Antibacterial and photocatalytic activity of ZnO nanoparticles from Zn(OH)2 dehydrated by azeotropic distillation, freeze drying, and ethanol washing

- Zn(OH)2 was synthesized by precipitation.
- Four different dehydration procedures were used to prepare ZnO nanoparticles.
- Azeotropic distillation and freeze drying were the most effective method.
- High surface area powders showed superior photocatalytic and antibacterial activity.
- Photocatalytic and antibacterial behaviors are governed by similar mechanisms.

In this study, the antibacterial and photocatalytic activities of a series of ZnO nanoparticles (NPs) produced using different dehydration methods on as-prepared zinc hydroxide precipitates (Zn(OH)2) have been investigated. Oven drying, azeotropic distillation, freeze drying, and ethanol washing methods were compared for their ability to yield non-agglomerated powders after precipitation synthesis. β-Zn(OH)2 single phase was observed after ethanol washing, oven drying, and freeze drying procedures, while azeotropic distillation transformed β-Zn(OH)2 into ZnO before calcination. Nanosized powders with high surface areas were produced via sublimation during the freeze drying process, and by replacement of hydroxyl groups on the precipitate surface with butoxy groups during azeotropic distillation. Both the photocatalytic degradation of Rhodamine B and the antibacterial activity against the pathogens Escherichia coli and Staphylococcus aureus were enhanced for dehydration methods that increased the surface area of ZnO NPs, suggesting that both photocatalytic and antibacterial behaviors were governed by similar mechanisms.

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