Relative Sensitivity Sr Research Articles

Tb3+/Dy3+ doped glass ceramics containing Bi2Ti2O7 crystal phases for luminescence and temperature sensing

Melt-curing-crystallization was used to synthesized a series of Tb3+/Dy3+ doped glass ceramics (GCs) with a crystalline phase of Bi2Ti2O7. The optimal treatment with heat conditions is 570 °C for 60 min. The emission spectra of Tb3+-Dy3+ co-doped GCs contain four separate emission peaks at 485 nm (5D4 →7F6 and 4F9/2 → 6H15/2), 545 nm (5D4 →7F5), 575 nm (4F9/2 →6H13/2) and 612 nm (5D4→7F3), proving existence of an energy transfer Dy3+→Tb3+. Concentration quenching dominated by dipole-dipole interactions appears as concentration of Dy3+ exceeds 0.4%, So the optimum dopant concentration is 0.4% Dy3+. Thermal quenching activation energy (ΔE) is 0.320 eV for Tb3+ at 545 nm and 0.383 eV for Dy3+ at 575 nm. The Tb3+-Dy3+ co-doped GCs showed a highest absolute sensitivity Sa of 7.96 ×10-2 K-1 and a greatest relative sensitivity Sr of 3.19% K-1 at temperatures between 298 K and 458 K, indicating GCs has potential application value in the field of temperature sensing.

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.

Luminescence performance, temperature sensing characteristics and Judd-Ofelt theory analysis of Y2MoO6:Er3+/Yb3+/Li+ upconversion phosphors

A series of Y2MoO6:0.01Er3+/0.09Yb3+ upconversion phosphors doped with different concentrations of Li+ ions (0.05, 0.10, 0.15, 0.20, 0.25, and 0.30 mol) were prepared by the high temperature solid phase reaction method, and their physical phase structures and upconversion luminescence were analyzed. At the excitation wavelength of 980 nm, the addition of Li+ sharply increased the upconversion luminescence intensity. With the increase of Li+ ion content, the luminescence intensity first increases and then decreases. When the doping amount reaches 0.25 mol, the luminescence intensity reaches the maximum, and the sample emits green light in the two-photon process. Y2MoO6:0.01Er3+/0.09Yb3+/0.25Li+ exhibits excellent temperature sensing properties. Its absolute sensitivity Sa reaches up to 0.012 K-1, the relative sensitivity Sr is 0.017 K-1 and the measurement error δT is less than 0.3 K at room temperature. Its temperature sensing performance is far superior to similar materials. In addition, Judd-Ofelt theory calculations revealed that in comparison with Y2MoO6:0.01Er3+/0.09Yb3+, its Ω2 increased from 0.56×10-20 cm2 to 3.68×10-20 cm2 , and the spectroscopic quality factor Ω4/Ω6 ratio reached 4.09, which is much higher than that of the other fluorescent materials. The main reason is that Li+ replaces the Y3+ ion lattice site, causing lattice distortion and reducing the lattice symmetry around the active ion. The increase in asymmetry increases the possibility of spontaneous radiative transitions. It is shown that the prepared upconversion luminescent materials have potential applications in the field of solid-state lasers and optical sensing.

Upconversion luminescence and thermosensitive properties of NaGd(PO3)4:Yb3+/Er3+

High-sensitivity optical temperature measurement has attracted extensive attention in both fundamental studies and practical applications. In this study, a series of upconversion (UC) luminescence phosphors composed of NaGd(PO3)4 (NGP) doped with 20 at% Yb3+ and various concentrations of Er3+ (0.5 at% as the optimal concentration) was synthesized by high-temperature solid-state method. And their crystal structure and the distribution of lanthanide dopants were analyzed using X-ray diffraction with Rietveld refinement verifies. Under 980 nm laser excitation, the obtained phosphors show the characteristic Er3+ upconversion green and red emission bands through two-photon processes. The fluorescence intensity ratio (FIR) based on the thermal coupled states demonstrates the thermal sensing ability in a wide temperature range of 200–573 K. The thermal sensitivity is relatively high with the maximum absolute thermal sensitivity Sa of 0.53 % K−1 (523 K) and the maximum relative thermal sensitivity Sr of 2.60 % K−1. The phosphor NGP:Yb/Er also exhibits high repeatability as the thermal sensors reach 97 %. These findings postulate the potential of NGP:Yb/Er as a promising candidate in optical thermal sensing applications.

