Maximum Relative Sensitivity Research Articles

Tunable luminescence and efficient energy transfer investigation of a borosilicate phosphor KBSi2O6: Bi3+, Eu3+ with hypersensitive thermal quenching

Energy transfer between Bi3+ and Eu3+ has undergone substantial research but Bi3+ and Eu3+ co-doped luminescent materials with high energy transfer efficiency for temperature sensing are rarely investigated until now. Herein, Eu3+ and Bi3+ co-doped KBSi2O6 phosphors were successfully synthesized by solid-state reaction method. The phase purity structure as well as the element distribution were carefully investigated through X-ray diffraction structural refinement and energy dispersive spectrometer analysis. The characteristic luminescence property and luminescence kinetics of KBSi2O6: Bi3+, Eu3+ were investigated. By the large spectra overlap between the emission spectrum of Bi3+ and excitation spectrum of Eu3+, the energy transfer from Bi3+ to Eu3+ can be inferred. The corresponding decrease of the emission intensity and decay time of Bi3+ in KBSi2O6: Bi3+, Eu3+ provided direct evidence for the effective energy transfer from Bi3+ to Eu3+. The interaction and energy transfer mechanism between Bi3+ and Eu3+ ions were also studied. By increasing the Eu3+ concentration in KBSi2O6: Bi3+, Eu3+, the color-tunable emission from blue to red can be realized. KBSi2O6: Bi3+, Eu3+ shows hypersensitive thermal quenching behavior and the maximum absolute sensitivity (Sa) and relative sensitivity (Sr) are determined to be 1.87 %K−1 and 2.895 %K−1, respectively. All of the above results imply that KBSi2O6: Bi3+, Eu3+ phosphor can be a color-tunable phosphor for optical temperature sensing.

Energy transfer of Tb3+→Eu3+ in Ca2Al2SiO7 phosphors with multicolor tunable and optical temperature sensing properties

Luminescent temperature sensors based on photoluminescent materials have received considerable attention for their advantages of quick and noninvasive measurement. In this paper, a series of Tb3+, Eu3+ single-doped and co-doped Ca2Al2SiO7 (CAS) phosphors were synthesized by sol-gel method. The phase purity, surface morphology, energy transfer, luminescence characteristics and temperature sensing properties of Tb3+, Eu3+ doped CAS phosphors have been studied carefully. Due to the energy transfer of Tb3+→Eu3+, CAS: Tb3+, Eu3+ phosphors demonstrate tunable luminescence under 238 nm excitation, in which the luminescence color gradually changes from purple-red to cool white, and then to warm white by continuously increasing the concentration of Tb3+ ions. The elongation of the fluorescence lifetime of Eu3+ with increasing Tb3+ ions content further confirms the energy transfer of Tb3+→Eu3+. The thermal behavior of CAS: Tb3+, Eu3+ phosphors shows enhanced luminescence intensity for 404 nm emission while suppressed luminescence intensity for 616 nm emissions with raising temperature, implying its potential in optical temperature sensing. Therefore, the temperature sensing performance is evaluated by using the fluorescence intensity ratio (I404 nm /I616 nm) in CAS: Tb3+, Eu3+ phosphors, showing a maximum relative sensitivity of 1.17%K−1 at 443 K. These results indicate that CAS: Tb3+, Eu3+ phosphors are promising candidates for tunable luminescence and non-contact temperature sensing.

Halide Double Perovskite Nanocrystals Doped with Rare-Earth Ions for Multifunctional Applications.

