Electrochemical immobilization of ellagic acid phytochemical on MWCNT modified glassy carbon electrode surface and its efficient hydrazine electrocatalytic activity in neutral pH

Abstract Ellagic acid (EA) is a lactone and polyphenolic functional groups-containing phyto-chemical that has been widely used as an anti-oxidant, anti-cancer and anti-aging cosmetic agent. EA is known as a stable redox active system only in organic medium, but irreversibly oxidized with coupled chemical reactions showing ill-defined redox peaks in aqueous solutions. Interestingly, we report here that electro-oxidation of EA tethered multiwalled carbon nanotube-modified glassy carbon electrode (GCE/MWCNT@EA) showed a well-defined pair of redox peaks with a surface-confined characteristics at E f  = 0.020 V vs Ag/AgCl corresponding to ortho -quinone moiety of oxidized EA in pH 7 phosphate buffer solution (PBS). No such behavior was noticed with EA adsorbed GCE. The GCE/MWCNT@EA was characterized by cyclic voltammetery (CV) and the transfer coefficient (α) and electrode to redox surface layer electron transfer rate constant ( k s ) were calculated. Physicochemical characterization of MWCNT@EA by FTIR, XRD and Raman Spectroscopy techniques revealed immobilized EA in its native form on MWCNT. Effect of various CNTs on EA electro-immobilization and the features that distinguish each other was highlighted. The GCE/MWCNT@EA showed excellent electrocatalytic activity toward N 2 H 4 oxidation. The mechanism and kinetics of the catalytic reaction was investigated by CV, and the kinetic parameters ca., number of electrons in the rate determining step ( n a ′), total number of electrons ( n ′), reaction order with respect to N 2 H 4 , catalyst reaction rate constant ( k chem ) were evaluated. Finally, amperometric i-t and flow injection analysis for highly selective sensing of hydrazine without any interference from other biochemicals were validated.