We report on a method of synthesizing Mn 4þ -activated ZnSiF 6 Á6H 2 O hydrate phosphor by the chemical reaction in a Teflon beaker. The structural and optical properties of ZnSiF 6 Á6H 2 O:Mn 4þ are investigated using x-ray diffraction measurement, photoluminescence (PL) analysis, PL excitation spectroscopy, diffuse reflectance measurement, and Raman scattering spectroscopy. The synthesized phosphor exhibits a series of sharp red emission peaks at $630 nm, which is characteristic for Mn 4þ ions. The luminescent study is focused on the thermal quenching phenomenon above $300 K and is found to be caused by thermal decomposition of the ZnSiF 6 Á6H 2 O host. Degradation in the PL intensity under near-UV light illumination has also been observed to occur in this phosphor. V C 2013 AIP Publishing LLC. [http://dx.

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Photo-induced degradation behaviors of the red-emitting ZnSiF 6 • 6H 2 O:Mn 4+ hydrate phosphor are studied using X-ray diffraction measurement, photoluminescence (PL) analysis, PL excitation spectroscopy, PL decay analysis, diffuse reflectance spectroscopy, and electron spin resonance (ESR) measurement. The ZnSiF 6 • 6H 2 O:Mn 4+ hydrate phosphor exhibits remarkable degradation in the PL intensity under Xe lamp exposure for a few minutes. Coherent laser beams also induce degradation and its degree is in the order of Ar + (488 nm) > He−Cd (325 nm) > He−Ne laser (632.8 nm). The degradation mechanism is found to be due to change in the valence state of manganese ions from Mn 4+ to Mn 5+ by the photooxidation (Mn 4+ → Mn 5+ ) or disproportionation reaction (2Mn 4+ → Mn 3+ + Mn 5+ ). This is supported by the facts that Mn 4+ ion has larger absorbance at 488 nm than at 325 or 632.8 nm and that the Mn 5+ -related absorption structures appear in the diffuse reflectance spectra at wavelengths below ∼700 nm. The ESR measurement also confirms the decreased Mn 4+ spin density in the sample exposed with Xe lamp. A comparative discussion is given on the PL properties of the two different hydrate phosphors, ZnSiF 6 • 6H 2 O:Mn 4+ and K 2 SnF 6 • H 2 O:Mn 4+ .

Direct electro-oxidation of C3H6 was achieved using a solid polymer electrolyte (SPE) electrolysis cell. PtOx anode prepared by mild oxidation of Pt black exhibited superior activity for propylene oxide (PO)...