Upconversion Luminescence Of Er3 Research Articles

Luminescent manifestations of ytterbium ions in the crystal structure of silicate apatite

The manifestation of ytterbium ions in the microcrystals of the Sr2Y6.8YbSi6O26:Er0.2 solid solution with apatite structure was studied on the basis of low-temperature photoluminescence (PL) spectroscopy and spectral-kinetic measurement data. Intracenter down-conversion luminescence of Er3+ ions in the visible and IR ranges was detected. Up-conversion luminescence of Er3+ ions is observed upon IR excitation due to excitation of Yb3+ ions and subsequent energy transfer Yb3+ → Er3+. Overlapping bands at 412 and 430 nm with a Stokes shift of less than 0.3 eV are observed in the PL spectra at room temperature. These emission bands are assigned to the spin-allowed and spin-forbidden 4f135d → 4f14 transitions from the low-spin and high-spin exciting states of Yb2+ ion, respectively. The PL decay kinetics for transitions from the low-spin states is characterized by a dominant component τ = 0.39 ns. An alternative model of Yb3+ luminescence center associated with a charge transfer band does not explain the data of low-temperature (5K) PL spectroscopy. At T = 5 K, a new wide emission band with a maximum at 696 nm and a Stokes shift of 1.1 eV appears in the PL spectrum. Two options of this PL band nature are considered. The first is the luminescence of defects having a vacancy nature. The second possible option is the manifestation of anomalous luminescence of Yb2+ ions, which occupy a different crystallographic position in the apatite crystal structure.

Effect of microwave heat-treatment on up-conversion luminescence of Er3+/Yb3+ co-doped NaYF4 oxy-fluoride glass-ceramics

The microscopic properties of fluoride grains are known to play critical roles in the up-conversion luminescence properties of phosphors carrying rare-earth-based luminescence centers. To study the effect of different heating methods during preparation on the microstructure and up-conversion luminescence performance of oxy-fluoride glass-ceramics, we synthesized Er3+/Yb3+ co-doped NaYF4 nanocrystals containing transparent glass-ceramics by microwave heat-treatment and the normally heating methods. We characterized the internal structure of glass-ceramics by X-ray diffraction, transmission electron microscopy, mid-infrared spectroscopy, and Raman spectroscopy. While glass-ceramics samples prepared by both methods have extremely high optical transmittance similar to that of a glass, the microwave heat-treatment promoted faster grain growth rate, the glass-ceramics sample had better crystallinity and much improved up-conversion luminescence intensity compared to the sample obtained by the normally heating method.

Effect of rapid thermal annealing treatment on up-conversion luminescence in Er3+/Yb3+ co-doped NaYF4 oxy-fluoride glass-ceramics

The heat-treatment plays a decisive role in the process of crystal phase precipitation and the microscopic features of the fluoride particles, which determines the optical transmittance and up-conversion luminescence (UCL) properties. In this work, we successfully synthesized Er3+/Yb3+ co-doped UCL transparent oxy-fluoride glass-ceramics (GCs) by precipitation of NaYF4 nanoparticles using a rapid thermal annealing (RTA) treatment with ultra-high heating rate (100 K/s). The particle sizes of NaYF4 nanoprecipitation inside glass-ceramic is only 4–5 nm, which is much smaller than the 40–50 nm particle sizes obtained using normal-heating treatment. The GCs with ultra-small particle sizes provided a very high optical transmittance that is close to that of all-amorphous glass, but the intensity of UCL was similar to that of a sample prepared using a slower heating rate. Finally, under different heat treatment conditions the Er3+/Yb3+ co-doped NaYF4 transparent GCs with different particle sizes can be produced, the color and intensity of UCL were controllable.

Ultrapure single-band red upconversion luminescence in Er3+ doped sensitizer-rich ytterbium oxide transparent ceramics for solid-state lighting and temperature sensing.

