Fluorescence Temperature Sensor Research Articles

Stable and sprayed cesium-lead-halide perovskite triggered visual temperature sensor for cold chain transport

Temperature sensing is significant in cold chain logistics, but developing a cost-effective temperature indicator that can be produced on a large scale remains a considerable challenge. In this study, a highly efficient, cost-effective, and amenable to large-scale production perovskite fluorescent temperature sensor was developed based on the strong linear photoluminescence dependence of cesium lead bromide perovskite nanocrystals (CsPbBr3 NCs), utilizing the dual confinement of liquid nitrogen and N,N-dimethylformamide (DMF). Due to the introduction of liquid nitrogen, CsPbBr3 NCs were able to stabilize, and the precursor solution can remain unchanged for over 30 days under low-temperature conditions. This fluorescent temperature sensor would gradually change its blue light from 440 nm to a bright green (524 nm) as the temperature rises to room temperature (25 °C). More importantly, due to nano nano-fibered CsPbBr3 NCs temperature sensor prepared via electrospinning process can directly contact with the atmosphere, it would facilitate rapid recrystallization and results in a swift color change from blue to green within 24 h. These characteristics demonstrate significant potential for applications in temperature sensing, especially for cold chain logistics to monitor the transportation of agricultural products, processed foods, and special items.

Defect-Enabled Superior Negative Thermal Quenching in Palmierite Ba9La(VO4)7:Eu3+ for WLED In Situ Temperature Measuring.

Negative thermal quenching (NTQ) of the phosphors is critically important for both scientific research and practical applications, but the design of efficient NTQ phosphors is still a challenging task. Herein, we report a new strategy for developing NTQ materials by cation-vacancy engineering. Specifically, a new color-tunable Ba9La1-x(VO4):xEu3+ (BLVO:xEu3+) phosphor with abundant intrinsic cation vacancy was developed, exhibiting superior NTQ behavior under 365 nm excitation. The NTQ performance can be modulated via adjusting Eu3+ doping levels, and the emission intensity of Eu3+ ions in the BLVO:0.20Eu3+ phosphor increased by 275% at 473 K compared to room temperature. Furthermore, the reported material emitting bright white light under 365 nm excitation was well-suited for use in white light-emitting diode (WLED) phosphor and fluorescent temperature sensors, exhibiting outstanding color-rendering index (90.1) in lighting and high sensitivity (Sa = 11.83% K-1, Sr = 2.33% K-1) in temperature detecting. Lastly, the operating temperature of WLED at different currents can be monitored and displayed in real time through emission spectroscopy. All of the results demonstrated that the designed NTQ BLVO:xEu3+ can be used as a single-phase white phosphor and optical thermometry. This work provides a fresh perspective for designing high-efficient NTQ phosphors and expands the application of phosphors in WLED in situ temperature detection.

A Programmable Ambient Light Sensor with Dark Current Compensation and Wide Dynamic Range.

Ambient light sensors are becoming increasingly popular due to their effectiveness in extending the battery life of portable electronic devices. However, conventional ambient light sensors are large in area and small in dynamic range, and they do not take into account the effects caused due to a dark current. To address the above problems, a programmable ambient light sensor with dark current compensation and a wide dynamic range is proposed in this paper. The proposed ambient light sensor exhibits a low current power consumption of only 7.7 µA in dark environments, and it operates across a wide voltage range (2-5 V) and temperature range (-40-80 °C). It senses ambient light and provides an output current proportional to the ambient light intensity, with built-in dark current compensation to effectively suppress the effects of a dark current. It provides a wide dynamic range over the entire operating temperature range with three selectable output-current gain modes. The proposed ambient light sensor was designed and fabricated using a 0.18 µm standard CMOS process, and the effective area of the chip is 663 µm × 652 µm. The effectiveness of the circuit was verified through testing, making it highly suitable for portable electronic products and fluorescent fiber-optic temperature sensors.

Glass Ceramic Fibers Containing PbS Quantum Dots for Fluorescent Temperature Sensing

Glass ceramics (GCs) containing PbS quantum dots (QDs) are prepared for temperature sensing. Broadband emissions are detected in the GCs when PbS QDs are precipitated from the glasses, and emissions centers are modulated from 1250 nm to 1960 nm via heat treatments. The emission centers of GCs exhibit blue-shifts when environment temperatures increase from room temperature to 210 °C. Importantly, the shift values of emission centers increase linearly with the test temperature, which is beneficial for applications in temperature sensing. A temperature sensor based on PbS QDs GC is heat-treated at 500 °C for 10 h, possesses the highest sensitivity of 0.378 nm/°C, and exhibits excellent stability and repeatability at high temperatures (up to 210 °C). Moreover, GC fibers are fabricated by using the GCs as the fiber core. The sensitivity of the temperature-sensing sensor of the GC fibers is also demonstrated and the sensitivity is as high as 0.558 nm/°C. The designed PbS QDs GCs provide a significant materials base for the manufacturing of fluorescent temperature sensors and the GC fibers offer significant opportunities for temperature detection in complex, integrated and compact devices.

