Photoluminescence Of Eu3 Research Articles

Formation and Photoluminescence of Eu$^{3+}$-Doped Y$_2$O$_3$ + H$_3$PO$_3$ Powders Produced by Using the Mechanochemical Method

Formation and Photoluminescence of Eu$^{3+}$-Doped Y$_2$O$_3$ + H$_3$PO$_3$ Powders Produced by Using the Mechanochemical Method

Vibrational and luminescent properties of LaPO4:Eu3+ with different preparation conditions

Monoclinic and hexagonal LaPO4:5 mol.%Eu3+ phosphors were synthesized with merely adjusting pH values of solutions by a hydrothermal method at the same synthesis temperature. The microstructure, morphology and photoluminescence of Eu3+-doped LaPO4, which were influenced by different preparation conditions, were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and luminescence spectroscopy, respectively. The specimen showed monoclinic structure in strong acid solution, however, it changed into hexagonal structure in weak acid solution and strong alkali solution. The monoclinic LaPO4:Eu3+ showed the longest length to diameter ratio, which was attributed to the preferential growth of [-112]. The monoclinic specimen exhibited a slight red shift in infrared spectra, Raman band positions and charge transfer (CT) compared with hexagonal specimens. Moreover, the calculated results of grain sizes, lattice parameters, full width at half maximum in Raman patterns and emission integral intensity were in good agreement with analysis results. The monoclinic specimen showed the maximal absolute luminescence quantum yield (0.4) and the second lifetime τ2 (0.52 ms), which was accordant with red-orange emission in CIE. The 5D0→7F1 occupied a dominate position in hexagonal specimens, which indicated that more Eu3+ in the hexagonal structure were occupied inversion center of symmetry sites.

Energy transfer and dissipation processes studied using photoluminescence of Eu3 + ions doped in epitaxial ZnO films

Photoluminescence from Eu3+ ions initiated by band-to-band excitations of ZnO host crystals was investigated in epitaxial films grown on sapphire C-planes. Emissions from Eu3+ ions were only observed when the films were deposited under H2O vapor gas flow. The maximum emission intensities were three times as large as those of films deposited on Si substrates. Close correlation between the emission intensities of Eu3+ ions and disorder in the host crystal lattice was evidenced by X-ray diffraction, which indicates that non-radiative energy dissipation channels determine the lifetime of the excited states, and high crystallinity is essential for intense emissions. In addition, the emission intensities from ZnO defects and Eu3+ ions exhibited a similar dependence on annealing temperature, suggesting the relevance of defect-mediated energy transfer from ZnO to Eu3+ ions. The excitation energy is shared among band-edge emissions, defect emissions, and emissions from Eu3+ ions, and these emissions compete with one another. In particular, the overlap of the Eu3+ emission energies on the red defect emission band facilitates efficient energy transfer from the ZnO crystals. Hydrogen atoms released from H2O will prevent Eu3+ ions from being bonded to excess oxygen atoms and/or promote substitution of Zn2+ sites with Eu3+ ions.

Synthesis and photoluminescence of EuII in barium zinc orthosilicate: a novel green color emitting phosphor for white‐LEDs

A series of Eu2+ -activated barium orthosilicates (BaZnSiO4 ) were synthesized using a high-temperature solid-state reaction. A photoluminescence excitation study of Eu2+ shows a broad absorption band in the range of 270-450nm, with multiple absorption peak maxima (310, 350 and 400nm) due to 4f-5d electronic transition. The emission spectra of all the compositions show green color emission (in the spectral region 450-550nm with a peak maximum at 502nm and a shoulder at ~490nm) with appropriate Comission Internationale de l'Eclairage (CIE) color coordinates. The two emission peaks are due to the presence of Eu2+ in two different Ba sites in the BaZnSiO4 host lattice. The energy transfers between the Eu2+ ions in BaZnSiO4 host are elucidated from the critical concentration quenching data based on the electronic multipolar interaction. All Eu2+ -activated BaZnSiO4 phosphor materials can be efficiently excited in the ultraviolet (UV) to near UV-region (270-420nm), making them attractive candidate as a green phosphor for solid state lighting-white light-emitting diodes.

