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Pressure - and temperature-dependent luminescence properties of 3F3/2 → 4I9/2 transition of Nd3+:GdTaO4 were studied for potential applications in optical sensing. Two isolated emission lines correspond to 3F3/2(R2, 1) → 4I9/2(Z5) transitions, locates at 920 and 927 nm under ambient condition, are very sensitive to pressure with coefficients of −15.6 and −14.5 cm−1/GPa determined in a pressure range up to about 9 GPa. The luminescence intensity ratio between the two emission lines exhibits a large dependence with temperature in a range from 80 to 620 K, the corresponding temperature sensitivity at room temperature is similar to that of Nd3+:YAG. These advantages, together with the other observed features of high stable position relationship under pressure and low thermal shifts for the two emission lines indicate that, Nd3+:GdTaO4 is a promising candidate to be used as pressure and temperature sensors in the near-infrared spectral range.

Temperature is a key indicator of infection and disease, however, it is difficult to measure at a cellular level. Nanoparticles are applied to measure the cellular temperature, and enhancement of the stability and reliability of the signal and higher biocompatibility are demanded. We have developed fluorescent polymeric nanoparticles loaded with temperature-sensitive units (as rhodamine B) and internal reference units (as coumarin) for imaging and ratiometric sensing of the cellular temperature in the physiological range. The fluorescence signal of the nanoparticles was stable in the bio-environment and the ratiometric sensing strategy could overcome the concentration effect of nanoparticles. The nanoparticles were endocytosed by cells and partially presented in mitochondria. The fluorescence intensity ratio of rhodamine B and coumarin using nanoparticles showed good linear correlations in buffer solutions, cell suspensions, and imaging of living cells. Using the fluorescent polymeric nanoparticles, the change of temperature of cells during influenza virus infection could be individually monitored.

Temperature sensing enables flammable materials to respond intelligently at high temperature, which is conducive to further improving their fire safety. However, it is still challenging to develop a smart nanocoating with sensitive temperature-sensing and efficient flame retardancy. Inspired by human skin, a thermoelectric flame retardant (TE-FR) nanocoating was fabricated by combining a dermis-mimicking thermoelectric (TE) layer and an epidermis-mimicking flame retardant (FR) layer. The TE-FR nanocoating exhibited accurate temperature sensing at 100–300 ℃ and repeatable fire-warning capability. When being burned, the fire-warning response time of the TE-FR nanocoating was only 2.0 s, and it retriggered the fire-warning device within 2.8 s when it was reburned. Meanwhile, the TE-FR nanocoating exhibited outstanding flame retardancy. The coated polypropylene self-extinguished in the horizontal and vertical burning tests. Besides, its peak heat release rate, total heat release, and peak smoke production rate were significantly reduced. This work proposed an ingenious strategy to fabricate smart nanocoating for temperature sensing and fire safety, which revealed an enticing prospect in the fields of fire protection, electronic skin, and temperature monitor.

Plants dynamically adapt to changing temperatures to ensure propagation and reproductive success, among which morphogenic responses to warm temperatures have been extensively studied in recent years. As readily inferred from the cyclic co-oscillations of environmental cues in nature, plant thermomorphogenesis is coordinately reshaped by various external conditions. Accumulating evidence supports that internal and developmental cues also contribute to harmonizing thermomorphogenic responses. The external and internal reshaping of thermomorphogenesis is facilitated by versatile temperature sensing and interorgan communication processes, circadian and photoperiodic gating of thermomorphogenic behaviors, and their metabolic coordination. Here, we discuss recent advances in plant thermal responses with focus on the diel and seasonal reshaping of thermomorphogenesis and briefly explore its application to developing climate-smart crops.

Distributed temperature sensing (DTS) has been used for fracture parameter diagnosis and flow profile monitoring. In this paper, we present a new model for predicting the temperature profile of two-phase flow multistage fractured horizontal wells in the tight oil reservoirs. The homogeneous reservoir flow/heat transfer model is extended to the tight oil reservoir-fracture-wellbore coupled flow/thermal model. The influence of SRV area on reservoir and wellbore is considered, and the Joule-Thomson effect, heat convection, heat conduction, and other parameters are introduced into the improved model. The temperature distributions of reservoir and wellbore with different production times, water cut, and locations of water entry are simulated. The simulated results indicate that the Joule-Thomson effect will cause wellbore temperature to rise; the temperature of fractures with more water production is significantly lower than that of other fractures, and the water outlet location can be judged according to the temperature change of the wellbore. By using the improved temperature prediction model, the DTS monitoring data of two-phase flow multistage fractured horizontal well in the tight reservoir has been calculated and analyzed, and the accurate production profile has been obtained.

