Fe3O4/ZrO2 NANOCOMPOSITE MODIFIED CARBON PASTE ELECTRODE; PREPARATION, CHARACTERIZATION AND APPLICATION FOR THE DETECTION OF ASCORBIC ACID

Abstract

Fe3O4, ZrO2 and Fe3O4/ZrO2 nanocomposites were synthesized by chemical co-precipitation method. The structural and morphological properties of the as-synthesized materials were characterized by FTIR, UV-Vis, XRD and SEM. Results obtained for the nanomaterials confirmed the formation of Fe3O4, ZrO2 and Fe3O4/ZrO2 nanocomposite. XRD diffraction patterns depicted Fe3O4, ZrO2 and Fe3O4/ZrO2 crystalline structure and the smaller size of the nanocomposite (9.8 nm) in comparison to the magnetite (52.11 nm) and zirconium oxide (51.5 nm). Electrochemical properties of carbon paste electrode modified by Fe3O4, ZrO2 and Fe3O4/ZrO2 nanocomposite were studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in the presence of 2 mM K3Fe(CN)6 and aqueous 0.1 M KCl. The acquired voltammograms demonstrates that Fe3O4/ZrO2 nanocomposite showed the highest electrochemical signal compared to the bare CPE and the other modified electrodes. This could be due to the synergistic effect as a result of the high absorption capacity of Fe3O4 and electrocatalytic properties of ZrO2. The EIS spectra result was also consistent to that of the CV; CPE modified by the binary system showed a small semicircle (low charge transfer resistance 976 Ω) to that of magnetite 2168 and zirconium oxide 2420 Ω. These behaviors can improve the sensitivity and the response of Fe3O4/ZrO2/CPE proposed sensor for the detection of ascorbic acid (AA). To improve the performance of the sensor pH and scan rate were optimized. Under optimized condition (pH = 4 and υ = 100 mV s -1 ) Fe3O4/ZrO2/CPE electrode was applied to determine the concentration of AA in standard solution (1 to 6 x 10-6 M) using differential pulse voltammetry. The sensor exhibits good linear range (1 - 6 µM), sensitivity (11 µA/µM) and detection limit (0.51 µM), reproducibility (2.4 %) and stability (96.91 %). The electrode was also applied to determine AA in paracetamol. The finding demonstrated the developed sensor can be a potential candidate for routine analysis of AA in pharmaceuticals, food and fruit samples.