GdBO3 and YBO3 crystals under compression

[EN] High-pressure X-ray diffraction studies on nanocrystals of the GdBO3 and YBO3 rare-earth orthoborates are herein reported up to 17.4(2) and 13.4(2) GPa respectively. The subsequent determination of the room- temperature pressure-volume equations of state is presented and discussed in the context of contemporary publications which contradict the findings of this work. In particular, the isothermal bulk moduli of GdBO3 and YBO3 are found to be 170(13) and 163(13) GPa respectively, almost 50% smaller than recent findings. Our experimental results provide an accurate revision of the high-pressure compressibility behaviour of GdBO3 and YBO3 which is consistent with the known systematics in isomorphic borates and previous ab initio calculations. Finally, we discuss how experimental/analytical errors could have led to unreliable conclusions reported elsewhere.The authors thank the financial support from the Spanish Ministerio de Ciencia, Innovacion y Universidades, Spanish Research Agency (AEI), Generalitat Valenciana, and European Fund for Regional Development (ERDF, FEDER) under grants nos. FIS2017-83295-P, MAT2016-75586-C4-1/2/3-P, RTI2018-101020-BI00, PID2019-106383 GB-C41/C42/C43, RED2018-102612-T (MALTA Consolier Team), and Prometeo/2018/123 (EFIMAT). R.T. acknowledges funding from the Spanish MINECO via the Juan de la Cierva Formacion program (FJC2018-036185-I), and J.A.S. acknowledges funding from the Ramon y Cajal Fellowship Program (RYC-2015-17482). We also thank ALBA synchrotron light source for funded experiments 2016021648 and 2016021668 at the MSPD-BL04 beamline.Turnbull, R.; Errandonea, D.; Sans-Tresserras, JÁ.; Cuenca-Gotor, VP.; Vilaplana Cerda, RI.; Ibáñez, J.; Popescu, C.... (2021). GdBO3 and YBO3 crystals under compression. Journal of Alloys and Compounds. 866:1-6. https://doi.org/10.1016/j.jallcom.2021.158962S1686

Synthesis and physicochemical studies of nanophosphors based on modified zinc oxide and lanthanides borates

Wydział ChemiiGłównym celem pracy doktorskiej była synteza nanomateriałów t.j.: modyfikowanego tlenku cynku oraz boranów pierwiastków ziem rzadkich domieszkowanych jonami lantanowców oraz dodatkowo jonami Mg2+ i Li+, a w dalszym etapie przeprowadzenie analizy struktury, morfologii oraz zbadanie właściwości fotofizycznych otrzymanych nanoluminoforów. W celu uzyskania jednofazowych nanoproszków o wysokiej krystaliczności i homogeniczności wybrano kilka metod syntezy. Są to: zol-żelowa metoda Pechniego, reakcja w warunkach hydrotermalnych, współstrącanie oraz proces samospaleniowy. Otrzymano zmodyfikowany tlenek cynku domieszkowany różnymi jonami, tj. Eu3+, Gd3+ lub Mg2+ i Li+, charakteryzujący się czerwoną luminescencją. W celu uzyskania opisywanego luminofora zastosowano zol-żelową metodę Pechiniego, hydrotermalną oraz samospaleniową. Zsyntetyzowano również szereg nanoluminoforów, boranów pierwiastków ziem rzadkich domieszkowanych jonami Eu3+ i Tb3+. W oparciu o analizę struktury metodą Rietvelda, określono dwie nowe grupy przestrzenne dla próbek Gd1-xEuxBO3 otrzymanych metodą Pechiniego i hydrotermalną. Na widmach wzbudzenia obserwowano intensywne pasma związane z przeniesieniem pomiędzy O2- i Eu3+, który zapewniał najbardziej wydajne wzbudzenie emisji nanomateriałów. Natomiast widma emisji, charakteryzowały się typowymi pasmami związanych z emisją jonu lantanowca. Na podstawie obliczeń wydajności kwantowej określono najbardziej wydajny nanoluminofor, t.j. Gd1-xEuxBO3, domieszkowany jonami Eu3+, otrzymany metodą hydrotermalną.The main goal of the doctoral thesis was the synthesis of nanomaterials, such as: modified zinc oxide and rare earth borates doped with lanthanide ions and additional ions, Mg2+ and Li+, and further, analysis of the structure, morphology and photophysical properties of the obtained nanophosphors. In order to obtain single-phase nanopowders with high crystallinity and homogeneity several methods of synthesis were selected. These are: the sol-gel Pechni method, the synthesis under hydrothermal conditions, co-precipitation and combustion reaction. The modified zinc oxide doped with different ions, i.e. Eu3+, Gd3+ or Mg2+ and Li+, characterized by red luminescence, was obtained. In order to obtain the phosphor sol-gel Pechini method, hydrothermal and combustion reaction was used. A series of nanoborates doped with Eu3+ and Tb3+, were also produced. Based on the Rietveld method of structure analysis, two new space groups for the samples Gd1-xEuxBO3 obtained by the Pechini and hydrothermal method, were determined. In the excitation spectra the intense bands associated with transfer between O2-and Eu3+, which provide the most efficient excitation of emission of nanomaterials. The emission spectra, presented the typical bands characteristic for the lanthanide ion emission. On the basis of the quantum yield calculations the most efficient nanophosphor, Gd1-xEuxBO3 obtained by hydrothermal method, was selected

