Search

Passive temperature sensing systems based on the Internet of Things (IoT) present an efficient, reliable, and convenient solution for temperature monitoring with extensive application prospects and market value. This paper introduces a passive, battery-free, chipless, metasurface temperature sensing tag. The key insight is that the sensing tag uses vanadium dioxide () to solve the problems of measuring distance, large size, and high cost related to active devices. The sensing tag fabricated with tungsten-doped powder demonstrated a significant variation in the reflection magnitude within the temperature range of 34–42 °C. It was achieved through coating, sintering, metasurface design, and ion beam etching. Experimental results showed that the square resistance of the prepared coating decreased from 1003 to 90 as the temperature increased from 34 to 42 °C. Additionally, the reflection magnitude of the tag significantly increased with the temperature decrease in the 3.5–5.27 GHz frequency band. These results indicate that the passive temperature sensing tags can achieve rapid and accurate temperature sensing within the 34–42 °C range. [ABSTRACT FROM AUTHOR]

Hybrid nanogenerators are advanced mechanical energy harvesters capable of simultaneously scavenging multiple types of energy. Additionally, thermochromic materials provide a practical and visually assessable method for real‐time temperature monitoring. In this report, a novel energy harvester and sensing patch (EHSP) is introduced, that utilizes combined piezoelectric and triboelectric effects to harvest mechanical energy efficiently. To optimize the EHSP, various energy harvester configurations are fabricated and tested, and the dielectric properties of triboelectric films are systematically investigated. These improvements are implemented to augment the overall energy harvesting capability. The thermochromic properties of the EHSP are also explored to enhance both the electrical performance and thermal responsiveness. The EHSP demonstrates the ability to generate maximum voltage and current outputs of 350 V and 20.4 µA, respectively. Moreover, it can detect temperature changes within seconds, making it suitable for both energy harvesting and sensing applications. The EHSP is tested in practical scenarios, proving its efficiency as an energy harvester and sensor for everyday human activities. Furthermore, its integration with multiple hybrid nanogenerators showcases its potential for industrial and wearable sensing applications. [ABSTRACT FROM AUTHOR]

A series of Y 2 MoO 6 :0.01Er3+/0.09 Yb3+ upconversion phosphors doped with different concentrations of Li + ions (0.05, 0.10, 0.15, 0.20, 0.25, and 0.30 mol) were prepared by the high temperature solid phase reaction method, and their physical phase structures and upconversion luminescence were analyzed. At the excitation wavelength of 980 nm, the addition of Li+ sharply increased the upconversion luminescence intensity. With the increase of Li+ ion content, the luminescence intensity first increases and then decreases. When the doping amount reaches 0.25 mol, the luminescence intensity reaches the maximum, and the sample emits green light in the two-photon process. Y 2 MoO 6 :0.01Er3+/0.09 Yb3+/0.25Li + exhibits excellent temperature sensing properties. Its absolute sensitivity S a reaches up to 0.012 K-1, the relative sensitivity S r is 0.017 K-1 and the measurement error δ T is less than 0.3 K at room temperature. Its temperature sensing performance is far superior to similar materials. In addition, Judd-Ofelt theory calculations revealed that in comparison with Y 2 MoO 6 :0.01Er3+/0.09 Yb3+, its Ω 2 increased from 0.56 × 10−20 cm2 to 3.68 × 10−20 cm2, and the spectroscopic quality factor Ω 4 /Ω 6 ratio reached 4.09, which is much higher than that of the other fluorescent materials. The main reason is that Li + replaces the Y3+ ion lattice site, causing lattice distortion and reducing the lattice symmetry around the active ion. The increase in asymmetry increases the possibility of spontaneous radiative transitions. It is shown that the prepared upconversion luminescent materials have potential applications in the field of solid-state lasers and optical sensing. [ABSTRACT FROM AUTHOR]

