Luminescence Intensity Ratio Research Articles

Chromatic tuning of upconversion emission upon dual infrared wavelength co-excitation in Er3+ doped Ba3Lu4O9 phosphor

Emission color change of the upconversion luminescence materials is often required for applications in optical anti-counterfeiting, laser lighting, and 3D displays. In this work, we developed a new route for chromatic tuning of upconversion emission upon two wavelength co-excitation by changing excitation power density. The proposed route was used for Er3+ single-doped Ba3Lu4O9 phosphor which was derived from a traditional solid-state reaction. The crystal structure of the obtained Ba3Lu4O9:Er3+ phosphor was characterized by X-ray diffraction and Rietveld refinement modeling. Under individual excitation of 980 or 1550 nm, it was found that the luminescence intensity ratio of red to green changes slightly with respectively increasing excitation power density (working current of the laser) of 980 or 1550 nm laser. However, upon both 980 and 1550 nm co-excitation at the same time and by adjusting the excitation power density of one laser amongst the two lasers, the luminescence intensity ratio of red to green changes greatly with increasing excitation power density. The change of luminescence intensity ratio of red to green implies the upconversion emission color tuning. The mechanism for the color tuning was discovered. It was found that with changing excitation power density the ratio of red to green changed greatly when the phosphor was irradiated by 980 and 1550 together, but the ratio of red to green changed slightly when the phosphor was irradiated individually by 980 or 1550. It is proved that it is feasible to turn color by the method of two infrared wavelengths excitation.

Temperature Changes in Luminescence of Mixed Complexes of Terbium and Samarium with Organic Ligands Based on 2,2-bipyridyldicarboxamides

Solutions in acetonitrile of three mixed complexes of rare earth elements (terbium and samarium) with organic ligands with various pyridine substituents were studied in this work. The ratios of ligands and metals in the resulting complexes were determined, and the stability constants of samarium complexes were calculated using the spectrophotometric titration method. Measurements of absorption, emission and excitation spectra of luminescence, luminescence kinetics of solutions of mixed complexes of rare earth elements with an excess of metal relative to the ligand were carried out at various temperatures in the range 298–328 K. An increase of luminescence intensity of a samarium ion in complex upon heating has been discovered for the first time. The dependences of the luminescence quantum yield and lifetime of mixed complexes on temperature were obtained. A thermometric parameter — the ratio of the integral luminescence intensities of samarium and terbium ions — was proposed, and the temperature sensitivity coefficient of this parameter was determined for different complexes.

Ultrasensitive and Adjustable Nanothermometers Based on Er3+-Sensitized Core@Shell Nanoparticles for Use in the First Biological Window.

In recent years, intensive research has focused on lanthanide-doped nanoparticles (NPs) used as noncontact temperature sensors, particularly in nanomedicine. These NPs must be capable of excitation and emission within biological windows, where biological materials usually show better transparency for radiation. In this article, we propose that NPs sensitized with Er3+ ions can be applied as temperature sensors in biological materials. We synthesized the NPs through a reaction in high-boiling solvents and confirmed their crystal structure and the formation of core@shell NPs by using X-ray diffraction, high-resolution transmission electron microscopy, and element distribution mapping within the NPs. NaErF4@NaYF4, NaYF4:12.5% Er3+, 2.5% Tm3+@NaYF4, NaYF4:7.5% Er3+@NaYF4, and NaYF4:12.5% Er3+, 2.5% Ho3+@NaYF4 exhibited intense upconversion (UC) emission under 1532 nm laser excitation detectable also in the whole human blood. We propose that this UC results from energy transfer between Er3+ ions and from Er3+ to Tm3+ or Ho3+ codopants. To determine the mechanism of UC, we measured the dependence of the emission band intensities on the laser power densities. Importantly, we also analyzed the temperature-dependent emission of the NPs within the 295-360 K range. Based on the collected emission spectra, we calculated the luminescence intensity ratios (LIRs) of the emission bands to assess their potential for optical temperature sensing. The temperature-sensing properties varied with the concentration of Er3+ ions and the presence of additional Tm3+ or Ho3+ codopants. Depending on the NP composition and the emission bands used for luminescence ratio calculations, the maximum relative temperature sensitivity ranged from 4.55%·K-1 to 1.12%·K-1, with temperature resolution between 0.05 and 2.53 K at room temperature. Finally, as proof of using NPs as temperature sensors in biomedicine, we successfully measured the temperature-dependent emission of NaYF4:7.5% Er3+@NaYF4 NPs dispersed in whole blood under 1532 nm excitation. We demonstrated that the ratio of Er3+ ion emission bands changes with temperature, indicating that these NPs have potential applications in temperature sensing within biological environments. We also confirmed the properties of NPs as temperature sensors by measuring the temperature reading uncertainty and the repeatability of the LIR readings during heating-cooling cycles, thereby confirming the excellent properties of the studied systems as temperature sensors.

