Concentration Of Rare Earth Ions Research Articles

Upconversion photoluminescence of Er-doped Bi$_{4}$Ti$_{3}$O$_{12}$ ceramics enhanced by vacancy clusters revealed by positron annihilation spectroscopy

Abstract Doping of rare earth elements into Bi$_{4}$Ti$_{3}$O$_{12}$ can significantly enhance the upconversion photoluminescence (UCPL) properties, but its structure-property relationship is still unclear. In this work, Er-doped bismuth titanate Bi$_{4-x}$Er$_{x}$Ti$_{3}$O$_{12}$ ($x$=0, 0.1, 0.2, 0.3, 0.4, 0.5) ceramics were synthesized via solid-state reaction method. The X-ray diffraction analysis confirmed the orthorhombic crystalline structure of the Bi$_{4-x}$Er$_{x}$Ti$_{3}$O$_{12}$ ceramics without any secondary phases. Experiments and calculations of positron annihilation spectroscopy were carried out to characterize their defect structure. The comparison between the experimental and calculated lifetime revealed that vacancy clusters were the main defects in the ceramics. The increase of the intensity of the second positron lifetime component (I$_{2}$) of Bi$_{3.5}$Er$_{0.5}$Ti$_{3}$O$_{12}$ ceramics indicated the presence of a high concentration of vacancy clusters. The UCPL spectra shown the sudden enhanced UCPL performance in Bi$_{3.7}$Er$_{0.3}$Ti$_{3}$O$_{12}$ and Bi$_{3.5}$Er$_{0.5}$Ti$_{3}$O$_{12}$ ceramics, which were consistent with the variation of the second positron lifetime component (I$_{2}$). These results indicate that the enhanced UCPL properties are influenced not only by the concentrations of rare earth ions but also by the concentration of vacancy clusters present within the ceramics.

Remarkable Plasmonic Enhanced Luminescence of Ce3+doped Lanthanide Downconversion Nanoparticles in NIR‐II Window by Silver Hole‐Cap Nanoarrays

AbstractLanthanide downconversion nanoparticles (DCNPs) have huge potential in biosensing and imaging applications in the NIR‐II window. However, DCNPs inherently suffer from low quantum efficiency, due to low absorption cross‐section and the restricted doping concentration of lanthanide ions. In this work, a combined strategy for downconversion luminescence in the NIR‐II window is investigated by the integration of Ce3+ ions into the conventional NaYF4: Yb3+, Er3+ DCNPs and incorporation of periodic silver hole‐cap coupled Nanoarrays (Ag‐HCNAs) simultaneously. Over two orders of magnitude, luminescence enhancement is achieved by the combination of optimized Ce3+ doping and plasmonic effects, compared to NaYF4: Yb3+, Er3+ DCNPs immobilized on the glass substrate. Moreover, 3D Finite‐Difference Time‐Domain (FDTD) simulations and time‐resolved luminescence measurements are combined to gain important insights into the mechanism of downconversion luminescence enhancement. The results show that there is a large electric field enhancement between the Ag nanoholes and the Ag hemisphere cap at 980 nm (excitation enhancement), while the lifetime shortening at 1525 nm revealed an increased radiative decay rate and enhanced quantum yield (emission rate enhancement). The strategy for downconversion luminescence enhancement demonstrated in this work holds a significant potential for advancing the next generation biosensing and bioimaging based on DCNPs in the NIR‐II window.

Effect of Li+ on luminescence properties and thermal stability of glass ceramics containing SrMoO4

