Electrochemical Oxidation of NADH in L-Cysteine Monolayer on Palladium Surface

The electrochemical oxidation of NADH has been evaluated using palladium surface modified with self assembled monolayer of L-cysteine. The alcohol dehydrogenase (ADH) enzyme was immobilized onto L-cysteine monolayer using different routes; adsorption physical or entrapment of the enzyme using Nafion as polymer. These modifications were analyzed with Fourier transform infrared (FT-IR) spectroscopy and electrochemical techniques. The FT-IR was used to characterize the immobilization process of ADH in L-cysteine monolayer. In cyclic voltammetry we use a redox probe as Fe(CN)63-/4- in KNO3 for study the kinetic of the system. Also, we studied the electrochemical oxidation of NADH in bare palladium and Pd modified with L-cysteine monolayer. The results show that L-cysteine monolayer assembly on the electrode surface facilitates the NADH oxidation, allowing the oxidation at a less positive potential. Finally, we studied the electrocatalytic activity toward the oxidation of ethanol in presence of ADH immobilized at L-cysteine monolayer and NAD+ in solution for the detection NADH on the palladium surface.