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Sample records for deficient perovskites srco1-xmxo3-d

  1. Perovskite SrCo0.9 Nb0.1 O3-δ as an Anion-Intercalated Electrode Material for Supercapacitors with Ultrahigh Volumetric Energy Density.

    Science.gov (United States)

    Zhu, Liang; Liu, Yu; Su, Chao; Zhou, Wei; Liu, Meilin; Shao, Zongping

    2016-08-08

    We have synthesized and characterized perovskite-type SrCo0.9 Nb0.1 O3-δ (SCN) as a novel anion-intercalated electrode material for supercapacitors in an aqueous KOH electrolyte, demonstrating a very high volumetric capacitance of about 2034.6 F cm(-3) (and gravimetric capacitance of ca. 773.6 F g(-1) ) at a current density of 0.5 A g(-1) while maintaining excellent cycling stability with a capacity retention of 95.7 % after 3000 cycles. When coupled with an activated carbon (AC) electrode, the SCN/AC asymmetric supercapacitor delivered a specific energy density as high as 37.6 Wh kg(-1) with robust long-term stability. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Phase stability and oxygen non-stoichiometry of SrCo0.8Fe0.2O3-d measured by in-situ neutron diffraction

    NARCIS (Netherlands)

    McIntosh, Steven; McIntosh, S.; Vente, Jaap F.; Haije, Wim G.; Blank, David H.A.; Bouwmeester, Henricus J.M.

    2006-01-01

    The phase stability, oxygen stoichiometry and expansion properties of SrCo0.8Fe0.2O3−δ (SCF) were determined by in situ neutron diffraction between 873 and 1173 K and oxygen partial pressures of 5×10−4 to 1 atm. At a pO2 of 1 atm, SCF adopts a cubic perovskite structure, space group Pm3¯m, across

  3. Effect of A-site deficiency in LaMn_0_._9Co_0_._1O_3 perovskites on their catalytic performance for soot combustion

    International Nuclear Information System (INIS)

    Dinamarca, Robinson; Garcia, Ximena; Jimenez, Romel; Fierro, J.L.G.; Pecchi, Gina

    2016-01-01

    Highlights: • A-site defective perovskites increases the oxidation state of the B-cation. • Not always non-stoichiometric perovskites exhibit higher catalytic activity in soot combustion. • The highly symmetric cubic crystalline structure diminishes the redox properties of perovskites. - Abstract: The influence of lanthanum stoichiometry in Ag-doped (La_1_-_xAg_xMn_0_._9Co_0_._1O_3) and A-site deficient (La_1_-_xMn_0_._9Co_0_._1O_3_-_δ) perovskites with x equal to 10, 20 and 30 at.% has been investigated in catalysts for soot combustion. The catalysts were prepared by the amorphous citrate method and characterized by XRD, nitrogen adsorption, XPS, O_2-TPD and TPR. The formation of a rhombohedral excess-oxygen perovskite for Ag-doped and a cubic perovskite structure for an A-site deficient series is confirmed. The efficient catalytic performance of the larger Ag-doped perovskite structure is attributed to the rhombohedral crystalline structure, Ag_2O segregated phases and the redox pair Mn"4"+/Mn"3"+. A poor catalytic activity for soot combustion was observed with A-site deficient perovskites, despite the increase in the redox pair Mn"4"+/Mn"3"+, which is attributed to the cubic crystalline structure.

  4. Effect of A-site deficiency in LaMn{sub 0.9}Co{sub 0.1}O{sub 3} perovskites on their catalytic performance for soot combustion

    Energy Technology Data Exchange (ETDEWEB)

    Dinamarca, Robinson [Department of Physical Chemistry, Faculty of Chemical Sciences, University of Concepción, Concepción (Chile); Garcia, Ximena; Jimenez, Romel [Department of Chemical Engineering, Faculty of Engineering, University of Concepción, Concepción (Chile); Fierro, J.L.G. [Instituto de Catálisis y Petroleoquímica, CSIC, Cantoblanco, 28049 Madrid (Spain); Pecchi, Gina, E-mail: gpecchi@udec.cl [Department of Physical Chemistry, Faculty of Chemical Sciences, University of Concepción, Concepción (Chile)

    2016-09-15

    Highlights: • A-site defective perovskites increases the oxidation state of the B-cation. • Not always non-stoichiometric perovskites exhibit higher catalytic activity in soot combustion. • The highly symmetric cubic crystalline structure diminishes the redox properties of perovskites. - Abstract: The influence of lanthanum stoichiometry in Ag-doped (La{sub 1-x}Ag{sub x}Mn{sub 0.9}Co{sub 0.1}O{sub 3}) and A-site deficient (La{sub 1-x}Mn{sub 0.9}Co{sub 0.1}O{sub 3-δ}) perovskites with x equal to 10, 20 and 30 at.% has been investigated in catalysts for soot combustion. The catalysts were prepared by the amorphous citrate method and characterized by XRD, nitrogen adsorption, XPS, O{sub 2}-TPD and TPR. The formation of a rhombohedral excess-oxygen perovskite for Ag-doped and a cubic perovskite structure for an A-site deficient series is confirmed. The efficient catalytic performance of the larger Ag-doped perovskite structure is attributed to the rhombohedral crystalline structure, Ag{sub 2}O segregated phases and the redox pair Mn{sup 4+}/Mn{sup 3+}. A poor catalytic activity for soot combustion was observed with A-site deficient perovskites, despite the increase in the redox pair Mn{sup 4+}/Mn{sup 3+}, which is attributed to the cubic crystalline structure.

  5. Crystal structure and lithium ion conductivity of A-site deficient perovskites La1/3-xLi3xTaO3

    International Nuclear Information System (INIS)

    Mizumoto, Katsuyoshi; Hayashi, Shinsuke

    1997-01-01

    The crystal structure and lithium ion conductivity of La 1/3-x Li 3x TaO 3 solid solutions with the A-site deficient perovskite structure have been studied. Single phase solid solutions were obtained in the range of x=0 to 1/6. Change from tetragonal to cubic structure and decrease in the lattice volume were observed with increasing the x value. The maximum conductivity obtained was 7 x 10 -3 S·m -1 at x=0.06. The composition-dependence on the carrier concentration was calculated and compared with conductivity data. (author)

  6. A-Site Deficient (Pr0.6Sr0.4)(1-s)Fe0.8Co0.2O3-delta Perovskites as Solid Oxide Fuel Cell Cathodes

    DEFF Research Database (Denmark)

    Kammer Hansen, Kent

    2009-01-01

    Five A-site deficient (Pr0.6Sr0.4)1−sFe0.8Co0.2O3perovskites (s=0.01, 0.05, 0.10, 0.15, and 0.20) were synthesized using the glycine-nitrate process. The perovskites were characterized with powder X-ray diffraction (XRD), dilatometry, four-point dc conductivity measurements, and electrochemical...... resistance more than 3 times lower than the weakly A-site deficient (Pr0.6Sr0.4)0.99Fe0.8Co0.2O3perovskite. ©2009 The Electrochemical Society...

  7. Facile Synthesis of SrCO3-Sr(OH2/PPy Nanocomposite with Enhanced Photocatalytic Activity under Visible Light

    Directory of Open Access Journals (Sweden)

    Alfredo Márquez-Herrera

    2016-01-01

    Full Text Available Pyrrole monomer was chemically polymerized onto SrCO3-Sr(OH2 powders to obtain SrCO3-Sr(OH2/polypyrrole nanocomposite to be used as a candidate for photocatalytic degradation of methylene blue dye (MB. The material was characterized by Fourier transform infrared (FTIR spectroscopy, UV/Vis spectroscopy, and X-ray diffraction (XRD. It was observed from transmission electronic microscopy (TEM analysis that the reported synthesis route allows the production of SrCO3-Sr(OH2 nanoparticles with particle size below 100 nm which were embedded within a semiconducting polypyrrole matrix (PPy. The SrCO3-Sr(OH2 and SrCO3-Sr(OH2/PPy nanocomposites were tested in the photodegradation of MB dye under visible light irradiation. Also, the effects of MB dye initial concentration and the catalyst load on photodegradation efficiency were studied and discussed. Under the same conditions, the efficiency of photodegradation of MB employing the SrCO3-Sr(OH2/PPy nanocomposite increases as compared with that obtained employing the SrCO3-Sr(OH2 nanocomposite.

  8. (La1-xSrx)0.98MnO3 perovskite with A-site deficiencies toward oxygen reduction reaction in aluminum-air batteries

    Science.gov (United States)

    Xue, Yejian; Miao, He; Sun, Shanshan; Wang, Qin; Li, Shihua; Liu, Zhaoping

    2017-02-01

    The strontium doped Mn-based perovskites have been proposed as one of the best oxygen reduction reaction catalysts (ORRCs) to substitute the noble metal. However, few studies have investigated the catalytic activities of LSM with the A-site deficiencies. Here, the (La1-xSrx)0.98MnO3 (LSM) perovskites with A-site deficiencies are prepared by a modified solid-liquid method. The structure, morphology, valence state and oxygen adsorption behaviors of these LSM samples are characterized, and their catalytic activities toward ORR are studied by the rotating ring-disk electrode (RRDE) and aluminum-air battery technologies. The results show that the appropriate doping with Sr and introducing A-site stoichiometry can effectively tailor the Mn valence and increase the oxygen adsorption capacity of LSM. Among all the LSM samples in this work, the (La0.7Sr0.3)0.98MnO3 perovskite composited with 50% carbon (50%LSM30) exhibits the best ORR catalytic activity due to the excellent oxygen adsorption capacity. Also, this catalyst has much higher durability than that of commercial 20%Pt/C. Moreover, the maximum power density of the aluminum-air battery using 50%LSM30 as the ORRC can reach 191.3 mW cm-2. Our work indicates that the LSM/C composite catalysts with A-site deficiencies can be used as a promising ORRC in the metal-air batteries.

