Concentration Of Rare Earth Ions Research Articles

Strain-sensitive mechanoluminescence with high stability and self-recovery toward stretchable strain sensor

Due to its unique strain-light response, non-contact measurement and visualization characteristics, strain-sensitive mechanoluminescent (ML) materials are expected to replace traditional strain gauges as a new generation of strain sensing materials. The strain sensing technology has high requirements for the multi-parameter response characteristics, stability and sensing working range of sensing materials. In this work, a composite flexible strain sensing ML device composed of La4GeO8 doped with lanthanide rare earth ions Ln3+ and polydimethylsiloxane (PDMS) is proposed. The ML of the device can produce good linear response to stress, strain and loading rate under tensile action. The minimum strain response threshold is less than 2% of the relative strain, and the sensing range can reach 100% of the relative strain in the full elastic deformation range. In addition, the ML intensity of La4GeO8: Ln3+@PDMS has the characteristic of self-recovery, and its self-recovery is related to the maximum strain of loading and the placing time. The wavelength (visible-near infrared) and color adjustable ML can be achieved by adjusting the type and doping concentration of rare earth ions. Moreover, the device has high thermal stability and water resistance, indicating that it is also adaptable to extremely harsh environments. The results show that La4GeO8: Ln3+@PDMS can be used as a strain-sensing-material with multi-dimensional mechanical parameter response, and has potential application prospects in the field of flexible tensile strain sensors.

Structural and Photoluminescence Characterization of Oxyfluorides for Phosphor Applications

ConspectusRare-earth-containing phosphors were crucial to the advances made to compact fluorescent lamps (CFLs), which assisted in protecting a widely used halophosphate phosphor from degrading after exposure to a high ultraviolet flux. The CFL phosphors are often coated twice by depositing a light coat of rare-earth-containing phosphors over the inexpensive halophosphate phosphor, which generates white light with high efficacy and a good color rendering index and possesses a balance between phosphor cost and performance. Costs of phosphors can be mitigated by requiring lower rare-earth ion concentrations or by completely eliminating rare-earth ions, which was one of the main goals of investigating the oxyfluorides Sr3AlO4F and Ba2SrGaO4F as potential phosphors. Changes in the Sr3AlO4F and Ba2SrGaO4F structures were studied using high-resolution neutron diffraction annealing these materials in 5%H2/95%Ar and 4%H2/96% Ar, respectively. Annealing in these atmospheres causes self-activated photoluminescence (PL) to occur under 254 nm light, which makes them ideal materials for rare-earth-free CFL phosphors. Additionally, these hosts possess two distinct sites for isovalent or aliovalent substitution of Sr denoted as the A(1) and A(2) sites. Ga3+ can be substituted for Al3+ at the M site, which is known to have an impact on the self-activated PL emission color. The structural distortions noted included closer packing in the FSr6 octahedrons and AlO4 tetrahedrons in the Sr3AlO4F structure as compared to in air-annealed samples, which show no PL emission. Temperature-dependent studies reveal that both the air- and reductively annealed samples have identical thermal expansion within this temperature range (3-350 K). High-resolution neutron diffraction at room temperature confirmed the tetragonal structure (I4/mcm) for Ba2SrGaO4F, a novel material in the Sr3AlO4F family of materials, has been synthesized via a solid-state method. Analysis of the refined Ba2SrGaO4F structure at room temperature revealed expansion in the lattice parameters and its polyhedral subunits between the reductively annealed and air-annealed samples, which are correlated with the PL emission. Previous studies related to the application of these host structure types revealed that they have potential as commercial solid-state lighting phosphors due to their ability to resist thermal quenching as well as accommodate various levels of substitutions that will assist with color tunability.

