Vertically ordered silica mesochannels as preconcentration materials for the electrochemical detection of methylene blue

Abstract

Silica mesochannels (SMCs) vertically and regularly oriented to the surface of indium tin oxide (ITO) electrodes were prepared and utilized for preconcentration and detection of methylene blue (MB) in aqueous solution. The positively charged MB can be adsorbed to the SMCs by following the pseudo-first-order kinetic model. The negative value of ΔG=−34.73 kJ/mol derived from the Langmuir adsorption isotherm indicated the thermodynamic feasibility of the adsorption and the spontaneous nature of the process. Moreover, the adsorbed MB can undergo an electrochemical reaction on the ITO electrode at a suitable potential and the resulting electrical current can be utilized to quantify the MB in aqueous solution. A good analytical performance for MB with a linear range from 10 nmol/L to 1.0 μmol/L and a detection limit at the nmol/L level was obtained. We believe that such a platform consisting of SMCs perpendicularly tethered to the underlying electrode surface simultaneously allows enrichment and electrochemical detection and can be extended for the detection of various charged dyes, as well as many other charged species.