Photochemical and antimicrobial properties of novel C₆₀ derivatives in aqueous systems

Four novel hexakis C₆₀ derivatives with varying functionalities were synthesized, and their photochemical properties and photodynamic disinfection efficiencies were quantitatively evaluated. All these C ₆₀ derivatives generated ¹O₂ more efficiently than commercial multihydroxylated C₆₀ (fullerol), as assessed by furfuryl alcohol consumption and electron paramagnetic resonance analysis. Despite significant agglomeration/aggregation in the aqueous phase to micrometer-sized particles, nanosecond laser flash photolysis showed that the lifetime of triplet state (a key intermediate for energy transfer responsible for ¹O₂ production) was comparable to reported values for pristine C₆₀ in organic phase. As a result of facile ¹O₂ production, the C₆₀ derivatives efficiently inactivated Escherichia coli and MS-2 bacteriophage. Cationic aminofullerene hexakis, which likely exerted electrostatic attraction, exhibited exceptionally rapid virus inactivation even compared to commercial nano-TiO₂ photocatalyst. These unique photodynamic, hydrophilic and cationic properties may be instrumental for the development of next generation photocatalysts for disinfection applications. The high ROS (reactive oxygen species) production activity and associated cytotoxicity are concerns for potential releases of functionalized C₆₀ to the environment, and require careful assessment apart from other forms of C₆₀ (e.g., nC₆₀) that have been widely studied as model nanomaterials but behave differently.