Achieving single-band upconversion (UC) is a challenging but rewarding approach to attain optimal performance in diverse applications. In this paper, we successfully achieved single-band red UC luminescence in Yb2O3: Er transparent ceramics (TCs) through the utilization of a sensitizer-rich design. The Yb2O3 host, which has a maximum host lattice occupancy by Yb3+ sensitizers, facilitates the utilization of excitation light and enhances energy transfer to activators, resulting in improved UC luminescence. Specifically, by shortening the ionic spacing between sensitizer and activator, the energy back transfer and the cross-relaxation process are promoted, resulting in weakening of green energy level 4S3/2 and 2H11/2 emission and enhancement of red energy level 4F9/2 emission. The prepared Yb2O3: Er TCs exhibited superior optical properties with in-line transmittance over 80% at 600 nm. Notably, in the 980nm-excited UC spectrum, green emission does not appear, thus Yb2O3: Er TCs exhibit ultra-pure single band red emission, with CIE coordinates of (0.72, 0.28) and color purity exceeding 99.9%. To the best of our knowledge, this is the first demonstration of pure red UC luminescence in TCs. Furthermore, the luminescent intensity ratio (LIR) technique was utilized to apply this pure red-emitting TCs for temperature sensing. The absolute sensitivity of Yb2O3: Er TCs was calculated to be 0.319% K-1 at 304 K, which is the highest level of optical thermometry based on 4F9/2 levels splitting of Er3+ known so far. The integration between pure red UC luminescence and temperature sensing performance opens up new possibilities for the development of multi-functional smart windows.

Upconversion Luminescence Reversible Modulation of Photochromic Ba2YTaO6 Double Perovskite Phosphors Toward Anticounterfeiting Application

AbstractDouble perovskite (DP) phosphors attract extensive attention due to their potential applications in the field of optoelectronics. Photochromism‐induced luminescence modulation can extend their application fields. However, designing and preparing DP phosphors with expected photochromic and luminescent properties is still challenging. Herein, the photochromic Ba2YTaO6: Yb3+, Er3+, Co2+ DP with upconversion luminescence properties is developed. The color of the sample turns from white to pink upon 254 nm UV light irradiation, which is fast fading upon 473 nm laser illumination. The mechanism of photochromism is related to the formation of color centers, and the doping of Co2+ ions is crucial for the improvement of photochromism, which is from the increasing of traps depth, the oxygen vacancies, and the carrier concentration of the matrix caused by Co2+ doping. The upconversion luminescence of Er3+ ions can be reversibly modulated by the photochromic effect, exhibiting excellent reproducibility and high stability. The potential application of photochromic Ba2YTaO6: Yb3+, Er3+, Co2+ phosphor is demonstrated in the field of anticounterfeiting and three‐dimensional (3D) artwork. This work not only offers insight into the photochromic mechanism of DP but also presents guidance for developing other photochromic DP phosphors.

An optical fiber temperature sensor based on fluorescence intensity ratio in Er3+/Yb3+ co-doped Gd2O3 phosphors

A simple optical fiber temperature sensing system based on up-conversion luminescence of Er3+/Yb3+ co-doped Gd2O3 phosphors is proposed and demonstrated for the first time. The Gd2O3: 1 mol% Er3+, 1 mol% Yb3+ phosphors are synthesized by traditional sol-gel method. A sandwich structure fabricated by two fiber connectors, one of which is deposited the fluorescent material cured with ultraviolet adhesive on the surface, is used as the sensing probe. Temperature measurement is achieved using the two green emissions, generated by Gd2O3: 1 mol% Er3+, 1 mol% Yb3+ phosphors, based on the fluorescence intensity ratio (FIR) technique. When the Gd2O3: 1 mol% Er3+, 1 mol% Yb3+ phosphor is excited by the 980 nm laser with the output power of 73 mW, the intense green emissions are observed and change with temperature. The temperature sensing characteristics are experimentally studied in the temperature range from 253 to 413 K, with the maximum absolute sensitivity of 4.15% K−1 at 413 K, the maximum relative sensitivity of 2.28% K−1 at 253 K and the maximum relative error of 0.43%. The proposed optical fiber temperature sensor not only offers excellent reversibility and stability, but also significantly contributes to accurate and remote temperature measurement in harsh environments.

