Dimensionality and size effects in Surface-enhanced Raman scattering (SERS) substrates: From multidimensional nanomaterials to metal single-atom materials

Surface-enhanced Raman scattering (SERS) has evolved from a fundamental phenomenon to a powerful analytical technique, heavily reliant on the properties of the substrate. This review comprehensively summarizes recent advances in SERS substrates, with a specific focus on the pivotal role of dimensionality and size effects. We systematically discuss the characteristics and enhancement mechanisms of diverse nanomaterials. The emergence of metal single-atom materials as a new frontier, enabling exceptional charge transfer efficiency via local microenvironment engineering, is also highlighted. We elucidate how dimensional and size control tailor electromagnetic responses and chemical enhancement pathways, ultimately dictating SERS activity. Additionally, the review addresses prevailing challenges in substrate reproducibility, stability, and real-world application, while offering perspectives on future research directions. This work aims to deepen the understanding of size-dependent SERS effects and provide guidelines for designing highly sensitive substrates.