SiO_2/SnO_2/Sb_2O_5 microporous ceramic material for immobilization of Meldola's blue: Application as an electrochemical sensor for NADH

摘要

The mixed oxide SiO_2/SnO_2, containing 25wt% of SnO_2, determined by X-ray fluorescence, was prepared by the sol-gel method and the porous matrix obtained was then grafted with Sb (V), resulting the solid designated as (SiSnSb). XPS indicated 0.7% of Sb atoms on the surface. Sb grafted on the surface contains Br?nsted acid centers (SbOH groups) that can immobilize Meldola's blue (MB~+) cationic dye onto the surface by an ion exchange reaction, resulting the solid designated as (SiSnSb/MB). In the present case a surface concentration of MB+=2.5×10~(-11)molcm~2 on the surface was obtained. A homogeneous mixture of the SiSnSb/MB with ultra pure graphite (99.99%) was pressed in disk format and used to fabricate a working electrode that displayed an excellent specific electrocatalytic response to NADH oxidation, with a formal potential of -0.05V at pH 7.3. The electrochemical properties of the resulting electrode were investigated thoroughly with cyclic voltammetric and chronoamperometry techniques. The proposed sensor showed a good linear response range for NADH concentrations between 8×10~(-5) and 9.0×10~(-4)molL~(-1), with a detection limit of 1.5×10~(-7)molL~(-1). The presence of dopamine and ascorbic acid did not show any interference in the detection of NADH on this modified electrode surface.