Relative Sensitivity Values Research Articles

Soil and Water Assessment Tool (SWAT) model for hydrological response analysis in the Gajahwong subwatershed, Yogyakarta, Indonesia

Hydrological response is a specific reaction of a watershed to rainfall, and one form is surface runoff, which can be influenced by climatic and physiographic factors. These factors are represented by various parameters that have their own impact on surface runoff, otherwise known as parameter sensitivity. The purpose of this study was to identify the hydrological response in the form of flow discharge based on the application of the Soil and Water Assessment Tool (SWAT) model and to identify the sensitivity of parameters that affect the hydrological response in the Gajahwong subwatershed. The data used in this study came from secondary data obtained from relevant agencies and primary data collected through sampling and laboratory testing. Flow discharge modeling was carried out using SWAT+ software, and the modeling results were automatically calibrated and validated using statistical tests. Meanwhile, sensitivity analysis was conducted by calculating the relative sensitivity values. The results showed that the flow discharge modeling of the Gajahwong subwatershed exhibited a pattern that is similar to the observed discharge. Based on this finding and the validation results with statistical tests, it can be said that the SWAT model can model and predict the flow discharge in the watershed quite well. The input parameter that is very sensitive and has a significant influence on the hydrological response in the subwatershed is the curve number (cn2), with a relative sensitivity value of 1.12.

Temperature Dependent Photoluminescence Properties of a Y2Ge2O7:Tb3+ phosphors. A dual band ratiometric luminescent thermometer

A series of green light emitting Y2Ge2O7:xTb3+ phosphors (x = 0.2, 0.5, 1.0, 2.0 and 4.0mol%) were obtained via the solid-state reaction method. The single phase was confirmed by XRD technique. The photoluminescence (PL) excitation spectrum, emission spectra at room and as a function of temperature, decay curves of phosphors were studied in detail. The emission spectra show typical emissions of Tb3+ ions, whose relative intensities change with the ion concentration or UV excitation. A shift of the CIE chromaticity coordinates from blueish to green region was observed. The emission decay curves are compatible with a single type of Tb3+ activator. The obtained internal Quantum Yield (iQY) increase with the terbium concentration, up to 10.0% for sample with 4.0mol%. In addition, the relative sensitivity values (Sr) for samples with 1.0 and 2.0mol% reached 0.97 and 2.02%K-1, respectively. These high thermal sensitivities obtained, in comparison with other Tb3+ based optical temperature sensors, in biophysical temperature range (30–45 °C), illustrates the potential use of Y2Ge2O7:xTb3+ phosphors in the design of efficient FIR luminescent thermometers for biological systems or other industrial applications.

Blue light excitable efficient down-conversion photoluminescence of Yb3+ and Er3+ in ultra-wide NIR region via Cr3+-Yb3+-Er3+ energy transfer in KAlP2O7 and multifunctional applications

Broadband near-infrared (NIR) phosphors have gained growing interest in applications such as food detection, plant growth and night vision lighting. However, designing NIR phosphors with large full width at half maximum (FWHM) is challenging. In this study, we introduce a novel blue light excitable Cr3+-Yb3+-Er3+ tri-doped KAlP2O7 (KAPO) phosphor, which exhibits luminescence in ultra-wide NIR region, including broadband NIR-II luminescence with the FWHM of 302nm and sharp NIR-III luminescence at 1538nm. Fluorescence decay curves confirmed the presence of energy transfer. In addition, the NIR optical thermometry was developed using the non-thermally coupled energy states of 4T2→4A2 (Cr3+) and 4I13/2→4I15/2 (Er3+), with the highest absolute (SA) and relative sensitivity (SR) values determined to be 122.2 × 10−4 K−1 (T = 473K) and 0.76% K−1 (T = 448K), respectively. In addition,the prepared phosphor can be efficiently excited by various wavelengths including 377nm ultraviolet light, 468nm blue light, and 808/980nm near infrared light, suggesting its promising applications in anti-counterfeiting. The NIR phosphor-converted LED (pc-LED) was fabricated using KAPO: 0.01Cr3+, 0.002Yb3+, 0.01Er3+ phosphor and a 470nm LED chip, demonstrating notable potential in night vision technology.

