Influence of Aging and 2-hydroxyethyl-methacrylate Content on the Color Stability of Experimental 2-hydroxyethyl-methacrylate-added Dental Glass Ionomers

Color stability of dental resin modified glass ionomer （RMGI） has been a challenge to dentistry; therefore, systematic changes in 2-hydroxyethyl methacrylate （HEMA） content were performed experimentally to find an idea to enhance the color stability. Changes in color （△E＊ab） and color coordinates （△L＊, △a＊ and △b＊） of experimental 10-50 wt pct HEMA-added dental glass ionomers （HAGIs） and corresponding RMGIs were determined after 5000 cycles of thermocycling. Color changes of HAGIs were not influenced by the HEMA content while △L＊, △a＊ and △b＊ values were influenced by the HEMA content. Color stability of 30% or 40% HEMA-added HAGIs was not different from those of the commercial RMGIs. Since the influence of HEMA itself on the color stability of HAGIs was limited, compositional modification to increase the color stability of these materials should be developed.

Effect of phosphor sedimentation on photochromic properties of a warm white light-emitting diode

In the process of producing a white light emitting diode, the consistency of the optical coherence and stability of the photochromic properties is a crucial index for measuring the quality of the product. Phosphor sedimentation is a significant factor affecting optical coherence, thus, in this paper, seven sets of control experiments were set up with the phenomenon of the phosphor precipitation at time intervals 0, 2, 5, 10, 20, 30, and 40 min.The color coordination concentration and optical properties were also tested. The results indicate that phosphor sedimentation occurs between 0 and 20 min, during which the color coordinate placement is concentrated, the central coordinates are(x = 0.4432 ± 0.004, y = 0.4052±0.002); the quality was verified because the supply demand chain management(SDCM) was no greater than 7. Later, between 30 and 40 min, the central coordinates are(x = 0.4366 ± 0.003, y = 0.4012 ± 0.003), which had an SDCM value higher than 7, and had a more discrete color placement; it does not meet the requirements of the national standard GBT24823-2016 general lighting LED module performance.

Synthesis,characterization and photoluminescent properties of Eu(Ⅲ)complexes with 5-hydroxy-2-hydroxymethyl-4H-4-pyranone and N,N’-donor heterocyclic coligands

In present work,five novel europium complexes[Eu(L)3·Phen(2),Eu(L)3·Bipy(3),Eu(L)3·Neo(4),Eu(L)3·Biq(5)and Eu(L)3·Batho(6)]were synthesized,derived from[Eu(L)3·2 H_(2)O](1)complex by using ligand(HL)5-hydroxy-2-(hydroxymethyl)-4 H-pyran-4-one and coligands 1,10-phenanthroline,bipyridine,neocuproine,2,2’-biquinoline and bathophenanthroline.In order to seek excellent photoluminescent properties,coligands were introduced in the complexes to form a rigid conjugated system,thus enhancing luminescence properties of complexes.The synthesized complexes reveal four narrow characteristic emission lines of Eu(III)consistent with ^(5)D0→^(7)FJ transitions,where J=0,1,2 and 3 at about 580,595,614 and 650 nm,respectively.The ^(5)D0→^(7)F_(2) transition is responsible for strong red luminescence.Color coordinate diagram also indicates that x,y coordinates lie in deep red region.Thermal data are in favour of high thermal stability of synthesized compounds.Owing to their high thermal stability and strong red luminescence,these complexes might be used in fabrication of optoelectronic devices.

Synthesis and spectroscopic studies of Zn4B6O13 and Eu/Tb single-doped Zn4B6O13 phosphors

In this study, Zn4B6O13, Eu-and Tb-doped Zn4B6O13 phosphors were prepared by conventional solid state reaction method and the samples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and photoluminescence spectroscopy（PL）. The doped rare-earth ions had little influence on the crystal structure of Zn4B6O13, but obviously affected the morphology of Zn4B6O13 particles. The PL results indicated that the 5% Eu-doped sample and 1% Tb-doped sample had the highest intensity in their respective different concentrations doped samples. The CIE chromaticity coordinates indicated that Zn4B6O13, Zn4B6O13：Eu and Zn4B6O13：Tb showed the three basic colors of blue, red and green, respectively. Evidently, the white light could appear only at appropriate intensity of blue, red and green components.