Primary Thermometer Research Articles

Repeatability of a primary thermometer and calibration of resistance thermometers between 5 K and 25 K

Repeatability of a primary thermometer and calibration of resistance thermometers between 5 K and 25 K

Expanding the Toolbox for Industrial Luminescent Primary Thermometry: Er3+-doped SrMoO4

We herein demonstrate the feasibility of employing strontium molybdate as host matrix for trivalent erbium ions for the developing of an optical temperature sensor operating in a wide temperature range suitable for industrial applications. This class of metal molybdate, known for its chemical and thermal capabilities, works as primary luminescent thermometer, relying on the thermally coupled levels of Er3+ arising from downshifting processes, neglecting first, the requirement of calibration curve acquisition and second, the excitation induced heating on the sample typically observed in upconverting luminescent thermometers. The synthesised primary optical thermometer displays a maximum temperature relative sensitivity of 1.13 %. K−1 and minimum temperature uncertainty and 0.09 K. These values make the performance of the Er3+-doped strontium molybdate as optical temperature sensor competitive with the existing luminescent primary thermometers, including a wide operating temperature range up to 413 K and high accuracy as main features. Moreover, it can be easily scaled up and produced due to straightforwardness and cost-effectiveness of the ceramic synthesis method, matching the requirements for its usage in industrial environments.

Yb3+ concentration influence on NIR and upconversion emission and temperature sensing properties of Er3+/Yb3+ co-doped Ta2O5 particles

We synthesized Er3+ and Yb3+ co-doped tantalum oxide (Ta2O5) spherical sub-micrometric particles by a facile method involving formation of tantalum glycolates after pouring in acetone. Then, we investigated how the annealing temperature and Yb3+ concentration (0–30 mol %) affect their structural and luminescence properties. Particle sizes ranged from 146 to 258 nm for the samples annealed at 800 °C. XRD analysis revealed the orthorhombic L-Ta2O5 crystalline structure. The different symmetry sites that the rare earth ions can occupy within the Ta2O5 structure led to intense and broad emission bands centered around 1530 nm. Up-conversion measurements and the calculated number of photons for intense green and red emissions obtained with 980 and 1550 nm excitations helped us to elucidate the mechanisms involved at both excitation wavelengths. We investigated how the 0.5 mol % Er3+/1.5 mol % Yb3+ co-doped Ta2O5 sample performs as a primary thermometer by using the Boltzmann distribution law to predict the absolute temperature from the ratio between the Er3+ 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions. We obtained a maximum relative thermal sensitivity of 0.97 ± 0.04 % K−1 and a minimum δT of 2.41 K. The calculated repeatability was above 95%. These results show that promising nanothermometer based on Ta2O5 with controlled size and morphology can be designed.

Harnessing ligand design to develop primary and self-calibrated luminescent thermometers with field-induced single ion magnet behaviour in Dy3+ complexes

Magneto-luminescent studies on Dy+3 complexes of N6 macrocycles lead to a unique [Dy(LN6prop)(OAc)2](NO3)·CHCl3 luminescent primary thermometer based on 2 thermally coupled levels, which in addition shows field-induced single ion magnet behaviour.

Extending the Palette of Luminescent Primary Thermometers: Yb3+/Pr3+ Co-Doped Fluoride Phosphate Glasses.

The unique tunable properties of glasses make them versatile materials for developing numerous state-of-the-art optical technologies. To design new optical glasses with tailored properties, an extensive understanding of the intricate correlation between their chemical composition and physical properties is mandatory. By harnessing this knowledge, the full potential of vitreous matrices can be unlocked, driving advancements in the field of optical sensors. We herein demonstrate the feasibility of using fluoride phosphate glasses co-doped with trivalent praseodymium (Pr3+) and ytterbium (Yb3+) ions for temperature sensing over a broad range of temperatures. These glasses possess high chemical and thermal stability, working as luminescent primary thermometers that rely on the thermally coupled levels of Pr3+ that eliminate the need for recurring calibration procedures. The prepared glasses exhibit a relative thermal sensitivity and uncertainty at a temperature of 1.0% K-1 and 0.5 K, respectively, making them highly competitive with the existing luminescent thermometers. Our findings highlight that Pr3+-containing materials are promising for developing cost-effective and accurate temperature probes, taking advantage of the unique versatility of these vitreous matrices to design the next generation of photonic technologies.

