Temperature Probe Research Articles

Low threshold photon avalanche upconversion emission for temperature sensing based on Yb(III)/Er(III) Co-doped NdVO4 with sphere 3D self-assembled structure microparticles

Upconversion luminescent microcrystals (UCMs) due to their optical characteristics have been applicated in temperature detecting fields. However, the accuracy of traditional temperature probes based on UCMs is limited by the low intensity of upconversion luminescence (UCL). Herein, Yb3+ and Er3+ ions co-doped NdVO4 (NdVO4:Yb/Er) UCMs with a 3D self-assembled structure were designed via a hydrothermal method. This innovative structure enables the realization of a photon avalanche (PA) emission process. The Yb3+ and Er3+ co-doping in NdVO4:Yb/Er UCMs significantly reduces the PA threshold compared to NdVO4:Er UCMs. Obvious PA process produced by Yb3+/Er3+ doping is observed at low excitation threshold (～13 mW) in NdVO4:Yb/Er UCMs, enhancing the whole UCL intensity. Additionally, the NdVO4:Yb/Er UCMs exhibit a high temperature sensitivity of 3.5% K−1 at low pump power, indicating that UCMs have the potential application in optical temperature sensor.

Temperature sensing of the brain enabled by directly inscribed Bragg gratings in CYTOP polymer optical fiber implants

Brain temperature is a vital physiological parameter that has a great effect on metabolic processes, enzymatic activity, neurotransmitter function, blood flow regulation, neuroprotection, and cognitive performance. In this framework, the development of accurate and reliable brain temperature measurement tools is crucial in brain-related treatment and research, such as neurosurgery, therapeutic hypothermia, and the understanding of brain function and pathologies. Here, we developed the first large-core flexible low optical loss CYTOP polymer optical fiber (POF)-based brain temperature probe operating in the telecommunication spectral range. The temperature measurements were achieved by detecting the reflected spectrum from a fiber Bragg grating (FBG) directly inscribed at the tip of the POF using femtosecond pulses. A fluorinated ethylene propylene (FEP) tube was thermally drawn and used as a sleeve around the FBG structure to eliminate the cross-sensitivity with humidity and microstrain perturbations. The assembled POF implant has a sensitivity of 14.3 pm/°C. The local temperature of the cerebral cortex, corpus callosum, and striatum in a rat brain was measured in vivo. The results indicate that the deep brain regions have higher temperature than the top cortical ones with a relatively linear relationship between the brain structure depth and its temperature. In addition, the rectal body core temperature was detected in parallel with the brain temperature measurement to further validate the developed device. We believe that the presented CYTOP POF-based implantable temperature probe opens the way towards the development of flexible and stable tools for accurate brain temperature recording where large-core fiber-based neural devices are required.

Simulations of laminar methane flames doped with iron nitrate/1-butanol aerosol in a novel matrix burner

A novel matrix burner enabled the investigation of aerosol-doped laminar low-pressure flames. Iron nitrate dissolved in 1-butanol was used as a typical model system, also found in the flame spray pyrolysis for synthesis of iron oxide. The state of the aerosol entering the flame front was quantified by single-droplet evaporation calculations. Three-dimensional simulations were conducted to quantify thermal losses and the impact of buoyancy on the deviation from an ideal one-dimensional approximation. Highly resolved simulations of the burner matrix confirmed the compact, external mixing zone and the flatness of the flame in the low-pressure operation. Simulations based on the one-dimensional approximation demonstrated the suitability of the experimental setup for reaction kinetics investigations. The results were compared and validated by temperature measurements and probing mass spectrometry. Based on investigations of the particle-producing flame, a hypothesis about the origin of gas-borne nanoparticles in the spray-flame synthesis process was derived. This work demonstrates the suitability of the novel matrix burner for the investigation of reaction kinetics in aerosol doped, quasi-premixed, flat flames using one-dimensional, laminar flame simulations.

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.

