Upconversion Emission Of Er3 Research Articles

Intense green up/down conversion emission and high-sensitivity optical thermometry of NaYb(WO4)2:Er3+ stoichiometric phosphors

Optical thermometry based on fluorescence intensity ratio (FIR) has garnered significant interest among researchers due to its rapid, non-contact, and high sensitivity characteristics. In this study, stoichiometric NaYb(WO4)2 phosphors, doped with varying concentrations of Er3+, were successfully synthesized using the high-temperature solid-state method. Under both 980 nm and 266 nm excitation, the samples exhibited strong green and very weak red upconversion (UC) and downconversion (DC) luminescence. The structural and morphological properties of the prepared samples were thoroughly characterized using techniques such as X-ray diffraction (XRD), XRD Rietveld refinement, scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy. The phosphors demonstrated high-purity UC and DC emission, with maximum green-to-red ratios of 60.9 and 77.0, respectively. This discovery opens up vast possibilities for their application as pure green color converters. The UC emission of Er3+ ions in the stoichiometric NaYb(WO4)2 phosphor was identified as a two-photon UC process, as evidenced by the relationship between the luminescence intensity and the excitation power of the sample. Moreover, the temperature-dependent emission spectra of UC and DC were monitored, and investigated the fluorescence intensity ratios (FIRs) of 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions of Er3+ ions to assess the optical temperature sensing behavior of NaYb(WO4)2:Er3+. The experimental results revealed that the maximum absolute sensitivities (SA) of NaYb(WO4)2 phosphors were 0.0120 K-1 (UC) and 0.0077 K-1 (DC), and the maximum relative sensitivities (SR) were 0.0089 K-1 (UC) and 0.0092 K-1 (DC), respectively. These findings highlight the promising of Er3+-doped Yb3+ stoichiometric NaYb(WO4)2 phosphors in optical temperature sensors.

Fluorescence and temperature sensing properties of Zr4+ and Er3+ codoped Y2O3 prepared by laser annealing

AbstractY2O3 codoped with different Zr4+ (10% mol, 30% mol, and 49% mol) and constant Er3+ (2% mol) ions were successfully prepared via the laser annealing method. According to the XRD data, the lattice parameters decrease with the increase of Zr4+, and the grain size increases with Zr4+. The crystal space group switches from Ia‐3 to Fm‐3 m at a Zr4+ concentration of 49% mol. As the concentration of doped Zr4+ increases, the upconversion emission of Er3+ decreases. The nonequivalent substitution of Y3+ by Zr4+ creates lattice defects, which affect the fluorescence intensity of Er3+ ions in the material. The temperature sensing behavior of Y88%Zr10%Er2%O1.55 crystals based on the fluorescence intensity ratio between 4S3/2→4I15/2 and 4I9/2→4I15/2 transitions of Er3+ is studied. The results show that after codoping with Zr4+, the 4S3/2→4I15/2 and 4I9/2→4I15/2 transitions satisfy the Boltzmann distribution formula at temperatures above 333K. And the temperature sensing relative sensitivity can reach 2.96%K−1.

Luminescence enhanced temperature sensor based on the up-conversion emission in Er3+/Yb3+/Mo6+ tri-doped tellurite fiber

In this study, the green up-conversion (UC) fluorescence emission in Er3+/Yb3+/Mo6+ tri-doped tellurite glasses (TeO2–ZnO–Li2CO3–Bi2O3, TZLB) was explored for temperature sensing. The doping of Mo6+ ions allowed enhanced luminescence at moderate power pumping, avoiding the introduction of undesired laser-induced thermal effects while improving the spectral signal-to-noise ratio. The luminescence characteristics were investigated in detail at different doping molar ratio of Mo6+ ions, and the strongest was observed at 8 mol%. Drawing on tri-doped TZLB glass with the strongest UC emission intensity, a tri-doped TZLB fiber was fabricated and coupled with two multimode fibers (MMFs) via Ultraviolet (UV) adhesive, forming the temperature sensor. The sensor was further encapsulated by a silica tube sealed with Ultraviolet adhesive, overcoming the poor mechanical property of tellurite fiber. The temperature information could be demodulated based on the fluorescence intensity ratio technique. The temperature sensing performance of the tri-doped TZLB sensor was investigated as temperature varied from 258 to 420 K and its repeatability was experimentally verified. The Er3+/Yb3+/Mo6+ tri-doped TZLB has an application prospect in the field of lighting, and the so-based temperature sensor is expected to be applied to thermal detection in the fields of medical diagnostics, environmental monitoring, and optical thermometers, etc.

