High Absolute Sensitivity Research Articles

Upconversion photoluminescence and optical thermometry properties of Gd3BWO9: Yb3+, Ho3+ with high absolute sensitivity

Optical temperature sensing has attracted significant attention owing to its unique characteristics of rapid response, non-contact detection, high resolution and high sensitivity. In this study, a series of Gd3BWO9: Yb3+, Ho3+ upconversion phosphors were synthesized by solid-state synthesis, and the optimal sample was Gd3BWO9: 0.32 Yb3+, 0.003Ho3+. The upconversion emission spectrum was measured under the excitation of 980 nm laser, and the emission peaks in the bands of 528–560 nm and 630–680 nm corresponded to the green emission (5F4/5S2→5I8) and red emission (5F5/→5I8) of Ho3+. The SR and SA of Gd3BWO9:0.32 Yb3+, 0.003Ho3+ in the range of 300 K–625 K were calculated. At 300 K, both the relative sensitivity SR and the absolute sensitivity SA reached their maximum values, which are SR(max) = 0.73 % K−1 and SA(max) = 0.0508 K-1, respectively. The Gd3BWO9: 0.32 Yb3+, 0.003Ho3+ phosphor has a very high absolute sensitivity, and hold great application potential in optical temperature sensing.

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.

In-band luminescence thermometry in the third biological window and multicolor emission of Er-doped fluoride and oxide nanoparticles

In this study we present a morphological and spectroscopical characterization of three different erbium doped nanocrystal samples, namely two oxides (Y2O3:3%Er, Sc2O3:3%Er) and one fluoride (YF3:5%Er). The spectroscopic study offers a comprehensive comparison of their multicolor emissions, ranging from the visible to the mid-infrared region. Emissions from the first five excited states are presented and the emission cross sections of the 4I11/2 → 4I15/2, 4I11/2 → 4I13/2, and 4I13/2 → 4I15/2 transitions have been calculated and compared with literature results for the oxide compounds providing a confirmation for the 1.5 μm emission of Er:Y2O3, a correction over published values for the 2.7 μm emission of Er:Y2O3, and also new results for the Er:Sc2O3 emission cross section values of all the infrared bands. Moreover, this study explores the application of the 4I13/2 emission for in-band luminescence thermometry within the third biological window. An optimized segmentation of the 1.5 μm emission permits to achieve high relative and absolute sensitivities using just one dopant ion.

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.

Energy-splitting from persistent luminescence nanoparticles with trivalent Cr ions for ratiometric temperature sensing.

MgGa2O4 (MGO) with the spinel structure exhibits abundance defects and could achieve the modulation of emission by ion doping as persistent luminescence nanoparticles (PLNPs). Here, we introduced Cr3+ ions into MGO to achieve near-infrared (NIR) emission, and Pr3+ ions to tune the lattice environment for enhanced NIR emission. The optimal composite, MgGa2O4: 0.005Cr3+, 0.003Pr3+ (MGCP), achieved enhanced NIR emission at 709 nm under 222 nm excitation. The concentration quenching was observed due to electric dipole-quadrupole interaction at high Cr3+ and Pr3+ content. The afterglow mechanism was revealed, while the energy-splitting occurs from trivalent Cr3+ ions at 650 and 709 nm, thanks to the complex lattice environment. We observed that the emission at 709 nm decreased, while the satellite signal at 650 nm increased first and then decreased intensity with increasing temperature, due to the intervalence charge transfer for Cr3+ ions at 303-528 K. Ratiometric temperature sensing was therefore realized with superb linearity, high absolute sensitivity at 303 K for 4.18%, and accuracy at 528 K for 2.62 K, confirming with the luminescence intensity ratio at 709 and 650 nm under excitation at 222 nm. Thus, we provide a method with energy-splitting emission of Cr3+ ions to design temperature sensing.

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.

Development of a Swedish short version of the Montreal Cognitive Assessment for cognitive screening in patients with stroke.

