SYNTHESIS AND STRUCTURAL CHARACTERISATION OF SINGLE WALL CARBON NANOTUBES FILLED WITH IONIC AND COVALENT MATERIAS

摘要

Carbon nanotubes have hollow interiors with internal diameters ranging from 0.5-20 run although more typically 1-4 nm. It is now well established that these internal cavities can be filled with crystalline and molecular materials. Filling of single walled carbon nanotubes (SWNTs) are normally filled by direct mixing of the molten filling material and the nanotubes at elevated temperature. Characterisation of filled carbon nanotubes relies mainly on high-resolution transmission electron microscopy (HRTEM) and extended resolution HRTEM techniques. The crystals formed within the narrower SWNTs are often only a few atoms in cross section with a large proportion of atoms lying on the surface of the encapsulated crystals. An extreme example is in the case of a 2 * 2 crystal of potassium iodide which is effectively an 'all surface' crystal. The structures of the nano-crystals encapsulated inside SWNTs show other significant differences compared to the corresponding bulk materials. For example, inter-atomic differences can be substantially greater (i.e. by as much as ～20%) for SWNT encapsulated materials. Several examples of filled SWNTs are described including those filled with simple metal halide salts, covalent metal halides and molecular species as in o-carborane.