Effects of Introducing 2-aminoethanethiol into 4-pyridineethanethiol Self-assembled Monolayer Applicable to Enhance Sensitivity of Hg(II) Electrochemical Analysis

In our work, enhancement of sensitivity of Hg(II) determination by introducing 2-aminoethanethiol (AET) from solutions into the self-assembled monolayers (SAMs) of 4-pyridineethanethiol (PET) on gold nanoparticles (Au-NPs) capped on glassy carbon electrode was studied. The formation of binary SAMs was indicated by the shift of reductive desorption peak to negative potentials in voltammograms recorded in 0.5 M KOH solution. Effects of introduction AET were monitored by FTIR that there was a rapid increase of intensities at bands of 1296 and 1189 cm-1 ascribed to (C-H) ring deformation and (C-N) ring stretching, respectively, with increasing immersion time. However, these bands became lower with prolonging more time as well as increasing the concentration of AET in solution. These effects were interpreted due to the conformation of pyridine ring and formation of intermolecular hydrogen bonding between PET and AET. The differential pulse voltammetry for reoxidation of Hg(0) showed the increase of peak current induced by the first effect, whereas the later caused the decrease. Since the optimized conditions, the detection limit for the binary SAMs could approach to 3.85 × 10-12 M Hg(II), approximately three times lower than that of PET SAM.