The primary objective was to develop a Swedish short version of the Montreal Cognitive Assessment (s-MoCA-SWE) for use with patients with stroke. Secondary objectives were to identify an optimal cut-off value for the s-MoCA-SWE to screen for cognitive impairment and to compare its sensitivity with that of previously developed short forms of the Montreal Cognitive Assessment. Cross-sectional study. Patients admitted to stroke and rehabilitation units in hospitals across Sweden. Cognition was screened using the Montreal Cognitive Assessment. Working versions of the s-MoCA-SWE were developed using supervised and unsupervised algorithms. Data from 3,276 patients were analysed (40% female, mean age 71.5 years, 56% minor stroke at admission). The suggested s-MoCA-SWE comprised delayed recall, visuospatial/executive function, serial 7, fluency, and abstraction. The aggregated scores ranged from 0 to 16. A threshold for impaired cognition ≤ 12 had a sensitivity of 97.41 (95% confidence interval, 96.64-98.03) and positive predictive value of 90.30 (95% confidence interval 89.23-91.27). The s-MoCA-SWE had a higher absolute sensitivity than that of other short forms. The s-MoCA-SWE (threshold ≤ 12) can detect post-stroke cognitive issues. The high sensitivity makes it a potentially useful "rule-out" tool that may eliminate severe cognitive impairment in people with stoke.

Evaluation of Satellite Precipitation Products for Estimation of Floods in Data-Scarce Environment

Utilization of satellite precipitation products (SPPs) for reliable flood modeling has become a necessity due to the scarcity of conventional gauging systems. Three high-resolution SPPs, i.e., Integrated Multi-satellite Retrieval for GPM (IMERG), Global Satellite Mapping of Precipitation (GSMaP), and Climate Hazards Group InfraRed Precipitation with Station (CHIRPS), data were assessed statistically and hydrologically in the sparsely gauged Chenab River basin of Pakistan. The consistency of rain gauge data was assessed by the double mass curve (DMC). The statistical metrics applied were probability of detection (POD), critical success index (CSI), false alarm ratio (FAR), correlation coefficient (CC), root mean square error (RMSE), and bias (B). The hydrologic evaluation was conducted with calibration and validation scenarios for the monsoon flooding season using the Integrated Flood Analysis System (IFAS) and flow duration curve (FDC). Sensitivity analysis was conducted using ±20% calibrating parameters. The rain gauge data have been found to be consistent with the higher coefficient of determination (R2). The mean skill scores of GSMaP were superior to those of CHIRPS and IMERG. More bias was observed during the monsoon than during western disturbances. The most sensitive parameter was the base flow coefficient (AGD), with a high mean absolute sensitivity index value. During model calibration, good values of performance indicators, i.e., R2, Nash−Sutcliffe efficiency (NSE), and percentage bias (PBIAS), were found for the used SPPs. For validation, GSMaP performed better with comparatively higher values of R2 and NSE and a lower value of PBIAS. The FDC exhibited SPPs’ excellent performance during 20% to 40% exceedance time.

An efficient construction model of multi-fluorescence morphologies in oxyfluoride matrix

As the most common up-conversion (UC) activation center now, Er3+ can emit the blue, green and red light under the excitation of 980 nm. It has important meaning how to manipulate the emission wavelength in practical application. In our work, a series of excellent UC luminescence materials Y6O5F8: M3+ (M = Yb, Er, and Fe) are synthesized by the hydrothermal method. Under the condition of different pH, the prepared precursors exhibited different phases of YF3 and Y(OH)1.63F1.37 and various morphologies. The hydrogen bond guides a regular crystal growth process. With the change of pH, OH group could be selectively introduced into the host during this different crystal growth process. The structure change is likely to decrease the rigidity of this lattice and adjusted the cut-off phonon energies, and further influence the f-f transition of Er3+, selectively forming red emission in Y6O5F8: Yb3+, Er3+. The intensity of red UC luminescence is enhanced by 22 times via Fe3+ co-doping into the Y6O5F8: Yb3+, Er3+ crystalline lattice. The introduction of transition metal ions Fe3+, produces an excellent energy transfer from <2F7/2, 4T1g> (Yb3+-Fe3+ dimer) to energy levels of Er3+ as well as the distortion of the crystalline field symmetry. In addition to the enhancing luminescence effect, Fe ions also introduce magnetism from the hysteresis loop curve. The temperature-dependent UC emission of Y6O5F8: Yb3+, Er3+, Fe3+ display significant thermal coupling occurs with a higher absolute sensitivity. Based on this, the anti-fake and temperature-sensitive luminescent applications of this material are investigated in detail.

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.

