Non-enzymatic hydrogen peroxide sensor based on MnO₂-ordered mesoporous carbon composite modified electrode

Abstract

A novel non-enzymatic hydrogen peroxide (H₂O₂) sensor based on the MnO₂-ordered mesoporous carbon (OMC) nanocomposite modified glassy carbon electrode (MnO₂/OMC/GCE) was developed. OMC was synthesized and dropped onto the surface of glassy carbon electrode, and MnO₂ nanoparticles were then electrodeposited on the surface of OMC to fabricate the MnO₂/OMC/GCE. The electrochemical behaviors of H₂O₂ at the modified electrode were investigated by cyclic voltammetry and amperometry. The results showed that the MnO₂/OMC/GCE exhibited excellent electrocatalytic activity toward H₂O₂. Optimization of measurement parameters such as the amount of MnO₂, applied potential and pH value were studied in detail. Under the optimum conditions, the calibration curve for H₂O₂ determination was linear in the range from 5 × 10⁻⁷ to 6 × 10⁻⁴ M with a detection limit of 7.0 × 10⁻⁸ M (S/N = 3), and the sensitivity of the sensor was calculated to be 806.8 μA mM⁻¹ cm⁻².

Introduction

Hydrogen peroxide (H₂O₂) is a common oxidizing agent or an essential intermediate in biochemical, pharmaceutical, clinical, industrial and environmental fields. Therefore, its analytical determination becomes of great significance [1]. Many traditional techniques, including chemiluminescence [2], titrimetry [3], spectrophotometry [4], fluorescence [5] and electrochemical method [6], [7], [8] have been employed to detect H₂O₂. Among these methods, electroanalytical method is attractive because of its low cost, operational simplicity and the possibility for real-time detection [9]. Owing to the high sensitivity and selectivity, electrochemical biosensors based on the electrocatalysis of immobilized enzymes toward H₂O₂ are used widely [10], [11]. However, due to inevitable drawbacks of the enzymatic sensors such as the complex fabrication procedure, limited lifetime, and stability problem, much recent effort has been devoted to the direct determination of H₂O₂ at non-enzymatic electrodes [12], [13]. Nowadays, metal and transition metal oxide nanoparticles have been applied extensively in fabricating high efficient non-enzymatic electrochemical sensors [9], [14], [15]. In particular, manganese dioxide nanoparticle (nano-MnO₂) is one of the most appealing inorganic materials [16], [17], and has drawn attention in bioanalytical chemistry, especially in electrochemical sensing of H₂O₂, due to its excellent catalytic activity which can promote H₂O₂ decomposition [18], [19], [20].

Because of the unique properties, such as ordered pore channels, high specific surface areas, narrow pore size distributions, and good electrical conductivity [21], [22], ordered mesoporous carbon (OMC) has been broadly studied as electrode modified material [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34]. For example, Chen et al. have fabricated an amperometric biosensor based on hemoglobin adsorbed on OMC modified electrode, which displayed excellent electrocatalysis to the reduction of both H₂O₂ and O₂ [30]. Guo et al. have constructed an electrochemical sensing platform based on the OMC-fullerene (C₆₀) system, which was possessed of electrocatalytic activity toward many important biomolecules (l-cysteine, glutathione, dopamine, ascorbic acid, uric acid, epinephrine and β-nicotinamide adenine dinucleotide) [31]. Zheng et al. have realized simultaneous determination of dopamine, ascorbic acid and uric acid with OMC/Nafion composite film modified electrode [32]. Zhu et al. have reported the electrochemical detection of double-stranded DNA by OMC modified carbon ionic liquid electrode [33]. Jiang et al. have prepared a glucose biosensor based on glucose oxidase fixed on the platinum nanoparticles-OMC nanocomposite [34]. The improved electrocatalytic activity of OMC makes it a promising alternative candidate for electrode modified materials.

In this work, we have tried to combine the advantages of both MnO₂ and OMC to realize the electrochemical detection of H₂O₂. For this purpose, MnO₂ nanoparticles were electrodeposited on the surface of OMC modified glassy carbon electrode (GCE) to develop a non-enzymatic H₂O₂ sensor (MnO₂/OMC/GCE). Compared with MnO₂/GCE and OMC/GCE, the proposed sensor exhibited excellent electrocatalytic ability toward the oxidation of H₂O₂, and the stability and sensitivity of the non-enzymatic sensor were also favorable.