Dy3+, Eu3+ co-doped glass ceramics (GCs) containing SrMoO4 crystalline phase were prepared by melt-curing-crystallization method. The most favorable heat treatment conditions for the glass ceramics were found to be 610 °C/2 h by differential scanning calorimetry (DSC), ultraviolet spectrophotometer (UV–Vis), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The best doping concentrations of Dy3+ and Eu3+ in this glass ceramic were 0.8 % and 0.6 %, concentration quenching caused by dipole-dipole interactions occurs when the content of rare earth ions in GCs continues to increase. The chromaticity coordinates of the Dy3+- Eu3+ co-doped glass ceramics changed from cool white light to warm white light with the addition of Eu3+ concentration. At the optimal doping concentration (0.8 % Dy3+-0.6 % Eu3+), the chromaticity coordinate of glass ceramics is (0.3972, 0.3331), and the related color temperature is 3047 K. The luminescence intensity can still reach about 80 % of room temperature at 180 °C, and its thermal quenching activation energy is 0.233 eV. This suggests that glass ceramics have excellent thermal stability. After adding an appropriate amount of Li+, the crystalline phase of the glass ceramics remained unchanged and the luminous intensity of the glass ceramics increased by a factor of about 1.4 in the same environment. The thermal quenching activation energy of the glass ceramic doped with 0.2 % Li+-0.8 % Dy3+-0.6 % Eu3+ was 0.344 eV. The experimental results indicate that GCs has potential application prospects in the field of solid-state lighting.

Efficient operation of atomic frequency comb optical memory using an optical frequency comb in 167Er3+:Y2SiO5

We demonstrated a highly efficient optical memory operation using an atomic frequency comb (AFC) created from a spectrally flattened optical frequency comb with an isotopically pure 167Er3+:Y2SiO5 crystal under zero magnetic field. Compared with standard AFC creation methods such as pulse train method, our method, called comb transfer method, can create a broadband and high-efficiency AFC at lower power and with less effort. This technique can make a significant improvement in the quality of AFCs in crystals doped with low concentrations of rare-earth ions.

Membrane pre-concentration as an efficient strategy to enhance the enrichment of rare earth by MgO precipitation

Taking advantage of the environmentally-friendly properties of a magnesium salt leaching agent, magnesium oxide (MgO) was used as a precipitant to enrich rare earth (RE) from leaching liquor in the magnesium salt system. This approach not only tackles the issue of ammonia–nitrogen pollution but also enables efficient magnesium recycling. However, due to the high concentration of magnesium ions and the low concentration of RE ions in the leaching solution, the precipitation kinetics of RE concentrates are sluggish, leading to low RE purity in the resulting precipitated product. In this work, we proposed a novel strategy that combines complexation-ultrafiltration (UF) pre-concentration with subsequent MgO precipitation to enhance the hydrolysis of MgO, promoting the precipitation of RE. We further improved the RE enrichment efficiency by optimizing membrane type, complexing agent selection, concentration levels, precipitation temperature, and MgO dosage. Under the conditions of concentrating the leaching solution using optimal UF membrane and employing glyphosate as the complexing agent, the RE ions concentration increased from 101 to 3940 mg/L, and we successfully separated magnesium ions with a separation factor of 36.4. A comparison between direct MgO precipitation and the pre-concentration approach revealed an 80 % reduction in precipitation time and an 80 % decrease in MgO usage with pre-concentration. Furthermore, this combined process led to an 8 % increase in RE recovery and a 2.8-fold enhancement in RE purity, and similar results were obtained when using actual mine leaching solutions. Additionally, the glyphosate present in the UF permeate and the precipitated mother liquor can be efficiently reclaimed through resin adsorption. This proposed process holds significant potential for engineering applications aimed at enriching RE.

Synthesis of NaYbF4:Er nanocrystals with controllable size, morphology, and multicolor upconversion luminescence for Anticounterfeiting applications

The dopant concentration of lanthanide ions plays one of the critical roles to manipulate size/morphology, photon population pathway, or luminescence color/intensity in upconversion nanoparticles (UCNCs), which have a significant effect on their application developments. Herein, a strategy is demonstrated for simultaneous size, morphology and multicolor luminescence tuning in the single doped lanthanide activator Er3+ ion system through simply tuning the concentration of Er3+ ions. The doping of different Er3+ ion amounts in NaYbF4:Er nanocrystals can control nanoparticle size (from several hundreds to tens of nanometers) and morphology. Moreover, multicolor upconversion luminescence involving green, yellow, orange and red can be obtained in the NaYbF4:Er UCNCs by changing the excitation power density of 980 nm laser. Mechanistic studies reveal the size and morphology evolution process as well as saturation/cross relaxation effects induced tunable multicolor emissions. These nanocrystals have demonstrated promising potential applications in anticounterfeiting. Our results not only provide a simple and feasible route for simultaneous size/morphology control and multicolor upconversion luminescence tuning, but also can further expand the utility of UCNCs in the frontier applications ranging from optical encoding to information security.

