Si trova su / Altri legami
© 2021 American Chemical Society.Direct electrooxidation of β–nicotinamide adenine dinucleotide (NADH) to NAD+ is associated with high irreversibility, requirement of large activation energy (i.e., large oxidation overpotential), and poisoning/passivation and fouling of the electrode surface owing to the adsorption of the oxidized form (NAD+) and intermediate radicals. These performance–hindering factors have so far resisted the development of an efficient NADH probe. With the objective of developing a suitable NADH probe, having reduced oxidation overpotential, and enhanced electron–transfer rate, the present study demonstrates the fabrication of an electrochemical sensing platform, which is based on the integration of a redox mediator and imidazolium ionic liquid (IL) on the reduced graphene oxide (rGO) matrix. For this purpose, a redox mediator, azure A (AzA) dye, was immobilized on the IL, which was grafted covalently on rGO nanosheets, for the voltametric and amperometric determination of NADH. It was found that the incorporation of AzA into the rGO–IL significantly enhanced the electrooxidation of NADH. More precisely, the covalent functionalization of the rGO matrix by the IL resulted in a decrease in the NADH oxidation peak by 120 mV. Again, the immobilization of AzA on the rGO–IL matrix (i.e., rGO–IL–AzA) caused a reduction of the NADH oxidation peak by 280 mV from that observed for rGO–AzA. It was further observed that the amperometric current in the rGO–IL–AzA film was amplified by ∼3.7 and ∼32 times compared to rGO–IL and rGO–AzA films, respectively. It is worth noting that the observed applied potential for recording amperometric current is the lowest reported until date. This improved response can be attributed to the synergistic effect that facilitated charge propagation via the rGO–IL–AzA matrix.
