Thermally Coupled Energy Levels Research Articles

Simultaneous modulation of multicolor upconversion emission and thermal‐sensing performance of Ba5Zn4Y8O21 phosphors

AbstractIn this study, we report the modulation of the emission color and optical temperature‐sensing properties of Er3+ in Ba5Zn4Y8O21 crystals. Er3+ single‐doped Ba5Zn4Y8O21 phosphors showed green emission under 980 nm excitation. When codoping with Yb3+ ions, the red emission component from the Er3+ ions increased significantly, and the sample emission turned orange. Yb3+–Er3+ codoped Ba5Zn4Y8O21 samples exhibited bright red emission with a maximum IR/IG value of 89.30 when excited with a longer wavelength, 1550 nm. A broad range of emission colors could be modulated by adjusting the dopant concentration. The possible modulation mechanisms and upconversion processes were analyzed based on the luminescence decay curves and power‐dependent emission intensities. Furthermore, the optical temperature‐sensing properties of Ba5Zn4Y8O21:Er3+ and Ba5Zn4Y8O21:Er3+, Yb3+ phosphors with thermal coupled energy levels (TCELs) and nonthermal coupled energy levels (N‐TCELs) of Er3+ ions were investigated using fluorescence intensity ratio technique. Based on the TCELs (2H11/2/4S3/2), the Er3+ single‐doped and Yb3+–Er3+ codoped Ba5Zn4Y8O21 phosphors present the similar optical thermometry behaviors under 980 and 1550 nm excitation. The highest absolute (Sa) and relative sensitivity (Sr) are 3.95 × 10−3 K−1 at 573 K and 1.31% K−1 at 303 K, respectively. Based on N‐TCELs (4F9/2/2H11/2), the temperature‐sensing performance depends on the Yb3+ dopant and excitation wavelength. The highest values for Sa and Sr reached 5.46 K−1 at 303 K and 1.38% K−1 at 573 K for the Ba5Zn4Y8O21:Er3+, Yb3+ phosphor under 1550 nm excitation, respectively. In addition, the present phosphor exhibited high stability and repeatability over a wide temperature range. These results indicate that the multicolor modulation upconversion Ba5Zn4Y8O21‐based phosphor can be considered a potential reusable optical thermometer for noncontact temperature detection.

New Na5Y(MoO4)4: Yb3+, Er3+ phosphors: Up-conversion luminescence and temperature sensing characteristics

Currently, the development of new up-converting fluorescent materials for manufacturing optical temperature sensing device with high accuracy and precision has always been significant pursuits of many researchers. In this work, we have synthesized new Na5Y(MoO4)4: Yb3+/Er3+ phosphors via solid-state reaction route, and the influences of dopant concentration on UCL performance were discussed. The results revealed that the introduction of Yb3+ enhanced the luminescence intensity, and the optimal concentration combination was 0.20Yb3+/0.04Er3+. Doping Yb3+ and Er3+ did not affect the phase structure of the phosphor. Several emission peaks at 529, 552 and 668 nm of Er3+ were found to be temperature-dependent within the scope of 298–573 K. Through the utilization of fluorescence intensity ratio technique (FIR, I529/I552 and I529/I668), dual-mode temperature measurement was realized. The maximum relative sensitivity (Sr-max) of 1.77 % K−1 (@298 K) utilizing thermally coupled energy levels (TCELs) and the maximum absolute sensitivity (Sa-max) of 12.0 % K−1 (@573 K) based on the non-TCELs were achieved. Furthermore, Yb3+/Er3+ co-doped Na5Y(MoO4)4 phosphors exhibited excellent photothermal repeatability and temperature resolution. The results indicated that the novel Na5Y(MoO4)4 phosphor provided the possibility for the development of temperature sensing materials with high sensitivity.