Fabrication and Evaluation of YBa2Cu3O7-δ Probe for Scanning Probe Microscopy

We proposed, fabricated, and evaluated a high-temperature superconducting probe made of YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-δ</sub> (YBCO) for scanning probe microscopy. A c-axis-oriented bulk was cut into a rectangular solid rod (0.5 × 0.5 × 10 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) using a fine cutter machine. The transition temperature of the rod was approximately 90 K, which was almost the same as that of the original bulk, indicating no critical damage to the superconductivity owing to the cutting process. One end of the rod was polished to a pyramid shape with <100-μm radius of curvature, and the apex was further sharpened to ∼1 μm using a focused Ga ion beam. The penetration depth of Ga ions from the YBCO surface was much less than 1 μm at an acceleration voltage of 40 kV, suggesting that the chemical composition was conserved inside the rod. An YBCO probe was installed in an atomic force microscope (AFM), where the probe temperature was set at 300 K at the time. Depending on the tip radius, a clear AFM image was obtained by gluing the probe to a quartz-tuning fork.

Developing a special microwave oven: Assessment of its performance for dough fermentation and nutrient soup elaboration

Bread and soup are two of the most important foods in daily life, thus dough fermentation and nutrient soup elaboration are more and more popular, but there is a lack of relevant low-cost and high-reliable household appliances on the market. Therefore, this paper proposes automatic control methods for dough fermentation and nutrient soup elaboration based on a special microwave oven. Fermentation theory, run-up microwave fermentation principle, microwave extraction principle, NTC temperature probe design and scalable fuzzy control algorithm are described in detail. Besides, the experimental platform is set up with a temperature chamber, an optical fiber thermometer and a power meter. Experimental results demonstrate that the relationship between the heating time and flour's mass is linear. For different ambient temperature tests, the volume ratios of the fermented dough to unfermented dough of different cases range from 2.2 to 2.62, and the inside of the dough after fermentation is fluffy, with small and dense cavities. Meanwhile, there is no acid taste and skin dryness, and the power consumption of microwave fermentation is less than half of that induced by grill, convection or steam fermentation. The detection error of the NTC temperature probe with microwave shielded is 0.48 °C, and the control error of the closed loop system is less than 0.5 °C. The temperature-rise slope of water is lower than that of ingredient, and the water's temperature is about 1 °C less than that of the ingredient. The soup after microwave elaboration is amber and clear, the ingredients are intact, the water loss is less than 50 g, and the total power consumption is 684 Wh. In short, microwave-based control methods for dough fermentation and nutrient soup elaboration are effective.

Thermal Profiles for Focal Pulsed Electric Field Ablation

BackgroundPulsed electrical field (PEF) ablation may cause tissue heating. These changes are reportedly small, but each PEF system and waveform will have a different behavior, and data are lacking. ObjectivesThis study sought to compare the temperature profile of focal point, monopolar biphasic PEF ablation versus radiofrequency (RF). MethodsAblation lesions were performed on perfused thigh muscle of swine. PEF lesions were performed with 3 compatible ablation catheters at the highest (25 amp) energy, and 1 catheter (Tacticath SE) was also used at the 22- and 19-amp levels. Temperature changes in the tissue were measured using fluoroptic temperature probes inserted at the muscle surface, as well as 3 mm and 7 mm below the surface. Temperatures were recorded continuously at baseline, during delivery, and after ablation. Muscle temperatures were compared with those of RF lesions performed with 1 catheter (Tacticath SE) at 30 W for 30 seconds. ResultsPEF ablation with 3energy settings produced small temperature changes. Maximum average temperature rise for PEF for the maximum (25-amp) energy setting (32 lesions) was 7.6 °C, 2.8 °C, and 0.9 °C at the surface, 3-mm depth, and 7-mm depth, respectively. The temperature rise was dose dependent, with lower energy settings yielding less temperature rise. RF ablations (10 lesions) produced temperature increases of 16.6 °C, 39.8 °C, and 9.5 °C at the surface, 3-mm depth, and 7-mm depth, respectively. ConclusionsPEF caused detectable temperature changes in muscle tissue, which never exceeded 2.8 °C at the 3-mm depth versus baseline. By contrast, RF produced substantial temperature rises. These data support that focal monopolar biphasic energy delivered by this PEF technology retains a favorable thermal safety profile.