Decomposition of Luminescent Hydroxyapatite Scaffolds in Simulated Body Fluid.

We present a luminescence study investigating the dissolution of rare-earth-doped hydroxyapatite scaffolds in simulated body fluid (SBF), aiming to assess the luminescence stability of Tb-, Ce-, and Eu-doped scaffolds over time. Our findings reveal a consistent decrease in luminescence emission intensity across all samples over a four-week period in which the scaffolds were immersed in the SBF. In addition, energy-dispersive spectroscopy confirms a decrease in rare-earth ion concentration in the scaffolds with respect to time, whereas fluorescence spectroscopy shows the presence of rare-earth ions in the SBF, indicating the partial dissolution of the scaffolds over time. The use of rare-earth ions as luminescence markers provides insights into the mechanisms of apatite formation in hydroxyapatites. Thus, these scaffolds may find wider use in regenerative medicine, particularly in targeted drug delivery systems, where their luminescent properties have the potential to noninvasively track drug release.

Photoluminescence properties of Pb5(PO4)3Br:RE (RE = Dy3+, Eu3+ and Tb3+) phosphor synthesised using solid-state method.

This study describes the luminous properties of Pb5(PO4)3Br doped with RE3+ (RE = Dy3+, Eu3+ and Tb3+) synthesised using the solid-state method. The synthesised phosphor was characterised using Fourier-transform infrared, X-ray diffraction, scanning electron microscopy and photoluminescence measurements. Dy3+-doped Pb5(PO4)3Br phosphor exhibited blue and yellow emissions at 480 and 573 nm, respectively, on excitation at 388 nm. Eu3+-doped Pb5(PO4)3Br phosphor exhibited orange and red emissions at 591 and 614 nm, respectively, on excitation at λex = 396 nm. Pb5(PO4)3Br:Tb3+ phosphor exhibited the strongest green emission at 547 nm on excitation at λex = 380 nm. Additionally, the effect of the concentration of rare-earth ions on the emission intensity of Pb5(PO4)3Br:RE3+ (RE3+ = Dy3+, Eu3+ and Tb3+) phosphors was investigated.

Influence of Pr3+ ions on structural, photoluminescence, dielectric, and mechanical properties of barium lithium fluoroborate glasses

The influence of Praseodymium Oxide (Pr6O11) on the physical, optical parameters, photoluminescence, dielectric, and mechanical properties for 20BaF2 + 10Li2O+(70-x) B2O3 + xPr6O11 (where x = 0.0, 0.5, 1.0, 1.5 and 2.0 mol %)] glasses was investigated. FTIR spectra of the borate glass network doped with Pr6O11 demonstrate the vibrational modes. The current study found that adding Pr3+ ions to the glass increased the glass density, packing density (VP), oxygen packing density (OPD), and rare earth ion concentration (N). The optical parameters include refractive index molar refraction and molar polarizability, optical transmission, and reflection loss. All the optical parameters increased except optical transmission decreased with the rising of Pr3+ ions in the glass. The photoluminescence emission intensity increased with the concentration of Pr3+ ions. The dielectric constant decreased while AC conductivity increased with the applied frequency, particularly in the high-frequency region. The elastic moduli, including longitudinal, shear, bulk, Young, and microhardness increased with increasing the content of Pr3+ ions in the glass.

Influence of ionic radius on the degree of extraction of rare earth metals during sorption by the interpolymer system AMBERLITE IR-120 –AВ-17-8

