Journal of Electroanalytical Chemistry, Vol.812, 10-21, 2018
In-situ electrochemical immobilization of [Mn(bpy)(2)(H2O)(2)](2+) complex on MWCNT modified electrode and its electrocatalytic H2O2 oxidation and reduction reactions: A Mn-Pseudocatalase enzyme bio-mimicking electron-transfer functional model
Mn-Pseudocatalase is a non-heme catalases family enzyme produced by various bacteria that involves in a two electron H2O2 catalytic cycle in a manner similar to that of the heme-based Catalase enzymes. Herein, we report a bio-mimicking functional model system prepared by in-situ electrochemical oxidation of Mn(bpy)(2)Cl-2 precursor to a surface-confined [Mn-II(bpy)(2)(H2O)(2)](2+) complex, wherein, bpy = 2,2'-bipyridyl, on a carboxylic acid functionalized multiwalled-carbon nanotube (f-MWCNT)/Nafion modified glassy carbon electrode for biomimicking H2O2 disproportionation reaction. The modified electrode showed a well-defined redox peaks at an apparent standard electrode potentials (E degrees'), 0.65 +/- 0.05 V and 0.2 V vs Ag/AgCI with surface-excess (Gamma(Mn)) values, 6.24 x 10(-9) mol cm(-2) and 0.43 x 10(-9) mol cm(-2) for the Mn-IV/III and Mn-III/II sites of the Mn-complex in neutral pH solution respectively. Physico-chemical characterizations of the system by FTIR, UV-Vis and ESI-MS (ethanolic extract of the electrode) confirming the conversion of [Mn(bpy)(2)(H2O)(2)](2+) complex (m/z, 403.09). A strong pi-pi interaction between the f-MWCNT's graphitic sp(2) carbons and the bpy's aromatic electrons, hydrogen bonding between the oxygen and water molecules and ionic interaction between the complex and sulphonic site of nafion favor the stability of the complex. The hybrid system showed selective current signals for mediated oxidation and reduction reactions of H2O2 (disproportional reaction) without any dissolved oxygen interference. As an independent study, selective electro-catalytic oxidation and amperometric detection of H2O2 was demonstrated.