Design and characterizations of a new dual-model optical temperature sensing material Ca3La2W2O12: Mn4+/Dy3+

In the recent past, noncontact optical thermometry has flourished as a result of the growing demand for temperature determination. In this work, we presented the first systematic investigation of a novel red phosphor Ca3La2-xW1.984O12: 0.016Mn4+/xDy3+ (CLW: Mn4+/xDy3+). Compared with Dy3+, the emitting intensity of Mn4+ decreases more rapidly with increasing temperature. This property enables CLW: 0.016Mn4+/0.08Dy3+ to be used as a fluorescence intensity ratio thermometer with absolute sensitivity (Sa) of 0.0364 K−1 at 573 K and relative sensitivity (Sr) of 1.551 % K−1 at 473 K. On the other hand, a second temperature sensing model based on the fairly rapid decay of the lifetime is achieved with Sr = 1.953 % K−1 at 523 K and Sa = 0.0034 K−1 at 448 K. The results of this study suggest that phosphor CLW: 0.016Mn4+/0.08Dy3+ could be useful as optical thermometer material with a temperature range of 298K–573K.

Comparative investigation on carbon dots and chloride fluxes modified ZnAl2O4:Cr3+ nanophosphors for temperature sensing, cutting-edge forensic, anti-counterfeiting and w-LEDs applications

A novel Cr3+ doped ZnAl2O4 is synthesized by grafting carbon dots (CDs) and chloride fluxes (NaCl, KCl, NH4Cl) through the solid-state reaction method. Upon excitation at 530 nm wavelength, the Cr3+ ions in the ZAO NPs emit red light due to the influence of a strong crystal field. This red emission arises from the electric dipole 2Eg→4A2g of the Cr3+ ions. Among the chloride fluxes examined, NH4Cl had a significant impact on the PL intensity. Notably, when CDs are incorporated into the ZAO:7Cr3+/NH4Cl NPs, a remarkable increase of 17.25-folds in photoluminescence (PL) intensity is observed. This enhancement is substantially higher than that of CDs alone (11.23-folds) and NH4Cl alone (3.82-folds). The increased PL intensity is attributed to the Förster resonance energy transfer (FRET) mechanism. Furthermore, the addition of CDs (5 wt.%) enhanced the colour purity (CP) of ZAO:7Cr3+/NH4Cl NCs to 99.8%, achieving a high Internal quantum efficiency (IQE) of 93.4 %. Notably, the CDs (5 wt.%)@ZAO:7Cr3+/NH4Cl NCs maintained 92.43 % of their emission intensity even at 420 K, demonstrating exceptional thermal stability compared to ZAO:7Cr3+ NPs. Moreover, the NPs holds promise for optical thermometry, boasting a high relative sensitivity (Sr) of 6.74 × 10-2 %K-1 across a temperature range spanning from 300 to 480 K. Moreover, the latent fingerprints (LFPs) developed using CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs demonstrate remarkable selectivity and high contrast. Under UV irradiation, the structural features of LFPs at levels I–III are clearly visible. In addition, the strong red fluorescence emitted by CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs makes them suitable for applications in AC. CDs(5 wt.%)@ZAO:7Cr3+ NCs exhibit significant potential for w-LED fabrication, achieving a correlated colour temperature (CCT) of 5517 K, a CIE coordinate of (0.332, 0.331), and a high colour rendering index (CRI) of Ra = 94, outperforming ZAO:7Cr3+/NH4Cl NPs. Overall results clearly demonstrates that, CDs(5 wt.%)@ZAO:7Cr3+/NH4Cl NCs are effective for applications in optical thermometry, dactyloscopy, w-LEDs, and AC.

