Recyclable Raman chip for detection of trace Mercury ions

Due to enrichment effect of Mercury ions (Hg2+), even if the concentration of Hg2+ is very low, it will do harm to human health. Precise detection of trace Hg2+ is important for environment protection and human health monitoring. In this work, gold nanoparticles (AuNPs) are immobilized on the surface of ITO with aid of inositol-hexaphosphate as linker agent and then 4-pyridinethiol (4-MPy) is decorated to form a 4-MPy/AuNPs/ITO chip. 4-MPy in the chip acts two roles involving the capture agent for Hg2+ and Raman signal reporter. With the adding of Hg2+, the linear increase of SERS response of 4-MPy is in the range from 1.0 ppt to 100 ppb (R2 = 0.9896) and the limit of detection could be down to 1 ppt. The mechanism of the Raman chip was also explored by molecular simulation. It is found that the interaction between Hg2+ and the nitrogen atoms changes the electron distribution of pyridine ring and induces reorientation of the 4-MPy molecules tending to more perpendicular adsorption fashion with respect to AuNPs surface, which leads to enhancement of the intensity of the pyridine breathing vibration peak at 1093 cm−1. The as-prepared SERS sensor chip features excellent stability and reproducibility as well as could be reused. The rapid 4-MPy/AuNPs/ITO-chip-based Raman protocol with capability against interference is competent for monitoring trace Hg2+ in river water samples.