2, resulting in surface oxygenation and hydroxylation as demonstrated by XPS and ATR-FTIR analyses. The reaction followed a pseudo-first order rate law with the apparent reaction rate constant of 2.2 × 10~(-2) h~(-1). However, the core of the nanoparticles remained intact over 21 days of irradiation. Although no mineralization or dissolution of nC_(60) was observed, experiments using fullerol as a reference fullerene derivative suggested likely dissolution and partial mineralization of nC_(60) under long-term UVA exposure. Aquatic humic acid reduced nC_(60) transformation kinetics presumably due to scavenging of reactive oxygen species. Results from this study imply that photochemical transformation is an important factor controlling nC_(60) physical and chemical properties as well as its fate and transport in the natural aqueous environment In addition, changes in nC_(60) surface chemistry drastically reduced C_(60) extraction efficiency by toluene, suggesting that the existing analytical method for C_(60) may not be applicable to environmental samples.