Red-emitting Eu3 Research Articles

High-brightness red-emitting Eu3+-activated Ca2LuZr2Al3O12 garnet phosphors with excellent thermal stability for near-UV-pumped white LEDs

In this work, a group of red-emitting Ca2LuZr2Al3O12:xEu3+ (x = 20%, 30%, 40%, 50%, 60%, 70% and 80%) phosphors have been prepared and their luminescence properties are studied. X-ray diffraction, excitation and emission spectra, fluorescence decay curves, CIE color coordinates, and temperature-dependent photoluminescence spectra are used to characterize these samples. All these Ca2LuZr2Al3O12:Eu3+ compounds exhibit intense red luminescence peaking at around 618 nm under 394 nm excitation. The critical concentration of Eu3+ ion is 50 mol%, and the concentration quenching mechanism has been discussed and analyzed. The CIE color coordinates of the optimal Ca2LuZr2Al3O12:50%Eu3+ sample are (0.6506, 0.3487), and it has a high color purity of 90.7%. Importantly, the emission intensity of Ca2LuZr2Al3O12:50%Eu3+ is about 1.67 times higher compared to the commercial Y2O3:Eu3+ red phosphor. What's more, Ca2LuZr2Al3O12:50%Eu3+ phosphor also displays excellent resistance to thermal quenching at elevated temperature; only 14% emission intensity is lost at 150 °C.

Red-emitting Eu3+ activated LaSr2AlO5 phosphor for wLEDs: Crystal structure, photoluminescence, thermal stability, Judd-Ofelt calculation and band-gap analyses

Red-emitting La1-xSr2AlO5:xEu3+ (x = 0.01–0.06) phosphors have been synthesized via gel combustion (GC) approach and their structure and luminescent characteristics were analyzed in detail. The tetragonal crystal structure (I4/mcm space group) of all generated La1-xSr2AlO5:xEu3+ (x = 0.01–0.06) phosphors have been established by X-ray diffraction and rietveld analysis. The shape and size of the phosphor has been examined using transmission electron microscopy (TEM) and the estimated crystallite size was found to be 32–65 nm. Energy Dispersive X-ray (EDX) analysis confirmed the chemical composition of the synthesized materials. The diffuse reflectance spectra (DRS) were used to compute the band gap energies (Eg) of the samples which emerged to be in region of 5.373–6.009 eV. The Eu3+ activated LaSr2AlO5 phosphors produce red emissions at 579, 592, 614, 656 and 708 nm, when excited at 395 nm. These emission bands are caused by 5D0→7FJ (J = 0, 1, 2, 3, 4) electronic transitions of Eu3+ ion. The Judd-Ofelt theory further supports the performance of LaSr2AlO5:Eu3+ phosphors as a red emitting substance with high branching ratio corresponding to 5D0→7F2 transition from Eu3+ center present in the low symmetry site. Computed chromaticity coordinates (x, y) indicate a high degree of color purity in the phosphors, providing additional evidence for the presence of red emission. Temperature dependent emission (PL) spectra revealed good thermal stability of the synthesized nanophosphors with activation energy (Ea) of 0.1384 eV.

Structural, optical and photoluminescence properties of BaLa2ZnO5: Eu3+ phosphor: A prospective red-emitting phosphor for LED applications

Herein, we report the synthesis of red-emitting Eu3+-activated BaLa2ZnO5 phosphors using a high-temperature solid-state reaction technique. The phase confirmation and crystal structure were established through X-ray powder diffraction patterns. Density-functional theory calculations revealed an indirect bandgap in the material. The bandgaps of both undoped and doped BaLa2ZnO5 phosphors were analyzed using diffuse reflectance spectra. The influence of Eu3+ doping on the bandgap was confirmed by applying the Kubelka-Munk function to the diffuse reflectance spectra. The effects of doping on the surface morphology and elemental composition were investigated through field emission scanning electron microscopy and energy-dispersive spectroscopy, respectively. Additionally, X-ray photoelectron spectroscopic studies were conducted to analyze the electronic structure, chemical states and impact of doping on the crystal structure. Using near ultraviolet excitation at 329 nm, the synthesized phosphor exhibited strong red emission attributed to various 5D0 → 7FJ transitions. Concentration quenching phenomena were observed due to dipole-dipole interactions. Judd-Ofelt analysis was performed to elucidate the coordination nature of the doping element in the host lattice. Excellent thermal stability was observed with an activation energy of 0.64 eV for discharging via lattice vibrations. The better color purity (98–99.3 %) and stable Commission Internationale de l’Elcairage coordinates in the red region of the gamut suggest that the prepared phosphor material holds potential as an efficient candidate for ultra violet and blue light-emitting diode chips, as well as an efficient component in the fabrication of white light-emitting diodes.

