Arginine Preparation Of Functionalized Carbon Nanotubes And Their Dispersion And Solubility

Since their discovery in 1991, Carbon nanotubes ( CNTs ) have become the research focus in chemistry, physics, material science and biomedicine. CNTs have a lot of potential applications in the future Hi-Tech field due to their special mechanical, electronic, chemical properties and unique one-dimensional tube structures. However, comparing with other materials, the carbon nanotubes owns a large relatively inert surface. So they don't dissolve in common solvents and easy to reunite. This would be the obstacle in the research and application of carbon nanotubes. Moreover, it has been reported that CNTs' toxicity could be reduced by improving their solubility. Here arginines was used to modify carbon nanotubes to improve their solubilities and dispersion. The pH-response of dispersion also was studied in detail. The main contents of this study are shown as follows:(1)The pure MWNTs were put in arginine to get the graft-functionalization with ultrasonic assistance method for one hour. The Suspension of arginine-grafted multiple-walled carbon nanotubes were obtained as sample products through centrifugation. The chemical structure of arginine-grafted multiple-walled carbon nanotubes was characterized by Raman and UV spectroscopy. Results show that arginine has been noncovalently grafted to the MWCNTs.(2)The dispersion of arginine-grafted multiple-walled carbon nanotubes solution with different pH was characterized by all kinds instruments. The aggregation and dispersion of carbon nanotubes in solution was characterized by an atomic force microscope. The decreasing emission of fluorescence caused by the aggregation of carbon nanotubes was detected using a fluorophotometer. Results show that the dispersion of arginine-grafted multiple-walled carbon nanotubes in alkalic situation was better than in acidic and the higher the pH, the better the dispersion.(3) Covalent and noncovalent graft-functionalization of multi-walled carbon nanotubes (MWNTs) with arginine was prepared successfully by two steps. First,the original MWNTs were oxidized lightly in nitric acid so that the ends of MWNTs opening and sidewall intact;secondly, the oxidized MWNTs were put in arginine to get the covalent and noncovalent graft-functionalization with ultrasonic assistance method. The last sample solution was obtained through filtrating with nanoscale filter membrane.(4) The solubility dissolution of arginine-grafted multiple-walled carbon nanotubes was studied. Comparing the ultraviolet spectrophotometer (UV) absorption spectrum of pure arginine solution and sample solution and checking the solid sample with the mogravimetric analysis(TGA), the results show that the sample solution after filtration must exist carbon nanotubes and the acidized carbon nanotubes after functionalization with arginine can dissolve in water. The stability of carbon nanotubes' solubility in solution was put in research. The results show that the carbon nanotubes behave stable solubility through comparing the ultraviolet spectrophotometer (UV) absorption spectrum of sample in different time.