Pulsed KrF-laser synthesis of single-wall-carbon-nanotubes: effects of catalyst content and furnace temperature on their nanostructure and photoluminescence properties

In this article, we report on the use of a pulsed KrF-laser (248 nm, 20 ns) for the synthesis of single wall carbon nanotubes (SWCNTs) from the ablation of a graphite target loaded with Co/Ni catalyst, under various growth conditions. By varying the Co/Ni catalyst load of the graphite target, from 0 to 2.4 at.%, the laser synthesized SWCNTs, under a furnace temperature (Tf) of 1,100 °C, were found to be decorated by C60 buckyballs, of which the density decreases as the catalyst content is increased. The effect of the catalyst content of the laser-ablated graphite target on the produced carbon nanostructures (C60 vs. SWCNTs) was systematically investigated by means of various characterization techniques, including Raman spectroscopy, thermogravimetry, and SEM/HR-TEM microscopies. A [Co/Ni] ≥ 1.2 at.% was identified as the optimal concentration for the production of SWCNTs without any detectable presence of C60 buckyballs. Thus, under the optimal growth conditions (i.e., [Co/Ni] = 1.2 at.% and Tf = 1,100 °C), the produced SWCNTs were found to be characterized by a very narrow diameter distribution (centered on 1.2 nm) with lengths in excess of 10 μm. By increasing Tf from 900 to 1,150 °C, the diameter of the SWCNTs can be varied from ~0.9 to ~1.3 nm. This nanotube diameter variation was evidenced by Raman and UV–Vis absorption measurements, and its effect on the photoluminescence of the SWCNTs is presented and discussed.