Research On The Preparation And Application For Electrochemical Sensor Based On The Functionalized Multi-walled Carbon Nanotubes

The electrochemical sensor has such feartures as high selectivity, fast speeding analysis, simple operation, low cost, and etc, and has been widely used in the fields of environmental monitoring, clinical diagnosis, food industry, and other fields. This dissertation mainly concentrated on the functionalized multi-walled carbon nanotubes (MWCNTs), developed the new electrochemical sensors based on the functionalized carbon nanotubes (CNTs) for successfully detection of dopamine (DA), ascorbic acid (AA) and uric acid (UA), in order to improve the sensitivity and selectivity of their detection.The main results are as follows:First of all, the glassy carbon electrode (GCE) modified by multi-walled carbon nanotubes which is functionalized by the hydroxy group was successfully prepared. The electrochemical oxidation of AA, DA and UA was simultaneously investigated in phosphate buffer solutions by using OH-MWCNT/GC electrode with well catalytic activity. At the same time, in comparison with bare glassy carbon electrode, the results demonstrate that its electrode response sensitivity is greatly improved, and the peak current of AA, DA and UA increases 12.8,17.6, and 42.6 times respectively. The voltammetric peaks well-separated towards the oxidation of AA, DA and UA is solved, and the peak current raises 10,2.2, and 5.3 times compared with no functionalized of multi-walled carbon nanotube electrode. The method has successfully been applied for the determination of the UA in the urine.Followed by researching the glassy carbon electrode modified by the composite film of copper nanoparticle-multi walled carbon nanotube. In order to obtain the composite film, the electrochemical sensors were prepared by electrochemical deposition method. A detailed investigation by transmission electron microscopy (TEM) was carried out in order to elucidate the preparation process and properties of the nanocomposites. TEM image shows that the copper nanoparticles distributed on inner and outer walls of MWCNTs. The results demonstrate its excellent electro-catalytic activity towards the oxidation of DA by using the glassy carbon electrode modified by the Nano-Cu-MWCNT film. Under the same conditions, the oxidation peak current of DA response signal is about 2 times of the current response signal without nanometer copper-modified glassy carbon electrode. The interference of the 10 times concentration of AA and 1 times concentration of UA in the determination of DA is totally ruled out. The method has successfully been applied for the determination of the DA indopamine hydrochloride injection and UA in the urine.Thirdly, the physical mixing method was used for molybdophosphoric acid adsorbing on the MWCNT, and modifying glassy carbon electrode, and then the PMo12-COOH-MWCNT modified glassy carbon electrode was prepared. A detailed investigation by XPS and CV was carried out in order to elucidate the preparation process and properties of the nanocomposites. It shows that PMo12 can adsorption onto the COOH-MWCNTs. Color test and UV-Vis absorption spectrum test also were performed. And it indicates that PMo12 and DA is a strong interaction. The determination of DA was accomplished through PMo12-COOH-MWCNT/GC electrode, in contrast to the COOH-MWCNT/GC electrode, the anodic peak current of DA on PMo12-COOH-MWCNT/GC electrode is nearly 6 times. At the same time, 20 times the concentration of AA and 5 times the concentration of UA do not affect the detection of DA. This method can be used to detect the content of DA in dopamine hydrochloride injection.Finally, the electrochemical sensors was prepared by using the NaBH4 reduction method to deposit Cu nanoparticles on the multi-walled carbon nanotubes, and then to adsorb phosphomolybdic acid on multi-walled carbon nanotubes. In the examination of dopamine using nano-Cu-PMo12-MWCNT/GC electrode, it is found that the sensor response to DA is superior to the single nano-copper-MWCNT/GC electrode or PMo12-MWCNT/GC electrode. It reveals that Cu and phosphomolybdic acid has a synergistic effect catalysis for DA. At the same time, it reveals that 10 times the concentration of AA and 2 times the concentration of UA do not affect the detection of DA, DPV method is performed to detect of DA and it has a sensitivity of 56.83 μA.μM-1. This method also can be used to detect the content of DA in dopamine hydrochloride injection.