Crystal formation in Eu3+ - Doped oxyfluorophosphate glass-ceramics for luminescence thermometry

Eu3+ doped-Oxyfluorophosphate glasses with a general composition 75 NaPO3 - (25-x) CaO – x CaF2 (with x ranging from 0 to 25 mol%) were prepared and their spectroscopic changes induced by the addition of fluorine and when applying a thermal treatment in order to grow crystals in the glasses were investigated. The addition of CaF2 at the expense of CaO reduces Ω2 and Ω4 parameters indicating that the Eu3+ ions are located in less covalent and well separated sites in oxyfluorophosphate glasses. An increase in the CaF2 content at the expense of CaO also leads to an increase in the absolute thermometric sensitivity from (4.2 × 10−4) K−1 to (17.6 × 10−4) K−1 at 523 K while decreasing the relative thermometric sensitivity from 3.0% to 1.4%.The heat treatment leads to the precipitation of crystals, the composition of crystal phase depends on the glass composition. For the glasses with x = 0 and 10, the thermal treatment increases Ω6 while reducing Ω4, as a result of an enhanced stiffness and reduced covalency of dopant's environment due to the precipitation of various crystals. As Ω2 remains unchanged, the Eu3+ are suspected to remain mainly in the amorphous part of the glass-ceramics in agreement with the lack of sharp peaks in the emission spectrum. For the glasses with x = 20 and 25, Ω2 increases indicating a change in the site symmetry of Eu3+ resulting from the dopant entering the CaF2 crystalline phase. Due to the changes in the Eu3+ sites in the heat treated glasses, the heat treatment of the glass increases the absolute thermal sensitivity, but reduces the relative thermal sensitivity. The oxyfluorophosphate glass-ceramic with x = 25 exhibits high absolute thermometric sensitivity compared to oxyfluorophosphate glass, but also comparatively low relative sensitivity of 0.5% K−1.

Exploring the excitation spectrum behavior of Dy in CaWO4 for a new excited-state-based ratiometric thermometry

Exploring excited-state transition behavior is of great importance for understanding the optical characteristics of lanthanide ions, which may potentially develop new optical thermometry by the thermally affected excitation processes. In this work, we explore the detailed excitation transition behaviors of Dy3+ and propose a new thermometry strategy based on excited-state absorption intensity ratio (EIR) in Dy3+ doped CaWO4 phosphors. The optimal Dy3+ doping concentration in CaWO4:Dy phosphors was determined and its fine excitation transition lines from low-lying levels of 6HJ (J = 15/2, 13/2, 11/2, and 9/2) to the respective high-lying levels of Dy3+ ions were identified by well-resolving the photoluminescence excitation (PLE) spectra. By taking advantage of the opposite trends of temperature-dependent PLE intensities of Dy3+, a new ratiometric thermometry based on the EIR of Dy3+ was proposed to be independent of the excitation wavelength and only excitation peak intensities required, with the merit of high absolute and relative sensitivities, excellent repeatability and reusability, good excitation wavelength selectivity. These findings demonstrated an effective strategy for developing a Dy3+-based EIR luminescent thermometer, as well as the enormous potential of Dy3+ doped CaWO4 phosphors in temperature sensing.

Unveiling the thermometric sensitivity of Eu3+ doped glasses in various system from theory to experimental

The thermometric sensitivity of the glasses in different Eu3+ doped glasses in different glass systems with different phonon energies and structures was obtained theoretically using the Judd-Ofelt parameters and compared to the experimental data obtained from the temperature dependent emission spectra. The purpose of the study was to test the limits of thermal sensitivity estimation from the Judd-Ofelt parameters in a wide selection of glass systems. We show, for the first time, the discrepancies in the theoretical and experimental values for the germanate and tellurite glasses due to their low phonon energies which cause the Boltzmann model to fail. The phosphate glasses, due to their high absolute thermometric sensitivity, are the promising materials as luminescence thermometer.