Study of visible upconversion luminescence in Er3+ and Er3+/Yb3+ doped tungsten tellurite glasses

Tellurite-based glasses have produced new, highly significant technologically multipurpose optical glasses. High tungsten content glasses have been investigated for use in nonlinear optics, near-infrared transmission, and as lanthanide ion hosts in optical devices.Thermal and functional studies of the prepared specimence were carried by differential scanning calorimetry (DSC) and Raman spectroscopy. The luminescence analysis of Er3+ and Er3+/Yb3+ co-doped in a novel TeO2-WO3-Na2O glass system is reported in this work. UV–VIS-IR absorption was studied to know the different levels of Er3+/Yb3+. The green and red zones show discernible up-conversion emissions, which are amplified when the samples are co-doped with Yb3 +. Emissions in the near-infrared range have good quantum efficiency.

High-accuracy dual-mode optical thermometry based on up-conversion luminescence in Er3+/Ho3+-Yb3+ doped LaNbO4 phosphors

Due to the non-contact and high sensitivity, optical thermometry based on rare earth doped phosphors has been paid much attention to. Herein, dual-mode optical thermometers are designed using up-conversion luminescence of Er3+/Ho3+-Yb3+ doped LaNbO4 phosphors, which were synthesized for the first time by high-temperature solid-state reaction method. The LaNbO4:1Er3+:10Yb3+ and LaNbO4:1Ho3+:10Yb3+ phosphors exhibit reliable and excellent thermometric performance by combining fluorescence intensity ratio and decay lifetime for self-calibration. Specifically, the maximal relative sensitivities based on fluorescence lifetime were 0.27 %K−1 and 0.33 %K−1 for LaNbO4:1Er3+:10Yb3+ and LaNbO4:1Ho3+:10Yb3+ phosphors, respectively. The maximal relative sensitivity is 1.12 %K−1 when using intensity ratio between thermal coupling energy levels in LaNbO4:1Er3+:10Yb3+ as a detecting signal. Furthermore, the maximal relative sensitivity reaches as high as 0.98 %K−1 when taking advantage of special non-thermal coupling energy levels in LaNbO4:1Ho3+:10Yb3+. These results indicate that Er3+/Ho3+-Yb3+ doped LaNbO4 phosphors possess great potential in self-calibrated optical thermometric techniques.

Upconversion luminescence thermal enhancement from visible to near infrared and improving temperature sensitivity under high temperature using a second-harmonic generation response

Er3+/Nd3+ co-doped and Er3+/Yb3+/Nd3+ triple-doped Cs2Bi2Sr(P2O7)(PO4)2 (CBSP) phosphors are prepared by a solid state reaction, and upconversion luminescence (UCL) from visible to near infrared was investigated under 808, 980, and 1550 nm laser excitation, respectively. UCL of Er3+ and Nd3+ manifests thermal enhancement under 808, 980, and 1550 nm excitation, respectively, except for under 980 nm laser excitation, the Er3+/Nd3+ co-doped sample exhibits UCL thermal quenching of Er3+. This thermal enhancement phenomenon has been discussed and attributed to phonon-assisted energy transfer and electron thermal migration. The relative temperature sensitivities were calculated based on an luminescence intensity ratio technique under 980 and 1550 nm laser excitation, respectively. Under the 1550 nm laser excitation, using a second-harmonic generation response improved the temperature sensitivity in a high temperature range, and the two maximum sensitivities at low and high temperature are obtained as 0.0062 K−1 at 484 K and 0.0111 K−1 at 697 K; 0.0219 K−1 at 303 K and 0.0097 K−1 at 555 K for the Er3+/Nd3+ co-doped and Er3+/Yb3+/Nd3+ triple-doped samples, respectively. UCL thermal enhancement and using a second-harmonic generation response provide a new approach for improving the sensitivity as an optical thermometer under high temperature.

Effect of glass-ceramics network intermediate Al2O3 content on up-conversion luminescence in Er3+/Yb3+ co-doped NaYF4 oxy-fluoride glass-ceramics

Effect of alumina as a glass network intermediate on the up-conversion luminescence (UCL) in NaYF4:Er3+/Yb3+ co-doped oxy-fluoride glass-ceramics (GCs) was investigated. Combinations of smaller NaYF4 nanocrystals (10 and 13 nm) and lower Al2O3 contents (5% and 10%), as well as larger NaYF4 nanocrystals (26 and 40 nm) and higher lower Al2O3 contents (15% and 20%) were prepared after heat-treatment, respectively. The glass network of intermediate partial replacement of SiO2 with Al2O3 was investigated, and the consequence on the response to the up-conversion of the lanthanide ions was also studied. The UCL properties of Er3+ ions were changed in accordance with the addition of Al2O3, the red UCL intensity decreased with an increased Al2O3 concentration, while the green emission intensity showed opposite tendency. Our results showed that adding Al2O3 to 20 mol% is an effective strategy to simultaneous control of the magnitude and luminescence properties of lanthanide ion doped GCs.

