Specific iodide effect on surface-enhanced Raman scattering for ultra-sensitive detection of organic contaminants in water

Ultra-sensitive detection of target molecules by surface-enhanced Raman scattering (SERS) is crucial in a wide range of fields but remains a great challenge. In this work, we report a simple and effective protocol for obtaining highly SERS-sensitive probe by mixing iodide with silver sol. The specific iodide effect on the SERS sensitivity is systematically investigated. It is found that, iodide can effectively promote the SERS enhancement of anionic and cationic analytes, and I- ion has a higher activating effect on SERS than that of Cl- ion. The as-prepared SERS-active substrate demonstrates excellent enhancement for rhodamine 6G with a high Raman enhancement factor of 1.8 × 108, which allows the detection limit of 1.0 × 10-13 M. Our findings in this work should be important for the developing of SERS theory and ultra-sensitive detection applications.