Optimizing the thermal stability of Tb3+-based phosphor through intervalence charge transfer compensation and charge transfer band edge red-shift

Thermal quenching (TQ) limits the large-scale practical application of most luminescent materials, so the investigation on thermal quenching phenomenon of phosphors has emerged as a prominent research area, garnering significant attention in academic circles. The thermal quenching performance is closely related to the charge transfer band (CTB) and intervalence charge transfer (IVCT) band. Herein, we study the correlation between CTB edge red-shift, IVCT band position and the thermal stability of Tb3+-based lithium tantalate phosphors, aiming to regulate the thermal quenching performance. The results show that totally anomalous thermal quenching (TATQ) was found to exist in LiTaO3:xTb3+ phosphors during the process of temperature rising, and the whole CTB edge absorption showed a red-shift and enhance with increasing temperature. Based on this characteristic phenomenon, under the excitation of CTB edge (270 nm), the phosphor exhibits obvious antithermal quenching. In addition, the existence of the Tb3+-Ta5+ IVCT band can be used as a compensation channel for Tb3+ 5D3 → 5D4 transition, which makes the phosphor produce stronger antithermal quenching performance. Accordingly, the co-regulation of the CTB edge red-shift and IVCT compensation effect was proposed. Modulation of Tb3+ concentration revealed that during thermal activation (λem = 547 nm), LiTaO3:0.005Tb3+ luminescence integral intensity (423 K) reaches 255.6% of the initial intensity, phosphor achieves the most excellent performance. The maximum absolute sensitivity (Sa) and relative sensitivity (Sr) for temperature sensing scheme based on the intensity ratio of excitation spectrum CTB and CTB-IVCT reaches 0.996%@523 K and 0.927%@523 K, respectively. The co-regulation strategy of thermal activation-induced CTB edge red-shift and IVCT compensation channel provides a promising research idea for developing Tb3+-based antithermal quenching luminescent materials.

Luminescence properties of Sr2Ga2GeO7:Bi3+ phosphors and temperature sensing characteristics of co-doped Sm3.

As one of the fundamental physical quantities, temperature is extremely important in various fields. In order to study the temperature sensing characteristics of dual-emitting center phosphors, Bi3+-doped and Bi3+/Sm3+-doped Sr2Ga2GeO7 phosphors were synthesized by high-temperature solid-phase method. Under 312 nm excitation, the Sr2Ga2GeO7:Bi3+ phosphor exhibits a blue broadband emission corresponding to the 3P1 → 1S0 transition of Bi3+ ions. By testing the temperature change spectrum of phosphors, it was found that Bi3+ exhibited strong thermal sensitivity. However, due to the fact that single ion doped phosphors are easily affected by other factors when applied to the field of temperature sensing, based on the thermal sensitivity of Bi3+, Sm3+ with low temperature sensitivity was selected as the co-doped ion, and it was found that the two ions had different thermal quenching characteristics when the temperature change spectrum was tested. Using the temperature detection method based on the fluorescence intensity ratio (FIR) of the dual emission centers, it was found that the best absolute sensitivity Sa was 3.125% K-1 and the maximum relative sensitivity Sr was 1.275% K-1 in the range of 303-423 K. These results show that Sr2Ga2GeO7:Bi3+/Sm3+ phosphors have broad application prospects in the field of optical temperature sensing.

Ratiometric optical temperature sensing properties based on up-conversion luminescence of novel NaLaTi2O6:Yb3+,Er3+/Ho3+ phosphors

To satisfy the increasing necessity of contactless optical thermometry, utilizing both thermally coupled (TCLs) or non-thermally-coupled (NTCLs) energy levels of rare earth ions in novel phosphors has significant potential for devising the optical thermometers with high temperature sensitivity. Herein, a sequence of novel Yb3+,Er3+/Ho3+ doped NaLaTi2O6 (NLTO) phosphors were sintered using a high-temperature solid-state reaction approach. Structure, phase component and luminescence performance were identified in detail. Upon 980 nm near-infrared (NIR) excitation, the obtained materials presented typical Er3+/Ho3+ characteristic emission wavelengths in visible region, which include two green emission bands around 522 and 543 nm, as well as a weaker red band around 661 nm for Er3+ doped NLTO, a green emission band around 545 nm and a red band around 657 nm for Ho3+ doped NLTO. Besides, a unusual emission band around 757 nm of Ho3+ in visible edge region was also clearly found. The temperature sensing properties of representative NLTO:Yb3+,Er3+/Ho3+ samples were assessed based on the fluorescence intensity ratio (FIR) technique of TCLs or NTCLs energy levels. The maximal absolute sensitivity (Sa) and relative sensitivity (Sr) were determined to be 0.0374 K-1 (293 K) and 0.970% K-1 (293 K) by taking the FIR of NTCLs 2H11/2→4I15/2 and 4F9/2→4I15/2 transitions in NLTO:Yb3+,Er3+. Simultaneously, the maximal Sa and Sr were 0.0306 K-1 (573 K) and 0.776% K-1 (373 K) using the FIR of NTCLs 5F5→5I8 and 5F4,5S2→5I7 transitions in NLTO:Yb3+,Ho3+. Consequently, the temperature sensitivities above can be compared to reported results, which indicate that as-prepared materials have a promising application in optical temperature sensors field.

