Menglian Gong

A novel 2-positional linked carbazole based β-diketone with methoxyl in the 7-position (EMOCTFBD), and its europium(III) ternary complex Eu(EMOCTFBD)₃phen were synthesized via a dexterously designed indirect routine, where EMOCTFBD was 1-(9-ethyl-7-methoxyl-9H-carbazol-2-yl)-4,4,4-trifluorobutane-1,3-dione and phen was 1,10-phenanthroline. Eu(EMOCTFBD)₃phen shows high thermal stability. The introduction of a methoxyl in the 7-position of the carbazole ring remarkably enhanced the excitation band intensity in the blue region, and the complex exhibited intense red emission under blue-light excitation. The lowest triplet state energy was measured and suggests the photoluminescence process as a ligand-sensitized luminescence process (antenna effect). A bright red-emitting diode was fabricated by coating the complex phosphor onto a ∼460 nm-emitting InGaN chip. All the results indicate that Eu(EMOCTFBD)₃phen is an interesting red-emitting material excited by blue light, and therefore may be applied in many fields without UV radiation.

An efficient green phosphor, Ba ₂ MgSi ₂ O ₇ :Eu ²⁺ , was prepared by a solid‐state reaction. Excited by 350–420 nm light, the phosphor shows a strong and broad emission band centering at 505 nm. The concentration quenching mechanism was verified to be a dipole–dipole interaction and the critical energy‐transfer distance was confirmed as around 20 Å by both the calculated crystal structure method and the experimental spectral method. This phosphor shows a low thermal‐quenching property with an activation energy of 0.677 eV. Light‐emitting diodes (LEDs) were fabricated with Ba ₂ MgSi ₂ O ₇ :0.07Eu ²⁺ and 395‐nm‐emitting InGaN chips and exhibited strong wide‐band green emission and relatively stable current‐dependent electroluminescence properties, indicating that this phosphor is a promising candidate as a green component for the fabrication of white LEDs.

Nanostructured tetragonal LaVO₄ with sheaf-like and prickly spherical morphologies has been hydrothermally synthesized with the assistance of ethylenediaminetetraacetic acid (EDTA). In the hydrothermal process, EDTA not only acts as a chelating reagent to facilitate the formation of t-LaVO₄, but also acts as a surface capping agent to adhere to the newly created surface and to promote the crystal splitting. t-LaVO₄ nanostructures with different morphologies can be achieved by adjusting the molar ratio of EDTA/La³⁺ , the concentration of La³⁺ , and the total volume of the reaction mixture, which result in the change of the crystal growth rate. Nanostructured Eu³⁺ -doped t-LaVO₄ was also synthesized and showed intense red emission under near UV-light excitation.

Two novel carbazole-based β-diketones with 2- or 2,7-substituted groups in the carbazole ring, 2-(4′4′4′-trifluoro-1′3′-dioxobutyl)-carbazole (2-TFDBC) and 2,7-bis(4′4′4′-trifluoro-1′’3′-dioxobutyl)-carbazole (2,7-BTFDBC), and their europium(III) ternary complexes Eu(2-TFDBC)₃phen and Eu₂(2,7-BTFDBC)₃(phen)₂ were synthesized via a dexterously designed routine, where phen is 1,10-phenanthroline. The Eu(III) complexes were characterized by elementary analysis, IR and UV−visible absorption spectroscopy, thermogravimetric analysis (TGA), and photoluminescence (PL) measurements. TGA shows that the decomposition temperatures of the complexes are 361.4 and 367.3 °C, respectively. PL measurement results indicated that suitably expanded π-conjugation in the complex molecules makes the excitation band redshift to the visible region, and both the Eu(III) complexes exhibit intense red emission under blue-light excitation. The triplet state energy levels of 2-TFDBC and 2,7-BTFDBC in the complexes are higher than that of the lowest excited level of Eu³⁺ ion, ⁵D₀, so the photoluminescence mechanism of the Eu(III) complexes was proposed as a ligand-sensitized luminescence process. All of the results indicate that Eu(2-TFDBC)₃phen and Eu₂(2,7-BTFDBC)₃(phen)₂ are promising candidates as visible-light excitable red phosphor for luminescence applications.

A dinuclear Eu(III) organic complex, , was synthesized, where BTFBDEC is 3,6-bis(4,4,4-trifluoro-1,3-butyldiketone)-9-ethyl-carbazole and phen is 1,10-phenanthroline. exhibits high thermal stability, excellent photoluminescence properties, appropriate CIE chromaticity coordinates for red and good quantum yield under near-UV light excitation. An intense red-emitting light-emitting diode (LED) was fabricated by combining with an emitting InGaN chip. The results indicate that is a good candidate as a red component for the fabrication of white LEDs.