Concentration Of Rare Earth Ions Research Articles

Enhancing multiphoton upconversion through energy clustering at sublattice level

The applications of lanthanide-doped upconversion nanocrystals in biological imaging, photonics, photovoltaics and therapeutics have fuelled a growing demand for rational control over the emission profiles of the nanocrystals. A common strategy for tuning upconversion luminescence is to control the doping concentration of lanthanide ions. However, the phenomenon of concentration quenching of the excited state at high doping levels poses a significant constraint. Thus, the lanthanide ions have to be stringently kept at relatively low concentrations to minimize luminescence quenching. Here we describe a new class of upconversion nanocrystals adopting an orthorhombic crystallographic structure in which the lanthanide ions are distributed in arrays of tetrad clusters. Importantly, this unique arrangement enables the preservation of excitation energy within the sublattice domain and effectively minimizes the migration of excitation energy to defects, even in stoichiometric compounds with a high Yb(3+) content (calculated as 98 mol%). This allows us to generate an unusual four-photon-promoted violet upconversion emission from Er(3+) with an intensity that is more than eight times higher than previously reported. Our results highlight that the approach to enhancing upconversion through energy clustering at the sublattice level may provide new opportunities for light-triggered biological reactions and photodynamic therapy.

Optical properties of oxide glasses with semiconductor nanoparticles co-doped with rare earth ions

This letter investigates PZABP glasses with nominal composition, 60P2O5. 15ZnO. 5Al2O3. 10BaO. 10PbO, doped with tellurium and co-doped with different concentrations of rare earth ions, ytterbium and europium. AFM, optical absorption, photoluminescence (PL) and time-resolved photoluminescence (TRPL) techniques characterized the vitreous systems. The formation of semiconductor nanoclusters ZnTe bulk-like and ZnTe quantum dots were identified. PL and TRPL show the energy transfer from the ZnTe nanocrystals and Eu3+ ions to Yb3+ ions. The optical properties presented qualify the system as potentially useful for light emission devices in the infrared region from 920 to 1060nm.

Fluorophosphate nanostructured glass ceramics activated by erbium ions

Possibility of preparation of transparent nanostructured glass crystalline materials based on fluorophosphate glasses with high fluoride content is demonstrated. The influence of concentration of rare earth ions (REI) on the crystallization process is studied. We determined the conditions of heat treatment to form nanocrystals containing REI whose growth is evidenced by the results of X-ray phase analysis changes in the absorption and luminescence spectra and in the lifetime of the excited level of trivalent erbium.

Low-temperature combustion synthesis and luminescent properties of SrMgAl10O17：Eu2+, Er3+ high brightness blue phosphors

The SrMgAl10O17:Eu2+ and SrMgAl10O17:Eu2+, Er3+ blue phosphors were synthesized by the combustion synthesis method. Their crystal structures and luminescent properties were analyzed by X-ray diffraction (XRD)、scanning electron microscope (SEM) and photoluminescence spectra, respectively. The XRD and SEM results indicate that the sample is well-crystallized in the combustion procedure, and its crystal structure has not changed when doped with low concentrations of rare-earth ions. PL results show that the phosphor of SrMgAl10O17:Eu2+ can be effectively excited by near UV LED chip with a broad emission spectrum extending from 430 nm to 520 nm, and has main peaks located at 460nm. Furthermore, the sample of the luminous intensity is the largest when the Er2+, Er3+ co-doped concentration is 4%, and the emission intensity of Sr0.95MgAl10O17:0.05Eu2+, Er3+ phosphor is significantly enhanced 54.9% higher than that of SrMgAl10O17:Eu2+ phosphor. It is indicated that Er3+has good sensitization effect for Eu2+ in luminescence, and this can be explained by the theory of energy transfer.

