(Digital Presentation) In-Situ Electro-Organic Synthesis and Functionalization of Catechol Derivative on Carbon Black and Its Interference-Free Voltammetric pH Sensing Application

Catechol, 1,2-dihydroxybenzene (1,2-DHB), is a well-known organic redox molecule and a potent biological electron-transfer mediator widely used in electrocatalysis, bio-electrocatalysis, energy-storage and pH sensing applications. Functionalization of catechol (CA) over the carbon-electrode is an essential step to achieving the desired application. There are several studies reported for the chemical synthesis of functionalized CA derivatives following surface immobilization procedure [1-3]. Indeed, preparation of a simple and stable catechol functionalized electrochemically modified electrode is a challenging task. For instance, 4-[2-(2-naphthyl)vinly]catechol and 4-[2-(9,10-ethanoanthracen-9-yl)vinlyl]catechol grafted graphite electrodes and a library of 26 different dihydroxy benzene derivatives covalently attached to glassy carbon via ethylenediamine and C 6 H 4 -CH 2 -NH linkers have showed serious surface fouling during their voltammetric experiments [1,4]. In this work, we report a simple in-situ electrochemical method for functionalizing catechol derivative (ferulic acid, FA) on a low-cost carbon black (CB) modified electrode surface suitable for voltammetric pH sensing. The precursor organic compound, FA has been electrochemically oxidized over the CB modified glassy carbon electrode, GCE/CB, by performing the electrochemical-potential treatment in pH 7 phosphate buffer solution that leads to a high redox-active surface-confined FA-catechol derivative (GCE/CB@FA-Redox). Cyclic voltammetric response of the GCE/CB@FA-Redox showed a well-defined and stable redox peak at a standard electrode potential, E o ’ = 0.160 V vs Ag/AgCl with a peak-to-peak potential difference, ∆E = 0.044 V vs Ag/AgCl and surface excess value, Γ = 1.88×10 -7 mol cm -2 . Unlike the previously reported CA-based chemically modified electrodes which showed a well-defined mediated oxidation reaction of cysteine (CySH), hydrazine and sulfide ion [5-7], the GCE/CB@FA-Redox modified electrode didn’t show any interference to common electroactive biochemicals and chemicals such as ascorbic acid, glucose, cysteine, caffeic acid, hydrazine, hydrogen peroxide, uric acid, dopamine, creatinine, urea, nitrite, sulfide and sulfate ions. There was no alteration in the peak potential and peak current responses in the presence of the chemicals mentioned above. It is a clear advantage of using this new redox electrode for the voltammetric pH sensing application. The surface orientation of the FA-R