Absolute Sensitivity Research Articles

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.

Probing multifunctional applications of LiCa2Mg2V3O12: Sm3+ phosphor using Judd-Ofelt analysis and dual mode non-contact optical thermometry

LiCa2Mg2V3O12:Sm3+ phosphors have been prepared by solid state method and analysed by X-ray diffraction, EDX-elemental mapping, UV–VIS-NIR spectroscopy, photoluminescence (PL) and temperature dependent photoluminescence (TDPL). The absorption spectra analysis using Judd-Ofelt theory provides the intensity parameters and manifest the covalent nature of Sm-O bond. The PL spectra monitored at 338 nm excitation exhibits emission peaks of Sm3+ at 567, 617 and 651 nm in addition to the broad band emission of LiCa2Mg2V3O12 host. The Commision Internationale deL’Eclairage (CIE) coordinates, correlated color temperature (CCT) and color rendering index (CRI) values elucidate the efficient yellow emission of phosphors. The radiative parameters are evaluated and have outrageous branching ratio and cross section that aids in visible laser applications. The optical thermometry of phosphor is carried out by utilizing FIR method through selecting spectral modes 6H5/2/VO43-, 6H7/2/VO43- and 6H9/2/ VO43-. The mode 6H9/2/ VO43- have higher absolute sensitivity (Sa) and relative sensitivity (Sr) values of 0.4418 K−1 and 1.6079% K−1. The temperature resolution of modes are 0.1633, 0.1677 and 0.1563 K respectively. The thermochromic study reveals the high chromaticity shift (Δs = 0.1869) of phosphor and the Sa(x) and Sr(x) values evaluated based on CIE coordinates are 0.0011 K−1 and 0.2407% K−1 respectively. The PL and TDPL characteristics of prepared phosphor suggest that it have multifunctional application in the fields of lasers, thermo-sensors, thermochromic displays and LEDs.

Upconversion fluorescent Sr9In(PO4)7:Yb3+, Er3+ phosphors with applications in temperature measurement and anti-counterfeiting

In this work, Yb3+ and Er3+-co-doped Sr9In(PO4)7 upconversion fluorescent materials with dual functionality were synthesized though simple high-temperature solid state method. Based on International Commission on Illumination (CIE) color coordinates, the calculation of color purity at different temperatures demonstrates the attainment of highly pure green luminescence (color purity >90 %) for the synthesized materials. The analysis of activation energy proves that synthesized materials are stable. Utilizing the fluorescence intensity ratio (FIR) of the thermally coupled energy levels (2H11/2, 4S3/2) as a metric for optical sensing performance, absolute sensitivity and relative sensitivity are determined, and their maximum values are 0.44 % and 1.13 %, respectively. Inspired by the variation in CIE coordinates with temperature, thermally responsive two-dimensional barcode image was developed, demonstrating the practical application of Sr9In(PO4)7:Yb/Er materials in the field of information security and anti-counterfeiting.

