Copper(II) adsorbed on SiO2/SnO2 obtained by the sol-gel processing method:: application as electrochemical sensor for ascorbic acid

With the objective of producing a material showing better conductive properties to be used as a support for electroactive species, a SiO2/SnO2 mixed oxide was prepared. The procedure for SiO2/SnO2 mixed oxide preparation using the sol-gel processing method, starting from tetraethylorthosilicate and SnI4 as precursor reagents, is described. SiO2/SnO2 with composition Sn = 15.6 wt% and S-BET = 525 m(2) g(-1), V-p = 0.28 ml g(-1), and D-p = 1.5 nm, where S-BET, V-p, and D-p are the specific surface area, the average pore volume, and the average pore diameter, respectively, was obtained. The X-ray photoelectron spectroscopy showed that the mixed oxide was thermally very stable for samples heat-treated at up to 1073 K. The Bronsted acid sites, probed with pyridine molecules for samples heat-treated at various temperatures, were chemically stable up to 473 K. Segregation of SnO2 crystalline phase was observed at 1473 K but no crystalline phase was verified for SiO2 at this temperature. The porous SiO2/SnO2 matrix was used as base for Cu(II) immobilization and an electrode was developed for application in electrochemical detection of vitamin C in tablets. (C) 2004 Elsevier Inc. All rights reserved.