Novel Micro-and Nano-Structures Of Endohedral Fullerenes:Preparation And Properties

Endohedral fullerenes represent a special type of fullerenes. Because of the encapsulation of different atoms or clusters which can transfer specific number of electrons to the outer carbon cage, endohedral fullerenes are unique carbon nanostructures, exhibiting a lot of new physical and chemical properties inaccessible by the empty fullerenes and hold great application potentials in such fields as biomedicines and energy. On the other hand,ordered microstructures prepared by the assembly of atoms or molecules may improve the intrinsic physical and chemical properties of materials or even bring about new properties,and can be further used to construct functional devices directly correlated with the applications. The well-organized microstructure combined with adjustable HOMO-LUMO bandgap will bring bright applications of endohedral fullerenes in many fields. On the basis of the potential applications of fullerene nanostructures, in this dissertation we focused on the preparation of novel micro-and nanostructures of endohedral fullerens, and carried out the following works related to the self-assembly property of metal nitride clusterfullerene Sc3N@C80(Ik):(1). Using a supramolecular approach, we successfully prepared hexagonal nanorods of Sc3N@C80(In, hereafter the label of isomer h is ommited for clarity) encapsulated in zinc meso-tetra(4-pyridyl) porphyrin (ZnTPyP)(Sc3N@C80-ZnTPyP nanorods). By introducing water as the solvent of cetyltrimethylammonium bromide (CTAB) surfactant, the effects of solvent and the ratio of the reactants had been studied so as to control the length and size distribution of the Sc3N@C80-ZnTPyP nanorods. The encapsulation nature and hybrid structures of Sc3N@C80-ZnTPyP nanorods were confirmed by TEM, EDX, TGA, Raman spectroscopy and electrochemical study. XRD study on the internal structure of Sc3N@C80-ZnTPyP nanorods suggested that ZnTPyP molecules tended to self-assemble in the axial direction. UV-vis electronic absorption spectrum of Sc3N@C80-ZnTPyP nanorods shows broader and stronger absorptions in the visible region than those of the components Sc3N@C8o and ZnTPyP. The comparison of the UV-vis electronic absorption spectra of Sc3N@C80-ZnTPyP and C60-ZnTPyP nanorods revealed the influence of the electronic structures of fullerenes on the aggregative interactions between fullerene and ZnTPyP. The fluorescence emission intensity of Sc3N@C80-ZnTPyP nanorods exhibits a strong quenching (-80%) compared to the pure ZnTPyP nanotubes, suggesting that the photo-induced electron transfer from the excited ZnTPyP to Sc3N@C80might occur.(2). By using a liquid-liquid interfacial precipitation (LLIP) method, we successfully prepared micron-sized hexagonal single-crystalline Sc3N@C8o rods for the first time with the first utilization of p-xylene as solvent dissolving Sc3N@Cso. The effect of concentration of Sc3N@C80solution on the size and length of Sc3N@C80rods had been studied, indicating that the length of Sc3N@Cso rods can be readily controlled by varying the concentration of Sc3N@C80solution. The crystal structure of the Sc3N@C80rods has been investigated by XRD and electron diffraction pattern, pointing to the hexagonal system.The growth kinetics of Sc3N@C80rods had been studied by monitoring the morphology evolution of Sc3N@C80crystals, and a plausible mechanism was proposed, featuring an intermediate hexagonal star-shaped prism structure with grooves. Raman spectroscopic characterization confirmed that Sc3N@C8o rods were composed of monomeric pristine Sc3N@C80molecules and no polymerization has occurred in the crystal lattice. According to the UV-vis-NIR absorption spectroscopic study of Sc3N@Cso rods revealing much broader and stronger absorptions in the visible and near-infrared regions than that of the Sc3N@Cso solution, we concluded that the electronic structure of the Sc3N@C80molecule was largely perturbed upon the formation of micron-sized single-crystalline rods because of the strong intermolecular π-π interactions. Finally photoelectrochemical application of Sc3N@C80rods was studied based on Sc3N@C80rods-modified ITO electrode prepared by electrophoretic deposition, and a higher photocurrent response contributed to the one-dimentional single-crystalline structures was obtained, demonstrating the potential application of Sc3N@C80rods in photoelectric conversion.(3). Dice-shaped Sc3N@Cso cubes were successfully prepared for the first time by a modified liquid-liquid interfacial precipitation (LLIP) method with ultrasonication. The effect of concentration of Sc3N@C80solution on the size of Sc3N@Cso cubes had been studied, indicating that the size of Sc3N@C80cubes can be readily controlled by varying the concentration of Sc3N@C80solution. The growth mechanism of the dice-shaped Sc3N@C80cubes had been studied by varying the preparation conditions, including the choice of good and poor solvents as well as their volume ratio,the mixing manner of solvents (ultrasonication or vigorous vibration), suggesting that the formation of the dice shape with holes in each surface was due to the insufficiency of the solute supply during the crystal growth. Contrarily, perfect Sc3N@C80cubes were prepared by the tradiontional LLIP method without ultrasonication for which sufficient supply of the solute was responsible for the perfect crystal growth. Finally Sc3N@C80dice-shaped cubes were applied as catalyst support for oxygen reduction reaction and the performance was compared with that obtained on perfect Sc3N@C80cubes, revealing a higher limiting diffusion current density for Sc3N@C80dice-shaped cubes.