Spectral Property and Thermal Quenching Behavior of Tb^(3+)-Doped YAG:Ce Phosphor

A series of YAG：Ce,Tb phosphors were synthesized by vacuum sintering method.Moreover,their spectral properties,thermal quenching behaviors and color rendering properties were investigated systematically.The photoluminescence emission spectra of YAG：Ce,Tb show a great red shift compared with that of YAG：Ce.Direct energy transfer from Tb^（3＋） to Ce^（3＋） ions is verified based on the analysis of different photoluminescence spectra.The quenching temperature for Tb^（3＋）-doped YAG：Ce phosphors is about 490 K.The thermal activation energy is estimated to be 0.18 and 0.291 eV for Tb^（3＋）-doped YAG：Ce and YAG：Ce phosphors,respectively.The smaller activation energy for Tb^（3＋）-doped YAG：Ce means a more rapid nonradiative transition from 5d to 4f state,thus resulting in the lower quenching temperature.In addition,white LEDs with improved color rendering properties are achieved by using modified YAG：Ce,Tb phosphors.

Theoretical Study on the Structures,Spectra and Thermodynamic Property of Herbicidal Monosulfuron

The structure optimization and frequency calculation have been carried out at the B3LYP/6-31G＊ level towards herbicidal monosulfuron using density functional theory.The computed results showed that the intramolecular hydrogen bond N-H…N can stabilize the molecule.IR spectra,Raman spectra and thermodynamic properties under different temperatures were also obtained.The first vertical excited state electronic transition energy was calculated by time-dependent density function theory,and absorption wavelength of the lowest energy excitation was obtained at 339.59 nm,belonging to the near UV.These results provided the basis for studies on compound＇s structure-activity relationship.

Synthesis, Crystal Structure and Characterization of the Host-guest Type UOF

A new uranium（Ⅵ）-polycarboxylate framework with honeycomb（6,3） nets {[Zn（phen）_2（H_2O）_2][（UO_2）_2（BDC）_3]·2H_2O}n（1, BDC = benzene-1,4-dicarboxylate） was hydrotherrmally synthesized by the reactions of Zn（NO_3）_2·6H_2O with phenanthroine, UO_2（NO_3）_2·6H_2O and benzene-1,4-dicarboxylate. The complex was structurally characterized by FT-IR spectroscopy, powder XRD and X-ray single-crystal diffraction. Crystal data for 1： monoclinic, space group Cc with M_r = 1522.19, a = 14.9385（10）, b = 20.4922（13）, c = 15.9728（10） ？, β = 100.1240（10）°, V = 4813.5（5） ？~3, Z = 4, D_c = 2.100 g？cm^（–3）, μ = 7.293 mm^（–1）, F（000） = 2872, the final R = 0.0224 and w R= 0.0677 for 6522 observed reflections with I 〉 2σ（I）. Hydrogen bonds and π-π stacking interactions contribute to the structural extension and stabilization. Experimental band gap of about 3.57 e V indicates its broad gap semiconductor nature. UV-Vis spectra and solid-state luminescence were discussed in detail. The compound exhibits photocatalytic activities for the degradation of rhodamine B.

Structure,room-temperature magnetic and optical properties of Mn-doped TiO_2 nano powders prepared by the sol-gel process

TiO2 nano powders with Mn concentration of 0 at%-12 at% were synthesized by the sol-gel process, and were annealed at 500 ℃ and 800 ℃ in air for 2 hrs. X-ray diffraction （XRD） measurements indicate that the Mn-TiO2 nano powders with Mn concentration of 1 at% and 2 at% annealed at 500 and 800 ℃ are of pure anatase and rutile, respectively. The scanning electron microscope （SEM） observations reveal that the crystal grain size increases with the annealing temperature, and the high resolution transmission electron microscopy （HRTEM） investigations further indicate that the samples are well crystallized, confirming that Mn has doped into the TiO2 crystal lattice effectively. The room temperature ferromagnetism, which could be explained within the scope of the bound magnetic polaron （BMP） theory, is detected in the Mn-TiO2 samples with Mn concentration of 2 at%, and the magnetization of the powders annealed at 500 ℃ is stronger than that of the sample treated at 800 ℃. The UV-VIS diffuse reflectance spectra results demonstrate that the absorption of the TiO2 powders could be enlarged by the enhanced trapped electron absorption caused by Mn doping.

Synthesis,Characterization and Theoretical Studies on a Thiocarbamide Derivative Containing Schiff Base Group

A thiocarbamide derivative containing Schiff base groups,1,5-bis[4-（dimethylamino）benzylidene]thiocarbonohydrazide,has been synthesized and characterized by elemental analysis,IR,^1H NMR,UV and X-ray single-crystal diffraction.Density function theory（DFT） calculations at the B3LYP/6-31G＊ and PBE0/6-31G＊ levels for optimized geometries and electronic transition spectra have been performed.Comparative studies show that both B3LYP/6-31G＊ and PBE0/6-31G＊ methods can well reproduce the molecular structure,and the latter is more reliable than the former to simulate electronic spectra.NPA calculational results at the B3LYP/6-31G＊ level indicate the title compound to be a potential multidentate ligand to the metallic ions.Based on the vibrational analysis,thermodynamic properties at different temperatures have been obtained.

Far-infrared Absorption Spectra and Properties of SnO_2 Nanorods

Nanostructured materials have drawn considerable attention because they are promising candidates for nextgeneration electronic and photonic devices with low power consumption[1-5]. A number of methods, such as laser ablation[6], template-induced growth[7], arc discharge [8], vapor transport [9], and molecular-beam epitaxy[10] have been developed to synthesize Si, Ge, MgO,SnO2, GaN, and Ga2O3 nanowires or nanorods[11-15].……

Spectroscopic properties of ytterbium doped KLu(WO_4)_2

Monoclinic Yb3＋-doped KLu（WO4）2 （Yb：KLuW） crystal with large sizes was grown by top-seeded solution growth （TSSG） method. Room-temperature absorption and fluorescence spectra were measured. The ground-state energy-level splitting was 562 cm–1. The absorption cross section, peak emission cross section as well as the minimum inversion fraction ？min and the minimum absorbed pump intensity Imin were calculated. The measured emission lifetime was 0.676 ms and the emission spectral bandwidth （FWHM） was up to 55 nm. In comparison with established laser crystals the results suggested that this crystal has potential application in efficient tunable and femtosecond laser operation.