Synthesis and up-conversion luminescence of Er3+ and Yb3+ co-doped La14W8O45 phosphors

Pure phase orthorhombic Er3+ and Yb3+ co-doped La14W8O45 up-conversion luminescent materials were successfully prepared by the hydrothermal method combined with calcination treatment. The structures, morphology, and optical properties of the samples were analyzed by X-ray powder diffractometer (XRD), scanning electron microscope (SEM), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), and up-conversion photoluminescence spectroscopy (UPL) with a 980 nm laser. XRD results indicated that the obtained samples are single-phase orthorhombic Er3+ and Yb3+ co-doped La14W8O45 crystals. SEM results showed that the prepared sample exhibits an irregular and melted polyhedral-like morphology with agglomeration in submicron size of particles approximately 50–200 nm. UV–vis DRS results revealed that the La14W8O45 crystal is a direct semiconductor with an optical band gap of 3.84 eV. The prepared Er3+ and Yb3+ co-doped La14W8O45 crystals exhibit strong up-conversion emission peaks at about 526 nm, 548 nm, and 660 nm under 980 nm laser excitation. The intensity of up-conversion luminescence is affected by the Er3+ doping concentration, and concentration quenching will be observed due to the cross-relaxation (CR) process when the Er3+ doping content is above 1%. The pumping power dependence of the luminescence indicated that the up-conversion emissions of samples are excited by a two-photon absorption process. The color coordinates of the samples are located in the green light region.

Achieving power-dependent fluorescence intensity ratio via enhanced photothermal effect in rare-earth and CaCu3TiO12 co-doped alkali niobate ceramics

Controlling the laser power density is one of the major means to bring photothermal conversion phenomenon. However, only a slight temperature enhancement was achieved by exposure to the laser. How to enhance photothermal conversion to develop power-sensitive fluorescence intensity ratio technology becomes a problem. Here, we report an eco-friendly niobate-based ceramic (K 0.25 Na 0.25 NbO 3 ) doped with rare earth ions (Er 3+ , Yb 3+ ) and simultaneously modified with CaCu 3 TiO 4 , exhibiting superior photothermal effect (PTE) and fluorescence intensity ratio (FIR). Thereinto, PTE originating from the up-conversion luminescence of Er 3+ greatly elevates due to the Cu 2+ quenching and Yb 3+ sensitization. Meanwhile, the defects formed by the volatilization of potassium and sodium at high temperature can enhance PTE (70 °C, 0.4 W) and power sensitivity ( S p = 0.61 W -1 ). Under multiple power cycles, stable FIR of the ceramic shows outstanding resistance to temperature in long-term power-dependent tests. Furthermore, this strategy can open opportunities for preparing efficient photothermal conversion ceramics and exploiting PTE for vision-to-tactile sensory conversion.

Influence of the TiO2 nanoparticles on upconversion luminescence of Er3+-doped and Er3+/Yb3+-codoped GeO2-PbO glasses

We report the effect of TiO2 nanoparticles (NPs) on the optical properties of Er3+-doped and Er3+/Yb3+-codoped GeO2-PbO glasses. The present investigation demonstrates the adequate experimental procedure to produce TiO2 NPs in anatase structure (size distribution of TiO2 NPs centered at ∼ 50 nm) that favors the infrared-to-visible frequency upconversion (UC) process in Er3+-doped and Er3+/Yb3+ codoped GeO2-PbO. The samples were produced with the melt-quenching technique; phase transformation from amorphous phase to anatase crystalline structure takes place during the annealing that was performed at 420 °C. The feasibility of obtaining GeO2-PbO glasses with improved UC, due to Er3+ ions located in low symmetry sites promoted by the anatase structure of TiO2 NPs and the UC mechanisms from Yb3+ to Er3+ ions is presented. Photoluminescence growth of about 40% (at ∼ 525 and 545 nm) was observed for the samples doped with Er3+ and TiO2 NPs in comparison with the one doped with Er3+ and without TiO2 NPs. Furthermore, an enhancement of ∼25% (525, 545 e 655 nm) was estimated for the UC intensity of samples codoped with Er3+/Yb3+ and with TiO2 NPs when compared with those without TiO2 NPs. The present investigation covers the lack of the literature related to the investigation of anatase structure of TiO2 NPs in Er3+-doped and Er3+/Yb3+ codoped GeO2-PbO glasses and can be extended to different hosts for different photonics applications.

