Green Synthesis of ZnO Nanoparticles and Potential Applications for Plant Growth and Improvement

Abstract

Zinc oxide nanoparticles (ZnONPs) have garnered increasing research interest because of their distinctive physicochemical characteristics, which have been employed in various fields, especially in agriculture. This has been premised on the role of elemental Zn, a trace metal in body metabolism and enzyme activities. Green synthesis techniques that use plant extracts as stabilizing and reducing agents are becoming more popular over conventional synthesis because of the popular belief that they are inexpensive, biocompatible and environmentally friendly. Many types of green ZnONPs have been synthesized using several plant parts, zinc precursors and reaction conditions. These tend to influence the general attributes of the synthesized nanoparticles such as optical characteristics, the major functional groups involved in the synthesis, crystalline nature and morphology when characterized using UV-Visible Spectrophotometer, FTIR, XRD and TEM. Green synthesized ZnONPs have been found to elicit significant responses on crop plants, especially in seed germination and seedling vigor, morpho-agronomic characteristics, yield and proximate composition among others. All these are explored in this review with suggestions for further studies that will translate to potential application of green ZnONPs for plant improvement and production.