Structure regulation and luminescence improvement of Gd3Ga5O12:Cr3+: An anti-thermal quenching NIR phosphor for multifunctional applications

Near-infrared (NIR) phosphors converted light emitting diodes (LEDs) are booming as next NIR light sources. But the quantum efficiency and thermal stability of the NIR phosphors need to be improved. Here, thermally stable garnet Gd3Ga5O12 is selected as the matrix and Cr3+ as the luminescent center to obtain Gd3Ga5O12:Cr3+ NIR phosphor. Equivalent smaller Lu3+ was adopted to regulate the structure of Gd3Ga5O12 to further improve the luminescence performance. By regulating the structure the emission spectra shift toward blue region and the intensity is improved. Optimized GdLu2Ga5O12:Cr3+ exhibits anti-thermal quenching behavior and the internal quantum efficiency reaches 73.69 %. Relative sensitivity value of the phosphor GdLu2Ga5O12:Cr3+ reaches 3.353 % K−1 at 423 K based on lifetime mode. LED device is fabricated by combining the phosphor GdLu2Ga5O12:Cr3+ and the commercial red phosphor with blue chip. Electroluminescence spectrum can cover the absorption spectra of the plant dyes well. The lettuce grow faster by adopting this LED device as compensating light source. This work provides an anti-thermal quenching NIR phosphor for multiple applications.

Multicolor and multimode luminescent lanthanide-doped Cs2NaInCl6:Sb3+ from visible to near infrared for versatile applications

Double halide perovskites have shown admirable potential in promising optoelectronic applications due to simple synthesis, good stability and high structural tolerance. However, the poor optical properties caused by the parity-forbidden transitions posts a stringent limitation on their potential applications. Herein, we dope the lanthanide (Ln3+) ions with abundant energy levels into the Cs2NaInCl6:Sb3+ single crystals, which not only achieve multicolor visible emissions spectra from blue to red light, but also expand to the near infrared region from 800 to 1900 nm. In addition, the phosphors enable the multimode emissions with the up-conversion and down-conversion photoluminescence. Intriguingly, the excitation source, and the excitation light intensity also endow the multicolor emissions. Thus, combining with the multicolor and multimode luminescent properties, Cs2NaInCl6:Sb3+/Ln3+ could be applied to night vision imaging, substance detection, optical thermometry, white-light-emitting diodes (WLEDs) and anti-counterfeiting. The maximum value of relative temperature sensitivity reaches as high as 1.207 % K−1, which is relatively higher than those of most metal halide perovskites. Moreover, the single-source WLED displays Commission Internationale de L'Eclairage color coordinates (0.32, 0.31), a correlated color temperature of 6673 K, and color rendering index of 81.7. These results demonstrate the potential applications in the multifunctional photoelectric applications.

Divalent tin activator for Nd3+/Yb3+ emission in lanthanum borate glass and its impact on inter-ionic phenomena and thermometry

The co-existence of divalent tin activator and Nd3+/Yb3+ rare earths in the borate glasses were utilized and examined to achieve the effective enhancement of the useful near-infrared emission in the wide spectral region. The UV Sn2+ excitation is extremely relevant for the effectiveness of both (Nd,Yb) near-infrared emission, however, Sn-Nd energy transfer efficiency is particularly prominent. The different advantageous inter-ionic phenomena made it possible to explore the diverse energy transfer routes leading to the population of the relevant ytterbium and neodymium excited states. Consequently, adequate multi-model temperature sensing can be proposed and verified considering single-doped and co-doped borate glass systems. The dissimilar effect of temperature on the complementary Sn2+, Nd3+ and Yb3+ optical transitions was investigated in detail. Employing the temperature-dependent spectra of optically active ions, high values of temperature relative sensitivity (1.3 % K−1) were estimated especially in the physiological range (30 – 75 ⁰C).

