Microcrystalline SWNT material Original Research Article

We report here on an optimised purification method for carbon nanotubes which yields microcrystalline single wall nanotube (SWNT) material. For this work the material is characterised using a scanning tunneling microscope (STM) with atomic resolution at room temperature. In the purified material, tubes with armchair structure prevail (diameter 1.7–2.5 nm), although tubes with other chiralities are also present. Based on STM topographic images the purity of SWNT material in the final step was estimated to be between 70 and 80%. In contrast to well-known ropes of SWNTs, the microcrystalline material is composed of parallel SWNTs which are not twisted, forming a crystalline structure in two dimensions. An interesting point is that tubes from one microcrystal appear from the STM images all to have the same chirality.