Early “Red Flags” in hospitalized patients with COVID-19

Relevance. Among the studies during the COVID-19 pandemic, a special role is played by studies examining the prognostic value of clinical, laboratory and instrumental markers in patients. Biomarkers with absolute sensitivity and specificity for predicting the outcome of a new coronavirus infection have not been identified yet.Aim: To identify early clinical and laboratory predictors of severity and mortality in hospitalized patients with COVID-19 and to evaluate the effectiveness of the pharmacotherapy in outpatient and early hospital settings.Methodology and research methods. A retrospective, comparative study was carried out. Medical data from 745 adult patients with COVID-19, hospitalized in the respiratory hospital of the Siberian State Medical University (Tomsk) from 05/16/2020 to 09/30/2020 were included. The main group consists of patients who were discharged from the hospital. The comparison group included patients with a fatal outcome of the disease.Results. The group of deceased patients was characterized by older age and a greater number of comorbid diseases (р < 0.0001), the presence of pneumonia during the year preceding COVID-19 (р < 0.0001) and risk factors for the development of Pseudomonas aeruginosa infection (р < 0.005). Early admission to the hospital (р = 0.0110), severe dyspnea (р < 0.0001) with a decrease in oxygen saturation below reference values (р < 0.0001) are also associated with the risk of a fatal outcome. Anosmia was significantly more common in the group of surviving patients.The number of platelets, the absolute number of lymphocytes, amounts of total protein, albumin (р < 0.0001), sodium (р = 0.0013) in the first 48 hours of hospitalization in the main group were significantly higher. The number of leukocytes (p = 0.0078), neutrophils (p < 0.0001), neutrophil-lymphocyte ratio (p < 0.0001), concentrations of glucose, aspartate aminotransferase, urea, creatinine, C-reactive protein and lactate dehydrogenase were significantly lower in the main group. Serum procalcitonin levels > 0.5 ng/ml were 5 times higher in deceased patients during early period of hospitalization.Conclusion. Clinical, anamnestic and laboratory factors were identified through this study. These factors may be useful in the early period of hospitalization for accurate assessment of risks of severe ill, effective disease management and reduction of mortality in hospitalized patients with COVID-19.

Temperature sensing materials based on the fluorescence intensity ratio in Li2Ba5W3O15:Dy3+ phosphors

One of the interesting uses of phosphors is the development of non-contact thermometers apart from their usage as visible photonic devices. A series of Dy3+-doped Li2Ba5W3O15 (LBW) phosphors were successfully synthesized using high temperature solid-state reaction process. The crystal structure and morphology of LBW:xDy3+ phosphors were studied using X-ray diffraction (XRD), Rietveld refinements and field effect scanning electron microscopy (FE-SEM) with energy dispersive x-ray (EDX) analysis. The XRD and photoluminescence (PL) analyses validated the effective substitution of Ba2+ ions with Dy3+ ions. Two prominent emission peaks were found at 493 and 583 nm corresponding to 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions respectively under 368 nm excitation wavelength. A comprehensive analysis has been carried out on the usage of the Dy3+ doped LBW phosphors in fluorescence intensity ratio (FIR) thermometry. The optical temperature measurement performance of the LBW:xDy3+ phosphor was achieved by utilizing distinct thermal quenching transitions, specifically on 4F9/2→6H15/2,13/2, at temperatures ranging from 293 to 443 K. The as-prepared phosphors demonstrate excellent performance as optical thermometers, with a maximum relative sensitivity (Sr) of 0.7% K−1 at 293 K, an absolute sensitivity (Sa) of 4.68 K−1 at 443 K and a temperature resolution of ∼0.51 at 443 K. These values indicate that the phosphors are highly responsive to changes in temperature, making them suitable for non-contact thermometry applications.

LiYF4:Er3+ for near-infrared luminescent cryothermometry

We explore the possibility of using the luminescence of LiYF4:Er3+ to measure cryogenic temperatures. Temperature dependences (2.5 K → 190 K) of the luminescence intensity ratios and linewidths are studied in the regions of infrared transitions 4I13/2 → 4I15/2 (∼1.5 μm) and 4I11/2 → 4I15/2 (∼0.98 μm) using high-resolution Fourier spectroscopy. Pairs of spectral lines 6550–6510 cm−1, 10176–10161 cm−1, and 6482–6478 cm−1 can be used for ratiometric Boltzmann thermometry with maximum absolute sensitivity at temperatures of 28.8, 10.8, and 2.9 K, respectively, and corresponding relative sensitivities of 6.9, 18.5, and 70% K−1 at these temperatures. The temperature dependence of the linewidth of 6510 cm−1 line is favorable for measuring higher temperatures.

Echolocating Bats Have Evolved Decreased Susceptibility to Noise-Induced Temporary Hearing Losses.

