Importance and Analytical Perspective of Green Synthetic Strategies of Copper, Zinc, and Titanium Oxide Nanoparticles and their Applications in Pathogens and Environmental Remediation

Background: Nanotechnology is a promising field of science which deals with the production and utilization of material under nanoscale dimensions. The nanoscale regime provides exceptional applications in various fields of science due to its large surface to volume ratio and many valuable properties. Hence, the production and use of nanomaterials are the prominent areas of modern research. Amongst the nanomaterials, metal oxide NPs have gained much attention due to their vast number of applications in different areas, including electrochemical applications, dye degradation, catalysis, and are known to be the exceptional entities in the battle against different pathogens. The metal oxides are viably synthesized through chemical methods that require the use of many noxious chemicals. Henceforth, it is the demand of the modern world to carry out research on the synthesis of metal oxide nanomaterials through eco-friendly, greener, and non-toxic routes. Thus, various green methods are employed to engineer the metal oxide NPs by using different greener, cheaper, and eco-friendly sources, employing the use of plant extracts, bacteria, fungi and other biological bodies. The present review covered the green synthesis of CuO, ZnO, TiO2 NPs and their applicability towards different pathogens and environmental remediation reported from the year 2015 to date. Objective: The exceptional catalytic properties, environmental, and anti-microbial applications of metal oxide, especially CuO, ZnO, TiO2, are the main highlights of this review articles. The most cost-effective and greener routes for the synthesis of CuO, ZnO, TiO2, are discussed in the present review. To date, various green synthetic methods for the preparation of mentioned nanoparticles and their applicability towards different pathogens and degradation of different hazardous dyes with some electrochemical applications has been thoroughly covered in this review. Conclusion: The biosynthesis of metal oxide NPs using greener and eco-friendly approaches have been the attentive area in the last decade. Green synthesis requires chemical-free active components from biological sources, which act as both the reducing and stabilizing agent for the size and shapecontrolled production of NPs. The future vision of bacterial, fungal, and plant-mediated production of NPs includes the postponement of laboratory-based work to a large industrial scale, exposition of different phytochemicals involved in the biosynthesis of NPs using bioinformatics techniques and stemming the real mechanism involved in preventing the growth of pathogenic bacteria, fungi, and algae. The plant-mediated NPs can have diverse applications in the arena of pharmaceutical, food, and cosmetic industries, and thus, became a vital area of modern research.