Red-emitting Eu3 Research Articles

A white-light-emitting LnMOF with color properties improved via Eu3+ doping: an alternative approach to a rational design for solid-state lighting

The intrinsic white-light-emitting properties of a lanthanide metal-organic framework that approach requirements for solid-state lighting are easily improved by incorporating minute quantities of red-emitting Eu(3+) into the host framework by virtue of the isostructural character of the La(3+) and Eu(3+) compounds and efficient sensitization of ligands toward Eu(3+) ions.

Photo-luminescent properties of a green or red emitting Tb3+ or Eu3+ doped calcium magnesium silicate phosphors

This study describes green-emitting Tb3+ or red-emitting Eu3+ doped calcium magnesium silicate phosphors by ultraviolet excitation at 335nm. The rare earth activated amorphous calcium silicate was prepared by a solution–combustion process at 600°C for 5–10min. The Ca2MgSi2O7 prepared using urea and ammonium nitrate has a tetragonal crystal structure. The resulting Tb3+-doped phosphor emitted green light centered at 544nm. The optimum excitation wavelength within the range 300–400nm was 335nm. The intensity and emitting wavelength of the Eu3+ doped samples can be controlled by annealing in a reducing or oxidizing environment, allowing light to be emitted as green or red. When the reducing environment is optimized, the emission spectrum of Ca2MgSi2O7:Eu2+ is a broad band at 497nm.

Synthesis, structure and photoluminescence properties of tetragonal tungsten bronze-type Eu3+-doped K2LaNb5O15 niobate phosphor

A series of red-emitting Eu3+-doped K2LaNb5O15 niobate phosphors with tetragonal tungsten bronze-type structure were synthesized by the solid state reaction method. The structure of new tungsten bronze-type K2EuNb5O15 was identified by Rietveld refinements to crystallize in the tetragonal space group P4bm, which is isostructural to K2LaNb5O15. The relative intensity of the emission from both 5D0→7F2 and 5D0→7F1 increases with increasing Eu3+ ion concentration. The quenching mechanism of the K2La1−xNb5O15:xEu system was investigated in detail. The relationship between Photoluminescence properties and the TTB-type structure was discussed. The quantum efficiency of K2EuNb5O15 excited under near-UV light (399nm) is 132% of that of commercial Y2O3:Eu3+ (394nm). The results demonstrated K2EuNb5O15 phosphor as a potential candidate for white light emitting diode pumped by near-UV or blue chip.

High quantum efficiency red-emission tungstate based phosphor Sr(La1−xEux)2Mg2W2O12 for WLEDs application

A series of red-emitting Eu3+-doped phosphors SrLa2Mg2W2O12 were successfully prepared by the solid state reaction and their luminescence properties were investigated in detail. Under 464 nm light excitation, the emission intensity at 613 nm increased with the Eu3+ ion concentration rising, and the quenching effect did not appear until the Eu3+ ion concentration reached 25%, and the critical distance was calculated to be 7.74 Å. The emission intensity of Sr(La0.75Eu0.25)2Mg2W2O12 is approximately three times higher than that of the commercial red phosphor Y2O3:Eu3+ under the blue light, meanwhile, the quantum efficiency of Sr(La0.75Eu0.25)2Mg2W2O12 is about two times higher than that of Y2O3:Eu3+. The Commission Internationale de l′Eclairage chromaticity coordinate of Sr(La0.75Eu0.25)2Mg2W2O12 is (x=0.660, y=0.340), which is closed to the standard of NTSC (x=0.670, y=0.330). The results indicate that Sr(La1−xEux)2Mg2W2O12 could be a potential red phosphor in fabrication of blue chips WLEDs.

