Excellent Temperature Resolution Research Articles

High sensitivity temperature sensing material In2Li3P3O12: Bi3+, Eu3+ based on effective energy transfer from Bi3+ to Eu3+

In recent years, fluorescent temperature sensing materials have been widely studied because they can realize remote non-destructive temperature measurement. High temperature sensitivity and excellent temperature resolution are the eternal pursuit of fluorescence temperature sensing. Here, we report the preparation, structure, luminescent properties and temperature sensing performance of phosphor In2Li3P3O12: Bi3+, Eu3+. Eu3+ singly doped samples can emit red light under 270 nm excitation. There is effective energy transfer from Bi3+ to Eu3+ in the Bi3+ and Eu3+ co-doped samples. Doping Bi3+ on the basis of doping Eu3+ can significantly enhance the luminescence intensity of Eu3+ ions. Ultraviolet light from Bi3+ and red light from Eu3+ are chosen to design a fluorescence intensity ratio thermometer for more accurate temperature detection. The temperature sensing technology has a maximum absolute and relative sensitivity is up to 0.0087 K−1 at 298 K−1 and 2.71 % K−1 at 325 K, respectively. This has a higher sensitivity than many phosphors available on the market. This indicates that it is a kind of fluorescence temperature sensing material with great potential.

Energy transfer in Bi3+-Sm3+ co-doped phosphors for temperature sensing and imaging

Optical thermometry has the distinct superiority of non-invasive, non-contact, and high spatial resolution. However, the simultaneous improvement of temperature sensitivity and resolution remains challenging. Herein, the tunable emission colors can be realized via energy transfer in Bi3+-Sm3+ co-doped La3Ta0.8Sb0.2O7, which further applied for fluorescence temperature sensing and imaging. With the partial substitution of Sb5+ with Ta5+, the emission peak of La3SbO7:0.04Bi3+ shiftes from 530 nm to 460 nm, together with a 2.1-fold enhancement of emission intensity. The emission shifted from bright blue to purple under 365 nm excitation based on the energy transfer. The energy transfer efficiency from Bi3+ to Sm3+ can reach 41.6 % via dipole–dipole interaction. The La3Ta0.8Sb0.2O7:(0.04Bi3+,0.005Sm3+) phosphors exhibit maximum relative sensitivity (Sr) of 1.32 %K−1 (@498 K) and absolute sensitivity (Sa) of 0.059 K−1 (@417 K), which have excellent temperature resolution and repeatability. Thus, the energy transfer in co-coped phosphors can simultaneously improve the temperature sensitivity and resolution for fluorescence temperature sensing. Besides, the phosphor/PDMS films can exhibit obvious thermochromic imaging.

The implementation of an easy-to-apply NMR cryoporometric instrument for porous materials

Time-domain NMR has been extensively utilised to study various characteristics of fluid-saturated porous,materials for instance their mobility, dynamics, stiffness, viscosity and rigidity features, particularly for solid hydrocarbons, rubbers and other polymers. As a unique time-domain technique available for over 30 years, NMR cryoporometry (NMRC) may be used to obtain pore-size distributions of the measured samples. To accurately control the sample temperature, a Peltier thermo-electrically cooled variable temperature probe has been developed and integrated with a highly compact precision NMR time-domain relaxation spectrometer, therefore providing the community with a high-performance instrument for NMR Cryoporometry. To extend the application of aforementioned high-performance NMRC instrument into more senarios, we designed a series of light-weight, compact and integral models with optional NMR frequencies from 12 MHz up to 23 MHz. The measured sample temperature can be precisely controlled from about −60 °C to +80 °C, with an excellent temperature resolution of 10 mK or better near the probe liquid bulk melting point. Therefore, it offers a fairly wide NMRC pore-size distribution ranging from about 1 nm to 2 μm by using water as the probe liquid in the pores, significantly wider than is possible when applying generic NMR Spectrometers for NMRC. A preliminary example of NMR Cryoporometric measurements on two special cement samples is shown in the paper in which the measured pore scales as well as their repeatability are demonstrated. Furthermore, various nano-materials, such as MOF, zeolite and shale kerogen would be potential materials to study by using these new available NMRC instrument models. We aim to offer this technique as a quantitative and easy-to-apply unitary benck-top tool for an even wider range of porous material.

Boltzmann vs. non-Boltzmann (non-linear) thermometry - Yb3+-Er3+ activated dual-mode thermometer and phase transition sensor via second harmonic generation

Second harmonic generation (SHG) and upconversion luminescence (UCL), as second-order nonlinear optical (NLO) effects, are crucial in modern optics and optoelectronics. Here, through the chemical engineering process we obtained a series of optically active BaTiO3: Er3+, Yb3+ perovskite materials, exhibiting temperature-dependent NLO responses. Upon 976 nm laser light irradiation, the micron-sized, polycrystalline samples show simultaneously intense UCL and SHG effects. Comparison of the thermometric features based on luminescence thermometry, i.e., band intensity ratio based on thermally-coupled levels of Er3+, and NLO thermometry, i.e., SHG/UCL intensity ratio, shows that the superior thermal sensitivity (≈ 4%/K, at ~400 K) and excellent temperature resolution (δT = 0.07 K) is achieved for the NLO thermometry approach. Furthermore, the combination of NLO spectroscopy with UCL allows rapid, more precise and clear phase transition detection (from tetragonal to cubic phase at around 386 K), compared to conventional structural methods, such as X-ray diffraction and Raman spectroscopy. Our work suggests that some non-Boltzmann, non-linear thermometers can provide much more effective temperature readouts (compared to the commonly studied Boltzmann thermometers), simultaneously working as accurate, rapid and non-invasive phase transition sensors.