Impact of Sm3+ ions on structural, thermal, optical and photoluminescence properties of ZnO–Na2O–PbO–B2O3 glasses for optoelectronics device applications

This work describes the impact of trivalent samarium (Sm3+) ions concentrations on the thermal, structural, physical, optical and photoluminescence (PL) characteristics in Zinc Sodium Lead Borate (ZnNaPbB) glasses with configuration (70-x) B2O3–10PbO–10ZnO–10Na2CO3-xSm2O3, (where x = 0.1–2.0 mol%). The glass samples were synthesized using a traditional melt-quench technique and characterized by various spectroscopic methods such as X-ray diffraction (XRD), Raman spectroscopy, Fourier Transform Infrared (FT-IR), UV–Vis–NIR spectra, Differential scanning calorimetry (DSC) and PL emission-excitation spectra to illuminate their photonic applications. The broad band perceived in the XRD diffractogram confirmed the amorphous nature of an un-doped ZnNaPbB glass. The physical properties including thickness, density, molar volume, dielectric constant, rare earth (RE) ion concentration, field strength and molecular electronic polarizability, etc. were calculated from the standard formulae. The FT-IR spectra identify the presence of stretching vibration in BO3 and BO4 units with some additional structural and functional groups with their bond nature. The observed DSC data was used to estimate the glass transition temperature (Tg). The absorption spectra presented all the probable transitions of Sm3+ ion-doped ZnNaPbB glass and the optical band gaps were computed using Tauc's method. All the glass samples depicted band gap values over 3 eV, proving that the material is insulating. The absorption spectra were utilized to evaluate Judd-Ofelt (J-O) parameters which were further used in different radiative parameters calculations to find the luminous levels of Sm3+ ions doped ZnNaPbB glasses. The PL emission spectra of the present ZnNaPbBSm glasses parade four bands parallel to the transitions 4G5/2 to 6H5/2 (563 nm), 6H7/2 (599 nm), 6H9/2 (646 nm) and 6H11/2 (706 nm), respectively. Additionally, the evaluated values of the emission cross-section and branching ratios describe the suitability of the present ZnNaPbBSm glasses for optoelectronic applications. Further, the colorimetric parameters such as CIE coordinates (x, y) and correlated color temperature (CCT) were evaluated using PL emission data and the measured CIE coordinates are found in the reddish-orange region for the present glasses. The time decay profiles of as-prepared glasses were used to evaluate the experimental lifetime, energy transfer parameter and type of donor-acceptor interaction. The Dexter theory and Inokuti-Hirayama (I–H) fitting are used to recognize the type of interaction in non-radiative energy transfer which is responsible for the concentration quenching. The result demonstrates that the as-prepared ZnNaPbBSm glasses are applicable for optoelectronics device applications.

Potentiality of low-temperature carbides from excess sludge to recover low-concentration rare earth ions: Isotherm, kinetic and thermodynamic

A low-temperature carbonization technique conducted under limited oxygen has been used to recycle excess sludge. The obtained low-temperature carbonized sludge (LCS) has been used in adsorption experiments with low-concentration rare-earth wastewater (rare-earth ion content of 103.45 mg/L, calculated on the basis of rare-earth oxides (REO)) to identify the most suitable carbonization conditions. Moreover, a response surface method has been used to optimize the adsorption conditions, focusing on the kinetics, isotherm, and thermodynamics of the process. Finally, the rare-earth ions loaded on the LCS were desorbed to assess the regeneration performance of the material. The results showed that the maximum degree of adsorption of low-concentration rare-earth ions on LCS was 94.1% under operation conditions optimized by the response surface method. Analysis of the kinetics and isotherm of the adsorption process showed it to be controlled by both liquid film diffusion and particle diffusion, corresponding to a pseudo-first-order kinetic model and the Langmuir adsorption isotherm. Analysis of the thermodynamics of the process showed the adsorption of rare-earth ions on LCS to be a non-spontaneous, exothermic, entropy-reducing process at high temperature. The results of desorption tests showed that the optimal conditions involved the treatment of LCS (1 g) loaded with rare-earth ions with 0.5 mol/L HCl (50 mL) for 1 h. The degree of desorption remained at about 70% after six desorption and regeneration cycles. Based on characterization results, it is inferred that the adsorption is a physicochemical process involving surface adsorption supplemented by chemical complexation.

