Surface-enhanced Raman spectroscopy based on chemical-enhancement engineering

Surface-enhanced Raman scattering (SERS) has revolutionized molecular spectroscopy by enabling ultrasensitive detection with molecular fingerprint specificity. Although electromagnetic enhancement has driven the remarkable success of SERS, chemical enhancement (CE) has emerged as a fundamentally distinct mechanism that amplifies Raman scattering through interfacial electronic interactions while offering superior molecular selectivity, high signal reproducibility, and direct access to charge-transfer processes. Recent advances in molecular engineering, substrate engineering, and external-field regulation have enabled precise manipulation of molecular adsorption, energy-level alignment, electronic coupling, and photo-induced charge transfer, providing effective routes toward high-performance CE-SERS platforms. This review presents a comprehensive overview of these interfacial electronic modulation strategies from an engineering perspective. Representative approaches, including molecular adsorption and assembly, defect engineering, elemental doping, heterostructure construction, and optical and electrical field regulation, are systematically discussed and correlated with their respective enhancement mechanisms. Furthermore, the relationships among electronic structure reconstruction, charge-transfer dynamics, and Raman enhancement are elucidated to establish a unified framework linking interfacial electronic regulation with CE. Finally, current challenges and future opportunities for rationally designing high-performance CE-SERS substrates and multifunctional, multi-field-coupled sensing platforms are discussed, providing insights for next-generation Raman spectroscopy and molecular sensing technologies.