In this study, ZnTe crystal was applied to provide precise thermal sensing for cryogenic temperatures. Multiple techniques, namely Raman and photoluminescence spectroscopies, were used to broaden the ...operating temperature range and improve the reliability of the proposed thermometers. Raman-based temperature sensing could be applied in the range of 20-100 K, while luminescence-based thermometry could be utilized in a narrower range of 20-70 K. However, the latter strategy provides better relative thermal sensitivity and temperature resolution. The best thermal performances based on a single temperature-dependent parameter attain
= 3.82% K
and Δ
= 0.12 K at
= 50 K. The synergy between multiple linear regression and multiparametric thermal sensing demonstrated for Raman-based thermometry results in a ten-fold improvement of
and a two-fold enhancement of Δ
. All studies performed testify that the ZnTe crystal is a promising multimode contactless optical sensor for cryogenic thermometry.
Accurate contactless thermometry is required in many rapidly developing modern applications such as biomedicine, micro- and nanoelectronics, and integrated optics. Ratiometric luminescence thermal ...sensing attracts a lot of attention due to its robustness toward systematic errors. Herein, a phonon-assisted upconversion in LuVO4:Nd3+/Yb3+ nanophosphors was successfully applied for temperature measurements within the 323–873 K range via the luminescence intensity ratio technique. Dual-activating samples were obtained by codoping and mixing single-doped nanopowders. The effect of the type of dispersion system and the Yb3+ doping concentration was studied in terms of thermometric performances. The relative thermal sensitivity reached a value of 2.6% K–1, while the best temperature resolution was 0.2 K. The presented findings show the way to enhance the thermometric characteristics of contactless optical sensors.
In the last decade much attention has been paid to the development of novel approaches in luminescence thermometry, which could allow contactless and noninvasive temperature sensing when traditional ...thermometers are useless. Typically, an optical thermometer exploits a distinct luminescence parameter to define temperature. However, the use of multimode sensors can significantly broaden the working range and improve the reliability of the temperature measurements. In this work, a Eu3+-doped LaVO4 sample was successfully utilized as a thermal sensor within a wide temperature range of 98–723 K based on monitoring various temperature-sensitive luminescence features. Different thermal sensing strategies were assessed and compared in terms of thermal sensitivity and temperature resolution. The best thermometric performances of the Eu3+-doped LaVO4 sensor reached an Sr = 1.49% K−1 and a ΔT = 0.6 K at room temperature. All the studies performed showed that the LaVO4:Eu3+ phosphor is a prospective multimode optical thermometer.
Novel strategies to obtain remote temperature sensing with good spatial and thermal resolution are in high demand in various applications, where traditional thermometers are inappropriate. The ...majority of developed luminescence thermometers utilize thermally-coupled levels with their inherent limitation of thermal sensitivity and problems with signal discriminability. We report mixed-valent Eu2+/Eu3+-doped MgAl2O4 phosphor as a ratiometric thermal sensor, which is free of these drawbacks. Different temperature behavior of Eu2+ and Eu3+ emission bands provides luminescence thermometry within range of 298–523 K. High absolute and relative thermal sensitivities of 0.084 K-1 and 0.83% K−1, respectively, as well as sub-degree temperature resolution indicate that MgAl2O4:Eu2+/Eu3+ phosphor is a promising material for optical thermometry.
The development of new contactless thermal nanosensors based on a ratiometric approach is of significant interest. To overcome the intrinsic limitations of thermally coupled levels, a dual activation ...strategy was applied. Dual activation was performed using co-doped single nanoparticles and a binary mixture of single-doped nanoparticles. Co-doped and mixed YVO4:Nd3+/Eu3+ nanoparticles were successfully demonstrated as luminescent nanothermometers and their thermometric performance, in terms of thermal sensitivity, temperature resolution and repeatability, was studied and compared.
A new series of luminescent heterometallic europium(III)–lutetium(III) terephthalate metal–organic frameworks, namely (EuxLu1−x)2bdc3·nH2O, was synthesized using a direct reaction in a water ...solution. At the Eu3+ concentration of 1–40 at %, the MOFs were formed as a binary mixture of the (EuxLu1−x)2bdc3 and (EuxLu1−x)2bdc3·4H2O crystalline phases, where the Ln2bdc3·4H2O crystalline phase was enriched by europium(III) ions. At an Eu3+ concentration of more than 40 at %, only one crystalline phase was formed: (EuxLu1−x)2bdc3·4H2O. All MOFs containing Eu3+ exhibited sensitization of bright Eu3+-centered luminescence upon the 280 nm excitation into a 1ππ* excited state of the terephthalate ion. The fine structure of the emission spectra of Eu3+ 5D0-7FJ (J = 0–4) significantly depended on the Eu3+ concentration. The luminescence quantum yield of Eu3+ was significantly larger for Eu-Lu terephthalates containing a low concentration of Eu3+ due to the absence of Eu-Eu energy migration and the presence of the Ln2bdc3 crystalline phase with a significantly smaller nonradiative decay rate compared to the Ln2bdc3·4H2O.