  9. High performance photodetector based on 2D CH3NH3PbI3 perovskite nanosheets

    International Nuclear Information System (INIS)

    Li, Pengfei; Shivananju, B N; Li, Shaojuan; Bao, Qiaoliang; Zhang, Yupeng

    2017-01-01

    In this work, a high performance vertical-type photodetector based on two-dimensional (2D) CH 3 NH 3 PbI 3 perovskite nanosheets was fabricated. The low trap density of the perovskite nanosheets and their short carrier diffusion distance result in a significant performance enhancement of the perovskite-based photodetector. The photoresponsivity of this vertical-type photodetector is as high as 36 mA W −1 at visible wavelength, which is much better than traditional perovskite photodetectors (0.34 mA W −1 ). Compared with traditional planar-type perovskite-based photodetectors, this vertical-type photodetector also shows the advantages of low-voltage operation and large responsivity. These results may pave the way for exploiting high performance perovskite-based photodetectors with an ingenious device design. (paper)

  10. Highly Efficient 2D/3D Hybrid Perovskite Solar Cells via Low-Pressure Vapor-Assisted Solution Process.

    Science.gov (United States)

    Li, Ming-Hsien; Yeh, Hung-Hsiang; Chiang, Yu-Hsien; Jeng, U-Ser; Su, Chun-Jen; Shiu, Hung-Wei; Hsu, Yao-Jane; Kosugi, Nobuhiro; Ohigashi, Takuji; Chen, Yu-An; Shen, Po-Shen; Chen, Peter; Guo, Tzung-Fang

    2018-06-08

    The fabrication of multidimensional organometallic halide perovskite via a low-pressure vapor-assisted solution process is demonstrated for the first time. Phenyl ethyl-ammonium iodide (PEAI)-doped lead iodide (PbI 2 ) is first spin-coated onto the substrate and subsequently reacts with methyl-ammonium iodide (MAI) vapor in a low-pressure heating oven. The doping ratio of PEAI in MAI-vapor-treated perovskite has significant impact on the crystalline structure, surface morphology, grain size, UV-vis absorption and photoluminescence spectra, and the resultant device performance. Multiple photoluminescence spectra are observed in the perovskite film starting with high PEAI/PbI 2 ratio, which suggests the coexistence of low-dimensional perovskite (PEA 2 MA n -1 Pb n I 3 n +1 ) with various values of n after vapor reaction. The dimensionality of the as-fabricated perovskite film reveals an evolution from 2D, hybrid 2D/3D to 3D structure when the doping level of PEAI/PbI 2 ratio varies from 2 to 0. Scanning electron microscopy images and Kelvin probe force microscopy mapping show that the PEAI-containing perovskite grain is presumably formed around the MAPbI 3 perovskite grain to benefit MAPbI 3 grain growth. The device employing perovskite with PEAI/PbI 2 = 0.05 achieves a champion power conversion efficiency of 19.10% with an open-circuit voltage of 1.08 V, a current density of 21.91 mA cm -2 , and a remarkable fill factor of 80.36%. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Mechanical control of magnetism in oxygen deficient perovskite SrTiO3.

    Science.gov (United States)

    Zhang, Yajun; Wang, Jie; Sahoo, M P K; Shimada, Takahiro; Kitamura, Takayuki

    2015-10-28

    Mechanical control of magnetism in perovskite oxides is an important and promising approach in spintronics. Based on the first-principles calculations, we demonstrate that a negative pressure leads to a great enhancement of magnetic moment in deficient SrTiO3 with oxygen vacancies, whereas a positive pressure results in the gradual disappearance of magnetism. Spin charge density, Bader charge analysis and electronic density of states successfully elucidate the origin and underlying physics of the enhancement and disappearance of magnetism. It is found that the split electronic states of dz(2), dyz and dzx in the 3d orbitals of Ti atoms remarkably contribute to the occupancy of majority spin states under negative pressure, which induces a large magnetic moment. Under positive pressure, however, the equal occupancy of both majority and minority t2g and eg states leads to the disappearance of magnetization. In addition, both negative and positive pressures can largely lower the vacancy formation enthalpy, suggesting that the oxygen vacancy is preferable with pressure. Our findings may provide a mechanism to achieve the pressure control of magnetization in nonmagnetic perovskite oxides.

  12. One-Year stable perovskite solar cells by 2D/3D interface engineering

    Science.gov (United States)

    Grancini, G.; Roldán-Carmona, C.; Zimmermann, I.; Mosconi, E.; Lee, X.; Martineau, D.; Narbey, S.; Oswald, F.; de Angelis, F.; Graetzel, M.; Nazeeruddin, Mohammad Khaja

    2017-06-01

    Despite the impressive photovoltaic performances with power conversion efficiency beyond 22%, perovskite solar cells are poorly stable under operation, failing by far the market requirements. Various technological approaches have been proposed to overcome the instability problem, which, while delivering appreciable incremental improvements, are still far from a market-proof solution. Here we show one-year stable perovskite devices by engineering an ultra-stable 2D/3D (HOOC(CH2)4NH3)2PbI4/CH3NH3PbI3 perovskite junction. The 2D/3D forms an exceptional gradually-organized multi-dimensional interface that yields up to 12.9% efficiency in a carbon-based architecture, and 14.6% in standard mesoporous solar cells. To demonstrate the up-scale potential of our technology, we fabricate 10 × 10 cm2 solar modules by a fully printable industrial-scale process, delivering 11.2% efficiency stable for >10,000 h with zero loss in performances measured under controlled standard conditions. This innovative stable and low-cost architecture will enable the timely commercialization of perovskite solar cells.

  13. Photovoltaic Effect of 2D Homologous Perovskites

    International Nuclear Information System (INIS)

    Jung, Mi-Hee

    2017-01-01

    Highlights: • The mixed perovskite was prepared by exposure of MAI gas on the BAPbI_4 film. • The increased dimensional perovskite shows a smaller band gap than 2D perovskite. • The mixed perovskite system shows the vertical crystal orientation. • The mixed perovskite cell exhibits the higher Jsc and FF than 2D perovskite cell. - Abstract: The controlled growth of mixed dimensional perovskite structures, (C_6H_5CH_2NH_2)(CH_3NH_3)_n_-_1Pb_nI_3_n_+_1, through the introduction of CH_3NH_3I molecule vapor into the two-dimensional perovskite C_6H_5CH_2NH_3PbI_4 structure and its application in photovoltaic devices is reported. The dimensionality of (C_6H_5CH_2NH_2)(CH_3NH_3)_n_-_1Pb_nI_3_n_+_1 is controlled using the exposure time to the CH_3NH_3I vapor on the C_6H_5CH_2NH_3PbI_4 perovskite film. As the stacking of the lead iodide lattice increases, the crystallographic planes of the inorganic perovskite compound exhibit vertical growth in order to facilitate efficient charge transport. Furthermore, the devices have a smaller band gap, which offers broader absorption and the potential to increase the photocurrent density in the solar cell. As a result, the photovoltaic device based on the (C_6H_5CH_2NH_2)(CH_3NH_3)_n_-_1Pb_nI_3_n_+_1 perovskite exhibits a power conversion efficiency of 5.43% with a short circuit current density of 14.49 mA cm"−"2, an open circuit voltage of 0.85 V, and a fill factor of 44.30 for the best power conversion efficiency under AM 1.5G solar irradiation (100 mW cm"−"2), which is significantly higher than the 0.34% of the pure two-dimensional BAPbI_4 perovskite-based solar cell.

  14. Estudio cinético de la descomposición térmica del carbonato de Estroncio en el sistema SrCO3-Al2O3-SrSO4

    Directory of Open Access Journals (Sweden)

    Torres T, J.

    2008-10-01

    Full Text Available The thermal decomposition of strontium carbonate in the SrCO3-Al2O3-SrSO4 system was studied by thermal analysis under isothermal experiments. Powder of reactive grade of SrCO3, Al2O3 y SrSO4 in molar ratio 3:3:1 were prepared. The powders were heat treated from 750 to 1000 °C for 4 h. Loss weight for each temperature was registered and the kinetics parameter were determine using the classical fit method. The effect of mechanical activation of SrCO3 was studied as well. The reaction mechanism for 750 to 900 °C temperature range corresponded to a geometric shrinkage in the grain boundary (R1.1 with an activation energy of 106. 21 Kjmol-1. The reaction mechanism for 900 to 1100 °C temperature range corresponded to a nucleation and growing (P1.1 with an activation energy of 44.87 Kjmol-1. The activation energy was reduced in 35% for the samples that contained SrCO3 mechanically activated.La cinética de descomposición térmica del carbonato de Estroncio (SrCO3 en el sistema SrCO3-Al2O3-SrSO4 se estudió por medio de análisis térmico gravimétrico (ATG, utilizando el método isotérmico. Se prepararon mezclas de polvos 3:3:1 molar de SrCO3, Al2O3 y SrSO4 grado reactivo, las cuales fueron homogenizadas y tratadas a temperaturas entre 750 hasta 1100°C, por periodo de 4 horas. Adicionalmente se estudio el efecto del tiempo de activación mecánica del SrCO3 sobre la cinética de descomposición. Se obtuvieron curvas representativas de la pérdida de peso de las muestras al incrementar la temperatura, a partir de ellas se realizó el estudio cinético. Para el rango de temperatura de 750 a 900°C, el mecanismo de reacción que rige el proceso de descomposición corresponde a una contracción geométrica mediante la frontera de grano (R1.1 con una energía de activación (Ea de 106.21KJmol-1. En el rango de temperatura de 950 a 1100°C, el mecanismo de reacción que rige la descomposición corresponde a un proceso de nucleación y crecimiento (P1.1

  15. Novel solid oxide cells with SrCo0.8Fe0.1Ga0.1O3-δ oxygen electrode for flexible power generation and hydrogen production

    Science.gov (United States)

    Meng, Xiuxia; Shen, Yichi; Xie, Menghan; Yin, Yimei; Yang, Naitao; Ma, Zi-Feng; Diniz da Costa, João C.; Liu, Shaomin

    2016-02-01

    This work investigates the performance of solid oxide cells as fuel cells (SOFCs) for power production and also as electrolysis cells (SOECs) for hydrogen production. In order to deliver this dual mode flexible operation system, a novel perovskite oxide based on Ga3+ doped SrCo0.8Fe0.1Ga0.1O3-δ (SCFG) is synthesized via a sol-gel method. Its performance for oxygen electrode catalyst was then evaluated. Single solid oxide cell in the configuration of Ni-YSZ|YSZ|GDC|SCFG is assembled and tested in SOFC or SOEC modes from 550 to 850 °C with hydrogen as the fuel or as the product, respectively. GDC is used to avoid the reaction between the electrolyte YSZ and the cobalt-based electrode. Under SOFC mode, a maximum power density of 1044 mW cm-2 is obtained at 750 °C. Further, the cell delivers a stable power output of 650 mW cm-2 up to 125 h at 0.7 V. In the electrolysis mode, when the applied voltage is controlled at 2 V, the electrolysis current density reaches 3.33 A cm-2 at 850 °C with the hydrogen production rate up to 22.9 mL min-1 cm-2 (STP). These results reveal that SCFG is a very promising oxygen electrode material for application in both SOFC and SOEC.

