Metallic Nanostructures: An Updated Review on Synthesis, Stability, Safety, and Applications with Tremendous Multifunctional Opportunities

Metallic nanostructures play a vital role in technological advancement, providing exceptional performance and improved adaptability in comparison to their bulk equivalents. Conventional synthesis techniques frequently depend on dangerous reducing agents to transform metal ions into Nanoparticles (NPs), which presents considerable environmental and health issues. In contrast, the approach of green synthesis, which emphasizes the use of non-toxic reagents, has garnered significant interest as a sustainable method for the fabrication of Metallic Nanoparticles (MNPs). This sustainable approach utilizes biological sources, like actinomycetes, algae, fungi, polymers, crops, waste biomass, and yeast, recognized for their excellent biocompatibility, availability, affordability, and efficiency. Biological extracts act as reducing and stabilizing agents, with the metabolites and enzymes present in these extracts aiding in the conversion of metal ions into nanoparticles. This review offers an in-depth examination of different MNPs, such as copper, gold, platinum, silver, and zinc, emphasizing their distinct characteristics and a variety of synthesis methods. The review further explores the diverse applications of MNPs in biomimetics, agriculture, and various industrial sectors, including energy, catalysis, and wastewater treatment, along with optical enhancement. This review explores stability and toxicity profiles, filling a significant gap in the existing knowledge base and providing valuable insights into the broad applicability of MNPs.