Crystal Growth Kinetics of Nanocrystalline ZnS under Surface Adsorption

The crystal growth mechanism, kinetics, and microstructure development play a fundamental role in tailoring the materials with controllable size and morphology. In this study, by introducing the strong surface adsorption of the concentrated NaOH, two-stage crystal growth kinetics of ZnS nanoparficles was observed. In the first stage, the primary particles grow into a size over a hundred times of the original volume and the growth is controlled by the crystallographically specific oriented attachment. The first stage data were fitted by the ＂multistep OA kinetic model＂ built based on the molecular collision and reaction. In the second stage, following the dispersal of nanoparficles, an abrupt transition from asymptotic to parabola growth kinetics occurs, which can be fitted by a standard Ostwald ripening volume diffusion model. The presence of surface adsorption causes the two-stage growth kinetics and permits an almost exclusive OA-based growth to dominate in the first stage.

Recent Progress on Spectroscopy of Lanthanide Ions Incorporated in Semiconductor Nanocrystals

Doping luminescent lanthanide ions into semiconductor nanocrystals is an ideal approach for developing nanodevices for various applications. Quantum confinement effects are expected for lanthanide ions doped in small semiconductor nanocrystals. The most recent progress on the synthesis and spectroscopy of lanthanide ions in various semiconductor nanocrystals such as Ⅱ -Ⅵ, Ⅲ-Ⅴ and Ⅳ-Ⅵ families were systematically reviewed, focusing on our recent findings on the optical spectroscopy of Eu^3 ＋ doped in ZnO and TiO2 nanocrystals by wet chemical synthesis. The energy transfer from the band-gap excitation to lanthanides further confirmed that lanthanide ions could be successfully incorporated into the lattice sites in spite of the mismatch in ionic radii.

Syntheses and Structures of Two Isomorphous Metal-organic Coordination Complexes Based on 4-Pyrimidin-5-ylbenzoic Acid

The reactions of 4-pyrimidin-5-ylbenzoic acid （HL） with Co（NO3）2·6H2O and Ni（NO3）2·6H2O gave rise to two isomorphous mononuclear coordination complexes, namely, [CoL2（H2O）4] （1） and [NiL2（H2O）4] （2）. Both compounds were characterized by IR spectroscopy and single-crystal X-ray diffraction. X-ray crystallographic analyses reveal that they crystallize in monoclinic, space group P21/n. In the crystal structures of these two complexes, only one nitrogen atom of L coordinates to the metal center, and neither carboxylate group nor another nitrogen atom of L links to Co（Ⅱ） or Ni（Ⅱ）. 2D Layers with significant hydrogen bonds can be observed, and they are further linked by L to form a 3D supramolecular network. Nitrogen atoms are not involved in forming hydrogen bonds, but carboxylic groups of the ligands play an important role in the configuration of this hydrogen-bond layer.

Single-crystal Structure of ScAlMgO_4

Crystals of scandium magnesium aluminate, ScAlMgO4, were grown from the melt prepared from stoichiometric quantities of Sc2O3, Al2O3 and MgO. Single-crystal X-ray diffraction indicates that ScAlMgO4 crystallizes in the space group R3 m with a = b = 3.2506（9） A, c = 25.152（8）A, V= 230.16（11）A^3, Z= 3, F（000） = 234,μ = 2.424 cm^-1, the final R = 0.0381 and wR = 0.1061 for 1874 observed reflections with I 〉 2σ（I）. In ScAlMgO4, all Sc atoms are coordinated octahedrally, whereas AI or Mg atoms are forming a tetrahedron, or in a triangular bipyramid if one distant O atom is included. The structure of ScAlMgO4 is characterized by { [AlMgO4]^3-}∞^2 layers parallel to the ab plane, and they are further connected into a 3-dimen-sional framework by Sc atoms via O（1） atoms between the layers.

Peak wavelength selection guides of chip and phosphors for phosphor-converted white light-emitting diodes

The dependences of light efficiency of radiation （LER） and color-rendering index （CRI） of trichromatic white light-emitting diode （wLED）, composed of blue LED die, green/yellow, and red phosphors, on the peak wave- length of each primary were investigated by theoretical calculations, at correlative color temperature （CCT） from 2,700 to 6,500 K. The peak wavelength of InGaN based blue LED chip ranges from 450 to 471 nm, while those of Ca3Sc2Si3012：Ce3＋, b-SiA1ON：Eu2＋, and Y3A15012：Ce3＋ based green/yellow phosphors range from 511 to 572 nm, and those of Sr2SisN8：Eu2＋ and CaA1SiN3：Eu2＋ red phosphors range from 620 to 650 nm, which cover almost all the practically used, commercially available wave bands until now. Then, based on the results, selection guides of peak wavelengths for blue LED chip and phosphors to obtain tradeoff LER 〉280 lm.W-1 as well as CRI 〉80 in all CCTs are proposed. The favorable wave bands of each primary are suggested.

Optimization of light efficacy and angular color uniformity by hybrid phosphor particle size for white light-emitting diode

In this study, small- and large-particle-diameter phosphor powders were mixed together（hybrid phosphors）to balance light efficacy and angular color uniformity and pursue optimal results. Phosphor with small-particlediameter of 4 lm was employed and it was mixed into each large-particle-diameter phosphor of 10, 16, 22, and 26 lm,at mass percentage from 0 % to 50 % with an interval of10 %, respectively. Remote phosphor package was adopted and overall phosphor concentration was kept constant for better comparison. Moreover, absorption coefficient labs,scattering coefficient lscaand extinction coefficient lext of each hybrid phosphors were calculated based on Mie theory to further discuss the experiment results. Results show that, the introduction of small-particle-diameter phosphor to large one can highly improve angular color uniformity while only slightly reduce light efficacy. The optimal performance with angular color uniformity of91.6 % as well as normalized light efficacy of 95.7 % is achieved in the white light emitting diode with hybrid phosphors consisting of 60 wt% powder of 22 μm and40 wt% powder of 4 μm.