Studies On Carbon Nanotubes Modified Glassy Carbon Electrode And Its Application

Carbon nanotubes (CNTs) are arrangements of carbon hexagons that are formed into tiny tubes, and both ends of each single tube are closed with caps formed by carbon rings. The extraordinary electronic property of CNTs enables them to facilitate the electron transfer when they act as electrode materials. Furthermore, the properties include excellent adsorption capability, great specific surface and various functional groups linked on CNTs have endued them with special electrocatalytic effect to the electrochemical behavior of some species. Thus, CNTs modified electrodes exhibit superior electrochemical properties to many other electrodes. And increasing attention is focused on how to control the modification of CNTs on the electrodes to improve the performance of CNTs modified electrodes and their application in various fields.In this thesis, we studied two kinds of dispersive systems include multiwall carbon nanotubes(MWNTs)-chitosan solution and MWNTs-Nafion solution. And we fabricated two kinds of MWNTs modified electrodes which have been successfully used to determine inorganic ions with high sensitivity. These two modified electrodes were characterized by using various methods, which give us new insight on the structure of modified layers and the electrode reactions. The main researches were summarized as follows:(1) Chitosan, a natural polymer without toxicity, was used as a dispersant to get the homogeneous MWNTs-chitosan solution. A uniform MWNTs-chiosan film was obtained on a glassy carbon electrode (GC) surface and then characterized by using scanning electron microscopy (SEM), infra-red (IR) spectra and electrochemical methods. The MWNTs-chiosan modified electrode possesses both the fascinating properties of MWNTs and the selectively adsorptive capability of chitosan. In pH 1.8 H2SO4 solution, the MWNTs-chitosan modified GC exhibits attractive ability for highly sensitive cathodic stripping voltammetric measurement of bromide. A wide linear calibration range (3.61×0^-7g mL^-71.4×10^-5g mL^-1) was achieved, with a detection limit of 9.6×10^-8g mL^-1. The kinetics parameters were measured by cyclic voltammetry (CV) and chronocoulometry. The mechanism of electrode reaction was also discussed.(2) The MWNTs-chiosan modified electrode exhibited an attractive ability to determine iodide. Operational parameters were optimized and the electrochemicalbehavior of iodide was studied by CV and anodic stripping voltammetry (ASV). A linear calibration range (5.0xl0"7 - 6.0xlO⁶mol L'1) was achieved, with a detection limit of 2.0 xlO"7 mol L"1.(3) In the presence of Nafion, an excellent cation-exchange polymer, MWNTs can be easily dispersed into ethanol. The MWNTs-Nafion modified GC was fabricated and the porous meshy structure of the modified layer was studied. The electrochemical behavior of iron(II) and iron(M) was studied by different electrochemical methods. The kinetics parameters were measured and the mechanism of electrode reaction was discussed. A linear calibration range (5.0xl0"10 - S.OxlO^mol I'1) was achieved, with a detection limit of 4.0xl0"10 mol 1^\ The method has been used to determine total iron in serum and red wine samples, and the results are satisfactory.