Through conventional solid-state sintering process, PbNb2O6:Yb3+, Ln3+ (Ln3+=Er3+/Ho3+) ceramics have been fabricated. The structural information of synthesized ceramics was obtained via X-ray diffraction. Scanning electron microscopy was utilized to investigate their morphological properties. The investigation of upconversion photoluminescence properties of the synthesized ceramics was conducted by analyzing upconversion emission spectra upon excitation with 980 nm light. Power dependence studies confirmed the presence of two-photon absorption processes in both PbNb2O6:Yb3+, Er3+ and PbNb2O6:Yb3+, Ho3+ ceramics. Temperature-dependent experiments from 303 K to 513 K demonstrated significant variations in emission intensities and fluorescence intensity ratios (FIR), enabling the assessment of temperature changes. The absolute sensitivity of PbNb2O6 ceramic co-doped with Yb3+, Er3+ ions reached its maximum value of 0.0056 K-1 at 513 K, while the maximum relative sensitivity of 0.697% K-1 was recorded at 339 K. For PbNb2O6 ceramic co-doped with Yb3+, Ho3+ ions, the maximum values of absolute and relative sensitivities were 0.048 K-1 and 0.8% K-1 at 513 K and 473 K, respectively. These results highlight the potential applications of PbNb2O6:Yb3+, Ln3+ (Ln3+=Er3+/Ho3+) ceramics in advanced temperature sensing based on photoluminescence. [ABSTRACT FROM AUTHOR]

High‐sensitivity flexible wireless passive sensors with multiple parameters sensing capability are highly demanded for industrial production, structural health monitoring, and medical care. In this study, a microstructure‐enhanced temperature and pressure dual‐mode inductance capacitance (LC) sensor is developed with a particle swarm optimization‐back propagation (PSO‐BP) algorithm for simultaneous measurement of temperature and pressure. In the device, two interdigital electrodes connected at different parts of an inductor is used to realize dual‐mode measurement of pressure and temperature, with reduced volume and cost of the device as well as avoided interaction of the superimposed inductance. The sandpaper‐molded polydimethylsiloxane microstructures are employed to enhance the device sensitivity, with six and three times of improvement in temperature and pressure sensitivity, respectively. A PSO‐BP neural network suitable for regression analysis of low dimensional small sample data is constructed to achieve the simultaneous measurement of pressure and temperature with an accuracy up to 94%. Furthermore, investigations have proved the promising applications of the dual‐mode LC sensor in health monitoring of lithium‐ion batteries and detection of plantar pressure for medical care. [ABSTRACT FROM AUTHOR]

In recent years, people have higher requirements for temperature measurement with the development of optical temperature measurement. Meanwhile, the emission intensity of most fluorescent materials is quenched by thermal effects as the temperature rises, making it challenging to meet the specifications of fluorescent materials employed in the field of pyrometry. In this work, the pure phase of Yb3+/Er3+ ions co-doped Sc 2 W 3 O 12 phosphor was successfully prepared. Sc 2 W 3 O 12 : Yb3+, Er3+ samples showed strong green emission and weak red emission. The optimal doping concentrations of Yb3+ and Er3+ ions are 0.3 and 0.02, respectively. The potential upconversion luminescence (UCL) mechanism was investigated by analyzing the UCL spectra, downshift emission spectra and power dependence spectra of Yb3+/Er3+ ions co-doped Sc 2 W 3 O 12. The upconversion emission excitation path is mainly through Er3+ ions from 4I 11/2 absorption photon excitation to 4F 7/2 energy level, then the photons of 4F 7/2 relaxes to green and red emission energy levels and returns to ground state for emitting green and red light. In addition, according to the UCL green light intensity increasing with temperature, it serves as an optical temperature sensor. The temperature sensitivity of the sample was explored in the temperature range of 298 K–673 K. This study provides new materials and ideas for non-contact temperature sensing. [ABSTRACT FROM AUTHOR]

