title: Copper (II) adsorbed on SiO(2)/SnO(2) obtained by the sol-gel processing method: application as electrochemical sensor for ascorbic acid.
abstract: With the objective of producing a material showing better conductive properties to be used as a support for electroactive species, a SiO(2)/SnO(2) mixed oxide was prepared. The procedure for SiO(2)/SnO(2) mixed oxide preparation using the sol-gel processing method, starting from tetraethylorthosilicate and SnI(4) as precursor reagents, is described. SiO(2)/SnO(2) with composition Sn=15.6 wt% and S(BET) = 525 m(2)g(-1), V(p)=0.28 mlg(-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 Brønsted acid sites, probed with pyridine molecules for samples heat-treated at various temperatures, were chemically stable up to 473 K. Segregation of SnO(2) crystalline phase was observed at 1473 K but no crystalline phase was verified for SiO(2) at this temperature. The porous SiO(2)/SnO(2) matrix was used as base for Cu(II) immobilization and an electrode was developed for application in electrochemical detection of vitamin C in tablets.
authors.affiliation: Instituto de Química, Unicamp, CP 6154, 13083-970 Campinas, SP, Brazil.
authors.forename: Lincoln A
authors.initials: LA
authors.lastname: Kurihara
authors.forename: Sergio T
authors.initials: ST
authors.lastname: Fujiwara
authors.forename: Rení V S
authors.initials: RV
authors.lastname: Alfaya
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Gushikem
authors.forename: Antonio A S
authors.initials: AA
authors.lastname: Alfaya
authors.forename: Sandra C
authors.initials: SC
authors.lastname: de Castro
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D004563:Electrochemistry / Q000379:methods*; D004577:Electron Probe Microanalysis; D006358:Hot Temperature; D008956:Models, Chemical; D044367:Phase Transition; D012821:Silanes / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013818:Thermogravimetry; D013997:Time Factors; D017971:Tin Compounds / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D012821:Silanes; D017971:Tin Compounds; C040733:tetraethoxysilane; D012822:Silicon Dioxide; D003300:Copper; C045358:stannic oxide; D001205:Ascorbic Acid