Gold nanoparticles engineered nanoporous membrane with sandwich structure for sensitive electrochemical quantification of exosome

Exosome has been identified as an excellent potential biomarker for tumor diagnosis. Herein, electrochemical aptasensor for exosome detection was developed via a sandwich-structured nanoporous membrane which was fabricated by assembling multilayer gold nanoparticles (mulAu) and monolayer gold nanoparticles (monAu) on the opposite side of a nanoporous alumina membrane (NAM). The tumor-derived exosomes can be efficiently captured by the specific probes confined on the monAu side of the membrane. And the mulAu side that was tightly attached with a Si wafer allowed the electrochemical exosome detection by monitoring the amperometric signal of ferricyanide that transported across the nanochannel array of the membrane. After optimization of pore diameter of the NAM, base sequence of the capture probe and incubation temperature as well as incubation time for exosomes, this NAM-based electrochemical aptasensor was applied to the quantification of the MCF-7 cells-derived exosomes. The steady state current displayed linearity relationship with the concentration of the exosomes in a broad range of 103 to 107 particles μL−1, along with a detection limit of 2.8 × 102 particles μL−1. By changing capture probe, this sandwich-structured membrane could be further extended to label-free, sensitive and rapid quantification of other tumor-associated vesicles.

Contributions towards variable temperature shielding for compact NMR instruments.

The application of compact NMR instruments to hot flowing samples or exothermically reacting mixtures is limited by the temperature sensitivity of permanent magnets. Typically, such temperature effects directly influence the achievable magnetic field homogeneity and hence measurement quality. The internal-temperature control loop of the magnet and instruments is not designed for such temperature compensation. Passive insulation is restricted by the small dimensions within the magnet borehole. Here, we present a design approach for active heat shielding with the aim of variable temperature control of NMR samples for benchtop NMR instruments using a compressed airstream which is variable in flow and temperature. Based on the system identification and surface temperature measurements through thermography, a model predictive control was set up to minimise any disturbance effect on the permanent magnet from the probe or sample temperature. This methodology will facilitate the application of variable-temperature shielding and, therefore, extend the application of compact NMR instruments to flowing sample temperatures that differ from the magnet temperature.

Noninvasive and Continuous Monitoring of the Core Body Temperature through the Quantitative Measurement of Blood Perfusion Rate.

Core body temperature (CBT) is one of the four vital signs that must be monitored continuously. The continuous recording of CBT is possible through invasive methods by inserting a temperature probe into specific body sites. We report a novel method to monitor CBT through the quantitative measurement of skin blood perfusion rate (ωb,skin). By monitoring the skin temperature, heat flux, and ωb,skin, the arterial blood temperature, equivalent to CBT, can be extracted. ωb,skin is quantitatively evaluated thermally via sinusoidal heating with regulated thermal penetration depth so that the blood perfusion rate is acquired only in the skin. Its quantification is significant because it indicates various physiological events including hyper- or hypothermia, tissue death, and delineation of tumors. A subject showed promising results with steady values of ωb,skin and CBT of 5.2 ± 1.05 × 10-4 s-1 and 36.51 ± 0.23 °C, respectively. For periods where the subject's actual CBT (axillary temperature) did not fall within the estimated range, the average deviation from the actual CBT was only 0.07 °C. This study aims to develop a competent methodology capable of continuously monitoring the CBT and blood perfusion rate at a distant location from the core body region for the diagnosis of a patient's health condition with wearable devices.

MONITORING PERFUSION-BASED CONVECTION IN CANCER TUMOR TISSUE UNDERGOING NANOPARTICLE HEATING BY ANALYZING TEMPERATURE RESPONSES TO TRANSIENT PULSED HEATING.

The dynamic nature of perfusion in living tissues, such as solid tumors during thermal therapy, produces challenging spatiotemporal thermal boundary conditions. Changes in perfusion can manifest as changes in convective heat transfer that influence temperature changes during cyclic heating. Herein, we propose a method to actively monitor changes in local convection (perfusion) in vivo by using a transient thermal pulsing analysis. Syngeneic 4T1 tumor cells were injected subcutaneously into BALB/c mice and followed by caliper measurements. When tumor volumes measured 150-400 mm3, mice were randomly divided into one of two groups to receive intratumor injections of one of two iron oxide nanoparticle formulations for pulsed heating with an alternating magnetic field (AMF). The nanoparticles differed in both heating characteristics and coating. Intratumor temperature near the injection site as well as rectal temperature were measured with an optic fiber temperature probe. Following heating, mice were euthanized and tumors harvested and prepared for histological evaluation of nanoparticle distribution. To ascertain the heat transfer coefficient from heating and cooling pulses, we fit a lumped capacitance, Box-Lucas model to the time-temperature data assuming fixed tumor geometry and constant experimental conditions. For the first particle set, the injected nanoparticles dispersed evenly throughout the tumor with minimal aggregation, and with minimal change in convection. On the other hand, heating with the second particle generated a measurable decline in convective performance and histology analysis showed substantial aggregation near the injection site. We consider it likely that though the second nanoparticle type produced less heating per unit mass, its tendency to aggregate led to more intense local heating and tissue damage. Further analysis and experimentation is warranted to establish quantitative correlations between measured temperature changes, perfusion, and tissue damage responses. Implementing this type of analysis may stimulate development of robust and adaptive temperature controllers for medical device applications.

