Green Palladium Nanoparticles Structure Property Mechanisms and Sustainable Applications

Green synthesis of palladium nanoparticles (PdNPs) using biological agents offers an ecofriendly alternative to conventional chemical methods, with growing applications in catalysis, pollutant degradation, and biomedicine. This review covers both foundational studies and recent advances from 2014 to 2025 in the green synthesis of PdNPs using plants, microbes, algae, and isolated biomolecules. It examines biological synthesis pathways, physicochemical properties, and multifunctional applications, with particular emphasis on structure–property–function relationships. Mechanistic insights into the roles of polyphenols, proteins, polysaccharides, and enzymes in Pd²⁺ reduction, nanoparticle nucleation, stabilization, and surface accessibility are discussed. Biogenic PdNPs have shown strong catalytic performance in C─C coupling reactions, nitrophenol and dye reduction, and Cr(VI) detoxification, while also exhibiting promising antimicrobial and anticancer activities. Recent developments, including microfluidic-assisted synthesis, hybrid nanocomposites, and bioengineered systems, have improved control over particle formation and expanded their practical potential. Nevertheless, important challenges remain, particularly in size control, reproducibility, mechanistic standardization, biosafety evaluation, and economic scalability. Overall, green PdNPs represent a promising platform for sustainable nanotechnology and circular economy strategies, especially when coupled with palladium recovery and reuse pathways.