Study on self-assembled monolayer of functionalized thiol on gold electrode forming capacitive sensor for chromium(VI) determination

A capacitive sensor based on S-{12-[1-(pyridin-4-ylmethyl)-1H-1,2,3-triazol-4-yl]dodecyl} ethanethioate (FT), a compound with a functional group exhibiting selective affinity towards Cr(VI) ions, was developed. FT was mixed with shorter-chain thiol-decanethiol (DT), to obtain an Au electrode surface well covered by a thiol monolayer. The composition and high quality of self-assembled monolayers (SAMs) were crucial factors influencing the performance of the capacitive sensor. In this work, SAMs formed from FT and DT mixtures with different compositions were studied. For physicochemical characterization of SAMs X-ray photoelectron spectroscopy (XPS), contact angle measurements as well as atomic force microscopy (AFM) were used. Cyclic voltammetry was employed to estimate an electrode surface coverage. Based on the obtained results, the composition of thiol layer providing the best parameters for capacitive sensing of chromium(VI) was chosen. Moreover, the analytical performance of sensor was verified.