Oxido misto de SiO2/SnO2,SiO2/SnO2/Fosfato : propriedades e aplicações / The SiO2/SnO2, SiO2/SnO2/fosfato mixed oxide : properties and applications




The present work describes the preparation of SiO2/SnO2 mixed oxide obtained by the sol-gel processing method with Sn compositions (in wt %) of 4, 13 and 18%. The high specific surface and the presence of Lewis and Brfnsted acid sites, constitutes an interesting substrate for preparing new classes of chemically modified electrodes. In a specific application, the SiO2/SnO2 surface was modified with copper hexacyanoferrate. The resulting material can be represented as SnOH2/{Cu[Fe(CN)6]} where SnOH2 means the hydrated SnO2 in the silica matrix and it is formed according to the reaction SnOH + H SnOH2. It is a mixed valence compound with a zeolitic structure. The redox reaction can proceed through a solid compound because the zeolitic structure allows a flux of cations to go through its channels and holes. The new material SnOH2/{Cu[Fe(CN)6]} shows a high selectivity for ion exchange in aqueous supporting electrolytes, principally alkali metal cations: K, Na, Li, NH4when investigated by cyclic voltammetry. The potential of the SiO2/SnO2 binary oxide to immobilize electroactives species becomes even better when its surface was modified with phosphate ions. Adsorption of phosphoric acid on sol-gel SiO2/SnO2 mixed oxide, resulting in a phosphate species bonded to tin oxide, is an interesting procedure to increase the Brfnsted surface acidity. The solid acid obtained combines the characteristics of a rigid matrix conferred by the SiO2 skeleton, a high specific surface area due to the porous nature of the matrix and a high surface density of Brfnsted acid sites. These characteristic are desirable to immobilize a cationic metallated porphyrin species by means of electrostatic interaction viewing its use as an electron mediator in electrocatalytic reduction of dissolved oxygen and oxidation of nitrite ions in aqueous matrix using electrochemical techniques.


sol-gel sensor eletroquimico oxidos mistos electrochemical sensor carbon paste pasta de carbono sol-gels mixed-oxide

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