A simply fabricated, highly sensitive, and inexpensive optical fiber temperature sensor is reported with a Fabry–Perot (FP) microcavity of controlled length. The microcavity with controllable length is fabricated by single-mode fiber (SMF) and polydimethylsiloxane (PDMS) for temperature sensing. After the PDMS is cured, the SMF is connected to the supercontinuum light source (SCLS) and the optical spectrometer analyzer (OSA) for online observation of the reflection spectrum. The micro-displacement platform is used to pull the SMF to form an air cavity. After the air cavity is stabilized, ultraviolet (UV) activated glue is used for packaging outside the PDMS. The FP microcavity is formed by the end face of the SMF and the face of PDMS. The length of the FP microcavity can be controlled online by the micro-displacement platform to a minimum of 15 µm. The free spectral range (FSR) may reach 74.8 nm and the interference fringe contrast (IFC) is up to 19.8 dB to allow sensitive measurements across a wide temperature range. The experiments demonstrate a high temperature sensitivity of 5.388 nm/°C from 33 to 93 °C with high repeatability and linearity (R2=0.9937). Stability experiments showed that the maximum changes in wavelength and intensity are only 45 pm and 0.035 dB, respectively. It is anticipated that the easily constructed, compact, and inexpensive fiber-optic temperature sensor will be employed in practical applications.

YGdO3:Er3+ nanoparticles were successfully synthesized by pulsed laser ablation in liquid method. The structural and morphological properties of the product are investigated by X-Ray diffraction and transmission electron microscopy. The upconversion photoluminescence properties were investigated in detail. Obvious stark splitting phenomena were observed in the green and red emission bands. The decay behaviors of three emission bands were studied. Based on thermal coupled energy level related upconversion fluorescence intensity ratio, the temperature sensing properties of product were studied. Linear function has beenused to reveal the relationship between fluorescence intensity ratio and temperature. Using stark sublevels related emission bands, sensitivity of the temperature sensor was successfully enhanced. These results suggest the YGdO3:Er3+ nanoparticles prepared via pulsed laser ablation in liquid are promising luminescent materials for optical thermometry.

The urgent requirement of monitoring air pollution worldwide evokes intensive research interest in developing chemiresistive gas sensing techniques. To overcome the limits in sensitivity and selectivity of room temperature (RT) chemiresistive sensing materials, a new strategy using single-atom catalysts (SACs) via surface coordination is proposed. As a proof-of-concept, single Pd atoms on TiO2 (Pd1-TiO2) possess high efficiency in generating adsorbed O2- as well as high activity and selectivity in catalyzing CO oxidation at RT. As a result, Pd1-TiO2 shows record high sensitivity among the reported RT sensing materials, which is even comparable to those of the best materials working at high temperature. It also provides an approximately 1 order of magnitude lower limit of detection than the best CO sensing materials. Moreover, Pd1-TiO2 presents high selectivity toward 12 kinds of interference gases. This work not only paves a way to design high-performance RT gas sensing materials but also extends the application of SACs.

Water pipelines are the efficient and reliable way for water transportation. Leakage of pipelines can lead to tremendous waste of water resources and large economic loss. In this paper, a novel leakage detection method was proposed based on active thermometry and fiber Bragg grating (FBG) based quasi-distributed fiber optic temperature sensing. In this method, the thermal sensing cable was fabricated by coupling heating cable with quasi-distributed temperature sensors. The heat was introduced by the heating cable and the temperature response was measured by the quasi-distributed fiber optic temperature sensor concurrently. The leakage can be detected and located by identifying the local low values in the temperature profile along the pipelines. The feasibility of the proposed method was validated by finite element simulation and experimental investigation. Good agreement between simulation and experimental study was achieved. The results confirmed the effectiveness of the proposed method for leakage detection.

Non-contact temperature sensors have important application prospects in the optoelectronic field, and their highly sensitive response to wide-range temperature changes is an important development direction. Herein, we propose an Eu2+-activated Sr3−xLa1+xP3−xSixO12 phosphor which shows an outstanding ratiometric temperature sensing performance over a super broad temperature range from 303 to 533 K (a relative sensitivity Sr of ≥1% K−1 and a repeatability capability of over 99%). The structural and luminescence investigations reveal an uncommon phenomenon, i.e. Eu2+ ions were located at a single crystallographic site but produced two emission bands due to the disordering of O1 and O2. As confirmed by the theoretical Debye temperature, the rigid and soft local structures of O1 and O2 coordinated to Eu2+ lead to the thermally stable purple and thermally sensitive yellow emission bands, respectively. Our findings offer useful inspiration for investigating high-performance luminescent thermometers and understanding the structure–property relationships in materials science.

Heating at the nanoscale is the basis of several biomedical applications, including magnetic hyperthermia therapies and heat-triggered drug delivery. The combination of multiple inorganic materials in hybrid magnetic nanoparticles provides versatile platforms to achieve an efficient heat delivery upon different external stimuli or to get an optical feedback during the process. However, the successful design and application of these nanomaterials usually require intricate synthesis routes and their magnetic response is still not fully understood. In this review we give an overview of the novel systems reported in the last few years, which have been mostly obtained by organic phase-based synthesis and epitaxial growth processes. Since the heating efficiency of hybrid magnetic nanoparticles often relies on the exchange-interaction between their components, we discuss various interface-phenomena that are responsible for their magnetic properties. Finally, followed by a brief comment on future directions in the field, we outline recent advances on multifunctional nanoparticles that can boost the heating power with light and combine heating and temperature sensing in a single nanomaterial., Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas

Temperature is one of the physical parameters that affects the emission luminescence properties of upconversion (UC) materials. Temperature-dependent emission color tuning and good temperature sensitivity in multifunctional β-NaYF4:Yb/Er@β-NaYF4:Yb/Tm microcrystals were achieved under 980 nm excitation. Based on the different emission bands (blue, green and red bands) and spectral sensitivities of the core–shell structured microcrystals to temperature, intense white-light emission was obtained at room temperature and a real-time naked-eye recognizable emission color change from white to the purplish-pink region was realized with the temperature increasing from 300 to 500 K. Furthermore, optical temperature sensing properties of the sample with good sensitivity (from 0.0034 to 0.0044 K−1) were investigated by using a fluorescence intensity ratio between 521 nm (2H11/2 → 4I15/2 transition) and 540 nm (4S3/2 → 4I15/2 transition) in the temperature range from 300 to 500 K. The results indicate that the sample has high sensitivity in a relatively wide range of temperature intervals, especially in the low temperature region. We believe that the multifunctional core–shell structured microcrystals exhibit promising applications in white-light emitting diodes, the anti-counterfeiting field, and temperature sensing.

