Ratiometric Temperature Sensor Research Articles

Ratiometric temperature sensing with non-thermally coupled levels from Pr–Al co-doped MgGa2O4

Fluorescence intensity ratio (FIR) technique demonstrates significant potential for non-contact temperature sensing with rapid response time, while the design of FIR probes is particularly intriguing. Herein, we report Pr–Al co-doped MgGa2O4 persistent luminescence nanoparticles (PLNPs), as MgAl0.04Ga1.96O4: 0.1 % Pr3+ (MAGP), for ratiometric temperature sensing application. Pr3+ ions function as the emission centers for dual-emission at 612 and 494 nm, while Al3+ ions adjust the lattice environment around Pr3+ ions to enhance the luminescence. Consequently, 274 nm excitation induces the emissions at 494 and 612 nm, as the transitions of Pr3+ for 3P0→3H4 and 1D2→3H4, respectively. The emission mechanism is substantiated by density functional theory calculations, regarding the electronic transitions of Pr3+. Ratiometric temperature sensing is achieved over the temperature range of 303–573 K with the thermally non-coupled mechanism of the 3P0/1D2 energy levels by FIR at 612 and 494 nm, respectively. The maximum relative sensitivity was 0.91 %. The mechanism is corroborated as the non-thermally coupled energy levels through intervalence charge transfer. Thus, the reversible and sensitive response was illustrated for temperature measurement and the non-thermally coupled mechanism is efficient for the design of ratiometric temperature sensors.

Interfacial compatible PolyMOF membranes as ratiometric fluorescence temperature sensors

Cryogenic temperature sensors play significant roles in manufacturing, metallurgy, and aerospace. Metal-organic frameworks (MOFs) as emerging crystal materials exhibited inherent advantages as fluorescence temperature sensors and researchers have shifted their focus toward incorporating MOFs materials into mixed matrix membranes (MMMs) for broader practical applications. However, the poor interfacial compatibility between MOFs particles and the polymer matrix would cause aggregation-induced fluorescence quenching and reduced energy transfer efficiency, thereby compromising temperature sensing performances. Herein, we adopt a post-synthetic copolymerization strategy to realize an interfacial-compatible membranous ratiometric luminescent thermometer based on the emissions of ligands and lanthanide ions. Benefiting from the controllable covalent cross-linking structures, the designed polyMOF membrane exhibited excellent interfacial compatibility and avoided MOFs irregular morphology agglomeration and phase separation, which contributed to outstanding fluorescence temperature sensing performance with excellent sensitivity ranging from 0.300 to 0.745 %·K−1 within the temperature range of 80–300 K, superior to recent reported MOFs-based thermometers. This research presents a promising approach for the design and fabrication of interfacial compatible MOFs-based membranes with excellent fluorescence temperature sensing properties, advancing the understanding of structure-property relationships and accelerating the practical applications.

Stimuli-responsive photoluminescent and structural properties of MIL-53(Al) MOF for sensing applications

Metal–organic frameworks (MOFs) are an intriguing group of porous materials due to their potential influence on the development of indispensable technologies like luminescent sensors and solid-state light devices, luminescent multifunctional nanomaterials. In this research work we explored MIL-53(Al), an exceptional class of MOF that, along with guest adsorption, undergoes structural transitions exhibiting breathing behavior between narrow pore and large pore under temperature and mechanical stress. Therefore, we opted for the time resolved luminescence and FT-Raman spectroscopy to investigate the mechanochromic and thermochromic response of this material under external stimuli. Intriguingly, when subjected to temperature changes, MIL-53(Al) exhibited a ratiometric fluorescence behavior related to the reversible relationship of photoluminescence emission intensity with respect to temperature. Moreover, under higher mechanical stress MIL-53(Al) displayed turn-on behavior in emission intensity, hence offering a thrilling avenue for the application in mechanically deformed-based luminescent sensors and ratiometric fluorescence temperature sensors.