Mechanoluminescence and photoluminescence properties of Eu3+ -activated SrGa2 O4 phosphors.

Red-emitting Eu3+ activated SrGa2 O4 phosphors were synthesized using a conventional solid-state reaction method. The structural, optical, and luminescence properties were systematically investigated. The synthesized phosphors are single phase with a monoclinic structure. There are no significant changes in the phase and the crystal structure of the host matrix after incorporating Eu3+ ions. The undoped and Eu3+ doped SrGa2 O4 phosphors exhibited good mechanoluminescence (ML) emission without any irradiation with ultraviolet (UV) or gamma rays. Eu3+ -activated SrGa2 O4 phosphors have prominent red emission attributed to 5 D0 → 7 F2 forced electric dipole transition excited at 395 nm. The colour coordinates and purity of the SrGa2 O4 : 0.08 Eu3+ phosphor were calculated to be (0.6102, 0.3810) and 97.6%, respectively. The quantum efficiency is 12.68%, and was better than that of commercially available red phosphors. The ML and photoluminescence studies revealed that the synthesized phosphors can act as potential candidates for stress sensors, UV or near-UV light-emitting diodes (NUV LEDs) and components of phosphor-converted white light-emitting diode (pc-WLED) applications.

Eu3+ activated non-crystalline BaTiO3 ultra-thin film phosphor with high purity, tailored red emission from n-UV excitation for WLEDs applications

As an alternative WLED red phosphor, BaTiO3 sol-gel based ultra-thin films were doped with various mol% of Eu3+ and annealed at 500 °C. The films were amorphous with short range ordered structure as seen via XRD and Raman analysis. Photoluminescence (PL) emission spectra enabled the determination of Eu3+ location asymmetry in the host via Judd-Ofelt (J-O) theory, from which Ω2=9.37×10−20cm2 and Ω4=1.55×10−20cm2 were derived, proving that the Eu3+ ions were non-centrosymmetrically located. This enhanced the Eu3+ 5D0 → 7F2 electric-dipole transition at 614.0 nm with the strongest emission from 30 mol% doping. 395 nm excited intense and narrow red spectral profiles which exhibited excellent colour coordinates (x = 0.657, y = 0.342), quantum efficiency (25.7% at a film thickness of ∼380 nm), and colour purity of (92.0%) whereby the red to orange ratio (R : O) enables colour tailoring with 5 mol% to 30 mol% Eu3+doping. This facilitates flexible control over the colour output, ensuring that it can be easily tailored to meet specific application requirements. The aforementioned results indicate that the red-emitting Eu3+ activated amorphous BaTiO3 ultra-thin film phosphors exhibit promising potential for application in n-UV excited WLEDs as a red phosphor with a branching ratio β0→2=81.43% making it a potential candidate for red laser materials too.

Simultaneous enhancement of red luminescence and thermal stability of a novel red phosphor: A Li+-Eu3+ co-occupied site strategy in BaAl2Ge2O8 lattices

The rapid development of phosphor-converted white light emitting diodes (pc-WLEDs) requires new red phosphors with efficient and thermally stable luminescence for high-quality warm-white lighting. However, it is still a challenge to discover red phosphors with facile synthesis, high internal quantum efficiency (IQE), excellent thermal stability and high color purity. Herein, a novel red-emitting Eu3+ activated barium dialuminum digermanate (BaAl2Ge2O8, BAGO) phosphor showing strong red emission at 610 nm was prepared. The IQE is improved from 32.91% to 78.84% by employing a charge compensation strategy. The lithium-ion co-doped BAGO:Eu3+ phosphor exhibits a nearly twofold increase in integral photoluminescence (PL) intensity and the high color purity reaches 94.17%. Impressively, the PL intensity of the BAGO:Eu3+,Li+ phosphor drops by only 2.6% at 150 °C of that at room temperature. Finally, the pc-WLED using the red BAGO:Eu3+,Li+ phosphor exhibits white light with the chromaticity coordinate of (0.3515, 0.3495), a high color-rendering index of 92 and a low correlated color temperature of 4746 K. All these results manifest that BAGO:Eu3+,Li+ phosphor is a suitable red phosphor for near-ultraviolet (NUV) chip-based pc-WLEDs.

