The Tellurophosphate K_4P_8Te_4: Phase-Change Properties,Exfoliation, Photoluminescence in Solution and Nanospheres

摘要

We describe the inorganic polymer K_4P_8Te_4 which is soluble, giving solutions that exhibit white emission upon 355 nm laser irradiation. An indirect band gap semiconductor (E_g ≈1.4 eV), K_4P_8Te_4 crystallizes in the space group P2/m, with a = 6.946(1) A, b - 6.555(1) A, c = 9.955(2) A, and β = 90.420(3)° at 173(2) K. The compound features infinite chains of [P_8Te_4~(4-)] with covalent P-Te bonding and exhibits reversible crystal-glass phase-change behavior. When deposited from solution, the material forms highly crystalline K_4P_8Te_4 nanospheres. The thermal analysis, FT-IR, UV-vis diffuse reflectance, ~(31)P 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 K_4P_8Te_4 in solution studied with ~(31)P solution-state NMR spectroscopy, electrospray ionization mass spectrometry, and PDF analysis indicate exfoliation of [P_8Te~4(4-)] chains followed by rearrangement into molecular species.