Self-assembled monolayer of 2-(((5-mercapto-1,3,4-thiadiazol-2-yl)imino)methyl)phenol (MTP) on gold surface: A platform for impedimetric and potentiometric sensing of mercury(II)

Abstract

2-(((5-mercapto-1,3,4-thiadiazol-2-yl)imino)methyl)phenol (MTP) was synthesized, self-assembled on the surface of gold (Au) electrode (Au-MTP) followed by characterization using Cyclic voltammetry (CV) and Electrochemical impedance spectroscopy (EIS). CV and EIS confirmed the formation of well-organized Au-MTP SAM free from defects and pinholes. Au-MTP was further utilized as a platform for sensing of Hg²⁺ using EIS. The results showed sensitive and selective response of Au-MTP towards Hg²⁺ in the linear concentration range from 1.0 × 10^-10 M to 1.0 × 10^-4 M with limit of detection (LoD) of 5.6 × 10^-11 M. Furthermore, MTP was self-assembled on gold nanoparticles (AuNPs) and MTP bound gold nanoparticles (MTP-AuNPs) so obtained were used as modifier for construction of carbon paste electrode (CPE). Hg²⁺-CPE exhibited Nernstian response towards Hg²⁺ with slope of 28.3 mV/decade in the concentration range from 1.0 × 10^-5 M to 1.0 × 10^-1 M with LoD of 6.3 × 10^-6 M. Both the Au-MTP EIS sensor and Hg²⁺-CPE were successfully applied for estimation of Hg²⁺ content in tap water samples.

Keywords: Electrochemical impedance spectroscopy; Hg(2+) detection; Potentiometry; Schiff base; Self-assembled monolayer.