ZnO Nanostructures and Their Photocatalytic Applications

Zinc oxide (ZnO) nanostructures encompass a diverse array of morphologies – from nanoparticles and nanorods to thin films and three-dimensional hierarchical architectures – all built upon the hexagonal wurtzite lattice. Their wide direct band gap (~3.3 eV) and large exciton binding energy render them highly active under ultraviolet illumination, while intrinsic and engineered defect states (oxygen vacancies, zinc interstitials) modulate visible-light absorption and charge separation. Controlled synthesis techniques – including hydrothermal growth, sol–gel routes, thermal oxidation and electrochemical anodization – yield tunable surface area, porosity and crystallographic orientation, crucial for enhancing photocatalytic performance. By promoting efficient generation and migration of photogenerated electrons and holes, ZnO nanostructures facilitate the formation of reactive oxygen species (hydroxyl and superoxide radicals), enabling degradation of organic contaminants, disinfection of microbial pathogens, and photoelectrochemical water splitting. Recent efforts focus on extending activity into the visible spectrum through metal or non-metal doping, designing heterojunctions with complementary semiconductors, and constructing immobilised films or hierarchical frameworks to improve stability and recyclability for environmental remediation and solar-fuel applications.

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ZnO Nanostructures and Their Photocatalytic Applications publication trend

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Technical terms

Wurtzite structure: Hexagonal crystal arrangement characteristic of ZnO, influencing optical and electronic properties.

Band gap: Energy difference between valence and conduction bands; for ZnO this is ~3.3 eV, dictating its light-absorption threshold.

Oxygen vacancy: Missing oxygen atom in the lattice that creates energy levels within the band gap, altering light absorption and charge trapping.

Facetted morphology: Nanoparticles with well-defined crystallographic faces, often exhibiting distinct defect distributions compared to spherical counterparts.

Photocatalysis: Process by which light-induced charge carriers in a semiconductor drive redox reactions, generating reactive species for pollutant degradation or fuel production.

References

1. Revealing the Dependency of Dye Adsorption and Photocatalytic Activity of ZnO Nanoparticles on Their Morphology and Defect States. Nanomaterials (2023).
2. Hierarchical 3D ZnO nanowire structures via fast anodization of zinc. Journal of Materials Chemistry A (2015).
3. Photocatalytic degradation of methylene blue at nanostructured ZnO thin films. Nanotechnology (2023).