Quantitative surface-enhanced Raman scattering ultradetection of atomic inorganic ions: the case of chloride

Surface-enhanced Raman scattering (SERS) spectroscopy can be used for the determination and quantification of biologically representative atomic ions. In this work, the detection and quantification of chloride is demonstrated by monitoring the vibrational changes occurring at a specific interface (a Cl-sensitive dye) supported on a silver-coated silica microbead. The engineered particles play a key role in the detection, as they offer a stable substrate to support the dye, with a dense collection of SERS hot spots. These results open a new avenue toward the generation of microsensors for fast ultradetection and quantification of relevant ions inside living organisms such as cells. Additionally, the use of discrete particles rather than rough films, or other conventional SERS supports, will also enable a safe remote interrogation of highly toxic sources in environmental problems or biological fluids.