Modeling of Quantum Cutting Systems in $\hbox{Tm}^{3+}/ \hbox{Yb}^{3+}$-Codoped Spectral Converters for sc-Si Solar-Cell Efficiency Enhancement

Cooperative quantum cutting mechanism in a spectral converter of Tm3+/Yb3+-codoped tellurite glass is investigated by setting up and solving the theoretical model of rate equations and power propagation equations in MATLAB. Based on the optimal rare-earth (RE) ion concentration and the thickness of the spectral converter, a 155% total power conversion efficiency and a 171% total quantum conversion efficiency have been obtained. For a single-crystalline silicon solar cell, a 20.09% energy conversion efficiency under the optimized solar irradiation compared with a 17.94% energy conversion efficiency under the normalized solar irradiation has been obtained using PC1D, and the simulated relative energy conversion efficiency for the single-crystalline silicon solar cell approaches up to 1.12. These results show that the use of a spectral converter yields better single-crystalline silicon solar-cell performance compared with the normalized solar irradiation. Our results and techniques also provide a framework for investigating and optimizing the Tm3+/Yb3+ couple and other RE-doped spectral converters, potentially enabling a single-crystalline silicon solar cell with an efficiency enhancement.

Study of mid-infrared laser action in chalcogenide rare earth doped glass with Dy^3+, Pr^3+and Tb^3+

We present a study of chalcogenide glass fiber lasers doped with Dy3+, Pr3+ or Tb3+ that would operate in the mid-infrared wavelength range. A set of chalcogenide glass samples doped with different concentrations of rare earth ions is fabricated. The modeling parameters are directly extracted from FTIR absorption measurements of the fabricated bulk glass samples using Judd-Ofelt, Fuchtbauer–Ladenburg theory and McCumber theory. The modeling results show that, for all the dopants considered, an efficient mid-infrared laser action is possible if optical losses are kept at the level of 1dB/m or below.

Er3+ interlayer energy migration as the limiting photoluminescence quenching factor in nanostructured Er3+:Y2O3 thin films

We report the effects of Er3+ nanostructuring on optical properties of heterogeneously doped Er3+:Y2O3 thin films synthesized by radical enhanced atomic layer deposition. By alternating the cycle sequences of Y2O3 and Er2O3, rare earth (RE) ion concentrations were controlled from 4.8 to 11.8 at. % Er and the local Er2O3 thicknesses were varied between 0.7 to 7.6 Å. Photoluminescence (PL) was used to examine the 1535 nm (Er 4I13/2→4I15/2) emission at two excitation wavelengths, 488 nm and 976 nm. The normalized PL increased with increasing Er3+ concentrations up to 11.8 and 9.6 at. % under 488 and 976 nm excitations, respectively. The introduction of a local Er2O3 layer greater than 2.4 Å resulted in significant PL quenching, over an order of magnitude, under both excitation wavelengths. The quenching was attributed to enhanced local Er3+↔Er3+ interlayer energy migration. Compared to homogeneously doped RE systems where the RE concentration is directly related to the average RE↔RE spatial distance, increased luminescence was observed at high Er3+ concentrations in heterogeneously doped systems. These results suggest that controlling the RE proximity is key to engineering the optical properties of RE doped heterogeneous materials.

Effect of Concentration on the Photoluminescence Properties of Sm3+ and Dy3+: Cadmium Lithium Boro Tellurite Glasses

Rare-earth (Sm3+ or Dy3+) ions doped cadmium lithium boro tellurite glasses have been prepared by melt quenching method for their spectral studies. From X-ray diffraction (XRD) patterns the glass amorphous nature has been confirmed. Vis-NIR absorption, excitation and emission spectra of these glasses have been analyzed systematically and also rare earth ion concentration is optimised Sm3+: CLiBT glasses have shown strong orange-reddish emission at 598 nm (4G5/2-->6H7/2) with an excitation wavelength lambda(exci) = 401 nm and Dy3+: CLiBT glasses have shown strong yellow emission at 574 nm (6F9/2-->6H13/2) with lambda(exci) = 451 nm.