Control of red upconversion emission in Er3+–Yb3+– Fe3+ tri–doped biphasic calcium phosphate

This paper reports a novel red upconversion (UC) emission in Er/Yb/Fe tri-doped biphasic calcium phosphate (BCP) synthesized using a solid-state reaction method. The crystal structure of BCP was analyzed using Rietveld refinement, which confirmed the hexagonal structure of hydroxyapatite and the rhombohedral structure of beta-tricalcium phosphate with good crystallinity. The results of Rietveld refinement, Fourier-transform infrared spectroscopy, and diffuse reflectance spectroscopy revealed that the presence of Fe3+ in the host lattices strongly influenced the crystal structure of the phosphors. The phosphors showed intense red UC emission with a maximum at 660 nm upon the near-infrared excitation of a diode laser at 975 nm. Significantly, the red emission intensities of the Fe3+-doped sample were 60-times greater than those of the undoped sample. The preferential enhancement of red UC emission was due to the energy transfer from the high-energy excited state |2F7/2, 4T1g > of the Yb3+-Fe3+ dimer to the 4F9/2 state of the Er3+ ions. The UC emission mechanism was primarily estimated by the dependence of the UC spectral intensities on the laser 975 nm excitation power. The BCP: Er/Yb/Fe phosphor generating strong red UC emission could be used to develop a highly effective bioimaging tool in biomedicine.

The upconverted luminescence and chemical stability of morphologically controllable La2O3:Yb3+/Er3+ nanoparticles

Morphology and size controls are critical for the research of luminescent nanomaterials. In this work, La 2 O 3 :18%Yb 3+ /2%Er 3+ nanoparticles were synthesized by a urea-assisted coprecipitation process, where the morphology and size of nanoparticles could be precisely controlled by adjusting the doping concentration, urea dosage and reaction time. With increasing Yb 3+ doping concentration and reaction time, morphological evolution processes from nanosheets to nanospheres to nanofibers were observed. The experimental results revealed that the nanospheres could only be synthesized when 18%Yb 3+ and 2%Er 3+ were doped into the La 2 O 3 host, where the size of the nanospheres could be precisely controlled by adjusting the urea dosage. The effects of the particle morphology and size on the upconversion luminescence of La 2 O 3 :18%Yb 3+ /2%Er 3+ nanoparticles were investigated. In addition, the chemical stability of La 2 O 3 :18%Yb 3+ /2%Er 3+ nanospheres in air was investigated by recording XRD and upconversion luminescence spectra after exposure to air for different periods. The experimental conclusions were useful for further probing the effects of the particle morphology and size on the upconversion emission of Er 3+ . The upconverted luminescence and chemical stability of morphologically controllable La 2 O 3 :Yb 3+ /Er 3+ nanoparticles. • La 2 O 3 :Yb 3+ /Er 3+ UC nanoparticles were synthesized via the co-precipitation method. • The morphology was controlled by adjusting doping concentration and reaction parameters. • The UC luminescence of La 2 O 3 :Yb 3+ /Er 3+ was associated with the particle morphology and size.

Enhanced red up-conversion emission in Er3+/Yb3+ co-doped SrSnO3 for optical temperature sensing based on thermally and non-thermally coupled levels