Impact of AgNPs on the optical thermometry and stability of bismuth modified tellurium-tungstate upconverting glass

Bismuth modified Er3+/Yb3+: TeO2-WO3 (TWBi) glass system containing silver metallic nanoparticles have been synthesized via melt-quenching method. Optical absorption spectra have been used for optical bandgap and Judd-Ofelt analysis. Judd-Ofelt intensity parameters show ionic type of bonding between the activator and ligand ions. The HR-TEM analysis of the glass containing silver confirms the presence of silver metallic nano-particles (AgNPs) with average particle size ∼ 42 nm at 30 h heat-treatment. The improvement observed in the UC emission intensity of Er3+ ions has been elucidated by considering the energy transfer processes and crystal field modification. Temperature sensing ability and luminescence stability of Er3+/Yb3+: TWBi glass have been explored with and without the incorporation of AgNPs. It has been found that the upconverting glass with AgNPs have high absolute sensitivity, relative sensitivity and luminescence stability with respect to temperature as compared to the upconverting glass without AgNPs.

A highly sensitive blue-LED-excitable self-calibrated luminescent thermometer based on Cr3+/Eu3+ Co-doped Al2W3O12

In this work, Al2W3O12:1%Cr3+,2%Eu3+ with two discriminable dual emissive centers is synthesized. Both Eu3+ and Cr3+ ions can be excited efficiently by 465 nm. Photoluminescence excitation (PLE) spectra and photoluminescence (PL) lifetime indicate that there is no energy transfer (ET) between Eu3+ and Cr3+ ions. It is worth noting that the photothermal stability of Eu3+ ions is much better than that of Cr3+ ions. Specifically, the ratio of ICr/IEu decreases linearly with increasing temperature. Therefore, a blue-LED-excitable luminescent thermometer based on Cr3+/Eu3+ co-doped Al2W3O12 is proposed. This developed self-calibrated luminescent temperature sensor possesses the relatively high absolute and relative sensitivity (0.38 K-1 and 2.9% K−1 respectively) as well as good cycle stability among the previously reported TM/Ln-based luminescent; thermometers. These superior features of the developed self-calibrated luminescent thermometer (SCLT) make it a very promising candidate for temperature sensing applications.

Effects of Yb3+ concentration on up-conversion luminescence and temperature sensing characteristics of Tm3+/Yb3+:Y2O3 phosphors

Y2O3:0.5 mol%Tm3+/x mol%Yb3+(x = 3, 5, 7, 10) luminescent materials have been synthesized by the CO2 laser zone melting method. With 980 nm excitation, the up-conversion luminescence (UCL) emission bands corresponding to 1G4→3H6, 1G4→3F4, 3F2,3→3H6, and 3H4→3H6 transitions of Tm3+ ions were obtained in visible and near-infrared spectral regions, among which the luminescence emitted by 1G4→3H6, 3H4→3H6 transitions shows obvious Stark splitting. Besides, the optimal doping concentration of Yb3+ is 5 mol%. The up-conversion luminescence spectra of Y2O3:0.5 mol%Tm3+/5 mol%Yb3+ were recorded from 224 K to 873 K. The temperature sensing properties of 3F2,3 and 3H4, 1G4(a) and 1G4(b) energy levels of Tm3+ ions were investigated by the luminescence intensity ratio (LIR) method in a wide temperature range, and the possibility of using 3H4(a), 3H4(b) thermally coupled levels (TCLs) of Tm3+ ions for temperature sensing was developed. The results show that 1G4(a) and 1G4(b), 3F2,3 and 3H4, 3H4(a) and 3H4(b) of Tm3+ ions are TCLs, and the Stark sub-levels own relatively high absolute sensitivity at low temperature, whereas the 3F2,3 and 3H4 TCLs of Tm3+ ions are more suitable for high temperature measurement. The results show that the Tm3+/Yb3+:Y2O3 luminescent material can be a promising candidate for temperature sensing.

Ultrasensitive Optical Thermometry via Inhibiting the Energy Transfer in Zero-Dimensional Lead-Free Metal Halide Single Crystals.

Self-referencing optical thermometry based on the fluorescence intensity ratio (FIR) have drawn extensive attention as a result of their high sensitivity and non-invasively fast response to temperature. However, it is a great challenge for luminescent materials to achieve simultaneously high absolute and relative temperature sensitivity based on the FIR technique. Herein, we developed a novel optical thermometer by designing hybrid lead-free metal halide (TTPhP)2MnCl4:Sb3+ (TTPhP+ = tetraphenylphosphonium cation) single crystals with multimodal photoluminescence (PL). The large TTPhP+ organic chain resulted in isolated [MnCl4]2- and [SbCl5]2- in the single crystal, which leads to a negligible energy trasfer process within them. Therefore, the two PL bands (band 1 from [MnCl4]2-) with a peak at 518 nm and band 2 (from [SbCl5]2) with a peak at 640 nm exhibit different thermal-quenching effects, which resulted in excellent temperature sensitivity, with the maximum absolute and relative sensitivities reaching 0.236 K-1 and 3.77% K-1 in a temperature range from 300 to 400 K. Both the absolute and relative sensitivities are among the highest values for luminescence thermometry.

