Synthesis of the Elusive Doublewall Nanotubes and Nanocones(Horns) of MoS₂ via Focused Solar Ablation

The synthesis of fundamentally small MoS₂ nanotubes and nanocones(horns) that have proven elusive in prior studies has been achieved via ablation of a precursor mixture of crystallites of MoS₂ + MoO₃ by highly concentrated solar radiation. The special far-from-equilibrium conditions achieved in the solar furnace prove conducive to the generation of these singular nanostructures. Extensive electron microscopy and characterization results (transmission electron microscopy (TEM), electron diffraction (ED), X-ray diffraction (XRD), scanning TEM (STEM), and high angle annular dark field (HAADF)) reveal a range of nanoparticle shapes and sizes based on which reaction mechanisms are proposed. Molecular dynamics simulations indicate that the sizable thermal fluctuations intrinsically produced in the high-temperature solar reactor soften the MoS₂ nanostructures, yielding corrugated layers that favor nanostructures with only a few layers, in agreement with the experimental observations.