Semiconducting Single‐Wall Antimony Oxide Nanotubes and Oxidotritelluridoantimonate(V) Anions

ABSTRACT Black, needle‐shaped crystals of K 6 Sb 12 O 18 (SbOTe 3 ) 2 · n H 2 O ( n ≈ 5) were grown in high yield from an alkaline medium under hydrothermal conditions. Microporous, single‐walled Sb 12 O 18 nanotubes dominate the hexagonal crystal structure of the cetineite‐type. Antimony(III) atoms form the outer and oxygen atoms the inner wall of the nanotube, making it radially dipolar, similar to a cylindrical capacitor. The inner wall is decorated with potassium cations, and water molecules fill the remaining internal volume of the nanotube. Stacks of the hitherto unknown oxidotritelluridoantimonate(V) anion, (SbOTe 3 ) 3− , fill the trigonal channels in the packing of the nanotubes. As with other modifications of Sb 2 O 3 , the filled bonding and empty antibonding states of the nanotubes are separated by a wide band gap of about 3.6 eV. In this energy gap, the molecular orbitals of the (SbOTe 3 ) 3− anions are located. Electronic excitation involves a charge transfer from the anions to the nanotubes, which are thereby heavily n‐doped and exhibit semiconducting behavior. Modification of the reaction conditions results in the crystallization of the tellurium‐rich cetineite K 6 Sb 12 O 18 (Te 3 ) 2 (Te 2 ) 3 ·5H 2 O or the cetineite K 18 Sb 36 O 54 (SbOTe 3 ) 2 (Te 2 ) 6 ·22H 2 O, which contains Sb 36 O 54 nanotubes with an even wider diameter.