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

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 Ef=0.020V vs Ag/AgCl corresponding to ortho-quinone moiety of oxidized EA in pH7 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 (ks) 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 N2H4 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 (na′), total number of electrons (n′), reaction order with respect to N2H4, catalyst reaction rate constant (kchem) were evaluated. Finally, amperometric i-t and flow injection analysis for highly selective sensing of hydrazine without any interference from other biochemicals were validated.