Progress towards in-situ traceability and digitalization of temperature measurements

Autonomous control systems rely on input from sensors, so it is crucial that the sensor input is validated to ensure that it is ‘right’ and that the measurements are traceable to the International System of Units. The measurement and control of temperature is widespread, and its reliable measurement is key to maximising product quality, optimising efficiency, reducing waste and minimizing emissions such as CO2 and other harmful pollutants. Degradation of temperature sensors in harsh environments such as high temperature, contamination, vibration and ionising radiation causes a progressive loss of accuracy that is not apparent. Here we describe some new developments to overcome the problem of ‘calibration drift’, including self-validating thermocouples and embedded phase-change cells which self-calibrate in situ by means of a built-in temperature reference and practical primary thermometers such as the Johnson noise thermometer which measure temperature directly and do not suffer from calibration drift. All these developments will provide measurement assurance which is an essential part of digitalisation to ensure that sensor output is always ‘right’, as well as providing essential ‘points of truth’ in a sensor network. Some progress in digitalisation of calibrations to make them available to end-users via a website and/or an Application Programming Interface is also described.

Magnetic Cooling and Vibration Isolation of a Sub-kHz Mechanical Resonator

We report recent progress toward the realization of a sub-mK, low-vibration environment at the bottom stage of a dry dilution refrigerator for use in mechanical tests of quantum mechanics. Using adiabatic nuclear demagnetization, we have cooled a silicon cantilever force sensor to Tapprox 1 mK. The temperature of the tip holder of the cantilever chip was determined via a primary magnetic flux noise thermometer. The quality factor of the cantilever continues to increase with decreasing temperature, reaching Qapprox 4cdot 10^4 at 2 mK. To demonstrate that the vibration isolation is not compromised, we report the detection of the thermal motion of the cantilever down to T approx 20 mK, only limited by the coupling to the SQUID readout circuit. We discuss feasible improvements that will allow us to probe unexplored regions of the parameter space of continuous spontaneous localization models.

Comb-assisted mercury spectroscopy in the deep-ultraviolet: towards the development of a new primary thermometer

We report on the development of a new primary thermometer based upon high-precision spectroscopy of mercury vapors in the deep-ultraviolet region for the practical realization of the new kelvin. The line profile of the (6s 2)1 S 0 → (6s6p)3 P 1 intercombination transition of the 200Hg bosonic isotope is observed with a high spectral fidelity using a coherent radiation source at 253.7 nm. This latter consists of a near-IR external cavity diode laser followed by a double-stage second-harmonic generation apparatus. Metrology grade UV spectroscopy is demonstrated by locking the diode laser to a self-referenced optical frequency comb synthesizer.

Exploring the intra-4f and the bright white light upconversion emissions of Gd2O3:Yb3+,Er3+-based materials for thermometry.

Upconversion broadband white light emission driven by low-power near-infrared (NIR) lasers has been reported for many materials, but the mechanisms and effects related to this phenomenon remain unclear. Herein, we investigate the origin of laser-induced continuous white light emission in synthesized nanoparticles (Gd0.89Yb0.10Er0.01)2O3 and a mechanical mixture of commercial oxides with the same composition 89% Gd2O3, 10% Yb2O3, and 1% Er2O3. We report their photophysical features with respect to sample compactness, laser irradiation (wavelength, power density, excitation cycles), pressure, temperature, and temporal dynamics. Despite the sensitizer (Yb3+) and activator (Er3+) being in different particles for the mechanical mixture, efficient discrete and continuous upconversion emissions were observed. Furthermore, the synthesized nanoparticles were developed as primary luminescent thermometers (upon excitation at NIR) in the 299-363 K range, using the Er3+ upconversion 2H11/2 → 4I15/2/4S3/2 → 4I15/2 intensity ratio. They were also operating as secondary ones in the 1949-3086 K, based on the blackbody distribution of the observed white light emission. Our findings provide important insights into the mechanisms and effects related to the transition from discrete to continuous upconversion emissions with potential applications in remote temperature sensing.

