Boron-Doped Diamond Modified with 4-Mercaptopyridine-Functionalized Gold Nanoparticles for Trace Mercury Detection

Mercury ions (Hg2+) are highly toxic, which can contaminate the environment and cause serious harm to human health. In this work, we report a portable, high-performance, and reusable boron-doped diamond (BDD) electrochemical sensor, which takes the advantages of 4-mercaptopyridine-functionalized gold nanoparticles (4-MPY/Au NPs) as the sensing element. Due to the specific coordination between Hg2+ and nitrogen of pyridine, Hg2+ can be captured by the 4-MPY to form a Hg(pyridine)2 complex, which leads to the reduction of electrochemical activity at the electrode surface. The current variations are monitored by differential pulse voltammetry (DPV) in solution containing the [Fe(CN)6]3–/4– redox probe. Under optimal conditions, the proposed sensor exhibits an excellent logarithmic relationship in the range of 0.001–10 μg/L with a low limit of detection (LOD) of 0.358 ng/L. In addition, the sensor is validated with satisfactory recovery of tap water samples, demonstrating its potential for on-site monitoring of the water environment.