Relative Sensitivity Sr Research Articles

High-Efficiency Red-Emitting Phosphor of Li0.5La0.5SrMgWO6: Mn4+, Pr3+

The 400–500 nm blue light and 630–750 nm red light play crucial roles in plant cultivation. In this work, a high efficiency red-emitting phosphor, Li0.5La0.5SrMgWO6:Mn4+, Pr3+, was synthesized through the solid-state reaction technique. The absorption and excitation spectra were measured, indicating that 467 nm was an suitable excitation wavelength for this material. Upon excitation with a 467 nm LED, the fluorescence characteristics were evaluated, revealing dual-band red emission peaks located at 621–654 nm and 695–710 nm. The quantum efficiency and pumping slope efficiency were measured to be 63% and 35%, respectively. Based on energy level theory and Tanabe-Sugano theory, the dual-band fluorescence mechanism was analyzed, revealing that cross relaxation phenomenon contributed to the high quantum efficiency. The temperature sensing property was also demonstrated. The relative sensitivity (Sr) exhibited a significant change from 0.05% K−1 to 0.85% K−1 with different temperatures. The phosphor’s high efficiency and exceptional temperature property confer it with extensive potential applications in the fields of plant cultivation and display technology.

A Doped Lanthanide-Based Coordination Polymer Exhibiting High Relative Sensitivity to Ratiometric Luminescent Thermometers at 440 K.

Ratiometric luminescent thermometers with excellent performance often require the luminescent materials to possess high thermal stability and relative sensitivity (Sr). However, such luminescent materials are very rare, especially in physiological (298-323 K) and high-temperature (>373 K) regions. Here we report the synthesis and luminescent property of [Tb0.995Eu0.005(pfbz)2(phen)Cl] (3), which not only exhibits high Sr in physiological temperature but also has a Sr up to 7.47% K-1 at 440 K, the largest Sr at 440 K in known lanthanide-based coordination compound luminescent materials.

Luminescence and optical thermometry strategy based on emission spectra of Li2Ba5W3O15:Pr3+ phosphors

In this study, a series of Pr3+ ions doped Lithium Barium Tungstate (Li2Ba5W3O15) was synthesized using the conventional high-temperature solid state method. The structure and phase of the phosphors were analysed using X-ray diffraction (XRD) patterns. Fourier Transform Infrared (FT-IR) spectroscopy was used to examine the different vibrational bands present. The optical band gap values of the optimized LBW phosphor and the undoped LBW sample were measured using diffuse reflectance spectra (DRS). Under 319 nm excitation, the photoluminescence (PL) spectra of the Pr3+-activated LBW phosphor exhibited strong visible blue and reddish emissions at 488 nm and 647 nm respectively corresponding to the 3P0 → 3H4 and 3F2 transitions of the Pr3+ ions. The evaluated CIE color chromaticity coordinates of the as-prepared LBW:Pr3+ phosphors lie within the white region. The temperature-dependent PL (TDPL) measurement demonstrated relatively good thermal stability for the synthesized phosphor. Moreover, the fluorescence intensity ratio (FIR) was used to analyze the optical sensing properties of the LBW:Pr1.0 phosphor. A maximum relative sensitivity (Sr) of 1.03 % K−1indicated the potential of these phosphors for optical thermometry applications. A double exponential trend with decreasing lifetime was observed in the PL decay data at 647 nm emission (λem) under 319 nm excitation (λex), with an increase in the Pr3+ ions concentration in the host matrix. In conclusion, the investigations conducted demonstrate that the Pr3+ ions doped LBW phosphors show great potential for applications in solid-state lighting and optical thermometry. Its emission characteristics, thermal stability, and optical sensing capabilities establish it as a suitable candidate for these applications.