Ultra-sensitive low-temperature luminescent thermometry based on Boltzmann behavior of the Stark sub-levels of Pr3+

The cryogenic sensor is critical for numerous applications such as cryobiology, aerospace space probes, and solid-state superconducting quantum technology. However, it is still a challenge to operate at temperatures below 100 K using luminescent intensity ratio (LIR) thermometers with typical thermal coupling levels based on the Boltzmann mechanism. In this work, a sensitive low-temperature luminescence thermometry approach has been developed utilizing Boltzmann behavior of the Stark sub-levels of Pr3+. Spectral Stark-splitting feature of the 1D2 multiplet of Pr3+ was observed in CaNb2O6: Pr3+ phosphor, and the luminescence intensity ratio (LIR) of high state (Stark sub-level (2)) and low state (Stark sub-level (0)) of 1D2 was employed for temperature sensing, resulting in a notable relative sensitivity (Sr) of 11.3 % K−1 at 60 K. In addition, the intervalence charge transfer (IVCT)-based strategy improves the temperature sensitivity above room temperature with maximum Sr up to 1.54 % K−1 at 420 K. This work consistently demonstrate high sensitivity at low temperature, indicating potential applications in cryogenic temperature sensor. These results provide a route to the development of luminescent thermometers with a high sensitivity at low temperatures and a wide range of operating temperatures.

Quantum yield and thermal sensitivity of SrGd2O4:Yb, Tm up-conversion nanoparticles

Luminescence thermometry is an effective method for temperature measurements using the remote operating mode. In this work, a series of Tm3+ (1 at%) and Yb3+ (2, 4, and 6 at%) ions doped SrGd2O4 up-conversion (UC) nanoparticles were synthesized by the modified sol-gel method, and fully characterized toward optimization of their composition and optical characteristic. Crystallization of single-phase nanoparticles with homogeneous doping was confirmed by XRPD, TEM/HRTEM, and STEM/EDS analysis in all samples, independently of their stoichiometry. The UC emissions recorded under 976 nm excitation revealed typical Tm3+ transitions, showing that the optimal sensitizer doping concentration is 4 at%. For this sample, a lifetime of 342 μs, and a total quantum yield of 1.12 % were determined at room temperature for the emission observed in the Vis part of up-conversion spectra. The temperature-dependent emission spectra, measured from 263 to 363 K, implied its excellent temperature-sensing capabilities. The luminescent intensity ratio (LIR) was employed for blue I479/485 and IR I795/807 Tm3+ emissions. The absolute and relative temperature sensitivity continuously decreases with the increase of the temperature, showing the values of 4.05x10−3 K-1 and 0.41 % K−1 (for blue) and 3.8x10−3 K-1 and 0.31 % K−1 (for IR) at the temperature of 300 K. The results indicate that SrGd2O4 doped with 4 % Yb3+ and 1 % Tm3+ may be employed for reliable temperature measurement over an investigated temperature range.

