Copper-decorated carbon nanotubes-based composite electrodes for nonenzymatic detection of glucose
© Pop et al.; licensee Springer. 2012
Received: 10 January 2012
Accepted: 22 May 2012
Published: 22 May 2012
The aim of this study was to prepare three types of multiwall carbon nanotubes (CNT)-based composite electrodes and to modify their surface by copper electrodeposition for nonenzymatic oxidation and determination of glucose from aqueous solution. Copper-decorated multiwall carbon nanotubes composite electrode (Cu/CNT-epoxy) exhibited the highest sensitivity to glucose determination.
KeywordsMultiwall carbon nanotubes composite electrodes Copper particles Glucose Electrochemical determination
Nowadays, a large community of researchers is focusing on the development of different applications for carbon nanotubes (CNT) in the field of electrochemical sensing. The high sensitivity, chemical stability, excellent electrical conductivity, and modifiable surface that provides the possibility to fabricate multifunctional electrochemical sensors are only a few important properties which recommend them for sensing applications [1, 2]. Using CNT in composites gives also the possibility to fabricate sensors with high electroanalytical performances with easy renewable surface and also a very good mechanical strength [1–3]. Nonenzymatic glucose determination in medical applications by electrocatalytic oxidation is of great interest to electrochemists [4–9]. Fabrication of high performance sensors for glucose continues to be a provocative challenge [7–10]. In this paper, three types of multiwall carbon nanotubes-based composite electrodes, i.e., CNT within an epoxy matrix (CNT-epoxy), CNT-synthetic A-type zeolite (SZ) within an epoxy matrix (SZCNT-epoxy), and CNT-natural clinoptilolite zeolite (NZ)-epoxy matrix (NZCNT-epoxy) were prepared, decorated with copper particles by electrodeposition, and then characterized and tested for direct electrochemical detection of glucose.
Multiwall CNT with an average diameter of 9.5 nm and average length of 1.5 μm were purchased from Nanocyl, Belgium (Belgium Nanocyl, Sambreville, Belgium). A synthetic A-type zeolite (SZ) was prepared using natural clinoptilolite as a silicon source and sodium aluminate as aluminum source, as we previously described . The composite electrodes were prepared by dispersion of CNT in tetrahydrofuran, 99.9% (THF, Sigma-Aldrich Laborchemikalien GmbH, Seelze, Germany) and epoxy resin (Araldite®LY5052, Huntsman Advanced Materials, Klybeckstrasse, Basle, Switzerland) by ultrasonication, followed by the homogenization of the resulting paste with the zeolite particles and the hardener using a two-roll mill. The mixture was then poured into polyvinyl chloride tubes and cured at 60°C for 24 h, obtaining disk electrodes with the surface area of 0.196 cm2. The ratios were chosen to reach 20% wt CNT, 20% wt SZ, and 20% wt NZ. The surface of prepared electrodes was then decorated with copper by electrodeposition at a potential of −0.5 V vs. Ag/AgCl for 20 s in the presence of 0.1 M CuSO4 solution. Scanning electron microscopy (SEM) was performed using an Inspect S PANalytical instrument (PANalytical Spectris Australia Pty Ltd., Sydney, New South Wales, Australia) coupled with the energy-dispersive X-ray analysis detector (EDX). Voltammetric and amperometric measurements were carried out using an Autolab PGSTAT101 (Metrohm Autolab, Utrecht, The Netherlands) controlled with NOVA 1.6 software (Metrohm Autolab, Utrecht, The Netherlands) and a three-electrode cell, with an Ag/AgCl reference electrode, a platinum counter electrode, and composite working electrodes.
Results and discussion
Direct electrochemical detection of glucose
The reproducibility of the Cu/CNT-epoxy electrode using the multiple-pulsed amperometry was evaluated for three replicate measurements of glucose detection and relative standard deviations (RSD) of 3.5% shows a good reproducibility. A recovery test was also performed by analyzing three parallel glucose serum samples. This test was run for 0.1 mM glucose in 0.1 M NaOH supporting electrolyte, and a recovery of 98% was found with an RSD of 3.8% using multiple-pulsed amperometry.
The electrocatalytic activities of the copper-decorated CNT-epoxy, SZCNT-epoxy and NZCNT-epoxy electrodes towards the oxidation of glucose in an alkaline solution were demonstrated. All copper-decorated composite electrodes exhibited useful properties for the direct oxidation and simple nonenzymatic determination of glucose on tested electrodes surface. The differences between the electroanalytical performances of the electrodes are related to composite structure and morphology, which influenced copper particle size and distribution on the surface of the composite material. The best electroanalytical performances obtained for the detection of glucose by cyclic voltammetry were recorded with the copper-decorated CNT-epoxy electrode, i.e., electrode sensitivity of 8.45 mA∙mM-1 and 0.2 μM glucose as limit of detection.
AP and CO are postdoctoral research associates. FM is an associate professor of Electrochemistry Applied for Environment Remediation and Monitoring. NV is a professor of Electrochemistry. JS is a professor of Advanced Materials. SM and EI are PhD students.
Carbon nanotubes-epoxy electrode
Carbon nanotubes-epoxy copper decorated electrode
Carbon nanotubes-natural zeolite-epoxy copper decorated electrode
Carbon nanotubes-synthetic zeolite-epoxy copper decorated electrode
Energy-dispersive X-ray spectroscopy
Carbon nanotubes-natural zeolite-epoxy electrode
Scanning electron microscopy
Synthetic A-type zeolite
Carbon nanotubes-synthetic zeolite-epoxy electrode.
This work was partially supported by the strategic grants POSDRU/89/1.5/S/57649, project ID 57649 (PERFORM-ERA), POSDRU/89/1.5/S/63700 and POSDRU/88/1.5/S/50783, project ID 50783, and cofinanced by the European Social Fund–Investing in People, within the Sectoral Operational Programme Human Resources Development 2007–2013, and partially by the PN-II-ID-PCE 165/2011 and PNII-RU-PD129/2010 grants.
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