Nanomolar detection of hydrogen peroxide on glassy carbon electrode modified with electrodeposited cobalt oxide nanoparticles.

The electrochemical detection of H2O2 was investigated on a cobalt oxide nanoparticles modified glassy carbon electrode in phosphate buffer solution (pH 7). Cyclic voltammetry at potential range -1.1 to 1.1 V from CoCl2 natural aqueous solution produced well defined cobalt oxide nanoparticles deposited on the surface of glassy carbon electrode. The surface of resulting electrode was characterized with SEM. The formation of cobalt oxyhydroxide film was investigated by cyclic voltammetry in alkaline and natural aqueous solution. The modified electrode showed well defined and stable redox couples in both alkaline and natural aqueous solution. The modified electrode showed excellent electrocatalytic activity for oxidation of hydrogen peroxide. The response to H2O2 on the modified electrode was examined using cyclic voltammetry and amperometry. The amperometric detection of hydrogen peroxide is carried out at 0.75 V versus Ag/AgCl reference electrode in phosphate buffer solution with pH 7.4. The detection limit (S/N=3) was 0.4 nM with linearity up to 6 orders of magnitude and sensitivity of 4.86 microA microM(-1) cm(-2). The response time of the electrode to achieve 95% of the steady-state current is <2 s. No measurable reduction in analytical performance of the modified electrode was found by storing the electrode in ambient conditions for 20 days. This modified electrode recedes many advantages such as remarkable catalytic activity, good reproducibility, simple preparation procedure and long term stability of signal response during hydrogen peroxide oxidation. The immobilization of cobalt oxide nanoparticles on the surface of GC electrode appears to be a highly efficient method for the development of a new class of sensitive, stable and reproducible hydrogen peroxide electrochemical sensor.