A novel high sensitivity temperature sensor based on polydimethylsiloxane (PDMS) coated the Multi-Thin-Multi mode Fiber was presented. The reliable material PDMS with higher negative thermal optical coefficient and thermal expansion coefficient was selected to improve the sensitivity of the optical fiber’s temperature sensing. A section of thin-mode fiber was connected in the middle of two multi-mode fibers, so as to form the Multi-Thin-Multi mode Fiber structure, which can make the light in the cladding better interact with the external PDMS. For the two dips of the interference spectra, the temperature sensitivities of the original fiber sensor were 47.14 pm/°C and 0.093 dB/°C. After the sensing part of the fiber was coated, its temperature sensitivities were become as 75.04 pm/°C and 0.231 dB/°C, which 1.6 and 2.5 times improved, respectively. In the temperature stability experiment, a standard deviation of the wavelength variation was established to demonstrate the good stability of the sensor.

New luminescent cage-like tetranuclear silsesquioxanes [NEt4][(Ph4Si4O8)2(Tb3Eu)(NO3)4(OH)(EtOH)3(H2O)]·4(EtOH) (1) and [NEt4]2[(Ph4Si4O8)2(Tb2Eu2)(NO3)6(EtOH)2(MeCN)2]·4(MeCN) (2) present a tunable thermosensitive Tb3+-to-Eu3+ energy transfer driven by Tb3+ and Eu3+ emission and may be used as temperature sensors operating in the range 41–100 °C with excellent linearity (R2 = 0.9990) and repeatability (>95%). The thermometer performance was evidenced by the maximum relative sensitivity of 0.63% °C−1 achieved at 68 °C.

Realizing multicolored luminescence in two-dimensional (2D) nanomaterials would afford potential for a range of next-generation nanoscale optoelectronic devices. Moreover, combining fine structured spectral line emission and detection may further enrich the studies and applications of functional nanomaterials. Herein, a lanthanide doping strategy has been utilized for the synthesis of 2D ZnSe:Er

An epicardial bioelectronic patch is an important device for investigating and treating heart diseases. The ideal device should possess cardiac-tissue-like mechanical softness and deformability, and be able to perform spatiotemporal mapping of cardiac conduction characteristics and other physical parameters. However, existing patches constructed from rigid materials with structurally engineered mechanical stretchability still have a hard–soft interface with the epicardium, which can strain cardiac tissue and does not allow for deformation with a beating heart. Alternatively, patches made from intrinsically soft materials lack spatiotemporal mapping or sensing capabilities. Here, we report an epicardial bioelectronic patch that is made from materials matching the mechanical softness of heart tissue and can perform spatiotemporal mapping of electrophysiological activity, as well as strain and temperature sensing. Its capabilities are illustrated on a beating porcine heart. We also show that the patch can provide therapeutic capabilities (electrical pacing and thermal ablation), and that a rubbery mechanoelectrical transducer can harvest energy from heart beats, potentially providing a power source for epicardial devices. An epicardial patch made from materials that match the mechanical softness of heart tissue can perform spatiotemporal mapping of electrophysiological activity, as well as strain and temperature sensing, pacing and ablation therapies, and energy harvesting, while deforming with a beating heart.

Distributed temperature sensing (DTS) uses Raman scatter from laser light pulsed through an optical fiber to observe temperature along a cable. Temperature resolution across broad scales (seconds to many months, and centimeters to kilometers) make DTS an attractive oceanographic tool. Although DTS is an established technology, oceanographic DTS observations are rare since significant deployment, calibration, and operational challenges exist in dynamic oceanographic environments. Here, results from an experiment designed to address likely oceanographic DTS configuration, calibration, and data processing challenges provide guidance for oceanographic DTS applications. Temperature error due to suboptimal calibration under difficult deployment conditions is quantified for several common scenarios. Alternative calibration, analysis, and deployment techniques that help mitigate this error and facilitate successful DTS application in dynamic ocean conditions are discussed.

Temperature sensor plays a significantly important role in the areas of biology, chemistry and engineering, especially the one can work accurately in a noninvasive manner are extremely attractive. We adopt photoinduced postsynthetic copolymerization strategy and realize membranous ratiometric luminescent thermometer based on emissions of two lanthanide ions. This novel mixed lanthanide polyMOF membrane exhibits not only the integrity and temperature sensing nature of Ln-MOF powder, but also excellent mechanical properties, such as flexibility, elasticity and processability. Moreover, the polyMOF membrane shows remarkable stability under harsh conditions, including high humidity, strong acid and alkali (pH 0-14), allowing to mapping the temperature distribution in extreme circumstances. This work highlights a simple strategy for polyMOF membrane formation and pushes forward the further practical application of Ln-MOFs based luminescent thermometer in various fields and conditions.