Novel transparent glass-ceramics of NaLu2F7:Yb3+, Er3+ for accurate temperature sensing and anti-counterfeiting

The development of up-conversion materials with strong emission and low thermal effect is crucial for achieving higher temperature sensing accuracy. In this work, novel transparent NaLu2F7:xYb3+, 0.02Er3+ (x = 0, 0.2, 0.4, 0.6, 0.8, 1) glass-ceramics (GCs) were manufactured by melt-quenching technique. The temperature sensing capabilities of GC20 based on thermally coupled energy levels (TCELs) and non-thermally coupled energy levels (nTCELs) were studied, which enable self-calibration. Our findings reveal that the maximum relative sensitivity (SRmax) of TCELs and nTCELs are 1.19% K−1 and 0.89% K−1 at 313 K, respectively. More importantly, the UC luminescence color of GC20 varies from yellow to green as the excitation power increases. The unique phenomenon can be utilized for anti-counterfeiting purposes without any background interference. Overall, our results demonstrate that these novel GCs possess significant potential in accurate temperature sensing and anti-counterfeiting fields.

Up-conversion emission of Yb3+/Tm3+-activated SrNb2O6 lead-free glass-ceramics for optical temperature sensors

The development of fluorescent materials with excellent thermal stability and high-temperature sensitivity is urgently needed to meet the rapidly growing temperature sensors. In this paper, the SrO-SrF2-Nb2O5-Al2O3-B2O3-SiO2-Yb2O3-Tm2O3 glasses were fabricated by high-temperature melting method. And the glass-ceramic with the optimal concentration of 4.0Yb3+/0.1Tm3+ was obtained after heat treatment of 800 °C for 30 min. Only the nanocrystalline SrNb2O6 crystal phase with a tetragonal structure precipitated from the glass matrix. The as-prepared glass-ceramic material produced intense blue light emission and excellent thermal cyclic stability. Utilizing the fluorescence intensity ratio technique, the glass-ceramic material showed the supreme relative sensitivity of 2.63 %K−1 at 298 K using thermally coupled energy levels (TCELs) and the highest absolute sensitivity of 22.10 %K−1 at 598 K employing non-TCELs. These findings show that Yb3+/Tm3+- doped SrNb2O6 glass-ceramic material is a promising candidate for optical sensor application.

Multi-strategy ratiometric luminescent thermometry based on Dy doped CaWO4 phosphors independent of excitation wavelength

This paper explores the detailed photoluminescence (PL) behaviors of Dy3+ doped CaWO4 (Dy:CaWO4) phosphors under multi-ultraviolet wavelength excitation. Moreover, it proposes multi-strategy ratiometric thermometry based on luminescence intensity ratio (LIR) from the transitions of thermally coupled energy levels (TCLs) of Dy3+. Under excitation of multiple ultraviolet wavelengths, the Dy:CaWO4 phosphors exhibited multi-wavelength responsive PL characteristics of Dy3+ with strong blue and yellow emissions from Dy3+ TCLs transitions. The temperature-dependent PL properties of Dy:CaWO4 phosphors were investigated over a temperature range of 300∼650 K. Multi-strategy ratiometric luminescent thermometry was examined under various excitation wavelengths by the thermal equilibrium population of Dy3+ TCLs. The proposed six LIR schemes based on the PL emissions of Dy3+ exhibited a good quantitative relationship with temperature. They showed well-luminescent thermometric behaviors with high absolute and relative sensitivities due to the largest energy gap of TCLs and a relatively larger LIR value. The thermometry properties of the multiple LIR schemes were independent of excitation wavelength, attributed to the stable site symmetry of Dy3+ and the thermal equilibrium population of TCLs under different excitation wavelengths. The multi-strategy ratiometric thermometry of Dy3+ demonstrated the merit of high sensitivity, excellent stability, and repeatability, indicating the potential luminescent thermometric application of Dy:CaWO4 phosphors.

