In this work, the potential of Li1.8Na0.2TiO3:Mn4+ for the lifetime-based luminescence thermometry is assessed. The material is prepared by the solid-state reaction of Li2CO3, Na2CO3, and ...nanostructured TiO2 at 800 °C, and its monoclinic structure (space group C2/c) is confirmed by X-ray diffraction analysis. In this host, Mn4+ provides strong absorption around 330 nm and 500 nm due to 4A2g → 4T1g and 4A2g→ 4T2g electric dipole forbidden and spin-allowed electron transitions, respectively, and emits around 679 nm on account of 2Eg→4A2g spin forbidden electron transition. Temperature dependences of emission intensity and emission decay are measured over the 10–350 K range. Due to the low value of energy of 4T2g level (20000 cm−1), the strong emission quenching starts at low-temperatures which favors the use of this material for the luminescence thermometry. It is demonstrated that the quite large value of relative sensitivity (2.27% K−1@330 K) facilitates temperature measurements with temperature resolution better than 0.15 K, and with the excellent repeatability.
•Li1.8Na0.2TiO3:Mn4+ was synthesized by the solid-state reaction method in C2/c structure.•The material was used as a probe for the lifetime-based luminescence thermometry.•Mn4+ emits around 679 nm due to of 2Eg→4A2g spin forbidden electron transition.•The material exhibits a large value of relative sensitivity (2.27% K−1@330 K).•Excellent Mn4+ emission repeatability with temperature resolution of 0.15 K.
The performance of Dy3+ doped Gd2Ti2O7 nano-powders for luminescence temperature sensing was tested over a temperature range from 293 to 443K. The Dy3+ ions were incorporated into Gd2Ti2O7 ...nanocrystals using a hydrolytic sol–gel route. Microstructural characterization of the obtained material was performed using transmission electron microscopy and X-ray diffraction measurements. Luminescence spectra of Dy3+ doped Gd2Ti2O7 nano-powders consists of two distinct spectral regions: the high-energy region associated with the trap emission of the Gd2Ti2O7 host and the low-energy region with well-resolved emission peaks of the Dy3+ ions. The ratio between intensities of two Dy3+ emission lines, as well as the ratio between intensities of trap emission of host and Dy3+ emission show strong temperature dependence and are tested for temperature sensing. In both cases, ratiometric measurements provide comparable quality of temperature sensing, and when they are combined the relative sensor sensitivities were found to be higher than 0.9%K−1 over given temperature range. The fluorescence quenching of Dy3+ ions was discussed in terms of simple theoretical models.
•Dy3+ doped Gd2Ti2O7 nanoparticles can serve as probes for luminescence thermometry.•Trap emission of host can be an excellent standard for luminescence thermometry.•Temperature can be measured over 293–443K range with sensitivity reaching 0.9%K−1.
A theoretical model for approximate evaluation of CIE chromaticity coordinates from the Judd-Ofelt intensity parameters has been presented. By reviewing the photoluminescence properties of all the ...lanthanides, the model's applicability was restricted to Nd3+, Sm3+, Eu3+, Tb3+ and Dy3+. Explicit equations for calculation of CIE coordinates for each of the allowed lanthanides were tested on Y2O3:Eu3+, P2O5·ZnO·Al2O3·BaO·PbO:Tb3+, LiNbO3:Dy3+, LaF3:Sm3+, LaF3:Eu3+, Ca3Sc2Si3O12:Eu3+, and TeO2·TiO2·Nb2O5:Nd3+ by comparing the CIE coordinates of the actual spectra to the coordinates obtained from the Judd-Ofelt parameters, with overall adequate matching.
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•CIE coordinates are calculated from the Judd-Ofelt parameters.•Model can be applied to Nd3+, Sm3+, Eu3+, Tb3+ and Dy3+ spectra.•Model is tested on 7 different materials.•Theoretically calculated CIE coordinates are close to real values.•Theoretical CIE calculations are the first step in selection of phosphor material.