Up-conversion luminescence and multimodal temperature sensing behaviors in the visible and infrared region of Er3+ and (Er3+, Yb3+) ions in Ca3Ta2Ga3O12 phosphors

Ca3Ta2Ga3O12 - CTGG ceramic phosphors doped with xEr3+ ions, x = (0.1, 1, 3, 5, 7, and 9 at.%) and (5Er, yYb), y = (0.1, 1, 3, 5, and 7 at.%) were investigated. The emission spectra of Er3+ ions were measured under 973 nm and 1550 nm excitations and the optimal concentrations of Er3+ and (Er3+, Yb3+) ions allowing to obtain the maximum emission intensities in the visible range were determined to be 5Er and (5Er, 5Yb), respectively. The best results in terms of correlated color temperature (CCT) and color purity (CRI) were obtained under λex = 973 nm. High values of CCT (between 5000 K and 6000 K) and CRI (in the range of 80 - 92) parameters indicate their potential as efficient materials for white light-emitting diode devices. The temperature dependence of Er3+ luminescence in 5Er:CTGG and (5Er, 5Yb):CTGG samples was investigated by the luminescence intensity ratio for different thermally coupled (TCLs) and non-thermally coupled (NTCLs) levels and the fluorescence lifetime. The highest value of the relative thermal sensitivity parameter (Sr) for 5Er:CTGG sample, Sr = 1.41 % K-1 at 325 K, was obtained from TCLs (2H11/2/4S3/2) under λex = 973 nm. For (5Er, 5Yb):CTGG sample, the highest values of Sr were obtained as follows: Sr = 1.77 % K-1 at 325 K from TCLs (2H11/2/4S3/2), Sr = 1.19 % K-1 at 150 K from TCLs (4I13/2(2)/4I13/2(3)), and Sr = 0.62 % K−1 at 450 K from 4S3/2 lifetime, under λex = 973 nm, and Sr = 1.23 % K-1 at 325 K from TCLs (2H11/2/4S3/2) and Sr = 1.21 % K-1 at 325 K from NTCLs (2H11/2/4F9/2) under λex = 1550 nm. These results indicate that 5Er:CTGG and (5Er, 5Yb):CTGG ceramic phosphors have high potential for applications in the field of optical temperature sensors.

Optically stimulated luminescence and radiophotoluminescence in NaMgF3:Eu nanoparticles

Optically stimulated luminescence and radiophotoluminescence were observed in NaMgF3:0.1%Eu nanoparticles synthesised via a hydrothermal technique. X-ray irradiation created F-centres, and subsequent optical stimulation at 420 nm released the electrons and electron-hole recombination produced Eu2+ emissions. The integrated optically stimulated luminescence intensity was linear up to 180 Gy. Photoluminescence was observed from Eu2+ and Eu3+ valences, whereas optically stimulated luminescence only occurred via the Eu2+ sites. X-ray irradiation also resulted in Eu3+ → Eu2+ and O2− → O− radiophotoluminescence effects, where the luminescence intensity ratio, RPLEu2+/RPLO2−, indicated a large detection range (>1 kGy). The observation of optically stimulated luminescence in lanthanide-doped near tissue-equivalent NaMgF3 nanoparticles has potential applications including as high spatial resolution two- and three-dimensional dosimeters for radiotherapy dose verification and validation. Radiophotoluminescence from oxygen-related centres and Eu is advantageous because it can provide a record of the dose history as well as an additional measure of the dose.

Achieving Near-Infrared Highly Sensitive Temperature Sensing in Lanthanide-Doped Lead-Free Double Perovskite NaLaMgWO6 with Significant Thermal Enhancement.

The significant temperature response of lanthanide-doped up-conversion luminescent materials is typically characterized by a severe thermal quenching of the luminescence intensity at elevated ambient temperatures, which severely restricts materials' capability in temperature sensing. Herein, the influence of matrix phonon properties on the remarkable thermal enhancement effect in the thermosensitive material NaLaMgWO6:Yb3+/Nd3+ is reported. It is elucidated that achieving a significant thermal enhancement of Nd3+ with a higher phonon energy oxide matrix is easier than a halide matrix, which has lower phonon energy by comparison with previous findings. Interestingly, the emission of thermally related levels gets enhanced to various extents through phonon-assisted thermal population. In light of this, a three-model thermometer is constructed based on luminescence intensity ratio (LIR) technology. Given that Sr and ΔE possess a positive correlation, it is feasible to acquire greater temperature monitoring sensitivity Sr in Nd3+, which has a larger ΔE. At 313 K, this thermometry model may achieve a maximum sensitivity of 2.84%·K-1. This work not only provides guidance for the selection of efficient near-infrared up-conversion material but also opens up a prospect for the realization of ultrasensitive thermally coupled luminescent thermometers.