A multi-mode optical thermometry based on the up-conversion La2MgGeO6: Er3+, Yb3+ phosphor

The up-conversion (UC) La2MgGeO6: Er3+, Yb3+ phosphors were prepared by a high-temperature solid-phase method. The structural phase and luminescence characteristics of the samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence spectra. The research systematically investigated a multi-mode optical thermometry based on fluorescence intensity ratios (FIR) of the thermal-coupled energy levels 2H11/2/4S3/2, non-thermal-coupled energy levels 4S3/2/4F9/2, and the fluorescence lifetime of the 4S3/2 state. Based on these methods, the maximum relative sensitivity reached 1.130%K−1, 0.623%K−1, and 2.914%K−1, respectively. According to the results, the manufactured samples have remarkable temperature measuring performance, which is characterized by a broad temperature measurement range, high sensitivity, and superior stability.

Ultra-sensitive luminescent ratiometric thermometry based on matrix energy transfer in Dy3+ doped CaWO4 phosphors

In this paper, we report the photoluminescence (PL) properties of the WO42− group and Dy3+ ions for a new highly sensitive luminescent ratiometric thermometry in Dy3+ doped CaWO4 (CaWO4:Dy) phosphors. Under 259 nm excitation, the violet emission from the WO42− group, as well as the blue and yellow emissions of Dy3+ from the transitions of thermally coupled energy levels (TCLs) of 4I15/2 and 4F9/2, were both investigated, which ascribed to an energy transfer from WO42− to Dy3+. The thermal-enhanced PL of Dy3+ and the thermal-quenched PL of WO42− were detected with increasing temperature. By taking advantage of the opposite temperature-dependent PL evolution, a new thermometry strategy was proposed based on the luminescence intensity ratio (LIR) between Dy3+ and WO42− having a quantitative relationship with temperature. The maximum absolute and relative temperature sensing sensitivities were as high as 449.52*10−4 K−1 and 21.03% K−1 at 300 K, respectively, which were superior to those reported previously for traditional TCLs-based LIR thermometry. This study demonstrated the potential of CaWO4:Dy phosphors in temperature sensing and provided guidance for constructing an effective ratiometric thermometry strategy with excellent and reliable sensing performance.

Ratiometric fluorescence temperature sensing based on thermal coupling energy levels of a single-lanthanide dysprosium MOF

The luminescence intensity ratio generated by thermally coupled energy levels (TCELs) based on lanthanide ions has been demonstrated to be a reliable technique for optical thermometry. In this study, we developed a new single-lanthanide (S’LnMOF), DyBPDA, by a straightforward solvothermal method with the [1,1′-biphenyl]-3,5-dicarboxylic acid (H2BPDA) as a linker and Dy3+ as a single luminescence center. Based on the dual emission originating from TCELs of Dy3+ (4I15/2 and 4F9/2 → 6H15/2), DyBPDA enables as a ratiometric temperature sensor in the range 303–443 K with a maximum relative sensitivity of 0.41%·K−1. This work provides a reference for the facile preparation of S'LnMOF, which further contributes to the optical temperature sensing technology based on TCELs.

Upconversion luminescence and temperature sensing performance of Er3+ ions doped self-activated KYb(MoO4)2 phosphors

In this work, a series of self-activated KYb(MoO4)2 phosphors with various x at% Er3+ doping concentrations (x = 0.5, 1, 3, 5, 8, 10, 15) was synthesized by the solid–state reaction method. The phase structure of the as-prepared samples was analyzed by X-ray diffraction (XRD), XRD Rietveld refinement and Fourier transform infrared (FT-IR) spectroscopy. The as-prepared samples retain the orthorhombic structure with space group of Pbcn even Er3+ doping concentration up to 15 at%. High-purity upconversion (UC) green emission with green to red intensity ratio of 55 is observed from the as-prepared samples upon the excitation of 980 nm semiconductor laser and the optimum doping concentration of Er3+ ions in the self-activated KYb(MoO4)2 host is revealed as 3 at%. The strong green UC emission is confirmed as a two-photon process based on the power-dependent UC spectra. In addition, the fluorescence intensity ratios (FIRs) of the two thermally-coupled energy levels, namely 2H11/2 and 4S3/2, of Er3+ ions were investigated in the temperature region 300–570 K to evaluate the optical temperature sensor behavior of the sample. The maximum relative sensitivity (SR) is determined to be 0.0069 K−1 at 300 K and the absolute sensitivity (SA) is determined to be 0.0126 K−1 at 300 K. The SA of self-activated KYb(MoO4)2:Er3+ is almost twice that of traditional KY(MoO4)2:Er3+/Yb3+ codoping phosphor. The results demonstrate that Er3+ ions doped self-activated KYb(MoO4)2 phosphor has promising application in visible display, trademark security and optical temperature sensors.