A blue-emitting porous MOF incorporated with red-emitting Eu(III) ions for nitro compounds fluorescence sensing: Improving ratiometric selectivity and sensitivity by synergistic effect of a dendritic auxiliary ligand

Due to the high nitrogen oxidation valence and electron-deficient structure, organic nitro compounds are generally known as potential explosive which are also considered as environmental threat. Optical sensing is an attractive quantification method with simple operation procedure and limited requirement for equipment, but traditional optical sensing platforms for nitro compounds suffered from limited sensitivity and poor selectivity. To solve this problem, this work designed applied a ratiometric sensing platform. Here red-emitting Eu(III) was incorporated into a blue-emitting host bio-MOF-1. A dendritic auxiliary ligand (denoted as BBB) was adopted to stabilize the adduct between Eu(III) and TPA (2,4,6-trinitrophenol). By so doing, the blue emission intensity from bio-MOF-1 was increased, while the Eu3+ emission intensity was minimized. The sensing behavior upon auxiliary ligand BBB was compared to that upon a reference ligand (1,10-phenanthroline). The sensing mechanism was proved as an irreversible Eu(III) leak and coordination with TPA/BBB guaranteed by BBB steric hindrance. Finally, a linear working equation with improved sensitivity (by sixfold) and unique selectivity was observed.

Structure, properties and application of Eu3+ doped bismuth molybdate red-emitting phosphor synthesized by sol-gel method

In this work, red-emitting Eu3+ doped bismuth molybdate phosphors (BMO: Eu3+) were synthesized by a sol-gel method. The influences of calcination temperature on BMO: Eu3+ were investigated. The structure and properties of BMO: Eu3+ at different calcination temperatures were characterized by XRD, Raman, SEM, FT-IR and PL techniques respectively. The crystal structure and related parameters were obtained by a Rietveld method. The relationship between the luminescence performance and the crystal structure is analyzed in detail. Furthermore, the BMO: Eu3+ phosphors was applied to the preparation in luminescent films and LED devices. In addition, it was the first time that BMO: Eu3+ phosphors were applied to the detection of Fe3+, Cr2O72− and 4-Nitrophenol (4-NP). It is worth noting that it has good selectivity and sensitivity to 4-NP, Fe3+ and Cr2O72−, which can be used as luminescent sensors for detection. Among them, the LOD of 4-NP is as low as 2.32 μM.

Photoluminescence characteristics of a novel orange red-emitting Eu3+ doped K3Ca2(SO4)3F phosphor for W-LED

The present work reported the synthesis of Eu3+-activated K3Ca2(SO4)3F sulfate-based phosphors via a solid-state reaction method (SSR). The crystal structure of as-synthesized phosphor was studied by XRD analysis. The PL and PLE spectrum were investigated using photoluminescence spectroscopy. The PL excitation spectrum monitored at 616 nm shows sharp line excitation peaks at 395 nm,466 nm and 535 nm, attributes to 7F0→ 5L6,7F0→ 5D2, and 7F0→ 5D1 transitions respectively. The PL spectrum under UV excitation of 395 nm exhibits emission in the red region centered at 592 nm and 616 nm, corresponding to 5D0→ 7F1, and 5D0→ 7F2 transitions of Eu3+ ions in the host. The CIE coordinates confirm the emission in the orange-red region positioned at (0.6824, 0.3175) with color purity of 97.37% and CCT 3872.2 K. The obtained outcome reveals that the reported K3Ca2(SO4)3F: Eu3+ phosphor is the best candidate as UV excitable orange-red emitting phosphor for w-LEDs.

Novel Red-Emitting Eu3+-Doped Y2(WxMo1-xO4)3 Phosphor with High Conversion Efficiency for Lighting and Display Applications.

