Facile Synthesis of Cu-Doped ZnO Nanoparticles for the Enhanced Photocatalytic Disinfection of Bacteria and Fungi.

In this study, Cu-doped ZnO was prepared via the facile one-pot solvothermal approach. The structure and composition of the synthesized samples were characterized by XRD (X-ray diffraction), TEM (transmission electron microscopy), and XPS (X-ray photoelectron spectroscopy) analyses, revealing that the synthesized samples consisted of Cu-doped ZnO nanoparticles. Ultraviolet-visible (UV-vis) spectroscopy analysis showed that Cu-doping significantly improves the visible light absorption properties of ZnO. The photocatalytic capacity of the synthesized samples was tested via the disinfection of Escherichia coli, with the Cu-ZnO presenting enhanced disinfection compared to pure ZnO. Of the synthesized materials, 7% Cu-ZnO exhibited the best photocatalytic performance, for which the size was ~9 nm. The photocurrent density of the 7% Cu-ZnO samples was also significantly higher than that of pure ZnO. The antifungal activity for 7% Cu-ZnO was also tested on the pathogenic fungi of Fusarium graminearum. The macroconidia of F. graminearum was treated with 7% Cu-ZnO photocatalyst for 5 h, resulting in a three order of magnitude reduction at a concentration of 105 CFU/mL. Fluorescence staining tests were used to verify the survival of macroconidia before and after photocatalytic treatment. ICP-MS was used to confirm that Cu-ZnO met national standards for cu ion precipitation, indicating that Cu-ZnO are environmentally friendly materials.

Highly efficient Ti3+ self-doped TiO2 co-modified with carbon dots and palladium nanocomposites for disinfection of bacterial and fungi.

High efficiency photocatalysts capable of disinfecting a broad-spectrum microorganisms are needed for the practical application of photodisinfection technology. Herein, we synthesized a highly efficient photodisinfection catalyst composed of Ti3+ self-doped TiO2 decorated with carbon dots (CDs) and palladium nano-photocatalyst, designated as Pd/CDs/Ti3+-TiO2, via a facile hydrothermal-calcination approach. XPS and ESR analyses were performed to verify that the composite contained Ti3+, while TEM imaging and FTIR confirmed that the samples contained CDs. The as synthesized photocatalysts, particularly the 1% Pd/CDs/Ti3+-TiO2 sample, exhibited superior photocatalyzed antibacterial activity to pure TiO2 against E. coli (～6.5 orders of magnitude increase at 30 min). The 1% Pd/CDs/Ti3+-TiO2 photocatalyst also exhibited efficient photodisinfection of five pathogenic agricultural fungi. The dark cytotoxicity of the 1% Pd/CDs/Ti3+-TiO2 nanocomposites was evaluated on HepG2 and Chinese hamster lung (V79) cells via Cell Counting Kit-8 (CCK-8) and found to be minimal. Lastly, the recycling capacity for the photodisinfective activity of the nanocomposites was evaluated and found to be unchanged after five cycles. Four active species were identified as contributing to the photoinduced antimicrobial activity of the catalyst: h+, •O2-, •OH, and e-. Together, our results indicate that Pd/CDs/Ti3+-TiO2 nanocomposites have great potential in agricultural plant pathogen disinfection.