In-situ confinement of ultra-small NaYF4:Yb3+/Er3+ UCNPs as multifunctional ratiometric thermometer and optical heater

Lanthanide-doped upconversion (UC) nanomaterials with zero background auto-fluorescence are of extensive interest in optical fields. Here, a NaYF4:Yb3+/Er3+@Zr-UiO-66 nanostructure was prepared by simultaneously encapsulating NaYF4:Yb3+/Er3+ nanoparticles (NPs) and promoting the nucleation of UiO-66 under solvothermal condition. Traditional nanosize-surface induced defects and grain boundaries of NaYF4:Yb3+/Er3+ upconversion nanoparticles (UCNPs) were greatly minimized; enabling a highly efficient energy transfer confirmed by the prolonged fluorescence lifetime and enhanced UC emission of NaYF4:Yb3+/Er3+@Zr-UiO-66 nanocomposite. The optical thermometry property of nanocomposite was investigated based on the fluorescence intensity ratio (FIR) technique in the temperature range of 303–393 K. The maximum relative temperature sensitivities (Sr) were calculated to be 1.02 and 0.73% K−1 based on a pair of thermally coupled energy levels (TCLs) of (2H11/2 → 4I15/2, 4S3/2 → 4I15/2) and another pair of non-thermally coupled energy levels (NTCLs) of (2H11/2 → 4I15/2, 4F9/2 → 4I15/2), respectively. Besides, it exhibited effective internal optical heating property due to the thermal excitation between the two adjacent TCLs of 2H11/2 and 4S3/2 in NaYF4:Yb3+/Er3+ UCNPs as heated by increasing the laser power. This work demonstrates a feasible confined synthesis of NaYF4:Yb3+/Er3+@Zr-UiO-66 nanocomposite with extreme UC emitting performance, and it holds great potential acting as both ratiometric thermometer and optical heater for multifunctional applications.

Activating ultralow upconversion nanothermometry in neodymium sublattice for heart tissue imaging rapid-responsive

The fields of biosensitivity and biological imaging have received a lot of attention from rare earth-doped upconversion nanoparticles (UCNPs). However, owing to the relatively large energy difference of rare earth ions, biological sensitivity based on UCNPs is restricted to detect at low temperature. Here, we design core-shell-shell NaErF4:Yb@Nd2O3@SiO2 UCNPs as a dual-mode bioprobe that produces blue, green, and red multi-color upconversion emissions at extremely low temperatures between 100 K and 280 K. Based on the thermally coupled energy levels (TCELs) of Er3+ (2H11/2 and 4S3/2) and Nd3+ (4F5/2 and 4F3/2) at 100 K, the greatest relative sensitivity (SR) approaches 12.7% K−1. NaErF4:Yb@Nd2O3@SiO2 injection is used to achieve blue upconversion emission imaging of frozen heart tissue, showing that this UCNP can serve as a low-temperature sensitive biological fluorescence.