The redshift of the charge transfer band (CTB) edge of phosphor induced by temperature rise is pervasively accompanied by antithermal quenching. Accordingly, exploring the mechanism of the CTB redshift is thus not only propitious for optimizing the sensitivity of optical thermometry but also tenders a new idea for the design of antithermal quenching phosphors. Herein, a family of YP 1-x V x O 4 :Eu3+ phosphors were designed via the V5+/P5+ ion substitution strategy. With the increase of the V5+ ratio, the relative integral intensity of the 5D 0 →7F 2 transition multiplies from 1.25 to 28.67 times under CTB edge excitation. Moreover, by Gaussian fitting, the reduction degree of vanadate band gap energy 1E (1T 1)→1B 2 (1T 2), 1A 2 (1T 1)→1B 2 (1T 2) increased from 0.122 eV and 0.065 eV to0.162 eV and 0.083 eV, respectively, in the range of 303–523 K. Both reveal an enhance in redshift of the excitation spectra. The decrease of charge transfer state (CTS) energy level and the alteration of photoelectron thermal population are two mechanisms that induce CTB redshift. Specifically, the decrease of the CTS level is dominant in the YPO 4 :Eu3+ sample, and the thermal population of the higher vibrational levels of the VO 4 3−ground state is dominant in the presence of a tiny amount of V5+ doping. In addition, according to the experimental phenomenon, a dual-mode temperature sensing scheme based on excitation intensity ratio (EIR) and single band ratiometric (SBR) is proposed. Y 0.9 P 0.1 V 0.9 O 4 :0.1Eu3+ achieves a maximum sensitivity of S r-max = 4.040 % K−1 and a minimum temperature determination uncertainty of δT = 0.124 K at 323 K, which excellent performance indicates that this is a promising non-contact optical thermometer. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The design of active and inert shell in NaYF 4 :Yb,Er @ NaYF 4 UCNPs exhibits the superior luminescence under 980 nm excitation. • NaYF 4 @NaYF 4 :Yb,Nd,Er core–shell UCNPs demonstrate optimized luminescence under 808 nm laser excitation because the inert core can bring the activators into closer proximity with each other. • NaYbF 4 as an active layer improves temperature sensitivity with S r = 1.12 %K−1 under 808 nm excitation. Research on the core–shell design of rare earth-doped nanoparticles has recently gained significant attention, particularly in exploring the synergistic effects of combining active and inert shell layers. In this study, we successfully synthesized 8 types of spherical core–shell Na-based nanoparticles to enhance the efficiency of core–shell design in upconversion luminescence and temperature sensing through the strategic arrangement of inert and active layers. The most effective upconversion luminescence was observed under 980 nm and 808 nm laser excitation using NaYF 4 inert shell NaYF 4 :Yb3+, Er3+@ NaYF 4 and NaYF 4 @ NaYF4:Yb3+, Nd3+ core–shell nanostructures. Moreover, the incorporation of the NaYbF 4 active shell structure led to a significant increase in relative sensitivity in ratio luminescence thermometry. Notably, the NaYF 4 :Yb3+, Nd3+, Er3+@ NaYbF 4 core–shell structure demonstrated the highest relative sensitivity of 1.12 %K−1. This research underscores the crucial role of inert shell layers in enhancing upconversion luminescence in core–shell structure design, while active layers play a key role in achieving high-sensitivity temperature detection capabilities. [ABSTRACT FROM AUTHOR]

Rice husk is usually generated as waste in large quantities but yet to be optimally utilized. Due to the pollution effects associated with poor approach prevalently adopted for its disposal, valorizing it into economical and sustainable material for building construction is a necessary option to provide solution for future generation. In this research, separate dry mortars were prepared using cement grades 32.5R and 42.5N and the influence of rice husk ash (RHA) inclusion on their electrical characteristics was investigated. The materials used were batched by volume and the RHA was utilized as a partial substitute for cement at 10 % level. All the samples were cured for 21 days and then allowed to dry completely prior to the tests implementation. The results showed decrease in electrical resistance with temperature (ranging from 20oC to 50oC) due to incorporation of the RHA. Though samples with the RHA content possessed ability to act as smart mortars for temperature monitoring/sensing, utilization of cement grade 42.5N ensured a better performance. By utilizing rice husks in such undertakings, their associated disposal problems could be tackled and construction of inexpensive but sustainable building with large temperature sensing capability could be enhanced.

