Potential Application In Temperature Research Articles

Enhanced Efficiency, Broadened Excitation, and Tailored Er3+ Luminescence Triggered by Te4+ Codoping in Cs2NaYbCl6 Crystals for Multifunctional Applications.

The quest for efficient and tunable luminescent materials has been at the forefront of research in the fields of chemistry and materials science. This work delves into the investigation of the luminescence properties of Er3+ ions triggered by 1% Te4+ in the environmentally benign perovskite Cs2NaYbCl6 (CNYC) crystals, aiming to enhance their efficiency and tune the luminescence color. The ratio of the green (2H11/2, 4S3/2-4I15/2) to red (4F9/2-4I15/2) emissions of Er3+ can be freely tunable by varying the concentration of Er3+ and producing the defects induced by codoping Te4+. The calculations reveal that the multiexcitonic excitations of Er3+ stem from f-f (4I15/2-4G11/2, 2H9/2) rather than d-f transitions. The broadened excitation, tuning of color, and enhancement of efficiency achieved in the luminescence perovskite crystals Cs2NaYbCl6:Te4+, Er3+ (CNYC:Te4+,Er3+) presents promising opportunities for the development of advanced optoelectronic devices with superior performance. Moreover, our investigation demonstrates the tunable luminescence response of CNYC:Er3+ to temperature variations, offering potential applications in temperature sensing.

Synergetic Conformational Regulations in Ground and Excited States for Realizing Stimulus-Responsive and Wide-Tuning Room-Temperature Phosphorescence.

Understanding the changes of molecular conformations is crucial for realizing multiple emissive triplet states in room-temperature phosphorescence (RTP) materials. In this work, we report two molecules, 4,4'-dimethylbenzil (DMBZ) and 4,4'-di-tert-butylbenzil (DBBZ) with conformation-dependent luminescence, and demonstrate that stimulus-responsive and wide-tuning RTP emissions can be realized via synergetic conformational regulations in ground and excited states. Due to conformational changes, DMBZ and DBBZ show abundant RTP variations upon external stimuli, including light, force, heat, and fumigation. Notably, DBBZ exhibits multiple conformational changes in both ground and excited states, which endow DBBZ with multiple emissive states and unique stimulus-responsive behaviors. DBBZ presents multiple phase transitions between the supercooled liquid state and different solid states accompanied by different phosphorescence transitions, in which the excited-state conformations are effectively regulated. Moreover, wide-range RTP regulations (between cyan, green, and yellow) are realized in both single component and host-guest systems of DBBZ, showing potential applications in temperature sensing, multicolor dynamic displays, and information encryption. These results may provide new visions for understanding the complicated conformational changes in the aggregated state, as well as unique insights into the relationship between molecular conformations, RTP emissions, and stimulus responsiveness.

Temperature dependence of luminescence color of Mn2+-doped ZnCN2 phosphor

Photoluminescent materials which show multi-wavelength luminescence have potential applications in temperature sensing device. In this study, Mn2+-doped ZnCN2 phosphor was prepared by ammonia nitridation of Zn-Mn oxalate precursors in the presence of carbon nitride. Upon UV excitation, it showed photoluminescence band at 580 nm due to isolated Mn2+ ions as well as minor broad emission bands at 500 and 670 nm due to anion vacancies and Mn-Mn pairs in the ZnCN2, respectively. Since the intensities of the luminescent bands had different temperature dependencies, and the total luminescence color changed from orange at 80 K to yellow green at 500 K.

