Surface redox-mediated dihydronicotinamide adenine dinucleotide probes based on ionic liquids covalently bound with catechol functionality

A novel imidazolium-based ionic liquid (IL), covalently bound to catechol (CA) groups by carbodiimide-mediated coupling reactions, was synthesized and used as the electrochemical sensing probe for dihydronicotinamide adenine dinucleotide (NADH). The thin layer of the CA-functionalized IL (IL-CA) at the screen-printed carbon electrode (SPCE) exhibited a stable redox couple originating from the catechol/quinone at the terminus. The redox-active film-modified electrode exhibited high and persistent electrocatalytic activity at 0.32 V for the oxidation of NADH in pH 7.0 buffer solutions, while the oxidation reaction occurred at 0.75 V at the bare electrode. Moreover, the modified electrode also showed free of interference from ascorbic acid (AA) and uric acid (UA). Flow-injection amperometry was performed for 1–1000 μM of NADH under optimized conditions, and a linear calibration plot with a slope of 0.0078 μA/μM was obtained. The detection limit (S/N = 3) was 0.4 μM.