Functionalization Of Carbon Nanotubes And Their Preliminary Applications As Supporting Materials

Carbon nanotubes (CNTs) are a kind of typical nanomaterials and have attracted considerable attentions in a wide variety of scientific disciplines based on their unique structure and extraordinary properties, and remarkable progress in research and application have been achieved. Carbon nanotubes are regarded as ideal supporting materials for their high aspect ratio and excellent stability. Up to date, many works have been reported on supporting catalysts and delivering bio-active molecules, all the enticing results indicate a promising future for application. This thesis focused on the preparation of carbon nanotubes supported catalyst and carbon nanotubes based anti-cancer drug delivery system. For supporting catalyst, a class of highly water soluble polymer grafted carbon nanotubes was prepared with a facile method in mild condition with precipitation polymerization. The nickel nanoparticles were loaded onto the PAA-g-MWNTs based on the interaction between PAA segments and nickel ion in solution and reduction process of hydrazine. At last, hydrogenation of citral was conducted to study the catalysis property of prepared Ni-MWNTs composites. For delivering anti-cancer drug, carbon nanotubes were cut into short tubes via oxidation process to enhance the capability of entrancing cell membrane. The as-prepared short carbon nanotubes were entitled with excellent dispersion property and good biocompatibility by further modified with hydrophilic polymer. Then, the hydrophilic polymer modified carbon nanotubes were attached with fluorescent tag and tumor-targeting molecule via covalent bonding. Finally, the multi-functional drug delivery system was investigated via cell experiments and the results were as follows:1) Poly(acrylic acid) grafted MWNTs (PAA-g-MWNTs) were prepared with precipitation process using acetone as solution and AIBN as initiator in mild condition. The grafting amount can be modulated by changing reaction solution, reaction time and the concentration of AIBN, the maximum grafting amount can be modulated to as high as 12 wt.%. The resultant PAA-g-MWNTs were found to be highly water soluble and hard to aggregate to form large granules. For biomedical purpose, oxidized short MWNTs were modified with amino functionalized polyethylene glycol (PEG) under catalysis of EDC and NHS. The polymer graft amount can be controlled by changing feed ratio of PEG to MWNTs and the graft amount can be as high as 50 wt.%. The resultant MWNTs-PEG could be well dispersed in water and exhibited no obvious cytotoxicity in the concentration of 0-100 pμg/ml indicating a promising future for biomedical application.2) By means of solution reduction process, the nickel ion was successfully reducted into nickel nanoparticles and deposited onto the side wall of PAA-g-MWNTs. The deposition morphology was controlled by changing temperature and surface functionality. Finally, MWNTs composites with ell dispersed nickel nanoparticles (Ni-MWNTs) were prepared in an optimized condition. The resultant Ni-MWNTs exhibits good magnetic response property which offers a way to a quick separation after reaction. The hydrogenation activity and selectivity of Ni-MWNTs nanocomposites forα,β-unsaturated aldehyde (citral) was studied, and the experimental results showed that the citronellal, an important raw material for flavoring and perfumery industries, is the favorable product with a percentage as high as 86.9%, which is 7 times higher than that of catalyzed by Ni-supported active carbon (Ni-AC).3) The MWNTs were firstly cut into short tubes by treated with H2SO4/HNO3 and different length of tubes was prepared by varying the treating time. The resultant carbon nanotubes were as short as 100 nm and were further modified with polyethylene glycol (PEG) under catalysis of EDC and NHS then the fluorescent tag and FA targeting group were introduced onto MWNTs successively. The Functionalized MWNTs exhibits good biocompatibility both in vitro and in vivo. Doxorubicin (DOX) was loaded onto the sidewall of MWNTs viaπ-πstaking interaction and the loading efficiency can be modulated to as high as 59%. DOX loaded MWNTs resulted in a significant Hela cell death and the DOX/Cut-MWNTs-PEG-FITC-FA showed an enhanced cell-killing effect toward Hela cells, which was higher than free DOX with the same concentration. This property was regarded as drug targeting delivery and the result revealed that nano drug delivery system can target killing cancer cells with high efficiency, therefor holds great promise in cancer therapy.