Improved thermometry via luminescence lifetime ratio of Er3+ and Tm3+ operated in the biological window

The luminescent intensity ratio of Lanthanide-doped nanocrystals has been widely used for non-contact thermometry but is still facing difficulties in biological applications due to spectrum distortion caused by tissues. Lifetime-based thermometry is the best alternative to other typical thermometry methods. However, its main drawback is the limited sensitivity. This paper introduces an innovative method known as luminescence lifetime ratio, which enhances luminescence thermometry by combining two emission bands with opposite decay behaviors with temperature. As a proof of concept, a core-shell structure separately containing Tm3+ and Er3+ was synthesized and exhibited two strong emission bands centered at 800 nm and 1530 nm, which are located in the NIR-I and NIR-III biological windows. The commonly used LIR thermometer, an Er/Yb co-doped NaYF4 sample, was also synthesized for comparison. By using chicken tissues of varying thicknesses (1 mm and 3 mm), it was revealed that the deep-tissue penetration and accuracy in biological environments of luminescence lifetime ratio are evidently improved than the widely-used technique of luminescence intensity ratio, although the relative sensitivity of is not much better. In summary, the luminescence lifetime ratio technique enables novel and more accurate temperature sensing within the wavelength range that is suitable for biological applications.

Single-Band Ratiometric Thermometry Strategy Based on the Completely Reversed Thermal Excitation of O2- → Eu3+ CTB Edge and Eu3+ 4f → 4f Transition.

Single-band ratiometric (SBR) strategies present huge potential in the field of luminescence intensity ratio thermometry owing to their excellent signal discrepancy and appealing simplicity. Herein, we employ the approach of Na replacing Li in the LiYGeO4:Eu3+ phosphor to regulate the thermal stability of the O2- → Eu3+ charge-transfer band (CTB) and obtain significant thermal enhancement of luminescence under CTB edge excitation. Combined with the obvious thermal quenching of luminescence under ground-state absorption excitation, the ratio of the single emission band increases by 18 times when the temperature increases from 300 to 570 K. Therefore, such excitation-wavelength-dependent diametrically opposite thermal luminescence behaviors enabled SBR thermometry, whose maximum relative sensitivity can reach up to 3.6% K-1. We demonstrate that the O2- → Eu3+ CTB thermal red-shifts and enhancements are particularly attractive for SBR thermometry with high sensitivity by utilizing the diametrically reversed thermal excitation between the O2- → Eu3+ CTB edge and the 4f → 4f transition of Eu3+. These advances have opened up a novel horizon for the development of high relative sensitivity and performance of the SBR thermometry strategy.

Visible to infrared wide wavelength range luminescence of Sr2LaNbO6: Yb3+/Nd3+/Ho3+ phosphor under 808/980 nm excitation and temperature sensing application