Ratiometric luminescent thermometry for the third bioimaging window by Er3+ doped garnet with large Stark splitting

Based on the 4I13/2 → 4I15/2 emission (1450–1700 nm) of Er3+ in garnet, which is matching well with third bioimaging window (NIR-III), we propose a ratiometric near-infrared (NIR) thermometer (YAGG:Ce-Er) in NIR-III by utilizing thermal coupling between Stark levels of 4I13/2, where energy levels were split into seven sublevels (I–VII). The energy gaps between Stark sublevel VII and I (ΔEVII-I) and V and I (ΔEV-I) of the 4I13/2 level, calculated from the temperature dependence of intensity ratios of the two selected thermal couples, corresponded well with the theoretical values. This agreement supports the analysis that the system can be utilized as a Boltzmann thermometry. Moreover, the relative sensitivity (Sr) within the temperature range commonly encountered in organisms (25–60 °C) reached a value of 0.63 ± 0.03% K−1 for the VII/I ratio and 0.57 ± 0.07% K−1 for the V/I ratio. These high relative sensitivity values indicate the strong potential for practical application in various biological fields.

Realization of plant growth lighting and temperature detecting based on novel Bi3+, Sm3+ and Mn4+ doped Ca2GdNbO6 double perovskite phosphors

The Bi3+ or Sm3+ ions are introduced into Mn4+-activated Ca2GdNbO6 (CGN) double perovskite phosphors to achieve highly efficient plant growth lighting and temperature measurement. Here, the energy band and density of states for CGN are computed using density functional theory (DFT) in detail. The emission bands of CGN: Bi3+/Mn4+ consist of both the blue-light band (3P1→1S0 transition of Bi3+ ions) and red-light band (2E→4A2 transition of Mn4+ ions), which solves the issue of the lack of blue light in Mn4+-activated phosphors used in plant-growth LEDs. The electroluminescence emission spectrum of the LEDs assembled with CGN: Sm3+/Mn4+ shows a wide emission band (550–800 nm), which coincides perfectly with the absorption (550–825 nm) of Phytochrome (PR and PFR). Moreover, non-contact thermometers are designed by luminescence intensity ratio technique (LIRMn/Bi or LIRMn/Sm) with excellent absolute (Sa = 0.074 K-1@448 K or 0.036 K-1@373 K) and relative sensitivity (Sr = 2.13 %K−1@498 K or 1.11 %K−1@448 K). The results reveal that as-prepared phosphors have great potential in promoting indoor plant cultivate and optical temperature sensing.

Luminescent thermometry with YVO4:Er/Nd: Achieving high sensitivities within the 1st and 2nd biological windows

YVO4:Er3+, Nd3+ powders were prepared by the modified sol gel synthesis route using glucose as chelating agent and characterized by X-ray powder diffraction (XRD) and scanning electron microscope (SEM). Under 660 nm excitation, four infrared emission bands located between 790 and 845 nm, 870 and 930 nm, 950 and 1030 nm, and between 1050 and 1100 nm were observed, and were assigned the transitions 4F5/2 – 4I9/2 (Nd) and 4I9/2 – 4I15/2 (Er), 4F3/2 – 4I9/2 (Nd), 4I11/2 – 4I15/2 (Er), and 4F3/2 – 4I11/2 (Nd), respectively. The performance of these powders as optical temperature sensors using the luminescence intensity ratio (LIR) technique between thermally coupled levels (TCLs) and non-thermally coupled levels (non-TCLs) was studied within the temperature range of 293–373 K. Using different combinations of the emission intensities at 809, 880, 914 and 1003 nm, three distinct (LIR) temperature sensors schemes were built, with both excitation and emission within the first and second biological window. These LIRs relative sensitivity (Sr) and temperature uncertainties (δT) were investigated for samples with different Er and Nd concentrations. Sr values up to 2.08 ± 0.03%. K−1 and δT smaller than 1 K, were obtained. Repeatability and reproducibility tests demonstrated the reliability of the proposed LIRs.

Energy transfer in Bi3+-Sm3+ co-doped phosphors for temperature sensing and imaging

Optical thermometry has the distinct superiority of non-invasive, non-contact, and high spatial resolution. However, the simultaneous improvement of temperature sensitivity and resolution remains challenging. Herein, the tunable emission colors can be realized via energy transfer in Bi3+-Sm3+ co-doped La3Ta0.8Sb0.2O7, which further applied for fluorescence temperature sensing and imaging. With the partial substitution of Sb5+ with Ta5+, the emission peak of La3SbO7:0.04Bi3+ shiftes from 530 nm to 460 nm, together with a 2.1-fold enhancement of emission intensity. The emission shifted from bright blue to purple under 365 nm excitation based on the energy transfer. The energy transfer efficiency from Bi3+ to Sm3+ can reach 41.6 % via dipole–dipole interaction. The La3Ta0.8Sb0.2O7:(0.04Bi3+,0.005Sm3+) phosphors exhibit maximum relative sensitivity (Sr) of 1.32 %K−1 (@498 K) and absolute sensitivity (Sa) of 0.059 K−1 (@417 K), which have excellent temperature resolution and repeatability. Thus, the energy transfer in co-coped phosphors can simultaneously improve the temperature sensitivity and resolution for fluorescence temperature sensing. Besides, the phosphor/PDMS films can exhibit obvious thermochromic imaging.