Optical temperature-sensing properties with various strategies for Y18W4O39 phosphors by near-infrared excitation

The Er3+-Yb3+ and Tm3+-Yb3+ rare earth (RE) ions co-doped Y18W4O39 (YWO) phosphors were prepared by the solid-state reaction method. Their phase purity, upconversion (UC) luminescence and optical temperature sensing behaviors were investigated in detail. The single-phase samples are obtained when the RE ions are incorporated into the YWO host lattice. The characteristic transition peaks of Er3+ and Tm3+ appear under irradiation with the 980 nm laser light source and their optimal doping concentrations are determined. The fluorescence intensity ratio (FIR) strategy is utilized to assess the optical temperature-sensing properties, including the thermally coupled energy levels (TCELs) and non-TCELs. It is found that the FIRs of Er3+ (I524/I546 and I659/I524) and Tm3+ (I477/I484 and I791/I652) change obviously as the temperature varies. The temperature-induced changes for FIRs are also checked, which indicates an excellent reproducibility and repeatability. A series of sensitivity curves are presented as a function of absolute temperature, and the maximum sensitivity values are obtained. Furthermore, the decay curves are studied to better understand the UC energy transfer process. The above results reveal that the developed phosphors are promising to be a candidate for optical temperature sensor.

A multi-mode optical thermometer based on the up-conversion Ca3Y2Ge3O12: Er3+, Yb3+ phosphor

In order to develop a new up-conversion luminescent temperature measurement material with a garnet structure, Ca3Y2Ge3O12: Er3+, Yb3+ phosphors were prepared by a simple high temperature solid phase method. The structural phase and luminescence characteristics of the samples were characterized by X-ray powder diffraction, field emission scanning electron microscopy and photoluminescence spectra. It can be observed that the characteristic emission of Er3+ ion appears in the sample under 980 nm excitation, and it's up-conversion emission intensity increases with the increase of Yb3+ ion concentration. The maximum relative sensitivity is 1.29 %K−1, 1.09 %K−1 and 1.03 %K−1 based on the different temperature dependence of the thermal coupled energy levels (TCELs), non-thermal coupled energy levels (NTCELs) and the fluorescence lifetime (FL) of 4S3/2 state, respectively. The results show that Ca3Y2Ge3O12: Er3+, Yb3+ phosphor is excellent a material for optical temperature measurement.

Luminescence, optical and temperature sensitive characteristics of Tm3+ /Yb3+ doped fluoride phosphosilicate glass ceramics

Yb3+/Tm3+ doped fluoride phosphosilicate glass ceramics with Sr6Ca4(PO4)6F2 nanocrystals were prepared by the controlled crystallization method. The research results of up-conversion (UC) spectra showed that the optimal dopant concentration of Yb3+ and Tm3+ was 3.0 and 0.1 mol%, respectively. In the visible range, the transmissivity of the precursor glass (PG) was close to 90%, while that of glass ceramics was approximately 82%. And the luminescence intensity of glass ceramics was stronger than that of PG. The Rietveld XRD refinement results confirmed that Yb3+ and Tm3+ ions partially entered the Sr6Ca4(PO4)6F2 crystal to form the solid solution. The highest relative sensitivity (Sr-max) of glass ceramics based on thermally coupled energy levels (TCELs) was 2.77% K-1 (@298 K). In view of non-TCELs, the highest absolute sensitivity (Sa-max) of glass ceramics was 12.21% K-1 (@698 K). These findings demonstrate that the as-prepared glass ceramic can be expected to be suitable for optical temperature sensing applications.

Ultralow pressure sensing and luminescence thermometry based on the emissions of Er3+/Yb3+ codoped Y2Mo4O15 phosphors.

