Electrocatalytic sensing of NADH at an in situ functionalized self-assembled monolayer on gold electrode

Abstract

In situ functionalization of a self-assembled monolayer (SAM) of an aromatic thiol, 4-aminothiophenol (4-ATP), on gold electrode in neutral pH yields a redox active monolayer of 4′-mercapto-N-phenylquinone diimine (NPQD). The in situ functionalized electrode shows an excellent electrocatalytic activity towards the oxidation of NADH with an activation overpotential, which is ca. 600 mV lower than that at the bare electrode. The sensitivity of the functionalized electrode towards the oxidation of NADH was found to be 0.0030±0.0003μA/μM. The electrode shows a linear response for a wide range of concentration (10–190 μM) and it can detect as low as 10 μM NADH at neutral pH. The mixed monolayer of cystamine (CYST) and NPQD is used to mitigate the interference of ascorbate (AA) in the measurement of NADH. The selective electrocatalytic sensing of NADH in the presence of AA at the mixed monolayer modified electrode is demonstrated for the first time.