Thermally boosted upconversion luminescence and high-performance thermometry in ScF3:Yb3+/Tm3+ nanorods with negative thermal expansion

Luminescence nanothermometers featuring high spatial resolution and thermal resolution have aroused extensive interest in biological and nanomedical fields. However, the challenge of thermal quenching in upconversion (UC) nanocrystals hampers achieving elevated relative temperature sensitivity (Sr). In this study, the quasi cubic nanorods of ScF3:Yb3+/Tm3+ with negative thermal expansion were prepared, and thermally boosted luminescence was found to derive from the phonon-assisted energy transfer, resulting in the emission band of 3F2,3 → 3H6 of Tm3+ ions enhanced monotonously. While the emission bands of (1G4)1D2→3F4 of Tm3+ ions first increased slightly and then decreased seriously because of the competition between phonon-assisted and cross-relaxation (CR) processes. Relying on this high-contrast thermal dependent feature, the maximum relative sensitivity of 1.60% K−1 at 523 K was achieved in the proposed luminescence intensity ratio (LIR) thermometry. These findings would open a new avenue for designing thermally boosted upconversion nanocrystals and reliable optical thermometers by using Tm3+ activated luminescent materials.

Multifunctional near-infrared Zn2TiO4:Cr3+ phosphors for luminescence, thermometry, and plant cultivation

A novel near-infrared phosphors Zn2TiO4:Cr3+ were synthesized through solid-state reaction, and the phosphors exhibit near-infrared emission at 600–850 nm under the excitation of 467 nm. An emission peak appears at 716 nm, which is attributed to 2E→4A2 spin-forbidden transition of Cr3+. Phase purity, photoluminescence properties and crystal filed environment of Zn2TiO4:Cr3+ were systematically investigated. Both the concentration and thermal quenching mechanisms were analyzed in detail. Moreover, the emission band of the phosphor match with characteristic absorption of PFR. At 398 K, the relative sensitivity Sr and absolute sensitivity Sa were estimated. The findings of this study demonstrated that the phosphors Zn2TiO4:Cr3+ are promising for both optical thermometry and plant cultivation.

Tm3+-doped Cs2Ag0.6Na0.4In0.9Bi0.1Cl6 microcrystals for thermometry

Lead-free double perovskites have superb luminescence properties for broad applications. However, increasing or improving near-infrared (NIR) photoluminescence (PL) is still a challenge. In this paper, a high-performance microcrystal is designed based on Tm3+ heavily doped Cs2Ag0.6Na0.4In0.9Bi0.1Cl6 (CANIBC), which realize both the self-trapped excitons (STEs) and Tm3+ NIR emission. The emission mechanism and energy transfer (ET) process are studied by steady-state and time-resolved PL spectra. The ET efficiency from STEs to Tm3+ can reach 38.3 %, and the NIR PL quantum yield of Tm3+ can reach 22.7 %. Meanwhile, the PL spectra of Tm3+-doped CANIBC microcrystals (MCs) with different concentrations are used to investigate their temperature sensing properties based on both fluorescence intensity ratio (FIR) and lifetime. Based on the FIR, relative sensitivity (Sr) can reach 2.93 % K−1 at 303 K. Moreover, based on lifetimes, Sr can maintain more than 1.55 % K−1 from 303 to 453 K, and maximum Sr can also achieve 2.38 % K−1 at 360 K. These excellent luminescence and sensing properties offer greater development potential in the field of NIR phosphor and thermometry.