The multi-functional materials with temperature sensing and multi-color imaging have broad application prospects in our daily life. A novel temperature-sensing technique facilitates the self-referencing thermometry probe to possess high sensitive, excellent repeatability and superior temperature resolution. Herein, temperature dependences of the emission spectra in carbon dots (CDs)/YVO4:Eu3+ composite are investigated at temperatures ranging from 313 K to 448 K. Furthermore, the non-toxic polyacrylic acid (PAA) is also introduced to prepare a uniform anti-counterfeit ink, which can significantly improve the afterglow performance by further hardening the CDs. Particularly, CDs/YVO4:Eu3+/PAA composites exhibit multi-mode emission color tuning in advanced optical anti-counterfeiting.

Flexible coatings with dual capabilities for remote real-time temperature sensing and photothermal conversion have a huge potential in the field of advanced thermal actuated optoelectronic applicat...

A series of garnet-structured Li6Ca(La0.99-xYbxEr0.01)2Nb2O12 (0≤x≤0.05) phosphors were originally synthesized and examined for upconversion (UC) luminescence and optical temperature sensing under 978 nm laser excitation. It was identified that the optimal content of Yb3+ sensitizer is x=0.04 for Er3+ emission and the non-thermally coupled 2H11/2/4F9/2 energy levels of Er3+ possess a superior capability of optical thermometry, whose maximum absolute sensitivity (~15.20 × 10−3 K−1 at 523 K) is generally ~1.7-6.1 times the values reported to date for most of other UC systems.

1. Many plant species in fire‐prone environments maintain persistence through fire via soil seedbanks. However, seeds stored within the soil are at risk of mortality from elevated soil temperatures during fire. Seeds may be protected from fire‐temperature impacts by burial, however, those buried too deeply may germinate but fail to emerge. Thus, successful post‐fire seed regeneration is contingent upon a trade‐off between burial depth and survival through fire. 2. We examined the relationships between seedling emergence behaviour, seed survival and soil temperatures during fire in 13 native and four non‐native woodland species in southwestern Australia. We assessed total seedling emergence per depth, maximum seedling emergence depth and seedling emergence speed from seeds planted at eight depths (0, 1, 2, 3, 4, 5, 7, 10 cm). Soil temperatures were quantified using distributed temperature sensing in optic fibre (DTS), measured continuously between 1 and 10 cm in depth (temperatures were subsequently categorized into 1 cm increments for analysis) during five experimental fires in beds with fine fuels manipulated between 8 and 20 t/ha. Using seed survival and emergence success relative to soil temperatures, we determined vulnerability of seedling emergence relative to soil temperatures generated by combustion of fuel quantities typically observed in woodlands. 3. Maximum depth of emergence varied between species from 2 to >10 cm, with a positive linear correlation to seed mass. Maximum soil temperatures from the two highest fuel masses exceeded seed lethal thresholds (T 50—representing temperatures lethal to 50% of seeds) of at least five species. Lethal temperatures were exceeded at all potential emergence depths for all three grass species, and all four non‐native species studied. Of the remaining 10 species, temperatures did not exceed the lethal thresholds under any of the fuel mass levels tested. We found no relationship between lethal temperature thresholds and maximum emergence depth. 4. Our data demonstrate that seeds exhibit variation in their response to soil heating and capacity to emerge from depth, with three distinct functional responses amongst our study species, which enable persistence through, and recruitment following, fire. Such variation in species attributes and fuel mass may lead to heterogeneity (within fires) or divergent trajectories (among fires) in community response under changed fire regime.

A selective and sensitive method for detecting rutin using MoS2 quantum dots (QDs) as a fluorescent probe is reported in the paper, a one-step hydrothermal synthesis method was used to prepare MoS2 QDs. The synthesized MoS2 QDs had good stability and water solubility, and the fluorescence of MoS2 QDs was quenched by rutin due to the inner filter effect. There was a good linear relationship between the intensity of MoS2 QDs and rutin concentration ranging from 5.0 × 10-7 to 3.2 × 10-5 mol/L with a detection limit of 3.5 × 10-7 mol/L. MoS2 QDs showed temperature-dependent fluorescence that had an excellent linear relationship between 20 and 80°C. Therefore MoS2 QDs can be used as specific fluorescence sensors for selection of rutin and for temperature sensing.

In this paper, upcovnerison luminescence in Er3+/Yb3+ co-doped NaYF4 nanophosphors was regulated by changing the Er3+ concentration. With increasing the Er3+ concentration, the green and red emissions increased first and then decreased, but the intensity ratio of red to green emission decreased monotonically. To clarify the role of Er3+ doping, the factors including crystal structure, morphology and size of particle, photon absorption, energy transfer, multi-phonon relaxation, population of emissive levels and emission probability of radiative transitions were considered and analyzed. More importantly, we proposed a simple method for discussing radiation transitions based on luminescence temperature sensing.

Lanthanide ion doped upconversion nanomaterials have attracted great interest because of their extensive application, especially in color display and temperature sensing. However, control synthesis...