Enhancement of photoluminescence in Eu3+ co-activated Ca2MgSi2O7:Dy3+ phosphors for solid state lighting application

A series of Ca2MgSi2O7:Dy3+, Ca2MgSi2O7:Eu3+and Ca2MgSi2O7:Dy3+, Eu3+phosphors were synthesized by conventional solid state reaction method. The X-ray diffraction (XRD) patterns were recorded to confirm the phase purity of Ca2MgSi2O7 phosphors. The XRD results showed that the prepared phosphors have single-phase tetragonal structure and incorporation of dopants has no effect on the crystal structure of phosphors. The surface morphological studies were performed using field emission scanning electronic spectroscopy (FESEM). Photoluminescence (PL) properties were systematically investigated in detail. With increasing, Dy3+ concentration the PL intensity first increases, reaches the maximum and then it was decreased. A Similar trend was shown in Ca2MgSi2O7:Eu3+ phosphors. The PL emission intensity was increased at the transitions 5D0 → 7F1 and 5D0 → 7F2 with increasing Eu3+ concentration while decreased the intensity at the transitions 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2. The calculated band gap values of the sample were found to be 4.29, 4.38, 4.11 and 4.23 eV.

Formation and photoluminescence of Eu3+ doped zirconia coatings formed by plasma electrolytic oxidation

Eu3+ doped ZrO2 coatings were formed by plasma electrolytic oxidation of zirconium in electrolyte containing Eu2O3 powder. The content of Eu in coatings increases with the time of PEO process. The coatings are crystallized and mostly composed of monoclinic ZrO2 phase. Photoluminescence (PL) emission spectra of Eu3+ doped ZrO2 coatings feature two distinct regions. The first region is related to ZrO2 PL band with a maximum positioned at about 490 nm, while the second region in the orange–red part of the spectrum shows sharp emission bands which are related to f–f transitions of Eu3+ from excited level 5D0 to lower levels 7FJ (J=0, 1, 2, 3, and 4). Excitation PL spectra of Eu3+ doped ZrO2 coatings monitored at 480nm feature a broad PL band with spectral maximum at about 280nm. In contrast, the excitation PL spectra monitored at the wavelength of the most intense peak in emission PL spectra can be divided into two regions: (a) the broad band region from 240nm to 350nm with a maximum at about 250nm, which is associated with the electron transfer transition from 2p orbital of O2− ions to 4f orbital of Eu3+ ions and (b) the region in the range from 350nm to 550nm with the series of sharp peaks, which correspond to direct excitation of the Eu3+ ground state 7F0 into higher levels of the 4f-manifold.

KY(MoO4)2:Eu3+ Phosphor: Template-Free Hydrothermal Synthesis and Luminescent Properties.

KY(MoO4)2 microcrystals with different morphologies, including rhombic, sheet-like, rectangular plate-like, and hexagon plate-like, have been successfully synthesized via a simple hydrothermal method without using any templates, surfactant, or other organic additives by varying the molar ratios of Y(NO3)3/K2MoO4 and pH values of the resultant solutions. X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), photoluminescence (PL), and photoluminescent excitation spectra (PLE) were employed to characterize the samples. Furthermore, a systematic study on the photoluminescence of Eu3+ doped KY(MoO4)2 samples has been explored by varying experimental conditions. The strongest red emission can be observed clearly at 616 nm. And by controlling the doping concentration of Eu3+ in KY(MoO4)2 solutions, it can be seen that the concentration quenching occurs at 25 at.% for Eu3+. These results suggest that the well-crystallized KY(MoO4)2:Eu3+ microcrystals synthesized in our experiment can be used as a red component for white light emitting diodes (W-LEDs).

Native defects determine phase-dependent photoluminescence behavior of Eu(2+) and Eu(3+) in In2O3 nanocrystals.

We demonstrate the coexistence of Eu(2+) and Eu(3+) in corundum and bixbyite-type colloidal In2O3 nanocrystals. The emission properties of dopants in both oxidation states are determined by their interaction with native defects, and are dramatically different in the two nanocrystal phases. This difference arises from the smaller nanocrystal size and higher defect density in metastable corundum-type nanocrystals.

