Green synthesis of metal and metal oxide nanoparticles: a pathway to sustainable energy and sensing applications

Abstract Green synthesis offers a sustainable and cost-effective alternative to producing metal and metal oxide nanoparticles, employing biological reductants from plants, algae, bacteria, fungi, and more. These biological agents act as reducing and capping agents, facilitating nanoparticle formation under ambient conditions. This eco-friendly method is scalable, safe, and straightforward, making it a valuable approach in nanotechnology. This review examines the diverse methodologies for green synthesis, highlighting the biological reductants and optimized conditions for nanoparticle production. It also outlines characterization techniques, including structural, morphological, and chemical analyses, to ensure precise understanding of nanoparticle properties. The applications of green-synthesized nanoparticles are extensively explored. These include their use as electrode materials in supercapacitors and batteries, enhancing energy storage capabilities, and as catalysts in hydrogen production for sustainable energy solutions. Their role in thermal energy storage is emphasized, showcasing their efficiency in improving energy systems. Additionally, their application in sensing technologies is discussed where their high surface area and reactivity enable sensitive detection of chemical and biological agents. This review integrates synthesis methods, characterization approaches, and technological applications, offering a comprehensive overview of the potential of green-synthesized metal and metal oxide nanoparticles in advancing sustainable energy and sensing technologies.