Department of Chemical Engineering, Sunchon National University;Nano and Bioelectrochemistry Research Laboratory, Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology University;Nano and Bioelectrochemistry Research Laboratory, Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology University;Department of Chemical Engineering, Sunchon National University;
K. Chandrasekara Pillai;K. S. Shalini Devi;Annamalai Senthil Kumar;Il-Shik Moon;
DPPH (2,2-diphenyl-1-picrylhydrazil), a free radical-containing organic compound, is used widely to evaluate the antioxidant properties of plant constituents. Here, we report an efficient electroactive DPPH molecular system with excellent electrocatalytic sensor properties, which is clearly distinct from the traditional free radical-based quenching mechanism. This unusual molecular status was achieved by the electrochemical immobilization of graphene oxide (GO)-stabilized DPPH on a glassy carbon electrode (GCE). Potential cycling of the DPPH adsorbed-GCE/GO between ??1 and 1?V (Ag/AgCl) in a pH 7 solution revealed a stable and well-defined pair of redox peaks with a standard electrode potential, E _(0)′?=?0?±?0.01?V (Ag/AgCl). Several electrochemical characterization studies as well as surface analysis of the GCE/GO@DPPH-modified electrode by transmission electron microscopy, Raman, and infrared spectroscopy collectively identified the imine/amine groups as the redox centers of the electroactive DPPH on GO. The use of different carbon-supports showed that only oxygen-functionalized GO and MWCNTs could provide major electroactivity for DPPH. This highlights the importance of a strong hydrogen-bonded network structure assisted by the concomitant π - π interactions between the organic moiety and oxygen function groups of carbon for the high electroactivity and stability of the GCE/GO@DPPH-NH/NH~(2)-modified electrode. The developed electrode exhibited remarkable performance towards the electrocatalytic oxidation of NADH at 0?V (Ag/AgCl). The amperometric i - t sensing of NADH showed high sensitivity (488?nA?μM_(?1)?cm_(?2)) and an extended linear range (50 to 450?μM) with complete freedom from several common biochemical/chemical interferents, such as ascorbic acid, hydrazine, glucose, cysteine, citric acid, nitrate, and uric acid.
DPPH;Graphene oxide;Free radical/functional group redox activity;Electrocatalytic oxidation;NADH;Amperometrici-tdetection;