Preparation Of Carbon Nanotubes And Their Composite Nanomaterials And Its Application In Electrochemical Analysis

Metal nanoparticles, not only have the basic characteristics of nanomaterials, but also have the unique physical and chemical properties, catalytic activity and electromagnetism characteristics. It is widely used in many fields, such as optics, electromagnetism, catalyst and bio-pharmaceutical, etc. And the synergy of bimetallic nanoparticles make them have more extensive applied values. Chitosan has good biological functions and compatibilities, blood compatibility, film-forming property, security, microbial degradation and other excellent properties. MWNTs can be viewed as composed of multilayer nested SWNT, it can make carbon nanotubes have different functions by changed the structure of carbon nanotubes, such as carboxyl carbon nanotubes. In this paper, we made different sensors based on the excellent characteristics of the above materials, and used electrochemical methods to determined the melamine, Cu (Ⅱ) and ascorbic acid (AA).I. The Preparation of Glycine/MWNTs Modified Glass Carbon Electrode and The Electrochemical Determination of MelamineThrough the relevant experiments, in this chapter, we prepared a simple electrochemical sensor. Firstly, we modifide the glassy carbon electrode with multi-walled carbon nanotubes, then, made glycine modified on the electrodes, After a period of time, we could get the final modified electrodes. As a working electrode for the determination of melamine, it has got better experimental results. The electrochemical behavior of electrode and optimization conditions were studied by the methods of cyclic voltammetry, AC impedance and so on. Based on the optimization conditions, we used square wave voltammetry (SWV) technology to studied the melamine detection limit. Through the determination of melamine it showed a good linear in the concentration ranging from 0.20 μM to 20 μM, the linear correlation coefficient R=0.9972, and the detection limit is 2.0×10-8 M (S/N=3). Eventually, we found that the method for determination of melamine can get a pair of redox peaks with good symmetry, and it could be explained that there was a redox reaction during the process of determination, and then we got the better detected result.Ⅱ. AuPdNPs/MWNTs-CS Modified Glass Carbon Electrode and The Determined Research of (Cu (Ⅱ))In this paper we talked about the determination of Cu (Ⅱ), on the basis of the good dispersion performance, film forming performance and good adsorption properties for metal ions of chitosan, first of all, we made the composite of carbon nanotubes and chitosan.The composite material has good dispersion, we used it modified the glassy carbon electrode, not only had the excellent characteristics of carbon nanotubes, but also had the corresponding performance with chitosan. After the electrical aggregation of AuPdNPs, due to the synergy between AuPdNPs, the electrical catalytic property of the modified electrode was improved greatly. Moreover, based on the properties of chitosan, the Cu (Ⅱ) in the solution can be fixed on the modified electrodes very well when determined. Finally, we got better electrochemical signals during the process of determination. We used the SWASV to detect the detection limit of Cu (Ⅱ). Through the determination of Cu (Ⅱ), it showed a good linear in the concentration ranging from 0.40 nM to 40 nM, and the linear correlation coefficient R=0.9955, detection limit is 8.0×10-11 M (S/N=3). So, we can get that the electrode preparation process is simple, the determination method has high sensitivity, and it tests more successful in the actual samples.Ⅲ. PTA/MWNTs -CS Modified Glass Carbon Electrode and The Determined Research of Ascorbic AcidIn this chapter we used the composite of carbon nanotubes and chitosan modified glassy carbon electrode, on the basis of electrical aggregation tartaric acid to determined ascorbic acid. Because of the composite of carbon nanotubes and chitosan have corresponding carboxyl and amino, besides, tartaric acid also contains hydroxyl and carboxyl, during electrical aggregation, the aggregation of tartaric acid has a large number of hydroxyl groups and carboxyl groups, then, there had esterification reactions between the corresponding carboxyl and amino of the composite and corresponding carboxyl and hydroxyl of tartaric acid, which made tartaric acid modified on the electrode by chemical reactions. And through the study we found that when AA soluble in buffer solution, it will lose protons and negatively charged. However, the polymerized tartaric acid contains a lot of positive charges, then there were interactions occured between AA and polymerized tartaric acid, which led to AA oxidized and the increase of the oxidation peak current, and this experiment achieved the goal of the determination. It showed a good linear in the concentration ranging from 20.0 μM to 1.25 mM, the linear correlation coefficient R= 0.9961, the detection limit is 5.0 μM (S/N=3). In this experiment, tartaric acid itself can have interference to the experimental determination in certain extend, so we adopt the cyclic voltammetry (CV) to determined the detection linear.