Plasmon-enhanced upconversion luminescence on horizontally aligned gold nanorod arrays with self-contained spacer

The growing interest in converting infrared light to visible light in many photovoltaic fields requires the development of upconversion systems with high luminescence quantum yields and stability without blinking. However, the weak and narrow absorption of rare earth ions has greatly restricted the luminescent efficiency of rare earth dopants and hampered their translation from experimental research to real world applications. In this work, horizontally aligned gold nanorod arrays with self-contained spacer and obvious polarization dependent plasmonic properties are prepared on the substrate of silicon wafers by a self-assembly method of droplet evaporation, and polarization-dependent enhancement on the upconversion luminescence of rare earth ions doped nanoparticles (NaYF4: Yb3+, Er3+) are investigated. The results show that the luminescence intensity of the nanoparticles is greatly enhanced by a factor of about 140, when the horizontally aligned gold nanorod arrays are available as a substrate. The effect of self-contained spacer of the arrays to prevent quenching of the luminescence is investigated with the introduction of an Al2O3 layer as an isolate and the adjustment of its thickness. It is found that the self-contained spacer can effectively block the non-radiative energy transfer without the need of additional spacer. In addition, the horizontally aligned gold nanorod arrays also exhibit excellent optical polarization anisotropy. As the polarization angle of the incident light gradually increases, the intensity of the fluorescent radiation decreases, which is interpreted and analyzed by simulating the near field distribution. This strategy not only provides a powerful solution to build high-efficiency surface enhanced fluorescence systems, but also suggests a new pathway to realize the polarization-selective excitation of upconversion luminescence.

A comparative study on structural, magnetic and optical properties of rare earth ions substituted Bi1−x R x FeO3 (R: Ce3+, Sm3+ and Dy3+) nanoparticles

Abstract A comparative study on the manifestation of rare earth ions substitution induced alteration in structure, magnetic and optical properties of BiFeO3 nanoparticles was done. Sol-gel technique was employed to synthesize Bi1−x R x FeO3 (x = 0.05 and 0.10; R: Ce3+, Sm3+ and Dy3+) nanoparticles. X-ray diffraction patterns and Raman spectra analysis confirmed substitution driven structural phase transformation from distorted rhombohedral structure to orthorhombic structure for x = 0.10 samples. The enhanced magnetic properties with weak ferromagnetic behaviour were observed with increasing concentration of rare earth ions in BiFeO3 nanoparticles. The improved magnetic characteristics are attributed to many factors such as the uncompensated surface spins in nanoparticles, breaking of spin cycloid with R 3+ ions substitution and super exchange interaction between R 3+ and Fe3+ ions. The maximum magnetization values of 1.77 emu g−1, 1.87 emu g−1 and 5.5 emu g−1 were observed for x = 0.10 samples with Ce3+, Sm3+ and Dy3+ substitution, respectively. The magnetization increased with increasing difference in ionic radii of host Bi3+ (1.17 Å) ion and dopant Ce3+ (1.14 Å), Sm3+ (1.08 Å) and Dy3+ (1.03 Å) ions. UV–Visible diffuse reflectance spectra showed a sharp absorption in visible region and energy band gap values variation in the range 2.2 eV–2.33 eV.

Detailed optical analysis of Dy3+ and Pr3+ co-doped alumino-borate glasses for visible lighting applications

A new glass series with nominal molar composition of 60B2O3 + 30NaF + 10Al2O3 co-doped with Dy3+ and Pr3+, synthesized by melt quench was reported. The influence of Rare Earth (RE) ratio variation on prepared glasses was investigated by using Fourier Transform Infra-Red spectroscopy, UV–Vis–NIR absorption spectroscopy, Photoluminescence, Decay curves and Density measurements. Their X-Ray Diffraction and FTIR spectra revealed the glassy nature and confirmed that AlO6, AlO4, BO3 and BO4 units are the main structural units of that matrix. A non-linear variation following the same trend for tetragonal borate units (N4), Band gap, non-linear optical properties, Density, Molar Volume etc. was observed. Different optical parameters were obtained by UV–Vis–NIR spectroscopy. The Bonding parameter obtained from Nephelauxetic study indicated ionic nature of Dy3+ and covalent nature of Pr3+ ions. Photoluminescence excitation and emission spectra were recorded under variety of excitation wavelengths and corresponding color parameters were calculated using 1931 CIE standards. A detailed yellow to blue ratio analysis was reported as a function of RE ion concentration and excitation wavelengths. Composition DPNAB(x = 0.7) displayed the best performance with CIE coordinates (0.33, 0.37). Existence of Energy transfer from Dy3+ and Pr3+ was evidenced by the spectral overlap diagram and lifetime values obtained from fitting of Decay curves. From the obtained results, prepared glasses can be suggested for solid-state lighting devices like WLEDs and display devices.

