Study On Functionalization Of Single-walled Carbon Nanotubes

Single-walled carbon nanotubes (SWNTs) have aroused increasing interest due to their unique structure and their mechanical and electronic properties. However, their insolubility in water or common solvents has made them difficult to be applied in many fields. Functionalization of SWNTs has received considerable attention in recent years due to the strong desire to improve SWNTs'solubility and the fascinating capacity to fabricate novel nanomaterials and nanodevices.The paper concentrates on the new trends of SWNTs and novel functional materials, seeks breakthrough in the crossing field. Three kinds of functional SWNTs were prepared including SWNTs functionalized with biocompatible amylose (cellulose), fluorescent ionic liquid (IL) and zinc-bipyridine frameworks. We devoted to develop new methods and to obtain new materials, thus mainly resolved four problems: 1) A"hierarchical self-assembly"model is put forward to explain the formation of the helical superstructure of amylose/SWNTs complex (A/S-C); 2) A kind of cheap biocompatible cellulose/SWNTs complex (C/S-C) was successfully prepared using IL as solvents; 3) A facile ion exchange strategy was presented for preparation of fluorescent SWNTs with high quantum yield (40%); 4) A kind of zinc-bipyridine frameworks was printed on SWNTs based on coordination chemistry combined with SWNTs chemistry. The details are as follows.1. Functionalization of SWNTs with biocompatible amyloseAn amylose/SWNTs complex (A/S-C) with regular helical morphology was successfully prepared. The resulting A/S-C was characterized and confirmed with 1H NMR, FTIR, Raman HR-TEM, FE-SEM and AFM. Besides the hydrophobic interaction, the existence of a mass of hydrogen bonds in the system was confirmed by variable-temperature 1H NMR. And a'hierarchical self-assembly'model, including the wrapping of amylose chains around SWNT and the hierarchical self-assembly of wrapped-SWNTs into the superstructural A/S-C, was put forward to explain the formation process of the helical A/S-C. The model will be helpful to study the formation of other polysaccharides, DNAs and polypeptides/SWNTs complexes. Subsequently, the tests of WST-1 and AO/EB staining reveal that the A/S-C has much better biocompatibility than SWNTs.2. Functionalization of SWNTs with biocompatible cellulose SWNTs, via noncovalent interaction, were functionalized with biocompatible cellulose in IL——1-butyl-3-methylimidazolium bromide. The resulting cellulose/SWNTs complex (C/S-C) was characterized and confirmed with HR-TEM,FE-SEM and Raman. The tests of WST-1 and AO/EB staining reveal that the water-soluble C/S-C has much better biocompatibility than SWNTs. Preparation of C/S-C using IL as solvent broke through the technique bottleneck in traditional functionalization of SWNTs with cellulose——the insolubility of cellulose in water or common solvents. Compared with the common molecules in biocompatible SWNTs including DNA, protein and polysaccharide, cellulose is the most abundant organic raw material in nature, and it is the only renewable resource that is available in large quantities. The cost reduction has an important meaning for the commercialization of biocompatible C/S-C.3. Functionalization of SWNTs with the fluorescent ILThe fluorescent IL——1,3-bis(9-anthracenylmethyl)imidazolium chloride ([bamim]Cl), is designed and synthesized. Subsequently, via ion exchange, [bamim]+ is attached to SWNT-COOK to produce SWNT-[bamim]. The successful formation of SWNT-[bamim] has been confirmed using HR-TEM, XPS, elemental mapping and elemental linear profiles analysis. The ion exchange strategy offers specific advantages including (1) that the resulting product retains a high fluorescence QY (40%), (2) that the fluorescent SWNTs complex retains one-dimension electronic states of SWNTs. Further, the ion exchange strategy is expanded to prepare other SWNT-IL combinations to demonstrate its universality. The strategy may open an avenue for exploring and preparing novel SWNTs-based nanomaterials and molecular devices with tailor-made structure, architecture and properties.4. Reversible photochemical behavior of SWNT-[bamim]The photochemical properties of SWNT-[bamim] were investigated by means of UV-Vis, fluorescence emission spectroscopy and HR-TEM. The results demonstrate that SWNT-[bamim] have the ability to photodimerize under longwave UV irradiation (365 nm) and to revert back to monomers at shortwave UV irradiation (254 nm). Based on the unique properties, SWNT-[bamim] is promising in the construction of organic-SWNTs solar energy storage devices, photoreponsive organic-SWNTs spin systems and other light-switchable materials.5. Functionalization of SWNTs with zinc-bipyridine frameworksA kind of zinc-bipyridine frameworks was printed on SWNTs based on coordination chemistry combined with SWNTs chemistry. Reaction of zinc acetate Zn(OAc)2 with carboxylic acid functionalized SWNTs (SWNT-COOH) afforded SWNTs complexes'zipped-together'by zinc carboxylate units, which may be viewed as SWNTs metal-organic frameworks (SWNT-MOF-1). Reactions of SWNT-MOF-1 with 2,2'-bipyridines and 4,4'-bipyridine gave two new SWNTs metal-organic framework products, the former being'unzipped'(SWNT-MOF-2), and the latter involving an additional ligand bridge between the zinc ions (SWNT-MOF-3). Inclusion of 2,2'-bipyridines and 4,4'-bipyridine into the SWNT-MOFs was confirmed by FTIR and 1H NMR spectroscopy. The microstructures of SWNT-MOF-2 and SWNT-MOF-3 were investigated by HR-TEM, XPS, elemental mapping and linear profiles analysis. Using this approach a wide range of transition metals and ligands could be incorporated into SWNTs systems and new types of functional SWNT-MOFs could be developed. This approach may eventually lead to new SWNT-based materials that could have diverse applications including gas transport and storage, catalysis etc.