  16. Effect of 24,25-dihydroxyvitamin D3 on 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] metabolism in vitamin D-deficient rats infused with 1,25-(OH)2D3

    International Nuclear Information System (INIS)

    Yamato, H.; Matsumoto, T.; Fukumoto, S.; Ikeda, K.; Ishizuka, S.; Ogata, E.

    1989-01-01

    Previous studies revealed that administration of 24,25-dihydroxyvitamin D3 [24,25-(OH)2D3] to calcium (Ca)-deficient rats causes a dose-dependent reduction in markedly elevated serum 1,25-(OH)2D3 level. Although the results suggested that the metabolism of 1,25-(OH)2D3 was accelerated by 24,25-(OH)2D3, those experiments could not define whether the enhanced metabolism of 1,25-(OH)2D3 played a role in the reduction in the serum 1,25-(OH)2D3 level. In the present study, in order to address this issue more specifically, serum 1,25-(OH)2D3 was maintained solely by exogenous administration through miniosmotic pumps of 1,25-(OH)2D3 into vitamin D-deficient rats. Thus, by measuring the serum 1,25-(OH)2D3 concentration, the effect of 24,25-(OH)2D3 on the MCR of 1,25-(OH)2D3 could be examined. Administration of 24,25-(OH)2D3 caused a dose-dependent enhancement in the MCR of 1,25-(OH)2D3, and 1 microgram/100 g rat.day 24,25-(OH)2D3, which elevated serum 24,25-(OH)2D3 to 8.6 +/- 1.3 ng/ml, significantly increased MCR and suppressed serum levels of 1,25-(OH)2D3. The effect of 24,25-(OH)2D3 on 1,25-(OH)2D3 metabolism developed with a rapid time course, and the recovery of iv injected [1 beta-3H]1,25-(OH)2D3 in blood was significantly reduced within 1 h. In addition, there was an increase in radioactivity in the water-soluble fraction of serum as well as in urine, suggesting that 1,25-(OH)2D3 is rapidly degraded to a water-soluble metabolite(s). Furthermore, the reduction in serum 1,25-(OH)2D3 was associated with a reduction in both serum and urinary Ca levels. Because the conversion of [3H]24,25-(OH)2D3 to [3H]1,24,25-(OH)2D3 or other metabolites was minimal in these rats, 24,25-(OH)2D3 appears to act without being converted into other metabolites. These results demonstrate that 24,25-(OH)2D3 rapidly stimulates the metabolism of 1,25-(OH)2D3 and reduces its serum level

  17. Enhanced radiosensitivity in 1,25-dihydroxyvitamin D3 deficient mice

    International Nuclear Information System (INIS)

    Zhang Zengli; Ding Xiaofei; Tong Jian; Li Bingyan

    2011-01-01

    To investigate whether impaired osteogenesis resulting from vitamin D deficiency can influence hematopoiesis recovery after radiation, the 25-hydroxyvitamin D-1α-hydroxylase (1α-hydroxylase) gene knockout (KO) mice and wild type (WT) mice were subjected to different doses of gamma ray. The survival rates, peripheral blood cell counts and bone marrow cellularity were studied after irradiation (IR). The survival rates of the KO mice were significantly lower than that of WT mice after 6 or 8 Gy dose of radiation. The recovery of white blood cells in KO mice was significantly delayed compared with that in WT mice after radiation. The red blood cell number in WT mice was observed to increase more than that in KO mice at days 14 and 28 after radiation. The nadir platelet count in KO mice was nearly half of that in WT mice. Dramatically higher bone marrow cell numbers were found in WT mice compared with KO mice. Our findings demonstrate the enhanced radiosensitivity in 1,25-dihydroxyvitamin D3 (1,25-(OH) 2 D 3 ) deficient mice. (author)

  18. Synthesis, structure and chemical bonding of CaFe2−xRhxSi2 (x=0, 1.32, and 2) and SrCo2Si2

    International Nuclear Information System (INIS)

    Hlukhyy, Viktor; Hoffmann, Andrea V.; Fässler, Thomas F.

    2013-01-01

    The finding of superconductivity in Ba 0.6 K 0.4 Fe 2 As 2 put the attention on the investigation of compounds that crystallize with ThCr 2 Si 2 structure type such as AT 2 X 2 (A=alkali/alkaline earth/rare earth element; T=transition metal and X=element of the 13–15th group). In this context the silicides CaFe 2 Si 2 , CaFe 0.68(6) Rh 1.32(6) Si 2 , CaRh 2 Si 2 and SrCo 2 Si 2 have been synthesized by reaction of the elements under an argon atmosphere. Single crystals were obtained by special heat treatment in welded niobium/tantalum ampoules. The compounds were investigated by means of powder and single crystal X-ray diffraction. All compounds crystallize in the ThCr 2 Si 2 -type structure with space group I4/mmm (No. 139): a=3.939(1) Å, c=10.185(1) Å, R 1 =0.045, 85 F 2 values, 8 variable parameters for CaFe 2 Si 2 ; a=4.0590(2) Å, c=9.9390(8) Å, R 1 =0.030, 90 F 2 values, 10 variable parameters for CaFe 0.68(6) Rh 1.32(6) Si 2 ; a=4.0695(1) Å, c=9.9841(3) Å, R 1 =0.031, 114 F 2 values, 9 variable parameters for CaRh 2 Si 2 ; and a=3.974(1) Å, c=10.395(1) Å, R 1 =0.036, 95 F 2 values, 8 variable parameters for SrCo 2 Si 2 . The structure of SrCo 2 Si 2 contains isolated [Co 2 Si 2 ] 2− 2D-layers in the ab-plane whereas in CaFe 2−x Rh x Si 2 the [T 2 Si 2 ] layers (T=Fe and Rh) are interconnected along the c-axis via Si3Si bonds resulting in a three-dimentional (3D) [T 2 Si 2 ] 2− polyanions and therefore belong to the so-called collapsed form of the ThCr 2 Si 2 -type structure. The SrCo 2 Si 2 and CaRh 2 Si 2 are isoelectronic to the parent 122 iron–pnictide superconductors AeFe 2 As 2 (Ae=alkaline earth elements), whereas CaFe 2 Si 2 is a full substituted variant (As/Si) of CaFe 2 As 2 . The crystal chemistry and chemical bonding in the title compounds are discussed in terms of LMTO band structure calculations and a topological analysis using the Electron Localization Function (ELF). - Graphical abstract: The SrCo 2 Si 2 and CaFe 2−x Rh x Si

  19. Ordered perovskites with cationic vacancies. 11. System Ba/sub 2/Gd/sub 2/3/vacant/sub 1/3/U/sub 1-x/W/sub x/O/sub 6/

    Energy Technology Data Exchange (ETDEWEB)

    Wischert, W; Oelkrug, D; Schittenhelm, H J; Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

    1982-12-01

    The cation deficient polymorphic perovskites Ba/sub 2/Gd/sub 2/3/vacant/sub 1/3/UO/sub 6/ and Ba/sub 2/Gd/sub 2/3/vacant/sub 1/3/WO/sub 6/ form a continuous series of mixed crystals, which crystallize over a wide range (x = 0.1 up to 0.99) in a cubic 1:1 ordered perovskite lattice. According to the investigations of the vibrational spectra, the diffuse reflectance spectra, and the photoluminescence - opposite to isostructural perovskites wihout vacancies - different species of UO/sub 6/ and WO/sub 6/ octahedra are present. Numerous differences in properties - e.g. an orange emission colour in comparison with a green one by absence of vacancies - are based upon that.

  20. Effect of lone-electron-pair cations on the orientation of crystallographic shear planes in anion-deficient perovskites.

    Science.gov (United States)

    Batuk, Dmitry; Batuk, Maria; Abakumov, Artem M; Tsirlin, Alexander A; McCammon, Catherine; Dubrovinsky, Leonid; Hadermann, Joke

    2013-09-03

    Factors affecting the structure and orientation of the crystallographic shear (CS) planes in anion-deficient perovskites were investigated using the (Pb(1-z)Sr(z))(1-x)Fe(1+x)O(3-y) perovskites as a model system. The isovalent substitution of Sr(2+) for Pb(2+) highlights the influence of the A cation electronic structure because these cations exhibit very close ionic radii. Two compositional ranges have been identified in the system: 0.05 ≤ z ≤ 0.2, where the CS plane orientation gradually varies but stays close to (203)p, and 0.3 ≤ z ≤ 0.45 with (101)p CS planes. The incommensurately modulated structure of Pb0.792Sr0.168Fe1.040O2.529 was refined from neutron powder diffraction data using the (3 + 1)D approach (space group X2/m(α0γ), X = (1/2, 1/2, 1/2, 1/2), a = 3.9512(1) Å, b = 3.9483(1) Å, c = 3.9165(1) Å, β = 93.268(2)°, q = 0.0879(1)a* + 0.1276(1)c*, RF = 0.023, RP = 0.029, and T = 900 K). A comparison of the compounds with different CS planes indicates that the orientation of the CS planes is governed mainly by the stereochemical activity of the lone-electron-pair cations inside the perovskite blocks.

  1. Fabrication of single phase 2D homologous perovskite microplates by mechanical exfoliation

    Science.gov (United States)

    Li, Junze; Wang, Jun; Zhang, Yingjun; Wang, Haizhen; Lin, Gaoming; Xiong, Xuan; Zhou, Weihang; Luo, Hongmei; Li, Dehui

    2018-04-01

    The two-dimensional (2D) Ruddlesden-Popper type perovskites have attracted intensive interest for their great environmental stability and various potential optoelectronic applications. Fundamental understanding of the photophysical and electronic properties of the 2D perovskites with pure single phase is essential for improving the performance of the optoelectronic devices and designing devices with new architectures. Investigating the optical and electronic properties of these materials with pure single phase is required to obtain pure single phase 2D perovskites. Here, we report on an alternative approach to fabricate (C4H9NH3)2(CH3NH3) n-1Pb n I3n+1 microplates with pure single n-number perovskite phase for n  >  2 by mechanical exfoliation. Micro-photoluminescence and absorption spectroscopy studies reveal that the as-synthesized 2D perovskite plates for n  >  2 are comprised by dominant n-number phase and small inclusions of hybrid perovskite phases with different n values, which is supported by excitation power dependent photoluminescence. By mechanical exfoliation method, 2D perovskite microplates with the thickness of around 20 nm are obtained, which surprisingly have single n-number perovskite phase for n  =  2-5. In addition, we have demonstrated that the exfoliated 2D perovskite microplates can be integrated with other 2D layered materials such as boron nitride, and are able to be transferred to prefabricated electrodes for photodetections. Our studies not only provide a strategy to prepare 2D perovskites with a single n-number perovskite phase allowing us to extract the basic optical and electronic parameters of pure phase perovskites, but also demonstrate the possibility to integrate the 2D perovskites with other 2D layered materials to extend the device’s functionalities.