Photophysical properties of [Ir(tpy)2]3+-doped silica nanoparticles and synthesis of a colour-tunable material based on an Ir(core)–Eu(shell) derivative

In this study, we report the synthesis and characterization of phosphorescent silica nanoparticles doped with the blue-greenish emitting Ir-tpy complex [Ir(tpy)2]X3 (tpy = 2,2′:6′,2′′-terpyridine; X = PF6− or NO3−). Depending on the type of counterion and the solubility of the complex, three different kinds of Ir(tpy)-doped silica nanoparticles were prepared by the Stober, water-in-oil and direct micelle synthetic approaches. The materials prepared through the Stober and the water-in-oil approaches showed enhanced photochemical stability and higher luminescence efficiency compared to the free Ir-tpy complex. In these cases, the silica matrix hampers the diffusion of O2 and restrains the mobility of the complexes resulting in a decrease of the vibration relaxation and restraining the nonradiative decay. Conversely, for the material prepared by the direct micelle method, in which the structure of silica shows some degree of mesoporosity, the luminescence properties of the Ir-tpy complex remained almost unchanged after silica encapsulation. Additionally, the nanoparticles prepared by the Stober method were chosen to functionalize their surface with a red-emitting Eu(hfac)3-alkoxysilane derivative leading to multicoloured luminescent silica nanoparticles in which the colour of the emission could be tuned by changing the excitation wavelength and where an Ir → Eu energy transfer was evidenced.

Luminescence and structure of a novel red-emitting phosphor Eu3+-doped tellurate garnet Li3Y3Te2O12

Eu3+-doped red-emitting phosphors of tellurate garnets Li3Y3−3xEu3xTe2O12 (x=0.05–1) were synthesized by the solid-state reaction. The phase purity of the as-prepared phosphor was verified by X-ray diffraction (XRD) studies. The photoluminescence excitation and emission spectra, the fluorescence decay curves, the dependence of luminescence intensity on doping level and CIE coordinates were investigated. The phosphor can be efficiently excited by near UV and blue light to realize an intense narrow red emission line (611nm) corresponding to the forced electric dipole transition 5D0→7F2 of Eu3+ ions. The potential application as a red-emitting phosphor for solid state lighting was evaluated in comparison with Eu3+-doped Y2O2S and aluminum garnet phosphors. The phosphor can be suggested to be a potential red-emitting candidate for the application in white LEDs under the irradiation of near-UV or blue chips.

A study of the luminescence in near UV-pumped red-emitting novel Eu3+-doped Ba3Ca3(PO4)4 phosphors for white light emitting diodes

Rare-earth ions doped inorganic luminescent materials (phosphors) in nanodimensions find widespread scientific and industrial applications. This paper report a novel red-emitting Eu3+ doped Ba3Ca3(PO4)4 phosphors in nanodimensions were synthesized via one-step conventional solid state reaction method for first time at high temperature in air atmosphere. The morphology and nanostructures of synthesized phosphors were determined by powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM) and Energy-dispersive X-ray spectroscopy (EDS). The XRD observation reveals that the undoped and Eu3+ doped Ba3Ca3(PO4)4 phosphors are in single crystalline phase with the sizes of 40–65nm. FE-SEM image indicated the phosphor is composed of nearly spherical particles and rod like structures with several nanometer sizes. The presence of orthophosphates in Ba3Ca3(PO4)4 phosphor was identified by Fourier transform infrared (FT-IR) analysis and the thermal stability was studied by Differential scanning calorimetry (DSC). Diffuse reflectance spectra (DRS) evidenced the incorporated Eu3+ ions in host material. In addition, the bandgap of these samples were estimated from the Mubelka–Munk function. The room-temperature photoluminescence spectra show the characteristic red fluorescence originating from intra 4f 5D0→7F2 (616nm) transition of Eu3+ is observed by introducing Eu3+ ions in Ba3Ca3(PO4)4 phosphors. The calculated color coordinates are lies in the orange–red region. Therefore, these obtained results suggest that the prepared phosphors exhibit great potential for use as red-component for near ultraviolet white light emitting diodes (NUV WLEDs).