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.

Temperature sensing performance of M2La8(SiO4)6O2:Ce3+(M=Ca, Sr, Ba) based on fluorescence intensity ratio of dual emission centers in different coordination environments

Rare earth doped luminescent sensing materials as non-contact thermometers have attracted extensive research interests due to their wide applications in areas like military, medical care, aerospace, etc. How to expand the working temperature range and improve the sensitivity has become the focus. In this work, we synthesized a series of apatite-structured luminescent temperature sensors M2La7.9Ce0.1(SiO4)6O2 (M = Ca, Sr, Ba) via isomorphic substitution. By monitoring the differential changes of emission intensities from Ce3+ at the 7-coordinate and 9-coordinate site respectively when temperature varies, the real-time temperature can be determined. These materials were proven to possess the maximum absolute sensitivity up to 0.825 × 10−3 K−1, 2.63 × 10−3 K−1 and 4.33 × 10−3 K−1, respectively. Meanwhile interesting regular patterns were observed for their temperature sensitivities with the substitution of Ca, Sr and Ba. Furthermore, through studying the temperature sensitivity of Ba2La8(SiO4)6O2:xCe3+ samples with different concentrations, it was found that when the Ce3+ content was at the optimal doping concentration of 0.7, the absolute sensitivity of the sample reached 14.64 × 10−3 K−1 at 573 K. This finding has opened up a new avenue for designing fluorescent temperature sensors.

Rhodamine B-Containing Chitosan-Based Films: Preparation, Luminescent, Antibacterial, and Antioxidant Properties.

In this study, Rhodamine B-containing chitosan-based films were prepared and characterized using their mechanical, photophysical, and antibacterial properties. The films were synthesized using the casting method and their mechanical properties, such as tensile strength and elongation at break, were found to be dependent on the chemical composition and drying process. Infrared spectroscopy and X-ray diffraction analysis were used to examine the chemical structure and degree of structural perfection of the films. The photophysical properties of the films, including absorption spectra, fluorescence detection, emission quantum yields, and lifetimes of excited states, were studied in detail. Rhodamine B-containing films exhibited higher temperature sensitivity and showed potential as fluorescent temperature sensors in the physiological range. The antibacterial activity of the films was tested against Gram-positive bacteria S. aureus and Gram-negative bacteria E. coli, with Rhodamine B-containing films demonstrating more pronounced antibacterial activity compared to blank films. The findings suggest that the elaborated chitosan-based films, particularly those containing Rhodamine B can be of interest for further research regarding their application in various fields such as clinical practice, the food industry, and agriculture due to their mechanical, photophysical, and antibacterial properties.

A Rail-to-Rail Operational Amplifier for Transimpedance Optoelectronic Conversion

The transimpedance conversion circuit is an important part of the fluorescent optical fiber temperature sensor, which is used for rare earth fluorescence detection. Transimpedance conversion circuits can benefit from the wide input range, high gain, low input offset voltage, and high common-mode rejection ratio of rail-to-rail operational amplifiers. In this paper, a constant transconductance rail-to-rail operational amplifier is designed and implemented based on the 0.18 μm CMOS process. According to the simulation results, the transconductance change rate of the operational amplifier is 4.8%, and its gain is 140 dB. The input offset voltage of this operational amplifier is 0.41 μV. Both the power supply rejection ratio and the common-mode rejection ratio have values above 140 dB, with the common-mode rejection ratio reaching as high as 165.4 dB. The transimpedance conversion circuit consists of the operational amplifier designed in this paper. The test results show that the operational amplifier has a certain application value in the transimpedance amplification circuit.

Blue-light-enhanced avalanche photodiode with amulti-finger grating structure for fluorescence detection.

The responsiveness of the photodetectors is critical to the accuracy of the fluorescent fiber optical temperature sensor. However, the current gain and signal-to-noise ratio (SNR) of traditional photodiodes (PDs) is low, which makes it difficult to meet the high-precision detection requirements of the system. In response to the above problems, this paper achieves a novel, to the best of our knowledge, multi-finger grating (MFG) avalanche photodiode (APD). The device combines the polysilicon gate and the space charge region formed by P+/N-Well to detect photon signals. The conversion capability of the photodetector can be significantly enhanced by the MFG structure. The principle of the device is simulated and verified by technology-computer-aided design (TCAD). The standard grating APD (SG-APD), 2-finger grating APD (2FG-APD), 3-finger grating APD (3FG-APD), and 4-finger grating APD (4FG-APD) are fabricated based on 0.18µm CMOS process. The optoelectronic detection characteristics of these devices are analyzed by establishing an optoelectronic test platform. At 480nm, the responsivity of 2FG-APD, 3FG-APD, and 4FG-APD increases by 79.3%, 96.9%, and 70.2%, respectively, compared to SG-APD (4.021A/W). The test results indicate that 3FG-APD exhibits a strong photon response in the blue light range. The device has broad application prospects in the field of fluorescence detection.

