Particle size effects on the structure and emission of Eu3+:LaPO4 and EuPO4 phosphors

The authors acknowledge the financial support of the Ministry of Education, Science and Technological Development of the Republic of Serbia (Projects nos. 45020 and 172056). T.G acknowledges to the ERDF PostDoc project No. 1.1.1.2/VIAA/1/16/215 (1.1.1.2/16/I/001).This paper provides the detailed study of (nano)particle's size effect on structural and luminescent properties of LaPO4:Eu3+ synthesized by four different methods: high temperature solid-state, co-precipitation, reverse micelle and colloidal. These methods delivered monoclinic monazite-phase submicron particles (> 100 nm), 4 × 20 nm nanorods and 5 nm spheres (depending on the annealing temperature), 2 × 15 nm nanorods, and ultra-small spheres (2 nm), respectively. The analysis of emission intensity dependence on Eu3+ concentration showed that quenching concentration increases with a decrease of the particle size. The critical distance for energy transfer between Eu3+ ions is found to be 18.2 Å, and the dipole-dipole interaction is the dominant mechanism responsible for the concentration quenching of emission. With the increase in Eu3+ concentration, the unit-cell parameter slightly increases to accommodate larger Eu3+ ions at sites of smaller La3+ ions. Photoluminescent emission spectra presented four characteristic bands in the red spectral region: at 592 nm (5D0→7F1), at 612 nm (5D0→7F2), at 652 nm (5D0→7F3) and at 684 nm (5D0→7F4), while in small colloidal nanoparticles additional emission bands from host defects appear at shorter wavelengths. Intensities of f-f electronic transitions change with particles size due to small changes in symmetry around europium sites, while emission bandwidths increase with the reduction of particle size due to increased structural disorder. Judd-Ofelt analysis showed that internal quantum yield of Eu3+ emission is strongly influenced by particle's morphology.Ministry of Education, Science and Technological Development of the Republic of Serbia (Projects nos. 45020 and 172056); ERDF PostDoc project No. 1.1.1.2/VIAA/1/16/215 (1.1.1.2/16/I/001); Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Visualizing Early Frog Development with Motion-Sensitive 3-D Optical Coherence Microscopy

A motion-sensitive en-face-scanning 3-D optical coherence microscope (OCM) has been designed and constructed to study critical events in the early development of plants and animals. We describe the OCM instrument and present time-lapse movies of frog gastrulation, an early developmental event in which three distinct tissue layers are established that later give rise to all major organ systems. OCM images constructed with fringe-amplitude data show the mesendoderm migrating up along the blastocoel roof, thus forming the inner two tissue layers. Motion-sigma data, measuring the random motion of scatterers, is used to construct complementary images that indicate the presence of Brownian motion in the yolk cells of the endoderm. This random motion provides additional intrinsic contrast that helps to distinguish different tissue types. Depth penetration at 850 nm is sufficient for studies of the outer ectoderm layer, but is not quite adequate for detailed study of the blastocoel floor, about 500 to 800 μm deep into the embryo. However, we measure the optical attenuation of these embryos to be about 35% less at 1310 nm. 2-D OCT images at 1310 nm are presented that promise sufficient depth penetration to test current models of cell movement near the blastocoel floor during gastrulation

A host signature based on TRAIL, IP-10, and CRP for reducing antibiotic overuse in children by differentiating bacterial from viral infections: a prospective, multicentre cohort study