Application of quantitative NMR in pharmaceutical analysis: Method qualification and potency determination for two new chemical entities in early-stage clinical studies

Quantitative NMR (qNMR), being a well-established analytical tool featuring efficiency, simplicity as well as versatility, has been extensively employed in pharmaceutical and medicinal testing. In this study, two 1H qNMR methods were developed to determine the %wt/wt potency of two new chemical entities (compound A and compound B) used in early clinical phase process chemistry and formulation development. The qNMR methods were demonstrated to be significantly more sustainable and efficient than the LC-based approach by substantially reducing the cost, hands-on-time, and materials consumed for testing. The qNMR methods were achieved on a 400 MHz NMR spectrometer equipped with 5 mm BBO S1 broad band room temperature probe. The methods with CDCl3 (for compound A) and DMSO-d6 (compound B) as solvent as well as commercially certified standards for quantitation were phase-appropriately qualified in terms of specificity, accuracy, repeatability/precision, linearity, and range. Both qNMR methods were demonstrated to be linear over the range of 0.8–1.2 mg/mL (80% to 120% of the nominal sample concentration of 1.0 mg/mL) with a correlation coefficient greater than 0.995. The methods were also demonstrated to be accurate with average recoveries ranging from 98.8% to 98.9% and 99.4–99.9% for compound A and compound B respectively as well as precise with %RSD of 0.46% and 0.33% for compound A and compound B respectively. The potency results of compound A and compound B determined by qNMR were compared with those determined by the conventional LC-based method and the qNMR results were demonstrated to be consistent with the LC-based method with absolute difference of 0.4% and 0.5% for compound A and B respectively.

Convergence criteria analysis for thermal conductance measurements of building walls: A case study

The significance of on-site measurements for the thermal characterization of building components is widely recognized. Walls thermal performance can be identified through the widely used Heat-Flow Meter (HFM) method, which has been frequently applied in literature. However, only a few scientific works have examined the convergence criteria suggested by the ISO 9869–1. Starting from this, the aim of this work is evaluating the convergence criteria in a case study using the progressive average method. Thermal conductance (C-value) measurements were carried out in a small-scale building, placed in the external area of a building school site near Rome (Italy). The building is internally equipped with an electric heating system. Heat-flux sensor and surface temperature probes were applied to assess the C-value of the envelope. The different switching-on of the heater characterized by different power levels and the reaching of regular thermal conditions after initial transients were considered to evaluate the acquired data and their influence on the results. The known walls stratigraphy allowed to compute and compare theoretical and experimental C-values. Based on the examined data, it is possible to assert that the convergence conditions are very strict, mainly due to the third criterion.

Can Oesophageal Temperature Probes Prevent Oesophageal Injury During Catheter Ablation of Atrial Fibrillation?

Can Oesophageal Temperature Probes Prevent Oesophageal Injury During Catheter Ablation of Atrial Fibrillation?

Achieving simultaneous sensing of oxygen and temperature with metalloporphyrins featuring efficient thermally activated delayed fluorescence and phosphorescence

Temperature is an essential parameter for reliable assessment of oxygen concentration by optical sensors. This can be done by a conventional sensor such as a resistance thermometer or by adding an optical temperature probe to the sensing material. A sensor that relies on a single emitter capable of simultaneous sensing of oxygen and temperature would be highly advantageous. Unfortunately, such materials are extremely rare and moreover poorly suitable for measurement at ambient temperatures and physiological conditions. To cover this gap, we systematically investigated 15 Pd(II) and 6 Pt(II) complexes of π-extended porphyrins that simultaneously emit thermally activated delayed fluorescence (TADF) and phosphorescence. The class of quinone-extended benzoporphyrins was found to feature especially high ratios of TADF to phosphorescence (1.4–2.7 and 0.10–0.21, for Pd(II) and Pt(II) complexes, respectively, at 25 °C) which represents approximately a sixteen-fold improvement compared to the benchmark octasulfone-substituted porphyrins. Interconversion of phosphorescence into TADF with increasing temperature enables ratiometric measurement of this parameter in the range from 0 to about 65 °C whereas the oxygen concentration is accessed through the decay time of either TADF or phosphorescence. Simultaneous sensing of both temperature and oxygen is demonstrated for a naphthoquinone-extended Pt(II) benzoporphyrin embedded in polystyrene that shows dual emission with maxima at 677 and 789 nm. The sensor is characterized for temperatures from 5° to 55 °C and oxygen partial pressure from 0 to 202 hPa, corresponding to the conditions found in the majority of applications. As an application example temperature compensated imaging of oxygen distribution is demonstrated.

