A non-carbon nanotube is a cylindrical molecule often composed of metal oxides, or group III-Nitrides and morphologically similar to a carbon nanotube. Non-carbon nanotubes have been observed to occur naturally in some mineral deposits.
A few years after Linus Pauling mentioned the possibility of curved layers in minerals as early as 1930, some minerals such as white asbestos (or chrysotile) and imogolite were actually shown to have a tubular structure. However, the first synthetic non-carbon nanotubes did not appear until Reshef Tenne et al. reported the synthesis of nanotubes composed of tungsten disulfide (WS2) in 1992.
In the intervening years, nanotubes have been synthesised of many non-carbon materials, such as vanadium oxide and manganese oxide, and are being researched for such applications as redox catalysts and cathode materials for batteries.
Non-carbon nanotubes are morphologically similar to carbon nanotubes and are observed in some mineral deposits of natural origin. Synthetic structures of this type were first reported by the group of Reshef Tenne in 1992.
Typical non-carbon nanotube materials are 2D layered solids such as tungsten(IV) sulfide (WS2), molybdenum disulfide (MoS2) and tin(IV) sulfide (SnS2). WS2 and SnS2/tin(II) sulfide (SnS) nanotubes have been synthesized in macroscopic amounts. However, traditional ceramics like titanium dioxide (TiO2), zirconium dioxide (ZrO2) and zinc oxide (ZnO) also form non-carbon nanotubes. More recent nanotube and nanowire materials are transition metal/chalcogen/halogenides (TMCH), described by the formula TM6CyHz, where TM is transition metal (molybdenum, tungsten, tantalum, niobium), C is chalcogen (sulfur, selenium, tellurium), H is halogen (iodine), and the composition is given by 8.2