Pressure and temperature are fundamental physical parameters, so their monitoring is crucial for various industrial and scientific purposes. For this reason, we developed a new optical sensor material that allows monitoring of both the physical parameters. The synthesized material exhibits upconversion (UC) emission of Er3+ in the red and green spectral regions under NIR (975 nm) laser irradiation. These UC emissions are strongly temperature-dependent, allowing multimode temperature sensing, either based on the luminescence intensity ratio between thermal-coupled energy levels (TCLs) or non-thermal-coupled energy levels (NTCLs) of Er3+ ions. Meanwhile, the luminescence lifetime of the 4S3/2 state of Er3+ ions was used as the third temperature-dependent spectroscopic parameter, enabling multi-parameter thermal sensing. Moreover, the observed enhancement of laser-induced heating of the sample under vacuum conditions allows for the conversion of the luminescent thermometer into a remote vacuum sensor. The pressure variations in the system are correlated with changes in the band intensity ratio (525/550 nm) of Er3+ TCLs, which are further applied for optical, contactless vacuum sensing. This is because of the light-to-heat conversion effect, which is greatly enhanced under vacuum conditions and manifests as a change in the intensity ratio of Er3+ bands (525/550 nm). The obtained results indicate that an Y2Mo4O15:Er3+/Yb3+ (YMO) phosphor has great application potential for the development of multi-functional and non-invasive optical sensors of pressure and temperature.

Optical temperature-sensing phosphors with high sensitivities in a wide temperature range based on different strategies.

Rare earth ion doped luminescent materials are considered potential candidates with a wide range of applications because of their unique optical characteristics. In this work, single-phase Yb3+-Er3+ and Yb3+-Tm3+ co-doped La1.55SiO4.33 (LS) phosphors of a hexagonal system for optical thermometers are reported. Three characteristic emissions of Er3+ were observed at 521, 553 and 659 nm in the LS:Yb3+,Er3+ phosphors under 980 nm excitation, which are assigned to the 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions, respectively. In the LS:Yb3+,Tm3+ phosphors, one can find two strong emissions at 474 and 790 nm and two weak emissions at 648 and 685 nm. Their upconversion (UC) luminescence mechanisms were studied from their pump-power-dependent spectra. When the samples were measured at various temperatures, their spectral features revealed that different fluorescence intensity ratio (FIR) strategies can be used to characterize their optical temperature-sensing behaviors. The sensor sensitivities were determined from the temperature-dependent UC emission spectra using thermally coupled energy levels (TCELs) and non-TCELs, which had improved compared with those of some other reported optical temperature-sensing luminescent materials. The device fabrication indicated that the developed UC phosphors are promising for applications in optical thermometers.

The excellent dual optical thermometry of the Yb3+, Er3+ doped SrLu2O4

SrLu2O4: Yb3+, Er3+ samples were achieved successfully via a traditional solid-state method at 1450 °C. As 980-nm laser exciting, the UC spectra include red and green emissions mainly centering on 665 and 552 nm, respectively. The red is dominant, and the green part is a relative weakness. For all co-doped samples, intense red radiation is obtained. Meanwhile, the experimental formulas about pumping power and spectrum intensity helped us comprehend the up-conversion processes further, and the conclusion is a two-photon process in UC. The 4S3/2 and 2H11/2 levels ions are thermal coupled energy levels. We also investigated thermometric characteristics of the samples on the fluorescence intensity ration technology. For SrLu2O4: Er3+/Yb3+, it can be used as a temperature sensor by using its green emission and red emission, and the sensor sensitivity was calculated. The maximum absolute sensitivity and the relative sensitivity is 0.00226 K-1 and 0.0119 K−1 at 513 K for green emission and the maximum absolute sensitivity and the relative sensitivity is 0.00126 K-1 and 0.0026 K−1 at 303 K for red emission. The fluorescence intensity ratio (FIR) values are almost stable and accurate in repeated tests. As a result, the SrLu2O4: Er3+/Yb3+ samples would useful hopefully to optical engineering and sensors.