Based on the luminescence of Bi3+, novel temperature sensing materials YNbO4:Bi3+ and YNbO4:Bi3+/Sm3+ were successfully synthesized by solid state reaction. The XRD patterns show that the synthesized materials have a pure phase of YNbO4. With the excitation of 314 nm, the YNbO4:Bi3+ material shows intense temperature-dependent luminescence in the range of 303 K–463 K. Based on the temperature-dependent luminescence of Bi3+ in YNbO4, the maximum relative sensitivity can be obtained at 434 K (1.72% K−1). Under the excitation of 406 nm, the YNbO4:Sm3+ material shows the characteristic emission peaks of Sm3+. In YNbO4:Bi3+/Sm3+ phosphor, the large overlap between the emission spectra of Bi3+ and the excitation spectra of Sm3+ leads to a significant energy transfer from Bi3+ to Sm3+. With the excitation of 314 nm, the emission spectra of YNbO4:Bi3+/Sm3+ material shows the characteristic peaks of Bi3+ and Sm3+. The luminescence intensity ratio of Sm3+ and Bi3+ shows a strong temperature dependence. Based on the luminescence intensity ratio, a large relative sensitivity is obtained at 455 K (1.57% K−1).

A twin-core sensor with high birefringence employing a photonic crystal fiber (PCF) is presented for simulated temperature measurements based on surface plasmon resonance (SPR). The internal wall of the central hole of the PCF is plated with gold and coated with graphene oxide (Au-GO) to develop an SPR sensing channel. The results of a numerical analysis with COMSOL Multiphysics show that the birefringence of this sensing structure can reach 0.0052. In addition, an average sensitivity of -12.695 nm/ °C can be achieved in the range of 0 °C~80 °C. Compared with uncoated GO sensors and existing sensing units, this sensor shows improved stability, sensitivity and birefringence.

Er3+ doped potassium sodium niobate (KNN: Er) ultrafine powders have been prepared by pulsed laser ablation in water. X-ray diffraction (XRD) pattern of the sample demonstrated that the as-synthesized powders were crystalized in orthorhombic phase. Scanning electron microscopy (SEM) and transmittance electron microscopy (TEM) images exhibited that the morphology of ultrafine powders are cube-like. Under the excitation of 980 nm laser, the sample exhibits green emission, which is originated from the transition of thermal coupled energy levels (2H11/2, 4S3/2) to ground state level 4I15/2. Temperature dependent up-conversion emission intensity associated with thermal quenching of total green emission band and the fluorescence intensity ratio (FIR) between two sub-emission bands related to population of thermal coupled energy levels are investigated for temperature sensing in the temperature range of 300 K to 480 K. The temperature sensing performances related to different technique were discussed. A maximum relative sensitivity reaches 1.01% K-1 at 464 K for emission intensity thermometry and that is 0.84% K-1 at 374 K for FIR thermometry technique. All these results show that KNN: Er ultrafine phosphors prepared via pulsed laser ablation in water have prospect for non-contact temperature sensing.

Native defects are highly prevalent in vanadium pentoxide (V2O5) as it can easily get converted into reduced oxides. The role of defects in gas sensing properties of V2O5 nanostructures, however, are not well understood. In the present report, effect of native defects on near room temperature sensing is reported for the first time. Hydrothermally grown V2O5 nanoparticles with substantial sensor response to CH4 close to room temperature at 50 °C is presented. Fast response and recovery times of 43 s and 75 s, respectively, for 500 ppm CH4 gas at optimum operating temperature of 150 °C were observed. Temperature dependent photoluminescence studies were carried out to understand the role of native defects and their emission behavior leading to carrier saturation in realizing optimum operating temperature.

Ca2YZr2Al3O12:Bi3+,Eu3+ phosphors were elaborated by a traditional solid-state reaction method. The luminescence of Ca2YZr2Al3O12:Bi3+ samples, energy transfer from Bi3+ to Eu3+, and the temperature sensing properties of Ca2YZr2Al3O12:Bi3+,Eu3+ samples have been systematically researched. Under the excitation of ultraviolet light, Bi3+ single doped phosphors give 313 and 392 nm emission bands, which origin from the substitutions of Bi3+ instead of Ca2+ and Y3+ sites, respectively. And the color-adjustable emission from blue to red were observed by increasing Eu3+ content in Ca2YZr2Al3O12:Bi3+,Eu3+ samples. Relying on different temperature dependent variation tendency, the fluorescence intensity ratio (FIR) values present outstanding temperature sensing properties. The absolute and relative sensitivity can be up to 0.826 %K-1 and 0.664 %K-1, respectively. All above results suggest that Ca2YZr2Al3O12:Bi3+,Eu3+ phosphor is a potential alternative for optical thermometer.

We introduce a technique based on infrared thermal emission, termed depth thermography, that can remotely measure the temperature distribution beneath the surface of certain objects. Depth thermogr...

