A Benzimidazole-pyridine-2,3-dicarboxylic Acid Bridged Zinc(Ⅱ)Coordination Complex–crystal Structure,Quantum Chemistry and Luminescence

The structure of a zinc（Ⅱ） coordination complex（1）, [C14 H10 N3 O5 Zn1.5]n or [Zn1.5（bzim）（pydc）（H2 O）]n（H2 pydc = pyridine-2,3-dicarboxylic acid, Hbzim = benzimidazole）, has been determined by X-ray crystallography and characterized by elemental analysis, IR spectrum and luminescence. Chemical formula： C14 H10 N3 O5 Zn1.5. It crystallizes in the monoclinic system, space group P21/c with a = 12.303（4）, b = 12.052（4）, c = 10.212（3） ？, β = 104.147（4）, V = 1468.3（8） ？3, Z = 4, Mr = 398.30, Dc = 1.802 g/cm3, F（000） = 800, μ = 2.501 mm-1 and S = 1.000. The 2-D network architecture of 1 is constructed from benzimidazole, zinc and pyridine-2,3-dicarboxylic acid. The quantum-chemical calculations have been performed on ‘molecular fragments’ extracted from the crystal structure using the B3 LYP method in Gaussian 09. The luminescence spectrum shows that complex 1 emits blue luminescence.

Energy transfer from Tb^(3+) to Eu^(3+) in zinc lead borate glass

In order to sensitize the luminescence of Eu3+ ions in heavy metal glass,zinc lead borate glass samples containing various concentrations of Eu3+ and Tb3+ ions were prepared to study the Tb3+ to Eu3+ non-radiative energy transfer phenomena.Energy level structures of Tb3+ and Eu3+ ions were plotted to show the excitation and energy transfer routes.Efficient energy transfer from Tb3+ to Eu3+ was observed and studied qualitatively in terms of doping concentrations.The sensitization turned out to be less effective than expected.Further studies to characterize the oxidation of Tb3+ into tetravalent state and to examine the mechanism of energy transfer are proposed.

Size-induced effect on cathode luminescence spectra of CsI(Na) and CsI(Tl) crystals

We investigated the cathode luminescence characteristics of CsI(Na)and CsI(Tl)crystals by the spectrum and structure properties at room temperature.We fabricated three different sizes of CsI(Na)and CsI(Tl)crystals and measured their luminescence spectra under cathode rays.We found that CsI(Na)cathode luminescence peaks appear at 420 and 305 nm,and CsI(Tl)cathode luminescence peaks are 540 and 410 nm,the grain size affects CsI(Na)luminescence significantly,and the Na-related420 nm luminescence intensified relatively when the average grain size reaches^20μm,which becomes weak when the grain size is down to nano-scale.But the cathode luminescence spectra of CsI(Tl)crystals with different size have no obvious changes.Our explanations for these phenomena are that the different impurities in the same host material CsI lead to different luminescence mechanisms.These cathode luminescence characteristics indicate the suitability of CsI(Na)and CsI(Tl)crystals to match photomultiplier tube for large area crystal detector development.

White light-emitting Ba0.05Sr0.95WO4:Tm3+Dy3+phosphors

Tm3＋ and Dy3＋） co-doped Ba（0.05）Sr0.95WO4 phosphors were synthesized by a low temperature combustion method. The structures of the samples were SrWO_4 phase and were identified by X-ray diffraction. The surface topographies of Ba_（0.05）Sr_（0.91）WO_4：0.01 Tm^（3＋） 0.03 Dy^（3＋） were tested by scanning electron microscopy. The particles are ellipsoid, and their average diameter is approximately 0.5 μm. The emission spectra of Ba_（0.05）Sr_（0.95）WO_4：Tm^（3＋） show a peak at 454 nm which belongs to the ~3 H_6→~1 D_2 transition of Tm^（3＋）, and the optimum doping concentration of Tm^（3＋） ions was 0.01. The emission spectra of Ba_（0.05）Sr_（0.95）WO_4：Dy^（3＋） consist of the ~4 F_（9/2）→~6 H_（13/2） dominant transition located at 573 nm, the weaker ~4 F_（9/_2→~6 H_（15/2） transition located at 478 and 485 nm. And the weakest ~4 F_（9/2）→~6 H_（11/2） transition located at660 nm, and the optimum doping concentration of Dy^（3＋） ions was 0.05. A white light is achieved from Tm^（3＋） and Dy^（3＋） co-doped Ba_（0.05）Sr_（0.95）MoO_4 crystals excited at 352-366 nm. With the doping concentration of Tm^（3＋） fixed at 0.01, the luminescence of Ba_（0.05）Sr_（0.95）MoO_4：Tm^（3＋）Dy^（3＋） is closest to standard white-light emissions when the concentration of Dy^（3＋） is 0.03; the chromaticity coordinates are（0.321,0.347）, and the color temperature is 6000 K.