In this study, a series of trivalent europium-doped tungstate and molybdate samples were synthesized using an improved sol-gel and high-temperature solid-state reaction method. The samples had different W/Mo ratios and were calcined at various temperatures ranging from 800 to 1000 °C. The effects of these variables on the crystal structure and photoluminescence characteristics of the samples were investigated. It was found that a doping concentration of 50% for europium yielded the best quantum efficiency based on previous research. The crystal structures were found to be dependent on the W/Mo ratio and calcination temperature. Samples with x ≤ 0.5 had a monoclinic lattice structure that did not change with calcination temperature. Samples with x > 0.75 had a tetragonal structure that remained unchanged with calcination temperature. However, samples with x = 0.75 had their crystal structure solely dependent on the calcination temperature. At 800-900 °C, the crystal structure was tetragonal, while at 1000 °C, it was monoclinic. Photoluminescence behavior was found to correlate with crystal structure and grain size. The tetragonal structure had significantly higher internal quantum efficiency than the monoclinic structure, and smaller grain size had higher internal quantum efficiency than larger grain size. External quantum efficiency initially increased with increasing grain size and then decreased. The highest external quantum efficiency was observed at a calcination temperature of 900 °C. These findings provide insight into the factors affecting the crystal structure and photoluminescence behavior in trivalent europium-doped tungstate and molybdate systems.

Effects of Eu3+ concentration on the thermoluminescence properties of narrow-band red-emitting Eu3+: SrLaGaO4 phosphor

A series of Eu3+ doped SrLaGaO4 ceramic phosphors were successfully synthesized by the solid-state reaction method. The optical properties of (x at%) Eu: SrLaGaO4 samples with x = (0.1, 1, 3, 5, 10, 15, 20, 30) were investigated and analyzed. The room temperature emission spectra of xEu: SrLaGaO4 ceramic samples, under blue and UV excitation wavelengths, showed a maximum relative emission intensity at 620 nm, corresponding to the hypersensitive 5D0→7F2 transition, with a full width at half maximum (FWHM) of ∼7 nm, for a doping concentration with Eu3+ ions of 10 at% (x = 10). The asymmetry parameter (the ratio between the 5D0→7F2 and 5D0→7F1 transitions) and the critical distance between Eu3+ ions allowed to obtain a very good color purity of the red emission (88 %) for the 10Eu: SrLaGaO4 phosphor. The cross-relaxation and energy migration processes between Eu3+ ions in the 10Eu: SrLaGaO4 sample are negligible and do not contribute to the quenching of the 5D0 emitting level. From the investigation of the temperature-dependent luminescence intensity ratio (LIR) of the 5D0→7F2 and 5D0→7F1 transitions of the 10Eu: SrLaGaO4 sample in the range of 10–575 K, the relative sensitivity parameter (Sr) was found to be 0.4 % K−1 at 10 K and 0.45 % K−1 at 450 K. These results suggest that 10Eu: SLO phosphor is a versatile material that could be operated as a temperature sensor over a wide range of temperatures, as well as a narrow-band red-emitting phosphor for phosphor-converted white light-emitting diodes (pc-WLEDs).

Nanodiamond-promoted white light emission in Eu, Dy, and Cu-containing phosphate glass: quantitative analysis and colorimetric study.

A thorough analysis of glass containing Eu2 O3 and Dy2 O3 , or Eu2 O3 , Dy2 O3 , and CuO melted together with nanodiamond powder was pursued based on measurements of optical absorption, photoluminescence (PL) emission and excitation spectra, and colorimetry. Nanodiamond facilitated the stabilization of Cu+ and Eu2+ ions with blue-emitting characteristics that, along with yellow-emitting Dy3+ and red-emitting Eu3+ led to the white light-emitting glass. Novel intensity notations implemented in intensity-based spectral ratios, and difference intensity correlation analysis were proposed for the assessment of PL properties. The chromaticity and correlated colour temperature of the emission were ultimately investigated as a two-parametric problem based on: (1) the different ionic components; and (2) the various excitation wavelengths employed. The optical analysis approach adds to the characterization methods to further fundamental understanding and provide helpful analytical tools for designing materials for tunable white light-emitting devices.

