Carbon electrodes modified by nanoscopic iron(III) oxides to assemble chemical sensors for the hydrogen peroxide amperometric detection

In this study we show that nanoparticles of various ferric oxides (hematite, maghemitc, amorphous Fe2O3, beta-Fe2O3 and ferrihydrite) incorporated into carbon paste exhibit electro-catalytic properties towards hydrogen peroxide reduction. The modified paste electrode performances were evaluated and compared with those obtained with Prussian Blue-modified carbon paste electrode, which represents an excellent chemical mediator towards the H2O redox reaction (as widely described in literature). The best catalytic activity was found for carbon paste modified by amorphous ferric oxide with 2 - 4 nm particle size, which was further tested for possible application as hydrogen peroxide sensor. At pH 7, the limit of detection was 2 x 10(-5) M H2O2 (S/N = 3), the calibration curves were linear upto 8.5 mM H2O2 (R-2= 0.998), the measurement reproducibility (RSD = 97%, n = 4), the interelectrode reproducibility (RSD = 16%, n(electrodes) = 5) and < 3 s response time.