Nowadays a large variety of applications are based on solid nanoparticles dispersed in liquids—so called nanofluids. The interaction between the fluid and the nanoparticles plays a decisive role in ...the physical properties of the nanofluid. A novel approach based on the nonradiative energy transfer between two small luminescent nanocrystals (GdVO4:Nd3+ and GdVO4:Yb3+) dispersed in water is used in this work to investigate how temperature affects both the processes of interaction between nanoparticles and the effect of the fluid on the nanoparticles. From a systematic analysis of the effect of temperature on the GdVO4:Nd3+ → GdVO4:Yb3+ interparticle energy transfer, it can be concluded that a dramatic increase in the energy transfer efficiency occurs for temperatures above 45 °C. This change is properly explained by taking into account a crossover existing in diverse water properties that occurs at about this temperature. The obtained results allow elucidation on the molecular arrangement of water molecules below and above this crossover temperature. In addition, it is observed that an energy transfer process is produced as a result of interparticle collisions that induce irreversible ion exchange between the interacting nanoparticles.
The interaction between nanoparticles and fluids has a major role in the properties of nanofluids. By means of nonradiative energy transfer between small luminescent nanoparticles dispersed in water, this work reveals how temperature affects the interactions between a liquid and particles. A crossover affecting diverse temperature‐dependent water properties is evidenced in the change of the luminescence of the nanoparticles.
We report on overcoming the sensitivity limit of Boltzmann's thermometers by utilization of seven thermalized Dy3+ excited states in the Lu1.5Y1·5Al5O12 host. Emission spectra recorded from room ...temperature to 938 K show transitions originating from seven 4F9/2, 4I15/2, 4G11/2, 4I13/2, 4M21/2, 4K17/2, and 4F7/2 excited levels to the 6H15/2 ground state. We introduce the multi-cascade LIR (McLIR) by extending the conventional, two-thermalized level Boltzmann-type LIR to seven thermalized levels. This approach provides higher energy differences between thermalized levels which results in five times larger sensitivity than in the conventional LIR. Considering energy differences between Dy3+ excited states of 1043, 2464, 4331, and 5089 cm−1, the luminescence thermometry with McLIR provided 0.35, 0.84, 1.47, 1.73% K−1 relative sensitivities at 650 K, respectively, in four different LIR combinations. The validity of the McLIR method and the effectiveness of thermalizations between levels is confirmed with the good theoretical fit of experimental data.
•Multilevel-cascade luminescence intensity ratio method McLIR is introduced.•7 thermalized levels of Dy3+ were employed for luminescence thermometry.•5 cascades in McLIR were utilized for increasing sensitivity of Boltzmann thermometer.•McLIR was tested on novel phosphor, LuYAG, up to 938 K.•5x increased sensitivity is obtained compared to the conventional method.
Monoclinic scheelite-type BiVO4 is currently considered as one of the most promising non-titania photocatalysts, wheras tetragonal zircon-type BiVO4 is still poorly understood. Herein, a new and ...simple synthetic approach was applied and nanostructured single-phase zircon-type BiVO4 was successfully prepared by a controllable ethylene-glycol colloidal route. In addition, nanostructured monoclinic scheelite-type BiVO4 powders were also fabricated through annealing of the as-prepared samples. A comparative study of the two BiVO4 polymorphs was conducted and it turned out that the novel synthetic approach had a significant impact on porosity and photocatalytic performance of zircon-structured BiVO4. All the prepared materials, as-prepared and annealed, were mesoporous, while measured values of specific surface area of some zircon-structured samples (∼34 m2/g) were ∼7 times higher than those reported thus far for this phase. Interestingly, for the first time, zircon-type BiVO4, previously considered to be a poor photocatalyst, exhibited a better overall performance in degradation of methyl orange compared to monoclinic scheelite-type BiVO4. Hence, it could be expected that the here-presented synthesis and observations will both arouse interest in scarcely studied tetragonal zircon-type BiVO4 and facilitate as well as speed up further research of its properties.
