The Nanoalchemy of nature: A critical review of biogenic and sustainable pathways in green nanotechnology

With an emphasis on biologically based, environmentally safe processes that follow the principles of green chemistry, this thorough review critically assesses contemporary green synthesis methods for nanomaterials. It draws attention to the limitations of traditional synthesis methods, which usually involve potentially hazardous materials, require a significant amount of energy, and produce harmful byproducts. The study explores the evolutionary role of several biological agents in the continuous production of a broad variety of nanoparticles (e.g., Ag, Au, ZnO, CuO, Fe), including plant extracts, microorganisms (bacteria, fungi, algae), and enzymes. This review focuses on biologically mediated nanoparticle synthesis; green physicochemical techniques are discussed only in relation to benchmark sustainability, mechanistic insight, and scalability. The fundamentals of nanoparticle creation are examined, along with the role that enzymes and phytochemicals play. The article also discusses important characterization techniques for evaluating the properties of green-synthesized nanoparticles, as well as their numerous uses in energy and sensor technologies, water treatment, air purification, soil remediation, antibacterial and medicinal applications, and among other applications. By highlighting its potential to promote scalable, low-toxicity, and financially viable solutions for global sustainable development in line with the UN Sustainable Development Goals (SDGs) and the circular economy, this study offers helpful advice for advancing green nanotechnology by identifying research gaps, scaling issues, and new opportunities. • Explores biogenic nanomaterial synthesis as a sustainable alternative process. • Critically reviews plant-, microbe-, and biomolecule-mediated pathways for nanoparticle fabrication. • Renewable resouces, minimizes waste and energy through AI/ML model. • Identifies current limitations, knowledge gaps, and standardization issues hindering industrial-scale implementation.