Objectives: Identifying infection aetiology is essential for appropriate antibiotic use. Previous studies have shown that a host-protein signature consisting of TNF-related apoptosis-induced ligand (TRAIL), interferon-γ-induced protein-10 (IP-10), and C-reactive protein (CRP) can accurately differentiate bacterial from viral infections. Methods: This prospective, multicentre cohort study, entitled AutoPilot-Dx, aimed to validate signature performance and to estimate its potential impact on antibiotic use across a broad paediatric population (>90 days to 18 years) with respiratory tract infections, or fever without source, at emergency departments and wards in Italy and Germany. Infection aetiology was adjudicated by experts based on clinical and laboratory investigations, including multiplex PCR and follow-up data. Results: In total, 1140 patients were recruited (February 2017–December 2018), of which 1008 met the eligibility criteria (mean age 3.5 years, 41.9% female). Viral and bacterial infections were adjudicated for 628 (85.8%) and 104 (14.2%) children, respectively; 276 patients were assigned an indeterminate reference standard outcome. For the 732 children with reference standard aetiology, the signature discriminated bacterial from viral infections with a sensitivity of 93.7% (95%CI 88.7–98.7), a specificity of 94.2% (92.2–96.1), positive predictive value of 73.0% (65.0–81.0), and negative predictive value of 98.9% (98.0–99.8); in 9.8% the test results were equivocal. The signature performed consistently across different patient subgroups and detected bacterial immune responses in viral PCR-positive patients. Conclusions: The findings validate the high diagnostic performance of the TRAIL/IP-10/CRP signature in a broad paediatric cohort, and support its potential to reduce antibiotic overuse in children with viral infections

Association of food security status with overweight and dietary intake: exploration of White British and Pakistani-origin families in the Born in Bradford cohort.

BACKGROUND: Food insecurity has been associated with dietary intake and weight status in UK adults and children although results have been mixed and ethnicity has not been explored. We aimed to compare prevalence and trajectories of weight and dietary intakes among food secure and insecure White British and Pakistani-origin families. METHODS: At 12 months postpartum, mothers in the Born in Bradford cohort completed a questionnaire on food security status and a food frequency questionnaire (FFQ) assessing their child's intake in the previous month; at 18 months postpartum, mothers completed a short-form FFQ assessing dietary intake in the previous 12 months. Weights and heights of mothers and infants were assessed at 12-, 24-, and 36-months postpartum, with an additional measurement of children taken at 4-5 years. Associations between food security status and dietary intakes were assessed using Wilcoxon-Mann-Whitney for continuous variables and χ2 or Fisher's exact tests for categorical variables. Quantile and logistic regression were used to determine dietary intakes adjusting for mother's age. Linear mixed effects models were used to assess longitudinal changes in body mass index (BMI) in mothers and BMI z-scores in children. RESULTS: At 12 months postpartum, White British mothers reported more food insecurity than Pakistani-origin mothers (11% vs 7%; p < 0.01) and more food insecure mothers were overweight. Between 12 and 36 months postpartum, BMI increased more among food insecure Pakistani-origin mothers (β = 0.77 units, [95% Confidence Interval [CI]: 0.40, 1.10]) than food secure (β = 0.44 units, 95% CI: 0.33, 0.55). This was also found in Pakistani-origin children (BMI z-score: food insecure β = 0.40 units, 95% CI: 0.22, 0.59; food secure β = 0.25 units, 95% CI: 0.20, 0.29). No significant increases in BMI were observed for food secure or insecure White British mothers while BMI z-score increased by 0.17 (95% CI: 0.13, 0.21) for food secure White British children. Food insecure mothers and children had dietary intakes of poorer quality, with fewer vegetables and higher consumption of sugar-sweetened drinks. CONCLUSIONS: Food security status is associated with body weight and dietary intakes differentially by ethnicity. These are important considerations for developing targeted interventions

Luminescence of Cr3+ ions in ZnAl2O4 and MgAl2O4 spinels: correlation between experimental spectroscopic studies and crystal field calculations

Details of preparation, spectroscopic and structural studies along with crystal field calculations for two Cr3+ doped spinels MgAl2O4 and ZnAl2O4 are given in the present paper. Both compounds show efficient red emission at about 685 nm, which is due to the E-2(g) - GT (4)A(2g) spin-forbidden transition of Cr3+ ions located at the sites with D-3d local symmetry. Analysis of structure of the CrO6 clusters was performed; comparison of the crystal field effects in both compounds revealed that the low-symmetry splitting of the orbital triplet states is more pronounced in ZnAl2O4. Both compounds show potential for applications as red-emitting phosphors. (c) 2016 Elsevier B.V. All rights reserved

