Construction, application and challenges of metal-rGO composite SERS substrates: a review

Surface-enhanced Raman spectroscopy (SERS) technology enables the efficient detection of molecules and has become an efficient tool for decoding information on life. Constructing an appropriate nano-material structure is the key to improving the SERS performance. This review provides a systematic review of reduced graphene oxide (rGO)-based composite substrates for SERS, covering construction strategies, performance advantages, application progress, and remaining challenges. Owing to its tunable electronic structure, high specific surface area, and favorable biocompatibility, rGO enables synergistic electromagnetic and chemical enhancement after it has been integrated with noble metal nanostructures, thereby markedly improving the SERS sensitivity and selectivity while suppressing the fluorescence background. A detailed discussion is provided on how synthesis routes such as chemical co-reduction, pulsed laser reduction, and stepwise reduction can be leveraged to regulate the morphology and spatial distribution of metal nanoparticles on rGO. In terms of applications, these composite substrates have demonstrated high sensitivity detection of environmental pollutants, bioactive molecules, pathogens, and circulating tumor cells (CTCs), and have expanded into diverse platform formats ranging from rigid supports to flexible devices, microfluidic chips, and minimally invasive probes. Nevertheless, key challenges remain, including batch-to-batch substrate variability, insufficient hot spot uniformity, complex interfacial coupling mechanisms, and limited antifouling capability in complex biological matrices.