Structure, Luminescent Sensing and Proton Conduction of a Boiling-Water-Stable Zn(II) Metal-Organic Framework

A novel Zn(II) metal-organic framework [Zn4O(C30H12F4O4S8)3]n, namely ZnBPD-4F4TS, has been constructed from a fluoro- and thiophenethio-functionalized ligand 2,2′,5,5′-tetrafluoro-3,3′,6,6′-tetrakis(2-thiophenethio)-4,4′-biphenyl dicarboxylic acid (H2BPD-4F4TS). ZnBPD-4F4TS shows a broad green emission around 520 nm in solid state luminescence, with a Commission International De L’Eclairage (CIE) coordinate at x = 0.264, y = 0.403. Since d10-configured Zn(II) is electrochemically inert, its photoluminescence is likely ascribed to ligand-based luminescence which originates from the well-conjugated system of phenyl and thiophenethio moieties. Its luminescent intensities diminish to different extents when exposed to various metal ions, indicating its potential as an optical sensor for detecting metal ion species. Furthermore, ZnBPD-4F4TS and its NH4Br-loaded composite, NH4Br@ZnBPD-4F4TS, were used for proton conduction measurements in different relative humidity (RH) levels and temperatures. Original ZnBPD-4F4TS shows a low proton conductivity of 9.47 × 10−10 S cm−1 while NH4Br@ZnBPD-4F4TS shows a more than 25,000-fold enhanced value of 2.38 × 10−5 S cm−1 at 40 °C and 90% RH. Both of the proton transport processes in ZnBPD-4F4TS and NH4Br@ZnBPD-4F4TS belong to the Grotthuss mechanism with Ea = 0.40 and 0.32 eV, respectively.

Atmosphere-sensitive photoluminescence of CoxFe3−xO4 metal oxide nanoparticles

CoxFe3−xO4 (0.4 < x < 2.5) nanoparticles show a broad green emission induced by surface OH-groups with a lower stability regarding UV-photoinduced dehydroxylation on Fe-rich (x ≤ 1.6) nanoparticles.

Synthesis and Photoluminescence Properties of SrLaAlO4: Ti Green-Emitting Phosphor

Ti-doped SrLaAlO4 green-emitting phosphor was synthesized via solid-state reactions in air and N2 atmosphere. Sample heated in air showed no emission, however, sample heated in N2 showed broad green emission around 492 nm and broad near-infrared emission around 950 nm by 321 nm near-ultraviolet excitation. XPS measurement and UV-Vis diffuse reflectance spectra suggest that Ti in the sample was reduced to Ti3+ state when the sample was heated in N2. Possible emission mechanism of the sample can be explained as O2-–Ti3+ charge-transfer transition.

Green Emission of Tellurite Based Glass Containing Erbium Oxide Nanoparticles

Investigation on green emission and spectral intensity of tellurite based glass containing erbium oxide NPs is one of the crucial issues. Tellurite based glass containing erbium oxide NPs with the composition of{[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.3}0.95(Er2O3)0.05has been prepared by using conventional melt-quenching method. The structural and optical properties of the glass sample were characterized by using XRD, FTIR, UV-Vis absorption, and PL spectroscopy. The amorphous structural arrangement was proved through XRD method. The formation of TeO3and BO3units was revealed by FTIR analysis. Five transition states of excitation were shown in UV-Vis spectra which arise from the ground state4I15/2to the excited states4G11/2+2H9/2+4F5/2+4F7/2+2H11/2+4S3/2+4F9/2+4I9/2+4I11/2. The intensity parametersΩt(t=2, 4, 6) are calculated and follow the trend ofΩ2>Ω4>Ω6. Broad green emission at 559 nm under 385 nm excitation was obtained.