Most lead-free halide double perovskite materials display low photoluminescence quantum yield (PLQY) due to the indirect bandgap or forbidden transition. Doping is an effective strategy to tailor the optical properties of materials. Herein, efficient blue-emitting Sb3+ -doped Cs2 NaInCl6 nanocrystals (NCs) are selected as host, rare-earth (RE) ions (Sm3+ , Eu3+ , Tb3+ , and Dy3+ ) are incorporated into the host, and excellent PLQY of 80.1% is obtained. Femtosecond transient absorption measurement found that RE ions not only served as the activator ions but also filled the deep vacancy defects. Anti-counterfeiting, optical thermometry, and white-light-emitting diodes (WLEDs) are exhibited using these RE ions-doped halide double perovskite NCs. For the optical thermometry based on Sm3+ -doped Cs2 NaInCl6 :Sb3+ NCs, the maximum relative sensitivity is 0.753% K-1 , which is higher than those of most temperature-sensing materials. Moreover, the WLED fabricated by Sm3+ -doped Cs2 NaInCl6 :Sb3+ NCs@PMMA displays CIE color coordinates of (0.30, 0.28), a luminous efficiency of 37.5lm W-1 , a CCT of 8035 K, and a CRI over 80, which indicate that Sm3+ -doped Cs2 NaInCl6 :Sb3+ NCs are promising single-component white-light-emitting phosphors for next-generation lighting and display technologies.

Blue-light pumped NIR emission of LaOF:Pr3+ nanorods for highly sensitive nanothermometry

Remote thermal sensing is a much-needed technology in today's world; therefore, developing highly sensitive optical thermometer probes has become a necessity. In this study, the luminescence thermometers based on Pr3+ emissions in the red and near-infrared (NIR) regions were used. LaOF:Pr3+ nanorods were synthesized via a microwave-assisted hydrothermal route. The prepared nanorods exhibited excellent photoluminescence (PL) emission in the red and NIR regions under blue laser excitation. Their PL emissions were found to be influenced by temperature, which was exploited to study the thermal sensing ability of the nanorods. Fluorescence intensity ratios (FIRs) of the red and NIR emissions were evaluated for both the thermally coupled levels and the non-thermally coupled levels. The maximum absolute and relative thermal sensitivities were 5% K−1 at 573 K and 0.8% K−1 at 303 K, respectively. The temperature resolution of 0.17 K was achieved for the FIR calculated from the NIR emissions. The nanorods passed the repeatability test, and the FIR maintained a similar pattern for repeated heating and cooling cycles. The results suggest that the prepared nanorods are promising materials for nanothermometry applications.

Luminescence Temperature Sensing and First Principles Calculation of Photoelectric Properties in C12A7 Co-Doped Eu3+ Ions.

Developing high-resolution, high-accuracy fluorescent thermometers is challenging. In this study, the optical properties and thermal sensing of Yb-, Tm-, and Eu-co-doped C12A7 (C12A7:Yb/Eu/Tm), with flower-like structure upconversion microparticles, were studied. Eu3+ doping induced an approximately 6-fold change in the upconversion luminescence (UCL) output in comparison with C12A7:Yb/Tm microparticles. The maximum relative temperature sensitivity (S) of C12A7:Yb/Eu/Tm reached 3.0% K-1, representing an approximately 5-fold difference compared with the value of C12A7:Yb/Tm. In particular, the multicolor upconversion emission of C12A7:Yb/Eu/Tm can easily change from blue to white UCL with increasing temperature. Moreover, the band structure, total density, and optical coefficient of C12A7:Yb/Eu/Tm were investigated via density functional theory. The total density of O atoms increased in comparison with the total density of pure C12A7, indicating that substitution of Ca2+ by Yb/Eu/Tm produced positive vacancies on the cage structure. The optical coefficient of C12A7 was improved by the Yb/Eu/Tm dopant. The thermally regulated multicolor characteristics and thermally coupled energy levels of Tm3+ provide "dual adjustment temperature sensing", which is a promising strategy for realizing accurate and effective temperature sensors.

Anthracene-based lanthanide coordination polymer for the sensitive detection of 2-thiazolidinethione-4-carboxylic acid and temperature

An anthracene-based rare earth coordination polymer (CP) [Tb2Cl2(adip)(NMP)3(H2O)] (1) was prepared by solvothermal assembling of Tb3+ and 5,5′-(anthracene-9,10-diyl)diisophthalic acid (H4adip, NMP = N-methylpyrrolidone) and possesses a 3D framework and ligand-based blue emission. 1 could be used as a fluorescent probe to detect 2-thiazolidinethione-4-carboxylic acid (TTCA) and temperature with excellent selectivity, sensitivity and anti-interference ability. Between 0 and 10 μM concentration range of TTCA, the fluorescence quenching constant (Ksv) of 1 reaches 9.78 × 104 M−1 with the limit of detection of 92.6 nM. 1 could also be used as a temperature sensor within 0–60 °C. The maximum relative sensitivity (Sr) was calculated as 5.74% °C−1 at 60 °C and the temperature resolution (δT) is 0.013–0.003 °C corresponding to the above ambient temperature range. The sensitivities of 1 have reached the best level of reported chemical sensors so far. In addition, the mechanisms of fluorescence quenching were studied.

