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Pure Appl. Chem., 2004, Vol. 76, No. 4, pp. 789-799

Electrochemistry and application of a novel monosubstituted squarate electron-transfer mediator in a glucose oxidase-doped poly(phenol) sensor

E. I. Iwuoha, A. R. Williams-Dottin, L. A. Hall, A. Morrin, G. N. Mathebe, M. R. Smyth and Anthony Killard

Department of Chemistry, University of the Western Cape, Belleville 7535, South Africa; Department of Chemistry, The University of the West Indies, St.Augustine, Trinidad; School of Chemical Sciences, Dublin City University, Dublin 9, Ireland

Abstract: Electrosynthetic poly(phenol) nanofilms were deposited in situ on platinum electrodes in the presence and absence of glucose oxidase. The synthesis charges and currents of the nonconducting polymer films were recorded at various applied potentials for films grown from 25 –100 mM phenol concentrations. Film parameters such as the standard rate constant for film deposition, film thickness, and surface concentration of the poly(phenol) films were evaluated from the cyclic and step voltammograms of the polymerization process. A novel electron-transfer mediator consisting of monosubstituted 4-hydroxycyclobut-3-ene-1,2-dione (squarate) was used as a mediator for Pt/poly(phenol) nanofilm/GOx amperometric glucose biosensors. Amperometric responses for 3-diphenylamino-4-hydroxycyclobut-3-ene-1,2-dione (diphenylaminosquarate: E°'=of +328 mV/Ag-AgCl at pH 7.0)-mediated systems were measured by both steady-state amperometric and cyclic voltammetry. The sensor sensitivity was calculated to be 558 nA cm−2 (µM)−1.