Photogenerated Charge Carriers and Reactive Oxygen Species in ZnO/Au Hybrid Nanostructures with Enhanced Photocatalytic and Antibacterial Activity

Abstract

Semiconductor nanostructures with photocatalytic activity have the potential for many applications including remediation of environmental pollutants and use in antibacterial products. An effective way for promoting photocatalytic activity is depositing noble metal nanoparticles (NPs) on a semiconductor. In this paper, we demonstrated the successful deposition of Au NPs, having sizes smaller than 3 nm, onto ZnO NPs. ZnO/Au hybrid nanostructures having different molar ratios of Au to ZnO were synthesized. It was found that Au nanocomponents even at a very low Au/ZnO molar ratio of 0.2% can greatly enhance the photocatalytic and antibacterial activity of ZnO. Electron spin resonance spectroscopy with spin trapping and spin labeling was used to investigate the enhancing effect of Au NPs on the generation of reactive oxygen species and photoinduced charge carriers. Deposition of Au NPs onto ZnO resulted in a dramatic increase in light-induced generation of hydroxyl radical, superoxide and singlet oxygen, and production of holes and electrons. The enhancing effect of Au was dependent on the molar ratio of Au present in the ZnO/Au nanostructures. Consistent with these results from ESR measurements, ZnO/Au nanostructures also exhibited enhanced photocatalytic and antibacterial activity. These results unveiled the enhanced mechanism of Au on ZnO and these materials have great potential for use in water purification and antibacterial products.

Antibacterial properties and toxicity from metallic nanomaterials

“…He et al constructed ZnO/Au hybrid nanostructures by the photoreduction method resulting in AuNPs of sizes smaller than 3 nm. 79 Size and density of AuNPs were controlled and manipulated by modification Composites made from polymeric nanofibers, such as CS systems, exhibit biocompatible, biodegradable, and favorable antibacterial properties. 80 Yan et al studied the fabrication of AuNRs encapsulated within PVA/CS hybrid nanofibers by electrospinning.…”

The antimicrobial activity of nanoparticles: present situation and prospects for the future

“…These effects are a result of the following factors: improved light absorption due to the surface plasmon resonance wavelength of Au; an altered band gap width of ZnO, which enhances the reactivity of photoinduced charge carriers; and increased efficiency of electron transport and charge carrier separation. 163 The activity of antibacterial ZnO can be altered by doping modification. For instance, ZnO NPs doped with fluorine generate more ROS than ZnO NPs, resulting in greater damage to bacterial cells.…”

In situ green synthesis of antimicrobial carboxymethyl chitosan–nanosilver hybrids with controlled silver release

“…30,31 The amount of silver released from the CMC-Ag hybrids and the initial amount of silver in the hybrids were evaluated by inductively coupled plasma-optical emission spectrometry To detect the cumulative amount of silver release, CMCAg1, CMC-Ag2, and CMC-Ag3 (10 mg) were separately immersed in 10 mL of phosphate buffer (pH 7.2) and incubated at 37°C under agitation (300 rpm). At specific time points (1,3,6,12,24,48,96,144,192, and 240 hours), samples were centrifuged, then 2 mL of the supernatants were removed for analysis and replaced by an equivalent volume of fresh media. The concentration (ppm) of silver in the release medium at the sampling time point was measured using ICP-OES analysis and then converted to the cumulative release amount (μg).…”

“…[1][2][3] Over the past few decades, the excessive use of antibiotics has allowed bacteria to develop resistance from continual exposure to conventional antibiotics. 4 The problem of decreasing effectiveness of our existing antibiotics is now recognized as a significant worldwide issue, and a new generation of antimicrobial agents to replace antibiotics is being researched and explored.…”