Carbon Nanotubes Paste Electrodes. A New Alternative for the Development of Electrochemical Sensors

Abstract

In this work we summarize the recent activities of our group regarding the analytical performance of a new compositematerial, the so-called carbon nanotubes paste electrode (CNTPE) obtained by dispersion of multiwall carbonnanotubes in mineral oil. The electrocatalytic properties towards different redox systems, especially those involved inimportant enzymatic reactions are discussed. Significant shifting in the overpotentials for the oxidation and/orreduction of hydrogen peroxide, NADH, phenol, catechol, dopamine, ascorbic acid, uric acid and hydroquinone areobtained at CNTPE in comparison with the analogous graphite paste electrode (CPE). The usefulness of the electrodeas a matrix for immobilizing enzymes is also demonstrated. Highly sensitive and selective glucose quantification isaccomplished even without using permselective films or redox mediators. Enzymatic biosensors obtained byincorporation of lactate oxidase, polyphenol oxidase and alcohol dehydrogenase/NADþwithin the composite materialhave allowed the successful quantification of lactate, phenol, dopamine, catechin and ethanol. The sensitivequantification of traces of oligonucleotides and double stranded calf thymus DNA by adsorptive stripping is reported.The confined DNA layer demonstrated to be stable either in air, acetate or phosphate buffer. The advantages ofincorporating copper particles for the quantification of amino acids and albumin is also discussed.