Transmissive fluorescent temperature sensor based on Er3+/Yb3+/Mo6+ tri-doped tellurite fiber for real-time thermal monitoring of motors using the FIR technique.

In this paper, we fabricate a transmissive fluorescent temperature sensor (TFTS) that based on Er3+/Yb3+/Mo6+ tri-doped tellurite fiber, which has the advantages of compactness and simplicity, corrosion resistance, high stability and anti-electromagnetic interference. The doping of Mo6+ ions will enhance the up-conversion (UC) fluorescence emission efficiency of Er3+ ions, thus improving the signal-to-noise ratio of TFTS. Using the fluorescence intensity ratio (FIR) technique, the real-time thermal monitoring performance of TFTS is evaluated experimentally. Apart from good stability, its maximum relative sensitivity is 0.01068 K-1 at 274 K in the measured temperature range. In addition, it is successfully used to monitor the temperature variation of the stator core and stator winding of the motor in actual operation. The results show that the maximum error between the FIR-demodulated temperature and the reference temperature is less than 1.2 K, which fully confirms the effectiveness of the TFTS for temperature monitoring. Finally, the FIR-based TFTS in this work is expected to provide a new solution for accurate and real-time thermal monitoring of motors and the like.

Applicability and Limitations of Fluorescence Intensity-Based Thermometry Using a Palette of Organelle Thermometers

Fluorescence thermometry is a microscopy technique in which a fluorescent temperature sensor records temperature changes as alterations of fluorescence signals. Fluorescence lifetime imaging (FLIM) is a promising method for quantitative analysis of intracellular temperature. Recently, we developed small-molecule thermometers, termed Organelle Thermo Greens, that target various organelles and achieved quantitative temperature mapping using FLIM. Despite its highly quantitative nature, FLIM-based thermometry cannot be used widely due to expensive instrumentation. Here, we investigated the applicability and limitations of fluorescence intensity (FI)-based analysis, which is more commonly used than FLIM-based thermometry. Temperature gradients generated by artificial heat sources and physiological heat produced by brown adipocytes were visualized using FI- and FLIM-based thermometry. By comparing the two thermometry techniques, we examined how the shapes of organelles and cells affect the accuracy of the temperature measurements. Based on the results, we concluded that FI-based thermometry could be used for “qualitative”, rather than quantitative, thermometry under the limited condition that the shape change and the dye leakage from the target organelle were not critical.

Design and fabrication of a bimodal emitting phosphor by co-doping two different activators for high sensitivity temperature sensing

Designing of phosphors with multi-emission peaks that show incongruent response to temperature is crucial to design high-efficiency optic fluorescence temperature sensors. Herein, Mn4+ and Dy3+ were co-doped into host lattice Ca2InSbO6 (CIS) with bimodal emissions for fluorescence intensity ratio (FIR) thermometry. The Dy3+-luminescence is insensitive to temperature for its 4f→4f transitions whereas the Mn4+-luminescence is sensitive for its outer 3d→3d transitions. This feature causes almost unchanged intensity of Dy3+-luminescence with increasing temperature and fast decay of Mn4+-luminescence. Utilized the inconsistent temperature dependency of phosphor CIS:Mn4+/Dy3+, highly absolute sensitivity (Sa) of 9.10% K−1 at 573 K and relative sensitivity (Sr) of 2.16% K−1 at 498 K are realized. Additionally, the fluorescence lifetime of Mn4+ is also sensitive to the temperature with Sa of 0.17% K−1 at 348 K and Sr of 1.890 %K−1 at 423 K. This work gives a design idea for researchers in optic temperature sensor field that a phosphor with double activated ions of Dy3+ and Mn4+ is a good choice.

Preparation and characterization of electrospun fluorescent fiber mats as temperature sensors using various polymers

In this study six electrospun fluorescent fiber mats were fabricated using a temperature-sensitive fluorescent dye, a ruthenium complex (tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) dichloride, (Ru(dpp)3)), each with one of six different polymers of polyvinyl alcohol (PVA), polyurethane-based hydrogel HydroMed D4 (D4), polyacrylonitrile (PAN), poly(methyl methacrylate) (PMMA), poly(styrene-co-acrylonitrile) (PSAN), and poly(acrylonitrile-co-methyl methacrylate) (PANMM). The electrospun fluorescent fiber mats were characterized as fluorescence temperature sensors in aqueous solution and gaseous environment. The electrospun fluorescent fiber mat fabricated from PAN showed good stability over 100 days, short response time (i.e. 4-5 min), and good reversibility in aqueous solution from 5 to 60 °C, whereas the electrospun fiber mat from PMMA showed relatively high sensitivity and good selectivity in air. These two electrospun fluorescent fiber mats were tested as non-invasive sensors for measuring temperature in biological and environmental processes.

