Renewable surface electrodes based on dopamine functionalized exfoliated graphite: NADH oxidation and ethanol biosensing

Abstract

Exfoliated graphite (EG) was modified by covalently attaching dopamine (DA) (3,4-dihydroxyphenethylamine) through amide linkages, using ---COOH groups introduced on the EG surface. The modified material was characterized by FT-IR spectroscopy, X-ray photoelectron spectroscopy and electrochemical techniques. Composites of DA modified EG dispersed in organically modified silicates were prepared by a sol-gel process. Electrodes were fabricated by casting the composites in glass tubes. The sol-gel based electrodes were found to be active for the electrocatalytic oxidation of NADH and biosensing of ethanol in presence of NAD⁺ and alcohol dehydrogenase enzyme. The modified composite electrodes were found to be stable for several months. The surface of the electrode could be renewed just by mechanically polishing the electrode using emery sheets. The modified EG was also pressed and restacked in the form of a pellet and the use of this material as a binderless bulk-modified electrode was also demonstrated. The performance of sol-gel derived composite EG electrodes with binderless bulk-modified EG electrodes was compared.