Dual Electrocatalytic Behavior of Oxovanadium(IV) Salen Immobilized Carbon Materials Towards Cysteine Oxidation and Cystine Reduction: Graphene Versus Single Walled Carbon Nanotubes

Abstract

AbstractOxovanadium(IV) salen (VO(salen)) (where salen=N,N’‐bis(salicylidene)ethylenediamine) is embedded onto reduced graphene oxide (rGO) and single walled carbon nanotubes (SWCNTs). The resulting materials, VO(salen) embedded rGO (rGO‐VO(salen)) and VO(salen) embedded SWCNTs (SWCNTs‐VO(salen)) show remarkable electrocatalytic activity for cysteine oxidation and cystine (the oxidized product of cysteine) reduction as demonstrated by cyclic voltammetry (CV). The materials, rGO‐VO(salen) and SWCNTs‐VO(salen) are characterized through spectroscopic and microscopic techniques. Transmission electron microscopy exhibits nanocrystalline view of VO(salen) on rGO‐VO(salen) while it appears like aggregated nodules in the SWCNTs‐VO(salen) revealing the nano‐structures excellently. Electrochemical cysteine oxidation is studied using rGO‐VO(salen) coated glassy carbon (GC) electrode (GC/rGO‐VO(salen)) and SWCNTs‐VO(salen) coated GC electrode (GC/SWCNTs‐VO(salen)). The efficiency of the catalytic platforms is compared. Overall number of electrons and electron transfer rate constant are obtained using rotating disc electrode for cysteine oxidation at GC/rGO‐VO(salen) and GC/SWCNTs‐VO(salen). Calibration curves for the determination of cysteine at GC/rGO‐VO(salen) and GC/SWCNTs‐VO(salen) exhibit linear range from 1.0 μM to 5.0 mM and 1.0 μM to 4.0 mM, respectively. GC/rGO‐VO(salen) and GC/SWCNTs‐VO(salen) are successfully applied for the real samples analysis with remarkable recovery.