Biogenic Zinc Oxide Nanoparticles: Mechanism and Environmental Applications

Biogenic synthesis of nanoparticles is more rapid, eco-friendly and cost-effective technique that do not involve any harmful chemical during synthesis and stabilization. Various viruses, bacteria, fungi, algae and medicinal plants are used for developing green route for biological synthesis of nanoparticles. Although biogenic metal nanoparticles include gold, silver, copper, platinum, palladium and others, zinc oxide nanoparticles (ZnONPs) have gained more attention for their biocompatibility and photocatalytic potential. This chapter discusses about biogenic synthesis of ZnONPs along with its environmental applications. Several bacteria such as Bacillus licheniformis, Bacillus subtilis, Pseudochrobacterum sp., Rhodococcus pyridinivorans, and Serratia nematodiphila can synthesize ZnONPs which are flower-like, hair-like, spherical or hexagonal in shape. Similarly, fungi such as, Acremonium potronii, Alternaria tenuissima, and Aspergillus niger, can also synthesize ZnONPs which can photocatalytically degrade hazardous dyes like methylene blue and bismarck brown under ultraviolet and/or visible light. Further, algal extracts of Chlorella, Pterocladia capillacea, Sargassum muticum, and Ulva lactuca are employed to fabricate anisotropic ZnONPs with exotic shapes that includes rod, flower, triangle, hexagon and spheres which are mostly in size ranging from 10 to 50 nm with few exceptions. Similarly, plants such as, Abelmoschus esculentus, Allium cepa, Artocarpus heterophyllus, Azadirachta indica, Pheonix dactylifera, Prosopis juliflora, Ruellia tubersoa, and Salvia officinalis with rich phytochemical diversity can efficiently synthesize ZnONPs with high photocatalytic dye degrading potential metanil yellow, methyl orange, rhodamine B, reactive blue 21, turquoise blue, and others. The detailed mechanism behind bacteriogenic, mycogenic, phycogenic and phytogenic ZnONPs synthesis is also discussed along with the future perspectives.