  2. Comparison of two different synthesis methods of perovskites, SrCo0.5FeO3 type, aiming at evaluating their use as membranes for partial oxidation of methane

    Directory of Open Access Journals (Sweden)

    Noronha F.B.

    2004-01-01

    Full Text Available In this work two different synthesis methods of perovskites, SrCo0.5FeO3, were compared: combustion synthesis and oxides mixture aiming at evaluating their use as membranes for partial oxidation of methane. The combustion synthesis method explores an exothermic, generally very fast and self-sustaining chemical reaction between the desired metal salts and a suitable organic fuel, which is ignited at a temperature much lower than the actual phase formation temperature. The oxides mixture are based on a physical mixture of the powder oxides followed by calcination to obtain the desired phase. In order to obtain the membranes, we studied the conformation of bodies and the temperatures of sintering in the two powders synthesized. The powders were analyzed by density and grain size distribution and characterized by X-ray diffraction (XRD and scanning electron microscopy (SEM. After conformation, in cylindrical form, the green bodies were analyzed by density. After sintering at 1150 °C, the membranes were analyzed by density and they were characterized by XRD and SEM. The powder obtained by combustion synthesis shows lower density and fine grains than the other obtained by oxides mixture. The membranes obtained present very different morphology depending on the precursor powder synthesis. The sintered membranes obtained by combustion method also present a very uniform morphology without segregation.

  3. Deficient by oxygen perovskites and superconductor with transition temperature 93 K

    International Nuclear Information System (INIS)

    Ross, N.L.; Angel, R.J.; Finger, L.W.; Hazen, R.M.; Prewitt, K.T.

    1988-01-01

    Structural changes in some perovskites deficient by oxygen is reviewd. The structure of the high-temperature YBa 2 Cu 3 O 7-x superconductor is shown to develop usual for perovskites properties and at the same time to possess specific features. The specific feature includes the fact that ordering of vacancies and oxygen atoms is the consequence of Ba 2+ and Y 3+ ordering in positions A. Such ordering causes the removal of oxygen atoms plane from the structure and accurrence of pyramidal-coordinated atoms Cu2 in positions B. 22 refs.; 3 figs.; 2 tabs

  4. An experimental study of perovskite-structured mixed ionic- electronic conducting oxides and membranes

    Science.gov (United States)

    Zeng, Pingying

    In recent decades, ceramic membranes based on mixed ionic and electronic conducting (MIEC) perovskite-structured oxides have received many attentions for their applications for air separation, or as a membrane reactor for methane oxidation. While numerous perovskite oxide materials have been explored over the past two decades; there are hardly any materials with sufficient practical economic value and performance for large scale applications, which justifies continuing the search for new materials. The main purposes of this thesis study are: (1) develop several novel SrCoO3-delta based MIEC oxides, SrCoCo1-xMxO3-delta, based on which membranes exhibit excellent oxygen permeability; (2) investigate the significant effects of the species and concentration of the dopants M (metal ions with fixed valences) on the various properties of these membranes; (3) investigate the significant effects of sintering temperature on the microstructures and performance of oxygen permeation membranes; and (4) study the performance of oxygen permeation membranes as a membrane reactor for methane combustion. To stabilize the cubic phase structure of the SrCoO3-delta oxide, various amounts of scandium was doped into the B-site of SrCoO 3-delta to form a series of new perovskite oxides, SrScxCoCo 1-xO3-delta (SSCx, x = 0-0.7). The significant effects of scandium-doping concentration on the phase structure, electrical conductivity, sintering performance, thermal and structural stability, cathode performance, and oxygen permeation performance of the SSCx membranes, were systematically studied. Also for a more in-depth understanding, the rate determination steps for the oxygen transport process through the membranes were clarified by theoretical and experimental investigation. It was found that only a minor amount of scandium (5 mol%) doping into the B-site of SrCoO3-delta can effectively stabilize the cubic phase structure, and thus significantly improve the electrical conductivity and

  5. Self-propagating high-temperature synthesis of Sr-doped LaMnO3 perovskite as oxidation catalyst

    International Nuclear Information System (INIS)

    Hirano, T.; Purwanto, H.; Watanabe, T.; Akiyama, T.

    2007-01-01

    Sr-doped LaMnO 3 perovskite oxide has been focused on as one of the alternative catalysts to precious metals such as platinum that are used for cleaning automotive emission gas. The conventional Solid-state reaction method is a popular productive process for perovskite oxide, however, it is time and energy consuming process because it requires repeated prolonged heat treatment at high temperatures. Therefore, the purposes of this work are to produce Sr-doped LaMnO 3 perovskite by using Self-propagating high-temperature synthesis (SHS) and experimentally examine the oxidation catalytic activity of the product for cleaning automotive emission gas. In the SHS, powders of La 2 O 3 , SrCO 3 , Mn and NaClO 4 were well mixed at the desired ratio and poured in a graphite crucible, where at one end it was ignited by using an electrically heated carbon foil. The wave of exothermic reaction due to oxidation of manganese propagated to the other end in a short time. The obtained products were characterized by means of XRD, FE-SEM, BET and particle size distribution analysis and then evaluated via catalytic oxidation tests by using propane in a fixed bed reactor at several temperatures. From the XRD analysis, the products had the desired composition of La 1-x Sr x MnO 3 (x = 0, 0.1, 0.2 and 0.4) perovskite, in which the replacing ratio x of La and Sr in the products was easily controlled by changing the mixing ratio of raw materials. The catalytic activity test showed that the samples exhibited good catalytic activity for propane oxidation over 200 deg. C , although the products had a relatively small surface area. SHS showed the potential for the production of a relatively inexpensive catalytic converter

  6. Thermodynamic modeling of the Sr-Co-Fe-O system

    DEFF Research Database (Denmark)

    Zhang, Wei Wei; Povoden-Karadeniz, Erwin; Chen, Ming

    2016-01-01

    This paper reviews and assesses phase equilibria and thermodynamic properties of phases in the Sr-Co-Fe-O system, with a focus on oxides, especially the SrCo1 - xFexO3 - δ perovskite. In our work, the SrCo1 - xFexO3 - δ perovskite was modeled with a three-sublattice model, where the three...... sublattices correspond to the A, B and oxygen sites in an ABO3 perovskite, respectively. A number of other important ternary oxide phases in Sr-Co-O and Sr-Co-Fe-O were also considered. Available thermodynamic and phase diagram data were carefully assessed. A thermodynamic description of Sr-Co-O was derived...

  7. Ordered oxygen deficient '112'perovskites, LnBaCo2 O5⋅ 50 ...

    Indian Academy of Sciences (India)

    ... Refresher Courses · Symposia · Live Streaming. Home; Journals; Bulletin of Materials Science; Volume 32; Issue 3. Ordered oxygen deficient '112' perovskites, LnBaCo2O5.50+: complex magnetism and transport properties. B Raveau Md Motin Seikh V Pralong V Caignaert. Volume 32 Issue 3 June 2009 pp 305-312 ...

  8. En route to the conductivity bottleneck in p-type CuCr1-xMxO2-ySy (M = Li, Mg)

    Science.gov (United States)

    Mandal, P.; Mazumder, N.; Akhtar, A. J.; Roy, R.; Chattopadhyay, K. K.

    2017-05-01

    We extend our material design concept [P. Mandal et al. J. Phys. D: Appl. Phys. 49, 275109, (2016); N. Mazumder et al. J. Phys. Chem. Lett. 4, 3539, (2013)] further aiming to overcome the conductivity bottleneck (1 Scm-1) in p-type transparent conducting oxide (TCO). In this work, we execute the strategy of simultaneous cationic-anionic hole doping in the prototype p-TCO CuCrO2. CuCr1-xMxO2-ySy (M = Li, Mg) is prepared by solid state heating at 1150 °C. Using Rietveld analysis, the presence of Mgcr•, Licr • and SO×areconfirmed and quantified. The diffuse reflectance (DR) spectra are acquired to determine the dominant optical gap (˜ 3.5 eV) and found to be affected little upon site selective hole doping. From temperature dependence (80 - 300 K) of DC conductivity (σdc), (Licr •+SO×)dopingcan be identified to be the more plausible alternative to reach the bottleneck threshold compared to (Mgcr •+SO×) albeit of smaller σdc at 300 K.

  9. CH3NH3Pb1-xMgxI3 perovskites as environmentally friendly photovoltaic materials

    Science.gov (United States)

    Zhang, Y. D.; Feng, J.

    2018-01-01

    In an effort to reduce the toxicity of Pb in perovskite solar cells, the band structures, electron and hole effective masses, and electronic and optical properties of the novel perovskites CH3NH3Pb1-xMgxI3 were predicted using density functional theory with the scalar relativistic generalized gradient approximation. The calculation results indicated that the introduction of the Mg component caused the band gaps of the CH3NH3Pb1-xMgxI3 compounds to exceed that of CH3NH3PbI3. The calculated absorption coefficients of the CH3NH3PbI3 and CH3NH3Pb1-xMgxI3 perovskites revealed that substituting 12.5 mol % of the Pb in CH3NH3PbI3 with Mg had little effect on the absorption ability. Surprisingly, it was also found that CH3NH3Pb0.75Mg0.25I3 retained up to 83% of the absorption performance relative to CH3NH3PbI3. This indicates that the amount of toxic Pb used in perovskite solar cells could be reduced by a quarter while retaining over 80% of the light-absorbing ability. In general, these novel CH3NH3Pb1-xMgxI3 (x ≤ 0.25) perovskites represent promising candidates for environmentally friendly light-harvesting materials for use in solar cells.

  10. The Density and Compressibility of BaCO3-SrCO3-CaCO3-K2CO3-Na2CO3-Li2CO3 Liquids: New Measurements and a Systematic Trend with Cation Field Strength

    Science.gov (United States)

    Hurt, S. M.; Lange, R. A.; Ai, Y.

