Sonochemical preparation of hollow nanospheres and hollow nanocrystals

Ceramic hollow spheres of MoS₂ and MoO₃ were obtained by sonochemical synthesis of MoS₂ and MoO₃ templated on silica nanoparticles (diameters 50-500 nm) followed by acid etching to remove the silica core. The resulting hollow materials have been characterized by elemental analysis, XPS, SEM, TEM, optical absorption, and hydrodesulfurization (HDS) studies. The TEM studies on the hollow ceramic materials indicate the formation of dispersed free spheres with a hollow core. The hollow materials obtained from thermally treated MoS₂/SiO₂ (450-700 °C) show the formation of layered MoS₂ (lattice fringes 6.2 Å) with a wall thickness of 6-8 layers. The MoS₂ hollow spheres are extremely active catalysts for the HDS of thiophene. Hollow spheres of MoO₃ are prepared in a similar fashion. Surprisingly, upon heating, hollow crystals of MoO₃ with sharp-edged truncated cubes containing inner voids are formed from the initial spheres.