Linear response for temperature sensing achieved by implanting Er3+ into the grain boundary of transparent MgAlON ceramic

Fluorescence thermometry is considered one of the most perspective temperature sensing techniques. However, few materials reported could combine a wide operating temperature range with stable and high sensing sensitivity. Herein, the fluorescence thermometry based on MgAlON:0.01 at.% Er3+ transparent ceramic was successfully proposed using the idea of local structural engineering, which distributed the Er3+ uniformly into the grain boundary of MgAlON transparent ceramic. It is demonstrated that the special local environment of Er3+ led to different fluorescence responses from those in crystalline or amorphous structures. Instead of the classic Boltzmann exponential relationship, a highly linear downshift fluorescence intensity ratio of thermally coupled energy levels of Er3+ with temperature was exhibited. A novel and constant absolute sensitivity (0.0156 K−1) was obtained within the tested temperature range (300–573 K). This work reveals the significance of the local structure of the activators in the design of high-performance fluorescence temperature sensors.

Isoindolium‐Based Allenes: Reactivity Studies and Applications in Fluorescence Temperature Sensing and Cysteine Bioconjugation

AbstractThe reaction of a series of electron‐deficient isoindolium‐based allenes with sulfhydryl compounds has been studied, leading to the formation of isoindolium‐based vinyl sulfides. The vinyl sulfides generated could be readily converted into the corresponding indanones and amines upon heating at 30–70 °C with good yields up to 61 %. The thermal cleavage reaction of vinyl sulfides was further studied for developing temperature‐sensitive systems. Notably, a novel FRET‐based fluorescent temperature sensor was designed and synthesized for temperature sensing at 50 °C, giving a 6.5‐fold blue fluorescence enhancement. Moreover, chemoselective bioconjugation of cysteine‐containing peptides with the isoindolium‐based allenes for the construction of multifunctional peptide bioconjugates was investigated. Thermal cleavage of isoindoliums on the modified peptides at 35–70 °C gave indanone bioconjugates with up to >99 % conversion. These results indicated the biocompatibility of this novel temperature‐sensitive reaction.

Isoindolium-Based Allenes: Reactivity Studies and Applications in Fluorescence Temperature Sensing and Cysteine Bioconjugation.

The reaction of a series of electron-deficient isoindolium-based allenes with sulfhydryl compounds has been studied, leading to the formation of isoindolium-based vinyl sulfides. The vinyl sulfides generated could be readily converted into the corresponding indanones and amines upon heating at 30-70 °C with good yields up to 61 %. The thermal cleavage reaction of vinyl sulfides was further studied for developing temperature-sensitive systems. Notably, a novel FRET-based fluorescent temperature sensor was designed and synthesized for temperature sensing at 50 °C, giving a 6.5-fold blue fluorescence enhancement. Moreover, chemoselective bioconjugation of cysteine-containing peptides with the isoindolium-based allenes for the construction of multifunctional peptide bioconjugates was investigated. Thermal cleavage of isoindoliums on the modified peptides at 35-70 °C gave indanone bioconjugates with up to >99 % conversion. These results indicated the biocompatibility of this novel temperature-sensitive reaction.

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.

Smartphone-Based Optical Fiber Fluorescence Temperature Sensor

Optical fiber sensors are one preferred solution for temperature sensing, especially for their capability of real-time monitoring and remote detection. However, many of them still suffer from a huge sensing system and complicated signal demodulate process. In order to solve these problems, we propose a smartphone-based optical fiber fluorescence temperature sensor. All the components, including the laser, filter, fiber coupler, batteries, and smartphone, are integrated into a 3D-printed shell, on the side of which there is a fiber flange used for the sensing probe connection. The fluorescence signal of the rhodamine B solution encapsulated in the sensing probe can be captured by the smartphone camera and extracted into the R value and G value by a self-developed smartphone application. The temperature can be quantitatively measured by the calibrated G/R-temperature relation, which can be unified using the same linear relationship in all solid-liquid-gas environments. The performance verifications prove that the sensor can measure temperature in high accuracy, good stability and repeatability, and has a long conservation time for at least 3 months. The proposed sensor not only can measure the temperature for remote and real-time detection needs, but it is also handheld with a small size of 167 mm × 85 mm × 75 mm supporting on-site applications. It is a potential tool in the temperature sensing field.