Glenis Long championed the application of quantitative psychophysical methods to understand comparative hearing abilities across species. She contributed the first psychophysical studies of absolute and masked hearing sensitivities in an auditory specialist, the echolocating horseshoe bat. Her data demonstrated that this bat has hyperacute frequency discrimination in the 83-kHz range of its echolocation broadcast. This specialization facilitates the bat's use of Doppler shift compensation to separate echoes of fluttering insects from concurrent echoes of non-moving objects. In this review, we discuss another specialization for hearing in a species of echolocating bat that contributes to perception of echoes within a complex auditory scene. Psychophysical and behavioral studies with big brown bats show that exposures to long duration, intense wideband or narrowband ultrasonic noise do not induce significant increases in their thresholds to echoes and do not impair their ability to orient through a naturalistic sonar scene containing multiple distracting echoes. Thresholds of auditory brainstem responses also remain low after intense noise exposures. These data indicate that big brown bats are not susceptible to temporary threshold shifts as measured in comparable paradigms used with other mammals, at least within the range of stimulus parameters that have been tested so far. We hypothesize that echolocating bats have evolved a decreased susceptibility to noise-induced hearing losses as a specialization for echolocation in noisy environments.

Temperature sensing of novel Tb3+/Ho3+/Bi3+ co-doped lead-free double perovskite Cs2AgInCl6 nanocrystals

Up to now, the research field of application of lanthanide ions doped lead-free double perovskite Cs2AgInCl6 nanocrystals (NCs) was relatively limited, even less in temperature sensing. Here, Tb3+/Ho3+/Bi3+ ions were successfully doped into Cs2AgInCl6 NCs by hot-injection. The temperature sensing performance of co-doped NCs by using the fluorescence intensity ratio (FIR) was studied through the temperature-dependent emission spectra. By analyzing the influence of ions' doping concentration on temperature sensing performance, the optimal doping concentration of co-doped Cs2AgInCl6 NCs was determined to be 7 % Tb3+, 20 % Ho3+ and 1 % Bi3+. The highest absolute and relative sensitivities reach 1.48 K−1 and 2.48 %/K, respectively. We provide a new doping scheme of lead-free double perovskite NCs which have good temperature sensing performance. This co-doped NCs have great potential application value in non-contact temperature sensing in nanoscale.

Enhanced thermal stability and luminous properties of Dy3+/Tm3+/Eu3+ doped glass ceramics containing Sr4Bi(PO4)3O crystalline phases based on back energy transfer

White light emitting and optical temperature sensing materials with high thermal stability have broad market development prospects. The use of substrates with excellent thermal stability is a common idea to improve thermal stability, while the modulation of dopants to enhance thermal stability has been less studied. Therefore, in this work, Tm3+/Dy3+/Eu3+ doped transparent glass ceramics containing Sr4Bi(PO4)3O crystalline-phase were prepared by melt-crystallization method to achieve warm white light emission and optical temperature sensing with good thermal stability. Since the Tm3+-Dy3+ doped samples can only achieve cold white light emission, warm white light emission is obtained by adding Eu3+, which can emit red light. The application scenario of the material is expanded. The luminous intensities of Tm3+, Dy3+, and Eu3+ were 109.4 %, 89.1 %, and 70.7 % of those at room temperature, at 473 K. The increase in the emission intensity of Tm3+ was explained by the presence of back energy transfer (BET) from Dy3+ and Eu3+ to Tm3+. The chromaticity shift (Δε) of the samples was 2.43 × 10−4 and the luminescent colour was stable. The absolute sensitivity of the material can reach 0.69 K−1 at 473 K, and the relative sensitivity of the material can reach 1.60 % K−1 at 293 K. This work provides new ideas for the study of improving the thermal stability of materials.