    2015-12-01

    The volumetric properties of multi-component carbonate liquids are required to extend thermodynamic models that describe partial melting of the deep mantle (e.g. pMELTS; Ghiorso et al., 2003) to carbonate-bearing lithologies. Carbonate in the mantle is an important reservoir of carbon, which is released to the atmosphere as CO2 through volcanism, and thus contributes to the carbon cycle. Although MgCO3 is the most important carbonate component in the mantle, it is not possible to directly measure the 1-bar density and compressibility of MgCO3 liquid because, like other alkaline-earth carbonates, it decomposes at a temperature lower than its melting temperature. Despite this challenge, Liu and Lange (2003) and O'Leary et al. (2015) showed that the one bar molar volume, thermal expansion and compressibility of the CaCO3 liquid component could be obtained by measuring the density and sound speeds of stable liquids in the CaCO3-Li2CO3-Na2CO3-K2CO3 quaternary system at one bar. In this study, this same strategy is employed on SrCO3- and BaCO3-bearing alkali carbonate liquids. The density and sound speed of seven liquids in the SrCO3-Li2CO3-Na2CO3-K2CO3 quaternary and three liquids in the BaCO3-Li2CO3-Na2CO3-K2CO3 quaternary were measured from 739-1367K, with SrCO3 and BaCO3 concentrations ranging from 10-50 mol%. The density measurements were made using the double-bob Archimedean method and sound speeds were obtained with a frequency-sweep acoustic interferometer. The molar volume and sound speed measurements were used to calculate the isothermal compressibility of each liquid, and the results show the volumetric properties mix ideally with composition. The partial molar volume and compressibility of the SrCO3 and BaCO3 components are compared to those obtained for the CaCO3 component as a function of cation field strength. The results reveal a systematic trend that allows the partial molar volume and compressibility of the MgCO3 liquid component to be estimated.

  11. New Type of 2D Perovskites with Alternating Cations in the Interlayer Space, (C(NH 2 ) 3 )(CH 3 NH 3 ) n Pb n I 3n+1 : Structure, Properties, and Photovoltaic Performance

    Energy Technology Data Exchange (ETDEWEB)

    Soe, Chan Myae Myae; Stoumpos, Constantinos C.; Kepenekian, Mikaël; Traoré, Boubacar; Tsai, Hsinhan; Nie, Wanyi; Wang, Binghao; Katan, Claudine; Seshadri, Ram; Mohite, Aditya D.; Even, Jacky; Marks, Tobin J.; Kanatzidis, Mercouri G. (UCSB); (NWU); (LANL); (CNRS-UMR)

    2017-11-01

    We present the new homologous series (C(NH2)3)(CH3NH3)nPbnI3n+1 (n = 1, 2, 3) of layered 2D perovskites. Structural characterization by single-crystal X-ray diffraction reveals that these compounds adopt an unprecedented structure type, which is stabilized by the alternating ordering of the guanidinium and methylammonium cations in the interlayer space (ACI). Compared to the more common Ruddlesden–Popper (RP) 2D perovskites, the ACI perovskites have a different stacking motif and adopt a higher crystal symmetry. The higher symmetry of the ACI perovskites is expressed in their physical properties, which show a characteristic decrease of the bandgap with respect to their RP perovskite counterparts with the same perovskite layer thickness (n). The compounds show a monotonic decrease in the optical gap as n increases: Eg = 2.27 eV for n = 1 to Eg = 1.99 eV for n = 2 and Eg = 1.73 eV for n = 3, which show slightly narrower gaps compared to the corresponding RP perovskites. First-principles theoretical electronic structure calculations confirm the experimental optical gap trends suggesting that the ACI perovskites are direct bandgap semiconductors with wide valence and conduction bandwidths. To assess the potential of the ACI perovskites toward solar cell applications, we studied the (C(NH2)3)(CH3NH3)3Pb3I10 (n = 3) compound. Compact thin films from the (C(NH2)3)(CH3NH3)3Pb3I10 compound with excellent surface coverage can be obtained from the antisolvent dripping method. Planar photovoltaic devices from optimized ACI perovskite films yield a power-conversion-efficiency of 7.26% with a high open-circuit voltage of ~1 V and a striking fill factor of ~80%.

  12. Structure, magnetism and electronic properties in 3d-5d based double perovskite (Sr1-xYx)2FeIrO6.

    Science.gov (United States)

    Kharkwal, Kishor Chandra; Pramanik, Ashim Kumar

    2017-10-17

    The 3$d$-5$d$ based double perovskites are of current interest as they provide model system to study the interplay between electronic correlation ($U$) and spin-orbit coupling (SOC). Here we report detailed structural, magnetic and transport properties of doped double perovskite material (Sr$_{1-x}$Y$_x$)$_2$FeIrO$_6$ with $x$ $\\leq$ 0.2. With substitution of Y, system retains its original crystal structure but structural parameters modify with $x$ in nonmonotonic fashion. The magnetization data for Sr$_2$FeIrO$_6$ show antiferromagnetic type magnetic transition around 45 K, however, a close inspection in data indicates a weak magnetic phase transition around 120 K. No change of structural symmetry has been observed down to low temperature, although the lattice parameters show sudden changes around the magnetic transitions. Sr$_2$FeIrO$_6$ shows an insulating behavior over the whole temperature range which yet does not change with Y substitution. Nature of charge conduction is found to follow thermally activated Mott's variable range hopping and power law behavior for parent and doped samples, respectively. Interestingly, evolution of structural, magnetic and transport behavior in (Sr$_{1-x}$Y$_x$)$_2$FeIrO$_6$ is observed to reverse with $x$ $>$ 0.1 which is believed to arise due to change in transition metal ionic state. © 2017 IOP Publishing Ltd.

  13. Exciton Dynamics of 2D Hybrid Perovskite Nanocrystal

    Science.gov (United States)

    Guo, Rui; Zhu, Zhuan; Boulesbaa, Abdelaziz; Venkatesan, Swaminathan; Xiao, Kai; Bao, Jiming; Yao, Yan; Li, Wenzhi

    Organic-inorganic hybrid perovskites have emerged as promising materials for applications in photovoltaic and optoelectronic devices. Among the perovskites, two dimensional (2D) perovskites are of great interests due to their remarkable optical and electrical properties as well as the flexibility of material selection for the organic and inorganic moieties. In this study, we demonstrate the solution-phase growth of large square-shaped single-crystalline 2D hybrid perovskites of (C6H5C2H4 NH3) 2 PbBr4 with a few unit cells thickness. Compared to the bulk crystal, a band gap shift and new photoluminescence (PL) peak are observed from the hybrid perovskite sheets. Color of the 2D crystals can be tuned by adjusting the sheet thickness. Pump-probe spectroscopy is used to investigate the exciton dynamics and exhibits a biexponential decay with an amplitude-weighted lifetime of 16.7 ps. Such high-quality (C6H5C2H4 NH3) 2 PbBr4 sheets are expected to have high PL quantum efficiency which can be adopted for light-emitting devices. National Science Foundation (Grant No. CMMI-1334417 and DMR-1506640).

  14. Low-Threshold Lasing from 2D Homologous Organic-Inorganic Hybrid Ruddlesden-Popper Perovskite Single Crystals.

    Science.gov (United States)

    Raghavan, Chinnambedu Murugesan; Chen, Tzu-Pei; Li, Shao-Sian; Chen, Wei-Liang; Lo, Chao-Yuan; Liao, Yu-Ming; Haider, Golam; Lin, Cheng-Chieh; Chen, Chia-Chun; Sankar, Raman; Chang, Yu-Ming; Chou, Fang-Cheng; Chen, Chun-Wei

    2018-05-09

    Organic-inorganic hybrid two-dimensional (2D) perovskites have recently attracted great attention in optical and optoelectronic applications due to their inherent natural quantum-well structure. We report the growth of high-quality millimeter-sized single crystals belonging to homologous two-dimensional (2D) hybrid organic-inorganic Ruddelsden-Popper perovskites (RPPs) of (BA) 2 (MA) n-1 Pb n I 3 n+1 ( n = 1, 2, and 3) by a slow evaporation at a constant-temperature (SECT) solution-growth strategy. The as-grown 2D hybrid perovskite single crystals exhibit excellent crystallinity, phase purity, and spectral uniformity. Low-threshold lasing behaviors with different emission wavelengths at room temperature have been observed from the homologous 2D hybrid RPP single crystals. Our result demonstrates that solution-growth homologous organic-inorganic hybrid 2D perovskite single crystals open up a new window as a promising candidate for optical gain media.

  15. CH3NH3Pb1−xMgxI3 perovskites as environmentally friendly photovoltaic materials

    Directory of Open Access Journals (Sweden)

    Y. D. Zhang

    2018-01-01

    Full Text Available In an effort to reduce the toxicity of Pb in perovskite solar cells, the band structures, electron and hole effective masses, and electronic and optical properties of the novel perovskites CH3NH3Pb1−xMgxI3 were predicted using density functional theory with the scalar relativistic generalized gradient approximation. The calculation results indicated that the introduction of the Mg component caused the band gaps of the CH3NH3Pb1−xMgxI3 compounds to exceed that of CH3NH3PbI3. The calculated absorption coefficients of the CH3NH3PbI3 and CH3NH3Pb1−xMgxI3 perovskites revealed that substituting 12.5 mol % of the Pb in CH3NH3PbI3 with Mg had little effect on the absorption ability. Surprisingly, it was also found that CH3NH3Pb0.75Mg0.25I3 retained up to 83% of the absorption performance relative to CH3NH3PbI3. This indicates that the amount of toxic Pb used in perovskite solar cells could be reduced by a quarter while retaining over 80% of the light-absorbing ability. In general, these novel CH3NH3Pb1−xMgxI3 (x ≤ 0.25 perovskites represent promising candidates for environmentally friendly light-harvesting materials for use in solar cells.

  16. Energy transfer mechanisms in layered 2D perovskites.

    Science.gov (United States)

    Williams, Olivia F; Guo, Zhenkun; Hu, Jun; Yan, Liang; You, Wei; Moran, Andrew M

    2018-04-07

    Two-dimensional (2D) perovskite quantum wells are generating broad scientific interest because of their potential for use in optoelectronic devices. Recently, it has been shown that layers of 2D perovskites can be grown in which the average thicknesses of the quantum wells increase from the back to the front of the film. This geometry carries implications for light harvesting applications because the bandgap of a quantum well decreases as its thickness increases. The general structural formula for the 2D perovskite systems under investigation in this work is (PEA) 2 (MA) n-1 [Pb n I 3n+1 ] (PEA = phenethyl ammonium, MA = methyl ammonium). Here, we examine two layered 2D perovskites with different distributions of quantum well thicknesses. Spectroscopic measurements and model calculations suggest that both systems funnel electronic excitations from the back to the front of the film through energy transfer mechanisms on the time scales of 100's of ps (i.e., energy transfer from thinner to thicker quantum wells). In addition, the model calculations demonstrate that the transient absorption spectra are composed of a progression of single exciton and biexciton resonances associated with the individual quantum wells. We find that exciton dissociation and/or charge transport dynamics make only minor contributions to the transient absorption spectra within the first 1 ns after photo-excitation. An analysis of the energy transfer kinetics indicates that the transitions occur primarily between quantum wells with values of n that differ by 1 because of the spectral overlap factor that governs the energy transfer rate. Two-dimensional transient absorption spectra reveal a pattern of resonances consistent with the dominance of sequential energy transfer dynamics.