Structure-Dopant Concentration Relations in Europium-Doped Yttrium Molybdate and Peak-Sharpening for Luminescence Temperature Sensing.

A set of Eu3+-doped molybdates, Y2-xEuxMo3O12 (x = 0.04; 0.16; 0.2; 0.4; 0.8; 1; 1.6; 2), was synthesized using a solid-state technique and their properties studied as a function of Eu3+ concentration. X-ray diffraction showed that the replacement of Y3+ with larger Eu3+ resulted in a transformation from orthorhombic (low doping concentrations) through tetragonal (high doping concentrations), reaching monoclinic structure for full replacement in Eu2Mo3O12. The intensity of typical Eu3+ red emission slightly increases in the orthorhombic structure then rises significantly with dopant concentration and has the highest value for the tetragonal Y2Mo3O12:80mol% Eu3+. Further, the complete substitution of Y3+ with Eu3+ in the case of monoclinic Eu2Mo3O12 leads to decreased emission intensity. Lifetime follows a similar trend; it is lower in the orthorhombic structure, reaching slightly higher values for the tetragonal structure and showing a strong decrease for monoclinic Eu2Mo3O12. Temperature-sensing properties of the sample with the highest red Eu3+ emission, Y2Mo3O12:80mol% Eu3+, were analyzed by the luminescence intensity ratio method. For the first time, the peak-sharpening algorithm was employed to separate overlapping peaks in luminescence thermometry, in contrast to the peak deconvolution method. The Sr (relative sensitivity) value of 2.8 % K-1 was obtained at room temperature.

Highly sensitive dual-mode temperature measurement utilizing completely opposite thermal quenching luminescence

In recent years, phosphors have been used in the field of temperature sensing, which has aroused great interest because of its advantages of quick response, high sensitivity and high accuracy. However, exploring optical thermometers with ultra-high sensitivity remains a challenge. In this work, we have designed and synthesized Sm3+ and Mn4+ co-doped La3Mg2NbO9 phosphor for temperature sensing for the first time by utilizing the anomalous thermal quenching property of Sm3+ ions and the sensitive thermal quenching property of Mn4+ ions. Furthermore, the structure, elemental distribution, morphology and optical characteristics of La3Mg2NbO9:Sm3+,Mn4+ were studied in detail. Benefiting from the different responses of the Sm3+ and Mn4+ ions to temperature, the fluorescence intensity ratios of Sm3+ to Mn4+ in La3Mg2NbO9 samples show excellent optical thermometry performance in the range of 303–463 K. The maximum absolute sensitivity (Sa) and relative sensitivity (Sr) values of La3Mg2NbO9:Sm3+,Mn4+ sample reach as high as 0.117 K-1 (@463 K) and 4.48 % K−1 (@303 K), respectively. Furthermore, the maximum of Sa is 0.385 K−1 (@463 K) and the maximum of Sr is 4.54 % K−1 (@303 K) based on the fluorescence lifetime temperature measurement method. The temperature cyclotron curve of the sample proves that the sample has excellent stability and repeatability in temperature measurement. These results demonstrate that the designed La3Mg2NbO9:Sm3+,Mn4+ phosphor is promising for the field of non-contact optical temperature thermometry.

Optical properties of La2MgSnO6: Eu3+/Mn4+ double-perovskite phosphors for multifunctional applications