Visible TADF and NIR Quenching Emission of Chromium Activated Zirconium‐Halide Perovskite Toward Ultra‐High‐Sensitive Ratiometric Fluorescent Thermometer

AbstractWith the development of science and technology, the measurement of temperature is receiving more and more attention. However, ratiometric fluorescent thermometers based on thermally coupled energy levels remain challenging because of their low relative sensitivity (Sr). In this work, chromium activated zirconium‐halide perovskite Cs2ZrCl6 microcrystals are successfully synthesized via a simple co‐precipitation method at room temperature. Interestingly, the host Cs2ZrCl6 exhibits reverse thermal quenching due to its thermal‐activated delayed fluorescence (TADF) behavior, while the Cr3+ dopant shows normal thermal quenching. Leveraging the difference in their temperature‐dependent luminescent properties, a ratiometric fluorescent thermometer is ingeniously developed, whose Sr reaches a maximum of 4.23% K−1. Besides, the as‐synthesized thermometer is demonstrated for mobile phone remote temperature measurement. This finding offers a new approach for the design of high‐sensitivity ratiometric fluorescent temperature sensors.

Mn4+/Eu3+ co-doped fluoride toward a blue light-excited optical fiber thermometer.

The ongoing development of ratiometric optical thermometry is mainly trapped in thermally coupled levels of rare-earth ions and inefficient ultraviolet excitation. Herein, a new-type multiple sharp line emitting, blue light-excited K2NaInF6:Mn4+, Eu3+ fluoride phosphor has been reported as a ratiometric thermometer. The f-f transition of Eu3+ paves a steady reference to a highly temperature sensitive Mn4+d-d transition and enables high relative sensitivity of 1.65% K-1 at 573 K. An optical fiber thermometry on a household oven with a relative standard deviation of 0.11% surpasses the standard of precision measurement, showing great potential in practical application. This discovery offers a highly sensitive neotype blue light-excitable ratiometric temperature sensor, that is Mn4+-doped fluoride, promoting practical applications of optical thermometry.

Tunable ratiometric temperature sensors based on a Zn-MOF material incorporating luminescent polyoxometalates and carbon dots

Incorporation of Eu polyoxometalates and carbon dots into a Zn-MOF matrix represents an efficient strategy to build luminescent ratiometric thermometers.

Illuminating the path to high-precision dual-mode optical thermometry: A Mn4+-activated oxyfluoride single crystal for a portable optical fiber thermometric platform

Multifunctional ratiometric and lifetime-technology dual-mode sensing plays a pivotal role in optical thermometry, yet poses substantial challenges in Mn4+-doped oxyfluorides/fluorides. Especially, despite of higher sensitivity, the applicability of lifetime-mode optical thermometers is generally restricted to large volume, highly integrated spectrometers. Here, a Mn4+-doped oxyfluoride single crystal Na2NbOF5:Mn4+ (NNOFM) is demonstrated as accurate dual-mode optical temperature sensor and developed into a portable optical fiber thermometric platform. Homogeneous NNOF shell is grown to improve the moisture resistant for extending operational lifespan. Under blue light excitation, two different temperature-sensitive sharp line vibrational transitions endow ratiometric mode temperature sensor. Importantly, rapidly decaying lifetime of Mn4+ produces high relative sensitivity Sr of 5.36 % K−1 at 448 K among Mn4+-based phosphors. Integrating NNOFM core–shell single crystal into optical fiber and coupling pulsed laser and oscilloscope, a portable optical fiber thermometric platform is realized. Accurate measurement result of boiling water being 373.33 K with quite small relative standard deviation to 0.04 % shows great potential of this fabricated thermometric platform for practical applications. This study not only enlightens the design of high-precision dual-mode optical thermometers in Mn4+-doped oxyfluorides/fluorides, but also illuminates the path to create portable optical fiber thermometric platforms.