Multicolor Mechanoluminescence From Lu3Al2Ga3O12: Tb, Eu for Stress and Temperature Visual Sensing

AbstractMechanoluminescence (ML) refers to the luminescence phenomenon that occurs when a material is under external mechanical stimuli. However, relying solely on stress information to obtain ML signals is prone to test errors in complex test conditions. In this work, a Tb3+/Eu3+‐doped Lu3Al2Ga3O12 multicolor ML material is reported, in which the ML color can be adjusted from white to red (CIE color coordinates: from (x = 0.313, y = 0.3293) to (x = 0.6183, y = 0.379)) by changing the Eu3+ concentration. In addition, LAGO: 0.25% Tb3+ and LAGO: 1.5% Eu3+ are physically mixed at different mass ratios, and the varied stimuli‐responsed emission characteristics of Tb3+ and Eu3+ ions are used to develop a stress and temperature dual sensing device. Stress and temperature information can be further reflected simultaneously through the blue/red emission ratio IR (ITb/IEu). As the temperature increases, the color changes from white to red (CIE color coordinates: from (x = 0.3259, y = 0.306) to (x = 0.4707, y = 0.3625)), and the relative temperature sensitivity (Sr) is as high as 1.209% K−1 at 298 K. This sensing device provides a new idea for potential structural safety monitoring, multi‐modal anti‐counterfeiting technology, etc.

Highly efficient Dy3+ activated Sr9Al6O18 nanophosphors for W-LEDs, optical thermometry and deep learning-based intelligent system for personal identification applications

A novel single-phase Dy3+ activated Sr9Al6O18 nanophosphors (NPs) was synthesized using a solution combustion method with urea as the fuel. When phosphors are excited at 350 nm, their photoluminescence (PL) spectra exhibit strong emissions at 484 and 574 nm, which are associated with the 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions. These emissions are attributed to magnetic and electric dipole allowed transitions, correspondingly. It is found that dipole–dipole interactions are the main source of concentration quenching and energy transfer among the activator ions. The prepared NPs show thermal stability up to 480 K having an activation energy (Ea) of 0.2437 eV, as determined by temperature-dependent photoluminescence (TDPL). With a remarkable internal quantum efficiency (IQE) of 66.14 %, the optimized phosphor achieves notable relative sensitivity (Sr) and absolute sensitivity (Sa), estimated to be 2.65 % K−1 and 1.38×10−3 K−1 at 300 K, respectively. Thus, Sr9Al6O18:Dy3+ is a promising material for non-contact optical thermometry applications. Latent fingerprints (LFPs) and latent lip prints (LLPs) can be efficiently produced on a variety of surfaces by using the optimized NPs with the simple powder dusting technique. The prints are made visible under UV light with a 365 nm wavelength. The You Only Look Once version 8 (YOLOv8x) approach analyzes the overall morphological correlations of different minutiae to identify essential minutiae that indicate the identities of people from FPs. Splitting and matching multi-scale fingerprints (FPs) features improves the validity of the authenticating findings. The results show that the recommended method, which improves the entire FP authentication process, offers exceptional accuracy, resilience and speed. The findings provide strong support for the implementation of the optimized NPs in photonic devices, optical thermometers, and advanced forensic applications.