Tuning the Thermometric Features in 1D Luminescent EuIII and TbIII Coordination Polymers through Different Bridge Phosphine Oxide Ligands.

TbIII and EuIII systems have been investigated as ratiometric luminescent temperature probes in luminescent coordination polymers due to TbIII → EuIII energy transfer (ET). To help understand how ion-ion separation, chain conformation as well as excitation channel impact their thermometric properties, herein, [Eu(tfaa)3(μ-L)Tb(tfaa)3]n one-dimensional (1D) coordination polymers (tfaa- = trifluoroacetylacetonate, and L = [(diphenylphosphoryl)R](diphenyl)phosphine oxide, R = ethyl - dppeo - or butyl - dppbo) were synthesized. The short μ-dppeo bridge ligand leads to a more linear 1D polymeric chain, while the longer μ-dppbo bridge leads to tighter packed chains. As the temperature rises from 80 K, upon direct TbIII excitation at 488 nm, the TbIII emission intensity decreases, while the EuIII emission intensity increases after 160 and 200 K when L = dppeo or dppbo, respectively. The temperature-dependent emission intensities, due to TbIII → EuIII ET, enable the development of ratiometric luminescent temperature probes featuring maximum relative thermal sensitivity up to 3.8% K-1 (250 K, L = dppbo, excitation at 488 nm). On the other hand, the same system displays maximum thermal sensitivity up to 3.5% K-1 (323 K) upon ligand excitation at 300 nm. Thus, by changing the excitation channel and bridge ligand that leads to modification of the polymer conformations, the maximum relative thermal sensitivity can be tuned.

Antithermal Quenching and Multiparametric Temperature Sensing from Mn2+/Tb3+‐Codoped Ca2LaTaO6 Phosphor

Luminescence thermometry plays significant roles in various fields including industrial production, environmental detection, aerospace, and medicine. However, its accuracy improvement remains highly challenging due to the thermal quenching effect of phosphors. Herein, for the first time, a thermal‐activated electron compensation Mn2+‐ and Tb3+‐codoped Ca2LaTaO6 phosphor is developed for multiparametric temperature sensing with tunable emission of Mn2+ and antithermal quenching emission of Tb3+, leading to excellent accuracy at high temperatures. By virtue of the deep electron trap states induced by Mn2+ dopant, the electrons in the deep trap can be thermally activated at high temperatures, which can replenish the attenuated Tb3+ emission caused by thermal quenching, thus bringing out the antithermal quenching phenomenon. On account of the prominent emission properties, the luminescence intensity ratio (LIR) readout and lifetime‐based thermometry are designed, providing a maximum relative sensitivity SR of 3.603% and 1.941% K−1, respectively. Multiparametric temperature sensing and novel data analysis are also employed to further improve the accuracy of the luminescence thermometer. The outstanding relative thermal sensitivity ranging from 8.72% to 16.11% K−1 and temperature uncertainty order of 10−3 are achieved. These results demonstrate that the designed Ca2LaTaO6:Mn2+/Tb3+ phosphor material is a promising thermal‐sensing candidate.

