Electrochemistry of ABTS at Glassy Carbon Electrodes

Abstract

The electrochemical and the mass transport behavior of ABTS 2− /ABTS ·− (2,2 -azinobis(3ethylbenzothiazoline-6-sulfonate)) redox couple at glassy carbon electrode (GCE) in phosphate buffer solution (PBS, pH=4.4) is studied in detail by cyclic voltammetry combined with rotating disk electrode system. From the i-E curves recorded at different electrode rotating rate, rate constant, and transfer coefficient for ABTS 2− ABTS ·− +e reaction at GCE electrode and the diffusion coefficient of ABTS 2− in PBS are estimated to be 4.6×10 −3 cm/s, 0.28, and 4.4×10 −6 cm 2 /s, respectively. The transfer coefficient with a value of ca. 0.28 differs largely from the value of 0.5 that is always assumed in the literature. The origins for the difference of the rate constant determined and the challenges for estimating the standard rate constant are discussed. The performance for such ABTS 2− mediated bio-cathode toward oxygen reduction reaction is discussed according to the over-potential drop as well as current output limit associated with the charge transfer kinetics of ABTS 2− ABTS ·− +e redox reaction and/or the mass transport effect.

Multi walled carbon nanotube and polyaniline coated pencil graphite based bio-cathode for enzymatic biofuel cell

“…The currents for the oxidation and reduction peaks in air saturated buffer solution in presence of ABTS are clearly appeared at 0.556 V and 0.454 V for E1 and E2 bio-cathodes respectively. The value of reduction peak potential for laccase immobilized bio-electrode is close to the reported (0.35 V vs. Ag/AgCl at pH 4.5) in previous studies [21,28,29]. In a control experiment, the absence of redox peak for bio-electrodes without immobilized enzyme confirmed role of enzyme in oxygen reduction reaction.…”

Design of Laccase–Metal Organic Framework-Based Bioelectrodes for Biocatalytic Oxygen Reduction Reaction

“…The active site of this metalloprotein contains one mononuclear copper site (type-1 (T 1 ) center) which is situated near the substrate binding pocket and a trinuclear copper cluster (one T 2 and two T 3 copper centers) embedded in the protein structure. , The electroenzymatic reduction of oxygen by laccase proceeds through a ABTS-mediated 4-electron reduction mechanism, converting O 2 completely to H 2 O . This is a well-documented process previously reported for laccase/ABTS systems in solution − or laccase/ABTS coimmobilized on electrode surfaces. ,,,, It involves four steps. The first step is the reduction of the oxidation state of Cu 2+ at the T 1 site of laccase by ABTS to form the radical cation ABTS +• The T 1 copper center functions as the primary electron acceptor site and shuttles electrons through an histidine-cysteine-histidine transfer pathway to the T 2 /T 3 cluster Then oxygen is reduced by the reduced state of the central Cu ions at its T 2 and T 3 sites in laccase Lac­(Cu + , T 2 , T 3 )­ The last step in the catalytic cycle is the electrochemical reduction of the ABTS +• radical cation to regenerate ABTS …”

Stable ABTS Immobilized in the MIL-100(Fe) Metal-Organic Framework as an Efficient Mediator for Laccase-Catalyzed Decolorization

“…As indicated, the ABTS@MIL-100(Fe)-modified Pt electrode exhibited similar behavior with an ABTS-modified Pt electrode, while the MIL-100(Fe)/Pt electrode produced a very low redox peak. Indeed, the redox peaks observed between −0.20 and 0.60 V for the ABTS@MIL-100(Fe)/Pt electrode corresponded to the one-electron reversible redox process of ABTS [ 30 , 31 ].…”