Energy transfer mechanism and new ratiometric thermometry strategy by the blue and yellow emissions of Dy

In this paper, we report the energy transfer mechanism between Dy3+ ions as well as a new optical ratiometric thermometry strategy in Dy3+ doped CaWO4 (CaWO4:Dy) phosphors. The optimal Dy3+ doping concentration was determined and the electric dipole-dipole interaction among Dy3+ was investigated based on the analysis of the concentration-dependence luminescent properties in CaWO4:Dy phosphors. The photoluminescence (PL) of two blue and two yellow emissions produced by Dy3+ transitions from the thermally coupled energy levels (TCLs) of 4I15/2/4F9/2 to the 6H15/2 ground level and 4I13/2 metastable level, respectively, exhibited opposite PL behavior with increasing temperature. The luminescence intensity ratio (LIR) between blue and yellow emissions (B/Y) was discovered to have a quantitative relationship with temperature based on the classic thermalized population distribution of TCLs. In comparison to traditional thermometry based on the LIR of two blue emissions, the proposed new ratiometric thermometry based on the LIR of B/Y demonstrated good optical thermometry behavior with extended temperature detection range to cryogenic region, excellent absolute sensitivity, good repeatability, and high accuracy, which can also be applied to other Dy3+ doped materials such as Y3Al5O12 and NaYF4 phosphors using either down- or up-conversion PL of blue and yellow emissions.

Optical thermometry based on enhanced up-conversion luminescence in Ba3-yYb4-xO9:xEr3+,yM2+ (M=Mg, Sr, Ca) phosphors

As significantly growing demand for noncontact temperature sensors, the exploitation of superior optical thermometers is increasingly urgency. Herein, novel Ba3Yb4O9:Er3+ phosphors were successfully synthesized and the strategy of appropriate cations substitution (Mg2+, Ca2+, Sr2+) was designed to strengthen the up-conversion luminescence as well as thermometric performance of Ba3Yb4O9:Er3+. Among them, Ba3-yYb4-xO9:xEr3+,yMg2+ is identified to be an excellent optical thermometric material. Based on the fluorescent intensity ratio from thermal coupled energy levels (2H11/2/4S3/2) of Er3+, the relative (SR) and absolute (SA) sensitivities of Ba2.9Yb3.6O9:0.4Er3+,0.1Mg2+ can reach as high as 1.29% K−1 at 302 K and 0.43% K−1 at 573 K, respectively, which are higher than that of Mg2+-free doped Ba3Yb3.6O9:0.4Er3+ (SR:1.15% K−1 at 302 K; SA:0.38% K−1 at 523 K). In addition, the sample exhibits outstanding reversibility and reproducibility. These results imply that Ba3-yYb4-xO9:xEr3+,yM2+ is a promising candidate applied in temperature sensing fields.

Ratiometric temperature sensing and molecular logic AND gate execution via Eu3+ doped BaWO4 nanophosphor

Self-calibrated Luminescence thermometry (LT), a contactless temperature measurement technique has gained significant recognition owing to its idiosyncratic contours over conventional thermal sensors. Apart from high relative sensitivity, large operating thermal window, insignificant absolute error with minimum temperature uncertainty are perquisite requirements for feasible endeavor of the developed temperature sensors. In the current work, after efficaciously preparation of Eu3+ doped BaWO4 via hydrothermal route, the inherent thermally coupled energy levels (TCEL) 5D1 and 5D0 of Eu3+ were employed for ratiometric temperature sensor design in 80–500 K range. The intense down-shifting luminescence and high temperature sensitivity elicit small temperature uncertainty (0.05 K) and a low absolute error (−0.12 to 0.14 K). Nevertheless, along with good repeatability (>95%) in thermal cycles, the prepared nanophosphor also demonstrates good stability (after repeated thermal cycles). Additionally, carried out Judd-Ofelt analysis provides significant insight in LT based upon emission behavior of Eu3+. A high value of relative sensitivity (1.65% K−1 and 2.95% K−1 from decay kinetics and ratiometric respectively) with chromaticity shift of 78* 10−3 manifests a visual change in inherent red emission profile from the prepared phosphor. Further, exploiting heat and incident UV as input, the prepared phosphor material is utilized to develop an exclusive dry molecular logic gate (here AND) implementation. As versatile spectroscopic probe, Eu3+ ion was exercised for details structural analysis to disclose the change of local site symmetry in BaWO4 due to aliovalent substitution.