  17. Energy transfer mechanisms in layered 2D perovskites

    Science.gov (United States)

    Williams, Olivia F.; Guo, Zhenkun; Hu, Jun; Yan, Liang; You, Wei; Moran, Andrew M.

    2018-04-01

    Two-dimensional (2D) perovskite quantum wells are generating broad scientific interest because of their potential for use in optoelectronic devices. Recently, it has been shown that layers of 2D perovskites can be grown in which the average thicknesses of the quantum wells increase from the back to the front of the film. This geometry carries implications for light harvesting applications because the bandgap of a quantum well decreases as its thickness increases. The general structural formula for the 2D perovskite systems under investigation in this work is (PEA)2(MA)n-1[PbnI3n+1] (PEA = phenethyl ammonium, MA = methyl ammonium). Here, we examine two layered 2D perovskites with different distributions of quantum well thicknesses. Spectroscopic measurements and model calculations suggest that both systems funnel electronic excitations from the back to the front of the film through energy transfer mechanisms on the time scales of 100's of ps (i.e., energy transfer from thinner to thicker quantum wells). In addition, the model calculations demonstrate that the transient absorption spectra are composed of a progression of single exciton and biexciton resonances associated with the individual quantum wells. We find that exciton dissociation and/or charge transport dynamics make only minor contributions to the transient absorption spectra within the first 1 ns after photo-excitation. An analysis of the energy transfer kinetics indicates that the transitions occur primarily between quantum wells with values of n that differ by 1 because of the spectral overlap factor that governs the energy transfer rate. Two-dimensional transient absorption spectra reveal a pattern of resonances consistent with the dominance of sequential energy transfer dynamics.

  18. CO2 absorption of perovskites as seen by positron lifetime spectroscopy

    International Nuclear Information System (INIS)

    Suevegh, K.; Nomura, K.; Juhasz, G.; Homonnay, Z.; Vertes, A.

    2000-01-01

    The CO 2 absorption of several ABO 3 type perovskites was studied by positron lifetime spectroscopy. The longer positron lifetime was associated with positrons trapped by A site vacancies. The evaluated positron lifetime data indicated the relative stability of the crystal structure of Sr(Co 0.5 Fe 0.5 )O 3-δ against Ca doping at low Ca concentrations. Oxygen desorption and CO 2 absorption/desorption could also be followed by positron lifetime spectroscopy. It was shown that the concentration of oxygen vacancies has a large effect on positron lifetime data through the electron density of A site vacancies.

  19. Characterization of the Valence and Conduction Band Levels of n = 1 2D Perovskites: A Combined Experimental and Theoretical Investigation

    KAUST Repository

    Silver, Scott

    2018-02-13

    This study presents a combined experimental and theoretical study of the electronic structure of two 2D metal halide perovskite films. Ultraviolet and inverse photoemission spectroscopies are performed on solution-processed thin films of the n = 1 layered perovskite butylammonium lead iodide and bromide, BA2PbI4 and BA2PbBr4, characterized by optical absorption and X-ray diffraction, to determine their valence and conduction band densities of states, transport gaps, and exciton binding energies. The electron spectroscopy results are compared with the densities of states determined by density functional theory calculations. The remarkable agreement between experiment and calculation enables a detailed identification and analysis of the organic and inorganic contributions to the valence and conduction bands of these two hybrid perovskites. The electron affinity and ionization energies are found to be 3.1 and 5.8 eV for BA2PbI4, and 3.1 and 6.5 eV for BA2PbBr4. The exciton binding energies are estimated to be 260 and 300 meV for the two materials, respectively. The 2D lead iodide and bromide perovskites exhibit significantly less band dispersion and a larger density of states at the band edges than the 3D analogs. The effects of using various organic ligands are also discussed.

  20. Structure, magnetism and electronic properties in 3d-5d based double perovskite ({Sr_{1-x}} Y x )2FeIrO6

    Science.gov (United States)

    Kharkwal, K. C.; Pramanik, A. K.

    2017-12-01

    The 3d-5d based double perovskites are of current interest as they provide model systems to study the interplay between electronic correlation (U) and spin-orbit coupling (SOC). Here, we report detailed structural, magnetic and transport properties of doped double perovskite material (Sr1-x Y x )2FeIrO6 with x ≤slant 0.2 . With substitution of Y, the system retains its original crystal structure but structural parameters change with x in nonmonotonic fashion. The magnetization data for Sr2FeIrO6 show antiferromagnetic type magnetic transition around 45 K however, a close inspection of the data indicates a weak magnetic phase transition around 120 K. No change of structural symmetry has been observed down to low temperature, although the lattice parameters show sudden changes around the magnetic transitions. Sr2FeIrO6 shows an insulating behavior over the whole temperature range, which nevertheless does not change with Y substitution. The nature of charge conduction is found to follow thermally activated Mott’s variable range hopping and power law behavior for parent and doped samples, respectively. Interestingly, evolution of structural, magnetic and transport behavior in (Sr1-x Y x )2FeIrO6 is observed to reverse with x > 0.1 , which is believed to arise due to a change in the transition metal ionic state.

  1. Impact of CD1d deficiency on metabolism.

    Directory of Open Access Journals (Sweden)

    Maya E Kotas

    Full Text Available Invariant natural killer T cells (iNKTs are innate-like T cells that are highly concentrated in the liver and recognize lipids presented on the MHC-like molecule CD1d. Although capable of a myriad of responses, few essential functions have been described for iNKTs. Among the many cell types of the immune system implicated in metabolic control and disease, iNKTs seem ideally poised for such a role, yet little has been done to elucidate such a possible function. We hypothesized that lipid presentation by CD1d could report on metabolic status and engage iNKTs to regulate cellular lipid content through their various effector mechanisms. To test this hypothesis, we examined CD1d deficient mice in a variety of metabolically stressed paradigms including high fat feeding, choline-deficient feeding, fasting, and acute inflammation. CD1d deficiency led to a mild exacerbation of steatosis during high fat or choline-deficient feeding, accompanied by impaired hepatic glucose tolerance. Surprisingly, however, this phenotype was not observed in Jα18⁻/⁻ mice, which are deficient in iNKTs but express CD1d. Thus, CD1d appears to modulate some metabolic functions through an iNKT-independent mechanism.

  2. Electrochemical reduction of nitrous oxide on La1-xSrxFeO3 perovskites

    DEFF Research Database (Denmark)

    Kammer Hansen, Kent

    2010-01-01

    The electrochemical reduction of nitrous oxide and oxygen has been studied on cone-shaped electrodes of La1-xSrxFeO3-delta perovskites in an all solid state cell, using cyclic voltammetry. It was shown that the activity of the La1-xSrxFeO3-delta perovskites for the electrochemical reduction...... of nitrous oxide mainly depends on the amount of Fe(III) and oxide ion vacancies. The activity of the La1-xSrxFeO3-delta perovskites towards the electrochemical reduction of nitrous oxide is much lower than the activity of the La1-xSrxFeO3-delta perovskites towards the electrochemical reduction of oxygen...

  3. Studies on absorption, distribution, excretion and metabolism of 3H-1α-hydroxycholecalciferol in vitamin D deficient rats

    International Nuclear Information System (INIS)

    Tohira, Yasuo; Hinohara, Yoshikazu; Kamiyama, Hiroshi; Ogawa, Machiko; Nakano, Hideki

    1978-01-01

    The absorption, distribution, excretion and metabolism of 2- 3 H-1α-OH-D 3 (4.2 Ci/mmol) were studied in vitamin D deficient rats in comparison with the normal rats after oral or intravenous dosing. (1) Maximum blood level of administered radioactivity was observed at 8 hours after oral administration with apparent half life of 3.8 days. This blood level was higher than that in normal rat. (2) As in the normal rat, administered radioactivity was distributed relatively high in the liver, while any other specific distribution or accumulation was not observed in the another tissues, which was consistent to the finding in the normal rat. The tissue levels of the radioactivity were higher than these in the normal rat. (3) Urinary excretion of administered radioactivity was significantly higher, fecal and biliary excretion was significantly lower than that in the normal rat after intravenous dosing. (4) Relative percentage of 3 H-1α, 25-(OH) 2 -D 3 content to 3 H-1α-OH-D 3 content in tissues and blood was higher than that in the normal one. Above results suggest that in the vitamin D deficient state, the tissue accumulation of 1α-OH-D 3 was significantly augmented than in the normal rat, thus resulting increased bioavailability of its active metabolite, 1α, 25-(OH) 2 -D 3 . (author)

  4. Phase transformation of Ca-perovskite in MORB at D" region

    Science.gov (United States)

    Nishitani, N.; Ohtani, E.; Sakai, T.; Kamada, S.; Miyahara, M.; Hirao, N.

    2012-12-01

    Seismological studies indicate the presence of seismic anomalies in the Earth's deep interior. To investigate the anomaly, the physical property of the major minerals in lower mantle such as MgSiO3-perovskite, MgSiO3 post-perovskite and MgO periclase were studied well. Other candidate, CaSiO3 perovskite (Ca-perovskite) exists in peridotitic mantle and basaltic oceanic crust (mid-ocean ridge basalt; MORB). Previous studies indicate the abundance of Ca-perovskite is up to ~9 vol.% in the pyrolite mantle and ~24 vol.% in the MORB oceanic crust. However, the pressure range of previous works are still not enough to understand the D" region. In this study, natural MORB was compressed in double sided laser heated DAC. Au was used as a pressure maker and a laser absorber. NaCl was used as the thermal insulator and pressure medium. The phase relation of Ca-perovskite in MORB was investigated from 36 to 156 GPa and 300 to 2600 K by the in situ X-ray diffraction measurements at SPring-8 (BL10XU). The transition of Ca-perovskite from a tetragonal structure to a cubic structure occurred at about 1800 K up to about 100 GPa and below 1500 K at pressures above 100 GPa. This suggests that the tetragonal-cubic transition of Ca-perovskite could occur in MORB, associating with Al2O3 contents. The present results suggest that the seismic anomaly at D" layer could be caused by the transition in Ca-perovskite.

