Efficient blue-light-excitable copper(Ⅰ) coordination network phosphors for high-performance white LEDs

The blue-light-excitable phosphors play a crucial role in the high-performance white LEDs. Here, we report on two new Cu(Ⅰ) coordination network materials as yellow-emitting phosphors prepared by suitably expanded π-conjugated triazole ligands. Upon blue-light irradiation, these complexes exhibit efficient solid-state emission and enhanced photostability. Through incorporating the yellow phosphor and a commercial blue-green powder(BaSi_(2)N_(2)O_(2):Eu^(2+)) with a blue LED chip, the phosphor-converted LED devices display remarkable white emission properties. The experimental results demonstrate that the Cu(Ⅰ)coordination network materials function as promising blue-light excitable phosphors with great application potential for full-spectrum white LEDs.

Luminescence properties of Pr^(3+) and Bi^(3+) co-doped NaCaTiNbO_6 phosphor for red-LEDs

This paper investigates the photoluminescence properties of NaCaTiNbO6：Pr^3＋ and NaCaTiNbO6：Pr^3＋,Bi^3＋ phosphors. NaCaTiNbO6：Pr^3＋ and NaCaTiNbO6：Pr^3＋,Bi^3＋ powder were synthesized successfully by solid state reaction method. Phase purity was checked using X-ray powder diffractometry（XRD）. The excitation and emission spectra were recorded to elucidate the photoluminescence properties of NaCaTiNbO6：Pr^3＋ and NaCaTiNbO6：Pr^3＋,Bi^3＋. Furthermore,fluorescence lifetime measurements were performed. The excitation spectra of NaCaTiNbO6：Pr^3＋ show a main band centered at around 357 nm.The luminescence spectra of NaCaTiNbO6：Pr^3＋ exhibit a red emission peak at 615 nm from the ^1 D2→^3 H4 transition of Pr^3＋ ions. With the introduction of the Bi^3＋ ion into NaCaTiNbO6：Pr^3＋, the luminescence intensity is enhanced nearly two times. Meanwhile,the absorption band edge of NaCaTiNbO6：Pr^3＋ is shifted from 380 to 420 nm. Thus, this study shows that the red phosphor NaCaTiNbO6：Pr^3＋ incorporated with Bi^3＋ is advantageous for light-emitting diode applications.

Combustion synthesis of YAG:Ce phosphors via the thermite reaction of aluminum

Cerium-doped yttrium aluminum garnet（YAG：Ce） as a yellow phosphor for white light-emitting diodes（LEDs） was synthesized via a facile combustion method using Y2 O3, CeO2, Al2 O3, Al,and NaClO4 as raw materials. The combustion synthesis approach utilizes the strong exothermic oxidation of aluminum to realize a self-sustaining reaction. In this study, we investigated the effects of the ratios of Al2 O3 to AI,fluxes, and coprecipitated materials as raw materials on the luminescence properties of the synthesized YAG：Ce phosphors. When the amount of Al2 O3 x is varied, the combustion reaction proceeds at x ≤ 1.8,with x = 1.725 being the optimum condition for producing a high-performance product. When 5 wt%BaF2 is added, the luminescence intensity is significantly improved owing to a decrease of YAP（YAlO3）formation with improved uniformity. However, the addition of CaF2 and NaF does not improve the luminescence properties. To suppress the segregation of CeO2, we used the coprecipitated material Y2 O3-CeO2 as a raw material. Unlike with separate addition of Y2 O3 and CeO2, Ce ions are uniformly distributed in the coprecipitated material, resulting in improved luminescence properties. The combination of BaF2 and coprecipitated material significantly improves the internal quantum efficiency to83.0%, which is close to that of commercial phosphors.

Immobilization of lead in anthropogenic contaminated soils using phosphates with/without oxalic acid

Understanding the effects of oxalic acid（OA） on the immobilization of Pb（Ⅱ） in contaminated soils by phosphate materials, has considerable benefits for risk assessment and remediation strategies for the soil. A series of phosphate amendments with/without oxalic acid were applied to two anthropogenic contaminated soils. We investigated the immobilization of Pb（Ⅱ） by KH2PO4, phosphate rock（PR）, activated phosphate rock（APR） and synthetic hydroxyapatite（HAP） at different phosphate：Pb（P：Pb） molar ratios（0, 0.6, 2.0 and 4.0） in the presence/absence of 50 mmol oxalic acid/kg soil, respectively. The effects of treatments were evaluated using single extraction with deionized water or Ca Cl2, Community Bureau of Reference（BCR） sequential extraction and toxicity characteristic leaching procedure（TCLP）methods. Our results showed that the concentration of water extractable, exchangeable and TCLP-Pb all decreased with incubation time. The concentration of water-extractable Pb after120 days was reduced by 100% when soils were amended with APR, HAP and HAP ＋ OA, and the TCLP-Pb was 〈5 mg/L for the red soil at P：Pb molar ratio 4.0. Water-soluble Pb could not be detected and the TCLP-Pb was 〈5 mg/L at all treatments applied to the yellow-brown soil. BCR results indicated that APR was most effective, although a slight enhancement of water-soluble phosphate was detected at the P：Pb molar ratio 4.0 at the beginning of incubation. Oxalic acid activated phosphates, and so mixing insoluble phosphates with oxalic acid may be a useful strategy to improve their effectiveness in reducing Pb bioavailability.