Third-order optical nonlinear features of Er3+ and Pr3+ activated multicomponent borate glasses in nanosecond pulse regime: A comparative study

In the current work, the borate-based glass specimens bearing composition (mol %) 5Na 2 O–10ZnO–10Bi 2 O 3 ‒(75‒ x )B 2 O 3 – x RE (where RE = Er 2 O 3 and Pr 6 O 11 , and x ranges from 0 to 5 mol %) were synthesized by conventional melt-quench method. The effect of rare earth ions concentration on photonic nonlinearities has been explored by the Z-scan method under the pumping of 532 nm in a nanosecond pulse regime. The Z-signatures revealed the occurrence of nonlinear absorption and refraction in the studied glass specimens. The nonlinear optical features were improved with respect to the rare earth concentration. The nonlinear optical features were superior for Er 3+ doped glasses compared to Pr 3+ doped glasses. This greatness of nonlinear optical features in Er 3+ doped glasses was attributed to the existence of a large number of electrons (11 electrons) in the 4 f outer shell compared to those existing in the 4 f outer shell of Pr 3+ (2 electrons). The enhancement of nonlinear gap features was also attributed to the creation of non-bridging oxygens in the host network when rare earths are loaded into the composition. The nonlinear photonic outcomes endorse that heavily Er 3+ loaded glasses are superior over Pr 3+ doped glasses for nonlinear optical device fabrications to work in the visible region.

Effect of Pr6O11 on improving the Near–Infrared nonlinear optical characteristics of zinc borate glasses

For achieving superior nonlinear optical (NLO) features of glass samples, we have incorporated rare earth oxide (in this case, it is Pr6O11) in the composition. The NLO properties are rare earth ions concentration–dependent and, therefore, it is crucial to examine the concentration impact on the NLO attributes of glasses. The effectiveness of Pr6O11 concentration on NLO characteristics of the borate–based glass specimens in the near–infrared region in the femtosecond regime is being investigated in the current work using the Z–scan method. The two–photon absorption coefficients were almost constant up to 0.5 mol % of Pr6O11 and then showed increased behaviour. The nonlinear index of refraction magnitudes was improved with Pr6O11 content in the glass compositions. However, the optical limiting thresholds were found to be decreased with Pr6O11 quantity in the glass compositions. These increases in NLO features and optical limiting efficiencies are attributed to the non–bridging oxygens, polarizability and molar refractions of the glasses. The outcomes of Z‒scan characterization unveil that the high Pr6O11 glass specimens are favourable for the production of NLO devices and optical limiters to execute the functioning in the near–infrared region.

An indigenous tool for the adsorption of rare earth metal ions from the spent magnet e-waste: An eco-friendly chitosan biopolymer nanocomposite hydrogel

Recently, polymer nanocomposite hydrogel (PNC-hydrogel) has attracted the focus and attention of young and dynamic researchers in water remediation and purification due to its cost effectiveness, high processability, modified surface area, and enhanced absorptivity for the elimination of toxic ions of heavy metals and for its tunable properties as well as reusability. Chitosan (Cs), a deacetylated product of chitin, is the most promising and prospective biopolymer for adsorbing toxic heavy metallic ions from wastewater in diluted form. But when it is functionalized with any of its copolymers, its effectiveness and usability capacity are enhanced bythousand times in comparison to the virgin biopolymer, as it is less soluble in acidic aqueous medium. The functionalization of the biopolymer is proficient enough to bind the rare earth ions from the wastewater solution, and it is done by grafting the biopolymer with a variety of co-polymers. Herein, SiO2 nanopowder along with chitosan biopolymer based bionanocomposite hydrogel (SCB-hydrogel) has been prepared. This grafted biopolymer-based SCB-hydrogel was investigated by various techniques such as FTIR, XRD, FESEM, TEM, and UV-spectroscopy. The impact of numerous parameters including pH, adsorbate doses, time of contact, concentration of metallic ions, kinetic parameters with proper isotherms, desorptivity, and reusability of the PNC was studied in batch adsorption mode. The adsorption efficiency by the SCB-hydrogel with increasing concentration of lanthanide ions was observed to be 99 % from the waste diluted water followed by the Langmuir adsorption model along with kinetics of pseudo second order. Desorption of the lanthanides was also carried out by using 1 M H2SO4 and HCl solution. The adsorption efficiency of these PNC didn’t alter much as with the original in reusability of maximum three times. Keeping in view of cost effectiveness and adsorption efficiency of the SCB-hydrogel we have used it in a maximum of three times availing its uses as well as reusability for a maximum limit of adsorption of the REEs onto its surface.Thus, in conclusion, the PNC can be effectively used as a novel bio-adsorbent for treatment of wastewater containing pollutants along with transition rare earth metal ions (Nd+3, Pr+3).