This work was supported by the Associated Laboratory for Sustainable Chemistry‐Clean Processes and Technologies – LAQV which is financed by national funds from FCT/MEC (UID/QUI/50006/2019) and co‐financed by the ERDF under the PT2020 Partnership Agreement (POCI‐01‐0145‐FEDER – 007265) The NMR spectrometers are part of The National NMR Facility, supported by Fundação para a Ciência e a Tecnologia (RECI/BBB‐BQB/0230/2012). We also thank to RNEM – Portuguese Mass Spectrometry Network, ref. LISBOA‐01‐0145‐FEDER‐022125, supported by FCT and Lisboa Regional Operational Programme (Lisboa2020). This work has been supported by Fundação para a Ciência e a Tecnologia through the contract n° IST‐ID/077/2018 (Bernardo Monteiro), SFRH/BD/120985/2016 (Mani Outis). Cláudia C. L. Pereira thanks to Fundação para a Ciência e a Tecnologia, MCTES, for the Norma transitória DL 57/2016 Program Contract. An unusual thermally sensitive anion–cation interaction, which is characteristic of the anion [Eu(FOD)4]−, occurs in the complex [CHOL][Eu(FOD)4] (1; CHOL=choline; FOD=1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedionate) and affects both quantum yield and thermochromic behavior. This prompted the design of an Eu3+-based ratiometric thermometer that functions at temperatures up to 95 °C through a thermally excited state absorption of the Eu3+ ion. The reusable temperature-sensitive luminescent complex showed a range of relative sensitivity between 0.45 % C−1 at 25 °C, with an increase to 7.0 % C−1 at 95 °C. Confinement of compound 1 in a transparent film of polysulfone resulted in a higher thermal stability of 1 while its luminescence showed a strong temperature dependence. authorsversion published

In this paper, we propose the use of a dual wavelength scheme for active distributed temperature sensing based on Co2+-doped fibers. A Brillouin Optical Frequency-Domain Analysis (BOFDA) set-up, operating at 850 nm, is used to detect the temperature changes along Co2+-doped optical fibers with various absorption coefficients, while optical heating is performed through a 1550-nm optical pump. A simple model describing optical heating along the Co2+-doped fiber is introduced and experimentally validated. As a proof of concept, we demonstrate that the sensor is capable to distinguish a 1-m portion of fiber immersed into water, from a section of equal length surrounded by air.

This paper presents reports on the preparation of a multifunctional coating system, CrNx, with temperature sensing capability. A systematic study of the thermo-resistive effect of chromium nitride (CrNx) thin films with a negative temperature coefficient of resistance (TCR) has been carried out. The CrNx nanostructures were grown by reactive magnetron sputtering under distinct Ar+N2 conditions. To confer a zigzag columnar morphology to the CrNx we explored the oblique angle deposition technique. The structural properties have been studied through X-ray diffraction and Scanning Electron Microscopy. The thermo-resistive response was evaluated by measuring the electrical resistivity as a function of temperature by the twopoint method. The results observed for the CrNx films produced with N2 flux between 4 and 8 sccm present an stable and negative TCR. Values of -9.1710-4 , -5.3110-3 , and -1.47610-2 were observed for the films grown with 4, 6, and 8 sccm, respectively. The grain-boundary was used to theoretically describe our results. The results open new technological possibilities for the application of CrNx coatings for esistive temperature detector (RTD) systems., The authors thank the Portuguese Foundation for Science and Technology (FCT) for the strategic funding UID/FIS/04650/2020. A. Ferreira thanks the FCT for the contract under the Stimulus of Scientific Employment (CTTI-31/18 - CF (2) junior researcher contract) . M. A. Correa thanks the CNPq and CAPES. The authors acknowledge funding by the Basque Government Industry and Education Departments under the ELKARTEK and PIBA (PIBA-2018-06) programs, respectively, and to European Regional Development Fund under the Operational Program Cdompetitiveness and InternationalizationdResearch and Development (R&D) and Innovation to SMEs - R&D Individuals Projects, grant agreement no 038397.

A new series of CaY2–10xYb9xErxGe3O10 trigermanates (space group P21/c, Z = 4) has been synthesized using an EDTA-assisted method. Under 980 nm laser diode excitation, the samples exhibit intense upconversion luminescence corresponding to the characteristic transitions 2H9/2 → 4I15/2 (400–420 nm), 2H11/2,4S3/2 → 4I15/2 (500–600 nm) and 4F9/2 → 4I15/2 (625–725 nm) in Er3+ ions. The CaY1.5Yb0.45Er0.05Ge3O10 phosphor can be used as a good temperature sensor with high absolute and relative sensitivities Sa(max) = 0.0051 K−1 and Sr(max) = 0.0109 K−1.

In this paper, optical fibre Bragg grating (FBG) and no-core fibre (NCF) sensors have been investigated for their performance in the temperature range 30–100 °C. The change in Bragg and NCF wavelengths with temperature changes was used to determine the performance and sensitivity of the sensors. The gradient of Δ $$ \lambda_{\text{FBG}} $$ and $$ \lambda_{\text{NCF}} $$ versus temperature leads the sensitivity of the FBG and NCF sensors as 23.97 and 20.08 pm/°C, respectively.

In this work, temperature-dependent optical properties of refractory plasmonic transition metal nitrides and dielectric thin films are utilized to design and realize a planar, direct-contact, nanop...