Multicolor-tunable emissions of YOF: Ln 3+ /Yb 3+ (Ln 3+ = Ho 3+ , Er 3+ , Tm 3+ ) nanophosphors

Color tuning of down-shifting and up-conversion emissions of YOF:Ln(3+)/Yb3+ (Ln(3+) = Er3+, Tm3+) nanophosphors is demonstrated. Nanophosphors were prepared by the modified sol-gel Pechini method and characterized by the X-ray diffraction, transmission electron microscopy, and photoluminescence spectroscopy. Samples consist of 20 nm particles crystallized in the rhombohedral crystal structure. Depending on the Ln(3+) / Yb3+ concentration ratio and the type of excitation (UV/VIS or NIR) color of the particles emission varied from the blue to red. Commission Internationale de L'Eclairage chromaticity coordinates of emission colors are given for the range of Ln(3+)/Yb3+ concentration ratios for both down-shifting and up-conversion luminescence. We showed that the emission color of these nanophosphors may be additional tuned by simultaneous excitation with UV-VIS and NIR radiation (in different proportion) which yields unique color labels for the anti-counterfeit and security applications

Photoluminescence properties and thermal stability of RE2-xEuxSn2O7 (RE = Y3+, Gd3+, Lu3+) red nanophosphors: An experimental and theoretical study

Defect-fluorite structured Eu 3+ -doped Y 2 Sn 2 O 7 nanoparticles (30–40 nm) were successfully prepared through a facile co-precipitation method without any organic additives or templates followed by calcination in air. Luminescent properties of the as-prepared Y 2-x Eu x Sn 2 O 7 (0.02 ≤ x ≤ 0.6) nanophosphors were fully characterized from an experimental and theoretical point of view (excitation, emission, lifetime, critical concentration, temperature-dependent luminescence and thermal stability, type of interactions and the Judd-Ofelt analysis). The nanophosphors showed relatively sharp excitation bands from 360 to 530 nm and exhibited characteristic emission bands with the most intensive emission centered at 612 nm. In addition, Gd 1.98 Eu 0.02 Sn 2 O 7 and Lu 1.98 Eu 0.02 Sn 2 O 7 samples were prepared in order to study how substitution of RE 3+ (Y 3+ with Gd 3+ and Lu 3+ ions) influences on luminescent properties of RE 1.98 Eu 0.02 Sn 2 O 7 and thermal stability of their luminescence. In order to understand better luminescent properties, the Judd–Ofelt analysis was applied to all the synthesized powders. The highest value of quantum efficiency, ~96%, was estimated for Lu 1.98 Eu 0.02 Sn 2 O 7 . To assess potential application in high-power LEDs, the temperature-dependent emission spectra of Y 1.98 Eu 0.02 Sn 2 O 7 , Gd 1.98 Eu 0.02 Sn 2 O 7 and Lu 1.98 Eu 0.02 Sn 2 O 7 nanophosphors were studied. © 2019 Elsevier B.V

Detailed study of structural and luminescent properties of Y2-xEuxZr2O7 (0 LT = x LT = 1) nanophosphors

