Green-Synthesized Nanoparticles for Sensing: From Molecular Mechanisms to Next-Generation Sensing Platforms

Green synthesis has emerged as a sustainable and mechanistically versatile strategy for fabricating nanomaterials with tunable physicochemical and interfacial properties for advanced sensing applications. Unlike conventional synthesis routes that depend on toxic chemicals, harsh reaction conditions, and post-synthetic functionalization, green synthesis integrates nanoparticle formation, stabilization, defect generation, and surface engineering within a biomolecule-rich environment. Biological entities such as plant extracts, microorganisms, proteins, polysaccharides, flavonoids, and polyphenols act as reducing and capping agents, producing intrinsically functionalized nanostructures with enhanced biocompatibility and sensing performance. Recent studies demonstrate that biomolecule-mediated synthesis strongly influences nucleation kinetics, morphology evolution, defect chemistry, electronic structure, plasmonic behaviour, and interfacial charge transfer, which collectively govern sensitivity, selectivity, and signal amplification in sensing systems. This Review critically discusses the mechanistic foundations of green nanoparticle synthesis and their use in electrochemical, fluorescence, colorimetric, SERS, and photoelectrochemical sensing platforms. Emphasis is placed on morphology engineering, defect-mediated electronic modulation, biomolecular corona formation, heterojunction design, and nano-bio interface engineering. Current challenges related to reproducibility, scalability, and mechanistic understanding are also highlighted, alongside future opportunities involving AI-assisted synthesis optimization and sustainable next-generation sensing architectures.