Formation studies and controlled production of carbon nanohorns using continuousin situcharacterization techniques

Abstract

The formation of carbon nanohorns by laser ablation was investigated using a scanning differential mobility analyzer combined with an ultrafine condensation particle counter. The measurement technique provided time-resolved size distributions for the carbon nanoparticles every minute during the course of the production run. The instrument performance was reasonably stable most of the time; however, during laser ablation, shockwave oscillations leading to significant transient flow and pressure variations were shown to disrupt the DMAs ability to measure accurate distributions. On the basis of the general trend observed in the data taken during the laser-ablation experiments, we found that the geometric mean diameter of the produced population shifted to larger particle sizes with increases in pulse width. For a given laser peak power and repetition rate, carbon nanoparticles of mobility diameter close to 100 nm were produced in a large abundance using longer laser pulse lengths (e.g., 10 ms) as compared to the shorter pulse lengths (e.g., 1 ms). A quantitative assessment of the particle size dispersion (using statistics like the geometric standard deviation) in relation to the laser pulse width could not be done with certainty as the shockwave disturbances produced by the laser-ablation process caused significant disruption to SMPS measurements. When laser ablation was not in operation, it was found that carbon nanoparticles with mobility diameters centred at about 20 nm could be produced by thermally desorbing the previously deposited carbon nanoparticles from the reactor wall at temperatures greater than 1300 K.

Antioxidant Deactivation on Graphenic Nanocarbon Surfaces

“…Single-wall carbon nanohorns (SWNHs) were produced by high-power Nd:YAG laser vaporization of pure graphite into background Ar gas at high temperature (1100 C) as described previously. [38] The short-SWNHs (s-SWNHs) used in these studies were produced by minimizing the laser pulse widths (0.5-ms, 4.5 J/pulse, 80Hz), yielding nanohorns with individual lengths < 10nm and roughly spherical aggregates with diameters typically between 40–60 nm, as assessed by high-resolution transmission electron microscopy (Hitachi, HF-3300 at 300kV). The growth time above 1000°C was limited to 8 ms, followed by several seconds annealing time at 1000°C within the tube furnace.…”

Interaction of carbon nanohorns with plants: Uptake and biological effects

“…Single wall carbon nanohorns (SWCNHs) were synthesized using high power laser vaporization setup as described early [37,38]. Briefly, the experimental setup includes a quartz tube reactor mounted inside a tube furnace operating at 1150C with flowing Argon (flow rate ~ 4600 sscm) at atmospheric pressure.…”

Laser Interactions for the Synthesis and In Situ Diagnostics of Nanomaterials

“…Diagnostics of the synthesis process, as shown in Fig. 7.5b, have been performed to characterize the growth environment [39][40][41], and it has been shown that SWNHs grow at *1 nm/ms growth rates (equivalent to the 1 lm/s growth rate of SWNTs with catalyst-assistance) [42].…”