Surfactant-templated sol–gel silica thin films bearing 5-mercapto-1-methyl-tetrazole on carbon electrode for Hg(II) detection

Abstract

Surfactant-templated mesoporous silica films functionalized with 5-mercapto-1-methyl-1-H-tetrazole (MTTZ) groups have been deposited in one step onto glassy carbon electrodes. This was made by evaporation-induced self-assembly co-condensation of triethoxysilyl-propyl-5-mercapto-1-methyl-tetrazole and tetraethoxysilane in the presence of cetyltrimethylammonium bromide. After template extraction, the film was highly porous and enabled fast mass transport of redox probes from the surrounding solution to the electrode surface. This attractive feature, associated to the easy access to MTTZ binding sites in such ordered mesoporous environment, can be exploited for effective analyte preconcentration and sensitive subsequent electrochemical detection. This has been illustrated using Hg(II) as a model analyte. Interestingly, effective Hg(II) accumulation was possible at low pH values (i.e., where other metal ions are not bonded to the hybrid material) and detection was made by anodic stripping square wave voltammetry after medium exchange to an HCl-containing solution where analyte desorption was going on. After optimization of both preconcentration and detection steps, the sensor exhibited good sensitivity, a linear response in the sub-micromolar concentration range, and a detection limit down to the nanomolar one.