Understanding how cells sense temperature is a fundamental question in biology and is pivotal for the evolution of life. In numerous organisms, temperature is not only sensed but also generated due to cellular processes. Consequently, the mechanisms governing temperature sensation in various organisms have been experimentally elucidated. Extending upon others’ proposals and demonstration of protein- and nucleic acid-based thermosensors, and utilizing a colonial India ‘punkah-wallahs’ analogy, I present my rationale for the necessity of temperature sensing in every organelle in a cell. Finally, I propose temperature-sensing riboceptors (ribonucleic acid receptors) to integrate all the RNA molecules (mRNA, non-coding RNA, and so forth) capable of sensing temperature and triggering a signaling event, which I call as thermocrine signaling. This approach could enable the identification of riboceptors in every cell of almost every organism, not only for temperature but also for other classes of ligands, including gaseous solutes, and water.

An "turn-on" polymer nanothermometer based on aggregation induced emission is applied for intracellular temperature sensing. [Display omitted] • The polymer nanothermometer shows TICT and AIE properties. • The nanothermometer exhibits "turn on" fluorescence in response to temperature. • It is applied for temperature sensing of lysosomes in A549 cells. Temperature measurements at the nanoscale facilitate the understanding of physiological processes related to heat in cells. Herein, we prepare a tetraphenylethylene-functionalized fluorophore (TPPEBr) with dual characteristics of twisted intramolecular charge transfer (TICT) and aggregation induced emission (AIE). It is polymerized with a thermo-responsive unit NIPAM to construct a fluorescent polymer nanothermometer (PNIPAM-TPPEBr). The phase transition behavior of PNIPAM from dispersed chains to dense spheres in aqueous media promotes the aggregation of TPPEBr fluorophores, which makes the fluorescence of PNIPAM-TPPEBr enhance with increasing temperature. Furthermore, the phase transition of PNIPAM is accompanied by a significant decrease in the polarity of the microenvironment, resulting in a blue shift in the emission wavelength of TPPEBr. Varying the ratio of NIPAM and TPPEBr can regulate the thermo-responsiveness of PNIPAM-TPPEBr in the physiological temperature range (31–38 °C), and the maximum relative thermal sensitivity reaches 13.2 % °C−1. The thermo-responsive performance of this nanothermometer is independent of the intracellular microenvironment, and it is successfully applied in the temperature imaging of A549 cells. Under the stimulation of ionomycin and oxidative phosphorylation inhibitor, the cell temperature increased by ca. 1.5 °C and ca. 1.0 °C, respectively. [ABSTRACT FROM AUTHOR]

Abstract The accurate characterization of local magnetic fields and temperature is vital for the design of electronic systems. To meet this imperative, we present a novel non-contact approach for simultaneous quantitative magnetic field imaging and temperature sensing using magnetooptics and a bismuth-doped yttrium iron garnet film with out-of-plane anisotropy. For the direct signal quantification, a Stokes polarization camera is employed in a conventional magnetooptical microscope. The magnetization in the garnet is modulated with an external magnetic field to continuously image the Faraday rotation at four distinct points along the saturating magnetization loop. The method enables sensing of the magnetooptical signal in saturation, the magnetooptical susceptibility, the temperature, and self-calibrated driftfree imaging of the out-of-plane magnetic field component. A spatial resolution of magnetic field in the micrometer range with millisecond exposure time is demonstrated. The method is verified by analyzing the stray magnetic field distribution of electrical current in a wire simultaneously to the Joule heating induced by the applied current.