Coprecipitation synthesis, structural, optical properties, and thermometry application of Tm3+/Yb3+ co-doped YPO4 phosphor

Coprecipitation synthesis and characterization of upconverting YPO4: Tm3+, Yb3+ phosphor is reported in the present work. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Scanning electron microscopy (SEM) were used to examine the structure and morphology of the synthesized phosphor. Tm3+ and Yb3+ co-doped YPO4 material have the tetragonal xenotime crystal structure of space group I41/amd. Upconversion luminescence properties of prepared phosphor are studied under the near-infrared (NIR) 980 nm laser excitation. The intense emission peaks are observed at ∼473 nm and ∼796 nm due to electronic transitions (1G4→3H6) and (3H4→3H6), respectively, and relatively weak emission peaks are observed at 654 nm and 700 nm which are attributed to (1G4→3F4) and (3F2,3→3H6) transitions of Tm3+, respectively. Tm3+ (0.3 mol%)/Yb3+(10 mol%) is the optimized concentration that gives intense and sharp emission in NIR (∼796 nm) region. Power dependence studies have been done to understand the upconversion emission mechanism. The fluorescence intensity ratio of (3F2,3→3H6)/(3H4→3H6) transitions of Tm3+ in the temperature range 323 K–598 K is analyzed. Relative and absolute temperature sensitivity are also calculated. Maximum relative sensitivity is 1.86% K−1 at 323 K and absolute sensitivity increases with rising temperature. Excellent sensitivity, avoidable spectral overlap, and intense upconversion emission, in the first biological window under NIR excitation, show that the prepared material is multifunctional and may have potential applications in temperature sensing and optical heaters for bio-molecules.

Nanostructured PbS-Doped Inorganic Film Synthesized by Sol-Gel Route.

IV-VI semiconductor quantum dots embedded into an inorganic matrix represent nanostructured composite materials with potential application in temperature sensor systems. This study explores the optical, structural, and morphological properties of a novel PbS quantum dots (QDs)-doped inorganic thin film belonging to the Al2O3-SiO2-P2O5 system. The film was synthesized by the sol-gel method, spin coating technique, starting from a precursor solution deposited on a glass substrate in a multilayer process, followed by drying of each deposited layer. Crystalline PbS QDs embedded in the inorganic vitreous host matrix formed a nanocomposite material. Specific investigations such as X-ray diffraction (XRD), optical absorbance in the ultraviolet (UV)-visible (Vis)-near infrared (NIR) domain, NIR luminescence, Raman spectroscopy, scanning electron microscopy–energy dispersive X-ray (SEM-EDX), and atomic force microscopy (AFM) were used to obtain a comprehensive characterization of the deposited film. The dimensions of the PbS nanocrystallite phase were corroborated by XRD, SEM-EDX, and AFM results. The luminescence band from 1400 nm follows the luminescence peak of the precursor solution and that of the dopant solution. The emission of the PbS-doped film in the NIR domain is a premise for potential application in temperature sensing systems.

A Rolling‐Mode Al/CsPbBr3 Schottky Junction Direct‐Current Triboelectric Nanogenerator for Harvesting Mechanical and Solar Energy

AbstractDirect‐current triboelectric nanogenerators (DC‐TENGs) can directly convert mechanical energy into direct current (DC) electrical energy, exhibiting wide applications in micro/nano power sources, etc. Herein, a rolling‐mode DC‐TENG based on the tribo‐photovoltaic effect is proposed, which verifies that the tribovoltaic effect can be achieved in DC‐TENGs with a rolling structure instead of a conventional sliding structure. Utilizing the all‐inorganic perovskite CsPbBr3, a multifunctional DC‐TENG with excellent performance, that is capable of collecting both mechanical and solar energy is produced by constructing a dynamic Al/CsPbBr3 Schottky junction. Under illumination by light, the output voltage and current density reach 3.69 V and 11.46 A m−2, respectively. Furthermore, the output current of the dynamic Al/CsPbBr3 junction under illumination is 4.7 times higher than that in dark conditions. Meanwhile, the device exhibits excellent stability and the output performance does not significantly degrade after more than 10 min of cycling. In addition, the DC‐TENG shows potential applications in temperature and humidity sensing and directly charging capacitors. This work not only realizes a multifunctional DC‐TENG for simultaneously harvesting mechanical and solar energy, but also provides a novel route to enhance the work stability through a rolling‐mode device structure, which is of great significance for accelerating the development and applications of high‐performance DC‐TENGs.

