Electrochemical Sensing Based on Redox Mediation at Carbon Nanotubes

Abstract

An electrochemical sensing platform was developed based on the integration of redox mediators and carbon nanotubes (CNT) in a polymeric matrix. To demonstrate the concept, a redox mediator Azure dye (AZU) was covalently attached to polysaccharide chains of chitosan (CHIT) and interspersed with CNT to form composite films for the amperometric determination of beta-nicotinamide adenine dinucleotide (NADH). The incorporation of CNT into CHIT-AZU matrix facilitated the AZU-mediated electrooxidation of NADH. In particular, CNT decreased the overpotential for the mediated process by an extra 0.30 V and amplified the NADH current by approximately 35 times (at -0.10 V) while reducing the response time from approximately 70 s for CHIT-AZU to approximately 5 s for CHIT-AZU/CNT films. These effects were discussed in terms of the AZU/CNT synergy, which improved charge propagation through the CHIT-AZU/CNT matrix. The concept of CNT-facilitated redox mediation in polymeric matrixes has a potential to be of general interest for expediting redox processes in electrochemical devices such as sensors, biosensors, and biological fuel cells and reactors.

Selective Detection of NADH with Neutral Red Functionalized Carbon Nanotube/Plasma-polymerized Film Composite Electrode

“…The similar results using by CNT and the other mediator have been reported. 6,11 However, our advantage of NR realized the lower potential (¹0.2 V) than those previous report (¹0.1 V 6,11 ). Figure 3 shows the steady-state amperometric response at ¹0.2 V vs. Ag/AgCl of the electrode.…”

Low-Potential Nicotinamide Adenine Dinucleotide Detection at a Glassy Carbon Electrode Modified with Toluidine Blue O Functionalized Multiwall Carbon Nanotubes

“…This phenomenon also existed in another study of Zhang and Gorsky. 16 This phenomenon may be due to aggregation of the TBO monomer. Figure 3 shows cyclic voltammograms of the TBOMWNTs/GC electrode in phosphate buffer (pH 7.0) at various scan rates in the range from 20 to 120 mV/s.…”

“…However, such modified surfaces displayed a rather limited stable ability and redox mediation capacity. The integration of phenothiazine derivatives and MWNTs in a polymeric matrix 16,17 for the determination of NADH with enhanced electrocatalytic characteristics was also reported, but the reported method was somewhat complicated. Hence, pursuing a simpler approach and new electrode materials to further decrease the overpotential for NADH oxidation and to minimize surface passivation effects to improve the detection sensitivity and redox mediation capacity is still an obvious challenge.…”

Electrochemical Sensors

“…98 Karyakin et al achieved even further reduction of the required oxidation potential, to just 0 V at physiological pH. 99 This was done by electropolymerization of the prosthetic FAD group that acted as electrocatalyst for NADH oxidation.…”

“…From the same group the electrochemical sensing based on the combination of redox mediation and CNTs was reported. 98 The authors co-immobilized a redox mediator, the phenothiazine derivatives of Azure dyes (AZU) and CNT in the chitosan biomatrix. The new sensing system amplified the NADH current 35 times and much reduced the response time compared to the system without CNT.…”