Crystalline α‐Gd2(MoO4)3 is synthesized by sintering at 800 °C using a coprecipitation method to prepare the precursor. The resulting α‐Gd2(MoO4)3 displayed a monocrystalline structure with a strong main peak (‐221) in the X‐ray diffraction signal. To develop a light‐emitting material, rare earth ions are added during synthesis. By doping with Tb3+ and Eu3+, the Gd2(MoO4)3 down‐conversion phosphor shows potential for use in UV–LED chips, counterfeit money prevention, and fingerprint identification. Additionally, co‐doping with [Er3+]/[Yb3+] and [Ho3+]/[Yb3+] ions produce green and red emissions when applied to a 980 nm LED chip, useful for anti‐counterfeit ink. The magnetic properties of gadolinium are leveraged to confirm magnetic resonance imaging luminescence. A flexible composite for heat detection and explored various applications for its use is also developed. [ABSTRACT FROM AUTHOR]

BaGeTeO6: Nd3+/Yb3+/Ho3+ green up-conversion phosphors were synthesized using the high-temperature solid-state reaction method. The optimal doping concentrations for the three dopant ions Nd3+, Yb3+, and Ho3+ were determined to be 1 mol%, 6 mol%, and 0.8 mol%, respectively, through the method of controlling variables. By analyzing the dependence of the up-conversion luminescence intensity on the pump current of the 980 nm laser, it was found that the green and red up-conversion emissions of Ho3+ ions under 980 nm laser excitation were both two-photon processes. Furthermore, the influence of temperature on the up-conversion luminescent properties of BaGeTeO6: Nd3+/Yb3+/Ho3+ green up-conversion phosphors under 980 nm laser excitation was investigated, and the temperature sensing properties of Ho3+ ions were discussed. The results indicated that, at room temperature and higher temperatures, both the red and green up-conversion emissions of the sample were two-photon processes. Within the range of excitation current used in the experiment, the ratio of red to green up-conversion luminescence intensity of Ho3+ ions was independent of the laser excitation current but correlated with the sample temperature. In the temperature range of 303–723 K, the ratio of red to green up-conversion luminescence intensity of Ho3+ ions exhibited a nonlinear relationship with temperature. Comparing the temperature sensing sensitivity of Ho3+ in different matrices, the results indicated that the sample possessed high temperature sensing sensitivity. [ABSTRACT FROM AUTHOR]

Eu2+‐doped phosphors have attracted the great attention of researchers in the past decade. However, Eu2+ dopant in inorganic hosts often suffers from the self‐oxidation effect, therefore causing the attenuated emission intensity and quantum efficiency. In this regard, developing Eu2+ doped phosphors with the prohibited self‐oxidation effect of Eu2+ and increased thermal stability is urgently required. Herein, an innovative cyan‐light emitting Li2CaSiO4:Eu2+/Eu3+, Lu3+ (LCSO) phosphor is designed. Both experimental results and theoretical calculations demonstrate that adding Lu3+ restricts the self‐oxidation of Eu2+ into Eu3+, thus improving the emission of Eu2+. Meanwhile, the Lu3+ introduction brings out excellent thermal stability. Finally, an efficient WLED with a color temperature (CCT) of 4573 K and a high color rendering index (Ra) of 84.2 is obtained using the as‐prepared phosphor due to the perfect compensation of the cyan light. As the introduction of Lu3+ improves the stability of Eu2+, a much greater difference in PL decay rate between Eu2+ and Eu3+ in LCSO is reached, thereby improving their sensitivity in temperature sensing. The strategy of Lu3+ introduction for prohibiting the self‐oxidation of Eu2+ for efficient and stable Eu2+ emission may stimulate some new ideas in designing high‐performance phosphors for more diverse applications. [ABSTRACT FROM AUTHOR]