Structural and luminescent performance and optical thermometry of Pr3+ doped SrWO4 down-conversion phosphors

A series of Pr3+ doped SrWO4 phosphors were synthesized using solid-state reaction routes. The phase composition, photoluminescence and temperature sensitivities of as-prepared materials were investigated. Rietveld refinement of measured XRD data was applied to analyze the lattice parameters. The optical transition was elaborated using UV–visible diffuse reflectance spectra and photoluminescence spectra. The photoluminescence measurements confirmed the strong visible light emission from the developed phosphors under both UV excitation at 250 nm and blue excitation at 450 nm. Notably, the maximum emission intensity was observed at a Pr3+ doping concentration of 2 mol%. Furthermore, the fluorescence intensity ratio (FIR) technique was employed, focusing on the emissions originating from the 3P0 and 1D2 state of Pr3+ within the temperature range of 298–598 K. Two FIR groups were adopted in this case, which can verify each other to achieve self-calibration. Typically, SrWO4:0.02Pr3+ exhibited remarkable performance as a temperature sensor, displaying an absolute sensitivity (Sa) of 3.11%K−1 and a relative sensitivity (Sr) of 0.81%K−1. As a result, the significant temperature-dependent PL and remarkable down-conversion luminescence make the SrWO4:Pr3+ material a promising candidate for optical thermometers and UV to visible converters of solar cell applications.

Novel Fluoride Matrix for Dual-Range Optical Sensors and Visualization

Novel tetragonal matrix Ba0.5−xLn0.5NaxF2.5−x with x = 0.08, doped by Yb3+, Ho3+, Er3+, was synthesized by molten salt synthesis (MSS) from nitrate flux. XRD data show that the tetragonal phase with a = 4.122(1) Å, c = 17.672(1) Å is stable in an argon atmosphere up to 960 °C. Luminescence spectra recorded in 500–900 nm and 1050–1700 nm upon 974 nm pumping demonstrated the characteristic luminescence at 1550 nm (4I13/2 → 4I15/2) for Er3+ and 1150 nm (5I6 → 5I8) for Ho3+. The relative thermal sensitivity (Sr) at 296–316 K were 0.3%×K−1 and 5.5%×K−1 in shortwave infrared (SWIR) and visible range, respectively. Synthesized luminophores can be used as dual-range optical temperature sensors, which simultaneously operate in visible and SWIR ranges.

A multi-mode self-referenced optical thermometer based on low-doped YVO4: Eu3+ phosphor

In recent years, the continued development of optical thermometry has become a hot topic of interest for researchers, due to its advantages of non-contact and non-invasive temperature measurement. The optical thermometry is based on the different photophysical properties or changes in luminescent parameters of luminescent materials to reflect temperature. Further, the development of multi-mode optical thermometers can effectively expand the practical application rang of the temperature measurements. Here, we monitored various temperature sensitive luminescence characteristics of YVO4: Eu3+ phosphor by testing its temperature-dependent photoluminescence (PL) spectra, photoluminescence excitation (PLE) spectra, and luminescence decay curves. We successfully realized a multi-mode optical thermometer based on the luminescence intensity ratio, absorption intensity ratio, the thermally induced behavior of the charge transfer band, and luminescent transition probability (A) of the host material. Different temperature measurement strategies were evaluated and compared in terms of relative sensitivity (Sr) and temperature uncertainty (ΔT). Notably, the Sr of the rarely used temperature measurement strategy based on the A of host luminescence was the optimal among the studied strategies with 2.03% K−1, corresponding to a ΔT of 0.5 K. The results suggest that YVO4: Eu3+ phosphor has potential applications in self-referential optical thermometry.

Tb3+/Mn4+ co-doped SrLaMgNbO6 green/red dual-emitting phosphors for optical thermometry

Remote and noncontact surface temperature measurements are frequently required yet challenging to execute. One the most promising options consists in using rare earth or transition metal doped materials as optical (luminescence) temperature sensors. In this paper, a series of novel Tb3+/Mn4+ co-doped SrLaMgNbO6 (SLMN) phosphors have been synthesized and thoroughly investigated for their structural, luminescence spectroscopic and decay kinetics properties as well as for temperature sensing performance. X-ray powder diffraction (XRD) analysis has shown that the prepared sample presents a double perovskite structure. Upon the UV excitation, emission spectra of SLMN:Tb3+, Mn4+ exhibit green and red emission bands for Tb3+ and Mn4+ dopants, respectively. Temperature-dependent photoluminescence (TD-PL) studies revealed sever thermal quenching of Mn4+ emission while that of Tb3+ was moderate providing well pronounced difference in fluorescence intensity ratios (FIR) of the ions. The maximum relative sensitivity (Sr) was found to be 3.27% K−1 and 1.92% K−1 for Mn4+ and Tb3+, respectively. This implies that SLMN: Tb3+, Mn4+ phosphor is a viable candidate material for a dual-mode optical temperature detection.