Synthesis, Characterization, and Luminescent Properties of a Red-Emitting Europium Complex

a fluorine functionalized 1,10-phenanthroline ligand, 3-ethyl-2-(2-fluorophenyl) imidazo[4,5-f]1,10-phenanthroline(EFPIP) and the corresponding red-emitting Eu(ΙΙΙ) complex Eu(DBM)3(EFPIP) (DBM = dibenzoylmethanate) was synthesized and the photophysical properties and electroluminescent(EL) performances were researched. When Eu(DBM)3(EFPIP) was used as emitting material in organic devices, the maximum efficiency and luminance of red emission achieved from the EL device with the configuration of ITO/m-MTDATA (30 nm)/NPB (20 nm)/ x wt% Eu(DBM)3(EFPIP) doped in CBP (30 nm)/Bphen (20 nm)/Alq3 (20 nm)/LiF (0.8 nm)/Al were 3.6 cd/A and 563 cd/m2, respectively. Compared with the previously reported devices based on methyl or chlorine substitute Eu(ΙΙΙ) complexes, the EL performances of the device using Eu(DBM)3(EFPIP) as an emitter was significantly enhanced due to the introduction of fluorine.

Fluorescent properties of a green- to red-emitting Eu3+, Tb3+ codoped amorphous calcium silicate phosphor

A Eu3+, Tb3+ codoped amorphous calcium silicate phosphor was prepared by heating a Eu3+, Tb3+ codoped calcium silicate hydrate phosphor formed by liquid-phase reaction for 30min at 900°C. The excitation peak wavelength of the resulting phosphor was 379nm and the emission peak wavelengths were at 542nm, attributed to the 5D4→7F5 transition of Tb3+, and at 613mm, attributed to the 5D0→7F1 transition of Eu3+. The intensity ratio of the two peaks could be freely controlled by varying the Eu/Tb atomic ratio of the Eu3+, Tb3+ codoped amorphous calcium silicate phosphor, allowing light to be emitted over a wide range from green to red. It was clarified that electron transfer from Tb3+ to Eu3+ is occurring.

Synthesis and photoluminescence properties of the high-brightness Eu3+-doped Sr3Y(PO4)3 red phosphors

A series of red-emitting phosphors Eu3+-doped Sr3Y(PO4)3 have been successfully synthesized by conventional solid-state reaction, and its photoluminescence properties have been investigated. The excitation spectra reveal strong excitation bands at 392nm, which match well with the popular emissions from near-UV light-emitting diode chips. The emission spectra of Sr3Y(PO4)3:Eu3+ phosphors exhibit peaks associated with the 5D0→7FJ (J=0, 1, 2, 3, 4) transitions of Eu3+ and have dominating emission peak at 612nm under 392nm excitation. The integral intensity of the emission spectra of Sr3Y0.94(PO4)3:0.06Eu3+ phosphors excited at 392nm is about 3.4 times higher than that of Y2O3:Eu3+ commercial red phosphor. The Commission Internationale de l’Eclairage chromaticity coordinates, the quantum efficiencies and decay times of the phosphors excited under 392nm are also investigated. The experimental results indicate that the Eu3+-doped Sr3Y(PO4)3 phosphors are promising red-emitting phosphors pumped by near-UV light.

Luminescent properties of green- or red-emitting Eu 2+-doped Sr 3Al 2O 6 for LED

Eu 2+-doped Sr 3Al 2O 6 (Sr 3− x Eu x Al 2O 6) was synthesized by a solid-state reaction under either H 2 and N 2 atmosphere or CO atmosphere. When H 2 was used as the reducing agent, the phosphor exhibited green emission under near UV excitation, while CO was used as the reducing agent, the phosphor mainly showed red emission under blue light excitation. Both emissions belong to the d– f transition of Eu 2+ ion. The relationship between the emission wavelengths and the occupation of Eu 2+ at different crystallographic sites was studied. The preferential substitution of Eu 2+ into different Sr 2+ cites at different reaction periods and the substitution rates under different atmospheres were discussed. Finally, green-emitting and red-emitting LEDs were fabricated by coating the phosphor onto near UV- or blue-emitting InGaN chips.