  5. Fragility of ferromagnetic double exchange interactions and pressure tuning of magnetism in 3 d -5 d double perovskite Sr2FeOsO6

    Science.gov (United States)

    Veiga, L. S. I.; Fabbris, G.; van Veenendaal, M.; Souza-Neto, N. M.; Feng, H. L.; Yamaura, K.; Haskel, D.

    2015-06-01

    The ability to tune exchange (magnetic) interactions between 3 d transition metals in perovskite structures has proven to be a powerful route to discovery of novel properties. Here we demonstrate that the introduction of 3 d -5 d exchange pathways in double perovskites enables additional tunability, a result of the large spatial extent of 5 d wave functions. Using x-ray probes of magnetism and structure at high pressure, we show that compression of Sr2FeOsO6 drives an unexpected continuous change in the sign of Fe-Os exchange interactions and a transition from antiferromagnetic to ferrimagnetic order. We analyze the relevant electron-electron interactions, shedding light into fundamental differences with the more thoroughly studied 3 d -3 d systems.

  6. Experimental autoabsorption curve 90Sr in SrCO3. Efficiency calculation to detection of 90Sr, 90Y and 90Sr + 90Y in a beta gas proportional counter

    International Nuclear Information System (INIS)

    Gasco, C.; Alvarez, A.

    1987-01-01

    Strontium-90 has been determined by radiochemical separation techniques in environmental samples. These techniques, of course, cannot separate the two strontium radionuclides from each other of from stable strontium. Consequently the end product of the chemical separation contains all strontium isotopes in SrCO 3 . The beta particules emitted by 90 Sr are absorbed by the SrCO 3 precipitate. This is the main source of error in the activity measurement. It has been prepared sources of 90 Sr in SrCO 3 in order to determinate the counting efficiency and autoabsorption curve. Also detection efficiencies have been calibrated using known activities of 90 Y and equilibrium mixture of 90 Sr+ 90 Y in the same geometry than our samples. The activity of 90 Sr by ingrowth of 90 Y has been calculated by our computer program. (author). 2 figs., 3 refs

  7. Oxygen permeability of perovskite-type BaBi1-xLaxO3

    International Nuclear Information System (INIS)

    Yaremchenko, A.A.; Kharton, V.V.; Viskup, A.P.; Naumovich, E.N.; Samokhval, V.V.

    1998-01-01

    Oxygen permeability, electrical conductivity, and thermal expansion of BaBi 1-x La x O 3-δ (x = 0, 0.2, and 0.4) perovskite-like solid solutions have been found to decrease with lanthanum content. Thermal expansion coefficients of the ceramics are (11.9--12.8) x 10 -6 K -1 . Oxygen transport through the BaBi(La)O 3-δ dense ceramic membranes within the membrane thickness range of 0.6 < d < 1.2 mm has been shown to be limited by both bulk ionic conductivity and surface exchange rate

  8. Strontium isotope fractionation during strontianite (SrCO3) dissolution, precipitation and at equilibrium

    Science.gov (United States)

    Mavromatis, Vasileios; Harrison, Anna L.; Eisenhauer, Anton; Dietzel, Martin

    2017-12-01

    In this study we examine the behavior of stable Sr isotopes between strontianite [SrCO3] and reactive fluid during mineral dissolution, precipitation, and at chemical equilibrium. Experiments were performed in batch reactors at 25 °C in 0.01 M NaCl solutions wherein the pH was adjusted by bubbling of a water saturated gas phase of pure CO2 or atmospheric air. The equilibrium Sr isotope fractionation between strontianite and fluid after dissolution of the solid under 1 atm CO2 atmosphere was estimated as Δ88/86SrSrCO3-fluid = δ88/86Sr SrCO3 - δ88/86Srfluid = -0.05 ± 0.01‰. On the other hand, during strontianite precipitation, an enrichment of the fluid phase in 88Sr, the heavy isotopomer, was observed. The evolution of the δ88/86Srfluid during strontianite precipitation can be modeled using a Rayleigh distillation approach and the estimated, kinetically driven, fractionation factor αSrCO3-fluid between solid and fluid is calculated to be 0.99985 ± 0.00003 corresponding to Δ88/86SrSrCO3-fluid = -0.15‰. The obtained results further support that under chemical equilibrium conditions between solid and fluid a continuous exchange of isotopes occurs until the system approaches isotopic equilibrium. This isotopic exchange is not limited to the outer surface layer of the strontianite crystal, but extends to ∼7-8 unit cells below the crystal surface. The behavior of Sr isotopes in this study is in excellent agreement with the concept of dynamic equilibrium and it suggests that the time needed for achievement of chemical equilibrium is generally shorter compared to that for isotopic equilibrium. Thus it is suggested that in natural Sr-bearing carbonates an isotopic change may still occur close to thermodynamic equilibrium, despite no observable change in aqueous elemental concentrations. As such, a secondary and ongoing change of Sr isotope signals in carbonate minerals caused by isotopic re-equilibration with fluids has to be considered in order to use Sr

  9. CO sub 2 absorption of perovskites as seen by positron lifetime spectroscopy

    CERN Document Server

    Suevegh, K; Juhasz, G; Homonnay, Z; Vertes, A

    2000-01-01

    The CO sub 2 absorption of several ABO sub 3 type perovskites was studied by positron lifetime spectroscopy. The longer positron lifetime was associated with positrons trapped by A site vacancies. The evaluated positron lifetime data indicated the relative stability of the crystal structure of Sr(Co sub 0 sub . sub 5 Fe sub 0 sub . sub 5)O sub 3 sub - subdelta against Ca doping at low Ca concentrations. Oxygen desorption and CO sub 2 absorption/desorption could also be followed by positron lifetime spectroscopy. It was shown that the concentration of oxygen vacancies has a large effect on positron lifetime data through the electron density of A site vacancies.

  10. Synthesis, Single Crystal Growth, and Properties of Cobalt Deficient Double Perovskite EuBaCo2−xO6−δ (x = 0–0.1

    Directory of Open Access Journals (Sweden)

    S. V. Telegin

    2017-01-01

    Full Text Available The cobalt deficient double perovskites EuBaCo2−xO6−δ with x=0–0.1 were obtained both as powders and as single crystal. Formation of cobalt vacancies in their crystal lattice was shown to be accompanied by the formation of oxygen ones. Chemical lattice strain caused by this cooperative disordering of cobalt and oxygen sublattices was found to be isotropic contrary to that caused by the formation of oxygen vacancies only. Cobalt deficiency was also shown to lead to lowering overall conductivity and Seebeck coefficient of EuBaCo2−xO6−δ double perovskites as a result of simultaneous decrease of charge carriers’ concentration and their mobility as well as number of sites available for electrons and holes transfer. Strong anisotropy of the overall conductivity of the single crystal double perovskites EuBaCo2−xO6−δ was found and explained on the basis of preferential location of oxygen vacancies in the rare-earth-oxygen- (REO- planes.

  11. Pulsed laser deposition of {CeO_2} and {Ce_{1-x}M_xO_2} (M = La, Zr): Application to insulating barrier in cuprate heterostructures

    Science.gov (United States)

    Berger, S.; Contour, J.-P.; Drouet, M.; Durand, O.; Khodan, A.; Michel, D.; Régi, F.-X.

    1998-03-01

    SrTiO_3 had been often tentatively used as an insulating barrier for HT superconductor/insulator heterostructures. Unfortunately, the deposition of SrTiO_3 on the YBa_2Cu_3O_7 inverse interface results in a poor epitaxial regrowth producing a high roughness dislocated titanate layer. Taking into account the good matching with YBa_2Cu_3O_7 and LaAlO_3, CeO_2 and Ce_{1-x}M_xO_2 (M = La, Zr), epitaxial layers were grown by pulsed laser deposition on LaAlO_3 substrates and introduced into YBa_2Cu_3O_7 based heterostructures as insulating barrier. After adjusting the growth parameters from RHEED oscillations, epitaxial growth is achieved, the oxide crystal axes being rotated by 45^circ from those of the substrate. The surface roughness of 250 nm thick films is very low with a rms value lower than 0.5 nm over 1;μ m^2. The YBa_2Cu_3O_7 layers of a YBa_2Cu_3O_7/CeO_2 /YBa_2Cu_3O_7 heterostructures grown using these optimized parameters show an independent resistive transition, when the thickness is larger than 25 nm, respectively at T_c_1 = 89.6;K and T_c_2 = 91.4;{K}. SrTiO3 est souvent utilisé comme barrière isolante dans des hétérostructures SIS de cuprates supraconducteurs, cependant les défauts générés lors de la croissance de ce titanate sur l'interface inverse de YBa2Cu3O7 conduisent à un matériau dont la qualité cristalline et les propriétés physiques sont médiocres. L'oxyde de cérium CeO2 est également une barrière isolante potentielle intéressante pour ces structures SIS basées sur YBa2Cu3O7 car cet oxyde cubique (a = 0,5411 nm, asqrt{2}/2 = 0,3825 nm) qui est peu désaccordé par rapport au plan ab du cuprate (Δ a/a = - 0,18 %, Δ b/a = 1,6 %) présente de plus un coefficient de dilatation thermique (10,6 × 10^{-6 circ}C^{-1}) très voisin de celui de YBa2Cu3O7 (13 × 10^{-6 circ}C^{-1}). Nous avons donc étudié l'épitaxie de CeO2 et des oxydes de type Ce{1-x}MxO2 (M = La, Zr) en ablation laser pulsée afin de définir des conditions de

  12. Characterization of vitamin D-deficient klotho(-/-) mice: do increased levels of serum 1,25(OH)2D3 cause disturbed calcium and phosphate homeostasis in klotho(-/-) mice?

    NARCIS (Netherlands)

    Woudenberg-Vrenken, T.E.; van der Eerden, B.C.; van der Kemp, A.W.; Leeuwen, J.P. van; Bindels, R.J.M.; Hoenderop, J.G.J.