Recent waste rock pile designs have been proposed to incorporate a fine-grained layer to create a capillary barrier to prevent surface water from draining into the pile interior. This study analyses active fibre optic distributed temperature sensing (FO-DTS) as a tool to measure the effectiveness a capillary barrier system following an infiltration test. A laboratory waste rock column was built with anorthosite waste rock overlain by sand. Volumetric water content is calculated during heat cycles lasting 15 min powered at 15 W/m in the column. A new algorithm is employed to circumvent several requirements for soil specific calibration. The inferred moisture contents were verified by soil moisture probes located adjacent to the cable. The FO-DTS data indicate, at vertical resolutions up to 2 cm, that water is retained in the sand and does not drain into the anorthosite following the infiltration test. The coefficient of determination, R2, between the inferred and measured volumetric water content in the fine cover sand layer is 0.90, while the screened anorthosite maintained an R2 of 0.94 with constant moisture content throughout the test. This study will ultimately help guide future waste rock storage design initiatives incorporating fibre optic sensors, leading to improved environmental mine waste management.

In this paper, new upconversion (UC) phosphors for Yb3+-Er3+- and Yb3+-Ho3+-doped Gd9.33(SiO4)6O2 (GSO) were designed via a solid-state reaction method. The phase purity of the samples was examined using XRD patterns. In Yb3+-Er3+ -doped GSO, the characteristic emission peaks of Er3+ appear upon 980 nm excitation, and the optimum Er3+ concentration was found to be 1 mol%. Different changes in the intensity of green and red emissions with Er3+ concentration appeared, and were interpreted by cross-relaxation between Er3+ ions. In Yb3+-Ho3+-doped GSO, three emission peaks of Ho3+ were observed, and the power-dependent UC luminescence was studied. For studying the temperature-sensing properties, different strategies were employed, including thermally coupled levels and non-thermally coupled levels. High sensitivities were obtained in the phosphors, and GSO:Yb3+,Er3+ showed the highest sensitivities. The above investigation results indicated that the developed GSO:Yb3+-Er3+/Ho3+ phosphors could have potential applications in optical thermometry.

Afterglow including thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP) has stimulated considerable attention owing to bright potential applications in optoelectronic devices, sensing, and security systems. However, previously reported afterglow materials are mostly single-mode (one of RTP or TADF only), a tunable multi-mode afterglow emission is still rarely achieved. Herein, we report the temperature-responsive conversion characteristics of TADF and RTP of carbon dots in silica (CDs@SiO2) for the first time. The unique temperature-responsive afterglow characteristics, that is, phosphorescence and TADF can be mutually transformed as the temperature changes, resulting in the free conversion of the RTP/TADF ratio as well as the afterglow color change through simple temperature control. The Si–O network plays multiple roles to strengthen and confine the embedded CDs, thus resulting in ultralong RTP emission and unique afterglow characteristics. Furthermore, CDs@SiO2 exhibited excellent stability against water, acid, alkali, salt and oxidants as well as polar solvents. CDs@SiO2 with unique afterglow characteristics and high stability can have multiple potential applications in rapid fingerprint detection and temperature sensing, especially in advanced temperature-responsive multicolor anti-counterfeiting and encryption.

It is meaningful but challenging to develop a fluorescent probe for temperature sensing in living cells because it should possess the features of good cytocompatibility, easy read out, and high resolution. Herein, we successfully synthesized emissive star-like cage-based organic temperature-sensitive polymers that can assemble into nanoparticles in aqueous solution. The obtained nanoparticle can be easily tuned to full-color emission (including white light emission) with a temperature resolution of at least 0.5 °C by encapsulating different doses of guest dyes ((4-dimethylamino-2'-butoxychalcone (DMBC) and Nile Red (NR)) through a cascade Förster resonance energy transfer (FRET) effect. Moreover, the white light emission polymeric hybrid nanoparticles exhibit reversible stimuli response toward temperature and can be used as probes for temperature sensing in live cells through their fluorescent color variation between white and orange emission with good cytocompatibility.

In this work, the up-conversion luminescence of Yb 3 + /Er 3 + doped Gd2O3 phosphors for optical temperature sensing in green and red regions are investigated. The intense green (522 and 562 nm) and red emissions (660 and 682 nm) radiated from Er 3 + /Yb 3 + tri-doped Gd2O3 phosphors are successfully realized via tuning the doping proportion of Er 3 + and Yb 3 + . To evaluate their potential ability of optical thermometry in green light range and the first biological window, the temperature-dependent green and red emissions are investigated. Based on the florescence intensity ratio (FIR) of 522 and 562 nm, the absolute sensing sensitivities of Gd2O3: 1 mol% Er 3 + /4 mol% Yb 3 + and Gd2O3: 1 mol% Er 3 + /6 mol% Yb 3 + phosphors reach 1.16 and 1.2% K−1 (523 K), respectively. In addition, the temperature sensing sensitivities based on the FIR of 660 and 682 nm reach 0.8 and 0.6% K−1 (300 K), respectively. Moreover, the changes of FIR ( Δ R) are smaller than 3% within the cycling heat and cool processes. These results reveal that Gd2O3:1mol%Er/4(6)mol%Yb phosphors are promising for FIR-based temperature sensing in high temperature via green emissions and room temperature via red emissions.

We demonstrated a linear-cavity fiber laser using a fiber Bragg grating (FBG) fabricated by femtosecond laser and a Sagnac loop as cavity mirrors. The temperature sensing response of the fiber laser was characterized by placing the FBG in a high-temperature environment. The stability of the fiber laser at high temperature was improved after the FBG was annealed at 1100 °C. The fiber laser can work stably as a temperature sensor at 1000 °C and its temperature sensing sensitivity is approximately 15.9 pm/°C from 300 °C to 1000 °C.