Studies have been carried out on the sorption of rare earth metal ions in solution using the interpolymer system Amberlite IR-120:AB-17-8. The purpose of the work is to search for conditions for maximum sorption of rare earth elements (Dy, Tb, Gd, Eu and Sm) from aqueous solutions using the effect of remote interaction of ion exchange resins. Methodology. The residual concentrations of rare earth ions were determined using an Optima 8300DV Duo inductively coupled plasma spectrometer. Results. The best sorption characteristics were determined by the interpolymer system at a ratio of 3:3. The residual concentration of rare earth elements in the solution was: Dy – 4.64 mg/l, Tb – 4.16 mg/l, Gd – 4.21 mg/l, Eu – 4.16 mg/l, Sm – 4.56 mg/l. The variations in the ionic radius of the ions chosen for the study are Dy3+<Tb3+<Gd3+<Eu3+<Sm3+. The degree of sorption of interpolymer system increased with increasing ionic radius of the metals. For dysprosium with the smallest ionic radius, the degree of sorption was η – 52%, and for terbium, gadolinium and europium it increased to η – 58%. For individual Amberlite IR-120 (6:0), the degree of sorption of terbium ions was 47%. Conclusion. The results of the study showed that the interpolymer system with a ratio of 3:3 has the best sorption activity. It has been established that the degree of sorption of interpolymer pairs increases with increasing order of the ionic radius of metals (Tb3+< Gd3+< Eu3+).

Influence of Sulfate and Nitrate for Lanthanum (III) Adsorption on Bentonite: Implications for Rare Earth Wastewater Disposal

The direct discharge of rare earth wastewater causes the waste of resources and heavy metal pollution. This paper compared the adsorption behaviors of lanthanide ions on bentonite under sulfate and nitrate systems by examining the factors affecting the adsorption, such as adsorption time, pH, background electrolyte concentration, and initial rare earth ion concentration. It was shown that the sulfate system was more favorable for the adsorption of rare earth ions on the bentonite surface. The maximum adsorption capacity in the sulfate system was about 1.7 times that in the nitrate system. In contrast, the adsorption under the nitrate system was more sensitive to the changes in pH and background electrolyte concentration. The adsorption processes under both systems are spontaneous physical adsorption processes (ΔGθ are from −27.64 to −31.48 kJ/mol), and both are endothermic (ΔHθ are 10.38 kJ/mol for the nitrate and 7.53 kJ/mol for the sulfate) and entropy-increasing (ΔSθ are 61.54 J/mol for the nitrate and 76.24 J∙mol−1 for the sulfate) processes. This study helps to provide information about the optimizing process parameters for the adsorption treatment of rare earth wastewater using bentonite.

Evaporation characteristics of Er3+-doped silica fiber and its application in the preparation of whispering gallery mode lasers.

In this work, the concentration of rare-earth ions in doped silica whispering gallery lasers (WGLs) is controlled by evaporation. The fabrication of WGLs is used to experimentally evaluate the evaporation rate (mol/μm) and ratio (mol/mol) of erbium and silica lost from a doped fiber during heating. Fixed lengths of doped silica fiber are spliced to different lengths of undoped fiber and then evaporated by feeding into the focus of a CO2 laser. During evaporation, erbium ions are precipitated in the doped silica fiber to control the erbium concentration in the remaining SiO2, which is melted into a microsphere. By increasing the length of the undoped section, a critical point is reached where effectively no ions remain in the glass microsphere. The critical point is found using the spectra of the whispering gallery modes in microspheres with equal sizes. From the critical point, it is estimated that, for a given CO2 laser power, 6.36 × 10-21 mol of Er3+ is lost during the evaporation process for every cubic micron of silica fiber. This is equivalent to 1.74 × 10-7 mol of Er3+ lost per mol of SiO2 evaporated. This result facilitates the control of the doping concentration in WGLs and provides insight into the kinetics of laser-induced evaporation of doped silica.

Multicolor-emitting Er3+ and Er3+/Yb3+ doped Zn2GeO4 phosphors combining static and dynamic identifications for advanced anti-counterfeiting application

Anti-counterfeiting labels based on luminescence materials are a newly emerging technique for protecting legal goods and intellectual property. In the anti-counterfeiting field to prevent forgery and cloning, luminescence materials with properties different from the commercialized and traditional ones are in urgent need. In this work, multicolor-emitting Er3+ single-doped and Er3+/Yb3+ co-doped Zn2GeO4 phosphors combining static and dynamic identifications were developed in order to achieve advanced anti-counterfeiting application. The variation of trap content with increasing the doping content of rare earth ions was analyzed through X − ray photoelectron spectroscopy, thermoluminescence analysis. It was found that there are two types of traps with different depth in Zn2GeO4 phosphors. The depths of the traps were experimentally confirmed to be 0.68 and 0.79 eV, respectively. The transient photocurrent response measurement confirmed the existence of charge carriers, and the mechanism for long persistent luminescence was deduced. The multicolor upconversion mechanisms under 980 and 1550 nm excitation were also discovered. Based on the multicolor steady and transient emission features, an anti-counterfeiting pattern was designed using the phosphors. Static and dynamic identification was demonstrated and presented in detail. Finally, it is indicated that the studied phosphors are excellent candidates for potential applications in luminescence anti-counterfeiting labels.

