Fabrication of BiTeI submicrometer hollow spheres

BiTeI submicrometer hollow spheres with diameters of 200-300 nm have been synthesized by an iodine transport hydrothermal method without the use of template materials or surfactants. The preparation was carried out in an autoclave in the temperature range 190-200 degreesC with Bi2Te3 and I-2 as reactants. X-Ray powder diffraction patterns and transmission electron microscopy images show that the product is BiTeI with a hollow sphere structure. The sphere wall is composed of BiTeI nanoparticles with an average diameter of 5 nm and a thickness of ca. 10 nm. A possible growth mechanism for the hollow structure is proposed. The first excitonic peak of the BiTeI hollow spheres is considerably blue shifted in comparison with the band gap of the bulk material, which can be attributed to quantum confinement effects.