In this work, the synthesis and characterization of SrSnO3:Er3+ 1% co-doped with Yb3+ x% (x = 1, 3, 5 and 7%) are shown. The synthesis was carried out by a modified sol-gel method. All the samples were characterized by X-ray powder diffraction and luminescence spectroscopy. All the synthesized phases have been indexed as distorted orthorhombic structures of SrSnO3 with the space group Pbnm. This study focuses on the optical properties of the doped and co-doped matrix. The up-conversion emission and optical temperature sensing properties of thermally and non-thermally coupled levels show the importance of co-doping with Yb3+ ions. The intensity of both green emissions, at 523 and 550 nm, increases when the co-doping of Yb3+ increases up to 5%, and then decreases. In the same way, the red emission (660 nm) increases in a more significant way when Yb3+ ions are present compared to when they are not in the matrix, showing the importance of Yb3+ as a co-dopant. The temperature sensing properties indicate the dependence of luminescence on temperature. To study this relationship, the fluorescence intensity ratio technique was used. The spectra were measured exciting at 975 nm while the sample was heated in a temperature range between 285 and 405 K, showing that the temperature dependence obtained for the intensity ratio (660/550) of these non-thermally coupled levels is temperature dependent and can be compared and studied as a temperature sensor. To study the performance and applicability of the material, the detection sensitivity, relative sensitivity and uncertainty temperature values were obtained. The excellent value obtained for the uncertainty temperature (approximately 0.1 K) using TCL indicates that the present material may be used as an effective temperature sensing device.

Energy transfer and controllable colors of upconversion emission in Er3+ and Dy3+ co-doped CaF2 transparent ceramics

x at. % Er3+, 3 at. % Dy3+: CaF2 transparent ceramics (x=1-5) with good transparency were fabricated by hot-pressed sintering. The phase composition of nanoparticles and transparent ceramics, microstructure, in-line transmittance, upconversion spectra and lifetime of transparent ceramics, as well as energy transfer mechanism between Er3+ and Dy3+ were investigated. The mean grain sizes of nanoparticles decreased from 33.0 nm to 26.2 nm with the Er3+ doping concentration increasing from 1 to 5 at.%. The microstructure of ceramic samples presented nearly dense microstructure and EDS analysis indicated Er3+ and Dy3+ were uniformly incorporated into CaF2 lattice. Under 900 nm excitation, the emission intensity for 4F9/2→6H15/2 transition of Dy3+ decreased and for 4S3/2→4I15/2 transition of Er3+ increased, the lifetime for the 4F9/2 level of Dy3+ decreased while the 4F7/2 level of Er3+ increased with the raise of Er3+ doping concentration. The energy transfer mechanism was proved to be the dipole-dipole interaction. The upconversion luminescence color was tuned from orange through yellow to green by changing the Er3+/Dy3+ ratio. In addition, the Vickers hardness, fracture toughness, and the thermal conductivity of Er3+, Dy3+: CaF2 transparent ceramics were discussed. All the results showed the Dy3+ could be used as a sensitizer for Er3+: CaF2 transparent ceramic in the upconversion field.

High-efficiency energy transfer pathways between Er(III) and Tm(III) in metal-organic frameworks for tunable upconversion emission and optical temperature sensing

In this work, Er3+/Tm3+ co-doped lanthanide metal-organic frameworks with uniform rod-like shape were obtained by one-step method, maintaining porous structure as well as upconversion characteristics under near-infrared excitation. The significant enhancement in upconversion emissions of Er3+ have been observed due to the Tm3+-mediated energy transfer pathways. By modulating the ratio of Er3+ to Tm3+, tuning upconversion luminescence from yellow to blue light were achieved. Efficient energy transfer from Er3+ to Tm3+ were demonstrated in metal-organic frameworks and the mechanism was discussed in detail. In addition, the Er/Tm-MOF was applied as an optical thermometer based on thermally coupled levels of Er3+, exhibiting high absolute and relative sensitivities. These results will pave an avenue to novel Ln-MOFs for color-tunable photoluminescence and optical sensors.

Enhanced upconversion emission in Er3+: BaWO4 through Gd3+ incorporation and optical thermometry

In this paper, a series of Er3+/Gd3+ co-doped BaWO4 phosphors have been synthesized through solid state reaction method. The corresponding upconversion(UC) luminescence properties were investigated under 980 nm excitation. The UC emission intensities of Er3+ ions were enhanced with Gd3+ doped, which was interpreted by crystal field deformation. Based on the fluorescence intensity ratio (FIR) technique, the temperature sensing characteristics of Er3 + ions were investigated. The maximum absolute sensitivity reached 15.49 × 10−3 K−1 at 523 K. The above results indicated that the Er3+/Gd3+ co-doped BaWO4 phosphor was a high efficient UC luminescence material and it could be used as photonic devices, temperature sensor purposes and an optical heater.

