Antibacterial activity of zinc oxide nanoparticles (ZnO-NPs) has received significant interest worldwide particularly by the implementation of nanotechnology to synthesize particles in the nanometer region. Many microorganisms exist in the range from hundreds of nanometers to tens of micrometers. ZnO-NPs exhibit attractive antibacterial properties due to increased specific surface area as the reduced particle size leading to enhanced particle surface reactivity. ZnO is a bio-safe material that possesses photo-oxidizing and photocatalysis impacts on chemical and biological species. This review covered ZnO-NPs antibacterial activity including testing methods, impact of UV illumination, ZnO particle properties (size, concentration, morphology, and defects), particle surface modification, and minimum inhibitory concentration. Particular emphasize was given to bactericidal and bacteriostatic mechanisms with focus on generation of reactive oxygen species (ROS) including hydrogen peroxide (H2O2), OH− (hydroxyl radicals), and O2 −2 (peroxide). ROS has been a major factor for several mechanisms including cell wall damage due to ZnO-localized interaction, enhanced membrane permeability, internalization of NPs due to loss of proton motive force and uptake of toxic dissolved zinc ions. These have led to mitochondria weakness, intracellular outflow, and release in gene expression of oxidative stress which caused eventual cell growth inhibition and cell death. In some cases, enhanced antibacterial activity can be attributed to surface defects on ZnO abrasive surface texture. One functional application of the ZnO antibacterial bioactivity was discussed in food packaging industry where ZnO-NPs are used as an antibacterial agent toward foodborne diseases. Proper incorporation of ZnO-NPs into packaging materials can cause interaction with foodborne pathogens, thereby releasing NPs onto food surface where they come in contact with bad bacteria and cause the bacterial death and/or inhibition.

/pdf/review-on-zinc-oxide-nanoparticles-antibacterial-activity-2smaigi8sc.pdf

Review on Zinc Oxide Nanoparticles: Antibacterial Activity and Toxicity Mechanism.

Persistent organic pollutants (POPs) are carbon-based chemical substances that are resistant to environmental degradation and may not be completely removed through treatment processes. Their persistence can contribute to adverse health impacts on wild-life and human beings. Thus, the solar photocatalysis process has received increasing attention due to its great potential as a green and eco-friendly process for the elimination of POPs to increase the security of clean water. In this context, ZnO nanostructures have been shown to be prominent photocatalyst candidates to be used in photodegradation owing to the facts that they are low-cost, non-toxic and more efficient in the absorption across a large fraction of the solar spectrum compared to TiO 2 . There are several aspects, however, need to be taken into consideration for further development. The purpose of this paper is to review the photo-degradation mechanisms of POPs and the recent progress in ZnO nanostructured fabrication methods including doping, heterojunction and modification techniques as well as improvements of ZnO as a photocatalyst. The second objective of this review is to evaluate the immobilization of photocatalyst and suspension systems while looking into their future challenges and prospects.

A review of ZnO nanoparticles as solar photocatalysts: Synthesis, mechanisms and applications

CuO nanostructures: Synthesis, characterization, growth mechanisms, fundamental properties, and applications

ZnO nanowires (or nanorods) have been widely studied due to their unique material properties and remarkable performance in electronics, optics, and photonics. Recently, photocatalytic applications of ZnO nanowires are of increased interest in environmental protection applications. This paper presents a review of the current research of ZnO nanowires (or nanorods) with special focus on photocatalysis. We have reviewed the semiconducting photocatalysts and discussed a variety of synthesis methods of ZnO nanowires and their corresponding effectiveness in photocatalysis. We have also presented the characterization of ZnO nanowires from the literature and from our own measurements. Finally, a wide range of uses of ZnO nanowires in various applications is highlighted in this paper.

/pdf/synthesis-characterization-and-applications-of-zno-nanowires-1a5kdv4lbi.pdf

Synthesis, characterization, and applications of ZnO nanowires

Photocatalysis is an ecofriendly technique that emerged as a promising alternative for the degradation of many organic pollutants. The weaknesses of the present photocatalytic system which limit their industrial applications include low-usage of visible light, fast charge recombination, and low migration ability of the photo-generated electrons and holes. Therefore, various elements such as noble metals and transition metals as well as non-metals and metalloids (i.e., graphene, carbon nanotube, and carbon quantum dots) are doped into the photocatalyst as co-catalysts to enhance the photodegradation performance. The incorporation of the co-catalyst which alters the photocatalytic mechanism was discussed in detail. The application of photocatalysts in treating persistent organic pollutants such as pesticide, pharmaceutical compounds, oil and grease and textile in real wastewater was also discussed. Besides, a few photocatalytic reactors in pilot scale had been designed for the effort of commercializing the system. In addition, hybrid photocatalytic system integrating with membrane filtration together with their membrane fabrication methods had also been reviewed. This review outlined various types of heterogeneous photocatalysts, mechanism, synthesis methods of biomass supported photocatalyst, photocatalytic degradation of organic substances in real wastewater, and photocatalytic reactor designs and their operating parameters as well as the latest development of photocatalyst incorporated membrane.

An overview of photocatalytic degradation: photocatalysts, mechanisms, and development of photocatalytic membrane

Zinc oxide (ZnO) and iron doped zinc oxide (ZnO/Fe) nanowires were synthesized on glass substrates through a conventional hydrothermal method and the nanowires were characterized by UV–visible spectrum, scanning electron microscope (SEM), X-ray diffraction (XRD), and Raman spectroscopy techniques, respectively. Photocatalytic activities of ZnO and ZnO/Fe nanowires were investigated in both UV and white light for degradation of organic contaminants (1, 2-dichlorobenzene ‘DCB’ and methyl orange ‘MO’) in water. The ZnO/Fe nanowires exhibit an improved photocatalytic activity compared to ZnO nanowires. The photocatalytic performance of the nanowires is also compared to P25 titanium oxide (TiO2) for degradation of DCB and MO. Interestingly, ZnO/Fe nanowires show superior photocatalytic activity than TiO2 in white light and a similar activity level under UV light. The results indicate that this photocatalyst is suitable for the decontamination of organic materials under solar radiation.

Enhanced photocatalytic activity of iron doped zinc oxide nanowires for water decontamination

A simple photolytic reactor employing Ag-doped ZnO nanowires for water purification

Effect of photocatalytic surface roughness on reactors effectiveness for indoor air cleaning

/pdf/modeling-and-design-of-photocatalytic-reactors-for-air-nn5r4wye5s.pdf

Yangyang Zhang

Papers

Synthesis, characterization, and applications of ZnO nanowires

Enhanced photocatalytic activity of iron doped zinc oxide nanowires for water decontamination

A simple photolytic reactor employing Ag-doped ZnO nanowires for water purification

Effect of photocatalytic surface roughness on reactors effectiveness for indoor air cleaning

Modeling and Design of Photocatalytic Reactors for Air Purification