Visible-light driven photodegradation on Ag nanoparticle-embedded fullerene (C60) heterostructural microcubes

Insights into the antibacterial activity and antibacterial mechanism of silver modified fullerene towards Staphylococcus aureus by multiple spectrometric examinations

Clarifying the antibacterial mechanism of silver (Ag)-based materials is of great significance for the rational design, synthesis, and evaluation of antimicrobials. Herein, detailed description of the antibacterial mechanism of a synthesized silver deposited fullerene material (Ag(I)-C60) towards Staphylococcus aureus was surveyed from the point of view of DNA damage by ultraviolet-visible spectroscopy (UV-vis), inductively coupled plasma mass spectrometry (ICP-MS), and liquid chromatography-mass spectrometry (LC-MS). The model material, Ag(I)-C60, was prepared by liquid-liquid interfacial precipitation method, and characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), thermos-gravimetric analysis (TGA), and nitrogen adsorption/desorption analysis. Ultra-efficient bacteriostatic rate of Ag(I)-C60 was found to be 88.98% under light irradiation for 20 min. UV-vis measurement of the composition changes of four DNA bases showed that they changed in the presence of Ag(I)-C60 under light irradiation, suggesting Ag(I)-C60 could destroy the cells and genetic material of Staphylococcus aureus and thereby inhibit its growth and reproduction. ICP-MS analysis demonstrated the releasing behavior of Ag+ from Ag-based materials. Finally, the transformation pathway of G, A, C, and T were measured by LC-MS, demonstrating the conversion of Adenine (m/z 136.06) to 8-OH-Ade (m/z 174.04). These collective results suggested that Ag(I)-C60 was a new ultra-efficient antibacterial by slowly releasing Ag+ in water and producing a large amount of ROS under light.

The strong interaction and confinement effect of Ag@NH2-MIL-88B for improving the conversion and durability of photocatalytic Cr(VI) reduction in the presence of a hole scavenger

Selectively regulating active factors in photocatalytic reactions by designing materials is one of the very important factors. Herein, we prepared spindle-like core-shell Ag@NH₂-MIL-88B composites (Ag@NM-88) by a two-step hydrothermal method. The as-prepared Ag@NM-88 displayed superior photocatalytic activity for Cr(VI) reduction under LED light, compared with the activities of pure NH₂-MIL-88B (NM-88) and Ag/NM-88 (Ag was deposited on NH₂-MIL-88B). The core-shell structure Ag@NM-88 was not only beneficial to the absorption of light but also beneficial to the separation of photogenerated e^- and h⁺. More importantly, it was further confirmed by active radical capture experiments and nitroblue tetrazolium (NBT) conversion experiments that the design of the core-shell structure could effectively prevent photogenerated e^- from combing with O₂ to form •O₂^-, so that photogenerated e^- directly reduced Cr(VI), thereby improving the reaction rate. In addition, it could still maintain good stability after 5 cycles, indicating that the construction of a core-shell structure is also conducive to improving stability. This work provides a strategy for selectively regulating the active components of photocatalysts, and provides new insights into the relationship between interfacial charge transfer and molecular oxygen activation in photocatalytic reduction Cr(VI) systems.