Ratiometric optical temperature sensor with wide range and high sensitivity based on the emission of Dy3+ ion-doped Ca5(PO4)2SiO4 phosphor

There is an urgent demand for the development of non-contact optical temperature sensors that possess a wide temperature measurement range and high sensitivity, particularly for extreme environments. In this study, Dy3+-doped Ca5(PO4)2SiO4 phosphors were prepared and comprehensively analyzed. XRD, SEM, EDS, Raman spectrum, as well as excitation and emission spectrum were employed to investigate the structural, photoluminescent, and temperature-dependent properties of the phosphors. Under 349 nm excitation, the luminescence intensity ratio (LIR) of Dy3+ ions at 453 nm (4I15/2) and 480 nm (4F9/2) exhibited a strong correlation with temperature within the range of 296-1073 K. By fitting the FIR of I453 and I480 at different temperatures using Boltzmann equations, we observed a larger energy gap, indicating high relative sensitivity of the synthesized phosphor. Additionally, Ca4.95(PO4)2SiO4: 0.05Dy3+ phosphor shows excellent temperature repetitiveness. These findings highlight the potential applications of Ca5(PO4)2SiO4: Dy3+ phosphors as highly sensitive ratiometric optical temperature sensor over a wide temperature range.

Turning 3D Covalent Organic Frameworks into Luminescent Ratiometric Temperature Sensors.

In this study, we report hybrid crystalline lanthanide-containing 3D covalent organic framework (Ln@3D COF) materials that are suitable for temperature sensing applications. Different routes to obtain these hybrid materials were tested and compared for material quality and thermometric properties. In the first approach, a bipyridine-containing 3D COF (Bipy COF) was grafted with a range of visible emitting lanthanide (Eu3+, Tb3+, Dy3+, and Eu3+/Tb3+) β-diketonate complexes. In the second approach, a novel nanocomposite material was prepared by embedding NaYF4:Er,Yb nanoparticles on the surface of a nonfunctionalized 3D COF (COF-300). To the best of our knowledge, the luminescent materials developed here are the first 3D COFs to be tested as ratiometric temperature sensors. In fact, for the Bipy COF, two different types of thermometers were tested (the Eu3+/Tb3+ system and a rare Dy3+ system), with both showing excellent temperature sensing properties. The reported NaYF4:Er,Yb/COF-300 nanocomposite material combines upconverting nanoparticles with 3D COFs, similar to previously reported metal organic framework (MOF) nanocomposite materials; however, this type of hybrid material has not yet been explored for COFs. As such, our findings open a new pathway toward potential multifunctional materials that can combine thermometry with other modalities, such as catalysis or drug delivery, in just one nanocomposite material.

Ratiometric fluorescence temperature sensing based on thermal coupling energy levels of a single-lanthanide dysprosium MOF

The luminescence intensity ratio generated by thermally coupled energy levels (TCELs) based on lanthanide ions has been demonstrated to be a reliable technique for optical thermometry. In this study, we developed a new single-lanthanide (S’LnMOF), DyBPDA, by a straightforward solvothermal method with the [1,1′-biphenyl]-3,5-dicarboxylic acid (H2BPDA) as a linker and Dy3+ as a single luminescence center. Based on the dual emission originating from TCELs of Dy3+ (4I15/2 and 4F9/2 → 6H15/2), DyBPDA enables as a ratiometric temperature sensor in the range 303–443 K with a maximum relative sensitivity of 0.41%·K−1. This work provides a reference for the facile preparation of S'LnMOF, which further contributes to the optical temperature sensing technology based on TCELs.

A plasmonic fluorescent ratiometric temperature sensor for self-limiting hyperthermic applications utilizing FRET enhancement in the plasmonic field.

Nanoparticle mediated photo-induced hyperthermia holds much promise as a therapeutic solution for the management of diseases like cancer. The conventional methods of temperature measurements do not measure the actual temperature generated in the vicinity of the nanoparticles during illumination. In contrast, nano temperature sensors built on hyperthermic nanoparticles can relay local temperatures around the nanoparticles during thermal induction. In this study, we present a core shell construct consisting of a plasmonic core and a silica shell encapsulating a FRET pair of organic dyes for such application. The plasmonic core imparts photo-induced hyperthermic properties to the nanoconstruct, while the fluorescent shell enables ratiometric sensing of temperature. We see that even at a low dye encapsulation concentration, the shell displays a linear ratiometric fluorescence response to temperature and high energy transfer between the dye pair. Interestingly, Monte Carlo simulations, without considering the plasmonic core, show that the energy transfer in the system should be much smaller than that observed, confirming plasmon enhancement in the FRET energy transfer. We also show the ratiometric temperature measurement using these particles during photoinduced hyperthermia. This study suggests the use of plasmonic nanoparticles in the next generation "self-limiting" photothermal therapy.

