Comparative Photoactivity and Antibacterial Properties of C_(60) Fullerenes and Titanium Dioxide Nanoparticles

摘要

The production of reactive oxygen species (ROS) by aqueous suspensions of fullerenes and nano-TiO_2 (Degussa P25) was measured both in ultrapure water and in minimal Davis (MD) microbial growth medium. Fullerol (hydroxylated C_(60)) produced singlet oxygen (~1O_2) in ultrapure water and both ~1O_2 and superoxide (O_2~-) in MD medium, but no hydroxyl radicals (OH~·) were detected in either case. PVP/C_(60) (C_(60) encapsulated with poly(N-vinylpyrrolidone)) was more efficient than fullerol in generating singlet oxygen and superoxide. However, two other aggregates of C_(60), namely THFC_(60) (prepared with tetrahydofuran as transitional solvent) and aquC_(60) (prepared by vigorous stirring of C_(60) powder in water), were not photoactive. Nano-TiO_2 (also present as aggregates) primarily produced hydroxyl radicals in pure water and superoxide in MD medium. Bacterial (Escherichia coli) toxicity tests suggest that unlike nano-TiO_2 which was exclusively phototoxic, the antibacterial activity of fullerene suspensions was linked to ROS production. Nano-TiO_2 may be more efficient for water treatment involving UV or solar energy, to enhance contaminant oxidation and perhaps for disinfection. However, fullerol and PVP/ C_(60) may be useful as water treatment agents targeting specific pollutants or microorganisms that are more sensitive to either superoxide or singlet oxygen.