Here, the Sr2LaNbO6: Yb3+/Nd3+/Ho3+ phosphors are prepared through solid-state route. The upconversion (UC)/downshifting (DS) luminescence and temperature performances of all samples are investigated in detail. Under 808 nm excitation, the infrared emission band (∼2000 nm) of Ho3+ ions is obtained. Especially, the energy transfer process of Nd3+ → Yb3+ → Ho3+ has increased the emission intensity of ∼2000 nm. Moreover, the infrared emission band presents thermal enhancement. Under 980 nm excitation, the UC emission band 500–960 nm is investigated. The green and red light of Ho3+ ion, near infrared light of Nd3+ ions are achieved. In addition, the possible luminescence mechanism of Sr2LaNbO6: Yb3+/Nd3+/Ho3+ phosphor is discussed. At last, the optical temperature sensing characteristics of the phosphor are studied according to the luminescence intensity ratio (LIR) technology. The maximum relative sensitivity of Sr2LaNbO6: Yb3+/Nd3+/Ho3+ reaches 5.476 % K−1 at 293 K. These results prove that the Sr2LaNbO6: Yb3+/Nd3+/Ho3+ phosphor presents the luminescence in infrared and visible range. The Sr2LaNbO6:Yb3+/Nd3+/Ho3+ phosphor also can be applied to design optical temperature sensor.

Structure-Dopant Concentration Relations in Europium-Doped Yttrium Molybdate and Peak-Sharpening for Luminescence Temperature Sensing.

A set of Eu3+-doped molybdates, Y2-xEuxMo3O12 (x = 0.04; 0.16; 0.2; 0.4; 0.8; 1; 1.6; 2), was synthesized using a solid-state technique and their properties studied as a function of Eu3+ concentration. X-ray diffraction showed that the replacement of Y3+ with larger Eu3+ resulted in a transformation from orthorhombic (low doping concentrations) through tetragonal (high doping concentrations), reaching monoclinic structure for full replacement in Eu2Mo3O12. The intensity of typical Eu3+ red emission slightly increases in the orthorhombic structure then rises significantly with dopant concentration and has the highest value for the tetragonal Y2Mo3O12:80mol% Eu3+. Further, the complete substitution of Y3+ with Eu3+ in the case of monoclinic Eu2Mo3O12 leads to decreased emission intensity. Lifetime follows a similar trend; it is lower in the orthorhombic structure, reaching slightly higher values for the tetragonal structure and showing a strong decrease for monoclinic Eu2Mo3O12. Temperature-sensing properties of the sample with the highest red Eu3+ emission, Y2Mo3O12:80mol% Eu3+, were analyzed by the luminescence intensity ratio method. For the first time, the peak-sharpening algorithm was employed to separate overlapping peaks in luminescence thermometry, in contrast to the peak deconvolution method. The Sr (relative sensitivity) value of 2.8 % K-1 was obtained at room temperature.

Optical thermometry using efficient upconversion luminescence in Er3+ self-sensitized NaYS2 under multi-wavelength excitation

Herein, a series of Er3+ self-sensitized NaYS2 phosphors are synthesized by the solid-gas reaction method for a novel upconversion luminescence thermometer. Er3+ possesses abundant excited state energy levels in the near-infrared region, enabling efficient upconversion luminescence by absorbing different near-infrared wavelength light. Compared to 980 nm excitation, the emission intensity is enhanced by nearly an order of magnitude under 1532 nm excitation, which can be attributed to the larger absorption cross-section of 4I13/2 and stronger absorption efficiency for Er3+. Based on the luminescence intensity ratio technique, the optical thermometry behaviors of NaYS2:Er3+ under different wavelength excitation are evaluated by employing the thermally coupled energy levels of 2H11/2/4S3/2. It can be deduced that the excitation wavelength has no significant effect on the temperature sensing parameters. Compared to other typical upconversion luminescence thermometers, NaYS2:Er3+ thermometer exhibits not only excellent sensitivity performance but also high upconversion luminescence efficiency, which is expected to be applied in wide-temperature-range and highly-sensitive temperature sensing.

