Phytochemical-engineered silver nanoparticles: surface functionalization, polymeric interfaces, and biomedical applications

Plant-based phytochemicals that operate as reducing and coordinating agents also create sustainable (green) frameworks for the construction of silver nanostructures (AgNPs). This review covers the inorganic and coordination chemistry underlying phytochemical-mediated AgNPs formation, with special emphasis on electron-transfer reduction, nucleation and growth kinetics, surface capping or ligand-exchange processes to control crystal facets, morphology, and zeta potential in detail. We systematically compare the specific functions of major secondary metabolites as either multifunctional reductants and stabilizing ligands (e.g., flavonoids, phenolic acids, terpenoids, alkaloids) or proteins or carbohydrates. In addition, we analyze how important reaction parameters (pH, temperature, precursor-to-extract ratios, incubation time, and solvent systems) modulate the size, shape, and colloidal stability of the nanostructures by means of speciation and binding equilibria. This review discusses the assembly of AgNPs with polymeric interfaces (e.g., chitosan (CS), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and polyethylene glycol (PEG)) and advanced materials scaffolds, including metal–organic frameworks (MOFs), covalent organic frameworks (COFs), and 2D MXenes, bridging the gap between structure–property relationships and higher-level functional performance. They have found versatile applications across selective biomedical domains such as anticancer, antimicrobial, and antiviral therapies, along with environmental catalysis for photocatalytic degradation of emerging contaminants, which we summarize here. Finally, we tackle related ongoing bottlenecks in batch-to-batch reproducibility, ligand heterogeneity, scalability, and ecotoxicological fate. Bridging mechanistic understanding in inorganic chemistry with hybridisation of materials and assessments of safety, this review presents a rational basis for exploiting size-controlled, eco-safe, scalable silver nanostructures for next-generation sustainable biomedical and environmental technologies.