Up-conversion luminescence transparent CaNb2O6 glass ceramics for temperature monitoring

To explore new up-conversion luminescent materials with high sensitivity for optical thermometry, Yb3+/Tm3+ co-doped transparent CaNb2O6 glass ceramics are successfully prepared using the traditional melting and controlling crystallization. Its structure, micro-morphology and luminescence characteristics are studied comprehensively by means of XRD, Raman, TEM and a fluorescence spectrometer. The results show that the luminescence intensity of glass ceramics is significantly higher than that of glasses under 980 nm laser excitation. A dual-mode temperature measurement based on fluorescence intensity ratios (FIR, I690/I796 and I690/I651) is realized by using the different temperature dependence of emission peaks of Tm3+. In a wide temperature range (298 − 573 K), the highest absolute sensitivity (Sa-max) of 0.42‰ K−1 and the supreme relative sensitivity (Sr-max) of 2.65% K−1 based on thermal coupling energy levels (TCELs) are gained. Furthermore, using non-thermal coupling energy levels (NTCELs), Sr-max and Sa-max reach 0.23% K−1 and 20.49% K−1, respectively. This work indicates that the CaNb2O6 glass ceramics as a new type of up-conversion luminescent material have great application prospects in the field of optical thermometry.

Dual‐Functional Nonmetallic Plasmonic Hybrids with Three‐Order Enhanced Upconversion Emission and Photothermal Bio‐Therapy

AbstractPlasmonic semiconductor nanoparticles (NPs) with wide‐range tailorable localized surface plasmon resonance (LSPR) hold exciting prospects on optical signal amplification. In this work, by precisely controlling oxygen vacancies around W atoms, plasmonic bismuth tungstate Bi2WO6 (BWO) nanosheets are constructed to enhance emission of Yb3+/Er3+ co‐doped NaYF4 upconversion nanoparticles (UCNPs). In the optimal conditions, the UCNPs/BWO‐2 hybrids exhibit over three‐order (1260‐fold) enhancement selectively on the 520 nm emission owing to the strong LSPR‐induced electrical field and photothermal effect. Moreover, it is found that the highly efficient emission of UCNPs/BWO‐2 allows it to act as a thermometer to monitor the real‐time local temperature with high absolute sensitivity of 5.8 × 10−3 K−1 in wide temperature range (up to 990 K). For proof‐of‐concept, the dual functions of plasmonic UCNPs/BWO‐2 hybrids on bioimaging and photothermal therapy for cancer cells are demonstrated that can be completely killed within 5 min under 980 nm irradiation. As far as it is known, this work reaches a new level on UCNPs emission enhancement by plasmonic semiconductor, exceeding most plasmonic metals.

Effect of fluorine substitution on the structure and spectral property of fluorotellurite glass for upconversion luminescence thermometry

A series of TeO2–ZnO–ZnF2–La2O3–Yb2O3–Er2O3 glasses (TZL) with different amount of ZnF2 were prepared by the melt quenching method. The effects of fluorine concentration on the density, refractive index, thermal behavior, and vibrational characteristic of TZL glasses were analyzed. The Judd-Ofelt (J-O) theory was employed to study the spectroscopic properties of Er3+ ions. By using the J-O intensity parameters the spontaneous radiative transition probabilities, fluorescence branching ratios, and radiative lifetimes of some concerned transitions of Er3+ were predicted. The potential of TZL glasses for the gain around 1.5 μm was briefly evaluated. Moreover, the upconversion luminescence was investigated under the excitation of 980 nm laser. The dependence of luminescence intensity on pump power revealed that the upconversion luminescence of Er3+ in TZL glasses are contributed by two-photon involved energy transfer processes. Furthermore, the adjacent upconversion green emissions of Er3+ ions were used to temperature sensing based on the fluorescence intensity ratio (FIR) technique. High absolute sensitivity and resolution have been obtained, which indicate that the TZL glasses are potential materials for optical fiber temperature sensors.