Dual cocatalyst loaded reverse type-I core/shell quantum dots for photocatalytic antibacterial applications

Abstract

Here, we combined the benefits of reverse type-I core/shell quantum dots (CSQDs) and co-catalysts to improve both the performance and durability of reverse type-I CSQDs in photocatalytic antibacterial applications. For this purpose, co-catalysts of Ag and PdS were loaded on the surface of ZnS/CdS CSQDs to facilitate the spatial separation and transfer of photogenerated electrons and holes in the as-synthesized CSQDs. Time-resolved and steady-state emission spectroscopy in the presence and absence of quenchers (electron quenching: NO₃⁻ and hole quenching: 4-methoxyphenol) was exploited to map out the distribution of the electron/hole wave functions in Ag-PdS/ZnS/CdS nanohybrids. The antibacterial activities of the as-synthesized samples were also studied using broth tube dilution and paper disc diffusion approaches against S. saprophyticus and E. coli as model strains of Gram-positive and Gram-negative microbes. The as-synthesized Ag-PdS/ZnS/CdS nanohybrid showed enhanced efficiencies in the photodecomposition of both Gram-negative and Gram-positive microorganisms compared to ZnS/CdS, ZnS and CdS. The roles of O₂˙⁻ and OH˙ in the bactericidal action of Ag-PdS/ZnS/CdS were investigated through chemiluminescence and fluorescence approaches, respectively. Finally, the simultaneous effects of radical species on lipid peroxidation and on the proteome were investigated.