Oxygen sensing nanofibers doped with red-emitting Eu(III) complex: Synthesis, characterization, mechanism, and sensing performance

In this paper, we synthesize a novel diamine ligand of PIP and its corresponding Eu(III) complex of Eu(DBM) 3PIP, where PIP = 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline, and DBM = 1,3-diphenyl-propane-1,3-dione. The UV–Vis absorption spectra, low temperature phosphorescence spectra, energy transfer mechanism, excited state lifetime of Eu(DBM) 3PIP, as well as its photoluminescence spectra, are investigated in detail. Data suggest that the emission of Eu(DBM) 3PIP is quenchable by molecular oxygen due to the back-energy transfer process. By doping Eu(DBM) 3PIP into a polymer matrix of poly(vinylpyrrolidone) (PVP), the oxygen sensing performance of the resulted nanofibrous membrane is investigated. Finally, the 0.6 wt% doped sample exhibits a linear response towards molecular oxygen, with a sensitivity of 3.5 and response/recovery time of 15 s/24 s.

Effect of substitution of nitrogen ions to red-emitting Sr 3B 2O 6−3/2 xN x:Eu 2+ oxy-nitride phosphor for the application to white LED

The luminescence properties of orange–red-emitting Eu 2+ activated Sr 3B 2O 6−3/2 x N x were optimized for application to blue/near UV light-emitting diodes (LEDs). Sr 3B 2O 6−3/2 x N x :Eu 2+ phosphor showed broad orange–red emission peaking at 600–650 nm under blue and n-UV excitations of 450 and 360 nm, respectively; the emission peak of phosphor was affected by nitrogen ion substitution. Boron nitride raw materials affect luminescence properties of phosphor; a small amount of BN reacts as a flux for synthesis of Sr 3B 2O 6 and a large amount of BN helps Sr 3B 2O 6−3/2 x N x :Eu 2+ phosphor to have longer-wavelength emission peak. A 447 nm-emitting blue LED-pumped white LED with a mixture of Sr 3B 2O 6−3/2 x N x :Eu 2+ ( x=1) and Ba 2SiO 4:Eu 2+ green-emitting phosphor was fabricated; it is observed that it showed color coordinates of (0.3648, 0.3605) and CRI value of 96.

Preparation and fluorescence properties of novel red-emitting Eu3+-activated amorphous alkaline earth silicate phosphors

Abstract This study reports the synthesis of novel red-emitting Eu 3+ -activated amorphous alkaline earth silicate phosphors with high emission intensities. Eu 3+ -activated barium (strontium) silicate hydrate phosphors were synthesized using a liquid phase reaction and then heated at 850 °C for 0.5 h to form amorphous barium (strontium) silicate phosphors. These amorphous phosphors emitted in the red region following near-UV (395 nm) irradiation. The internal quantum efficiencies of the Eu 3+ -activated amorphous barium silicate phosphor and strontium silicate phosphor were 56% and 60%, respectively, even though these phosphors were in the amorphous state.

High color rendering white light-emitting-diode illuminator using the red-emitting Eu^2+-activated CaZnOS phosphors excited by blue LED

A red phosphor CaZnOS:Eu(2+) was synthesized by solid state reaction and has been evaluated as a candidate for white LEDs. For this material, the XRD, PL, PL excitation (PLE) and diffuse reflection spectra have also been investigated. CaZnOS:Eu(2+) reveals a broad absorption band and good color purity. By utilizing a mixture of red-emitting CaZnOS:Eu(2+), green-emitting (Ba,Sr)(2)SiO(4):Eu(2+) and yellow-emitting Y(3)Al(5)O(12):Ce(3+) as light converters, an intense white InGaN-based blue-LED (~460 nm) was fabricated to exhibit a high color-rendering index Ra of 85 at a correlated color temperature of 4870 K. Based on the results, we are currently evaluating the potential application of CaZnOS:Eu(2+) as a red-emitting blue-chip convertible phosphor.