Atomic scale network structure of a barium aluminosilicate glass doped with different concentrations of rare-earth ions explored by molecular dynamics simulations

Molecular dynamics (MD) simulation is employed for exploring the coordination of atoms in peralkaline BaO-Al2O3-SiO2 glasses of variable Gd3+ doping concentrations between 1 and 3.8 mol% Gd2O3. For this the MD simulation procedure of inherent structure sampling was used which provides statistically robust information on the local atomic surrounding of the doped rare earth ions. Distributions of Si/Al/Ba/Gd cations in the first, second and third coordination spheres are investigated. Special focus is laid on the effect of Gd3+ doping concentration on the local surrounding of the Gd3+ ions, i. e. rare earth clustering, and general glass structure. The simulations show that SiOAl bonds are preferred in comparison to SiOSi and AlOAl connections with respect to the random model predictions. Deviations from a statistical Si/Al distribution around the BaOp and GdOq polyhedra are observed. The network modifier ions are preferably surrounded by other network modifier ions, rather than by network formers. It is shown that the incorporation of Gd does not affect radial distribution functions, cumulative radial distribution function curves and the coordination sphere of Gd for Gd2O3 doping concentrations of up to 3.8 mol%, i.e. no rare earth clustering is observed. However, increasing Gd2O3 concentrations decrease the number of bridging oxygen and increase the number of non-bridging oxygen (NBO) species in the glass structure. Charge compensation of the additional non-bridging oxygen species is achieved by increasing NBO coordination numbers with Ba2+.

Coherent spin dynamics of rare-earth doped crystals in the high-cooperativity regime

Rare-earth doped crystals have long coherence times and the potential to provide quantum interfaces between microwave and optical photons. Such applications benefit from a high cooperativity between the spin ensemble and a microwave cavity---this motivates an increase in the rare-earth ion concentration which in turn impacts the spin coherence lifetime. We measure spin dynamics of two rare-earth spin species, $^{145}\mathrm{Nd}$ and Yb, doped into ${\mathrm{Y}}_{\text{2}}{\mathrm{SiO}}_{\text{5}}$, coupled to a planar microwave resonator in the high-cooperativity regime, in the temperature range $1.2\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ to $14\phantom{\rule{0.16em}{0ex}}\mathrm{mK}$. We identify relevant decoherence mechanisms, including instantaneous diffusion arising from resonant spins and temperature-dependent spectral diffusion from impurity electron and nuclear spins in the environment. We explore two methods to mitigate the effects of spectral diffusion in the Yb system in the low-temperature limit, first, using magnetic fields of up to 1 T to suppress impurity spin dynamics and, second, using transitions with low effective $g$ factors to reduce sensitivity to such dynamics. Finally, we demonstrate how the ``clock transition'' present in the $^{171}\mathrm{Yb}$ system at zero field can be used to increase coherence times up to ${T}_{2}=6(1)\phantom{\rule{0.16em}{0ex}}\mathrm{ms}$.

Growth process of Yb, Er: Na0.04K0.96Y(WO4)2 crystals and luminescence properties in the near infrared range

The top seed solution growth (TSSG) method was used to grow the x mol% Yb, 5 mol%Er: Na0.04K0.96Y(WO4)2(x = 1, 3, 5, 7) (Yb, Er: NKYW) crystals. The structure and physical properties of the crystals were investigated using TG-DTA and X-ray diffraction (XRD) characterization. The absorption and luminescence intensities of crystals doped with various concentrations of rare earth ions were studied. Inside the crystal, the luminescence mechanism is based on Yb3+ ions as the sensitizer and Er3+ ions as the activator. The x mol% Yb, 5 mol%Er: NKYW (x = 1, 3, 5, 7) crystal spectral intensity parameters Ω2, Ω4, and Ω6 were calculated using the Judd-Ofelt theory. The absorption cross section, emission cross section, and gain cross section assisted analysis concluded that the 3 mol% Yb, 5 mol%Er: NKYW crystal has high laser emission potential. This research helps to advance the development of high- performance laser materials.