Rare-earth (Dy3+ and Pr3+) ratio variation effects on electrical properties of sodium fluoride alumino borate glass system

Inlaying two RE ions simultaneously in the glass network, greatly impacts its properties and therefore its study is paramount. A glass series with composition 60B2O3 + 30NaF + 10Al2O3 + (1 − x) Dy2O3 + (x/3)Pr6O11 (where x = 0, 0.2, 0.5, 0.7 and 1 mol%) was prepared by melt quenching technique. The influence of both composition, concentration of rare earth ions and temperature variation in wide frequency range on electrical properties were investigated. The DC and AC conductivity curves for all the prepared compositions obeyed Arrhenius relation and Jonscher’s Power law, respectively. The frequency exponent “s” parameter was obtained to study the conductivity mechanism. Dielectric parameters were observed to be decreasing with a rise in frequency and increasing with temperature. Electric Modulus and Nyquist Plots for all compositions were studied to examine the relaxation behavior in prepared glasses as Debye or non-Debye. Depressed semicircular Nyquist plots were observed.

NaGdF4:Yb, Er, Tm Upconversion Nanoparticles for Bioimaging in Shortwave-Infrared Range: Study of Energy Transfer Processes and Composition Optimization

Upconversion nanoparticles are promising for many applications. For triple-doped nanoparticles (NPs), the luminescence intensity shows a non-linear dependence on the rare-earth ion concentration, making it difficult to obtain bright phosphors with high energy output. We investigated the energy transfer processes in β-NaGdF4:Yb-Er-Tm NPs and considered strategies for increasing the thulium luminescence intensity, in particular, the use of core–shell structures. The luminescence spectra were analyzed in the short-wavelength infrared (SWIR) and visible (VIS) regions. The Er3+ and Tm3+ luminescence lifetimes in the VIS region were measured to study the energy transfer processes between the active ions. The quenching of the Tm3+ luminescence in the SWIR region was observed. However, both Er3+ and Tm3+ luminescence bands were observed in the VIS range. We attribute these effects to energy transfer between Tm3+ 3F4 → 3H6 and Er3+ 4I13/2 → 4I9/2, which occurs due to overlap of Er3+ and Tm3+ luminescence bands, and also to competition between Er3+ and Tm3+ for energy transfer from Yb3+. For core–shell NPs, when Tm3+ and Er3+ are separated into adjacent layers, quenching cannot be avoided, likely due to the mutual diffusion of ions during shell synthesis. The most optimal strategy to obtain luminescence in the SWIR range is to use an inert intermediate shell between the layers containing Tm3+ and Er3+.

EPR and optical study of erbium-doped CeO2 and CeO2 / CeF3 nanoparticles

Here, the facile dry synthesis of composite CeO2/CeF3 nanoparticles doped with Er3+ probe ions using ammonium bifluoride (NH4HF2) is reported. This method allows synthesizing composite nanoparticles with different ratio of СеО2 and CeF3. The structural properties of the composite nanoparticles were studied using XRD, SEM, and TEM techniques, which confirmed the formation of composite CeO2/CeF3 nanoparticles. The luminescence spectra show that the intensity of the Ce3+ peak increases after fluorination procedure, revealing the fact that the amount of Ce3+ is increased. In particular, the total 4f-4f luminescence intensity of CeO2/CeF3:Er3+(0.1 at.%) nanoparticles is 3.5 time higher compared to CeO2:Er3+(0.1 at.%) ones under both UV or resonant pumping. Probably it can be associated with the increased concentration of trivalent rare-earth ions in a cubic-distorted environment. The same tendency is observed for the excitation spectra. EPR measurements showed that fluorination of CeO2 nanoparticles doped with different concentration of Er3+ ions leads to the formation of trigonal sites in ceria nanoparticles.