A series of Eu3+/Mn4+ doped La2MgSnO6 double-perovskite phosphors were successfully synthesized by solid-state method. The crystal structure, optical properties, and temperature sensitivity of the phosphors were investigated systematically. Under excitation at 310 and 394 nm, the La2MgSnO6: Eu3+, Mn4+ phosphor exhibits intense red emission of Mn4+ (2Eg→4A2g) and orange-red emission of Eu3+ (5D0→7F2). Within the temperature range of 298–473 K, Eu3+ exhibits excellent thermal stability, whereas the Mn4+ shows significant thermal quenching behavior. A luminescence thermometer for dual-wavelength operation with high sensitivity was designed based on the fluorescence intensity ratio (FIR) method. The value of maximum relative sensitivity (Sr) was calculated as 1.58 % K−1 at 423 K. Particularly, the wavelength-dependent of La2MgSnO6: Eu3+, Mn4+ phosphor was investigated over a range of 270–340 nm, revealing promising potential with a remarkably high maximum wavelength sensitivity of 18.2 % nm−1 at 300 nm. Subsequently, a prototype LED device was fabricated by integrating the La2MgSnO6: Eu3+, Mn4+ phosphors and a near-UV LED chip, demonstrating significant spectral overlap with the absorption curves of plant pigments. These results suggest that the La2MgSnO6: Eu3+, Mn4+ multifunctional phosphor has promising applications in optical thermometry, wavelength detection, and promoting plant growth.

A novel multifunctional Eu3+/Mn4+ co-doping double perovskite phosphor for applications in LEDs and optical thermometry

In recent years, phosphors have played important roles in solid-state lighting, plant growth lighting and optical temperature measurement. In this work, novel La3Mg2NbO9:Eu3+,Mn4+ phosphors were successfully prepared by the high temperature solid phase method and innovative multimode applications were investigated in optical thermometry, plant growth and White-LEDs. The crystal structure, surface morphology, photoluminescence, temperature sensing properties and luminescence mechanism of La3Mg2NbO9:Eu3+,Mn4+ phosphors were investigated in detail. Benefiting from the different responses of Eu3+ and Mn4+ ions to temperature, the La3Mg2NbO9:0.06Eu3+,0.0095Mn4+ sample shows excellent optical thermometry performance in the range of 303 ∼ 478 K. The maximum values of relative sensitivity (Sr) reach 2.7 % K-1 (@478 K) according to the fluorescence intensity ratio method and the maximum of Sr is 5.2 % K−1 (@428 K) based on the fluorescence lifetime method. Furthermore, the electrochromic spectrum of the red pc-LED prepared using La3Mg2NbO9:0.06Eu3+,0.005Mn4+ phosphor perfectly overlapped with the absorption bands of the photosensitive pigments for planting, and another white pc-LED prepared using La3Mg2NbO9:0.06Eu3+,0.0025Mn4+ phosphor emitted bright white light with a color rendering index of 89.8, color coordinate of (0.3468, 0.3557) and correlated color temperature of 4945 K. All the results demonstrate that the La3Mg2NbO9:Eu3+,Mn4+phosphors are promising for the field of non-contact optical temperature thermometry, plant lighting lamps and pc-LED backlit displays.

NIR-II luminescence and temperature sensing properties based on double perovskite La2MgTiO6: Yb3+/Er3+/Ho3+ phosphor

The near-infrared-II (NIR-II) fluorescence thermometer based on rare earth-doped double perovskite is rarely. Herein, Er3+-Ho3+ and Yb3+ co-doped lead-free double perovskite La2MgTiO6 (LMTO) phosphors were synthesized by a conventional high temperature solid phase method. The phase purity and morphology of the samples were analyzed using XRD and FE-SEM. The NIR-II luminescence properties of LMTO: Er3+-Ho3+-Yb3+ phosphors were systematically investigated under laser irradiation at 980 nm. A NIR-II fluorescence thermometer was also designed based on non-thermal coupled energy levels originated from the 4I13/2 energy level of Er3+ and the 5I6 energy level of Ho3+. The maximum value of relative sensitivity (Sr) was 0.54 % at 513 K. Compared to visible thermometers (LMTO: Er3+-Yb3+ and LMTO: Ho3+-Yb3+), the NIR-II thermometers offer better temperature measurement capability and penetration depth. All the experimental results show that the NIR-II thermometer with a wider range and higher sensitivity has been realized, which puts forward a new idea for the design and optimization of NIR-II thermometers.