Nanocrystalline Y2-xEuxZr2O7 (0 LT = x LT = 1) phosphor particles were prepared by polymer facilitated combustion and subsequent calcination at 800 degrees C. The thorough study of Eu-concentration influence on particles structure, morphology and luminescence is presented. This type of synthesis provides particles of similar to 5 nm in diameter, which crystallize in a defect fluorite structure (space group Fm-3m), and where each particle consists of a single crystallite, as revealed by X-ray diffraction and high-resolution transmission electron microscopy. With the increase of Eu concentration, the unit-cell parameter slightly increases to accommodate larger Eu3+ ions at sites of smaller Y3+, while the shape and size of particles remain the same. Analysis of emission intensity and decay dependence on Eu concentration showed that this host material could be heavily doped with Eu since concentration quenching of emission occurs at high Eu content of 25-30 at.% (with respect to Y ions). The critical distance for energy transfer between Eu ions is estimated to 10.28 A and dipole-quadrupole interaction is found as the dominant mechanism responsible for the concentration quenching of emission. Radiative and non-radiative transition rates, the quantum efficiency of emission, Omega-intensity parameters, and branching ratios of Eu3+ emission are calculated for nanocrystals of all doping concentrations. It is found that more to-the-point expression 86% of emission comes from D-5(0) - GT F-7(2) and D-5(0) - GT F-7(1) transitions. Therefore, this phosphor emits pure red light with (0.661, 0.338) CIE color coordinates. (C) 2017 Elsevier B.V. All rights reserved

Europium(III)-doped A(2)Hf(2)O(7) (A = Y, Gd, Lu) nanoparticles: Influence of annealing temperature, europium(III) concentration and host cation on the luminescent properties

The detailed analyses of structure and luminescence of europium(III)-doped A(2)Hf(2)O(7) (A = Y, Gd, Lu) nanoparticles is presented. Samples were prepared by time and cost effective combustion method that utilize polyethylene glycol both as a chelating agent and as a fuel, with different europium(III) concentrations (from 1 to 12 at.%), annealed at temperatures ranging from 800 to 1400 degrees C, and with alternating A(3+) cation in the A(2)Hf(2)O(7) host. Then, structural variations between materials were analysed by Xray diffraction and structural refinement, while the changes in the luminescence were assessed from the Judd-Ofelt analyses of emission spectra. Nanoparticles prepared at the lowest temperature (800 degrees C) had the smallest particle size of similar to 6 nm and showed the highest quantum efficiency when doped with 1 and 2 at.% of europium(III). Radiative transition rate and quantum efficiency of emission showed Lu2Hf2O7 GT Gd2Hf2O7 GT Y2Hf2O7 trend. (C) 2016 Elsevier B.V. All rights reserved.4th International Conference on the Physics of Optical Materials and CI Devices (ICOM), Aug 31-Sep 04, 2015, Budva, Montenegr

Functionalized biogenic hydroxyapatite with 5-aminosalicylic acid - Sorbent for efficient separation of Pb2+ and Cu2+ ions

The biogenic hydroxyapatite (BHAP), obtained by proper treatment of bovine bones, was functionalized with 5-aminosalicylic acid (5-ASA). The coordination of 5-ASA to the surface of BHAP leads to the charge transfer (CT) complex formation accompanied with absorption in visible spectral range. The sorption ability of surface-modified BHAP with 5-ASA (5-ASA/BHAP) for removal of Pb2+ and Cu2+ ions from single- and bi-component solutions was compared with unmodified BHAP. The thorough characterization of both sorbents, BHAP and 5-ASA/BHAP, was performed including X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), nitrogen adsorption-desorption isotherms, as well as diffuse reflection spectroscopy. Sorption kinetics and equilibriums for both ions (Pb2+ and Cu2+) by as-prepared BHAP and 5-ASA/BHAP are quite different. Functionalized sorbent demonstrated faster sorption kinetic and higher maximum sorption capacity for Pb2+ ions from bi-component solutions. From equimolar Pb2+ and Cu2+ mixture with a total concentration of 10-2 mol/L, 66% of Pb2+ was recovered using BHAP, while 97% using 5-ASA/BHAP. These preliminary data indicate potential applicability of properly functionalized hydroxyapatite for selective removal of heavy metal ions from contaminated water.The peer-reviewed version: [http://cer.ihtm.bg.ac.rs/handle/123456789/3015