The sensitivity of luminescence thermometry is enhanced at high temperatures when using a three-level luminescence intensity ratio approach with Dy3+- activated yttrium aluminum perovskite. This ...material was synthesized via the Pechini method, and the structure was verified using X-ray diffraction analysis. The average crystallite size was calculated to be around 46 nm. The morphology was examined using scanning electron microscopy, which showed agglomerates composed of densely packed, elongated spherical particles, the majority of which were 80–100 nm in size. The temperature-dependent photoluminescence emission spectra (ex = 353 nm, 300–850 K) included Dy3+ emissions in blue (458 nm), blue (483 nm), and violet (430 nm, T 600 K). Luminescence intensity ratio, the most utilized temperature readout method in luminescent thermometry, was used as the testing method: a) using the intensity ratio of Dy3+ ions and 4I15/2→6H15/2/4F9/2→6H15/2 transitions; and b) employing the third, higher energy 4G11/2 thermalized level, i.e., using the intensity ratio of 4G11/2→6H15/2/4F9/2→6H15/2 transitions, thereby showing the relative sensitivities of 0.41% K−1 and 0.86% K−1 at 600 K, respectively. This more than doubles the increase in sensitivity and therefore demonstrates the method’s usability at high temperatures, although the major limitation of the method is the chemical stability of the host material and the temperature at which the temperature quenching commences. Lastly, it must be noted that at 850 K, the emission intensities from the energetically higher levels were still increasing in YAP: Dy3+.
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.
The multiparametric luminescence thermometry with Dy3+, Cr3+ double activated yttrium aluminium garnet – YAG is demonstrated. Phospors were synthesized via Pechini method and their structure is ...confirmed by X-ray diffraction analysis. Mean crystallite size of powders was calculated to be ~22 nm. Morphology was investigated using scanning electron microscopy showing combination of dense, different size chunks constituted of spherical particles bellow 50 nm in size. Photoluminescence emission spectra of the Dy3+, Cr3+ double activated YAG consist of blue and yellow Dy3+ emissions and the broad, deep red Cr3+ emission. The decrease in the Dy3+ emission intensity with the increase in the Cr3+ content indicates the efficient energy transfer from Dy3+ to Cr3+ of ~90%. Temperature-dependant photoluminescence emission measurements are performed under 484 nm and 582 nm excitation in the steady-state domain and in the 175 K–650 K temperature range. The noted alterations of luminescence with temperature present an excellent base for studying the multiparametric temperature readouts. The luminescence intensity ratio, the most frequently exploited luminescent thermometry temperature readout method, was tested using: i) the combination of Dy3+ and Cr3+ emissions, ii) using the double excitation approach, and iii) using Cr3+ emission only, with relative sensitivities of 0.64 %K−1 at 175 K, 0.96 %K−1 at 200 K and 2.2 %K−1 at 200 K, respectively.
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•Multiparametric luminescence thermometry with Dy3+, Cr3+ double activated YAG.•PL consists of blue and yellow Dy3+ emissions and the broad, deep red Cr3+ emission.•Efficient energy transfer (~90%) from Dy3+ to Cr3+ in theYAG host.•LIR using: i) Dy3+ and Cr3+ emissions, ii) double excitation, and iii) Cr3+ emission.•Sr of i) 0.64 %K−1 at 175 K, ii) 0.96 %K−1 at 200 K and iii) 2.2 %K−1 at 200 K.
This work aimed to examine the influence of the storage period on the content of toxic elements (As, Cd, Hg, and Pb) in five types of canned meat products regularly used in the Serbian Armed Forces. ...Cans of beef goulash (BG), pork ragout (PR), spam (SP), liver pate (LP), and meatballs in tomato sauce (MB), produced according to military standards and stored under regular conditions, were analyzed. Meat products were packed in tin cans made according to special requirements in terms of tin and varnish application and stored for up to 6 years. The content of toxic elements varied depending on the analyzed product. The highest average content of arsenic was in BG (10.00 μg/kg), cadmium in LP (35.91 μg/kg), and mercury and lead in PR (15.04 and 8.00 μg/kg, respectively). The average concentrations of As, Cd, Hg, and Pb in all types of canned meat products were significantly lower than the maximum permitted levels in food currently in force by local and EU legislation. The storage period did not significantly affect the level of toxic elements, although higher concentrations were found in samples stored for more than 2 years. Examination of raw materials, spices, and additives showed that the highest Cd and Pb concentrations, which can affect the total level of these elements in meat products, were found in red ground pepper (Cd above 150 μg/kg) and dish supplement (Pb of 250 μg/kg). The assessment of the weekly intake of toxic elements through canned meat showed that it is significantly lower than the values that affect adversely to human health, as determined by the FAO/WHO and EFSA. However, as there is a constant possibility of contamination of raw materials and food additives, primarily due to environmental pollution, it is recommended to monitor the content of heavy metals in food permanently and assess their risk to human health.