Sb3+ and Er3+ co-doped Cs2NaYCl6 double perovskite with ultra-high sensitivity for optical thermometry

Optical thermometry has attracted great attention because it enables accurate temperature measurement in harsh environments due to non-contact temperature measurement. Three-dimensional (3D) lead-free halide perovskites have a great application potential in this field, due to its outstanding luminous properties and stability. In this work, the Sb3+ and Er3+ are introduced in Cs2NaYCl6 double perovskites (DPs). The Sb3+ doping Cs2NaYCl6 DPs exhibits bright blue emission from the Sb3+ activated self-trapped excitons (STEs) and Sb3+,Er3+ co-doped Cs2NaYCl6 has efficient green emission with excellent photoluminescence quantum yields (PLQY) of 81.1% because of the presence of energy transfer from self-trapped excitons to Er3+ ions. Excitingly, the ratio between the fluorescence intensity at 524 nm and 550 nm (FIR(I524 nm/I550 nm)) and the ratio between the fluorescence intensity at 524 and 456 nm (FIR(I524 nm/I456 nm)) both have a high correlation with temperature in the range of 298–473 K. The maximum of relative sensitivity values reach to 1.18%/K (I524 nm/I550 nm) and 1.19%/K (I524 nm/I456 nm) at 298 K, respectively. The outstanding temperature sensitivity suggests that the Sb3+,Er3+ co-doped Cs2NaYCl6 has enormous application potential in ratiometric optical thermometry.

Na5Y9F32:Yb3+/Ho3+/Tm3+ up-conversion luminescent single crystals for highly sensitive optical temperature sensor

A novel non-contact optical temperature sensor with excellent performance of its adequate temperature resolution (δ(T) = 0.017 K) and exceptional relative thermal sensitivity (Sr = 1.97% K−1) was developed based on the up-conversion fluorescence intensity ratio (FIR) of Ho3+/Tm3+/Yb3+ triply incorporated Na5Y9F32 single crystal grown by Bridgman method. The up-conversion (UC) emission bands at 482 nm/669 nm/700 nm of Tm3+ and 522 nm/542 nm/653 nm of Ho3+ ions were observed upon excitation of 980 nm. The effects of Yb3+ concentration from 0.5 to 4 mol% on the UC emission of the Ho3+/ Tm3+ fixed doped Na5Y9F32 single crystal were also carried out. It has been demonstrated through the calculation of the steady-state rate equation that the intensity of UC emission is linearly heightened with the pump power, confirming the conversion mechanism. The temperature sensing performance of the Ho3+/Tm3+/Yb3+ incorporated Na5Y9F32 single crystals was explored by analyzing the FIR employing thermally coupled energy levels (TCLs) and non-thermally coupled energy levels (NTCLs). The maximum values of absolute sensitivity (Sa) and relative sensitivity (Sr) of the material are estimated to be 19.1% K−1 (323 K) and 1.97% K−1 (398 K), separately, which are far higher than those of previously reported RE3+-doped UC optical temperature sensor materials. This study shows that the transparent single crystal has the great potential as a non-contact optical thermometer, and provides a new idea for studying other highly optical sensing materials.

Upconversion luminescence and temperature sensing properties of Tm3+, Yb3+, and Ho3+ doped 12CaO·7Al2O3 single crystals

Tm3+, Yb3+, and Ho3+ doped 12CaO·7Al2O3 (C12A7) single crystal exhibiting white light emission has been successfully prepared by the Czochralski method. Under 980 nm excitation, the emission peaks were observed at 475 nm, 550 nm, 653 nm, and 660 nm. As the temperature increased from 403 K to 623 K, the upconversion luminescence color of the Tm3+/Yb3+/Ho3+/C12A7 crystal changed from white to green and exhibited large temperature dependence. In the temperature range of 403K-623 K, the absolute sensitivity (SA) value of the thermal coupling levels (TCLs) fluorescence intensity ratio (FIR, I700/I800) was 1.48×10−5K−1, and the relative sensitivity (SR) value was 7.13×10−3%K−1. The non-thermal coupling levels (NTCLs) FIR (I800/I870) had an SA value of 0.026K−1 and an SR value of 0.014%K−1, which achieved a significant increase in temperature sensitivity compared to the former. It provides a strategy to achieve accurate sensitivity of FIR technology. Rare earth (RE) ions doped C12A7 single crystal material has good research and application prospects in the field of temperature sensing and optoelectronics.

