Light-Induced Assembly of Metal Nanoparticles on ZnO Enhances the Generation of Charge Carriers, Reactive Oxygen Species, and Antibacterial Activity

Abstract

Increasing the photocatalytic activity of semiconductors by forming heterojunctions with metal improves their energy transfer efficiency and environmental remediation capabilities. However, our knowledge regarding the structure–activity relationship of semiconductor/metal hybrid nanostructures is lacking due to poor control over their physicochemical properties. Here, we report a facile way to make ZnO/metal hetero-nanoparticles by the mixing/irradiation process of ZnO and metal nanoparticles. The resultant products provide an expedient model to explore the effects of various metal NPs on light-induced electron/hole separation, reactive oxygen species (ROS) production, and antibacterial activities of ZnO NPs. Electron spin resonance spectroscopy was used to compare the effect of mixing Pt, Au, or Ag NPs at different sizes and concentrations with ZnO NPs on light-induced electron–hole separation and ROS production. The enhancing effect of metal NPs depends on particle size, composition, and mass ratio of the metal NPs to the ZnO NPs. Smaller-sized Pt NPs are more efficient in promoting charge carrier generation and ROS production. At 5 nm, Ag NPs promoted charge carrier generation more efficiently than Pt and Au NPs, but Pt NPs promoted ROS generation more efficiently than Au and Ag NPs. These results provide valuable strategy to design the synthesis of semiconductor/metal hybrid nanostructures and easy tailoring of ROS and charge carrier production.

Rational Design of W-Doped Ag3PO4 as an Efficient Antibacterial Agent and Photocatalyst for Organic Pollutant Degradation

“…The increase of this structural local disorder profoundly alters the properties of the material, leading to an enhanced e′–h • separation, which is directly proportional to the ROS production. 66 These species, in turn, are responsible for injuries to the plasmatic membrane of microorganisms and changes in the cytoplasmic region, rendering them inhomogeneous in comparison with healthy microorganisms. ROS is also associated with disintegration of DNA, RNA, and microbial proteins, causing severe cellular injuries, making them unviable.…”

Coumarin as a Quantitative Probe for Hydroxyl Radical Formation in Heterogeneous Photocatalysis

“…Despite the fact that heterogeneous photocatalysis was discovered almost half a century ago, numerous studies focusing on the fundamental physical chemistry of this process are still being published every year. Some of the most recent studies can be found in refs − . Presently, the primary focus is on the synthesis and characterization of photocatalysts that are tailored for specific applications, e.g., oxidative degradation of pollutants, reductive degradation of pollutants, or hydrogen production. − A general aim has been to produce photocatalysts that are activated by visible light, either to drive reactions with less energy input or to more closely match the solar spectrum.…”

“…Some of the most recent studies can be found in refs − . Presently, the primary focus is on the synthesis and characterization of photocatalysts that are tailored for specific applications, e.g., oxidative degradation of pollutants, reductive degradation of pollutants, or hydrogen production. − A general aim has been to produce photocatalysts that are activated by visible light, either to drive reactions with less energy input or to more closely match the solar spectrum. The catalytic efficiency of a photocatalyst can be increased by prolonging the lifetime of the hole–electron pair generated upon illumination.…”

Zn2+ leakage and photo-induced reactive oxidative species do not explain the full toxicity of ZnO core Quantum Dots

“…Recent reports highlight also the key role played by the ROS generated by ZnO NPs under light irradiation and even in the dark [8,9,[19][20][21][22][23]. ZnO is a semiconductor with a bandgap of 3.37 eV in the bulk state and is able to be activated by wavelengths equal of below 368 nm.…”