A novel Y/Eu co-doped Ln-MOF for ratiometric luminescent thermometer of high sensitivity

Lanthanide metal-organic frameworks (Ln-MOFs) co-doped by mixed lanthanide ions is a preeminent candidate for ratiometric luminescence thermometers. In recent years, there are few studies on the synthesis of such MOFs by introducing Ln3+ ions of no luminescent properties such as Y3+. Herein, a novel Y/Eu co-doped Ln-MOF (Y0.95Eu0.05NDPA, H4NDPA = 5,5′-naphthalene-1,4-diyl-diisophthalic acid) was synthesized via solvothermal methods, which showed good phase purity and thermal stability. Compared with EuNDPA, the Y3+ ions in Y0.95Eu0.05NDPA dilute the molar concentration of Eu3+, causing the emerge of ligand emission band. The luminescence intensity ratio of organic ligands and Eu3+ owns a good exponential dependence on temperature variation. As investigated, Y0.95Eu0.05NDPA owns the merits including a wide temperature sensing range (303–423 K), high relative sensitivity (3.04 %·K-1 at 423 K), good spectral repeatability (>92 %) and distinct emission color change from red to blue. This novel Y0.95Eu0.05NDPA ratiometric thermometer is expected to promote the application and development of dual-emission MOF materials in the field of microelectronic temperature measurement.

High-sensitivity luminescent temperature sensors: MFX:1%Sm2+ (M = Sr, Ba, X = Cl, Br).

The use of lanthanide luminescence has advanced the field of remote temperature sensing. Luminescence intensity ratio methods relying on emission from two thermally coupled energy levels are popular but suffer from a limited temperature range. Here, we present a versatile luminescent thermometer: Ba(Sr)FBr(Cl):Sm2+. The Sm2+ ion benefits from multiple thermally coupled excited states to extend the temperature range and has strong parity-allowed 4f6→4f55d1 absorption to increase brightness. We conduct a comparative analysis of the temperature sensing performance of Sm2+ in BaFBr, BaFCl, SrFBr, and SrFCl and address the role of concentration, host, and Boltzmann equilibration. Different thermal coupling schemes, 5D1-5D0 and 4f55d1-5D0, and temperature-dependent lifetimes enable accurate sensing between 350 and 800 kelvin. Differences in 4f55d1-5D0 energy gap allows optimization for a temperature range of interest. This type of Sm2+-based thermometer holds great potential for temperature monitoring in the wide and relevant range up to 500°C.

Upconversion nanoparticles-CuMnO2 nanoassemblies for NIR-excited imaging of reactive oxygen species in vivo

Here, we designed a ratiometric luminescent nanoprobe based on lanthanide-doped upconversion nanoparticles-CuMnO2 nanoassemblies for rapid and sensitive detection of reactive oxygen species (ROS) levels in living cells and mouse. CuMnO2 nanosheets exhibit a wide absorption range of 300–700 nm, overlapping with the visible-light emission of upconversion nanoparticles (UCNPs), resulting in a significant upconversion luminescence quenching. In an acidic environment, H2O2 can promote the redox reaction of CuMnO2, leading to its dissociation from the surface of UCNPs and the restoration of upconversion luminescence. The variation in luminescence intensity ratio (UCL475/UCL450) were monitored to detect ROS levels. The H2O2 nanoprobe exhibited a linear response in the range of 0.314–10 μM with a detection limit of 11.3 nM. The biological tests proved the excellent biocompatibility and low toxicity of obtained UCNPs-CuMnO2 nanoassemblies. This ratiometric luminescent nanoprobe was successfully applied for the detection of exogenous and endogenous ROS in live cells as well as in vivo ROS quantitation. The dual transition metal ions endow this probe efficient catalytic decomposition capabilities, and this sensing strategy broadens the application of UCNPs-based nanomaterials in the field of biological analysis and diagnosis.

Boltzmann thermometry: Eu3+-doped monoclinic Y2O3 and Y2O3@SiO2 nanoparticles

During last decade optical thermometry has gained considerable attention due to the possibility to determine temperature remotely in cases when traditional contact methods fail. The most widespread type of optical temperature sensors is based on monitoring luminescence intensity ratio between transition originated from thermally coupled energy levels. Eu3+ ions own the largest energy gap between thermally coupled 5D1 and 5D0 energy levels among all lanthanides, which guarantees a high thermal sensitivity of Boltzmann-type thermometry. Here, uncoated m-Y2O3:Eu3+ and core-shell m-Y2O3:Eu3+@SiO2 nanophosphors have been successfully utilized as ratiometric thermal sensors within the 298–873 K range. It was shown that the calculation method (integral or peak intensities) only slightly affects thermal sensitivity. SiO2 coating significantly enhances emission intensity and increases lifetime, but has no noticeable effect on thermal sensitivity. m-Y2O3:Eu3+ nanophosphor has the best thermometric characteristics of Sr = 0.96 % K-1 at 373K and δT = 0.5 K.

