ABSTRACT
In addition to well-known carbon nanotubes (CNTs), described in hundreds of thousands of publications, the micro-and nanotubes (including core-shell inorganic nanotubes1) of a series of other inorganic compounds have been developed, mainly by the research groups of Tenne2-6 and Rao.7,8 Among extensive reviews,9-13 we note an excellent discussion of TiO2 nanostructures, including its nanotubes.14 Generally, the formation of tubular nanostructures requires layered, anisotropic, or pseudo-layered crystal structures.15 Inorganic nanotubes, which typically do not possess such structures, are usually synthesized using template-based methods, leading, however, to either amorphous, polycrystalline products or existing only in ultrahigh vacuum. Additionally, although initially the method of synthesis for the formation of nanotubular structures, such as, for example, WS2 and MoS2, involved starting from the respective oxides, it was well established that the gas-phase synthetic route (using metal chlorides, carbonyls, etc.) provides an alternative that is suitable for the synthesis of many closed caged structures and nanotubes hitherto unknown.16