Quenching Photoluminescence of Eu(III) by Cu(II) in ZnO:Eu3++Cu2+ Compounds by Solution Combustion Method

In this study Cu2++Eu3+ co-doped ZnO(ZnO/Cu2++Eu3+) solid solution powders were synthesized by solution combustion method using as oxidant agent zinc nitrate hexahydrate and as fuel urea; the Cu2+ concentrations were 0, 1, 2, 3, 10, and 20 %Wt; the Eu3+ ion concentration was fixed in 3%Wt. The samples after were annealed at 900°C by 20 h in air. The structural results showed the largely presence of a wurtzite solid solution of Cu2++Eu3+doped ZnO, at high Cu2+ doping CuO and Eu2CuO4 phases are also present. Morphological properties were analyzed using scanning electron microscopy (SEM) technique. However it is important to remark that the Cu2+ ions suppress the Eu3+ ion photoluminescence (PL) by means of an overlap mechanism between Cu2+ absorption band and Eu3+emission band (e.g. 5D0→7F2) of the Eu3+ emission spectra.

Optical studies of Eu3+ doped CaZrO3 phosphor for display device applications

The present paper reports the synthesis and characterization and photoluminescence of Eu3+ doped CaZrO3 nanophosphors. The samples were prepared by combustion a synthesis technique which is suitable for less time taking techniques for nano phosphors. The starting material used for sample preparation are Ca(NO3)2, (Zr(NO3)3 and Eu2(NO3)3 and urea used as a fuel. The prepared sample was characterized by X-ray diffraction technique (XRD) with variable concentration of Eu3+ (0.05–1mol%) there is no any phase change found with increase the concentration of Eu3+. Sample shows cubic structure and the crystallite size calculated by Scherer's formula. The surface morphology of prepared phosphor was determined by field emission gun scanning electron microscopy (FEGSEM) technique. The good connectivity with grains and the sphere like structure was found by FEGSEM. All prepared phosphor with variable concentration of Eu3+ (0.05–1mol%) was studied by photoluminescence analysis, it is found that the emission spectra of prepared phosphor shows broad excitation centered at 265nm with shoulder peak at 336nm. The emission spectra with variable concentration of Eu3+ shows strong peaks at 593nm and 613nm range the dominant peak at 613nm due to the allowed electronic transition 5D0–7F2 and weaker transition at 593nm is due to magnetic dipole transition 5D0–7F1. Spectrophotometric determinations of peaks are evaluated by Commission Internationale de I’Eclairage (CIE) technique. The phosphor shows good PL spectra in orange-red region so that the prepared phosphor is useful for display devices application.

Photoluminescence of Eu3+-doped glasses with Cu2+ impurities

Glasses activated with Eu3+ ions are attractive as luminescent materials for various photonic applications. Co-doping with copper has been proposed for enhancing material optical properties, but the quenching effect of Cu2+ impurities on Eu3+ emission in glass remains largely unexplored. In this work, Eu2O3/CuO-containing barium–phosphate glasses have been prepared by the melt-quench method, and the Eu3+ photoluminescence (PL) quenching resulting from Eu3+→Cu2+ energy transfer was evaluated. Optical absorption spectroscopy showed that with the increase in CuO concentration the Cu2+ absorption band resonant with Eu3+ emission (e.g. 5D0→7F2 transition around 615nm) developed steadily. As a result, Eu3+ PL was progressively quenched. Evaluation of the quenching constants as a function of temperature in the 298–673K range showed differences basically within experimental error, consistent with a resonant transfer and lack of phonon-assisted processes. Moreover, analysis of the Eu3+ emission decay dynamics revealed a strong correlation between the decay rates and Cu2+ impurity levels. Results imply that for practical applications the levels of Cu2+ in Eu3+/Cu+-activated glasses should be reduced if not removed as these will significantly limit device efficiency.

Magnetic Tuning of Optical Hysteresis Behavior in Lanthanide-Doped Nanoparticles

Magnetic-optical bifunctional materials have attracted tremendous interest due to their potential applications in biomedicine as well as multifunctional sensors. However, much attention has been paid on the bifunctional materials rendering magnetic and optical behavior individually, rather than the interaction between magnetic field and optical process. In this paper, we examine the coupling of magnetic field with photoluminescence in Eu3+-doped NaGdF4 nanoparticles. The Zeeman effect induced by magnetic field is clearly observed from the shift of luminescence bands and the splitting of the emission peaks. Furthermore, the luminescence intensity of different transitions of Eu3+ in paramagnetic NaGdF4 exhibits a hysteresis behavior when the magnetic field is scanned between 0 and 40 T. Compared with the optical behavior of Eu3+ in the nonmagnetic NaYF4, this optical hysteresis behavior of luminescence intensity is tentatively ascribed to the magnetic response of the paramagnetic dopant ions in both hosts. Due to the high magnetic field sensitivity, the Eu3+-doped bifunctional nanoparticles could be used as optical probes in sensor and biomedical areas.