Upconversion NIR luminescence negative thermal quenching and temperature sensing in LiYGeO4:Yb3+/Nd3+ phosphors

Solid state reaction was used to create LiYGeO4(LYG):Yb3+/Nd3+ phosphors, and upconversion luminescence (UCL) properties were investigated under 980 nm laser stimulation. When only the Yb3+ concentration is altered, and the doping concentration of Nd3+ is kept at 0.02, LYG:0.30 Yb3+/0.02Nd3+ achieves the highest UCL intensity. Because to phonon-assisted transitions and electron thermal migration, considerable near infrared (NIR) UCL negative thermal quenching (NTQ) from Nd3+ is observed with rising sample temperature. The UCL intensity of 4F7/2/4S3/2 → 4I9/2 transition in LYG:0.20 Yb3+/0.02Nd3+ at 723 K is 301.39 times than that at 303 K, and the total UCL intensity of 4F7/2/4S3/2; 4F5/2/2H9/2; 4F3/2 → 4I9/2 transitions attain 24.32 times. Moreover, the temperature sensitive characteristic based on the technology using luminescence intensity ratio (LIR) was systematically evaluated. According to the study, LYG:Yb3+/Nd3+ phosphors exhibit a remarkable NIR UCL NTQ effect and a relative temperature sensitivity (Sr) reaches 1.41% K−1, making them appropriate for application as a photothermal thermometer under high temperature.

Exploring the luminescent thermometer and optical storage applications in negative thermal quenching phosphor of BaSc2Ge3O10:Pr3+

The optical contactless thermometer demonstrates remarkable advantages over traditional contact thermometers. However, maintaining a strong optical signal output across a wide temperature range poses a challenge due to the thermal quenching effect. In this study, we aimed to overcome the limitation of low signal intensity in high-temperature applications by developing a Pr3+-doped BaSc2Ge3O10 (BSGO) phosphor with anti-thermal quenching properties. This phosphor was designed to ensure a stable and sufficiently strong light signal for accurate temperature measurements. The phosphor exhibited a negative thermal quenching effect, where the integrated emission intensity spanning from 450 nm to 800 nm increased from 173 K to 253 K, and the intensity at 353 K still remained stronger than at 173 K. Multiple 4f-4f transition emissions were observed in the phosphor, and the fluorescence intensity ratio (FIR) was utilized as a standard parameter for temperature evaluation ranging from 82 K to 353 K. At 82 K, the phosphor achieved maximum relative sensitivity (Sr) of 2.3% K−1. The presence of multiple traps with depths ranging from 1.09 eV to 1.50 eV not only supported luminescence with a negative thermal quenching effect but also resulted in long persistent luminescence (LPL), which was systematically investigated in this study.

Morphology controlled synthesis and sensitive temperature sensing performance of Gd2(WO4)3: Er3+, Yb3+

Rare-earth ion doped negative thermal expansion materials as fluorescent thermosensitive materials have attracted significant attention due to their natural advantage in achieving high resolution fluorescence. Herein, Er3+/Yb3+-codoped Gd2(WO4)3 microparticles were developed. Their morphology and size can be finely controlled by manipulating the additives, pH values, and reaction rates. Under near-infrared (NIR) excitation, the compounds evince green and red UC emissions. With regards to the thermal coupling level of 2H11/2/4S3/2 of Er3+ ions, the maximum absolute sensitivity (Sa) and relative sensitivity (Sr) were established to be 1.39 % K−1 (at 300 K) and 1.18 % K−1 (at 293 K), respectively. Ultimately, the utilization of synthesized microparticles and a 940 nm NIR chip facilitated the development of a proficient green-emitting light-emitting diode device. The aforementioned characteristics indicate that Er3+/Yb3+ co-doped Gd2(WO4)3 microparticles possess potential applications in the fields of non-contact optical temperature sensing as well as solid-state lighting.