Exercise-induced arterial hypoxemia in female masters athletes

The purpose of the study was to characterize exercise induced arterial hypoxemia (EIAH) in female masters athletes (FMA). We hypothesized that FMA would experience EIAH during treadmill running. Eight FMA (48–57 years) completed pulmonary function testing and an incremental exercise test until exhaustion (V̇O2max⁡ = 45.7 ± 6.5, range:35–54 ml/kg/min). On a separate day, the participants were instrumented with a radial arterial catheter and an esophageal temperature probe. Participants performed three to four constant load exercise tests at 60–70 %, 75 %, 90 %, 95 %, and 100 % of maximal oxygen uptake while sampling arterial blood and recording esophageal temperature. We found that FMA decrease their partial pressure of oxygen (86.0 ± 7.6, range:73–108 mmHg), arterial saturation (96.2 ± 1.2, range:93–98 %), and widen their alveolar to arterial oxygen difference (23.2 ± 8.8, range:5–42 mmHg) during all exercise intensities however, with variability in terms of severity and pattern. Our findings suggest that FMA experience EIAH however aerobic fitness appears unrelated to occurrence or severity (r = 0.13, p = 0.756).

Computational framework for polymer synthesis to study dielectric properties using polarizable reactive molecular dynamics

The increased energy and power density required in modern electronics poses a challenge for designing new dielectric polymer materials with high energy density while maintaining low loss at high applied electric fields. Recently, an advanced computational screening method coupled with hierarchical modelling has accelerated the identification of promising high energy density materials. It is well known that the dielectric response of polymeric materials is largely influenced by their phases and local heterogeneous structures as well as operational temperature. Such inputs are crucial to accelerate the design and discovery of potential polymer candidates. However, an efficient computational framework to probe temperature dependence of the dielectric properties of polymers, while incorporating effects controlled by their morphology is still lacking. In this paper, we propose a scalable computational framework based on reactive molecular dynamics with a valence-state aware polarizable charge model, which is capable of handling practically relevant polymer morphologies and simultaneously provide near-quantum accuracy in estimating dielectric properties of various polymer systems. We demonstrate the predictive power of our framework on high energy density polymer systems recently identified through rational experimental-theoretical co-design. Our scalable and automated framework may be used for high-throughput theoretical screenings of combinatorial large design space to identify next-generation high energy density polymer materials.

P-243 A commonly used temperature probe could result in setting heated surfaces within the IVF lab too high

Abstract Study question Which temperature probe (thermocouple Type T or Pt100) is the most accurate and robust for measuring medium temperatures in dishes on a heated surface? Summary answer A Pt100 probe attached to the bottom of the dish provides a more accurate and repeatable measurement than the commonly used thermocouple Type T probe. What is known already The success of an IVF cycle is dependent on several variables. Ensuring the gametes and embryos are exposed to appropriate temperatures is a critical variable during incubation and manipulation. There are different temperature measurement probes available for this purpose. Their specific properties could make them more, or less suitable for the various temperature measurements required in the laboratory. Study design, size, duration The aim of the study was to determine the best method (thermocouple Type T probe placed in the medium or a Pt100 sensor attached to the bottom of a dish) to measure temperature in medium held in two types of dish placed on a heated surface. Measurements were made in triplicate and standard deviation determined. Participants/materials, setting, methods The temperature of the medium in two types of dish (5 well and 40mm direct surface contact dishes, Vitrolife) were measured with two types of probes. The commonly used thermocouple Type T, which is composed of two wires, a copper and copper nickel alloy, that are welded together, and a resistance sensor composed of a small platinum plate attached to the bottom of the dish (Pt100). Main results and the role of chance With a 100 μl droplet under 5.0 ml of oil in a 40 mm dish (with the lid on) the tip of the Type T probe measured a temperature 3.2 ± 0.26 °C lower than the Pt100 probe. The Type T probe also measured a lower temperature in the 5 well dish. With a well containing 500 μl (lid on) it measured a temperature 2.1 ± 0.15 °C lower than the Pt100 probe. When the entire length of the Type T probe was placed inside of an incubator set at 37.0 °C the measured temperature was 0.1 °C lower than the Pt100 probe. This suggests the length of the Type T probe within the environment to be measured is critical, i.e., the lower temperatures obtained with the Type T probe when measuring medium temperature on heated surfaces depends on the method used rather than the probe itself. The reason for the lower temperature is correlated to the high temperature conductivity of the copper in the Type T probe. This also makes the measurement less repeatable as different factors (e.g., length of probe submerged, ambient temperature, air flow, etc.) will affect the reading. The Pt100 is not influenced by such factors. Limitations, reasons for caution The dishes used in this investigation create a uniform direct contact with the heated surface. This means that the heated surface will have a temperature close to that measured by the Pt100. This will not be the case with dishes with an air gap design. Wider implications of the findings This investigation highlights the importance of using the correct type of thermometer probe for the purpose. It is likely that when using a thermocouple Type T probe, temperature in the medium can be 2-3 °C higher than measured, which could impact gametes/embryos and lead to deleterious results. Trial registration number Not applicable

