Crucial Factors for Reproducible and Ultrasensitive Surface‐Enhanced Raman Spectroscopy Detection: Hot Spot Engineering and Molecular Delivery

ABSTRACT Surface‐enhanced Raman spectroscopy (SERS) has emerged as one of the most powerful techniques for ultrasensitive molecular sensing due to the advantages in providing unique fingerprint information with high sensitivity and noninvasive detection. Despite the remarkable enhancement factors achieved by conventional SERS substrates, their practical applications remain hindered by challenges related to signal uniformity, substrate stability, and reproducibility. Moreover, an equally crucial challenge remains: efficiently extracting and transporting trace amounts of target chemical or biological molecules from their highly diluted solutions to the tiny SERS hot spots. This issue remains unresolved and continues to hinder the widespread application of SERS for molecular sensing. To further improve SERS performance, the development of next‐generation SERS substrates has become a key focus of research. This review highlights recent advancements in SERS substrate design, with a particular emphasis on the rational engineering of plasmonic hot spot arrays and molecule delivery to enhance detection sensitivity and reliability. Ultimately, these developments are expected to pave the way for the next generation of SERS platforms, enabling their practical application in diverse areas such as chemical analysis, biomedical diagnostics, and environmental and food safety monitoring.