Plasmon-induced immobilization of xanthene chemosensors toward repurposing as SERS nanotags

Surface-enhanced Raman spectroscopy (SERS) has emerged as a powerful tool in biophysics, bioanalytical chemistry, and biomedicine due to its unique ability to monitor extracellular chemical activity using fiber optics and multiplexed detection, which are essential for the study of complex biological systems. However, the exceptionally limited choice of SERS nanotags has hindered the practical application of SERS sensing in the fields. Enormous efforts and time are needed to develop new nanotag lines from ab initio for different targeted analytes. This study is inspired by the extensive range of fluorescent chemosensors already in use for various applications and takes a pioneering step toward repurposing them as the SERS nanotags. More specifically, this study explores the potential of plasmon-induced aromatic radical substitution reaction to immobilize xanthene-based chemosensors onto plasmonic nanostructures using a chemical linker without pre-modifying the chemical structures of the chemosensors or compromising the functionality of their binding groups towards specific analytes. Using this proposed method, we immobilize two primary xanthene-based chemosensors and demonstrate their functionality as SERS chemosensors.