Synthesis, structure, and upconversion emission of Er3+ and Yb3+ co-doped YBO3

We investigated the upconversion (UC) properties of YBO3 co-doped with Er3+ and Yb3+ ions. The YBO3 samples were synthesized by the solid state reaction method. The Er3+ and Yb3+ were doped at various ratios into YBO3 to investigate the effect of concentration of the Er3+/Yb3+ ions on the UC emission. Rietveld refinement was performed on the X-ray diffraction patterns to obtain the crystal structural parameters. Strong red and green UC emissions were observed from Er3+ and Yb3+-codoped YBO3 under 980 nm diode laser excitation. The highest UC emission efficiency was achieved at 5 mol% concentration of both the Er3+ and Yb3+ ions. The power-dependent UC emission spectra of our samples indicate that the red UC emission of Er3+ should originate from a two-photon absorption process.

Spectral characteristics and optical temperature sensing properties of Er3+/Yb3+-co-doped phosphate glasses with GeO2 modification.

Er3+/Yb3+-co-doped phosphate glasses with GeO2 modification (PLAZGs) were successfully prepared by the melt-quenching method. The phenomenological intensity parameters Ωt (t=2, 4, 6) of the PLAZGs have been calculated by the Judd-Ofelt theory. Based on the phenomenological intensity parameters, the spectroscopic parameters of Er3+ and fluorescence intensity ratio (FIR) of green upconversion emissions were estimated. It was observed that, under 980 nm excitation, all samples exhibit green and red upconversion emissions of Er3+. The 10 mol% GeO2 modified phosphate glass has the strongest upconversion emission. Additionally, the fluorescence decays of the 2F5/2→2F7/2 transition of Yb3+ ions were measured to evaluate the energy transfer efficiency from Yb3+ to Er3+ ions. Finally, the optical temperature sensing properties based on upconversion emissions were investigated at temperatures from 150 K to 600 K. The maximum absolute temperature sensitivity S value of 6.0×10-3K-1 at 400 K is obtained, which indicates that the glass is promising for temperature sensing application based on the FIR technology.

Enhancing IR to NIR upconversion emission in Er3+-sensitized phosphors by adding Yb3+ as a highly efficient NIR-emitting center for photovoltaic applications

The IR to NIR upconversion emission is enhanced through codoping Yb3+ and the upconversion luminescence kinetics involved is investigated.

Optical thermometry based on up-conversion luminescence behavior in BaGdF5:Er3+ glass ceramics

Er3+ ions are often used as up-conversion (UC) activators for fluorescence intensity ratio (FIR) thermometer technique, and Yb3+ ions are co-doped for improving the UC luminescence efficiency of Er3+ ions. However, Yb3+ ions will cause heating effect by absorbing 980 nm laser excitation which affects the precision of FIR technique. Challenge of FIR technique still remains to seek for superior host materials of high UC luminescence efficiency without sensitizer Yb3+ ions, in which heating effect can be reduced. Herein, glass ceramics (GC) containing Er3+-doped BaGdF5 nano-crystals (NCs) were successfully elaborated through melt-quenching method. X-ray diffraction, scanning transmission electron microscopy and element mappings are convinced the formation of BaGdF5 NCs. The UC emissions of Er3+ ions are greatly enhanced due to the Er3+ dopants incorporated into the BaGdF5 NCs with low phonon energy. The temperature dependent FIR of two thermal coupled energy levels (2H11/2/4S3/2) was carried out from 300 to 720 K, and the maximum relative sensitivity is 1.36% K−1 at 300 K. According to all the above results, the BaGdF5:Er3+ GC may have possible utilization in thermometer with high precision.