Supersensitive Sm2+‐Activated Al2O3 Thermometric Coatings for High‐Resolution Multiple Temperature Read‐Outs from Luminescence

AbstractThe introduction of additional functionalities to materials is exceptionally important as it opens new applications for them. Aluminum, one of the most abundant and important materials, is coated with luminescent Sm2+‐doped γ‐aluminium oxide to impart thermometric functionality. Considering the potential industrial applications, two of the most widely used aluminum alloys, 6061 and 7075, are also coated. For this purpose, plasma electrolytic oxidation (PEO), an effective technique for producing hard ceramic coatings on various metal surfaces, is used. It is shown that thermometric coatings can be produced on aluminum in one‐step process by adding the raw precursor to the electrolyte. The valence reduction of Ln3+ to Ln2+ is achieved during the PEO process. The intense and broad (orange to deep red) emission from the coating shows supersensitivity to temperature changes over the 100–648 K range. The temperature is obtained from the coating emission using i) the emission intensity ratio method, ii) emission lifetime, and iii) emission band position with sensitivities of 4.8% K−1, 1.2% K−1, and 8 cm−1 K−1, respectively. Several applications would benefit from the thermometric coating's excellent temperature resolution of 0.04 K and the choice of three temperature read‐outs that facilitate the coating's use in different luminescence thermometry setups.

Improving temperature resolution of luminescent nanothermometers working in the near-infrared range using non-thermally coupled levels of Yb3+ & Tm3+

Up-converting nanothermometer YF3: 20% Yb3+, 0.5% Tm3+ was obtained via hydrothermal synthesis and a subsequent post-synthesis thermal treatment. The nanomaterial formed a stable colloid and showed (under 975 nm excitation) blue upconversion luminescence visible to the naked eye. The emission spectrum consisted of five thulium ion bands (450–870 nm) and one ytterbium ion band (above ~900 nm). The determined band intensity ratios of the non-thermally coupled levels (non-TCLs), i.e. emission bands of Tm3+ and Yb3+ observed in the visible − NIR ranges, monotonously change with temperature. Using linear fits, the determined band intensity ratios were correlated with temperature, and the relative temperature sensitivities and temperature resolutions were calculated for four of them, associated with the non-TCLs of Yb3+ and Tm3+. Utilizing the 2F5/2 → 2F7/2/3H4 → 3H6 band intensity ratio of Yb3+/Tm3+ (940/800 nm), located within the NIR spectral range of the first biological window, and exhibiting very high signal intensity, the developed nanothermometer has a decent relative sensitivity (Sr ≈ 1% K−1) and excellent temperature resolution (δT ≈ 0.2 K) at 313 K. The obtained material can be used to construct new nanothermometers, useful both in biological experiments and in industrial research.

Photoluminescence and ratiometric fluorescence temperature sensing abilities of zincate phosphors

Nowadays, the fluorescent materials applying to the temperature sensing field are mostly based on the rare-earth ions, scarcely non-rare-earth co-doped optical thermometers have been invested, let alone the phosphors with dual transition metal ions. Herein, we advocate a novel rare-earth free activated fluorescent material co-doped with dual transition metal ions and adopt the fluorescence intensity ratio-based strategy to measure the temperature. Firstly, this kind of optical material possesses the feasibility to be mass-produced for its intrinsic merits of economic rationality and nontoxicity. Besides, benefitting from the different thermal properties of sensitizer and activator ions, this material is supposed to be an excellent material for temperature sensing. It turns out that this Ti4+,Mn4+ coactivated optical material possesses an excellent temperature measuring performance with the optimal absolute sensitivity as high as 3.79% K−1. What is more, the prominent signal discriminability and accurate temperature detection ability could be enabled deriving from two well-separated emission bands and excellent temperature resolution. Furthermore, the photoluminescence properties, the crystalline structure, the crystal field strength, and the viability of the Chromaticity Coordinates-based method to measure temperature are manifested in this paper as well. Overall, it is anticipated that this novel coactivated optical material with binary luminescent centers could be a promising candidate for temperature sensing, and this preliminary study would invoke researchers’ passion for exploring more dual activators-based optical thermometric materials in the absence of rare-earth ions.

Room temperature picowatt-resolution calorimetry

Picowatt-resolution calorimetry is necessary for fundamental studies of nanoscale energy transport. Here, we report a microfabricated device capable of <4 pW resolution—an order of magnitude improvement over state-of-the-art room temperature calorimeters. This is achieved by the incorporation of two important features. First, the active area of the device is thermally isolated by thin and long beams with a total thermal conductance (G) of ∼600 nW/K. Further, a bimaterial cantilever thermometer capable of a temperature resolution (ΔTres) of ∼4 μK is integrated into the microdevice. The small thermal conductance and excellent temperature resolution enable measurements of heat currents (q = G × ΔTres) with a resolution <4 pW.

An ac susceptometer for the characterization of large, bulk superconducting samples

The main purpose of this work was to design, develop and construct a simple, low-cost ac susceptometer to measure large, bulk superconducting samples (up to 32 mm in diameter) in the temperature range 78–120 K. The design incorporates a double heating system that enables a high heating rate (25 K h−1) while maintaining a small temperature gradient (<0.2 K) across the sample. The apparatus can be calibrated precisely using a copper coil connected in series with the primary coil. The system has been used successfully to measure the temperature dependence of the ac magnetic properties of entire RE–Ba–Cu–O [(RE)BCO] bulk superconducting domains. A typical ac susceptibility measurement run from 78 K to 95 K takes about 2 h, with excellent temperature resolution (temperature step ∼ 4 mK) around the critical temperature, in particular.