Single-wall carbon nanotubes prepared with different kinds of Ni–Co catalysts: Raman and optical spectrum analysis

The addition of acetates and nitrates for the synthesis of single-wall carbon nanotubes via laser ablation was explored. Targets containing nominal amounts of acetates or nitrates in addition to Ni and Co catalysts were compared to a standard target containing only Ni and Co at temperatures ranging from 1000 to 1200 degrees C. The as produced web-like soot was characterized by transmission electron microscopy, Raman spectroscopy and optical absorption spectroscopy. All samples showed a linear increase in SWCNT mean diameter with temperature, however, the rate of mean diameter change with temperature differed for the various targets, more so at lower temperatures. The addition of nitrates improved the SWCNT relative yield over all the temperatures used, whereas the inclusion of acetates improved the relative yield only at lower temperatures. The above results were discussed and analyzed according to the porous structure of the targets resulting from the decomposition of the acetates and nitrates and consequential thermal diffusion changes.