Silver quantum dots in plasmonic photocatalysis: linking quantum confinement to structure-function relationships

Silver quantum dots (AgQDs) have emerged as a distinctive class of plasmonic nanomaterials that bridge the gap between conventional metallic nanoparticles and quantum-confined systems. Their unique electronic structure, surface atomic organization, and size-dependent optical properties have attracted increasing attention for photocatalytic applications. This review critically examines the fundamental structure-function relationships governing AgQD-enabled plasmonic photocatalysis, with particular emphasis on the transition from metallic behavior to quantum confinement and its implications for photocatalytic performance. Recent advances in understanding size-dependent electronic states, surface heterogeneity, plasmonic responses at the quantum limit, charge-carrier dynamics, and interfacial energy-transfer pathways are systematically discussed. The review further analyzes how these properties influence key photocatalytic processes, including hydrogen evolution, CO₂ reduction, environmental remediation, and photoelectrochemical conversion. Rather than considering AgQDs as simple plasmonic additives, emerging evidence highlights their multifunctional roles in light harvesting, charge management, interfacial modulation, and catalytic activation. By integrating mechanistic insights with application-oriented developments, this review identifies the key design principles linking quantum confinement to photocatalytic function. Finally, unresolved challenges, including mechanistic ambiguity, atomic-level control, interface engineering, and scalability, are discussed to outline future directions for the rational design of next-generation AgQD photocatalysts.