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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.

Owing to the high-surface area and macromolecular architecture, metal-organic frame (MOF) material has been referred to as an advanced system for supercapacitor applications. Indeed, poor electrical property and structural instability under electrified conditions are the major limitations. In this work, we wish to introduce a new strategy for marked enhancement in the electrical and redox property of the MOF by simple chemical mixing followed by ultrasonication of pristine MOF with low-cost carbon black (CB) material. As a model system, Ni-MOF, prepared using 2,2’-bipyridine and benzene-1,4-dicarboxylic acid (provides a rich source for π-π interaction with graphic carbon), functionalized CB, designated as CB@Ni-MOF, has been developed for improved energy storage application. Electrochemical studies of CB@Ni-MOF modified screen-printed carbon electrode showed about ten times enhanced peak current and surface excess value (24.8 nmol.cm−2) over the respective pristine Ni-MOF modified electrode (1.9 nmol.cm−2) in 1 M NaOH solution. Physicochemical and electrochemical characterization using TEM, X-ray, Raman, FTIR, BET Surface area and electrochemical impedance measurements collectively revealed that there are multiple hydrogen-bonding interactions between the oxygen functional groups of Ni-MOF and CB, and strong π-π interaction between the aromatic units of Ni-MOF and sp2 carbon-graphitic sites of CB. These interactions help de-agglomeration and active-site inter-connection and a marked reduction in the multi-shell hollow structure of the CB (55nm→30nm). Capacitance measurement by galvanostatic charge and discharge (GCD) method yield value, 2700 F g−1 at a biased-current, 2 A g−1. It is about seven times higher than the values obtained with the respective pristine Ni-MOF (415 F g−1) and markedly higher than several literature-based MOF values. A GCD cyclic stability of the CB@Ni-MOF showed about 2% and 10% decrement at 2000 and 5000 cycles, respectively.