A colorimetric and surface-enhanced Raman scattering dual-signal sensor for Hg2+ based on Bismuthiol II-capped gold nanoparticles Original Research Article

The addition of Bismuthiol II to the gold nanoparticles (AuNPs) solution led to the aggregation of AuNPs with a color change from red to blue. As a result, hot spots were formed and strong surface-enhanced Raman scattering (SERS) signal of Bismuthiol II was observed. However, the Bismuthiol II-induced aggregation of AuNPs could be reversed by Hg2+ in the system, accompanied by a remarkable color change from blue to red. As evidenced by UV–vis and SERS spectroscopy, the variation in absorption band and SERS intensity was strongly dependent on the concentration of Hg2+, suggesting a colorimetric and SERS dual-signal sensor for Hg2+. The sensor had a high sensitivity, low detection limits of 2 nM and 30 nM could be achieved by UV–vis spectroscopy and by SERS spectroscopy, respectively. Other environmentally relevant metal ions did not interfere with the detection of Hg2+. The method was successfully applied to detect Hg2+ in water samples. It was simple, rapid and cost-effective without any modifying or labeling procedure.