CsPb(Br/Cl)3-Sm3+ codoped glasses for optical temperature sensing in FIR and chromatic coordinate modes

We have fabricated Sm3+ doped glasses, CsPb(Br/Cl)3 quantum dots (QDs) glasses and CsPb(Br/Cl)3-Sm3+ codoped glasses by melt-quenching and subsequent heat treatment for optical temperature sensing. Photoluminescence (PL), photoluminescence excitation (PLE) spectra and PL decay have been measured. Two CsPb(Br/Cl)3-Sm3+ samples with different PL peaks of QDs at 486 nm and 503 nm have been studied for fluorescence intensity ratio (FIR) and chromatic coordinate sensing. The CsPb(Br/Cl)3 QDs and Sm3+ ions exhibit distinguished spectral components and they are dynamically independent. PL intensity of QDs rapidly decreases with temperature, whereas PL intensity of Sm3+ slowly decreases with temperature. PL intensity of Sm3+ ions and CsPb(Cl/Br)3 QDs have been independently fitted. Then, FIR sensing has been studied. The different variation in PL intensity with temperature for Sm3+ and CsPb(Cl/Br)3 leads to the change of luminescent color and chromatic coordinate. The chromatic coordinate sensing has also been studied. Absolute sensitivity (Sa) and relative sensitivity (Sr) have been analyzed for both FIR and chromatic coordinate sensing. Compared with the chromatic coordinate mode, FIR mode has the larger Sa and Sr. But the chromatic coordinate method is more convenient for application, which does not require separating two spectral components. Both FIR and chromatic coordinate sensing modes show outstanding temperature cycling characteristics.

Up-conversion optical temperature sensing characteristics of new KBaGd(MoO4)3:Yb3+,Ho3+ phosphors

To develop new up-conversion luminescent materials for non-contact optical thermometer with high sensitivity and temperature resolution, a battery of KBaGd(MoO4)3:Yb3+,Ho3+ phosphors were fabricated through solid reaction process. The crystal structure, up-conversion luminescence, energy transfer, thermal stability and optical temperature sensing performances were studied in detail. Under 980 nm laser excitation, the KBaGd(MoO4)3:Yb3+,Ho3+ phosphor exhibits distinctive emission bands of Ho3+ at 545, 660, and 755 nm, and excellent illuminant performance. Based on the thermally coupled levels (TCLs) of Ho3+, both the relative sensitivity (Sr) and absolute sensitivity (Sa) display similar change trends, with the highest values of 6.73%/K (@298 K) and 5.69%/K (@298 K), respectively. Furthermore, the highest Sa of 13.90%/K (@623 K) and the ultimate Sr of 0.62%/K (@ 298 K) are achieved based on non-TCLs of Ho3+. Therefore, KBaGd(MoO4)3:Yb3+,Ho3+ phosphor is a promising candidate for self-referenced optical thermometry.

Modeling of a Single-Band-Ratiometric Sensor Based on Lattice Positive Thermal Expansion in Eu3+-Activated Halide Perovskite Cs2NaEuCl6.

Recently, single-band ratiometric (SBR) thermometry has emerged as an innovative approach to traditional fluorescence thermometry, overcoming uncertainties associated with emission spectrum overlap or scattering while maintaining high spatial resolution and remote monitoring. This paper presents a novel Cs2NaEuCl6 perovskite prepared through a slow-cooling solution method. Additionally, it proposes a temperature sensor model that relies on the thermal quenching of charge-transfer state absorption. Mechanical studies highlight the role of lattice positive thermal expansion in affecting Eu3+ emission. Conversely, a significant emission enhancement is observed upon excitation corresponding to both the ground state and excited state absorption. The distinct luminescent behavior of this Eu3+-activated halide perovskite model makes it suitable for developing a highly sensitive SBR-type sensor with a relative sensitivity (Sr) exceeding 1.5% K-1 and temperature resolution (𝛿T) below 1 K at room temperature. Furthermore, it demonstrates the thermal stability during multiple heating-cooling cycles. Finally, the practical applicability of the proposed SBR model is demonstrated by employing a self-manufactured film sensor that enables precise real-time temperature detection for electronic components. The work is regarded as a significant stride toward the development of cutting-edge and exquisitely sensitive thermometers based on lanthanide-based halide double perovskites.