Paper-based LRET sensor for the detection of total heavy rare-earth ions.

Based on the mechanism of luminescence resonance energy transfer (LRET) and using a special single strand DNA as the recognition element, a portable paper-based sensor for the accurate detection of total heavy rare-earth ions (mainly Gd3+, Tb3+ and Dy3+) concentration was proposed. The RNA cleaving-DNAzyme should recognize rare-earth ions to cleave RNA on DNA duplexes linking UCNPs and AuNPs, causing UCNPs and AuNPs to approach each other, inducing LRET, which attenuated the green upconversion luminescence (UCL) triggered by the 980 nm laser. UCL was captured by a charge-coupled device (CCD) image sensor and processed with the red-green-blue (RGB) image to quantitatively analyze heavy rare-earth ions in the samples. In the range of 5–50 μmol·L-1, the sensor has good sensitivity, with the limit of detection of 1.26 μmol L−1.

Fabrication luminescence and radiation shielding properties of Gd2O3–La2O3–ZnO–B2O3–Sm2O3 glasses

The purpose of developing high transparency radiation shielding materials and luminescence materials with stoichiometric ratio of xGd2O3:10La2O3:10ZnO:(79-x) B2O3: 1Sm2O3 where x = 0, 5, 10, 15, and 20 mol% using melt quenching technique. The physio-optical properties such as molar volume, density, concentration of rare-earth ions, polaron radius, inter-ionic radius, optical basicity, average distance between rare-earth ions, and optical packing density of the present glasses has been evaluated. The glass samples obtained show high density which is vital factor for radiation shielding. The absorption spectra show significant of bands Sm3+ ions. The FTIR results of Gd-La-Zn-B-Sm (Gd-1Sm) glass samples show signature borate BO3 and BO4 vibrational units in Gd-1Sm glass samples. The μ, μm, HVL, TVL, and MFP were evaluated and showed that the values decrease with increasing X-ray energy whereas increase with an increase in Gd2O3 content suggesting their potential use in X-ray diagnosis regions. The HVL value was compared with commercial windows, concrete, Serpentine and X-ray windows and found that the glasses doped with 10 mol%, 15mol%, and 20 mol% Gd2O3 content showed better results than X-Ray windows at 10 kVp. The emission and excitation spectra of glass samples were studied and emission spectra show orange emission bands. The experimental lifetime analysis shows that the glass samples show decreasing trend from 1.161 to 1.128 ms with an increase in Gd3+ ions exhibiting single exponential nature.

(INVITED)Rare-earth ions doped glasses based on TeO2 and GeO2 with and without nanoparticles used as cover to increase Si solar cell performance: A review of recent results

The search for new materials to improve the efficiency of the light electricity conversion process of photovoltaic devices has grown in the last years. As there is always a mismatch between Si solar cell absorption and the solar spectrum, the use of luminescent materials as cover layer represents an alternative to overcome this problem. In this context the down and upconversion processes together with the plasmonic effects of metallic nanoparticles (NPs) to improve the luminescence of the materials play an important role. A review of recent works with glasses prepared with the melt quenching technique, used to increase the performance of photovoltaic devices due their luminescence is presented. So we present results of glasses based on GeO2 and TeO2 doped with rare-earth ions whose luminescence growth due to crystalline NPs (Ag or Au) or dielectric ones as TiO2, crystallized in anatase phase, increased the photovoltaic efficiency of up to 18%. Moreover, the influence of the rare-earth ions concentration on the efficiency increase in samples without NPs is also reviewed. The contribution of the transmittance of the material is highlighted as it also plays an important role to understand the enhancement of the Si solar cell performance.

Simultaneous Observation of Visible Upconversion and Near-Infrared Downconversion in SrF2:Nd3+/Yb3+/Er3+ Nanocrystals and Their Application for Detecting Metal Ions under Dual-Wavelength Excitation.

