The Tellurophosphate K4P8Te4: Phase-Change Properties, Exfoliation, Photoluminescence in Solution and Nanospheres

We describe the inorganic polymer K4P8Te4 which is soluble, giving solutions that exhibit white emission upon 355 nm laser irradiation. An indirect band gap semiconductor (E-g approximate to 1.4 eV), K4P8Te4 crystallizes in the space group P2(1)/m, with a = 6.946(1) angstrom, b = 6,555(1) angstrom, c = 9.955(2) angstrom, and beta = 90.420(3)degrees at 173(2) K. The compound features infinite chains of [P8Te44-] with covalent P-Te bonding and exhibits reversible crystal-glass phase-change behavior. When deposited from solution, the material forms highly crystalline K4P8Te4 nanospheres. The thermal analysis, FT-IR, UV-vis diffuse reflectance, P-31 magic angle spinning solid-state NMR spectroscopy, and pair distribution function (PDF) analysis for the crystal and glass forms and ab initio electronic structure calculations by the. screened-exchange local density function approximation are also reported. Speciation of K4P8Te4 in solution studied with P-31 solution-state NMR spectroscopy, electrospray ionization mass spectrometry, and PDF analysis indicate exfoliation of [P8Te44-] chains followed by rearrangement into molecular species.