Bi3+-activated dual-wavelength emitting phosphors toward effective optical thermometry

Optical thermometry as an important local temperature-sensing technique, has received increasing attention in scientific and industrial areas. However, it is still a big challenge to develop luminescent materials with self-activated dual-wavelength emissions toward high-sensitivity optical thermometers. Herein, a novel ratiometric thermometric strategy of Bi3+-activated dual-wavelength emission band was realized in the same lattice position with two local electronic states of La3Sb1-xTaxO7:Bi3+(0 ≤ x ≤ 1.0) materials based on the different temperature-dependent emission behaviors, benefiting from the highly-sensitive and regulable emission to the coordination environment of Bi3+. The structural and spectral results demonstrate that the emission tremendously shifted from green to blue with 68 nm and the intensity was enhanced 2.6 times. Especially, the visual dual-wavelength emitting from two emission centers was presented by increasing the Ta5+substitution concentration to 20% or 25%, mainly originating from the two local electronic states around the Bi3+ emission center. Significantly, the dual-wavelength with different thermal-quenching performance provided high-temperature sensitivity and good discrimination signals for optical thermometry in the range between 303 and 493 K. The maximum relative sensitivity reached 2.64%/K (La3Sb0.8Ta0.2O7:0.04Bi3+@383 K) and 1.91%/K (La3Sb0.75Ta0.25O7:0.04Bi3+@388 K). This work reveals a rational design strategy of different local electronic states around the single-doping multiple emission centers towards practical applications, such as luminescence thermometry and white LED lighting.

Dual-mode optical thermometers based on YNbO4:Bi3+,Sm3+ phosphors

Herein, YNbO4:Bi3+,Sm3+ phosphors were fabricated via conventional solid-phase reaction. A thorough evaluation of their structure, morphology, photoluminescence properties and energy transfer from Bi3+ to Sm3+ was carried out, along with the investigation of temperature sensing capabilities. Excited by 312 nm, YNbO4:Bi3+,Sm3+ phosphors exhibit broadband emission from transition of 3P1 to 1S0 of Bi3+ and characteristic emission peaks from 4f-4f transitions of Sm3+. Using color-coordinate and fluorescence intensity ratio (FIR) dual modes, YNbO4:Bi3+,Sm3+ phosphors show good temperature sensitivity. The maximum relative sensitivity (Sr-max) of x and y coordinates reach 0.43%K−1 at 450 K and 0.54%K−1 at 460 K, respectively. The Sr-max of FIR is 1.52%K−1 at 458 K. These results indicate that YNbO4:Bi3+,Sm3+ phosphors offer possibility for designing a dual-mode optical thermometer.

Photoluminescence and temperature dependent properties of Bi3+, Sm3+ co-doped Ca2YSbO6 phosphor for dual-emitting optical thermometer

Bi3+, Sm3+ co-doped Ca2YSbO6 phosphors with dual-emitting centers were created using a high-temperature synthetic process. Investigations were conducted into the phase structure, luminous characteristics, and optical temperature dependent properties. Under the condition of 320 nm Ultraviolet light excitation, the Ca2YSbO6: Bi3+ phosphor exhibits the 3P1→1S0 emission of Bi3+, which peaked at 402 nm, and the Ca2YSbO6: Sm3+ phosphor exhibits the 4G5/2→6Hn/2 (n = 5, 7, 9 and 11) red emission of Sm3+, which is visible between 550 and 720 nm. Spectrum overlap between the PL spectrum of Bi3+ and the PLE spectrum of Sm3+ served as evidence for the energy transfer (ET) behavior. Furthermore, the conclusion could be supported by the life decay of Bi3+.In the case of optimal UV excitation of 320 nm, the maximum absolute sensitivity (Sa) and relative sensitivity (Sr) values for Ca2YSbO6: Bi3+, Sm3+ were 2.21 × 10−3 K−1 and 0.973% K−1, respectively, at 503 K. The outcomes demonstrated that the Ca2YSbO6: Bi3+, Sm3+ phosphor could perform well as an optical thermometer.

New Family of Luminescent Tetranuclear Lanthanide-Based Germsesquioxanes: Luminescence and Temperature Sensing

We report the synthesis, structures, magnetic, and luminescence properties of a new series of tetranuclear lanthanide-based germsesquioxanes [NEt4]2[(Ph4Ge4O8)2(Ln4)(NO3)6(EtOH)2(MeCN)2]·n(CH3CN) (where Ln = Eu3+ (1), Tb3+ (2), Tb3+/Eu3+ (3), Dy3+/Y3+ (4), and Dy3+ (5)). These paramagnetic compounds exhibit characteristic Ln3+-based emission in solid state at room and liquid nitrogen temperature. Temperature-dependent luminescence investigated between 293 and 373 K reveals that mixed Tb3+/Eu3+ (3) compound works as a self-referenced ratiometric optical thermometer with a maximum relative sensitivity of 0.87%·°C–1 achieved at 57.6 °C.