Luminescent Pb-free perovskites: low-cytotoxicity materials for primary thermal sensing

Novel luminescent In-based lead-free double halide perovskites co-doped with Yb3+/Er3+ have been synthesized. Their primary thermometer performance was assessed and their biological application to predict temperature was evaluated.

Upconverting nanoparticles as primary thermometers and power sensors

Luminescence thermometry is a spectroscopic technique for remote temperature detection based on the thermal dependence of the luminescence of phosphors, presenting numerous applications ranging from biosciences to engineering. In this work, we use the Er3+ emission of the NaGdF4/NaGdF4:Yb3+,Er3+/NaGdF4 upconverting nanoparticles upon 980 nm laser excitation to determine simultaneously the absolute temperature and the excitation power density. The Er3+2H11/2→4I15/2 and 4S3/2→4I15/2 emission bands, which are commonly used for thermometric purposes, overlap with the 2H9/2 →4I13/2 emission band, which can lead to erroneous temperature readout. Applying the concept of luminescent primary thermometry to resolve the overlapping Er3+ transitions, a dual nanosensor synchronously measuring the temperature and the delivered laser pump power is successfully realized holding promising applications in laser-supported thermal therapies.

Photophysical and Primary Self-Referencing Thermometric Properties of Europium Hydrogen-Bonded Triazine Frameworks.

Lanthanide hydrogen-bonded organic frameworks (LnHOFs) are recently emerging as a novel versatile class of multicomponent luminescent materials with promising potential applications in optics and photonics. Trivalent europium (Eu3+) incorporated polymeric hydrogen-bonded triazine frameworks (PHTF:Eu) have been successfully obtained via a facile and low-cost thermal pyrolysis route. The PHTF:Eu material shows a porous frame structure principally composed of isocyanuric acid and ammelide as a minor constituent. Intense red luminescence with high colour-purity from Eu3+ is obtained by exciting over a broad absorption band peaked at 300 nm either at room or low temperature. The triazine-based host works as excellent optical antenna towards Eu3+, yielding ~42% sensitization efficiency (ηsens) and an intrinsic quantum yield of Eu3+ emission (ΦEu) as high as ~46%. Temperature-dependent emission studies show that PHTF:Eu displays relatively high optical stability at elevated temperatures in comparison to traditional inorganic phosphors. The retrieved activation energy of 89 meV indicates that thermal quenching mechanisms are attributed to the intrinsic energy level structure of the metal-triazine assembly, possibly via a thermally activated back transfer to ligand triplet or CT states. Finally, by using an innovative approach based on excitation spectra, we demonstrate that PHTF:Eu can work as a universal primary self-referencing thermometer based on a single-emitting center with excellent relative sensitivity in the cryogenic temperature range.

Novel and High‐Sensitive Primary and Self‐Referencing Thermometers Based on the Excitation Spectra of Lanthanide Ions

AbstractRemote sensing through ratiometric luminescence thermometry based on trivalent lanthanide ions (Ln(III)) has lately become a promising technique due to its numerous applications. Most available Ln(III)‐based luminescent thermometers require a calibration process with a reference thermal probe (secondary thermometers) and recurrent calibrations are mandatory, particularly when the thermometers are used in different media. This is sometimes impractical and a medium‐independent calibration relation is postulated, which is potentially inaccurate. Thus, the determination of the temperature based on well‐grounded physical principles by primary thermometers is the only way to overcome these challenges. Despite being considered one of the most important developments in luminescence thermometry, primary luminescent thermometers are scarce. Primary thermometers requiring calibration are proposed, implemented, and validated at one known temperature (primary‐T), which are also self‐referencing, employing ratiometric data from the excitation spectrum of Ln(III). By combining with the emission spectrum, thermometers not requiring calibration (primary‐S) are devised. An Eu(III)‐β‐diketonate complex is used as a proof‐of‐concept, but the approach is universal and other Ln(III)‐based materials can be explored. Because many thermometric parameters are employed for temperature prediction an unprecedented very high accuracy of 0.2% in the physiological range is obtained.