Preparation, luminescence properties, and application of temperature sensing and anti‐counterfeiting of La2MgTiO6:Yb3+/Ln3+/Mn4+

AbstractThe doping of transition metal ions in the up‐conversion (UC) luminescent material doped with Yb3+/Ln3+ is a facile way to increase their UC luminescence intensities and alter their colors. In this study, La2MgTiO6:Yb3+/Mn4+/Ln3+ (Ln3+ = Er3+, Ho3+, and Tm3+) phosphors showing excellent luminescence properties were prepared by a solid‐state method. The sensitivity of the La2MgTiO6:Yb3+/Ln3+/Mn4+ phosphor was double that without Mn4+, because Mn4+ affects the UC emissions of Ln3+ via energy transfer between these ions. Moreover, Mn4+ also acts as a down‐conversion activator, which can combine with UC ions to achieve multi‐mode luminescence at different wavelengths. Under 980 nm excitation, these samples emit green light (from Er3+ and Ho3+) and blue light (from Tm3+). In contrast, under 365 nm excitation, they emit red light (from Mn4+). Further testing revealed that the La2MgTiO6:Yb3+/Mn4+/Ln3+ phosphors have potential applications in temperature sensing and anti‐counterfeiting.

Carbon dots derived from cellobiose for temperature and phosalone detection

Cellobiose, the hydrolysis product of cellulose and the dimer of glucose, was employed to synthesize carbon dots (CDs) via a simple hydrothermal method. The inducing of nitrogen can act as a “molecular glue”, more and more carbon clusters were “glued” together, which would push the hydrothermal reaction in the positive direction. Besides, the linear response of the fluorescence of N-CDs to temperature ensured its potential application in temperature sensing. In the temperature range of 10∼80 °C, the fluorescence of as-prepared N-CDs was reversible and recoverable. Moreover, the dual fluorescence centers and dual-absorption bands of the as-prepared N-CDs permitted the novel dual-mode ratiometric assays for phosalone detection. The linear range and limit of detection (LOD) for dual fluorescence center-based ratiometric assay were 0.12∼5.45 μg/mL and 42.90 ng/mL, respectively. While that for the dual absorption-based ratiometric assay were 0.02∼1.40 μg/mL, and 6.67 ng/mL, respectively.

Fiber-Based Thermoelectric Materials and Devices for Wearable Electronics.

Fiber-based thermoelectric materials and devices have the characteristics of light-weight, stability, and flexibility, which can be used in wearable electronics, attracting the wide attention of researchers. In this work, we present a review of state-of-the-art fiber-based thermoelectric material fabrication, device assembling, and its potential applications in temperature sensing, thermoelectric generation, and temperature management. In this mini review, we also shine some light on the potential application in the next generation of wearable electronics, and discuss the challenges and opportunities.

First-principles study on site occupancies and excitation spectra of Na3LuSi2O7:Ce3+

The observed strongly temperature-dependent luminescence of Ce3+-doped Na3LuSi2O7 indicates its potential applications in temperature sensing. The experimental assignments of excitation spectra to Ce3+ ions at two Lu sites are at odds with the empirical crystal-field analysis. Here, first-principles calculations were carried out to resolve the site occupancies of the Na3LuSi2O7:Ce3+ by considering the influence of the oxygen vacancy. The hybrid functional was utilized to overcome the well-known underestimation of the band gap so as to obtain energy levels of Ce3+ ions in the band gap more accurately. Based on our calculated results of defect formation energies and energy level structures, one set of the excitation spectra is assigned to Ce3+ ions at Lu(2) sites and the other to Ce3+ ions at Lu(2) sites with an adjacent O(3) vacancy. Furthermore, the thermal stabilities of these two luminescence centers are predicted, which is consistent with the previous reported experimental results. Our results exhibit the significance of intrinsic defects on the spectra and thermal quenching behavior of Ce3+-activated phosphors.