This paper demonstrates the effects of Li+ co-doping on the structure, morphology, and luminescence properties of GdVO4:Er3+/Yb3+ phosphor prepared using a high-temperature solid-state chemistry ...method. The GdVO4:Er3+/Yb3+ powders synthesized with the Li+ co-dopant (in concentrations of 0, 5, 10, and 15mol%) are characterized by X-ray powder diffraction, scanning electron microscopy, and photoluminescence spectroscopy. Structural analysis showed that powders co-doped with Li+ have larger crystallite sizes and slightly smaller crystal lattice parameters than powders prepared without Li+ ions. Photoluminescence down-conversion (345-nm excitation) and up-conversion (980-nm excitation) spectra show characteristic Er3+ emissions, with the most intense bands peaking at 525nm (2H11/2→4I15/2 transition) and 552nm (4S3/2→4I15/2). The intensity of up-conversion emission from GdVO4:Er3+/Yb3+ is enhanced (by a factor of four) by co-doping with 5mol% of Li+ ions. The mechanisms responsible for this emission enhancement are discussed.
UC emission spectra for GdVO4:1.5-mol% Er3+/20-mol% Yb3+ powders co-doped with different concentrations of Li+ ions, recorded under 980-nm excitation. Display omitted
•5-mol% Li+ co-doped powders have 400% enhanced up-conversion emission intensity.•15-mol% Li+ co-doping produces 40% higher emission in down-conversion.•Li+ co-doped powders have larger crystallite size and smaller lattice parameters.
•Interactive effects of dietary protein level and oil source examined.•Changes in proximate, fatty acid composition of common carp fillets observed.•Production performance observed and no detrimental ...effects of the diets were observed.•The oil sources in the diets showed significant effect on dietary fatty acid compositions.•The dietary protein level influenced proximate composition of fish fillets.
Fish meal and fish oil represent main protein and lipid sources in fish feed, but there is a growing need for sustainable alternatives to these ingredients. In this study, four isolipid extruded diets for carp (Cyprinus carpio L.) were used: ROHP (rapeseed oil-high protein), FOHP (fish oil-high protein); ROLP (rapeseed oil-low protein) and FOLP (fish oil-low protein). The trial lasted 75 days. No statistically significant effect of oil source or protein level or interactions of these factors was observed in final body weight, growth parameters or in feed conversion ratio. Protein sparing effect and omega-3 sparing effect were observed in the present study. The results of this experiment showed no negative effects on growth parameters, or major detrimental effects on fatty acid composition of muscle tissue in common carp when fish fed with diets supplemented with rapeseed oil (RO). Furthermore, an enhanced protein sparing effect was observed, when fish fed with lower protein diets, but significant accumulation of crude lipid was observed as a result of lowering protein level. The results of this study showed that diets supplemented with rapeseed oil can be used successfully in common carp cage production.
Luminescence of Mn4+ activated Li4Ti5O12 Medić, Mina; Ristić, Zoran; Kuzman, Sanja ...
Journal of luminescence,
December 2020, 2020-12-00, Letnik:
228
Journal Article
Recenzirano
This work demonstrates the luminescence of Mn4+ activated cubic spinel Li4Ti5O12 (LTO) powders. One-step solid-state method was used to obtain eleven samples with different quantities of Mn4+. The ...deep red emission centered at around 696 nm originates from 2Eg → 4A2g spin forbidden electronic transitions from 3 d3 electron configuration of Mn4+ ion. The concentration quenching of emission is also observed in values of excited-state lifetimes, ranging from 212 μs to 143 μs. Such emission in the red spectral region which can be excited by blue light is suitable for the plant growth LEDs. The exchange charge model (ECM) of crystal field was used to calculate the Mn4+ energy levels in the LTO host. The temperature dependence of the Mn4+ emission in LTO was measured in the 10–350 K temperature range. Excited-state lifetime strongly changes with temperature. A very large value of relative sensitivity of 2.6% K−1 is found at 330 K, which facilitates temperature measurements with the temperature resolution of about 0.26 K. A low concentration of Nb5+ co-doping sensitizes the Mn4+ optical center effectively showing a relative increment of emission intensity.