Excitation power density dependence of a primary luminescent thermometer based on Er3+, Yb3+: GdVO4 microcrystals operating in the visible

A discussion about the calibration of the Er3+,Yb3+:GdVO4 microcrystals as a luminescent primary thermometer based on the known equation of state of Boltzmann distribution of the electronic population of the two Erbium emitting coupled levels has been given. Its validity has been demonstrated. Besides, when Er3+,Yb3+:GdVO4 microcrystals acting as secondary thermometer, it has been proven the dependence of the thermometric ratio based on the integrated intensities of the green visible emissions arising from the two thermally coupled levels of erbium, 2H11/2 and 4S3/2, on the excitation power density for the Er3+,Yb3+:GdVO4 microcrystals. The effect of the excitation power density on the relative thermal sensitivity and temperature resolution has been also analyzed.

Luminescent thermometry based on Er3+/Yb3+ co-doped yttrium niobate with high NIR emission and NIR-to-visible upconversion quantum yields

The growing demand aiming non-invasive diagnosis techniques applications has become an emerging field for developing more efficient bioprobes working in the near infrared (NIR) biological windows. In this work, we propose Er3+/Yb3+ co-doped yttrium niobate as a multifunctional material synthesized via sol-gel method. We study its NIR emission under UV excitation (down-shifting) and NIR-to-visible upconversion (UC) emission and exploit this material as a luminescent thermometer. X-ray diffraction analysis points out the formation of cubic Y3NbO7 crystalline phase after annealing at 1100 °C. Intense and narrow 1.5 μm emission (FWHM ∼24 nm) with Er3+4I13/2 lifetime value of ca. 5.5 ms are observed under excitation in the host absorption band (276 nm), due to down-shifting process. Down-shifting and upconversion quantum yields (QY) with excitation at 980 nm were reported for the first time for Y3NbO7 material with values of ca. 18% and ca. 0.0020% in the NIR and visible ranges, respectively. Y3NbO7 is a luminescent primary thermometer with maximum relative thermal sensitivity of 1.31 ± 0.06% K−1, temperature uncertainty of 0.31 K, and repeatability of 99.6%. Furthermore, the relatively high QY values in NIR and UC emission, comparable to fluorides and higher than other oxides, make Er3+/Yb3+ co-doped yttrium niobate an interesting multifunctional probe aiming for biological applications.

Insights from 20 years of temperature parallel measurements in Mauritius around the turn of the 20th century

Abstract. There is considerable import in creating more complete, better understood holdings of early meteorological data. Such data permit an improved understanding of climate variability and long-term changes. Early records are particularly incomplete in the tropics, with implications for estimates of global and regional temperature. There is also a relatively low level of scientific understanding of how these early measurements were made and, as a result, of their homogeneity and comparability to more modern techniques and measurements. Herein we describe and analyse a newly rescued set of long-term, up to six-way parallel measurements undertaken over 1884–1903 in Mauritius, an island situated in the southern Indian Ocean. Data include (i) measurements from a well-ventilated room, (ii) a shaded thermograph, (iii) instruments housed in a manner broadly equivalent to a modern Stevenson screen, (iv) a set of measurements by a hygrometer mounted in a Stevenson screen, and for a much shorter period (v) two additional Stevenson screen configurations. All measurements were undertaken within an ∼ 80 m radius of each other. To our knowledge this is the first such multidecadal multi-instrument assessment of meteorological instrument transition impacts ever undertaken, providing potentially unique insights. The intercomparison also considers the impact of different ways of deriving daily and monthly averages. The long-term comparison is sufficient to robustly characterize systematic offsets between all the instruments and seasonally varying impacts. Differences between all techniques range from tenths of a degree Celsius to more than 1 ∘C and are considerably larger for maximum and minimum temperatures than for means or averages. Systematic differences of several tenths of a degree Celsius also exist for the different ways of deriving average and mean temperatures. All differences, except two average temperature series pairs, are significant at the 0.01 level using a paired t test. Given that all thermometers were regularly calibrated against a primary Kew standard thermometer maintained by the observatory, this analysis highlights significant impacts of instrument exposure, housing, siting, and measurement practices in early meteorological records. These results reaffirm the importance of thoroughly assessing the homogeneity of early meteorological records.