Regulating Arrhenius Activation Energy and Fluorescence Quantum Yields of AuNCs-MOF to Achieve High Temperature Sensitivity in a Wide Response Window.

Luminescent thermometry affords remote measurement of temperature and shows huge potential in future technology beyond those possible with traditional methods. Strategies of temperature measurement aiming to increase thermal sensitivity in a wide temperature response window would represent a pivotal step forward, but most thermometers cannot do both of them. Herein, we propose a balancing strategy to achieve a trade-off between high Arrhenius activation energy (Ea), which could stretch the temperature response windows, and fluorescence quantum yields (QYs) in a manner that will increase thermal sensitivity in a wide response window. In particular, a luminescent thermometer composed of AuNCs-MOF is prepared via a facile impregnation process to enhance QYs and Ea, responsible for high relative sensitivity (Sr) (15.6% K-1) and ultrawide temperature linearity range (from 83 to 343 K), respectively. Taking fluorescence intensity and lifetime as multiple parameters, the maximum Sr can reach 22.4% K-1 by multiple linear regression. The maximum Sr and temperature response range of the proposed thermometer outperform those of the most recent luminescent thermometers. The strategy of balancing Sr and thermal response range by regulating Ea and QYs enables the construction of ultra-accurate thermal sensors in the age of artificial intelligence.

Upconversion photoluminescence and optical thermometry properties of Gd3BWO9: Yb3+, Ho3+ with high absolute sensitivity

Optical temperature sensing has attracted significant attention owing to its unique characteristics of rapid response, non-contact detection, high resolution and high sensitivity. In this study, a series of Gd3BWO9: Yb3+, Ho3+ upconversion phosphors were synthesized by solid-state synthesis, and the optimal sample was Gd3BWO9: 0.32 Yb3+, 0.003Ho3+. The upconversion emission spectrum was measured under the excitation of 980 nm laser, and the emission peaks in the bands of 528–560 nm and 630–680 nm corresponded to the green emission (5F4/5S2→5I8) and red emission (5F5/→5I8) of Ho3+. The SR and SA of Gd3BWO9:0.32 Yb3+, 0.003Ho3+ in the range of 300 K–625 K were calculated. At 300 K, both the relative sensitivity SR and the absolute sensitivity SA reached their maximum values, which are SR(max) = 0.73 % K−1 and SA(max) = 0.0508 K-1, respectively. The Gd3BWO9: 0.32 Yb3+, 0.003Ho3+ phosphor has a very high absolute sensitivity, and hold great application potential in optical temperature sensing.

Self‐Calibration Temperature Sensing and Color Tunable Emission in a Bimetallic Lanthanide Metal–Organic Framework

ABSTRACTTemperature in various scientific and industrial applications requires accurate detection and measurement. Herein, a range of novel isostructural lanthanide‐based metal–organic frameworks (Ln‐MOFs), [EuxTb2−x(3,5‐pdc)3(phen)2(H2O)2]n (x = 0, Tb‐MOF; x = 2, Eu‐MOF; x = 0.002, 0.010, 0.020, 0.040, 0.080, EuxTb2−x‐MOF), were solvothermally synthesized using 3,5‐pyridinedicarboxylic acid (3,5‐H2pdc) and 1,10‐phenanthroline (phen) as ligands. Based on binuclear second building units, Ln‐MOFs exhibited 2D layered structure with sql topology. The luminescent properties of series Ln‐MOFs show systematic tuning shifted from green to red by adjusting the ratio of Eu3+ to Tb3+. The temperature sensing experiments showed that Eu0.020Tb1.980‐MOF exhibited self‐calibration temperature response in a range of 293–413 K, achieving maximum relative sensitivity (Sr) 2.46%·K−1 at 413 K, outscoring many state‐of‐the‐art temperature sensors reported in literature. This study poses great promise of the newly designed Eu0.020Tb1.980‐MOF for the ultra‐sensitive temperature sensing in diverse and large‐scale applications.