Investigation on the Physical and Optical Properties of Dy3+ Doped Soda-Lime-Silicate Glasses

Soda-lime-silicate glasses with the compositions of (65-x)SiO2-25Na2O-10CaO-xDy2O3 (where x = 0.0, 0.10, 0.30, 0.50 and 1.00mol %) were prepared by melt-quenching technique and characterized. The density (ρ) and molar volume (VM) obtained were found to increase with increasing Dy2O3 content. Such behaviour was accounted for by the differences between atomic weight and the atomic radii of the Si and Dy ions. The rare-earth ion concentration (N) and ionic radius (rp) were calculated. The absorption spectra of Dy3+ doped soda-lime-silicate glass correspond with several bands, which are assigned from the ground state, 6H15/2 to 4I13/2, 4F7/2(389nm), 4I15/2(453nm), 6F3/2(744nm), 6F5/2(797nm), 6F7/2(892nm), (6H7/2, 6F9/2)(1082nm), (6F11/2, 6H9/2)(1266nm), and 6H11/2(1649nm). The refractive index of glasses was increased with the increasing of Dy2O3 concentration.

Lanthanide ions as required cofactors for DNA catalysts

We report that micromolar concentrations of lanthanide ions can be required cofactors for DNA-hydrolyzing deoxyribozymes. Previous work identified deoxyribozymes that simultaneously require both Zn(2+) and Mn(2+) to achieve DNA-catalyzed DNA hydrolysis (10(12) rate enhancement); a mutant of one such DNA catalyst requires only Zn(2+). Here we show that in vitro selection in the presence of 10 µM lanthanide ion (Ce(3+), Eu(3+), or Yb(3+)) along with 1 mM Zn(2+) leads to numerous DNA-hydrolyzing deoxyribozymes that strictly require the lanthanide ion as well as Zn(2+) for catalytic activity. These DNA catalysts have a range of lanthanide dependences, including some deoxyribozymes that strongly favor one particular lanthanide ion (e.g., Ce(3+) >> Eu(3+) >> Yb(3+)) and others that function well with more than one lanthanide ion. Intriguingly, two of the Yb(3+)-dependent deoxyribozymes function well with Yb(3+) alone (K(d,app) ~10 µM, in the absence of Zn(2+)) and have little or no activity with Eu(3+) or Ce(3+). In contrast to these selection outcomes when lanthanide ions were present, new selections with Zn(2+) or Mn(2+) alone, or Zn(2+) with Mg(2+)/Ca(2+), led primarily to deoxyribozymes that cleave DNA by deglycosylation and β-elimination rather than by hydrolysis, including several instances of depyrimidination. We conclude that lanthanide ions warrant closer attention as cofactors when identifying new nucleic acid catalysts, especially for applications in which high concentrations of polyvalent metal ion cofactors are undesirable.

Emission from rare-earth ions in GaN wurtzite crystals

Intense studies of a wide-gap direct-zone semiconductor represented by GaN wurtzite crystals doped with rare-earth ions, namely, Eu, Er, Sm, and Tm, suggest the development of an alternative (compared to that with the use of InGaN layers) technology of fabrication of light-emitting diodes of white color. The opportunities of increasing the intensity of emission of intracenter 4f transitions are demonstrated for rare-earth ions in GaN wurtzite crystals by the optimization of doping technology, concentration of rareearth ions, and use of an additionally introduced impurity. The form of electroluminescence spectra of the GaN<RE<-based structures is similar to the form of photoluminescence spectra.