Ratiometric luminescence thermometers based on thermally coupled levels provide reliable temperature sensing with predictable calibration. However, requirement of thermal coupling of levels limits ...possible energy gap between them, and as, a result, leads to a fundamental limitation of relative thermal sensitivity. Development of luminescence thermometers with two active centers could overcome this drawback and obtain sensors with enhanced thermometric characteristics. Here, we suggested two types of dual-center Gd2O3:Tb3+/Eu3+ nanophosphors, namely co-doping and physical mixture, for ratiometric thermometry within temperature range of 123–473 K. Monitoring luminescence intensity ratio between Tb3+ and Eu3+ bands provides contactless sensing with moderate relative thermal sensitivities (0.53–0.77 % K−1) and sub-degree temperature resolution (0.3–0.6 K) at room temperature. All studied thermometers irrespective to dispersion system type and doping concentration display exceptional relative sensitivity exceeding the theoretical limit of sensors based on thermally-coupled levels at high temperatures. The largest sensitivity was determined to be 5.6 % K−1@473 K for mixed Gd2O3:Tb3+ 0.01 at. %+ Gd2O3:Eu3+ 0.2 at. % sample.
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•Co-doped and mixed Gd2O3:Tb3+/Eu3+ nanophosphors provide luminescence thermometry.•Ratiometric thermometry uses 5D4–7F5 (Tb3+) and 5D0–7F2/5D0–7F4 (Eu3+) transitions.•Higher energy transfer efficiency was obtained for co-doped samples compared with mixed ones.•The unprecedentedly high relative sensitivity of 5.6 % K−1@473K was achieved.•Suggested nanothermometers provide sub-degree thermal sensing resolution.
Remote thermal sensing has emerged as a temperature detection technique for tasks in which standard contact thermometers cannot be used due to environment or dimension limitations. One of such ...challenging tasks is the measurement of temperature in microelectronics. Here, optical thermometry using co-doped and mixed dual-center Gd
O
:Tb
/Eu
samples were realized. Ratiometric approach based on monitoring emission intensities of Tb
(
D
-
F
) and Eu
(
D
-
F
) transition provided sensing in the range of 30 °C-80 °C. Dispersion system type only slightly affected relative sensitivity, accuracy and precision. The applicability of phosphors synthesized to be utilized as remote optical thermometers for microelectronics has been proved with an example on a surface mount resistor and microcontroller.
In this work, three series of micro-sized heterometallic europium-containing terephthalate MOFs, (Eu1-xLnx)2bdc3·nH2O (Ln = La, Gd, Lu), are synthesized via an ultrasound-assisted method in an ...aqueous medium. La3+ and Gd3+-doped terephthalates are isostructural to Eu2bdc3·4H2O. Lu3+-doped compounds are isostructural to Eu2bdc3·4H2O with Lu contents lower than 95 at.%. The compounds that are isostructural to Lu2bdc3·2.5H2O are formed at higher Lu3+ concentrations for the (Eu1-xLux)2bdc3·nH2O series. All materials consist of micrometer-sized particles. The particle shape is determined by the crystalline phase. All the synthesized samples demonstrate an “antenna” effect: a bright-red emission corresponding to the 5D0-7FJ transitions of Eu3+ ions is observed upon 310 nm excitation into the singlet electronic excited state of terephthalate ions. The fine structure of the emission spectra is determined by the crystalline phase due to the different local symmetries of the Eu3+ ions in the different kinds of crystalline structures. The photoluminescence quantum yield and 5D0 excited state lifetime of Eu3+ are equal to 11 ± 2% and 0.44 ± 0.01 ms, respectively, for the Ln2bdc3·4H2O structures. For the (Eu1-xLux)2bdc3·2.5H2O compounds, significant increases in the photoluminescence quantum yield and 5D0 excited state lifetime of Eu3+ are observed, reaching 23% and 1.62 ms, respectively.
