Meldola blue immobilized on a new SiO2/TiO2/graphite composite for electrocatalytic oxidation of NADH

Meldola blue immobilized on a new SiO2/TiO2/graphite composite was applied in the electrocatalytic oxidation of NADH. The materials were prepared by the sol-gel processing method and characterized by several techniques including scanning electronic microscopy coupled to energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electronic microscopy (HRTEM). Si and Ti mapping profiles Oil the surface showed a homogeneous distribution of the components. Ti2p binding energy peaks indicate that the formation of Si-O-Ti linkage is presumably the responsible for the high rigidity of the matrices. The good electrical conductivity presented by the composites (5 and 11 S cm(-1)) can be related to a homogeneous distribution of graphite particles observed by TEM. After the materials characterization, a SiO2/TiO2/graphite electrode was prepared and some chemical modifications were performed on its surface to promote the adsorption of meldola blue. The resulting system presented electrocatalytic properties toward the oxidation of NADH, decreasing the oxidation potential to -120 mV. The proposed sensor showed a wide linear response range from 0.018 to 7.29 mmol l(-1) and limit of detection of 0.008 mmol l(-1). SiO2/TiO2/graphite has shown to he a promising material to be used asa suitable support in the construction of new electrochemical sensors. (c) 2008 Elsevier Ltd. All rights reserved.