Energy density capability and upconversion luminescence in Er3+/Yb3+-codoping BNT-based ferroelectric thin films

Smart materials with multiple functions are the preferred materials for technological applications in military, medical, aerospace science and technology, and architecture. However, developing newly single-phase material coupling with multiple functions is still subjects with enormous challenge. Herein, the rare-earth elements Er3+/Yb3+ substitution of lead-free 0.7Bi0·5Na0·5TiO3-0.3Sr0·7Bi0·2TiO3 (BNT-SBT) ferroelectric thin films are designed and fabricated to improve energy storage capability and upconversion luminescence. Optimized BNT-SBT thin films achieves superior discharged energy density of 52.4 J/cm3 with high efficiency of 70.2%, as well as excellent temperature stability (RT to 150 °C) and fatigue endurance (107 circles). Additionally, the emission color of BNT-SBT thin films could be controlled through changing Yb3+ ion concentrations. More importantly, the maximum sensor sensitivity of the Er3+/Yb3+ codoped BNT-SBT thin films could reach 0.0049 K−1 at 363 K. This contribution paves a novel avenue for preparing lead-free multifunctional ferroelectric thin films, which are interested in potential application in the field of optoelectronic devices.

Upconversion Luminescence of Er3+ Ions from Barium Titanate Xerogel Powder and Target Fabricated by Explosive Compaction Method

Upconversion Luminescence of Er3+ Ions from Barium Titanate Xerogel Powder and Target Fabricated by Explosive Compaction Method

Effect of fluorine substitution on the structure and spectral property of fluorotellurite glass for upconversion luminescence thermometry

A series of TeO2–ZnO–ZnF2–La2O3–Yb2O3–Er2O3 glasses (TZL) with different amount of ZnF2 were prepared by the melt quenching method. The effects of fluorine concentration on the density, refractive index, thermal behavior, and vibrational characteristic of TZL glasses were analyzed. The Judd-Ofelt (J-O) theory was employed to study the spectroscopic properties of Er3+ ions. By using the J-O intensity parameters the spontaneous radiative transition probabilities, fluorescence branching ratios, and radiative lifetimes of some concerned transitions of Er3+ were predicted. The potential of TZL glasses for the gain around 1.5 μm was briefly evaluated. Moreover, the upconversion luminescence was investigated under the excitation of 980 nm laser. The dependence of luminescence intensity on pump power revealed that the upconversion luminescence of Er3+ in TZL glasses are contributed by two-photon involved energy transfer processes. Furthermore, the adjacent upconversion green emissions of Er3+ ions were used to temperature sensing based on the fluorescence intensity ratio (FIR) technique. High absolute sensitivity and resolution have been obtained, which indicate that the TZL glasses are potential materials for optical fiber temperature sensors.

Effects of A-site cations and the substitution site on the upconversion luminescence of Er3+ in the zirconate perovskite series

We investigated the upconversion luminescence (UCL) properties of AZrO3 (A = Ca, Sr, and Ba) perovskite compounds co-doped with Er3+ and Yb3+ in relation to the change in the crystal structure from orthorhombic to cubic. The dopants selectively substituted the A- and B-site ions in the ABO3-type perovskite structure. Upon excitation at 980 nm, we observed the two main UCL features at 545 nm and 660 nm, which depended strongly on the ion occupying the A-site and whether the dopant substituted the ion occupying the A- or the B-site. The intensity of the UCL was found to be maximized for A = Ca because this ion resulted in the lowest crystal symmetry of the host material. The dependence of the UCL on the substitution site (A or B) was significant for A = Sr, in accordance with the sizable difference in the lattice constants of host materials doped at either the A-site or B-site. Our results showed that the crystal symmetry of the host materials and the related local lattice symmetry could play an important role in determining the emission properties of Er3+ ions in perovskite crystals.