A dual-emissive optical sensor based on the fluorescence intensity ratio (FIR) technique has been demonstrated to have significant advantages of high sensitivity and reliability. Here, we designed ...

Phase-pure eulytite-type Sr3Y0.88(PO4)3:0.10Yb3+,0.02Ln3+ upconversion (UC) phosphors (Ln = Ho, Er, Tm) were synthesized via gel-combustion and subsequent calcination at 1250°C. Their UC luminescence, temperature-dependent fluorescence intensity ratio of thermally and/or non-thermally coupled energy levels, and performance of optical temperature sensing were systematically investigated. The phosphors typically exhibit green, orange-red and blue luminescence under 978 nm NIR laser excitation for Ln = Er, Ho and Tm, respectively, which were discussed from two- and three-photon processes. The 524 nm green (Er3+), 657 nm red (Ho3+) and 476 nm blue (Tm3+) main emissions were analyzed to have average decay times of ~52 ± 2, 260.6 ± 0.7 and 117 ± 1 μs, respectively. It was shown that (1) the Er3+ doped phosphor has a better overall performance of temperature sensing with thermally coupled 2H11/2 and 4S3/2 energy levels, whose maximum absolute (SA) and relative (SR) sensitivities are ~5.07 × 10−3 K−1 at 523 K and ~1.16% at 298 K, respectively; (2) the Ho3+ doped phosphor shows maximum SA and SR values of ~0.019 K−1 (298–573 K) and 0.42% at 573 K for the non-thermally coupled energy pairs of 5F5/(5F4,5S2) and 5I4/5F5, respectively; (3) the Tm3+ doped phosphor has a maximum SA of ~12.74 × 10−3 K−1 at 573 K for the non-thermally coupled 3F2,3/1G4 energy levels and a maximum SR of ~1.74% K−1 at 298 K for the thermally coupled 3F2,3/3H4 levels. Advantages of the current phosphors in optical temperature sensing were also revealed by comparing with other typical UC phosphors.

A series of Ce3+ and Dy3+ doped LiY9(SiO4)6O2 phosphors was prepared by conventional high temperature solid state reaction method. The dominant emission of Dy3+ originates from the 4F9/2 → 6H13/2 (yellow emission) electric dipole transition while that of Ce3+ locates in the blue region. The concentration quenching for Dy3+ emission was investigated by luminescence spectra and decay curves, the main mechanism responsible for the energy transfer between Dy3+ ions was determined by the Inokuti-Hirayama model. Energy transfer from Ce3+ to Dy3+ as well as the temperature sensing property was studied in detail. Thanks to the different thermal responses between Ce3+ and Dy3+ in the host, the highest sensing sensitivity was calculated to be 0.43% K−1. The results demonstrate that LiY9(SiO4)6O2: Ce3+, Dy3+ may be a potential candidate for a luminescent ratiometric thermometer.

Herein, we reported Er3+/Yb3+ co-doped CaLaAl3O7 up-conversion phosphors synthesized via solid state reaction, which was further explored as a new optical thermometry. The luminescent properties of Er3+ or Er3+/Yb3+ doped CaLaAl3O7 phosphor was studied in detail. The two-photon process for the green emissions of Er3+ were confirmed by the power-dependent luminescence. The up-conversion optical temperature sensing performances of the Er3+/Yb3+-codoped CaLaAl3O7 phosphor were investigated based on the FIR technique. The maximum sensitivity of this phosphor can reach about 0.00345 K−1 at 453 K, which reveals this phosphor can be a promising candidate for optical thermometry devices.

This paper presents a low-cost and high-sensitivity temperature sensor based on an isopropanol-sealed multimode microfiber (MMMF). Isopropanol is a kind of material with a high thermo-optic coefficient. Refractive index (RI) of isopropanol changes with the surrounding temperature variation allowing high-sensitivity temperature sensing. By inserting the MMMF into an isopropanol-sealed capillary, a simple and highly sensitive fiber temperature sensor is implemented. Theoretical and experimental results demonstrate that the tapered multimode fiber can efficiently excite high-order cladding modes, the MMMF can enhance the multimode interference and increase the interaction between the evanescent wave and the isopropanol. The characteristics of the measured transmission spectra under different conditions are evaluated. Experimental results demonstrate that the temperature sensitivity increases with the decreasing diameter of MMMF. The maximum temperature sensitivity of −4.12 nm/°C is obtained over the range of 30 °C–50 °C. This packaging technology not only offers a more stable structure but also improves the temperature sensitivity for the thermo-optic effect of isopropanol and the thermal expansion effect of packaging materials.

Developing an alternative solution to reduce or not use the rare-earth ions is of much importance. Tunable up-conversion (UC) multicolor luminescence is realized by utilizing the green UC emission of the intrinsic defects and optimizing the doping contents of Yb3+ and Tm3+ ions in the Na0.5Bi0.5-x-yYbxTmyTiO3 (NBT:xYb/yTm) ceramics. The UC white-light emission, which is close to the standard achromatic point, is achieved by an optimal design. And the possible up-conversion emission mechanism of defects and Tm3+/Yb3+ ions is also discussed. In addition, the optical temperature sensing properties were also investigated basing on the UC emission of defects in a temperature range from 83 to 683 K. The results indicate that the NBT:xYb/yTm is promising for the application as optical thermometry materials.