Pressure- and temperature-dependent luminescence from Tm3+ ions doped in GdYTaO4

Luminescent properties of Tm3+-doped GdYTaO4 are studied for exploring their potential applications in temperature and pressure sensing. Two main emission peaks from 3H4 → 3H6 transition of Tm3+ are investigated. Intensity ratio between the two peaks evolves exponentially with temperature and has a highest sensitivity of 0.014 K−1 at 32 K. The energy difference between the two peaks increases linearly with pressure increasing at a rate of 0.38 meV/GPa. Intensity ratio between the two peaks and their emission lifetimes are also analyzed for discussing the pressure-induced variation of the sample structure. Moreover, Raman spectra recorded under high pressures indicate an isostructural phase transition of GdYTaO4 occurring at 4.46 GPa.

CaSnO3: Pr3+ phosphor for new application in temperature sensing.

CaSnO3: Pr3+ phosphor for new application in temperature sensing was investigated. CaSnO3: 0.3%Pr3+ had distorted orthorhombic perovskite structure and Pr3+ occupied Ca2+ sites due to their similar ionic radii. CaSnO3: 0.3%Pr3+ had spherical particles with mean size of 0.816μm. The electric dipole-dipole interaction could explain the concentration quenching mechanism. The chromaticity coordinates were (0.1324, 0.3847), located in greenish-blue region and the average afterglow decay time was 60.2s for CaSnO3: 0.15%Pr3+, which had potential applications for LED and emergency lighting. CaSnO3: 0.3%Pr3+ had the activated energy of 0.380eV. The maximum relative temperature sensitivity for CaSnO3: 0.3%Pr3+ was 7.57% K-1 at 298K and relative sensitivity was as high as 6722.76/T2K-1, which was better than that of most Pr3+ doped phosphors and had potential application in temperature sensing. Moreover, the possible luminescence and long afterglow mechanisms and thermal quenching process of 3P0 level through IVCT state were proposed.

Study on the structure and optical properties of phosphor Ca3La3(BO3)5:Dy3+ for potential application in temperature sensing

A series of single phase calcium lanthanum borates Ca3La3(BO3)5:Dy3+ (CLBD) phosphors were synthesized via conventional solid-state reaction. The introduction of Dy3+ with a preferred location on La3+ over Ca2+ site in CLB is owing to the different ionic radii and charge valent and confirmed by XRD, Rietveld refinements and photoluminescence analysis. Under ultraviolet (UV) excitation, tunable colors of high-brightness emissions were realized by controlling the Dy3+ doping concentrations. The CLBD demonstrated potential application as non-contact and self-calibration thermometer. Two different effective strategies for temperature sensing were investigated, namely, fluorescent intensity ratio (FIR) and emission decays. The FIR method was employed the fluorescence ratio of 4I15/2 → 6H15/2/4F9/2 → 6H15/2 due to the Boltzmann-like distribution of the two exited energy levels with temperature while the decay lifetimes were fitted and compared by adopting three different theoretical models: multiphonon relaxation (MR), charge transfer (CT) and transformed CT (TCT, which further consideration the relationship between CT energy and temperature). Altogether, the CLBD phosphors show promising potentials for temperature sensing.

