Nanotube Structure of AsPSSe ( = 0, 1).

Single-wall nanotubes of isostructural AsPSSe ( = 0, 1) are grown from solid-state reaction of stoichiometric amounts of the elements. The structure of AsPS was determined using single-crystal X-ray diffraction and refined in space group . The infinite, single-walled AsPS nanotubes have an outer diameter of ≈1.1 nm and are built of corner-sharing PS tetrahedra and AsS trigonal pyramids. Each nanotube is nearly hexagonal, but the ≈3.4 Å distance between S atoms on adjacent nanotubes allows them to easily slide past one another, resulting in the loss of long-range order. Substituting S with Se disrupted the crystallization of the nanotubes, resulting in amorphous products that precluded the determination of the structure for AsPSSe. P solid-state NMR spectroscopy indicated a single unique tetrahedral P environment in AsPS and five different P environments all with different degrees of Se substitution in AsPSSe. Optical absorption spectroscopy revealed an energy band gap of 2.7 to 2.4 eV for AsPS and AsPSSe, respectively. Individual AsPS microfibers showed a bulk conductivity of 3.2 × 10 S/cm and a negative photoconductivity effect under the illumination of light (3.06 eV) in ambient conditions. Thus, intrinsic conductivity originates from hopping through empty trap states along the length of the AsPS nanotubes.