High-performance of optical thermometry based on the non-thermally coupled levels in YVO4: Yb3+/Er3+/Tm3+ nanocrystals

Hydrothermally fabricated nanocrystals YVO4: Yb3+/Er3+/Tm3+ were investigated for up-conversion (UC) luminescence and optical temperature sensing performance. Upon 980 nm excitation, the luminescence intensity firstly increases and then decreases with raising Yb3+ doping content and reaches the maximum at 15 mol%. Considering the strong UC emission, the temperature sensing behavior was investigated based on the fluorescence intensity ratio (FIR) technique in temperature range of 293–573 K. The study was focused on the non-thermally coupled levels (NTCLs) including transitions 3F2,3 → 3H6 and 1G4→3H6 of Tm3+, transitions from the 4S3/2, stark sublevel 4S3/2(2), and 4F9/2 to the ground state 4I15/2 of Er3+ owing to their various temperature-dependent behaviors. Through using the stark sublevel 4S3/2(2) of Er3+, the maximum absolute sensitivity (SA) of 0.0563 K-1, relative sensitivity (SR) of 2.334 %K−1 and the minimum temperature resolution of 0.0058 K was achieved with good repeatability. The experimental results indicate that the as-obtained YVO4: 15%Yb3+/1%Er3+/1%Tm3+ nanocrystals can be potential candidates for nano-dimensional optical thermometry applications.

Upconversion Luminescence Properties and Temperature Sensing Characteristics of Tm3+, Yb3+-codoped SrAl2Si2O8 Phosphors with High Thermometric Sensitivities

In this paper, a SrAl2Si2O8:Tm3+,Yb3+ upconversion (UC) phosphor was prepared with a high-temperature solid-phase method, and proved that the strontium feldspar structure was an excellent UC matrix. The Tm3+ were shown to have a maximum relative thermometric sensitivity (Sr) of 1.67% K−1 at 298 K and a maximum absolute thermometric sensitivity (Sa) of 1.34% K−1 at 573 K. The non-thermally coupled energy level corresponded to the maximum relative thermometry sensitivity (Sr) of 2.4% K−1 at 298 K and a maximum absolute sensitivity (Sa) of 13% K−1 at 423 K. The use of the fluorescence intensity ratio of the nonthermally coupled energy levels of Tm3+ for temperature measurements improved the temperature measurement sensitivity of the same material. These results indicated that the phosphor has good temperature sensing performance with a wide sensing range and good stability and has potential thermometry applications in the first biological window.

Upconversion luminescence and temperature sensing performance of Zn2+-doped Ba2GdAlO5: Yb3+, Er3+ phosphors

Although upconversion luminescence (UCL) materials have attracted considerable attention in biomedical, lighting, anti-counterfeiting, and solar cells due to their excellent fluorescence properties, reports of the dibarium gadolinium aluminum oxide (Ba2GdAlO5) are scarce. Herein, we synthesized the single-phase Ba2GdAlO5 material with non-stoichiometric Ba2Gd1.06Al0.94O5 (denoted as BGAO, hereafter). The X-ray Rietveld refinement reveals that the substitution of Gd for Al accounts for the non-stoichiometry. Notably, the UCL properties of BGAO are realized by doping with Yb3+ and Er3+ ion pair, and it can be further enhanced significantly by co-doping with appropriate Zn2+ ions. The SEM images show that the particle size increases as the concentration of Zn2+ ions increases. The X-ray Rietveld refinement results of the Zn-doped BGAO: 0.1 Yb3+, 0.03Er3+ phosphor indicate the substitution of Zn2+ for Ba2+ and Al3+ ions simultaneously. Grain growth and lattice distortion account for the improvement of UCL properties after Zn2+ ions doping. In addition, the temperature sensing performance of the Zn2+-doped sample has been researched based on the fluorescence intensity ratio (FIR) technique, and the maximum absolute and relative sensitivities (SA-max and SR-max) are obtained to be 4.8 × 10−3 K−1 at 498 K and 1.1% K−1 at 298 K, respectively. This work provides a candidate with high UCL intensity for potential applications in optical temperature sensors.

