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Studies of Electrochemical Sensors Based on MWCNTs/CHIT-Fc Composites

Author: ZhouHong
Tutor: SunChangQing
School: Jilin University
Course: Analytical Chemistry
Keywords: Multi - walled carbon nanotubes Ferrocene Functional Biosensors Composition Ascorbic acid Membrane electrode Chitosan Scanning electron microscope Multilayers
CLC: TB383.1
Type: Master's thesis
Year: 2009
Downloads: 158
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Abstract


A novel amperometric sensor for the determination of sulfite was fabricated based on multiwalled carbon nanotubes/ferrocene-branched chitosan composites-covered glassy carbon electrode. The electrochemical behavior of the sensor was investigated in detail by cyclic voltammetry. The apparent surface electron transfer rate constant and charge transfer coefficient of the CHIT-Fc/MWCNTs/GCE were also determined by cyclic voltammetry, which were about 1.93 cm s-1 and 0.42, respectively. The sensor displayed good electrocatalytic activity towards the oxidation of sulfite. The peak potential for the oxidation of sulfite was lowered by at least 330 mV compared with that obtained at CHIT/MWCNTs/GCE. In optimal conditions, linear range spans the concentration of sulfite from 5μΜto 1.5 mM and the detection limit was 2.8μΜat a signal-to-noise ratio of 3. The proposed method was used for the determination of sulfite in boiler water. In addition, the sensor has good stability and reproducibility.By using the electrostatic self-assembly technique, the multilayer films containing CHIT-Fc@MWCNTs and PSS were alternately fabricated on GCE modified with PDDA. The obtained thin films were characterized by CV, UV-vis and SEM. The electrocatalytic oxidation of AA on the multilayer film electrode was studied in detail by CV. When the number of bilayers of CHIT-Fc@MWCNTs on the GCE is 6, the oxidation peak potential of AA was lowered by at least 0.4 V compared with that obtained at bare GCE. The current response of AA at different bilayers of CHIT-Fc@MWCNTs on the modified electrode was studied by amperometric method. The analytical performance of the modified electrode such as sensitivity, detection limit and linear range for AA determination can be turned to the desired level by adjusting the number of deposited CHIT-Fc@MWCNTs bilayers.Ferrocene-branched chitosan as a redox polymer has been covalently grafted onto the surface of multiwalled carbon nanotubes by the carboxyl-amine coupling between the MWCNTs containing carboxyl groups and CHIT-Fc containing amino groups. Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy were used to characterize the covalent interaction between MWCNTs and CHIT-Fc, respectively. From transmission electron microscopy images a core-shell structure with MWCNTs in the center and a CHIT-Fc layer lying around them were observed. The CHIT-Fc grafted MWCNT composites (MWCNTs@CHIT-Fc) have excellent solubility in diluted acetic acid solution. Electrochemical behaviour and electrocatalytic oxidation towards glucose of the chemically modified electrodes based on the MWCNTs@CHIT-Fc composites were studied by cyclic voltammetry.

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