Micro-/Nanomaterials for Surface-Enhanced Optical Biosensing

Optical biosensors are pivotal for their stability and high throughput, but their sensitivity often hinges on optical signal strength. Thanks to the combination of plasmonic nanostructures and spectroscopy, surface-enhanced spectroscopy (SES) has emerged as a powerful tool for identifying and characterizing trace molecular species with ultrahigh sensitivity. This technique holds broad application prospects in the field of optical biosensors, including surface-enhanced fluorescence (SEF), surface-enhanced Raman scattering (SERS), and surface-enhanced infrared absorption (SEIRA), which significantly improve the interaction intensity between photons and materials. This review elaborates on SES from the perspective of the combined system of SEF, SERS, and SEIRA, and summarizes the mechanism, micro-/nanomaterials structural design principles, and applications. A comprehensive review of the mechanisms from electromagnetic and chemical perspectives is provided. Reasonable micro/nanomaterial design strategies are then discussed to customize hot spots for different platforms with optimal enhancement. The review aims to emphasize the significant impact of micro-/nanomaterials in surface-enhanced optical biosensing. Besides, the progress of surface-enhanced biosensors around immunoassays, DNA/RNA, and other biomolecules is summarized. Finally, the challenges and future directions of the field are outlined.