1. Electrochemical sensor based on nanoparticles of cobalt oxides for determination of glucose
NiO2 mediator in catalytic oxidation of 2-propanol on glassy carbon
electrode modified with nickel oxides
Abdelkader BENCHETTARA(1, 2)*, Abdelhakim BENCHETTARA (1)
(1) Laboratoire d’Electrochimie-Corrosion, Métallurgie et Chimie Minérale-Fac. Chimie-USTHB-BP 32 El-Alia Bab Ezzouar 16 111 Alger (Algérie)
(2) Ecole Nationale Préparatoire aux Etudes d’Ingéniorat (ENPEI), BP 05 Rouiba-Alger
Abstract
The electrochemical reactions are reactions of electron exchange at the interface of an electron conductor and an ionic liquid or solid conductor. It is thus not necessary to use bulk electrodes for electrochemical reactions. Hence the importance of developing electrodes by depositing nanoparticles on glassy carbon (GC) or other substrates. This electrode design has the advantage of controlling the dimensions of electrochemical sensors and reduces their cost. In this context, we present the results of the modification of glassy carbon with cobalt oxides [1-3]. The procedure of filing is done in two steps. During the first step, a thin film of Co is deposited by potentiostatic polarization of GC/ 10-2 mol.L -1 cobalt chloride interface, in boric acid, pH 5.5. In a second step, the cobalt film is anodically oxidized in sodium hydroxide solution, pH 12. Well choosing reduction potential of Co2+ ions and oxidation potential of cobalt film is extremely important to obtain a stable deposit with a good faradic efficiency. These thin oxide films are used to develop an electrochemical sensor for glucose determination.
2. RESULTS
INTRODUCTION
To our knowledge, the use of sensors dates back to 1952 and was interested in phonocardiography. Since, the development of electrochemical detection systems for small organic molecules gained considerable attention. In analytical science, electrochemical detection systems represent a simple and less expensive way than traditional methods. Numerous attempts have been undertaken to develop methods of detection. Many studies focused on the use of electrocatalysts based on iron hydroxides, cobalt oxides, nickel oxides , copper oxides, zinc oxides and ruthenium oxides. The presence of the oxidized form in the sensors provides an intense electrocatalytic performance and makes them able to oxidize various organic molecules.
1. Elaboration of cobalt film followed by its reoxidation
Fig.4 Voltamperograms recorded during glucose oxidation in 0.1 mol L-1 NaOH; 0.1 V s-1; 25 °C. Inset: Calibration straight line of glucose on GC activated with cobalt oxides, in 0.1 mol L-1 NaOH; 25°C; 0.1Vs-1.
Glucose oxidation mechanism
Glucose + 3Co2O Oxidation product + 2Co3O4
2Co3O4 + H2O Co2O3 +2H+ +2e
Fig.1: Chronoamperogram of the cathodic reduction of 10-2 mol L-1 Co2+on GC electrode in 0.1 mol L-1 H3BO3 at -1V/SCE; 50mVs-1; 25°C.
glucose
3Co2O3 +
In acidic medium: Co2+ + 2e Co
In alkaline medium:
Co + H2O CoO + 2H+ + 2e
3CoO + H2O Co3O4 + 2H+ + 2e
2Co3O4 + H2O Co2O3 + 2H+ + 2e GC
electrode €
Electrode
modification
Electrooxidation
of metallic film 2e
Oxidation
Co2+
Oxidation product
2Co3O4 +
Drawing 1 summarizes the steps of modification of the GC electrode, and the catalytic effect of Co2O3
Co2O3
Fig.2: Voltammograms recorded during oxidation of Co film in 0.1 mol L-1 NaOH; 100mVs-1; 25°C.
CoO
Co3O4
CONCLUSION
In conclusion, a non-enzymatic sensor was manufactured successfully using Co2O3 as sensing materials. This modified electrode is used to the glucose determination in the concentration range from 133 µM to 1.99 mM, with a sensitivity of 4.6 L mol-1 .
Fig.3: Nyquist plots of bare GC (1) and CoOx/GC (2) recorded at OCP by superimposing a sinusoidal potential of 10mV peak to peak, in the frequency range [10+5Hz-10-3Hz] ;25°C; 1000rpm. 2
REFERENCES
[1] Y. Song, Z. He, H. Zhu, H. Hou, L. Wang, Electrochim Acta, 58(2011) 757–763
[2] Mahshid, S.S., Mahshid, S., Dolati, A., Ghorbani, M., Yang, L., Luo, S., Cai, Q.,
Electrochim acta. 58(2011)
[3] Pasta, M., La Mantia, F., Cui, Y., Electrochim acta. 55(2010) 1

2. Graphite electrode Electrode modification Electrooxidation
glucose
Graphite electrode €
Electrode modification
Electrooxidation
of metalic film