Designing a dual-wavelength excitation Eu3+/Mn4+ co-doped phosphors for high-sensitivity luminescence thermometry

Luminescence thermometry has been widely concerned by researchers due to its quick response, high spatial resolution, and remote measurement. However, low sensitivity is still an existing problem and affects its development. Herein, the luminescence thermometer with high sensitivity taking advantage of the distinguished thermal response between Eu3+ and Mn4+ is designed. Excitedly, Eu3+ exhibits an anti-thermal quenching behavior under 310 nm excitation and a slight thermal quenching behavior under 393 nm excitation due to the energy transfer of host→Eu3+, while Mn4+ presents a strong thermal quenching behavior. Moreover, the energy transfer of Eu3+→Mn4+ (λex = 310 nm and λex = 393 nm) can also be observed for the Ca2Sb2O7: Eu3+, Mn4+ phosphors during the heating process. On the basis of the diverse thermal quenching behavior of Eu3+ and Mn4+, the thermometric performances are investigated by utilizing the fluorescence intensity ratio (FIR) of Eu3+(5D0→7F2)/Mn4+(2Eg→4A2g) under a dual-wavelength excitation. The maximum relative sensitivities of the designed phosphors are determined to be 4.072% K−1 at 305 K under 310 nm and 3.072% K−1 at 351 K under 393 nm excitation. It's worth noting that the thermometric characteristic can be modified by various excitation wavelengths. Hence, the developed Ca2Sb2O7: Eu3+, Mn4+ phosphors have great potential in the field of luminescence thermometry and provide an effective strategy for designing high-sensitivity dual-wavelength excitation optical thermometers.

Developing "smart windows" for optical storage and temperature sensing based on KNN transparent ceramics

Smart windows have attracted considerable attention due to their wide applications in optical data storage, switchable sunroof and temperature sensing. The development strategy for smart windows is focused on performance design, enhancement and integration. However, developing integrated multi-functional smart windows in a single material remains a challenge. In this work, we have successfully prepared (K0.5Na0.5)0.95Ba0.04Er0.01NbO3 (4Ba-1Er-KNN) transparent ceramics for potential applications of temperature detection and optical information storage in smart windows. With alternating ultraviolet (UV) illumination and 300 °C thermal stimulation, the prepared 4Ba-1Er-KNN ceramics can not only achieve non-destructive luminescence readout, but also exhibits an ultra-high photochromic (PC) contrast with rapid response time of 1 s. Furthermore, based on the up-conversion (UC) photoluminescence (PL) intensity ratio of Er3+: 2H11/2/4S3/2 thermally coupled levels, excellent low-temperature sensing performance with the maximum relative sensitivity of 0.023 K−1 at 213 K is obtained. The integration between UC PL, PC response and temperature sensing performance makes it possible to develop multi-functional smart windows.

Multi-ratio optical thermometry and energy storage characteristics of Yb3+/Er3+/Tm3+ doped BaNb2O6 transparent glass-ceramics

• RE-doped BaNb 2 O 6 transparent glass ceramics (GCs) were fabricated firstly. • Realizing three-mode Up-conversion optical thermometry in the GCs. • The maximum S r-max and S a-max can reach 2.30% K –1 and 6.71‰ K –1 . • Achieving high W d of 0.99 J cm –3 and high P d of 225.3 MW cm –3 . • Multifunctional GCs can be used in optical sensing and energy storage fields. In order to meet the needs of new materials gradually developing towards miniaturization, integration, and light weight, multifunctional BaNb 2 O 6 : Yb 3+ /Er 3+ /Tm 3+ transparent glass-ceramics were successfully prepared by melt quenching and controllable crystallization. Its structure, luminescence, and energy transmission were studied. Using the opposite temperature dependence of the Tm 3+ emission band and the corresponding large energy level gap, a maximum relative sensitivity of 2.3% K –1 based on thermal coupling levels (TCLs) is obtained in a wide temperature range (298–673 K). The multi-ratio optical thermometry based on TCLs and non-TCLs is successfully realized by using the different emission bands of double emission centers, which makes it possible for self-reference optical temperature measurement modes. In addition, the transparent glass-ceramic exhibits excellent electrical properties under 700 kV cm –1 electric field: high discharge energy density ( W d = 0.99 J cm –3 ), huge instantaneous power density (225.3 MW cm –3 ), and ultra-fast discharge rate ( T 0.9 ≤ 15.8 ns). The prepared glass-ceramic is expected to be a new type of lead-free multifunctional photoelectric material for temperature sensors and transparent electronic devices.

