| Since carbon nanotubes (CNTs) display unique structures and remarkable physical properties, various applications of CNTs have emerged in materials, catalysis and life sciences etc. In terms of applications, the functionalization of nanotubes is extremely important, as it increases their solubility and processability, and also combines the unique properties of CNTs with other various useful function groups.Up to date, a number of methods have been developed to prepare functionalized CNTs, which can be divided into four major approaches:(1) non-covalent modifications, (2) covalent functionalization, (3) endohedral filling CNTs with other materials, (4) decoration of CNTs with metal nanoparticles. Among these, the first two methods have been used widely in the research of CNTs.In this paper, different functionalized multi-walled carbon nanotubes (MWNTs) had been prepared mainly through covalent approach as the covalent functionlization can not only improve CNTs'solubility and processability, but also afford their novel properties. Our main work could be divided into three parts. Part I:using carboxyl functionalized MWNTs as carriers, Au nanoparticle and magnetic Fe3O4 nanoparticle decorated MWNTs were prepared further. Partâ…¡:Cu-Zn human superoxide dismutase (Cu-Zn SOD) covalently functionalized MWNTs were prepared via amidation reaction, where the delivery of SOD-g-MWNTs into cells and the toxicity of MWNTs-COOH and SOD-g-MWNTs were studied as well. Part III:poly (p-styrenesulfonic acid) grafted multi-walled carbon nanotubes (PSSA-g-MWNTs) were prepared as solid acid catalysts in applications of alkylation of hydroquinone with tert-butanol and esterification of lauric acid with methanol, the results showed that PSSA-g-MWNTs were of high catalytic activity. The main research contents and results are shown as follow:1. Firstly, two kinds of carboxyl functionalized MWNTs were prepared via different methods. One was polyacrylic acid functionalized MWNTs (PAA-g-MWNTs) which were prepared by the in situ polymerization, the other was MWNTs-COOH which could obtained by oxidation of pristine MWNTs. Secondly, Au nanoparticles were reduced onto PAA-g-MWNTs through the interaction of Au precursors and carboxyl groups on MWNTs. As PAA grafted MWNTs had held the electronic structure of pristine MWNTs, Au nanoparticles decorated PAA-g-MWNTs could be further used in catalysis. Thirdly, magnetic Fe3O4 nanoparticles were decorated onto MWNTs-COOH by chemical coprecipitation. Since Fe3O4 functionalized MWNTs showed good magnetic response, and MWNTs-COOH as carriers which were much shorter than pristine MWNTs could be ingested by cells effectively, Fe3O4 functionalized MWNTs showed great potential in target drug delivery.2. Cu-Zn SOD covalently functionalized MWNTs had been synthesized via amidation reaction. We could control the grafted ratio of Cu-Zn SOD by taking control of the ratio of raw materials, and the grafted ratio of SOD evaluated by TGA could up to 27 wt%. Furthermore, SOD-g-MWNTs were labeled by FITC to trace the delivery of SOD by MWNTs into cells. Finally, the toxicity of MWNTs-COOH and SOD-g-MWNTs was also studied through MTT method, which showed both were of low toxicity.3. PSSA-g-MWNTs were successfully prepared by in situ polymerization of sodium p-styrenesulfonate in the presence of MWNTs, followed by fluxing with concentrated HC1. The graft ratio of PSSA evaluated by TGA was 23.6 wt%. Due to the existence of copious sulfonic groups, PSSA-g-MWNTs could be well dispersed in polar solvent to form a stable black solution. Then, PSSA-g-MWNTs as solid-acid catalysts were applied in alkylation of hydroquinone with tert-butanol and esterification of lauric acid with methanol. Catalysis results showed PSSA-g-MWNTs were of high catalytic activity. As good solid acid catalysts, PSSA-g-MWNTs could be easily separated from the products by filtration and their catalytic activity could be withheld by treated with sulphuric acid after three recycles. |
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