Green chemistry approaches to nanomaterial synthesis for different applications

Green synthesis of nanoparticles (NPs) has attracted considerable attention as an alternative to conventional physical and chemical approaches because biological and renewable components in selected systems can function as reducing, complexing, and stabilizing agents and may facilitate the synthesis of NPs under relatively mild conditions. Specifically, plant-mediated synthesis, utilizes phytochemicals present in plant extracts to ease the reduction of metal ions and the subsequent nucleation, growth, and stabilization of NPs. This review discusses the recent advancement in the plant-mediated synthesis of metal and metal oxide NPs, with the important roles of phytochemicals, synthesis parameters, and proposed reaction mechanisms. The effect of reaction conditions, viz. , pH, temperature, reaction time, metal precursor concentration, and plant extract concentration, on NP size, morphology, and stability is also discussed. The biological and agricultural applications of plant-mediated NPs, including antimicrobial, antifungal, anticancer, and plant-growth-related applications, are studied together with their proposed mechanisms of action. The potential advantages of plant-mediated approaches, including the multifunctional role of phytochemicals and the possibility of reducing the use of selected conventional reducing or stabilizing agents are focused specifically. However, these approaches are not essentially sustainable, biocompatible, or scalable, and their environmental and biological performance depends on the plant source, extract composition, synthesis conditions, NP characteristics, and downstream processing. Challenges associated with extract variability, reproducibility, reaction time, yield, standardization, purification, and large-scale production are therefore critically discussed. Future development of plant-mediated NP synthesis will require improved process control, standardized extract characterization, quantitative assessment of environmental and biological effects, and validation of scalability to establish its practical and sustainable potential.