Electrochemical catalysis and stability of tetraamido macrocyclic ligands iron immobilized on modified pyrolytic graphite electrode

A synthetic molecule tetraamido macrocyclic ligands iron complex (FeIII-TAML), a catalyst that speeds up peroxide oxidation reaction, was immobilized on pyrolytic graphite (PG) electrode modified with sodium alginate (SA) gel films. The tetraamido macrocyclic ligands iron complex in the sodium alginate thin films was characterized by cyclic voltammetry (CV), ultraviolet–visible spectrophotometry (UV–vis) and scanning electron microscopy (SEM). The characterization results showed that the tetraamido macrocyclic ligands iron complex on pyrolytic graphite electrode retained its native structure and displayed a pair of well-defined and nearly reversible peaks at about −0.051 V and 0.051 V (V vs saturated calomel electrode, SCE) in a 0.1 M phosphate buffer solution of pH 7.0, originated from the tetraamido macrocyclic ligands iron complex redox couples. The iron complex in the sodium alginate films also exhibited a good electrocatalytic property toward the decomposition of hydrogen peroxide with a significant lowering of overpotential, indicating the electrode can be potential hydrogen peroxide sensors. The amperometric response of the sensor which showed good stability and reliability varied linearly with the hydrogen peroxide concentrations ranging from 2.2 mM to 24 mM, with a detection limit of 0.88 mM at a signal-to-noise ratio of 3.