Controlled Synthesis and Up-Conversion Emission of Rare-Earth Tri-Doped NaYF&lt;SUB&gt;4&lt;/SUB&gt; Nanocrystals Under Femtosecond-Laser Excitation

Cubic nanocrystal and hexagonal micro-rods NaYF4, with predictable size, shape and phase, have been successfully synthesized through hydrothermal reaction. The growth mechanism and the effect of mass transfer on the morphology of hexagonal micro-prism are both discussed in detail. The increase of tri-doping lanthanide ion concentration decreased the size of crystal particle, which was explained by the Arrhenius rate equation together combined with the Gibbs-Thomson relationship. Furthermore, the dopants did not only affect the sizes of tri-doped NaYF4 micro-rods, but also impacted upon fluorescence intensity. The fluorescence of tri-doped NaYF4: Nd3+/Yb3+/Er3+ system, excited by an 800 nm femtolaser, was intensified with the increase of doped lanthanide ions concentration. Nevertheless owing to the fluorescence quenching, the other two systems (NaYF4: Nd3+/Ho3+/Er3+ and NaYF4: Nd3+/Tm3+/Er3+) did not show the same phenomenon.

Physical study of Sm 3+ doped borochromate glass system

Sm 3+ doped borochromate glasses of composition [ xSm 2O 3–74.5B 2O 3–25Li 2O–(0.5 − x)Cr 2O 3] with x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5 mol% have been prepared by conventional quenching melting method. The XRD profile confirm the amorphous nature of the glass samples. The density measurements were made using Archimedes’ principle of the prepared samples. Molar volume V M, rare-earth ion concentration N and ionic radius r p as well as field strength F have been estimated from the density measurements. The average optical basicity, Λ th, electronegativity χ 2av and electronic polarizability α 2− were calculated for the prepared glass samples. Influence of rare earth ions on structural behavior in borochromate glasses have been investigated using infrared spectroscopy (IR). The structural changes have been analyzed with increasing rare earth concentration. Partial BO 3 ↔ BO 4 conversion as a function of rare earth concentration was observed. From the relative peak areas of BO 3 and BO 4 in structural groups the ratio N 4 has been calculated. ESR spectra were recorded at room temperature. The obtain ESR signals were used to estimate the paramagnetic susceptibility ( χ).

Influence of Tm- or Er-codoping on the photodarkening kinetics in Yb fibers

We investigated photodarkening (PD) parameters of Yb/Al-doped silica fibers as a function of the concentration of additional rare earth ions like Tm or Er. It was found that both Tm and Er cause a decrease in Yb inversion followed by a reduction of PD in the case of Er, whereas Tm-codoping with more than 10 mol-ppm can strongly accelerate the process and also increase the PD loss. However, contrary to [1], we conclude that the typical PD behavior of Yb/Al fibers is an intrinsic feature of this fiber type and not caused by trace impurities of Tm (< 1 mol-ppm) unintentionally incorporated by the raw materials during fiber preparation.

Sol–gel synthesis, structural and optical properties of rare earth ions (Sm 3+ or Dy 3+) activated Ca 3Ga 2Si 3O 12 powder phosphors

Structural, morphological and optical properties of rare earth ions (RE 3+=Sm 3+ or Dy 3+) activated Ca 3Ga 2Si 3O 12 (CaGaSi) phosphors synthesized by the sol–gel method are reported. XRD results confirmed the cubic phase structure of RE 3+:CaGaSi phosphors. From the SEM images of RE 3+:CaGaSi phosphors, it is observed that the particles are agglomerated. Photoluminescence spectra of Sm 3+:CaGaSi phosphors have shown bright orange red emission at 598 nm ( 4G 5/2→ 6H 7/2) with an excitation wavelength of λ exci=401 nm. In the case of Dy 3+:CaGaSi phosphors bright yellow emission has been observed at 574 nm ( 4F 9/2→ 6H 13/2) with λ exci=451 nm. From the PL spectral results, the rare earth ion concentration of CaGaSi phosphors is optimized.

Additive coloring rate and intensity for pure and doped fluorite crystals

The mechanism of the additive coloring of calcium fluoride crystals, both pure and doped with I- and III-group elements, has been investigated. The coloring rate and intensity and the dependences of these parameters on the experimental conditions, vapor mixture pressure, and temperature have been experimentally determined. It is shown that the concentration of anion vacancies/electrons that can be introduced into crystals is in the range of 1017–1018 cm−3; in crystals with a high concentration of rare earth ions, the limiting concentration can be an order of magnitude higher.