Optical thermometry using up and down conversion photoluminescence mechanism in Y2Zr2O7: Er3+ phosphors with excellent sensing sensitivity

In this article, photoluminescence up and down conversion properties of Er3+ activated Y2Zr2O7 (YZO) phosphors have been investigated. All the compositions have been synthesized via hydrothermal method. Various characterization techniques have been used to characterize the samples. Powder X-ray diffraction reveals the crystallization of the fluorite phase of all samples. FESEM technique and EDX spectroscopy were performed for surface morphology and elemental analysis of the samples. The optical band gap is appeared to increase after doping. Photoluminescence down conversion (DC) excitation (PLE) spectra exhibit a strong near UV absorption at 378 nm. All the doped samples under 378 nm excitation display the featured emission of Er3+ ions. The variation of DC PL intensity and the lifetimes with temperature were also investigated within the temperature range 77K–475K. Excitation power dependent up conversion (UC) emission and temperature dependent UC emission spectra within 303K–483K of the optimized sample were examined with 980 nm laser excitation. The fluorescence intensity ratio (FIR) technique and the variation of the average lifetime with temperature have been used to study the temperature sensing behaviour of the reported phosphors. Comparatively high sensitivities suggest the reported phosphors could have potential applications in temperature sensing and also could be a UV and NIR to green converter phosphors material.

High sensitivity micro-fiber Mach-Zehnder interferometric temperature sensors with a high index ring layer.

The influence of the high index ring layer (HIRL) in a tapered fiber Mach-Zehnder interferometer (MZI) on the interference observed, and thus on its potential applications in temperature sensing, has been investigated. The MZI was comprised of a tapered Ring Core Fiber (RCF), spliced between two single mode fibers (SMF). Since part of core mode from the SMF was converted into cladding modes in the RCF, due to the mismatch in the cores between the RCF and SMF, the residual power enters and then propagates along the center of the RCF (silica). The difference in phase between the radiation travelling along these different paths is separated by the HIRL to generate an interference effect. Compared with fiber interferometers based on core and cladding mode interference, the thin fiber HIRL is capable of separating the high order cladding modes and the silica core mode, under grazing incident conditions. Therefore, the optical path difference (OPD) and the sensitivity are both substantially improved over what is seen in conventional devices, showing their potential for interferometric temperature sensor applications. The optimum temperature sensitivity obtained was 186.6 pm/°C, which is ∼ 11.7 times higher than has been reported previously.

Regulatable Thermochromic Hydrogels via Hydrogen Bonds Driven by Potassium Tartrate Hemihydrate

The thermochromic materials have received widespread attention due to their ability to adjust color under the environmental stimuli. However, it is still a challenge in the sensitivity of transmittance on temperature. Here, a novel type of thermochromic hydrogel is proposed and demonstrated to improve the sensitivity of transmittance to temperature. At different temperatures, the size of the micelle could be changed, giving the thermochromic ability for the hydrogel. As the temperature gradually increases to the thermochromic transition temperature (TTT), the hydrogels undergo a transition from opaque to transparent (90%) at 550 nm visible radiation the same as the near-infrared region. The reverse process occurs when the temperature drops below TTT. Meanwhile, TTT could be adjusted over a range of temperature from 25 to 35 °C by changing the content of potassium tartrate hemihydrate. This hydrogel provides a new approach to obtain thermochromic materials and has wide potential application in temperature ...

Design of a six-band terahertz metamaterial absorber for temperature sensing application

We present a simple design of a six-band terahertz metamaterial absorber (MMA). The unit-cell of the MMA consists of a metallic cross-cave-patch (CCP) structure and an InSb dielectric spacing layer stands on a ground-plane. The permittivity of the InSb dielectric layer can be adjusted efficiently by the variation of external temperature. The numerical simulation results show that the MMA has six distinct absorption peaks from 0.4 THz to 2.2 THz, and the absorption peak frequencies can be tuned easily by changing the external temperature. The surface current distributions of the top layer and back layer of the unit-cell structure are studied to better understand the physical mechanism of the proposed MMA. The six-band strong absorption of the MMA is originated from the excitations of high-order magnetic resonance. In addition, the sensitivity S is investigated to explore temperature sensing performance of the device, and the value of S is 10.3 GHz/K, 8.1 GHz/K, 6.7 GHz/K, 6.4 GHz/K, 5.5 GHz/K and 5.4 GHz/K, respectively. The design of the MMA could find potential applications in temperature sensing or other optoelectronic related areas in terahertz region.

