Applications of π-conjugated organic small molecules in surface-enhanced Raman spectroscopy

Surface-enhanced Raman spectroscopy (SERS) has emerged as a powerful analytical technique for trace analysis owing to its exceptional sensitivity and unique molecular “fingerprint” recognition capability. However, the widespread application of traditional SERS substrates remains limited by factors such as high cost, poor biocompatibility, and unsatisfactory signal reproducibility. π-conjugated organic small molecules (π-COSMs), with their tunable electronic structures, high crystallinity, and superior charge-transfer properties, provide a promising strategy for developing novel SERS substrates. This review systematically summarizes recent advances in applying π-COSMs to SERS technology. Molecular engineering strategies, including precise modulation of energy levels and substituents within the conjugated system, have been shown to significantly enhance the chemical enhancement (CE) mechanism. Furthermore, constructing organic/two-dimensional material heterostructures enables a synergistic effect between electromagnetic enhancement and CE, substantially improving signal stability and detection sensitivity. These π-COSM-based substrates have shown significant potential in environmental monitoring, offering highly sensitive, selective, and fluorescence-free detection of microplastics and nanoplastics, antibiotics, and their interactions with bacteria. In summary, π-conjugated molecules open a new avenue for developing low-cost and biocompatible SERS platforms. Future research focusing on an in-depth understanding of structure-activity relationships and optimized design is expected to further promote the practical application of SERS technology in single-molecule science and real-time monitoring within complex environments.