Synthesis, the effect of rare earth ion concentration and temperature on luminescence properties of Eu 3+: Ba 3Y 2WO 9 ceramics

Eu 3+ ions activated Ba 3Y 2WO 9 ceramics were synthesized using a solid state reaction method and the luminescent characteristics were investigated. Photoluminescence spectra of Eu 3+: Ba 3Y 2WO 9 ceramics have shown strong red emission at 615 nm ( 5D 0→ 7F 2) with an excitation wavelength λ exci=392 nm ( 7F 0→ 5L 6). These powder ceramics have been characterized for their structures and morphology from the measurements of X-ray diffraction (XRD) and scanning electron microscope (SEM) results. Functional groups are identified using Fourier transform infrared (FTIR) measurements and elemental analysis has been carried out from the measurements of energy dispersive X-ray analysis (EDAX).

White up-conversion emission in Ho3+/Tm3+/Yb3+ tri-doped glass ceramics embedding BaF2 nanocrystals

Ho3+/Tm3+/Yb3+ tri-doped glass ceramics with white light emitting have been developed and demonstrated. Pumped by 980nm laser diode (LD), intensive red, green and blue up-conversions (UC) were obtained. The green emission is assigned to Ho3+ ion and the blue emission is assigned to Tm3+ ion, whereas the red emission is the combination contribution of the Ho3+ and Tm3+ ions. The RGB intensities could be adjusted by tuning the rare-earth ion concentration and pump power intensity. Thus, multicolor of the luminescence, including perfect white light with CIE-X=0.329 and CIE-Y=0.342 in the 1931 CIE chromaticity diagram can be obtained in 0.15 Ho3+/0.2Tm3+/3Yb3+ tri-doped glass ceramics embedding BaF2 nanocrystals pumped by a single infrared laser diode source of 980nm at 500mW. The up-conversion luminescence mechanism of Yb3+ sensitize Ho3+ and Tm3+ ions and the energy transfer from Ho3+ to Tm3+ in oxy-fluoride silicate glass ceramics were analyzed.

Luminescent nanomaterials containing rare earth ions for security printing

The high-efficiency luminescent nanomaterials with different emission wavelengths of red (YVO4:Eu3+), green (CePO4:Tb3+), ZnS:Mn2+ and YVO4:Eu3+;@SiO2 were successfully prepared with different concentrations of Mn and rare earth ions as active centres by chemical synthesis. Structure properties were studied. It was found that the particle size of our samples was in the range of 10-30 nm. Photoluminescent properties were studied under 325, 337, 365 and 370 nm excitations in order to apply in luminescent labels. The primary colour components are red and green emission making them very convenient and attractive for screen security printing systems. Hundreds of different labels with a size of 1-10 cm² were prepared by screen-printing as well as inkjet printing. By improving the Epson printer, commercial red, green and blue inks were used in the printing application. Screen and inkjet printing were deemed good methods for security printing. Our products were beautiful, high resolution and withstood tropical weather.

Luminescence spectra and optical properties of TeO 2–WO 3–Li 2O glasses doped with Nd, Sm and Er rare earth ions

New tellurite glass series of the form (70– x)TeO 2–20WO 3–10Li 2O– xLn 2O 3, where x=0, 1, 3 and 5 mol% and Ln=Nd, Sm and Er, were prepared. Density of the prepared glasses was measured and molar volume was calculated. Luminescence spectra of the prepared glasses were measured at room temperature using a micro-Raman spectrometer. The obtained luminescence intensity ratio was correlated with the rare earth ion concentration, the short distance between the identical rare earth ions r(Ln–Ln) and the glass density. Optical properties like refractive index, molar refractivity and optical polarizability were theoretically calculated in order to interpret the dependence of these properties on the rare earth ion content.