Catalyst-free synthesis of single-wall boron nitride nanotubes via laser ablation

Boron nitride nanotubes (BN-NTs) were synthesized in "mass" quantities (∼0.6 g/h) using a continuous CO₂ laser ablation reactor described in the literature. High-resolution electron microscopy (HRTEM) analyses have shown the nanotubes to be organized in "ropes" comprising ∼10 tubes. Analysis of HRTEM images indicate that the majority of the tubes are zig-zag. The chemical composition of the tubes was confirmed using electron energy loss spectroscopy (EELS) analysis, which also determined that nanoparticles terminating tube ends were composed of pure boron covered by BN fullerene-like "cages". The growth mechanism of the nanotubes seems to be "root-based" with tubes growing from boron nanoparticles dispersed throughout the samples; the non-particle-terminated ends of the tubes exhibit flat "caps" characteristic of BN-NTs.