Intense red upconversion luminescence in Er3+-sensitized particles through confining the 1532 nm excitation energy

Lanthanide-doped upconversion (UC) materials are commonly excited by 700–1000 nm laser because of Yb3+ (980 nm excitation) and Nd3+ (808 nm excitation) are typically used as sensitizers. However, the excitation band located in the second near-infrared window (NIR-II, 1000–1700 nm) demonstrates the deeper penetration in biological tissue with minimum tissue scattering and autofluorescence. Herein, intense red UC emission in Er3+-sensitized NaLuF4 particles under 1532 nm NIR-II excitation is presented. Red UC luminescence is significantly enhanced and purified through confining the 1532 nm excitation energy by Ho3+ and Tm3+ mediators, via an energy back transfer pathway (Er3+ → Ho3+ → Er3+ and Er3+ → Tm3+ → Er3+). Furthermore, when the particles injected into the fresh beef, red UC luminescence can be distinctly observed from the inside of beef under 1532 nm NIR-II excitation, implying the deep penetration of 1532 nm NIR-II excitation and 660 nm red UC emission. Our results suggest that bright red UC luminescence from Er3+-sensitized NaLuF4 crystals with 1532 nm NIR-II excitation may be suitable for deep optical imaging.

Energy transfer and cross-relaxation induced multicolor upconversion emissions in Er3+/Tm3+/Yb3+ doped double perovskite La2ZnTiO6 phosphors

Investigation on the bright and stable upconversion (UC) phosphors with multicolor emissions is fundamental and significant for the frontier applications of display and temperature probe. Here, diverse emitting colors with blue, cyan and yellowish green, which are caused by the energy transfer and cross-relaxation processes, are obtained by altering Er3+, Tm3+ and Yb3+ concentrations in Er3+ singly, Er3+ - Tm3+ - Yb3+ co- and tri-doped double perovskite La2ZnTiO6 (LZT) phosphors synthesized by a simple solid-state reaction. In addition, excellent infrared emission at 801 nm located at “first biological window” is collected in Tm3+-Yb3+ co-doped phosphors. Meanwhile, the temperature sensing properties based on the thermally coupled levels (2H11/2/4S3/2) of Er3+ ions were analyzed from 298 to 573 K of LZT:0.15Er3+/0.10Yb3+ phosphor, demonstrating that the maximal sensitivity value is about 56 × 10−4 K−1 at 448 K. All these results imply that this kind of UC material has potential applications in display, bioimaging and optical device.

Tunable upconversion emission in Er3+/Yb3+ co-doped oxyfluoride glass ceramics containing NaYF4 nanocrystals by the incorporation of Li+ ions

Rare earth doped glass materials with efficient tunable upconversion emission are a challenging field of research in the development of advanced optical devices. In this paper, tunable upconversion emission was realized by incorporating Li+ ions in Er3+/Yb3+ co-doped oxyfluoride glass ceramics containing NaYF4 nanocrystals. The prepared glass ceramics samples experience significant enhancement of luminescence intensity (up to 15 times) under 980 nm excitation. Meanwhile, a composite yellow emission with adjustable CIE chromaticity coordinates was achievable by altering the doping concentration of Li+ ions. The XRD analysis, absorption spectra and Judd-Ofelt theoretical calculations consistently revealed that these phenomena were associated with the Li+ caused shrinkage/expansion of NaYF4 crystal cells, which offers the possibility of emission tuning. The relevant luminescence mechanism was discussed in detail. Furthermore, it may pave new avenue for optimizing novel oxyfluoride glass ceramics applied in various optoelectronic fields.

Yb3+- and Er3+-doped Y2O3 microcrystals for upconversion photoluminescence and energy transfer with enhancements of near-ultraviolet emission

