Detection of NADH via electrocatalytic oxidation at single-walled carbon nanotubes modified with Variamine blue

• DOI: 10.1016/j.electacta.2007.09.031
• Publication Date: 2007-10-02T11:30:49Z
• Authors: A. Radoi; D. Compagnone; M.A. Valcarcel; P. Placidi; S. Materazzi; D. Moscone; G. Palleschi
• Keywords: Settore CHIM/01 - CHIMICA ANALITICA; l-lactate biosensor; nadh; single-walled carbon nanotubes; variamine blue; 01 natural sciences; 0104 chemical sciences

Abstract Screen-printed electrodes (SPEs) modified with Variamine blue (VB), covalently attached to the oxidized single-walled carbon nanotubes (SWCNTs-COOH), were developed and used as chemical sensors for the detection of the reduced nicotinamide adenine dinucleotide (NADH). The Variamine blue redox mediator was covalently linked to the SWCNTs-COOH by the N , N ′-dicyclohexylcarbodiimide (DCC) and N -hydroxysuccinimide (NHS) chemistry. Infrared Fourier transform (FT-IR) spectroscopy revealed the presence of the amide bands situated at 1623 cm −1 (I band), 1577 cm −1 (II band) and 1437 cm −1 (III band) demonstrating the covalent linkage of Variamine blue to SWCNTs-COOH. The heterogeneous electron transfer rate, k obs. , was 13,850 M −1 s −1 , and the k s and α were 0.8 s −1 and 0.56, respectively. The pH dependence was also investigated. SPEs modified with Variamine blue by using the DCC/NHS conjugation method, showed a variation of −36 mV per pH unit. A successful application was the development of a lactate biosensor obtained by the immobilization of the l -lactate dehydrogenase on the NADH sensor.