Photoluminescence and doping mechanism of theranostic Eu3+/Fe3+ dual-doped hydroxyapatite nanoparticles

Theranostic nanoparticles currently have been regarded as an emerging concept of ‘personalized medicine’ with diagnostic and therapeutic dual-functions. Eu3+ doped hydroxyapatite (HAp) has been regarded as a promising fluorescent probe for in vivo imaging applications. Additionally, substitution of Ca2+ with Fe3+ in HAp crystal may endow the capability of producing heat upon exposure to a magnetic field. Here we report a preliminary study of doping mechanism and photoluminescence of Eu3+ and Fe3+ doped HAp nanoparticles (Eu/Fe:HAp). HAp with varied concentration of Eu3+ and Fe3+ doping are presented as Eu(10 mol%):HAp, Eu(7 mol%)-Fe(3 mol%):HAp, Eu(5 mol%)-Fe(5 mol%):HAp, Eu(3 mol%)-Fe(7 mol%):HAp, and Fe(10 mol%):HAp in the study. The results showed that the HAp particles, in nano-size with rod-like morphology, were successfully doped with Eu3+ and Fe3+, and the particles can be well suspended in cell culture medium. Photoluminescence analysis revealed that particles have prominent emissions at 536 nm, 590 nm, 615 nm, 650 nm and 695 nm upon excitation at a wavelength of 397 nm. Moreover, these Eu/Fe:HAp nanoparticles belonged to B-type carbonated HAp, which has been considered an effective biodegradable and biocompatible drug/gene carrier in biological applications.

The electronic structure and photoluminescence properties of BiOCl:Eu3+ from first-principles calculations

Europium-doped luminescent heavy metal bismuth oxychloride has been investigated by first-principles calculation, and the crystal structure, electronic structure, and optical properties of pure BiOCl and Eu-doped BiOCl have been examined and compared. Based on the calculated results, the luminescence properties and mechanism of Eu-doped BiOCl has been discussed. Owing to the unique layered structure, BiOCl host could produce enough separated electron–hole pairs, under UV-light excitation. Furthermore, because the energy levels (5D0) of Eu3+ is matched with the energy bands (the bottom of conduction band) of BiOCl, the energy transport and charge transfer from host to luminescence center can be efficiently carried out. Thus, the photoluminescence of Eu3+ could be enhanced in the matrix of BiOCl. These findings are helpful to understand previously published experimental results, and to improve novel luminescence materials.

Luminescent properties of MAl(SO4)2Br:Eu3+ (M = Sr or Mg) red phosphors for near‐UV light‐emitting diodes

Eu(3+) -activated MAl(SO4 )2 Br phosphors (where M = Mg or Sr) are successfully prepared using a wet chemical reaction technique. The samples are characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectroscopies. The XRD pattern revealed that both the samples are microcrystalline in nature. PL of Eu(3+) -doped SrAl(SO4 )2 Br and MgAl(SO4 )2 Br phosphors exhibited characteristic red emission coming from the (5) D0 → (7) F2 (616 nm) electron transition, when excited by 396 nm wavelength of light. The maximum intensity of luminescence was observed at a concentration of 1 mol% Eu(3+) . The intensity of the electric dipole transition at 616 nm is greater than that of the magnetic dipole transition at 594 nm. The results showed that MAl(SO4 )2 Br:Eu(3+) , (M = Mg, Sr) phosphors have potential application in near-UV light-emitting diodes as efficient red-emitting phosphor.