Generation of Pure Green Up-Conversion Luminescence in Er3+ Doped and Yb3+-Er3+ Co-Doped YVO4 Nanomaterials under 785 and 975 nm Excitation.

Materials that generate pure, single-color emission are desirable in the development and manufacturing of modern optoelectronic devices. This work shows the possibility of generating pure, green up-conversion luminescence upon the excitation of Er3+-doped nanomaterials with a 785 nm NIR laser. The up-converting inorganic nanoluminophores YVO4: Er3+ and YVO4: Yb3+ and Er3+ were obtained using a hydrothermal method and subsequent calcination. The synthesized vanadate nanomaterials had a tetragonal structure and crystallized in the form of nearly spherical nanoparticles. Up-conversion emission spectra of the nanomaterials were measured using laser light sources with λex = 785 and 975 nm. Importantly, under the influence of the mentioned laser irradiation, the as-prepared samples exhibited bright green up-conversion luminescence that was visible to the naked eye. Depending on the dopant ions used and the selected excitation wavelengths, two (green) or three (green and red) bands originating from erbium ions appeared in the emission spectra. In this way, by changing the UC mechanisms, pure green luminescence of the material can be obtained. The proposed strategy, in combination with various single-doped UC nanomaterials activated with Er3+, might be beneficial for modern optoelectronics, such as light-emitting diodes with a rich color gamut for back-light display applications.

Upconversion Luminescent Humidity Sensors Based on Lanthanide-Doped MOFs

Lanthanide-doped metal-organic frameworks (Y/Yb/Er-MOF) were synthesized by a low-cost solvothermal method. The obtained Y/Yb/Er-MOF shows the cooperative upconversion luminescence of Yb3+ and upconversion luminescence of Er3+ (Yb3+-sensitized) irradiated by a continuous wave 980 nm laser. In order to explore the potential application of Y/Yb/Er-MOF in relative humidity (RH) sensors, the RH responsiveness of Y/Yb/Er-MOF was investigated by measuring the intensity changes of upconversion luminescence. The Y/Yb/Er-MOF possesses two luminescence centers, in which Yb3+ forms emission at 500 nm through the cooperative luminescence effect, and Er3+ achieves 660 nm emission through excited state absorption and successive energy transfer from Yb3+. Hence, the ratio meter luminescence sensor for RH is constructed based on Y/Yb/Er-MOF. The results show that the response of Y/Yb/Er-MOF to RH presents a linear relationship in the range of 11–95%. The cycle stability of Y/Yb/Er-MOF responses to RH was investigated with the intensity changes of upconversion luminescence, and the recovery ratio was more than 93% each time. Therefore, the Y/Yb/Er-MOF is a humidity-sensitive material with great potential for applications such as humidity sensors.

Improved photoluminescence and multi-mode optical thermometry of Er3+/Yb3+ co-doped (Ba,Sr)3Lu4O9 phosphors

Contactless optical thermometers have attracted extensive attentions for applications in scientific research and technological fields due to their apparent advantages. Herein, a novel sequence of Ba 3-x Sr x Lu 4 O 9 (B 3-x S x LO):Er 3+ /Yb 3+ phosphors were successfully prepared to investigate the temperature sensing property. By establishing energy transfer from Yb 3+ to Er 3+ and regulating the local lattice environment, up-conversion luminescence of Er 3+ is dramatically improved when excited by 980 nm laser. This can effectively promote signal-noise ratio and reduce the errors in temperature detection. Furthermore, a multi-mode optical thermometry, which includes the fluorescence intensity ratio (FIR) from two thermally coupled levels of 2 H 11/2 / 4 S 3/2 , FIR based on non-thermally coupled system of 2 H 11/2 / 4 F 9/2 and fluorescence lifetime of 4 S 3/2 state of Er 3+ , was explored systematically. The fabricated samples exhibit the superior temperature measurement performances containing wide temperature-sensing range, superior signal discriminability, high sensitivity and favorable repeatability, indicative of the enormous utilization prospects of B 3-x S x LO:Er 3+ /Yb 3+ for thermometry.