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.

Two-Dimensional Hybrid Perovskite with High-Sensitivity Optical Thermometry Sensors.

Optical thermometry has gained significant attention due to its remarkable sensitivity and noninvasive, rapid response to temperature changes. However, achieving both high absolute and relative temperature sensitivity in two-dimensional perovskites presents a substantial challenge. Here, we propose a novel approach to address this issue by designing and synthesizing a new narrow-band blue light-emitting two-dimensional perovskite named (C8H12NO2)2PbBr4 using a straightforward solution-based method. Under excitation of near-ultraviolet light, (C8H12NO2)2PbBr4 shows an ultranarrow emission band with the full width at half-maximum (FWHM) of only 19 nm. Furthermore, its luminescence property can be efficiently tuned by incorporating energy transfer from host excitons to Mn2+. This energy transfer leads to dual emission, encompassing both blue and orange emissions, with an impressive energy transfer efficiency of 38.3%. Additionally, we investigated the temperature-dependent fluorescence intensity ratio between blue emission of (C8H12NO2)2PbBr4 and orange emission of Mn2+. Remarkably, (C8H12NO2)2PbBr4:Mn2+ exhibited maximum absolute sensitivity and relative sensitivity values of 0.055 K-1 and 3.207% K-1, respectively, within the temperature range of 80-360 K. This work highlights the potential of (C8H12NO2)2PbBr4:Mn2+ as a promising candidate for optical thermometry sensor application. Moreover, our findings provide valuable insights into the design of narrow-band blue light-emitting perovskites, enabling the achievement of single-component dual emission in optical thermometry sensors.

Ratiometric dual-emitting thermometers based on rhodamine B dye-incorporated (nano) curcumin periodic mesoporous organosilicas for bioapplications.

This study explores the potential of combining periodic mesoporous organosilicas (PMOs) with a fluorescent dye to develop a ratiometric thermometry system with enhanced stability, sensitivity, and biocompatibility. PMOs, ordered porous materials known for their stability and versatility, serve as an ideal platform. Curcumin, a natural polyphenol and fluorescent dye, is incorporated into PMOs to develop curcumin-functionalized PMOs (C-PMO) and curcumin-pyrazole-functionalized PMOs (CP-PMO) via hydrolysis and co-condensation. These PMOs exhibit temperature-dependent fluorescence properties. The next step involves encapsulating rhodamine B (RhB) dye within the PMO pores to create dual-emitting PMO@dye nanocomposites, followed by a lipid bilayer (LB) coating to enhance biocompatibility and dye retention. Remarkably, within the physiological temperature range, C-PMO@RhB@LB and CP-PMO@RhB@LB demonstrate noteworthy maximum relative sensitivity (Sr) values of up to 1.69 and 2.60% K-1, respectively. This approach offers versatile means to create various ratiometric thermometers by incorporating different fluorescent dyes, holding promise for future temperature sensing applications.

Advanced temperature sensing with Er3+/Yb3+ co-doped Ba2GdV3O11 phosphors through upconversion luminescence.