Enhanced luminescence by charge compensation in red-emitting Eu 3+-activated Ca 3Sr 3(VO 4) 4

The effects of charge compensation on the luminescence behavior of a red-emitting phosphor, Ca 3Sr 3(VO 4) 4:Eu 3+, were investigated. It has been observed that charge compensated by monovalent ions, especially Na +, shows greatly enhanced red emission under ultraviolet excitation. It is found that Na 2CO 3 addition acts as a fluxing agent and plays a role in charge compensation, which clearly improves the emission intensity of Eu 3+-activated Ca 3Sr 3(VO 4) 4. Enhanced emission intensity of the corresponding charge compensated phosphors under ultraviolet radiation may find application in the production of red phosphors for white light-emitting diodes.

Preparation and fluorescence property of red-emitting Eu 3+-activated amorphous calcium silicate phosphor

This paper describes the energy efficient synthesis of a red-emitting Eu 3+-activated amorphous calcium silicate phosphor produced by heating a Eu 3+-activated calcium silicate hydrate phosphor. Concentration quenching of the Eu 3+-activated calcium silicate hydrate phosphor was not observed and the emission intensity did not decrease up to a Eu/(Ca+Eu) atomic ratio of 0.46. Heating of the Eu 3+-activated calcium silicate hydrate (Eu/(Ca+Eu) atomic ratio = 0.32) phosphor produced an amorphous Eu 3+-activated calcium silicate phosphor, which had a maximum emission intensity at 870 °C and emitted in the red under near-ultraviolet irradiation (395 nm). The emission intensity of the Eu 3+-activated amorphous calcium silicate phosphor was about half that of a commercial BaMgAl 10O 17:Eu 2+ phosphor, and shows great potential for application in white light-emitting diodes.

Synthesis and luminescent properties of a new red-emitting phosphor for solid-state lighting: Eu 0.1Gd xLa 1.9−xTeO 6 (0.02⩽ x⩽0.1)

The photoluminescence (PL) emission and excitation behavior of red-emitting Eu 0.1Gd x La 1.9− x TeO 6 (0.02⩽ x⩽0.1) powder phosphors is reported. Three dominant bands centered at 395, 466 and 534 nm characterized the excitation spectrum. Under the excitation of 395 nm UV light, the emission spectrum exhibits an intense peak centered at 616 nm corresponding to the 5D 0→ 7F 2 transition of Eu 3+. Because the f→f transitions are located in the wavelength range of blue or near-UV range, optimized phosphor, Eu 0.10Gd 0.08La 1.82TeO 6, is a promising material for solid-state lighting based on GaN LEDs applications.

Novel Eu3+‐Doped Red‐Emitting Phosphor Gd2Mo3O9 for White‐Light‐Emitting‐Diodes (WLEDs) Application.

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Elaboration of nanostructured Eu3+-doped Gd2O3 phosphor fine spherical powders using polyol-mediated synthesis

Red-emitting Eu3+-doped Gd2O3 spherical powders were directly precipitated using a polyol method. The as-synthesized powders consist of agglomerates with a spherical shape and a size ranging between 0.4 and 0.6 μm. Each agglomerate is nanostructured and consists of a packing of nanocrystallites (3–5 nm) of a bcc oxide phase whose luminescence presents original features in comparison with bulk materials. The powders were further calcinated and the size of both crystallites and agglomerates, the crystalline structure and the luminescence were studied as a function of the annealing temperature. For temperatures lower than 900 °C, the samples obtained are highly crystalline and possess the classical Eu3+ red luminescence. For optimized temperature, the morphology of the particles can be preserved leading to spherical, dense, luminescent and almost monodisperse oxide powders, 0.5 μm in size.