Observation of a red Ce3+ center in SrLu2O4:Ce3+ phosphor and its potential application in temperature sensing.

In Ce3+ activated SrLn2O4 type phosphors (Ln = Y, Lu, Sc, etc.) only one Ce3+ center was previously reported to show a blue emission band. In this paper, we report the observation of a second Ce3+ center in SrLu2O4:Ce3+. The new center shows a red emission band peaking at 600 nm with an excitation band at 485 nm. We attributed the new center (Ce(ii)) to the substitution of the Lu3+ site and the original blue center (Ce(i)) to the substitution of the Sr2+ site. Spectroscopy studies indicate that Ce(i) centers are preferentially formed at a low doping concentration and the number ratio of Ce(i)/Ce(ii) decreases with increasing Ce3+ concentration until beyond 0.002. The fluorescence lifetimes of the two centers were measured for various doping concentrations. Energy transfer from Ce(i) to Ce(ii) was observed. It was found that the emission intensity of Ce(ii) centers reduces much faster than that of Ce(i) with increasing temperature from 83 K up to 350 K, implying their potential application in temperature sensing based on their temperature dependent intensity ratios. A relative sensing sensitivity as high as 2.28% K-1 at 283 K was achieved.

Optical temperature sensing using upconversion luminescence in rare-earth ions doped Ca2Gd8(SiO4)6O2 phosphors

A series of Yb3+-Er3+, Yb3+-Ho3+, and Yb3+-Tm3+ doped Ca2Gd8(SiO4)6O2 (CGS) phosphors were synthesized by solid-state reaction method, and their upconversion (UC) luminescence properties for temperature sensing were studied. Upon 980 nm excitation, the green and red emissions of Er3+ were observed, and the optimal Er3+ concentration was determined to be 3 mol%. For the CGS:10%Yb3+,yHo3+ phosphors, three emission peaks in the green, red and near-infrared region appear. It was found that the relative intensities of Ho3+ different emissions change with Ho3+ concentration, which has been explained by the cross-relaxation process. The strongest Tm3+ emission appeared at 790 nm, attributed to the 3H4-3H6 transition. The optimal Tm3+ concentration was determined to be 0.5 mol%. The temperature sensing behavior was evaluated by employing the thermally-coupled or non-thermally coupled levels of Er3+, Ho3+ and Tm3+. The maximum sensitivities obtained are 3.71×10−3 and 1.12 K-1 for CGS:10%Yb3+,3%Er3+, 0.111 K-1 for CGS:10%Yb3+,3%Ho3+ and 3.3×10−4 K−1 for CGS:10%Yb3+,0.5%Tm3+, respectively. The high sensitivities indicate the present phosphors could have potential application in temperature sensing.

Eu3+ activated LiSrVO4 phosphors: Emission color tuning and potential application in temperature sensing

A series of color-tunable emitting LiSrVO4:Eu3+ phosphors were synthesized by solid state reaction. The Luminescence properties and temperature sensing performance were investigated. Under near ultraviolet (NUV) excitation, LiSrVO4: Eu3+ exhibited both the green broad band luminescence due to (VO4)3−groups and red sharp emission peaks of sensitized Eu3+ ions. The tunable color of high-brightness emission from green to red is realized by controlling the Eu3+ doping content. The optical thermometry of LiSrVO4: Eu3+ was studied via excitation intensity ratio between V-O charge transfer band and Eu3+ f-f transition at low temperature (10–323 K). The highest absolute sensitivity SA is found to be 8.6%. The red emission intensity of Eu3+ shows a linear relationship in high temperature range of 298–573 K. The maximum value of relative sensitivity SR is established as 2.2%K−1 @573 K. The LiSrVO4:Eu3+ phosphors might be a promising candidate for NUV based phosphor and temperature sensing in a wide temperature range.