Use of biomimetic systems at the preparation of amperometric sensors / Utilização de sistemas biomiméticos no Preparo de sensores amperométricos

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

04/09/2009

RESUMO

This work describe the immobilization of the copper(II) dinuclear complex ([Cu2(apyhist)2Cl2](ClO4)2), (apyhist =[(4-imidazolyl)ethylene-2-amino-1-ethylpyridine]), and others similar copper(II) compounds mono- and tetranuclears, obtained in water solution or for desprotonation of the imidazole ligant, in the Nafion membrane on glass carbon electrode surface, for the development of an amperometric sensor for the analytical determination of hydrogen peroxide (H2O2). Study realized in the characterization of copper complex and the optimization of the system in differents conditions in order to obtain the best efficiency of the sensor. Parameters were evaluated as pH, potencial, ligant around the metal ion, volume of Nafion membrane, copper(II) amount, response sensibility and stability of the modified electrode to detect H2O2. Also, there was also the reactivity of the cyclic species tetranuclear (pH 9.0) imidazolate-bridged complex in the catalyses of the reduction of O2. The methodology developed proved to be efficient in the detection of H2O2, with response sensibility around the 0.360 A.cm-2.mol-1L, however, may be a possibility of degradation of Nafion membrane usinf the electrode, this possibly due to the fact that the degradation of this membrane is facilitaded in the presence of metal ions, due to the formation of OH radical, present in the reduction of H2O2. There was also evidence that the cyclic tetranuclear species allows a better catalyst in the amperometric response, which was determined by the highest sensibility obtained with this species. It was noticed, too, an efficient catalysts in the reduction of O2, with the involvement of four electrons, mimicking the process that occurs in copper enzymes such as laccase, ascorbate and bilirubin oxidase. A wire transfer is facilitated by the use of the modified electrode, suggesting that the metal center of the film works as a mediator for the reduction of O2. The sensibility is strongly influenced by changes in pH values (higher or lower than 8.0), probably due to change of the Schiff base copper(II) complex in equilibrium. This may be an indication that the tetranuclear species favors the recognition of the substrate cavity and promotes the electrocatalytic reduction of O2, since the pKa of the imidazole group of the mononuclear complex has a value closer (~8.5). The most important point of this research, however, was the fact that this is the first work that uses a copper(II) complex as a mimetic copper multinuclear system ever described in literature.

ASSUNTO(S)

bioinorganic sistemas biomiméticos complexos de cobre (ii) biossensores sistemas supramoleculares bioinorgânica enzymeless biosensors copper (ii) complexes biosensors supramoleculars systems quimica

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