Fluorine-functionalized reduced graphene oxide-TiO2 nanocomposites: A new application approach for efficient photocatalytic disinfection and algicidal effect

Abstract

Using surface functionalization and related applications to 2D materials as innovative solutions to environmental pollution has gained considerable attention among researchers. Fluorinated graphene has derivative-based synergistic components with high thermal and chemical stability because of its structure and bonding. Fluorine-functionalized reduced graphene oxide (rFGO-TiO2) demonstrated enhanced hydrophilicity and wettability, highly efficient photocatalytic disinfection, and an algicidal effect. This study presents the hydrothermal synthesis of rFGO-TiO2 to realize antibacterial properties with high stability, which was conducted against the gram-negative bacteria Escherichia coli. To optimize antibacterial performance, the effects of multiple synthetic conditions were investigated. The antibacterial performance was optimized at an rFGO content of 1 wt%, hydrothermal temperature of 200 °C, and hydrothermal time of 1 h. The rFGO–TiO2 composite demonstrated an antibacterial efficiency of 5.76 log under ultraviolet A irradiation for 10 min and around 2 log under visible light. In the absence of light, rFGO–TiO2 took 6 h to reach an antibacterial efficiency of 6 log. Increasing the rFGO content and hydrothermal temperature beyond the optimal conditions reduced the antibacterial efficiency because of the excess rFGO and disruption of rFGO–TiO2 binding. Measurements with electron spin resonance spectroscopy confirmed that hydroxyl radicals and superoxide ions caused stress and damaged the membrane of a cell, which led to cell death.