Up-Conversion Luminescence and Optical Temperature Sensing of Tb3+, Yb3+, Er3+ Doped (Gd, Y, Lu)2O2S Series Phosphors

The phase analysis, luminous intensity, and luminescence lifetime of different doping concentrations of Tb3+ (1 mol %–11 mol %), Yb3+ (9 mol %–54 mol %), Er3+ (0.1 mol %–1.1 mol %) ions and different introduction concentrations of Y3+ (1 mol %–6 mol %) and Lu3+ (0.5 mol %–3 mol %) of Gd2O2S series phosphors were studied systematically. In addition, the energy transfer model of Tb3+-Yb3+-Er3+ was established by analyzing the changes of luminous intensity and luminescence lifetime of novel (Gd, Y, Lu)2O2S phosphors co-doped Tb3+, Yb3+ and Er3+ which were prepared by the coprecipitation-high temperature solid-state reaction method. The luminescence intensity ratio equations of the sample excited by 980 nm was obtained at 313–553 K. And the absolute sensitivities were 0.0033 (313 K). This work is of reference value to the study of the mechanism of up-conversion system.

Toward Ultra-High Sensitivity Optical Thermometers and Bright Yellow LEDs Based on Phonon-Assisted Energy Transfer in Rare Earth-Doped La2ZnTiO6 Double Perovskite.

Double perovskites, a class of ceramic oxides with unique crystal structures and diverse physical properties, show promise for various technological applications including solar cells, photodetectors, and light-emitting diodes (LEDs). Despite limited research on rare earth-doped double perovskites, leveraging their ultrahigh luminous efficiency to achieve bright yellow LED emission and addressing energy transfer challenges between Yb3+ and Nd3+ ions in double perovskite La2ZnTiO6 with moderate phonon energy are explored in this work. Through phonon-assisted energy transfer, an ultrasensitive optical thermometer covering a wide temperature range is developed by utilizing the different temperature responses of Er3+ emission in the visible light region and Nd3+ emission in the near-infrared region based on the luminescence intensity ratio (LIR). All the results demonstrate that the rare earth (Yb-Er, Yb-Nd, and Yb-Nd-Er)-doped La2ZnTiO6 phosphors can be effectively utilized for ultrabright LED illumination and ultrahigh sensitivity self-calibrated temperature sensing. This research underscores the significance of phonon-assisted energy transfer in improving material properties and provides valuable insights for the advancement of multifunctional materials.

An energy transfer strategy towards versatile sensing applications from Cr3+ and Yb3+ codoped near infrared phosphors

Near-infrared (NIR) phosphors have garnered notable attention for their extensive applications in anti-counterfeiting, optical imaging, non-invasive medical diagnosis and detection. Nevertheless, the quest for NIR phosphors with outstanding detection and sensing capabilities remains a challenge. In this study, we have successfully prepared Ga1.6Mg0.2Ge0.2O3:Cr3+,Yb3+ NIR phosphors by codoping and substitutation strategies. When incorporated into polydimethylsiloxane films, these phosphors demonstrated a direct correlation between luminescence intensity ratio and applied stress under 450 nm excitation. Moreover, variations in luminescence spectra occurred with different compositions and concentrations of liquids coated on the film, facilitating both force measurement and composition analysis. Furthermore, a NIR phosphor-converted light-emitting diode (pc-LED) was fabricated by integrating phosphor with a blue LED chip, exhibiting excellent performance. Utilizing the prepared NIR pc-LED as a light source, we facilitated non-destructive imaging, night vision, and anti-counterfeiting applications with an infrared camera. These findings suggest that the synthesized NIR phosphors possess hold promise for diverse detection and sensing applications.