Thermal Enhancement of Upconversion in Sub‐10 nm Yb3+/Er3+/Na+ Tridoped Cs2ZrF6 Nanocrystals for Ratiometric Temperature Sensing

AbstractAlkaline zirconium fluorides (AxZryFx+y, A = Li, Na, and K), featuring unique crystallographic structures, have recently emerged as a class of attractive hosts for fabricating lanthanide (Ln3+)‐doped upconversion nanocrystals (UCNCs) that exhibited distinct morphology, upconversion luminescence (UCL) performance, and physicochemical property. In this paper, for the first time the controlled preparation of Yb3+/Er3+‐doped UCNCs is reported based on the trigonal Cs2ZrF6 host, leading to tunable morphology and size of the resulting UCNCs by varying the reaction temperature and time. By further incorporating Na+ ions into the Cs2ZrF6 crystal lattice, sub‐10 nm Yb3+/Er3+/Na+ tridoped UCNCs with highly improved crystallinity and thus greatly enhanced UCL intensity are obtained. Moreover, these resulting UCNCs display abnormal thermal enhancement of UCL over a temperature range from 333 to 493 K, enabling the fabrication of supersensitive luminescent nanothermometers for temperature sensing. Based on the luminescence intensity ratio of two nonthermally coupled levels (i.e., 4F9/2 and 2H11/2) of Er3+, the as‐prepared Cs2ZrF6:Yb/Er/Na UCNCs exhibit an extremely large absolute sensitivity of 177.3% K−1 and a considerably high relative sensitivity of 1.52% K−1 at 333 K. These results unambiguously demonstrate that Cs2ZrF6 is a suitable host material for preparing small‐sized Ln3+‐doped UCNCs as nanothermometer for high‐performance ratiometric temperature sensing.

A three-mode temperature sensing based on UC luminescence of Er:PbF2 crystal

Optical temperature sensor, especially the temperature sensor made based on fluorescence intensity ratio (FIR) technology, have numerous applications in temperature detection. However, most of these sensing materials are phosphors, which still face challenges in maintaining their chemical stability. In contrast, crystal materials exhibit superior thermal stability and fluorescence stability. The temperature sensing characteristics of Er: PbF2 single crystal material were studied by the three modes temperature dependence curve. Excellent relative sensitivity and absolute sensitivity were obtained on FIR between two non-thermally coupled energy levels (non-TCEL: I(4F9/2)/I(4S3/2)) and two thermally coupled energy levels (TCEL: I(2H11/2)/I(4S3/2), and I(4S3/2)/I(4S3/2)) of Er3+ ions when excited by a 980 nm LD. Futhermore, with the increase of temperature, the luminescence emission color of the Er: PbF2 single crystal varied from green to yellow-orange. These discoveries suggest that the Er: PbF2 single crystal could serve as an excellent sensing medium for optical temperature sensors.

Temperature sensing performance of M2La8(SiO4)6O2:Ce3+(M=Ca, Sr, Ba) based on fluorescence intensity ratio of dual emission centers in different coordination environments

Rare earth doped luminescent sensing materials as non-contact thermometers have attracted extensive research interests due to their wide applications in areas like military, medical care, aerospace, etc. How to expand the working temperature range and improve the sensitivity has become the focus. In this work, we synthesized a series of apatite-structured luminescent temperature sensors M2La7.9Ce0.1(SiO4)6O2 (M = Ca, Sr, Ba) via isomorphic substitution. By monitoring the differential changes of emission intensities from Ce3+ at the 7-coordinate and 9-coordinate site respectively when temperature varies, the real-time temperature can be determined. These materials were proven to possess the maximum absolute sensitivity up to 0.825 × 10−3 K−1, 2.63 × 10−3 K−1 and 4.33 × 10−3 K−1, respectively. Meanwhile interesting regular patterns were observed for their temperature sensitivities with the substitution of Ca, Sr and Ba. Furthermore, through studying the temperature sensitivity of Ba2La8(SiO4)6O2:xCe3+ samples with different concentrations, it was found that when the Ce3+ content was at the optimal doping concentration of 0.7, the absolute sensitivity of the sample reached 14.64 × 10−3 K−1 at 573 K. This finding has opened up a new avenue for designing fluorescent temperature sensors.