Luminescent materials with dual-mode excitation and tunable emission color for anti-counterfeiting applications

Abstract GdVO4-based dual-mode phosphors were successfully synthesized via a hydrothermal approach. The X-ray diffraction analysis determined the tetragonal structure as well as I41 /amd space group of products by comparing with a reference pattern no. ICDD #01-072-0277. The morphology of yielded phosphors was confirmed by transmission electron microscopy and scanning electron microscopy. Detailed spectroscopy analysis revealed tunable luminescence properties with an increasing Yb3+ content in series of GdVO4: x% Yb3+, y% Tm3+, 5% Eu3+ (x = 5, 10, 15, 20; y = 0.1, 0.5, 1) phosphors. For Yb3+, Tm3+, and Eu3+- codoped phosphors we observed bands related to the 1G4 → 3H6 and 1G4 → 3F4 transitions of Tm3+ ions, occurred through the cooperative up-conversion mechanism, where two nearby Yb3+ ions were involved in near-infrared absorption. Moreover, the GdVO4: 20% Yb3+, 0.5% Tm3+, 5% Eu3+ showed the most outstanding color tunability from red color (x = 0.6338, y = 0.3172) under UV to blue color (x = 0.2640, y = 0.1988) under NIR excitation, which can be applied in anti-counterfeiting activity

Influence of GdVO4:Eu3+ Nanocrystals on Growth, Germination, Root Cell Viability and Oxidative Stress of Wheat (Triticum aestivum L.) Seedlings

The increasing application of lanthanide-doped nanocrystals (LDNCs) entails the risk of a harmful impact on the natural environment. Therefore, in the presented study the influence of gadolinium orthovanadates doped with Eu3+ (GdVO4:Eu3) nanocrystals on wheat (Triticum aestivum L.), chosen as a model plant species, was investigated. The seeds were grown in Petri dishes filled with colloids of LDNCs at the concentrations of 0, 10, 50 and 100 µg/mL. The plants’ growth endpoints (number of roots, roots length, roots mass, hypocotyl length and hypocotyl mass) and germination rate were not significantly changed after the exposure to GdVO4:Eu3+ nanocrystals at all used concentrations. The presence of LDNCs also had no effect on oxidative stress intensity, which was determined on the basis of the amount of lipid peroxidation product (thiobarbituric acid reactive substances; TBARS) in the roots. Similarly, TTC (tetrazolium chloride) assay did not show any differences in cells’ viability. However, root cells of the treated seedlings contained less Evans Blue (EB) when compared to the control. The obtained results, on the one hand, suggest that GdVO4:Eu3+ nanocrystals are safe for plants in the tested concentrations, while on the other hand they indicate that LDNCs may interfere with the functioning of the root cell membrane

New Multicolor Tungstate-Molybdate Microphosphors as an Alternative to LED Components

Due to the ongoing need to create phosphors with the appropriate emission color for the production of light emitting diodes, we decided to synthesize a series of multicolour microphosphors with tunable visible emissions, depending on the composition of dopant ions. In this work, we investigated the structure, morphology, and luminescent properties of new molybdate–tungstate phosphors co-doped with Tb3+ and Eu3+ ions. The conventional high temperature solid state method was used to prepare a series of CaMoyW1−yO4:Eu3+x/Tb3+1−x materials. In order to obtain phosphors with the most promising luminescent properties, the experiment was planned by taking into account the different composition of the matrix and the concentration of the particular dopant ions (Eu3+x/Tb3+1−x, x = 0.001, 0.003, 0.005, 0.007, 0.009). As a result, luminescent materials were obtained with a pure tetragonal crystal structure, the space group of I41/a, confirmed by X-ray diffraction (XRD). The size and shape of the particles obtained from the materials were analyzed based on scanning electron microscopy images. Luminescence spectroscopy (excitation and emission spectra, decay lifetimes) was utilized to characterize the luminescence properties of the as-prepared phosphors. The color change of the emission from green-yellow to orange-red was confirmed using the 1931 Comission Internationale de l’Eclairage (CIE) chromaticity coordinates and color correlated temperature (CCT)

Hydrothermal Synthesis and Structural and Spectroscopic Properties of the New Triclinic Form of GdBO:Eu3+Eu^ {3+} Nanocrystals

Triclinic Gd1-xEuxBO3 nanophosphors have been prepared by a hydrothermal method without using additional coreagents and prior precipitation of precursor (in situ). The formation of the borate nanorods and their crystal structure was refined on the basis of X-ray diffraction patterns (XRD) and well confirmed using various techniques such as infrared spectroscopy (IR), Raman spectroscopy, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The new triclinic crystal structure (space group P1̅) for the GdBO3 nanocrystals and detailed structure parameters were determined with the help of the Rietveld analysis. The spectroscopic characteristics of the synthesized nanomaterials with different concentrations of Eu(3+) ions were defined with the use of luminescence excitation spectra as well as emission spectra and decay kinetics. The Judd-Ofelt parameters (Ω2, Ω4) and quantum efficiency, η, were also calculated for the more detailed analysis of Eu(3+) spectra in the GdBO3 host