Hydrosphere pollution by organic pollutants of different nature (persistent dyes, phenols, herbicides, antibiotics, etc.) is one of the urgent ecological problems facing humankind these days. The task of water purification from such pollutants can be effectively solved with the help of modern photocatalytic technologies. This article is devoted to the study of photocatalytic properties of composite catalysts based on ZnO modified with plasmonic Ag nanoparticles. All materials were obtained by laser synthesis in liquid and differed by their silver content and preparation conditions, such as additional laser irradiation and/or annealing of produced powders. The prepared ZnO-Ag powders were investigated by electron microscopy, X-ray diffraction and UV-Vis spectroscopy. Photocatalytic tests were carried out with well- known test molecules in water (persistent dye rhodamine B, phenol and common antibiotic tetracycline) using LED light sources with wavelengths of 375 and 410 nm. The introduction of small concentrations (up to 1%) of plasmonic Ag nanoparticles is shown to increase the efficiency of the ZnO photocatalyst by expanding its spectral range. Both the preparation conditions and material composition were optimized to obtain composite photocatalysts with the highest efficiency. Finally, the operation mechanisms of the material with different distribution of silver are discussed.

Recently, the urgency of combating antibiotic-resistant bacteria, viruses, and other pathogens has dramatically increased. With the development of nanotechnology, significant hopes are placed on nanoparticles with antimicrobial properties. The efficiency of such materials can be significantly enhanced through light-activated processes. In this study, we prepared composite ZnO-Ag nanoparticles and tested their ability to inhibit Staphylococcus aureus bacteria. The composite ZnO-Ag nanoparticles were fabricated using pulsed laser ablation of Zn and Ag targets in water using a nanosecond pulsed laser. During antibacterial tests, light-enhanced activation of the nanoparticles was achieved using low-power near UV (375 nm) and blue visible (410 nm) LED irradiation. For comparison, similar laser-fabricated ZnO nanoparticles were also tested. The combined use of nanoparticles and LED irradiation significantly increased the generation of reactive oxygen species. As a result, low nanoparticle concentrations (0.05 g/L) and low-power LED irradiation (0.17–0.22 W) significantly reduced the concentration of Staphylococcus aureus bacteria, including experiments with visible light irradiation. Compared to their ZnO counterparts, the use of ZnO-Ag composite particles led to an additional increase in antimicrobial activity.

Bimetallic Au–Pt nanoparticles with different molar ratios were obtained using laser synthesis (Nd:YAG laser with the parameters: 1064 nm, 180 mJ, 7 ns, and 20 Hz). The bimetallic nature of the particles was confirmed by X-ray diffraction and UV-visible spectroscopy. According to the transmission electron microscopy data, it was found that the bimetallic nanoparticles were represented by the alloy particles of an elongated shape with a diameter of 5–10 nm. Then, the bimetallic particles were decorated with a powder of highly defective dark titania by impregnation.The photocatalytic activity of the TiO₂ with deposited bimetallic particles was estimated in the reactions of Rhodamine B dye decomposition and hydrogen production under LED irradiation with a wavelength of 375 nm. It was found that the highest photocatalytic activity in the series was exhibited by the samples with the deposited bimetallic particles, where the Au : Pt ratios was 50 : 50 and 30 : 70. It was also shown that the TiO₂ nanoparticles decorated with the bimetallic Au : Pt NPs exhibited higher activity compared to the samples successively modified with monometals in the same ratios.