Microcrystalline SWNT material

We report here on an optimised purification method for carbon nanotubes whi ch yields microcrystalline single wall nanorube (SWNT) material. For this w ork the material is characterised using a scanning tunneling microscope (ST M) with atomic resolution at room temperature. Tn the purified material, tu bes with armchair structure prevail (diameter 1.7-2.5 nm), although tubes w ith 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 a nd 80%. In contrast to well-known ropes of SWNTs, the microcrystalline mate rial is composed of parallel SWNTs which are not twisted, forming a crystal line structure in two dimensions. An interesting point is that tubes from o ne microcrystal appear from the STM images all to have the same chirality. (C) 2000 Elsevier Science Ltd. All rights reserved.