Sensing temperature with Tb-Eu-based luminescent thermometer: A novel approach to increase the sensitivity

To obtain ratiometric temperature sensor with high sensitivity we have synthesized three rows of bimetallic Tb-Eu hydroxybenzoates, whose sensitivity was expected to exceed the theoretical limit due to the presence of the temperature-dependent OH-quenching. Single crystals of two new bimetallic complexes were obtained, and their crystal structures were determined. Despite europium complexes with the selected ligands do not emit light, bimetallic Tb-Eu complexes with 3- and 4-hydroxybenzoates demonstrate europium luminescence with the quantum yield up to 77 %. Selected 3- and 4-hydroxybenzoates demonstrated temperature-dependent luminescence in the range of 25–100 °C. For 3-hydroxybenzoate of Tb-Eu, thermometer sensitivity reached 4 %/°C at 100 °C, which exceeds the expected limit of 3.3 %/°C at this temperature and is the highest reported value at this temperature. Temperature resolution is about 3 °C. • Bimetallic Tb-Eu hydroxybenzoate formation increases europium luminescence efficiency from 0 % to up to 77 %. • Tb-Eu 3- and 4-hydroxybenzoates demonstrate temperature-dependent luminescence in the range of 25–100 °C. • The sensitivity reached 4 %/°C at 100 °C, which exceeds the theoretical limit. • Temperature resolution is about 3 °C.

Temperature-dependent photoluminescence of violet phosphorus quantum dots as temperature sensors

Violet phosphorus quantum dots (VPQDs) have been recently produced to give intense green photoluminescence with excellent stability. Quantum dots are promising temperature sensors. However, the temperature-dependent photoluminescence of VPQDs is still unexplored. Herein, both the steady-state and time-resolved photoluminescence of VPQDs have been investigated at 263–353 K. With increasing temperature, the photoluminescence of VPQDs has been demonstrated to have decreasing intensity, blue shifts, and broaden bandwidth with excellent temperature reversibility. The non-radiative heat escape was found to cause the intensity to decrease. The blue shift was deduced to be due to the interplay between the electron–phonon renormalization and the thermal expansion. The enhanced exciton–phonon coupling was found to be the main cause of broaden bandwidth. The photoluminescence lifetime of VPQDs was measured to be stable at different temperatures. The non-radiation recombination processes have been demonstrated to play a crucial role in the photoluminescence by linking static and dynamic processes to calculate the radiative rate and non-radiative rate variation with temperature. The activation energy of VPQDs was deduced to be 90.25 meV, which is suitable for temperature sensing. The linear correlation of photoluminescence intensity and peak position to temperature gives more accurate dual mode sensing for a wide-range of ratiometric temperature sensors.

Ratiometric temperature sensing and molecular logic AND gate execution via Eu3+ doped BaWO4 nanophosphor