Structure, Luminescence and Temperature Detection Capability of [C(NH2)3]M(HCOO)3 (M = Mg2+, Mn2+, Zn2+) Hybrid Organic-Inorganic Formate Perovskites Containing Cr3+ Ions.

Metal-organic frameworks are of great interest to scientists from various fields. This group also includes organic-inorganic hybrids with a perovskite structure. Recently their structural, phonon, and luminescent properties have been paid much attention. However, a new way of characterization of these materials has become luminescence thermometry. Herein, we report the structure, luminescence, and temperature detection ability of formate organic-inorganic perovskite [C(NH2)3]M(HCOO)3 (Mg2+, Mn2+, Zn2+) doped with Cr3+ ions. Crystal field strength (Dq/B) and Racah parameters were determined based on diffuse reflectance spectra. It was shown that Cr3+ ions are positioned in the intermediate crystal field or close to it with a Dq/B range of 2.29-2.41. The co-existence of the spin-forbidden and spin-allowed transitions of Cr3+ ions enable the proposal of an approach for remote readout of the temperature. The relative sensitivity (Sr) can be easily modified by sample composition and Cr3+ ions concentration. The luminescent thermometer based on the 2E/4T2g transitions has the relative sensitivity Sr of 2.08%K-1 at 90 K for [C(NH2)3]Mg(HCOO)3: 1% Cr3+ and decrease to 1.20%K-1 at 100 K and 1.08%K-1 at 90 K for Mn2+ and Zn2+ analogs, respectively.

Improved optical thermometric sensitivity of Eu3+‐doped calcium niobate phosphor via nonstoichiometric control

AbstractEu3+‐doped calcium niobate CaNbxO6 phosphors were successfully prepared by a solid‐state reaction, and the crystal structure, morphology, energy transfer process, and temperature‐dependent behaviors were systematically investigated. The CaNbxO6 host matrix presents the self‐activated characteristic emission at 470 nm due to the charge transfer transition of Nb5+–O2+, and the corresponding photoluminescence intensity reaches the maximum intensity when the nonstoichiometric ratio of Ca2+/Nb5+ ions is 1:1.9. Moreover, the energy transfer process from the host (470 nm) to Eu3+ (612 nm) ions in the CaNb1.9O6:Eu3+ phosphor is demonstrated, and the corresponding energy transfer efficiency is significantly enhanced compared with that of stoichiometric sample. Furthermore, it is observed that nonstoichiometric ratio of Nb5+ ions deteriorates the thermal quenching of the matrix while guaranteeing the thermal stability of the activators, resulting in the relative sensitivity (Sr) of CaNb1.9O6:Eu3+ being greatly improved from 2.235% to 3.673% K−1. Herein, these results provide an effective strategy for manipulating the sensitivity of optical thermometers of phosphors based on the induced modulation of the temperature‐response performance via nonstoichiometric control.

Luminescence and temperature‐sensing properties of Y4GeO8:Bi3+,Eu3+ phosphor

AbstractIn this paper, Y4GeO8:Bi3+,Eu3+ phosphor with dual emission centers was elaborated via conventional solid‐state reaction technology. Thorough research on the structure, morphology, and luminous properties of Y4GeO8:Bi3+,Eu3+ phosphor, the potential applications in optical thermometry were investigated by means of fluorescence intensity ratio and thermochromic techniques. Under 290 and 347 nm excitation, Y4GeO8:Bi3+,Eu3+ phosphor presents broadband emission from 3P1 → 1S0 transition of Bi3+ ions and characteristic emission peaks from 4f–4f transition of Eu3+ ions. Outstanding temperature‐sensing capabilities are acquired from Y4GeO8:Bi3+,Eu3+ phosphor. The maximum relative sensitivity (Sr) can attain 1.51% K−1 (λex = 290 nm). With temperature raising (303–513 K), the emitted color of Y4GeO8:Bi3+,Eu3+ phosphor (λex = 290 nm) shifts from faint yellow to red with a high chromaticity shift (0.180), which can be distinguished by the unaided eye clearly. Our results indicate that Y4GeO8:Bi3+,Eu3+ phosphor has potential applications in optical temperature measurement and high‐temperature safety marker.