Rapid and Ultrasensitive Detection of Mercury Ion (II) by Colorimetric and SERS Method Based on Silver Nanocrystals

Abstract It is significant for environmental protection and food safety to establish a rapid, sensitive, and reliable analytical method to detecting heavy metal mercury ions (II) (Hg2+). Here, a simple and rapid colorimetric method was developed for the micromole detection of Hg2+ ion using silver nanocrystals (Ag NCs) modified by Tris-base (TB). In order to further improve the sensitivity and reproducibility detection, self-assembled monolayer Ag NCs film at n-hexane-water interface was constructed as surface enhanced Raman scattering (SERS) active substrate for ultrasensitive detection of Hg2+. The self-assembly Ag NCs film was achieved by optimizing the concentration of octadecylamine with amino group in n-hexane solution. Meanwhile, 4,4’-dipyridyl (Dpy) was used as the SERS probe molecule to realize the specific recognition of mercury ions. A linear correlation of Raman intensity with Hg2+ concentrations was from 5 × 10-15 M to 1 × 10-10 M and the limit of detection (LOD) was 0.35 fM. The good reproducibility and recovery rate of SERS sensor based monolayer Ag film was also demonstrated. These results indicate that Ag NCs-based colorimetric and SERS sensors have great potential for Hg2+ detection in practical application.