Self-calibrated Luminescence thermometry (LT), a contactless temperature measurement technique has gained significant recognition owing to its idiosyncratic contours over conventional thermal sensors. Apart from high relative sensitivity, large operating thermal window, insignificant absolute error with minimum temperature uncertainty are perquisite requirements for feasible endeavor of the developed temperature sensors. In the current work, after efficaciously preparation of Eu3+ doped BaWO4 via hydrothermal route, the inherent thermally coupled energy levels (TCEL) 5D1 and 5D0 of Eu3+ were employed for ratiometric temperature sensor design in 80–500 K range. The intense down-shifting luminescence and high temperature sensitivity elicit small temperature uncertainty (0.05 K) and a low absolute error (−0.12 to 0.14 K). Nevertheless, along with good repeatability (>95%) in thermal cycles, the prepared nanophosphor also demonstrates good stability (after repeated thermal cycles). Additionally, carried out Judd-Ofelt analysis provides significant insight in LT based upon emission behavior of Eu3+. A high value of relative sensitivity (1.65% K−1 and 2.95% K−1 from decay kinetics and ratiometric respectively) with chromaticity shift of 78* 10−3 manifests a visual change in inherent red emission profile from the prepared phosphor. Further, exploiting heat and incident UV as input, the prepared phosphor material is utilized to develop an exclusive dry molecular logic gate (here AND) implementation. As versatile spectroscopic probe, Eu3+ ion was exercised for details structural analysis to disclose the change of local site symmetry in BaWO4 due to aliovalent substitution.

Single Excited Dual Band Luminescent Hybrid Carbon Dots-Terbium Chelate Nanothermometer.

The report introduces hybrid polyelectrolyte-stabilized colloids combining blue and green-emitting building blocks, which are citrate carbon dots (CDs) and [TbL]+ chelate complexes with 1,3-diketonate derivatives of calix[4]arene. The joint incorporation of green and blue-emitting blocks into the polysodium polystyrenesulfonate (PSS) aggregates is carried out through the solvent-exchange synthetic technique. The coordinative binding between Tb3+ centers and CD surface groups in initial DMF solutions both facilitates joint incorporation of [TbL]+ complexes and the CDs into the PSS-based nanobeads and affects fluorescence properties of [TbL]+ complexes and CDs, as well as their ability for temperature sensing. The variation of the synthetic conditions is represented herein as a tool for tuning the fluorescent response of the blue and green-emitting blocks upon heating and cooling. The revealed regularities enable developing either dual-band luminescent colloids for monitoring temperature changes within 25–50 °C through double color emission or transforming the colloids into ratiometric temperature sensors via simple concentration variation of [TbL]+ and CDs in the initial DMF solution. Novel hybrid carbon dots-terbium chelate PSS-based nanoplatform opens an avenue for a new generation of sensitive and customizable single excited dual-band nanothermometers.

Vibrationally Induced Photophysical Response of Sr2NaMg2V3O12:Eu3+ for Dual‐Mode Temperature Sensing and Safety Signs

In the dual‐emitting Eu3+‐activated Sr2NaMg2V3O12 garnet, vibrationally induced thermometric response and thermochromic luminescence are investigated for the first time. Based on the diverse thermal quenching of VO43− and Eu3+ along with the advantage of variation in the fluorescence intensity ratio, a potential phosphor for sensitive dual‐mode ratiometric and colorimetric temperature sensors is proposed in which maximum absolute and relative sensitivity of 0.0135 K−1 and 1.61% K−1 are obtained at 420 K with a temperature resolution <0.2 K. Efficient thermochromic luminescence in which colorific shift from white (300 K) to red (500 K) is observed such that the requirement of larger number of phonons weakens the nonradiative relaxation of Eu3+, resulting in slow quenching, substantiated by estimating radiative and nonradiative decay rates by the 4f–4f intensity method. In contrast, a strong vibrational coupling of excited electrons of the VO43− complex is identified and verified by means of temperature‐dependent Raman and photoluminescence excitation spectra for the first time. Consequently, an increased thermal population of vibrational levels favors rapid thermal quenching of luminescence of VO43− via crossover mechanism. Hence dual‐centered Sr2NaMg2V3O12:Eu is an efficient thermometric and thermochromic luminescent material for optical thermometry and safety sign applications in a high‐temperature environment.