This paper presents the Cr3+-activated Mg2TiO4 phosphor temperature dependance of its near infrared luminescence and its potential in the optical thermometry applications. In this respect, ...temperature dependences of three emission features were tested over the broad temperature range (10–500 K): (i) the luminescence intensity ratio (LIR) between emissions from 4T2→4A2 and 2E→4A2 transitions, (ii) the emission lifetime, and (iii) the shift of the 2E→4A2 emission band. We observed that LIR follows the Boltzmann equation for T > 300 K with the maximal value of relative sensitivity of 1.73 %K−1. The lifetime value of the 2E→4A2 transition strongly decreases with temperature with a maximal relative sensitivity of about 0.75 %K−1 at around 430K. Finally, the shift of the emission band is about 65 cm−1 over the complete temperature range.
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•Synthesis of single phase Mg2TiO4:Cr3+ phosphor.•Multi readout approach to temperature sensing in first biological NIR window.•The maximum relative sensitivity of 1.73 %K−1 in the LIR mode at physiological temperatures.•The maximum relative sensitivity 0.75 %K−1 in the lifetime mode in broad temperature range from 100 K to 400 K.•Significant red shift of the Cr3+ R line with temperature increase.
Upconversion sub-micron particles are one of the most perspective materials due to their wide application range, the most important being in the bio-medicinal field where they can be used for ...labeling, sensing, treatment or drug delivery. Chemically stable upconversion sub-micron particles of La2O2S co-doped with Yb3+/Ho3+ and Yb3+/Tm3+ were synthesized and characterized. Different concentrations of Yb3+/Ho3+ and Yb3+/Tm3+ were successfully incorporated into the hexagonal crystal structure of lanthanum oxysulfide using the optimized solution combustion synthesis method with urea as a fuel. Sub-micron particles of less than 50 nm in diameter showed the typical upconversion photoluminescence when exited by 980 nm laser. The highest PL intensities were obtained in La2O2S co-doped with 8 wt% Yb and 1.5 wt% Ho, or in case of La2O2S:Yb3+/Tm3+ with 4 wt% Yb and 0.5 wt% Tm.
The CIE 1976 chromaticity coordinates of Ho3+ photoluminescence emission are (0.119, 0.581), with color purity of 98.7 %. The chromaticity of upconversion emission was invariant to doping concentrations.
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•La2O2S:Yb3+/Tm3+ and La2O2S:Yb3+/Ho3+ were synthesized by the optimized combustion technique.•Microcrystalline sub-micron particles are in pure hexagonal phase and average 50 nm diameter.•Upconversion photoluminescence is typical for the doped lanthanide pair.
Wooden cultural heritage serves as a very important source of information for historians and researchers. Also, it imposes an obligation on the science to keep this legacy for future generations in a ...proper condition. Among other techniques of conservation of wooden cultural heritage, a very suitable method is impregnation of the wood with the polymer, whereby the wood/polymer composites are formed. This paper describes the method of preparing the wood/polymer composites based on beechwood, using five different monomer systems. The method of lyophilization and subsequent polymerization by gamma radiation was used. After lyophilization and immersing in the monomer solutions, the wood samples were dried and irradiated with a dose of 25 kGy and different gamma irradiation dose rates. The weight of the samples before and after this procedure was measured. Also, changes in the mechanical properties of wood (compression test) before and after treatment were examined. We also examined the effect of radiation dose rate on polymerization. Based on the weight differences, dose rates and materials characterization we determined which of the monomer solution and dose rate are the most suitable for making beechwood/polymer composites.
•Wood/polymer composites have been prepared with different monomer compounds in order to improve the wood properties.•The method of lyophilization and subsequent polymerization by gamma radiation is used.•The monomer concentration and composition do not play a significant role in the amount of polymer loading.•Butyl methacrylate solutions show slightly higher loading values than styrene solutions.•The dose rate significantly affects the polymer loading - the values of polymer loading increase with the highest dose rate.
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