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An amperometric biosensor for the determination of ethanol has been constructed. It comprises a multiwalled carbon nanotubes (MWNTs) conduit, a Nafion binder, and an alcohol dehydrogenase (ADH) function. The measurement of ethanol is based on the signal produced by beta-nicotinamide adenine dinucleotide (NADH), the product of the enzymatic reaction. The MWNTs are cylindrical with an outer diameter in the range 40-60 nm, an inner diameter in the range 2-5 nm, and a length of up to several micrometers. The homogeneity of the resulting nanobiocomposite film was characterized by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The performance of the MWNTs-Nafion-ADH nanobiocomposite modified glassy carbon electrode was examined using cyclic voltammetry and amperometry in presence of NADH and in the presence of ethanol. The electrocatalytic activity of MWNTs towards the oxidation of NADH has allowed an effective low-potential amperometric determination of ethanol. In the case of 6 mgmL(-1) ADH, the MWNTs-Nafion-ADH nanobiocomposite film displayed a sensitivity of 830 nAmM(-1), a linear range up to 0.1 mM, a detection limit of 3 microM, and a response time of about 4 s.

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