Post-modification preparation of dual-emission Eu3+@ZnII MOFs-based hybrid material and its application in highly sensitive ratiometric sensing for asthma wonder drug-procaterol enhanced by HCO3- and temperature

Currently, procaterol has been widely used as an asthma wonder drug; however, the overuse of procaterol easily leads to arrhythmia, and tachycardia decreased blood pressure. Metal organic frameworks (MOFs) are a new class of hybrid porous materials that have attracted great attention in the past 20 years. These metal-organic framework composites have highly efficient host-guest interactions and are excellent fluorescent sensing materials. In this work, an effective detection method to control the amount of procaterol was designed. A unique three-dimensional (3D) cluster-based metal-organic framework (MOF), namely [Zn2L(DEF)3]n (Zn-MOF, H4L=[1,1′:4′,1′'-terphenyl]- 3,3′',5,5′'-tetracarboxylic acid) can be prepared through the solvothermal method. Furthermore, through postsynthesis strategies, Eu3+ is loaded into cluster-based Zn-MOF to form dual-emission Eu3+@Zn-MOF, which can be employed as a ratiometric photoluminescent sensor for detecting the amount of wonder drug procaterol with a high K sensing constant value (6.12 ☓ 105 [M−1]) and a low limit of detection (LOD) value (46.10 nM). In addition, HCO3- can be effectively detected with a low LOD value (8.28 nM) in procaterol solution while other anions do not respond, which also reveals the pharmacological effects between HCO3- and procaterol. Furthermore, in the HCO3- solution, Eu3+@Zn-MOF exhibits a more sensitive sensing performance for the procaterol with high sensitivity and excellent recovery. On the other hand, Eu3+@Zn-MOF is a highly sensitive ratiometric temperature sensor in the range of 298−353 K. The detection sensitivity of Eu3+@Zn-MOF towards procaterol under the different physicochemical temperatures of the human body (303 K, 308 K, and 313 K) is also compared, This comparision indicates that temperature of 303 K has an enhanced sensing performance for procaterol in comparison with other detection temperatures. In conclusion, with the help of HCO3- and a suitable temperature (303 K), the detection sensitivity of Eu3+@Zn-MOF towards procaterol can be significantly improved and enhanced.

Overview of N-Rich Antennae Investigated in Lanthanide-Based Temperature Sensing.

The market share of noncontact temperature sensors is expending due to fast technological and medical evolutions. In the wide variety of noncontact sensors, lanthanide-based temperature sensors stand out. They benefit from high photostability, relatively long decay times and high quantum yields. To circumvent their low molar light absorption, the incorporation of a light-harvesting antenna is required. This Review provides an overview of the nitrogen-rich antennae in lanthanide-based temperature sensors, emitting in the visible light spectrum, and discusses their temperature sensor ability. The N-rich ligands are incorporated in many different platforms. The investigation of different antennae is required to develop temperature sensors with diverse optical properties and to create a diverse offer for the multiple application fields. Molecular probes, consisting of small molecules, are first discussed. Furthermore, the thermometer properties of ratiometric temperature sensors, based on di- and polynuclear complexes, metal-organic frameworks, periodic mesoporous organosilicas and porous organic polymers, are summarized. The antenna mainly determines the application potential of the ratiometric thermometer. It can be observed that molecular probes are operational in the broad physiological range, metal-organic frameworks are generally very useful in the cryogenic region, periodic mesoporous organosilica show temperature dependency in the physiological range, and porous organic polymers are operative in the cryogenic-to-medium temperature range.

White light-emissive europium complexes and their versatile applications

Dual-emissive single-component white light-emissive Eu-complex-based luminogens were designed and synthesized for white LEDs as well as ratiometric temperature sensors.

Ratiometric fluorescent detection of temperature and MnO4- using a modified covalent organic framework

A new covalent organic framework (COF), PP-TzDa, has been synthesized by post-synthetic modification. Our studies suggest that the modification leads to the changes of both the stacking mode and the fluorescence emission. This new COF shows dual fluorescence emissions, and can be used as a ratiometric fluorescent temperature sensor. In the range of 20–100 °C, the COF suspensions in DMF exhibit the temperature dependent fluorescence and the intensity ratios of two emissions change linearly with temperature. The new COF can also be used as a ratiometric fluorescent sensor for MnO4-. This work represents the opportunity to tune their fluorescent properties and explore their applications of a variety of COFs by simple modification.