Comparative study on fluorescence intensity ratio and chromatic coordinate temperature measurement using CsPbBr3-Eu3+ co-doped glass

We have fabricated CsPbBr3-Eu3+ co-doped glass for optical temperature measurement. Photoluminescence (PL) spectra, PL excitation (PLE) spectra and PL decay have been measured. The CsPbBr3 and Eu3+ show distinguishable PL spectra and different temperature dependences. Fluorescence intensity ratio (FIR) and chromatic coordinate temperature measurements are investigated. Absolute sensitivity (Sa), relative sensitivity (Sr) and temperature measurement accuracy (UT) are analyzed. For the FIR method, the Sa and Sr are better in comparison with other temperature sensing materials. The chromatic coordinate is calculated by using PL spectra. Comparing with FIR method, the chromatic coordinate method has smaller Sa and Sr, but better UT due to small uncertainty Ur(x). In addition, the chromatic coordinate method has linear temperature dependence, good compatibility and universality. Both FIR mode and chromatic coordinate mode have excellent temperature cycle characteristics..

Preparation of Er3+, Ho3+, Yb3+-doped Bi2WO6 upconversion luminescent materials and their temperature sensing properties

A high-temperature solid-phase method was used to prepare codoped Bi2WO6 upconversion luminescent materials with different concentrations of Er3+, Ho3+, and Yb3+. The microstructure, upconversion luminescence and temperature sensing properties of the synthesized powders were analyzed. X-ray diffraction (XRD) patterns showed that the doping of Er3+, Ho3+, and Yb3+ did not affect the orthorhombic crystal structure of the Bi2WO6 matrix material. As the calcination temperature increased from 800 °C to 1000 °C for 3h, the average particle sizes of the 1% Er3+, 1% Ho3+, 1% Yb3+: Bi2WO6 samples decreased, and the luminescence weakened. Scanning electron microscopy (SEM) images showed that the morphology of the sample for 1% Er3+, 1% Ho3+, 1% Yb3+: Bi2WO6 with calcination at 800 °C was nearly spherical, with particle sizes ranging from 1 to 5 μm and some agglomeration. SEM mapping showed that the elements were more uniformly distributed on the surfaces of the sample particles, and energy-dispersive X-ray spectroscopy (EDS) analysis showed that each element was distributed with in the particles. Er3+, Ho3+, and Yb3+ codoping was used to regulate the Yb3+ doping concentration, and under 980 nm excitation, the strongest upconversion emission was obtained for the prepared 1% Er3+, 1% Ho3+, 1% Yb3+ samples. Compared with that for the Er3+, Yb3+-doped Bi2WO6 sample, the luminescence intensity of the characteristic emission peak of Er3+ at 525 nm for the Er3+, Ho3+, Yb3+-doped sample was weakened, while the luminescence of the characteristic emission peak of Ho3+ was enhanced; these results indicated that energy transfer from Er3+ to Ho3+ occurred. The intensities of the four emission peaks at 525 nm, 546 nm, 660 nm, and 756 nm in the 1% Er3+, 1% Ho3+, 1% Yb3+-doped Bi2WO6 sample increased with increasing excitation pump power from 45 mW to 233 mW. Based on the relationship between the excitation pump power and the emission intensity, all four luminescence peaks originated from two-photon absorption. The fluorescence intensity ratio versus temperature was fitted using three different nonthermally coupled energy level pairs in the range from 298 K to 573 K. The maximum absolute temperature sensitivity of 0.296 K-1 was obtained at 573 K for the Ho3+ nonthermally coupled energy level pair, and the maximum relative temperature sensitivity of 0.279 K-1 was obtained at 298 K. The temperature resolution for characterization using the above nonthermally coupled energy level pairs was calculated, with the temperature resolution δT yielding a minimum value of 0.03 K. The CIE color coordinates at different temperatures were calculated, and the color coordinates gradually moved from the green region to the red region.

