A platinum electrode coated with a copper (II) aminopropyl complex-cellulose acetate membrane and its use for dissolved oxygen reduction

Highly dispersed Al2O3 in a cellulose acetate membrane, resulting in an organic–inorganic hybrid material, Cel/Al2O3, was prepared. It was further modified by attaching an organofunctional group by reacting with the precursor reagent (EtO)3Si(CH2)3NH(CH2)2NH2. The resulting organofunctionalized material was reacted with CuCl2 in ethanolic solution forming a distorted tetragonal coordinated complex Cel/Al2O3/(SiL)2CuCl2 [L=−(CH2)3NH(CH2)2NH2], as shown by the UV-Vis absorption spectrum. The quantities of attached organofunctional groups and of adsorbed metal were 0.41 and 0.12 mmol per gram of the material, respectively. Cyclic voltammetric (CV) experiments, carried out on a thin membrane of the material fixed on a platinum disk, showed two cathodic current peaks, one at 0.10 and another at −0.35 V, versus SCE, both due to the Cu(II)→Cu(I) reduction process. The differences in the equilibrium coordination geometry around the metal complexes of Cu(II) and Cu(I) are responsible for the doubled peaks. In a dissolved oxygen solution, an enhancement of the cathodic peak currents was observed due to a catalytic oxygen reduction. The electrode response towards dissolved oxygen concentrations showed a linear correlation between concentrations of 1.9 and 12.1 mg l−1, indicating the potential use of the material to make an oxygen sensor.