A green method to synthesize AuNPs/mpg-C3N4 nanocomposites for constructing anti-interference electrochemical sensing interface toward methylmercury

Abstract Methylated mercury is a bio-magnifier that readily crosses the blood-brain barrier exerting neurotoxic effects. Therefore, the development of a rapid and in situ method of methylmercury (CH3Hg+) detection is research priority. We report a sensitive electrochemical method for the detection of CH3Hg+ using a modified glassy carbon electrode with Au nanoparticles-graphitic carbon nitride (AuNPs/mpg-C3N4). The AuNPs/mpg-C3N4 nanocomposites was synthesized by photochemical method and characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), X-ray photoelectron spectroscopic (XPS), Fourier Transform Infrared Spectrometer (FTIR). The results showed that Au nanoparticles were successfully loaded on the surface of mpg-C3N4 and dispersed uniformly. AuNPs/mpg-C3N4 combined the excellent catalytic properties of AuNPs and unique structure of mpg-C3N4 to improve the electrochemical sensing performance of CH3Hg+. The AuNPs/mpg-C3N4 GCE show a high sensitivity for CH3Hg+ determination using Differential pulse stripping voltammetry (DPSV). The CH3Hg+ calibration curve is linear within 1 μg/L ∼25 μg/L. The sensitivity and detection limit of CH3Hg+ is 0.285 μA/μg−1L and 0.103 μg/L (S/N = 3), respectively. The Hg2+ shows chemical interference in CH3Hg+ detection, which is minimized by the addition of SnCl2 or Diethylene triamine pentaacetic acid (DTPA). We also determined the CH3Hg+ concentration of natural waters with a ±106% spike recovery. A newly developed AuNPs/mpg-C3N4 modified GCE sensor provides a promising platform for CH3Hg+ detection in natural water.