Synthesis and Antimicrobial Applications of ZnO Nanostructures: A Review

ZnO nanostructures (ZnO NSs) are able to provide significant antimicrobial activity, ensuring high biocompatibility, good chemical stability, and low toxicity. Such versatility has led to great success of this nanomaterial for antibacterial, antifungal, and, more recently, antiviral applications. However, methods for the preparation of ZnO NSs must be properly selected for their end use. Moreover, ZnO NSs can also be cytotoxic to some extent. In this context, this review emphasizes some aspects relevant to the preparation as well as to the antimicrobial use of ZnO NSs. In particular, a brief overview of the sol-gel, hydrothermal, biogenic, and electrochemical approaches proposed for their synthesis is presented, highlighting advantages/drawbacks of each route in terms of scalability, simplicity, and efficacy. Next, the application of ZnO NSs in several fields is reported. This is followed by a discussion of the antimicrobial role of ZnO NSs, where antimicrobial mechanisms of action, possible cell resistance, and cytotoxicity of ZnO NSs are highlighted. We also discuss the role of ZnO NSs against different biothreats, such as bacteria and viruses. The future of such nanomaterials in this application field is addressed in the final part.