Optical thermometry is a non-contact temperature sensing technique with widespread applications. It offers precise measurements without physical contact, making it ideal for situations where contact-based methods are impractical. However, improving the accuracy of optical thermometry remains an ongoing challenge. Herein, enhancing the thermometric properties of luminescent thermometers through novel materials or strategies is crucial for developing more precise sensors. Hence, the present study focuses on the application of four-mode luminescence thermometric techniques in sol-gel synthesized Er3+/Yb3+ co-doped Ba2GdV3O11 phosphors for optical temperature sensing in the temperature range of 298-573 K. The upconversion (UC) luminescence is achieved under excitations of 980 nm or 1550 nm, resulting in bright yellow-green emission in the visible spectral range. Temperature sensing is realized by exploiting the UC emissions of 4S3/2, 2H11/2 and 4F7/2 bands, which represent intensity ratios of thermally coupled levels (TCELs) and non-thermally coupled levels (NTCELs) of Er3+/Yb3+, along with the emission lifetimes at 4S3/2. The relative sensitivity (Sr) values for TCELs exhibit a gradual decrease with rising temperature, reaching a maximum of 1.1% K-1 for 980 nm excitation and 0.86% K-1 for 1550 nm excitation at 298 K. Conversely, for NTCELs, the highest Sr value observed is 0.9% K-1 at 298 K for 1550 nm excitation. Moreover, the emission lifetimes at 4S3/2 yield notably high Sr values of up to 5.0% μs K-1 (at 425 K). Furthermore, the studied phosphors have a sub-degree thermal resolution, making them excellent materials for accurate temperature sensing. Overall, this study provides a promising new direction for the development of more precise and reliable optical thermometry techniques, which could have important implications for a range of scientific and industrial optical temperature sensing applications.

Near-infrared to visible up-conversion in Er3+ doped LaAlO3 phosphors and their assessment as an optical temperature sensor

The present work studies the optical temperature sensing in micro and nanospheres of LaAlO3, synthesized by a Pechini sol-gel method. The optical properties focus on the up-conversion emission and optical temperature sensing properties of thermally and non-thermally coupled levels. Exciting at 975 nm, the up-conversion produces three emissions bands centered at 533, 545, and 670 nm. When the concentration of Er ion increases, the intensity of emission increases up to 5 %. The mechanism shows the absorption of two photons and the energy transfer up-conversion process. Optical temperature sensing is studied in the range of 299–327 K based on thermal coupled and non-thermal coupled levels by the luminescence intensity ratio technique. The absolute sensitivity, relative sensitivity, and uncertainty temperature values were obtained to study the material's performance and applicability. The maximum absolute and relative sensitivity values are 5.21 × 10−3 K−1 at 327 K for I670/I545 and 0.87 % at 299 K for I533/545. On the other hand, the temperature uncertainty is 0.2 K, indicating that the present material may be used as an effective temperature-sensing device using thermal coupled and non-thermal coupled levels.

Effect of the synthesis route on luminescence dynamics and thermographic properties of Sm3+ doped Ba2Mg(PO4)2 phosphor

The present study investigates the impact of synthesis routes on the structure, optical, and thermographic properties of Ba2Mg(PO4)2:xSm3+ (x = 2 mol.%) phosphor. The two techniques used for the synthesis were combustion synthesis (CS) and solid-state reaction synthesis (SSR). X-ray diffraction analysis confirmed a pure monoclinic phase with space group P21/n in both SSR and CS synthesized samples. The average crystallite size was 41 ± 0.19 nm for SSR and 21 ± 0.02 nm for CS phosphors. Using Fourier transform infrared (FTIR) analysis, the vibrational behavior of both synthesized phosphor samples was analyzed. Both samples displayed a bright orange-red photoluminescence (PL) emission, attributed to the 4G5/2→6H7/2 transition when excited with 403 nm light at room temperature. However, the intensity of PL emission was higher in the CS-prepared sample. The UV-Vis absorption measurements indicated several bands in both samples. The CIE coordinates were calculated for both samples and they corresponded to the shade of orange-red emission of the Sm3+ ions. The study also included an investigation into the temperature-sensing characteristics of the synthesized phosphors, which was performed in the 323–673 K temperature range. The fluorescence intensity ratio (FIR) technique was used to study the non-contact temperature sensing for both samples, and the CS-prepared phosphors exhibited the maximum value of absolute sensitivity (0.00629 K−1) and relative sensitivity (0.26 % K−1) at temperature 673 K. Overall, the results indicate that the CS method provides better results in terms of luminescence and temperature sensing characteristics compared to the SSR method.