Novel GdAlGe2O7:Bi3+,Eu3+ phosphors with anti-thermal quenching properties for high sensitivity optical temperature measurement

The thermometry technique based on fluorescence intensity ratio has attracted much attention for its advantages of fast response, high accuracy, and non-contact. Here, we report a series of novel GdAlGe2O7:Bi3+,Eu3+ phosphors with anti-thermal quenching properties for high sensitivity optical temperature measurement. By constructing the energy transfer between Bi3+ and Eu3+ ions, the GdAlGe2O7:Bi3+,Eu3+ exhibits a rare anti-thermal quenching performance upon 285 nm excitation due to the redshift of the charge transfer band. Therefore, we designed ratiometric optical thermometers with high sensitivity based on the intense thermal quenching behavior of the Bi3+ ions and the anti-thermal quenching property of the Eu3+ ions with a relative sensitivity of 1.06% K−1 at 483 K and an absolute sensitivity of up to 0.0447 K−1 at 573 K. Our results not only reveal the optical behaviors of the Bi3+ and Eu3+ ions in GdAlGe2O7:Bi3+,Eu3+, but also propose that the synthesized phosphors have significant potential applications in the field of optical temperature measurement.

β-NaBiF4:Yb3+,Er3+:Novel green synthesis, crystal structure, upconversion luminescence and optical thermometry

Non-lanthanide based NaBiF4 host have evoked remarkable interest due to unique luminescent property and potential applications. Current synthetic methods are not environment friendly and causes pollution. This is the first report mentioning green synthetic innovative route to develop upconversion, crystalline, and temperature sensing material. Here, we deigned ultrasonic assisted green approach for successful synthesis of β-NaBiF4:Yb3+, Er3+ (size ∼25–100 nm) using Tabernaemontana divaricata leaves extract without any surfactant. Characterization techniques such as XRD, SEM, TEM, XPS, EDX, and PL unveiled its properties. Green and red upconversion emissions (λex = 980 nm) were two-photon absorption process. The possible energy transfer and thermal quenching mechanism is discussed. Using thermally coupled levels (2H11/2 and 4S3/2) of Er3+, FIR based temperature sensing revealed ΔE ∼841 cm−1, linear response (R2 ∼0.99), outstanding relative sensitivity (Sr max∼ 1.4 % K−1 @294 K), good absolute sensitivity (Sa max∼ 0.29 %K−1 @ 398 K) and a low temperature resolution (δTmin = 0.35 K) over temperature range 294–398 K.

Reduced processing efficiency impacts auditory detection of amplitude modulation in children: Evidence from an experimental and modeling study

Auditory detection of the Amplitude Modulation (AM) of sounds, crucial for speech perception, improves until 10 years of age. This protracted development may not only be explained by sensory maturation, but also by improvements in processing efficiency: the ability to make efficient use of available sensory information. This hypothesis was tested behaviorally on 86 6-to-9-year-olds and 15 adults using AM-detection tasks assessing absolute sensitivity, masking, and response consistency in the AM domain. Absolute sensitivity was estimated by the detection thresholds of a sinusoidal AM applied to a pure-tone carrier; AM masking was estimated as the elevation of AM-detection thresholds produced when replacing the pure-tone carrier by a narrowband noise; response consistency was estimated using a double-pass paradigm where the same set of stimuli was presented twice. Results showed that AM sensitivity improved from childhood to adulthood, but did not change between 6 and 9 years. AM masking did not change with age, suggesting that the selectivity of perceptual AM filters was adult-like by 6 years. However, response consistency increased developmentally, supporting the hypothesis of reduced processing efficiency in early childhood. At the group level, double-pass data of children and adults were well simulated by a model of the human auditory system assuming a higher level of internal noise for children. At the individual level, for both children and adults, double-pass data were better simulated when assuming a sub-optimal decision strategy in addition to differences in internal noise. In conclusion, processing efficiency for AM detection is reduced in childhood. Moreover, worse AM detection was linked to both systematic and stochastic inefficiencies, in both children and adults.