Temperature Distribution Assessment in Gas–Solid Reactive and Nonreactive Systems Heated by Microwaves

Research studies have shown that selective heating of different phases in gas–solid systems exposed to microwave (MW) irradiation leads to a temperature gradient between gas and MW absorber solids. This can suppress undesired secondary gas-phase reactions and yield apparent kinetic improvements and energy savings. However, the effects of reaction exothermicity/endothermicity, gas velocity, temperature probe location at the microscale, and MW penetration depth in fixed beds on the temperature difference between solid and gas phases exposed to MWs and temperature distribution in the fixed beds are poorly understood. Highlighting these effects was targeted in this study and accomplished with the help of multiphysics simulations by COMSOL Multiphysics (5.6). The corresponding COMSOL model was initially verified and validated by data collected from literature studies and those obtained experimentally by the authors in this study. Simulation results from the verified and validated model indicated that the temperature gradient between the gas and the MW absorber solid increases by increasing the gas velocity or switching from an endothermic reaction to no reaction and/or an exothermic reaction. In addition, the collected results show nonuniform temperature distribution in a fixed-bed reactor made of MW absorber particles irradiated by MWs due to the limited penetration depth of MWs and hotspot formation. This operational deficiency makes the large-scale design of this type of reactor very challenging for MW heating-assisted reactions.

Functionalized β-NaGdF4:YbIII luminescent nanothermometer based on the direct population of triplet states and NIR emission

Lanthanide (LnIII)-doped NaGdF4 nanoparticles functionalized with organic ligands have been investigated for cell imaging and luminescence thermometry for instance due to their versatility regarding radiation conversion, e.g, near-infrared (NIR)-to-NIR, NIR-to-visible, or UV-to-NIR. Yet, in the later case, the high energy of radiation into the human tissue is an issue, aiming cell imaging application. This drawback could be surpassed by shifting the absorption bands of the organic luminescent sensitizers attached on the particle to longer wavelengths, which can be achieved by singlet (S0) → triplet (Tn) transitions instead of the classic S0 → Sn processes. Herein, this possibility is discussed for hybrid systems based on spheroidal β-NaGdF4:YbIIII nanoparticles (average diameter of 7.8 nm) functionalized on the surface with 3,5-dibromobenzoate (3,5-bbza-) coordinated to LnIII ions. The Tn states of 3,5-bbza- are directly populated upon excitation at 368 nm or 430 nm, followed by energy transfer to YbIII that emits within the NIR spectral region. On the other hand, the ligand singlet states are populated at 300 nm. Taking advantage of the intensity ratio of the emission spectrum collected upon S0 → Tn (368 nm or 430 nm) or S0 → Sn (300 nm) excitation, luminescence thermometry was performed for the hybrid system, which displays maximum relative thermal sensitivity of 0.58% K−1 at 77 K. Therefore, the S0 → Tn transitions observed in the NaGdF4:YbIIII nanoparticles functionalized with 3,5-bbza- enable visible-shifted excitation bands and luminescence thermometry, which are interesting features aiming application in cell imaging and temperature probing, respectively.