High quantum yield of red-emitting Eu3+ doped nanophosphor based on monoclinic Y2O3

In the present article we report on the laser synthesis of Eu3+ doped nanophosphor with improved red color based on single-phase monoclinic Y2O3 and an experimentally measured quantum yield as high as 60% at λ = 395 nm excitation. HRTEM and SEM studies evidence the formation of nanoparticles with a spherical morphology, the average diameter of ca. 20 nm, and high crystallinity. We demonstrate that such a high quantum yield can be achieved by adding oxygen during laser synthesis in a combination with post-synthesis treatments in air at T = 750 °C. The thermal annealing effects in air and vacuum in the range of 250–750 °C on the morphology, structure, optical and photoluminescence properties of as-synthesized m-Y2O3:Eu3+ have been discussed. The obtained chromaticity coordinates (0.659, 0.332), high color purity (96%) and high absolute quantum yield indicate the possibility of using red nanophosphor based on monoclinic Y2O3:Eu3+ in numerous luminescence applications.

High quantum efficiency and excellent color purity of red-emitting Eu3+-heavily doped Gd(BO2)3-Y3BO6-GdBO3 phosphors for NUV-pumped WLED applications.

Eu3+-doped phosphors have been much attractive owing to their narrow-band red emission peak at 610-630 nm with high color purity; however, the weak and narrow absorption band in the NUV region limits their applications. Doping a higher amount of Eu3+ ions into a non-concentration quenching host could be key to enhancing the efficiency of the absorption value and emission intensity. Hence, the design of Eu3+-heavily doped phosphors with a suitable host lattice is key for applications. In this study, red-emitting Eu3+-doped Gd(BO2)3-Y3BO6-GdBO3 (GdYGd:Eu3+) phosphor with a high quantum efficiency of 58.4% and excellent color purity of 99.5% is reported for the first time. The phosphor is efficiently excited by NUV light at 394 nm and emits a strong red emission band in the 590-710 nm range, peaking at 612 nm. The optimal annealing temperature and Eu3+ doping content to obtain the strongest PL intensity are 1100 °C and 20 mol%, respectively. The optimized GdYGd:Eu3+ phosphor possesses a high activation energy of 0.319 eV and a lifetime of 1.14 ms. An illustration of phosphor-coated NUV LED with chromaticity coordinates (x = 0.5636,y = 0.2961) was successfully synthesized, demonstrating the great potential of GdYGd:Eu3+ phosphor for NUV-pumped WLED applications.

Fabrication of red-emitting Eu3+-induced CaS phosphors: a view of optical, in vitro, lifetime, structural and morphological studies for biomedical applications

Fabrication of red-emitting Eu3+-induced CaS phosphors: a view of optical, in vitro, lifetime, structural and morphological studies for biomedical applications

Structural and optical properties of a new Milarite type Na3 Mg4 LiSi12 O30 :Eu3+ phosphor.

A new red-emitting Eu3+ (1-17 mol%)-doped Na3 Mg4 LiSi12 O30 (NMLS) phosphor was prepared using a conventional solid-state reaction method at low temperature. The prepared samples belong to a hexagonal structure with a good match to JCPDS card no. 73-0934. The photoluminescence (PL) emission spectrum showed an intense peak at 612 nm when excited at 393 nm. The variation of electric dipole transition (5 D0 -7 F2 ) emission intensity with increasing Eu3+ ion concentration was investigated. The concentration quenching at 11 mol% is due to the dipole-dipole interaction mechanism in the NMLS host. The optimized NMLS:Eu3+ phosphor shows 2.18 times higher luminescence intensity than the (Y,Gd)BO3 (YGB) commercial phosphor. The NMLS:Eu3+ showed an intense red emission, having Commission Internationale de l'éclairage (CIE) coordinates (0.6280, 0.3691) and colour purity of 99.2%. The resulting phosphor exhibits good thermal stability of 80% at 423 K. The magnified images of fingerprint showed various minute features such as bridges, sweat pores, ridge end, bifurcation, island and core with better visualization under 393 nm excitation. Furthermore, the optimized NMLS:Eu3+ was used for pc-LED, latent fingerprints, and anticounterfeit applications as a promising red phosphor.