•Deep red luminescence of Mn4+ activated cubic spinel Li4Ti5O12 (LTO) powders.•The Mn4+ emission and lifetime measured in the 10–350 K temperature range.•The exchange charge model of crystal field was used to calculate the Mn4+ energy levels.•A very large value of relative sensitivity of 2.6% K−1 is found at 330 K.•Nb5+ co-doping sensitizes the Mn4+ showing a relative increment of emission intensity.
Herein, the synthesis, structural and crystal field analysis and optical spectroscopy of Mn4+ doped metal titanates ATiO3 (A = Ca, Mg) are presented. Materials of desired phase were prepared by ...molten salt assisted sol-gel method in the powder form. Crystallographic data of samples were obtained by refinement of X-ray diffraction measurements. From experimental excitation and emission spectra and structural data, crystal field parameters and energy levels of Mn4+ in CaTiO3 and MgTiO3 were calculated by the exchange charge model of crystal-field theory. It is found that crystalline field strength is lower (Dq = 1831 cm−1) in the rhombohedral Ilmenite MgTiO3 structure due to the relatively longer average Mn4+O2− bond distance (2.059 Å), and higher (Dq = 2017 cm−1) in orthorhombic CaTiO3 which possess shorter average Mn4+O2− bond distance (1.956 Å). Spectral positions of the Mn4+2Eg → 4A2g transition maxima is 709 nm in MgTiO3 and 717 nm in CaTiO3 respectively in good agreement with calculated values.
•Mn4+ doped titanates CaTiO3 and MgTiO3 via Molten salt assisted sol-gel method.•Calculated crystal field parameters and energy levels of Mn4+ in the hosts.•Smallest fraction of covalence in the Mn4+-O2− bonding in MgTiO3 among ATiO3.•The Mn4+2Eg → 4A2g emission transition in MgTiO3 is at the highest energy among ATiO3
We synthesized Eu3+-doped CsY2F7 and RbY2F7 nanoparticles (orthorhombic crystal structure, Pnna space group, No. 52) by the microwave-assisted solvothermal technique and investigated the influence of ...reaction temperature and fluoride ion concentration on the particles’ phase and crystal structure. Fluoride ions were added in excess of the stoichiometric amount to achieve the orthorhombic phase for CsY2F7 and to convert the cubic RbY3F10 to the orthorhombic RbY2F7. Mild synthesis conditions yielded nanoparticles with crystallites ranging in size from 19 to 37 nm and a combination of spherical, rod-like, and hexagonal shapes. Nanoparticles emit a strong orange and red light when excited into the Eu3+5L6 level, which is centered around 390 nm. The strongest emission peak is around 612 nm, which comes from the 5D0→7F2 electronic transitions. Emission intensity dependence on Eu3+ concentration revealed that nanoparticles can be heavily doped with Eu3+, up to 25 % with respect to Y3+. Emission decay measurements provided values of excited state lifetimes of 6.2 ms for the Cs(Y0.75Eu0.25)2F7 and 6.0 ms for the Rb(Y0.75Eu0.25)2F7.
Surface modification of Al2O3 powders, prepared using reproducible sol-gel synthetic route with small colorless organic molecules, induces charge transfer complex formation and the appearance of ...absorption in the visible spectral region. Comprehensive microstructural characterization involving transmission electron microscopy, X-ray diffraction analysis, and nitrogen adsorption–desorption isotherms, revealed that γ-crystalline alumina powders consist of mesoporous particles in the size range from 0.1 to 0.3 μm, with specific surface area of 54.8 m2/g, and pore radius between 3 and 4 nm. The attachment of catecholate-type of ligands (catechol, caffeic acid, gallic acid, dopamine and 2,3-dihydroxy naphthalene), salicylate-type of ligands (salicylic acid and 5-amino salicylic acid), and ascorbic acid, to the surface such γ-Al2O3 particles leads to the formation of colored powders and activates their absorption in visible-light spectral region. To the best of our knowledge, similar transformation of an insulator (Al2O3), with the band gap energy of 8.7 eV, into a semiconductor-like hybrid material with tunable optical properties has not been reported in the literature before. The density functional theory (DFT) calculations with periodic boundary conditions were performed in order to estimate the energy gaps of various inorganic/organic hybrids. The calculated values compare well with the experimental data. The good agreement between the calculated and experimentally determined band gaps was found, thus demonstrating predictive ability of the theory when proper model is used.
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•Surface modification of mesoporous Al2O3 powder with benzene derivatives.•Charge transfer complex formation between Al2O3 and small colorless organic molecules.•Visible-light activity of surface-modified Al2O3 powders.•Large-scale quantum chemical calculations based on density functional theory.
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