Development of a ferrocene-tethered ionic liquid modified electrode for non-enzymatic electrochemical sensing of NADH

Sensitive and selective determination of reduced nicotinamide adenine dinucleotide (NADH) has gained momentum in healthcare monitoring as it plays a pivotal role in living organisms. In this work, we have designed a redox-active ionic liquid by tethering an ionic liquid to a prominent redox mediator, viz., ferrocene (Fc) for the electrochemical determination of NADH. The Fc-tethered ionic liquid (Fc-PF6-IL) thus synthesized was thoroughly characterized and then immobilized on the glassy carbon electrode surface to form Fc-PF6-IL/GCE and used as the sensing probe. Initially, the fabricated sensor was electrochemically characterized, which revealed a pair of distinct redox peaks due to ferrocene mediator with enhanced peak currents. Further, the fabricated sensor was utilized for the electrochemical sensing of NADH, which showed an excellent electrocatalytic behaviour towards NADH over concentration linearity from 20 to 825.6 µM with a detection limit and sensitivity of 5.3 µM and 157.88 µA/mM/cm2. The admirable electrochemical behaviour of the developed sensor could be due to the incorporation of IL into the Fc moiety, which favoured the electron transfer process as well as enhanced their electrochemical properties. Moreover, the fabricated sensor showed good potential cyclic stability and long-term storage stability with excellent anti-interference ability and reliable reproducibility. Furthermore, the practical applicability of the developed sensor was also explored by analysing real samples of NADH, which exhibited remarkable recoveries and thus making it a prominent electrochemical sensor for NADH sensing.