Highly sensitive dual-mode temperature measurement utilizing completely opposite thermal quenching luminescence

In recent years, phosphors have been used in the field of temperature sensing, which has aroused great interest because of its advantages of quick response, high sensitivity and high accuracy. However, exploring optical thermometers with ultra-high sensitivity remains a challenge. In this work, we have designed and synthesized Sm3+ and Mn4+ co-doped La3Mg2NbO9 phosphor for temperature sensing for the first time by utilizing the anomalous thermal quenching property of Sm3+ ions and the sensitive thermal quenching property of Mn4+ ions. Furthermore, the structure, elemental distribution, morphology and optical characteristics of La3Mg2NbO9:Sm3+,Mn4+ were studied in detail. Benefiting from the different responses of the Sm3+ and Mn4+ ions to temperature, the fluorescence intensity ratios of Sm3+ to Mn4+ in La3Mg2NbO9 samples show excellent optical thermometry performance in the range of 303–463 K. The maximum absolute sensitivity (Sa) and relative sensitivity (Sr) values of La3Mg2NbO9:Sm3+,Mn4+ sample reach as high as 0.117 K-1 (@463 K) and 4.48 % K−1 (@303 K), respectively. Furthermore, the maximum of Sa is 0.385 K−1 (@463 K) and the maximum of Sr is 4.54 % K−1 (@303 K) based on the fluorescence lifetime temperature measurement method. The temperature cyclotron curve of the sample proves that the sample has excellent stability and repeatability in temperature measurement. These results demonstrate that the designed La3Mg2NbO9:Sm3+,Mn4+ phosphor is promising for the field of non-contact optical temperature thermometry.

Up-Conversion Luminescence and Optical Temperature Sensing Properties of NaLuF4:Yb3+/Ho3+ Micron-Sized Crystals at Low Temperature.

Non-contact temperature sensors utilising the fluorescence intensity ratio and the unique up-conversion (UC) luminescence of rare-earth ions have numerous benefits; however, their operational temperature range has remained limited. In this study, NaLuF4:Yb3+/Ho3+ samples were prepared by the hydrothermal method. The samples exhibited exceptional UC luminescence properties at low temperatures. The intensity of the green emission (with peak wavelengths of 540 and 546 nm) gradually decreased with increasing temperature, and the green emissions showed a unique change at low temperatures. In addition, we studied the dependence of the UC luminescence intensity on the excitation power and the variation in the decay lifetime with temperature. The experiments revealed excellent luminous performance and significantly enhanced sensitivity at low temperatures; the maximum absolute sensitivity Sa and relative sensitivity Sr of the 540 and 546 nm thermally coupled energy levels were 1.02% and 0.55% K-1, respectively. The potential temperature sensing properties of Yb3+/Ho3+-co-doped NaLuF4 makes it suitable for temperature sensing applications at temperatures as low as 30 K. This study offers a novel approach for the advancement of temperature sensing technology at low temperatures.

Optical properties of La2MgSnO6: Eu3+/Mn4+ double-perovskite phosphors for multifunctional applications

A series of Eu3+/Mn4+ doped La2MgSnO6 double-perovskite phosphors were successfully synthesized by solid-state method. The crystal structure, optical properties, and temperature sensitivity of the phosphors were investigated systematically. Under excitation at 310 and 394 nm, the La2MgSnO6: Eu3+, Mn4+ phosphor exhibits intense red emission of Mn4+ (2Eg→4A2g) and orange-red emission of Eu3+ (5D0→7F2). Within the temperature range of 298–473 K, Eu3+ exhibits excellent thermal stability, whereas the Mn4+ shows significant thermal quenching behavior. A luminescence thermometer for dual-wavelength operation with high sensitivity was designed based on the fluorescence intensity ratio (FIR) method. The value of maximum relative sensitivity (Sr) was calculated as 1.58 % K−1 at 423 K. Particularly, the wavelength-dependent of La2MgSnO6: Eu3+, Mn4+ phosphor was investigated over a range of 270–340 nm, revealing promising potential with a remarkably high maximum wavelength sensitivity of 18.2 % nm−1 at 300 nm. Subsequently, a prototype LED device was fabricated by integrating the La2MgSnO6: Eu3+, Mn4+ phosphors and a near-UV LED chip, demonstrating significant spectral overlap with the absorption curves of plant pigments. These results suggest that the La2MgSnO6: Eu3+, Mn4+ multifunctional phosphor has promising applications in optical thermometry, wavelength detection, and promoting plant growth.