Luminescent Properties of Eu2+, Eu3+ and Dy3+ Co-Activated SrAl2O4 Nanocrystals

By the control of the reducing atmospheres in the one-pot combustion reactions, Eu2+, Eu3+ and Dy3+ co-activated strontium aluminate oxide were synthesized. X-ray diffraction confirmed the formation of monoclinic SrAl2O4 nanocrystals. The photoluminescence spectra of the phosphors were measured. It is found that three sharp emissions at 483, 570 and 615 nm were superimposed onto the broad green emission band at about 520 nm. The origins of the broad green luminescent band, the sharp blue at 483 nm, and sharp yellow emissions at 570 nm and the sharp red emissions at 615 nm can be attributed to the 4f65d1→4f7 transitions of Eu2+ ions, the 4F9/2→6H15/2 transition of Dy3+ ions, the 4F9/2→6H13/2 transition of Dy3+ ions, and the 5D0–7F2 transition of Eu3+ ions in the SrAl2O4 nanocrystals, respectively. The results indicate that the white light emitting phosphors are possible by tuning the relative molar percentages of Eu2+, Eu3+ and Dy3+ in the phosphors.

Luminescent Properties, Afterglow Behavior and Thermoluminescence Characteristics of (Eu, Dy) Doped Sr3Al2O6 Phosphors

(Eu, Dy) doped Sr3Al2O6 phosphors with high brightness and long afterglow were achieved by a high-temperature solid state reaction. Luminescence measurements indicate that the phosphor Sr3Al2O6:Eu prepared in normal atmosphere exhibits a sharp orange emission peaking at 591 nm excited by 221nm light, which is intrinsic f-f transition generated from Eu3+. Whereas, the phosphors Sr3Al2O6:Eu and Sr3Al2O6:Eu,Dy prepared in a weak reducing atmosphere show both a sharp orange emission peaking at 591nm excited by 221-nm light and a broad green emission peaking at 510nm excited by 328nm light, which resulted from Eu2+ transition between 4f65d1 and 4f7 electron configurations. The investigation results suggest that Eu3+ and Eu2+ co-exist in Sr3Al2O6 matrix synthesized in weak reducing atmosphere. In all samples, only Sr3Al2O6: Eu, Dy prepared in a weak reducing atmosphere has high intensity afterglow after excited by the UV source. The decay curve of Sr3Al2O6: Eu, Dy phosphor contains the rapid-decaying process and the slow-decaying process and can be fitted by a bi-exponential decay function. The measurement of thermal simulated luminescence demonstrates that only appropriate deep trap energy level and high trap concentration can generate optimum long-afterglow performance.

A NOVEL METHOD FOR PREPARING ZnSnO NANOFIBERS

This paper reports that ZnSnO nanofibers (ZSNFs) were synthesized by thermal oxidation of ZnSn alloys. ZnSn alloys were prepared by cold press and sintering (powder metallurgy). The structure and optical properties were characterized by X-ray diffraction (XRD), micro-Raman scattering technology, field emission scanning electron microscopy (FESEM) and photoluminescence (PL) spectrum. The micro-Raman scattering spectra of ZSNFs show four Raman peaks at 574, 1156, 1729 and 2330 cm-1. The diameter and length of ZSNFs are about 50 nm and 60 μm, respectively. The room temperature PL spectra of ZSNFs shows the near-band-edge emission at ~391 nm and a broad green emission at ~493 nm.

Luminescence of nanocrystalline ZnS:Pb2+

ABSTRACTNanocrystalline ZnS:Pb2+ is synthesized via a precipitation method. The luminescence is studied and the influence of the size of the nanocrystals on the luminescence properties is investigated. Nanocrystalline ZnS:Pb2+ shows a white emission under UV excitation. At least two luminescence centers are involved. One center is identified as a Pb2+ ion located on a regular Zn2+ site and gives a red emission under 480 nm excitation. The luminescence properties of this emission are characteristic for transitions on Pb2+ ions. The other centers are not as well defined and give a broad green emission band under 380 nm excitation and also show luminescence properties typically observed for Pb2+. The green emission probably originates from a charge-transfer like D-band emission of Pb2+ in ZnS close to a defect (e.g. an S2− vacancy or an O2− ion on an S2− site). A relation between the temperature quenching of the emissions and the band gap is observed and indicates that photoionization occurs.