Yb3+ and Er3+ were doped into Y2O3 to form Y2O3: Yb3+, Er3+ microcrystals. The effect of doping concentration of Yb3+ was studied. The near-ultraviolet (UV) upconversion (UC) emission spectra of Y2O3: Yb3+, Er3+ were studied under 1.55-μm excitation. The near-UV UC emissions centered at 391 and 418 nm were enhanced by Yb3+ under 1.55-μm laser excitation. Er3+ generally acts as activator and is not used as sensitizer in the reference Er3+-doped oxides. In the present upconversion process under the 1.55-μm laser excitation, the energy transfer from Er3+ to Yb3+ and then Yb3+ to Er3+ was observed. Dopant Er3+ acted as not only activator but also sensitizer. The energy transfer between Er3+ and Yb3+ enhanced the near-UV UC emission of our materials. The near-ultraviolet (UV) upconversion (UC) emission spectra of Y2O3:Yb3+, Er3+ microcrystalswere studied under 1.55-μm excitation. Enhancements of near-UV UC emission of Er3+ were observed. The energy transfer from Er3+ to Yb3+ and then Yb3+ to Er3+ was thought to be the possible mechanisms for these enhancements. The doping concentration of the Yb3+ ion was studied also. In the upconversion process, Er3+ ion is not only as activator but also as sensitizer.

The influence of the nanocrystals size and surface on the Yb/Er doped LaF3 luminescence properties

Up-conversion luminescence and thermoluminescence properties of LaF3 nanocrystals, with sizes of about 20 nm, were studied and discussed in relation to -size and surface related effects. XPS spectra have evidenced the presence of oxidized Er and La ions within a thin layer (of about 1 nm thickness) at the nanocrystals surface, as well as Yb ions bonded with fluorine ions. The green ((2H11/2, 4S3/2) → 4I15/2) and red (4F9/2 → 4I15/2) up-conversion emissions of Er3+ ions are influenced by the relative dominance of Er-ions that reside within the thin oxidized layer. The broad thermoluminescence curves are assigned to the recombination of trap defects associated with surface states and within the oxidized surface layer.

A novel strategy for markedly enhancing the green upconversion emission in Er3+/Yb3+ co-doped VO2

There is a growing interest in developing upconversion nanocrystals at the forefront of promising applications. However, insufficient energy transfer between lanthanide ions still limited the practical application. In this work, a new class of welded-structure upconversion nanoparticles which emits bright green emission upon 980 nm near-infrared (NIR) laser excitation is presented. Importantly, this unique welded-structure arrangement enables the high-efficient energy transfer between different nanocrystals, leading to 65-folds enhancement for green upconversion emission. A continuous wave 980 nm laser is used to reduce interparticle distance followed by structure welding. The experiment findings show that the controlling distance of nanosheets enables readily manipulation the intensity ration of green and red emission, thereby allowing us to achieve the emission color purity tuning from pea green to bright green. And the green and red ratio achieved 11 folds enhancement, leading to a purer green light emission. The result not only provide an upfront experimental design for constructing welded-nanostructures with efficient energy transfer and color purity tunability, but also suggests a new pathway to build high-efficiency upconversion systems.

Up-conversion luminescence and highly sensing characteristics of Er3+/Yb3+ co-doped borophosphate glass-ceramics

Er3+/Yb3+ co-doped phosphate glass ceramics (GC) with a cubic KAlSi2O6type structure were successfully fabricated by traditional melt-quenching technique and subsequent heat treatment. Structural characterization of the GC was achieved by X-ray powder diffractometer (XRD) combined with transmission electron microscope (TEM). The up-conversion (UC) optical properties were systemically investigated through absorption spectra, photoluminescence spectra, pump power dependent UC emission spectra, and UC decay curves. The possible energy transfer process and the transition channels were analyzed by using energy level diagram. Results show that the UC luminescence performance of the GC was enhanced compared to precursor glass (PG). Moreover, the temperature dependent UC emission spectra of the GC were measured in the temperature range of 298–798K under 980 nm laser excitation. Combined with the fluorescence intensity ratio (FIR) technique, the UC emissions of Er3+/Yb3+ co-doped GC with two thermally coupled energy levels (TCELs) of 525 nm (Er3+: 2H11∕2→4I15∕2) and 549 nm (Er3+: 4S3∕2→4I15∕2) were studied as a function of temperature in the range of 298–798K. For optimized Er3+/Yb3+ co-doped GC, the theoretical maximum value of relative sensitivity Sr−max is 1.67 % K−1 at 298 K, and absolute sensitivity Sa−max is 4.59 ×10−3 K−1 at 570 K, which indicates that the Er3+/Yb3+ co-doped phosphate GC is a very promising candidate for optical temperature sensors with higher sensitivity.