Blue-light excitable red-emitting Eu3+-doped TiO2 phosphor for WLED applications: Judd-Ofelt analysis and systematic investigation on its optical properties

Red-emitting Eu3+-activated TiO2 phosphors with excellent color purity of 99.9% have been successfully synthesized by a facile sol-gel method. PLE spectrum demonstrates that the obtained products have absorption bands ranging from 370 to 540 nm, with the highest band peaking at 464 nm. Under the blue excitation of 464 nm, the characteristic emissions of Eu3+ ions corresponding to the 5D0 → 7FJ transitions are observed, with the dominant emission peak at 614 nm. The optimal annealing temperature and dopant concentration are 5 h at 500 °C and 1.3 mol%, respectively. The PL quenching mechanism is attributed to the dipole-quadrupole interaction. The Judd-Ofelt analysis is carried out to explore the local structure environment around the Eu3+ ions. It is found that the highest asymmetry of the local environment surrounding Eu3+ ions and the strongest covalence Eu-O bond is attained at the annealing temperature of 500 °C and the activation energy is determined to be 0.385 eV. The fluorescence lifetime of the 614 nm emission was found to be 0.44 ms. These results indicate that the Eu3+-doped TiO2 phosphor may be a promising red-emitting phosphor for white light-emitting diodes.

Physico-chemical analysis of white light-emitting Eu, Dy and Cu tri-doped plasmonic glasses synthesized via nanodiamond

Phosphate glasses containing Eu2O3, Dy2O3 and CuO were melted together with nanodiamond (ND) powder for an assessment of optical and plasmonic properties aiming for the tuning of light-emitting properties towards photonic applications. A thorough evaluation incorporating optical absorption, differential scanning calorimetry, Raman scattering, and photoluminescence (PL) spectroscopy was carried out. The presence of ND allowed for the stabilization of the Cu+ ions with blue-emitting character alongside the yellow-emitting Dy3+ and red-emitting Eu3+ ions thus allowing for attaining the white light-emitting glasses. Further heat treatment within 470–490 °C of the tri-doped glass resulted in the development of the surface plasmon resonance (SPR) characteristic of Cu nanoparticles (NPs). A strong correlation of the optical bandgaps with SPR development is revealed. Further, a novel approach for assessing the activation energy for Cu NP precipitation is proposed linked to the glass transition temperature of the host. Subsequently, the effect of the plasmonic character on the PL properties was evaluated and correlated to the emission color. Correlated color temperature and chromaticity shifts were assessed and analyzed. The study contributes to the fundamental understanding and design of materials for tunable white light-emitting devices and the influence of incorporating plasmonic nanostructures attractive for photonic applications.

Surface engineered La2Zr2O7:Eu3+ nanophosphors: Luminescent based platform for latent fingerprints visualization and anti-counterfeiting applications

The advancements in the forensic technologies is still a constructive and requires continuous development and evaluation strategies are to be implement. In this regard, the present work deals with fabrication of novel surface modified red-emitting Eu3+ ions doped La2Zr2O7 nanophosphors and used for latent fingerprint visualization and data security applications. The powdered x-ray diffraction studies of the prepared samples confirm the disordered cubic phase. The photoluminescence emission spectra consist of intense emission peaks located at ∼ 576, 593, 613, 656 and 711 nm, ascribed to the 5D0 → 7FJ (J = 0 - 4) transitions of Eu3+ ions, respectively. The surface modified nanophosphors by oleic acid showed 2-fold enhancement in the emission intensity as compared to bare nanophosphors, which is due to effective intramolecular energy transfers from coordinated ligands to the activated Eu3+ ions, called the antenna effect. The photometric properties of the surface grafted nanophosphors exhibit pure red color with high purity. The visualized latent fingerprints using surface modified nanophosphor could reveal level 1 − 3 ridge characteristics, which is most reliable evidence for personal identification. High resolution images of developed latent fingerprints further validated the effective chemical binding between the hydrophobic nanophosphor and chemical constituents present in the fingerprints, which enables most authenticated sweat pores. The oleic acid grafted nanophosphors can be formulated into writable inks so that secret writings can be accomplished using a simple brush technique and decoded under ultraviolet light illumination. The followed surface modification strategy drastically improves the properties of the nanophosphor, which is real time choice for latent fingerprint development and anti-counterfeiting technologies.

Strong and pure red-emitting Eu3+-doped phosphor with excellent thermal stability for warm WLEDs

A red-emitting Eu3+-doped LiYO2 phosphor with excellent luminescence properties was prepared by solid phase reaction, showing potential in high-quality white-light-emitting diodes.