Two dimensional layered material based electrochemical reduction oxidation of nicotinamide adenine dinucleotide NAD a kinetic investigation

Abstract

Nicotinamide adenine dinucleotide (NAD) is an important coenzyme that participates in several biochemical reactions and has wide applications in electrochemical sensors, bio-fuel cells and bio-catalysis. The bio-electrochemistry of NAD is complex and involves side reactions. In this work, the electrochemical kinetics of NAD is investigated on graphene and its analogues viz. Graphene oxide (GO) and chemically reduced graphene oxide (CRGO) using several electrochemical techniques. Initially GO and CRGO were synthesized using modified Hummer s method and were subjected to characterization such as transmission electron microscopy (TEM), X-Ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), Raman spectroscopy and UV-Visible spectroscopy. The direct oxidation of NAD produces NAD+ along with NAD2 as side product. From cyclic voltammetry studies it is found that CRGO/GCE exhibited better electrocatalytic properties. The number of electrons transferred, calculated from hydrodynamic voltammetry, indicated the possible formation of NAD2 during the oxidation. Further, the interfacial properties of the electrode were studied using electrochemical impedance spectroscopy (EIS). Subsequently, the oxidation reaction was studied in the presence of a mediator: Prussian Blue (PB). The mediated oxidation exhibited a higher rate constant, kobs for CRGO/GCE (5.95x106 M-1s-1) than GO/GCE (2.34x106 M-1s-1). The elucidation of number of electrons transferred showed possible interference from PB, thereby a conclusive remark on the NAD2 formation could not be ascertained. newline newline