Spontaneous formation of an electroactive co-polymeric film derived from nordihydroguaiaretic acid and 4,4′-diaminobibenzyl

Binary solution of nordihydroguaiaretic acid (NDGA) and 4,4′-diaminobibenzyl (DABB) undergoes rapid oxidation by ambient oxygen to form a thin film of poly-NDGA-co-DABB on the surface of the reaction chamber and on immersed substrates. Electrochemistry of thus formed films was studied in 0.1 M sulfuric acid and in phosphate buffer (pH 7.4). Electrochemical behavior of the co-polymeric film is characterized by two redox couples, the predominant one being observed at more negative potentials comparing to parent NDGA i.e. 0.28 vs. 0.49 V (vs. Ag/AgCl) in 0.5 M H2SO4. The peak potentials were shifted toward lower values with solution pH at the rate of 59 mV/pH unit indicating a 2e/2H+ transition as expected for quinone-containing films. The poly-NDGA-co-DABB film exhibits catalytic activity toward electroreduction of nitrite to nitric oxide in acidic electrolytes. This reaction can be used to quantify nitrite in a broad concentration range with low detection limit (0.3 μM, S/N = 3).