Investigation of dysprosium oxide substitution on physical, electrical and dielectric properties in sodium borosilicate glass system

Dysprosium oxide doped sodium borosilicate glasses were prepared in this study using a usual melt-quenching process. Further XRD, FTIR, density measurements, electrical conductivity, and dielectric properties were utilized to explore the prepared glassy samples. We found that all produced samples exhibit amorphous nature through X-ray diffraction. Increase in density and molar volume were found when dysprosium oxide concentration increased, which was ascribed to dysprosium oxide's greater molecular weight. Density data was used to calculate and explain several physical characteristics, including rare earth ion concentration (N), polaron radius (rp), internuclear distance (ri), and field strength (F).

Solution combustion synthesis of Dy3+doped La2O3 nanoparticles: An investigation of their structural, optical and photoluminescence characteristics

The impact of the varying Dy3+ (1–9 mol %) rare earth ion concentration on the structural and luminous characteristics of La2O3 phosphors was studied via solution combustion synthesis. Structure formation, photoluminescence (PL) effectiveness, optical properties, and energy transfer mechanisms were examined in detail. All the synthesised samples exhibits hexagonal structure, which is supported by X-ray diffraction patterns (space group: P-3 mL (164)). Scanning electron microscope analysis shows irregular particle size and shapes of the synthesised materials. The presence of prominent and dominant Dy3+ ion peaks in the excitation spectrum of the ideal sample material, correlate to the Dy3+ ion's absorption peaks, supports the existence of considerable energy transfer among La3+ and Dy3+ ions. The PL emission wavelengths at 486 and 570 nm assigned to the Dy3+ ions transitions 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 respectively owing to the charge-transfer between La3+ and Dy3+ ions. PL emission intensity increases up to 3 mol% and afterwards it starts to decrease due to concentration quenching caused by non-radiative interactions. Photometric properties were investigated to check the possible utilization of La2O3:Dy3+ phosphor in white light emitting diodes application with CIE (x- 0.3468, y- 0.3986), CCT (0.1957, 0.5060), and colour purity (23.8 %). Aforementioned findings suggest that the synthesized phosphor is a viable option for making w-LEDs using NUV chips serving as the source of excitation.

Thermal stability and spectroscopic properties of Eu-doped phosphate glasses for lasing applications

Current study is aimed at evaluating Eu-doped barium-bismuth phosphate glasses as potential visible laser medium operating in red spectral region. Samples with composition xEu2O3–20BaO–20Bi2O3-1.5Al2O3-(58.5-x)P2O5 (x = 0, 0.5, 1.0, 1.5) were prepared using melt-quenching technique. Physical parameters, such as, density, molar volume, oxygen packing density, rare-earth ion concentration, inter-nuclear distance and field strength were evaluated. Thermal stability of prepared glass samples was observed using Thermogravimetric Analysis (TG). The influence of rare-earth oxide content on glass transition temperature Tg, crystallization temperature Tc and onset of crystallization temperature Tx was studied through Differential Thermal Analysis (DTA). Optical band gap and related optical properties were evaluated from absorption spectrum recorded in the range 225–1000 nm. Judd-Ofelt parameters, branching ratio, radiative lifetime, emission cross-section and other radiative properties were evaluated from photoluminescence emission spectrum in the range 500–750 nm. High value of emission cross-section observed for transition 5D0 →7F4 in 0.5-EuBiPBa sample signifies its potential use in the development of visible lasers.

Structural characterisation of Pr3+ ions incorporated sodium lead Barium borate glasses

The Structural properties of 20Na2O – 10PbO – 10BaO –B2O3 – xPr2O3 glass doped with praseodymium have been investigated. The characterization techniques used for studying rare earth-doped glasses include energy-dispersive X-ray analysis (EDS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) for structural investigations. The concept of physical parameters plays a fundamental role in estimating the strength and structural compactness of the synthesized glass. Consequently, we investigated the influence of rare earth ions (Pr3+) concentration on physical properties. The nature and composition of the synthesized glass samples have been confirmed through Energy Dispersive X-ray Analysis (EDS) and Scanning Electron Microscopy (SEM). The results have been analyzed in view of the modified borate glass network.