Recent Progress in Ag-Nanoparticles-Based Hybrid Substrates for Surface-Enhanced Raman Spectroscopy: Mechanisms,...

Surface-enhanced Raman spectroscopy (SERS) has emerged as a powerful analytical technique for ultrasensitive molecular detection; however, practical sensing performance strongly depends on substrate architecture, hotspot stability, and interfacial interactions rather than plasmonic metal selection alone. Among various plasmonic materials, Ag nanoparticles (Ag NPs) remain the most widely investigated SERS components due to their outstanding electromagnetic enhancement (EM) capability, although their practical application is often limited by oxidation, signal instability, and poor reproducibility under complex operating conditions. In this review, we provide a comprehensive and architecture-oriented analysis of Ag NPs-based hybrid SERS substrates reported from 2020 to 2026, with emphasis on sensitivity, long-term material stability, reproducibility, and practical applicability. Major hybridization strategies, including Ag-metal, Ag-metal oxide, Ag-2D material, Ag-MOF, multi-component, and flexible hybrid systems, are comparatively discussed to elucidate the relationships among hybrid structure, hotspot engineering, interfacial charge transfer, and sensing performance. Comparative analysis reveals that SERS sensitivity cannot be predicted solely from EM, as effective hotspot utilization, molecular adsorption behavior, and chemical enhancement (CE) pathways also play decisive roles in determining analytical performance. Furthermore, recent advances in flexible and multi-component hybrid substrates demonstrate promising applicability for food safety, environmental monitoring, and biomedical sensing through improved stability, reproducibility, and matrix compatibility. Overall, this review proposes a unified structure-hotspot-charge-transfer framework and highlights current challenges, practical limitations, and future directions for the rational development of robust and application-ready Ag NPs-based hybrid SERS platforms.