Tunable emission color and anti-thermal-quenching behaviors in niobates for high-sensitive optical thermometry

Non-contact remote optical thermometers as a significant technique have been extensively developed. However, it is still a challenge to design new Bismuth-doped phosphor materials with tunable spectra for high-sensitive optical temperature sensors. Herein, a novel YxLu1-xNbO4:Bi3+ (0 ≤ x ≤ 1.0) phosphor is constructed by the isomorphic end components LuNbO4 and YNbO4. Owing to the modification of crystal field strength around Bi3+ ions, the emission positions controllably shifted from 475 to 462 nm with the increase of Y3+ ions concentrations. Besides, systematic luminescence modifying from blue to red across the white light region could be achieved via the design of Bi3+→Eu3+ energy transfer (ET). Intriguingly, an anti-thermal-quenching behavior of Eu3+ ion originating from the ET is found in Y0.8Lu0.2NbO4:Bi3+, Eu3+ (YLNO:Bi3+, Eu3+) phosphors, while Bi3+ ion presents a great emission intensity loss with only retaining 46.8% at 383 K. Based on the disparate thermal responses, the fluorescence intensity ratio (FIR) of Eu3+ to Bi3+ demonstrates excellent thermometry properties from 303 to 503 K. The maximum absolute sensitivity (Sa) and relative sensitivity (Sr) reach 0.318 K−1 (@328 K) and 1.62%K−1 (@393 K). In addition, the thermochromic performance of the resultant phosphors could be applied to qualitatively estimate the surrounding temperature. The spectral adjustability and high-sensitive of the developed phosphors highlight their multiplicity of applications in non-contact temperature measurement and white LED.

Raman and photoluminescence intensity ratio: A tool for high temperature optical thermometry in Ba2Y2/3TeO6: Eu3+ double perovskites

Ratiometric thermometry based on lanthanide-activated phosphors is the most reliable method to measure the thermometric figures of merit due to its self-referencing ability. In this work, we use the rarely investigated Raman and photoluminescence intensity ratio (RPIR) method to evaluate the high-temperature sensitivity of a double perovskite phosphor Ba2Y2/3TeO6: 2.5% Eu3+ for the first time. The phosphor exhibits a maximum relative sensitivity of 0.52% K−1 at 573 K with a temperature resolution of 0.17 K. The study proved the RPIR method as a promising strategy for high-temperature optical thermometry using crystalline solids.

Versatile Ca2LnSbO6:Eu3+/Mn4+ (Ln = La, Y, Gd, and Lu) phosphors for temperature sensing and plant growth LED