Development of two novel Eu2+-activated phosphors in the Na–Sc–Si–O system and their photoluminescence properties

Two novel Eu2+-activated phosphors in the Na–Sc–Si–O system were developed in this study, NaScSi2O6:Eu and Na3ScSi3O9:Eu. NaScSi2O6:Eu2+ showed yellow emission with a peak at 555nm under excitation at 220–430nm. When flux-treatment was performed for NaScSi2O6:Eu2+, we found the existence of a new phase. We then succeeded in synthesis of a high-purity sample of this new compound by a parallel solution synthesis method. It was revealed that the new phase was Na3ScSi3O9 with isostructure to Na3YSi3O9, and Eu2+-activated Na3ScSi3O9 exhibited photoluminescence. Na3ScSi3O9:Eu showed green emission with a peak at 530nm and a corresponding broad excitation band up to 500nm. However, photoluminescence of Eu2+ was negligible for Na3YSi3O9:Eu because of the stabilization of Eu3+ at the Y3+ site.

Spectral asymmetry and deep red photoluminescence in Eu^3+-activated Na_3YSi_3O_9 glass ceramics

We report on photoluminescence from Eu3+-activated Na,Y-silicates of the Na3YSi3O9 type. The effect of structural environment on Eu3+-related emission is considered by comparing a glassy reference host to its crystalline correspondents which are obtained through crystallization of the super-cooled melt. Crystallization is accompanied by a quantitative increase in quantum yield and external efficiency of photoluminescence. At the same time, strong Stark splitting of the emission bands and significant changes in the spectral symmetry of photoemission with a notable relative enhancement of the 5D0 → 7F4 relaxation are observed. The results indicate that Eu3+ ions partition on Y3+ lattice sites which undergo changes in coordination, volume and symmetry when moving from glassy to crystalline environment. Potential application of such Eu3+-activated Na3YSi3O9 silicate glass ceramics in light converters is considered.

An Abnormal Photoluminescence Enhancement in (Eu, Yb) Co-doped SiO2 Thin Film

We report on the photoluminescence (PL) properties of europium (Eu) and ytterbium (Yb) co-doped SiO2 thin film. The Eu (both Eu2+ and Eu3+) PL and the Yb3+ PL is co-related under different temperature annealing. However, upon 1100°C anneal, the Eu PL intensity is significantly stronger than other temperatures anneal. Transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction results, suggest that meta-stable Eu2+-related silicates (EuSiO3) have formed in the oxide as well as the formation of Yb2Si2O7.

Microscopic investigations of advanced thin films for photonics

We present the different approaches we recently followed to achieve intense room temperature photoluminescence (PL) from Si-based materials. On one side we obtained sub-bandgap PL from H-related defects induced by the H2 plasma treatment of Si photonic crystal (PhC) nanocavities. We demonstrated that a strong and narrow PL emission can be obtained in the PhC nanocavities due to the formation of a damaged layer mainly consisting of nanometric platelets and bubbles. An overall 40000-fold enhancement of the PL signal, with respect to pure crystalline Si, has been achieved and moreover the signal can be tuned in a wide range by only changing the PhC parameters. On the other side, we focused our attention on the properties of SiO2 and SiOC host matrices doped with Eu ions. C addition produces a strong enhancement of the Eu PL with respect to pure SiO2 films. The chemical and structural characterization of these materials reveals an extensive Eu clustering in SiO2-based films, while C addition induces a significant reduction of this phenomenon, enhancing the fraction of optically active Eu ions. These results can be applied for the realization of efficient Si-based light sources.

Surface modification of grains with silver nano-clusters: a new route to great enhancement of photoluminescence in Eu^3+-doped ferroelectric polycrystalline oxide thin films

We report on a new route to greatly enhance the photoluminescence of Eu³⁺ doped ferroelectric polycrystalline oxide thin films: surface modification of grains with silver nanoclusters (NCs). The Ag doped Bi₃.₆Eu₀.₄Ti₃O₁₂ (BET) thin films were prepared by a chemical solution deposition method. According to the XRD, TEM and XPS analysis, partially oxidated Ag NCs have been formed on the surfaces of the BET grains. A greatly enhanced photoluminescence was obtained in a wide range of Ag doping level. Role of the Ag NCs in the photoluminescence enhancement was investigated by means of absorption, emission and excitation spectra, as well as decay lifetime measurement. The results indicate that the intra-4f transition of Eu³⁺ can be intensively activated by the coupling of the charge transfer band of BET with the ⁵D₀ state of Eu³⁺ ions, and the enhancement of Eu³⁺ ions emission in the present thin films was attributed to the surface modification of BET crystalline grains by Ag NCs. In addition, the influences of Ag NCs on the dielectric and ferroelectric properties of these materials were discussed as well.