In this work, a sequence of Nd3+, Yb3+, and Er3+ tridoped SrF2 nanocrystals (NCs) is synthesized by a hydrothermal method. Both the efficient near-infrared downconversion luminescence (DCL) and visible upconversion luminescence (UCL) of the Er3+ and Nd3+ ions are simultaneously observed and systematically demonstrated under dual-wavelength excitation (808 and 980 nm continuous-wave lasers). Subsequently, the SrF2:Nd3+/Yb3+/Er3+ (15/4/0.2 mol %) NCs with the strongest luminescence were utilized for detecting the metal ion concentrations under 808 nm excitation. The results reveal that both the UCL and DCL gradually decrease as the metal ion concentrations increase, and high sensitivity is obtained for Cu2+ ions with a detection limit of 0.22 nM (∼650 nm) and 0.63 nM (∼976 nm). In addition, these SrF2:Nd3+/Yb3+/Er3+ NCs are further demonstrated to achieve a solid-state display under 980 nm excitation, exhibiting obvious “red” and “green” patterns by varying the doping rare earth ion concentrations.

Luminescence properties and time-resolved spectroscopy of rare-earth doped SrMoO4 single crystals

Luminescence properties of nominally pure and doped with Eu3+ and Pr3+ ions SrMoO4 single crystals grown by the Czochralski method have been studied. Thermal quenching of intrinsic emission of pure and doped SrMoO4 single crystals has been observed, as well as a correlation of thermal quenching activation energies with rare-earth ion concentration has been observed. Tunable laser was used to study time-resolved luminescence in a range from 10 K to room temperature. The effect of dopant nature and concentration on intrinsic emission and decay kinetics has been elucidated.

Bioadsorption of Terbium(III) by Spores of Bacillus subtilis

Wastewater containing low concentrations of rare earth ions not only constitutes a waste of rare earth resources but also threatens the surrounding environment. It is therefore necessary to develop environmentally friendly methods of recovering rare earth ions. The spores produced by Bacillus are resistant to extreme environments and are effective in the bioadsorption of rare earth ions, but their adsorption behaviors and mechanisms are not well understood. In this study, the cells and spores of Bacillus subtilis PS533 and PS4150 were used as biosorbents, and their adsorption of terbium ions was compared under different conditions. The adsorption characteristics of the spores were investigated, as were the possible mechanisms of interaction between the spores and rare earth ions. The results showed that the PS4150 spores had the best adsorption effect on Tb(III), with the removal percentage reaching 95.2%. Based on a computational simulation, SEM observation, XRD, XPS, and FTIR analyses, it was suggested that the adsorption of Tb(III) by the spores conforms to the pseudo−second−order kinetics and the Langmuir adsorption isotherm model. This indicates that the adsorption process mainly consists of chemical adsorption, and that groups such as amino, hydroxyl, methyl, and phosphate, which are found on the surface of the spores, are involved in the bioadsorption process. All of these findings suggest that Bacillus subtilis spores can be used as a potential biosorbent for the recovery of rare earth ions from wastewater.

Synthesis and spectroscopic properties of Er3+/Yb3+-codoped GdNbO4 phosphor for thermometry and marine safety protection

Micron-sized GdNbO4:Er3+/Yb3+ phosphors were prepared by employing a high-temperature solid-state reaction. The crystalline phase, morphology, composition, spectroscopic properties, and impact of rare-earth ion concentration, temperature and high salinity environment were systematically characterized. The extracted results show that phosphor is dominated by the existence of the GdNbO4 crystalline phase. Their morphology and agglomeration phenomenon are strongly dependent on the rare-earth concentration. The phosphor exhibits also excellent up-conversion luminescence (UCL) properties under 980 nm excitation, while a two-photon process accounts for UCL. The following optimal concentrations were selected for enhanced UCL intensity: 10 mol% for Yb3+ and 3 mol% for Er3+. The phosphor shows excellent thermometric performances including strong UCL, good thermal stability, appropriate sensitivity and a wide sensitivity response range. To evaluate the accuracy of the present optical thermometer, the temperature of a heated bench has been comparatively measured by using the proposed optical thermometer and a commercial thermocouple with an accuracy of 1 K. By comparing the temperature values measured by the two methods, it can be concluded that the present optical thermometer has an accuracy better than 1.6 K. In addition, the phosphor exhibits good chemical stability in high salinity environment. Interestingly, its crystalline phase, structure, and UCL spectral structure, intensity and color are all preserved after one-month immersion into a high salinity solution.