AbstractA multifunctional double‐perovskite‐type Ca2LnSbO6 (Ln = La, Y, Gd, and Lu) phosphors with Eu3+ and Mn4+ co‐doped were successfully synthesized and designed to simultaneously apply to temperature sensing and plant growth LED. With temperature varying from 303 to 523 K, the integrated intensity of Mn4+ ions (2Eg → 4A2g) markedly decline swifter comparing to Eu3+ ions (5D0 → 7F2) due to the thermal quenching effect. It implies that Mn4+ is susceptive to the temperature in this work. Eu3+ exhibits high heat resistance, which can be selected as a calibration parameter for the fluorescence intensity ratio temperature sensor. The maximum relative sensitivity (Sr) values of Ca2LnSbO6:1%Eu3+, 0.5%Mn4+ (Ln = La, Y, and Gd) phosphor are estimated as 2.19% K−1 at 443 K, 1.68% K−1 at 503 K, and 1.80% K−1 at 483 K, respectively. They are superior to many recent emerging phosphors. Moreover, upon 365 nm excitation, Ca2LnSbO6:1%Eu, 0.5%Mn (Ln = La, Y, Gd, and Lu) phosphors display a wide red emission peaking at 696, 680, 677, and 684 nm, respectively. They come from the overlapped of 2Eg–4A2g of Mn4+ and 5D0–7F4 transition of Eu3+. Their full widths at half maximum are 34, 35, 35, and 29 nm, respectively. They are all perfectly overlapping the absorption curves of chlorophyll a and chlorophyll b, and their fabricated red phosphor‐converted light‐emitting diode device ulteriorly corroborated the promising applications for plant growth. Markedly, the systematic analysis of their crystal chemistry and site preferentially occupancy is first reported and discussed by the bond valence theory.

Excellent Sensitive Temperature Sensing Performance Based on Fluorescence Intensity Ratio Technique of Yb3+/Er3+ Codoped Gd2(WO4)3

The efficient upconversion (UC) particles based on fluorescence intensity ratio (FIR) technique are developed for application in novel temperature sensors. Herein, Yb3+/Er3+‐codoped Gd2(WO4)3 particles are prepared by coprecipitation method and subsequent calcination. The phase structure and surface morphology of the particles are systematically analyzed. The UC emission spectrum of Gd2(WO4)3:Yb3+/Er3+ particles are mainly composed of two strong emission bands centered at 530 and 551 nm, respectively. Moreover, the optimum doping concentration of Yb3+ and Er3+ is fixed at 10% and 2%, respectively. UC emission mechanism based on two‐photon process is investigated by studying the pump power excitation dependence and fluorescence decay behavior of Gd2(WO4)3:10%Yb3+/2%Er3+ particles. The excellent temperature sensing capability of Gd2(WO4)3:10%Yb3+/2%Er3+ particles is implemented from thermally coupled levels (TCLs) of Er3+. Notably, the maximum absolute sensitivity (S a) and relative sensitivity (S r) based on TCLs by 2H11/2/4S3/2 levels are 1.39 %K−1 (at 518 K) and 1.18 %K−1 (at 293 K), respectively. As a result, Gd2(WO4)3:10%Yb3+/2%Er3+ particles have a great potential for application in noncontact temperature sensors.

Multimode fluorescence intensity ratio thermometer based on synergistic luminescence from Eu3+ to Mn4+ of SrTiO3:Eu3+-ZnTiO3:Mn4+ nanocomposites

SrTiO3:Eu3+-ZnTiO3:Mn4+ nanocomposites were successfully synthesized to obtain highly sensitive optical thermometers. The synthesized SrTiO3:Eu3+ was cubic perovskite structure, and the synthesized ZnTiO3:Mn4+ was cubic perovskite structure accompanying with hexagonal ilmenite structure. The results of X-ray diffraction and Fourier transform infrared spectra suggested that the mixture of SrTiO3:Eu3+-ZnTiO3:Mn4+ nanophosphors had no obvious change in the structure after heat treatment at 800 °C. The photoluminescence intensity of Eu3+ in SrTiO3 phosphors revealed a stable temperature dependence, while that of Mn4+ in ZnTiO3 phosphors revealed a sharp temperature dependence. The emission band ranging from 650 nm to 800 nm were separated into two bands centered at 690 nm and 714 nm, which were assigned to 4T2g→4A2g and 2Eg→4A2g transitions of Mn4+ ions in cubic perovskite and hexagonal ilmenite ZnTiO3 matrix, respectively. The maximum relative sensitivity revealed a dependence on the molar ratio between SrTiO3 and ZnTiO3. The maximum value of 3.3 %K−1 was achieved for the composites with the molar ratio of 1:3 between SrTiO3:Eu3+ and ZnTiO3:Mn4+ nanophosphors, which was higher than that of the composites before heat treatment, 3.1 %K−1. The results suggested the potential application in optical temperature probes for the composites.