Redox-active green-electrode: Plant-extract based rutin and caffeic acid functionalized MWCNT for scanning electrochemical microscopy imaging and selective electrocatalytic oxidative sensing of dopamine

Abstract

A straightforward, environmentally friendly, and rapid in-situ electrochemical functionalization of Rutin (Rut) and Caffeic acid (Caf) on a multiwalled carbon nanotube-modified glassy carbon electrode, denoted as GCE/MWCNT@Herb-Redox (Herb-Redox =redox active species from the plant extract), has been demonstrated. This method utilizes an eco-friendly, plant-based water extract from Indian Borage (Coleus amboinicus), referred to as IBE, as a precursor sample. The as-prepared molecular bio-electrode showed a well-defined and stable surface-confined redox response at standard electrode potentials, Eo’ = 0.160 and 0.200 V vs Ag/AgCl in pH 7 phosphate buffer solution. By performing physicochemical and molecular characterisations using TEM, SEM, UV–Vis, FTIR, high-performance thin-layer chromatographic techniques, it has been confirmed that Rut and Caf from the Herbal-plant were selectively immobilized on the MWCNT-modified electrode. Using scanning electrochemical microscopy (SECM), the electroactive sites of the molecular-electrode were mapped. The electrocatalytic function of the GCE/MWCNT@Herb-Redox was demonstrated by performing a dopamine (DA) oxidation reaction as a model system in pH 7 PBS using CV and amp-it techniques. The results showed 100—10,000 times increase in the DA- oxidation current response over the values quoted with many of the literature reports highlighting the efficient functionality of the new molecular electrocatalytic system. As a proof of concept, batch injection analysis based elegant dopamine sensing using screen-printed electrode/MWCNT@Herb-Redox as an electrochemical detector has been demonstrated and there is no biochemical interference was observed. Since the electrochemical approach follows a green chemistry route for the modification, this bioelectrode showed a new platform for eco-friendly electrocatalytic applications.