Low Potential Stable Glucose Detection at Carbon Nanotube Modified Gold Electrodes
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Low Potential Stable Glucose Detection at Carbon Nanotube Modified Gold Electrodes S. G. Wang, Qing Zhang, Ruili Wang 1, D. J. Yang, S. F. Yoon, R. Zhang Microelectronics Centre, School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798. 1 Department of Community Occupational & Family Medicine, Faculty of Medicine, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260. ABSTRACT The subtle electronic properties and large electroactive surface of carbon nanotubes (CNTs) suggest that they have the ability to promote electron-transfer and favor electrocatalytic behavior in electrochemical reactions when they are employed as an electrode. In this paper, CNT-modified gold electrodes for glucose biosensor have been fabricated using multi-walled carbon nanotubes. The CNT-based electrode exhibits a strong and stable amperometric response toward glucose even at a low potential of +0.35 V versus Ag/AgCl in comparison with the glassy carbon-based electrode.
INTRODUCTION Carbon materials including glassy carbon (GC) [1], carbon paste [2], graphite [3], diamond-like carbon [4] and diamond [5] are widely used for biosensor construction. Carbon material-based biosensor has many advantages such as high thermal stability, excellent chemical stability, and biocompatibility with human tissue and organisms. Carbon nanotubes (CNTs), which were initially discovered by Iijima [6], are a new member of carbon material family. CNTs can be considered as the result of folding graphitic layers into carbon cylinders and may be composed of a single shellsingle-walled carbon nanotubes (SWNTs) [7], or of several shellsmulti-walled carbon nanotubes (MWNTs) [6]. The subtle electronic properties and large electroactive surface of CNTs suggest that they have the ability to promote electron-transfer and favor electrocatalytic behavior in electrochemical reactions when they are employed as an electrode. CNT-based electrodes have been demonstrated to be superior to other carbon materials for the oxidation of biomolecules including dopamine [8], protein [9] and β-nicotinamide adenine dinucleotide (NADH) [10]. CNT-based electrodes have recently been reported to be used for the construction of biosensors [11-15]. In this paper, a CNT-based electrode for glucose biosensor has been described. The CNT-based biosensor exhibits a strong and stable glucose response even at a low potential of +0.35 V versus Ag/AgCl in comparison with GC-based biosensor.
EXPERIMENTAL DETAILS Chemicals Glucose oxidase (GOD, EC 1.1.3.4, type VII solid from Aspergillus niger) was purchased from Sigma. All other reagents were of analytical grade and were used without any further purification.
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A buffer (pH 7.4) comprising Na2HPO4 and NaH2PO4 was prepared in distilled water. This buffer was used for all bioelectrochemical measurements. CNT preparation CNTs were grown on n-type silicon substrates using an ASTeX microwave plasma system. During the CNT growth, the deposition pressure, substr
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