Primary thermometers based on sol–gel upconverting Er3+/Yb3+ co-doped yttrium tantalates with high upconversion quantum yield and emission color tunability

Primary thermometers based on sol–gel upconverting Er3+/Yb3+ co-doped yttrium tantalates with high upconversion quantum yield and emission color tunability

In vitro assays and nanothermometry studies of infrared-to-visible upconversion of nanocrystalline Er3+,Yb3+ co-doped Y2O3 nanoparticles for theranostic applications

Luminescent spherical, redispersable, and monodisperse Er3+,Yb3+ co-doped Y2O3 nanoparticles were synthesized by homogenous precipitation followed by thermal annealing. Cubic Y2O3 nanoparticles exhibited high colloidal stability in water and biological medium and 90% cell viability toward glioblastoma multiforme cell lines. Confocal microscopy revealed cellular internalization of Y2O3 nanoparticles. Upon excitation at 980 nm, efficient near-infrared to visible upconversion luminescence from Y2O3:Er3+,Yb3+ nanoparticles occurred. The upconversion dynamics was determined by the number of photons, which evidenced that energy transfer by the upconversion mechanism is predominated. On the basis of luminescence nanothermometry studies, the nanoparticles exhibited features of a primary thermometer with high thermal sensitivity (1.27 ± 0.05% K−1 (303 K) and large repeatability (>97%), attesting that it can be used as a contactless optical thermal sensor. This primary thermometer is also successfully applied in a cell culture medium showing that the nanoparticles can operate on biological media. This opens the possibility of the use of Y2O3:Er3+,Yb3+ nanoparticles in the design of a theranostic platform, able to simultaneously monitor temperature and, coupled to photosensitizers, produce reactive oxygen species for cancer therapy.

Primary Luminescent Nanothermometers for Temperature Measurements Reliability Assessment

The potential applications in disparate fields led to a rapid evolution of luminescence thermometry. In particular, luminescent thermometry based on trivalent lanthanide ions (Ln3+) has become very popular in the past decade due to the unique versatility, stability, and narrow emission band profiles covering a broad spectral range (from ultraviolet to the infrared) with relatively high emission quantum yields. Nevertheless, the reliability of Ln3+ ratiometric nanothermometry measurements is recently questioned in a few works reporting fake temperature readouts caused by experimental artifacts and even intrinsic effects. Using NaYF4:Er3+/Yb3+@NaNdF4@PAA (PAA stands for polyacrylic acid) core–shell nanoparticles, it is shown that how the primary luminescent thermometer concept can be used to correct the thermometric parameter (the intensity ratio of the Er3+ 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions) from the interference of the intruding 2H9/2 → 4I13/2 emission ensuring, thereafter, reliable temperature measurements.

Magnon-Phonon Quantum Correlation Thermometry

A large fraction of quantum science and technology requires low-temperature environments such as those afforded by dilution refrigerators. In these cryogenic environments, accurate thermometry can be difficult to implement, expensive, and often requires calibration to an external reference. Here, we theoretically propose a primary thermometer based on measurement of a hybrid system consisting of phonons coupled via a magnetostrictive interaction to magnons. Thermometry is based on a cross-correlation measurement in which the spectrum of back-action driven motion is used to scale the thermomechanical motion, providing a direct measurement of the phonon temperature independent of experimental parameters. Combined with a simple low-temperature compatible microwave cavity read-out, this primary thermometer is expected to become a popular thermometer for experiments below 1 K.