    2012-01-01

    BACKGROUND: Klotho(-/-) mice display disturbed Ca(2+) and vitamin D homeostasis. Renal cytochrome p450 27b1 (Cyp27b1), the enzyme that catalyzes the hydrolysis to 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), is increased in klotho(-/-) mice, and a 1,25(OH)(2)D(3)-deficient diet partially normalized

  13. Displacement-type ferroelectric transition with magnetic Mn ions in perovskite Sr1-xBaxMnO3

    Science.gov (United States)

    Sakai, Hideaki; Fujioka, Jun; Fukuda, Tatsuo; Okuyama, Daisuke; Hashizume, Daisuke; Kagawa, Fumitaka; Nakao, Hironori; Murakami, Youich; Arima, Takahisa; Baron, Alfred Q. R.; Taguchi, Yasujiro; Tokura, Yoshinori

    2012-02-01

    Almost all the proper ferroelectrics with a perovskite structure discovered so far have no d-electrons in the off-center transition metal site, as exemplified by BaTiO3 and Pb(Zr,Ti)O3. This empirical d^0 rule is incompatible with the emergence of magnetism and has significantly restricted the variety of multiferroic materials. In this work, we have discovered a displacement-type ferroelectric transition originating from off-center Mn^4+ ions in antiferromagnetic Mott insulators Sr1-xBaxMnO3. As Ba concentration increases, the perovskite lattice shows the typical soft mode dynamics, and the ferroelectricity shows up for x .45. In addition to the large polarization and high transition temperature comparable to BaTiO3, we demonstrate that the magnetic order suppresses the ferroelectric lattice dilation by ˜70% and increases the soft-phonon energy by ˜50%, indicating gigantic magnetoelectric effects [1]. This work was supported by the FIRST program on ``Quantum Science on Strong Correlation''. [4pt] [1] H. Sakai et al., Phys. Rev. Lett. 107, 137601 (2011).

  14. Cerium luminescence in nd0 perovskites

    International Nuclear Information System (INIS)

    Setlur, A.A.; Happek, U.

    2010-01-01

    The luminescence of Ce 3+ in perovskite (ABO 3 ) hosts with nd 0 B-site cations, specifically Ca(Hf,Zr)O 3 and (La,Gd)ScO 3 , is investigated in this report. The energy position of the Ce 3+ excitation and emission bands in these perovskites is compared to those of typical Al 3+ perovskites; we find a Ce 3+ 5d 1 centroid shift and Stokes shift that are larger versus the corresponding values for the Al 3+ perovskites. It is also shown that Ce 3+ luminescence quenching is due to Ce 3+ photoionization. The comparison between these perovskites shows reasonable correlations between Ce 3+ luminescence quenching, the energy position of the Ce 3+ 5d 1 excited state with respect to the host conduction band, and the host composition. - Graphical abstract: Ce 3+ decay times versus temperature for perovskites with nd 0 B-site cations.

  15. 3d-metal doping (Fe,Co,Ni,Zn) of the high Tc perovskite YBa2Cu3O(7-y)

    International Nuclear Information System (INIS)

    Tarascon, J.M.; Barboux, P.; Greene, L.H.; Hull, G.W.; Bagley, B.G.

    1988-01-01

    The structural, magnetic and superconducting properties of the mixed compounds YBa 2 Cu(3-x)M(x)O(7-y) (M = Ni,Zn,Fe, and Co) are reported. Values of y, determined by titration, are found to be dependent on the nature and amount of the doping. The range of solubility is greater for the Fe and Co compounds (x = 1) than for those with Ni or Zn (x = 0.3). The undoped material is orthorhombic and remains orthorhombic after substitution for Cu by Ni or Zn, whereas a tetragonal phase is observed when Fe, Co are substituted for Cu. DC resistance and AC susceptibility measurements show that Tc is depressed from 90K (x = 0) to 45K (x = 0.2) for both the Ni- and Zn-doped compounds, and Tc is destroyed in the Fe- and Co-doped compounds when x reaches 0.4. It is suggested that a valence of two be assigned to the Ni and Zn and three to the Fe and Co ions. 8 references

  16. Chemical Substitution-Induced and Competitive Formation of 6H and 3C Perovskite Structures in Ba3-xSrxZnSb2O9: The Coexistence of Two Perovskites in 0.3 ≤ x ≤ 1.0.

    Science.gov (United States)

    Li, Jing; Jiang, Pengfei; Gao, Wenliang; Cong, Rihong; Yang, Tao

    2017-11-20

    6H and 3C perovskites are important prototype structures in materials science. We systemically studied the structural evolution induced by the Sr 2+ -to-Ba 2+ substitution to the parent 6H perovskite Ba 3 ZnSb 2 O 9 . The 6H perovskite is only stable in the narrow range of x ≤ 0.2, which attributes to the impressibility of [Sb 2 O 9 ]. The preference of 90° Sb-O-Sb connection and the strong Sb 5+ -Sb 5+ electrostatic repulsion in [Sb 2 O 9 ] are competitive factors to stabilize or destabilize the 6H structure when chemical pressure was introduced by Sr 2+ incorporation. Therefore, in the following, a wide two-phase region containing 1:2 ordered 6H-Ba 2.8 Sr 0.2 ZnSb 2 O 9 and rock-salt ordered 3C-Ba 2 SrZnSb 2 O 9 was observed (0.3 ≤ x ≤ 1.0). In the final, the successive symmetry descending was established from cubic (Fm3̅m, 1.3 ≤ x ≤ 1.8) to tetragonal (I4/m, 2.0 ≤ x ≤ 2.4), and finally to monoclinic (I2/m, 2.6 ≤ x ≤ 3.0). Here we proved that the electronic configurations of B-site cations, with either empty, partially, or fully filled d-shell, would also affect the structure stabilization, through the orientation preference of the B-O covalent bonding. Our investigation gives a deeper understanding of the factors to the competitive formation of perovskite structures, facilitating the fine manipulation on their physical properties.

  17. Nature of potential barrier in (Ca 1/4,Cu 3/4)TiO 3 polycrystalline perovskite

    Science.gov (United States)

    Marques, V. P. B.; Bueno, P. R.; Simões, A. Z.; Cilense, M.; Varela, J. A.; Longo, E.; Leite, E. R.

    2006-04-01

    The nonohmic electrical features of (Ca 1/4,Cu 3/4)TiO 3 perovskite ceramics, which have very strong gigantic dielectric is believed originate from potential barriers at the grain boundaries. In the present study, we used the admittance and impedance spectroscopy technique to investigate (Ca 1/4,Cu 3/4)TiO 3 perovskite ceramics with low nonohmic electrical properties. The study was conducted under two different conditions: on as-sintered ceramics and on ceramics thermally treated in an oxygen-rich atmosphere. The results confirm that thermal treatment in oxygen-rich atmospheres influence the nonohmic properties. Annealing at oxygen-rich atmospheres improve the nonohmic behavior and annealing at oxygen-poor atmospheres decrease the nonohmic properties, a behavior already reported for common metal oxide nonohmic devices and here firstly evidenced for the (Ca 1/4,Cu 3/4)TiO 3 perovskite related materials. The results show that oxygen also influences the capacitance values at low frequencies, a behavior that is indicative of the Schottky-type nature of the potential barrier.

  18. High-dose vitamin D3 reduces deficiency caused by low UVB exposure and limits HIV-1 replication in urban Southern Africans

    Science.gov (United States)

    Coussens, Anna K.; Naude, Celeste E.; Goliath, Rene; Chaplin, George; Wilkinson, Robert J.; Jablonski, Nina G.

    2015-06-01

    Cape Town, South Africa, has a seasonal pattern of UVB radiation and a predominantly dark-skinned urban population who suffer high HIV-1 prevalence. This coexistent environmental and phenotypic scenario puts residents at risk for vitamin D deficiency, which may potentiate HIV-1 disease progression. We conducted a longitudinal study in two ethnically distinct groups of healthy young adults in Cape Town, supplemented with vitamin D3 in winter, to determine whether vitamin D status modifies the response to HIV-1 infection and to identify the major determinants of vitamin D status (UVB exposure, diet, pigmentation, and genetics). Vitamin D deficiency was observed in the majority of subjects in winter and in a proportion of individuals in summer, was highly correlated with UVB exposure, and was associated with greater HIV-1 replication in peripheral blood cells. High-dosage oral vitamin D3 supplementation attenuated HIV-1 replication, increased circulating leukocytes, and reversed winter-associated anemia. Vitamin D3 therefore presents as a low-cost supplementation to improve HIV-associated immunity.

  19. Thermodynamic modeling of the Sr-Co-Fe-O system

    DEFF Research Database (Denmark)

    Zhang, Wei Wei; Povoden-Karadeniz, Erwin; Chen, Ming

    2016-01-01

    This paper reviews and assesses phase equilibria and thermodynamic properties of phases in the Sr-Co-Fe-O system, with a focus on oxides, especially the SrCo1 - xFexO3 - δ perovskite. In our work, the SrCo1 - xFexO3 - δ perovskite was modeled with a three-sublattice model, where the three...... sublattices correspond to the A, B and oxygen sites in an ABO3 perovskite, respectively. A number of other important ternary oxide phases in Sr-Co-O and Sr-Co-Fe-O were also considered. Available thermodynamic and phase diagram data were carefully assessed. A thermodynamic description of Sr-Co-O was derived...... using the CALPHAD approach and was further extrapolated to that of Sr-Co-Fe-O. The thermodynamic database of Sr-Co-Fe-O established in this work allows for calculating phase diagrams, thermodynamic properties, cation distribution and defect chemistry properties, and therefore enables material...

  20. Shell model for BaTiO3-Bi(Zn1/2Ti1/2)O3 perovskite solid solutions

    Science.gov (United States)

    Vielma, J.; Jackson, D.; Roundy, D.; Schneider, G.

    2010-03-01

    Even though the composition of BaTiO3-Bi(Zn1/2Ti1/2)O3 perovskite solid solutions is similar to other ferroelectric compounds, the dielectric response is unusual. Results of permittivity measurements as a function of temperature show a diffuse phase transition indicative of a weakly coupled relaxor behavior.footnotetextC. C. Huang and D. P. Cann, J. Appl. Phys. 104, 024117 (2008) To investigate the weakly coupled relaxor behavior in these materials at intermediate length scales we are developing a newly calibrated shell model based on first-principles supercell calculations of both the solid solution and its compositional endpoints. Initial results for its phase diagram will presented.

  1. Photoresponse of CsPbBr3 and Cs4PbBr6 Perovskite Single Crystals.

    Science.gov (United States)

    Cha, Ji-Hyun; Han, Jae Hoon; Yin, Wenping; Park, Cheolwoo; Park, Yongmin; Ahn, Tae Kyu; Cho, Jeong Ho; Jung, Duk-Young

    2017-02-02

    High-quality and millimeter-sized perovskite single crystals of CsPbBr 3 and Cs 4 PbBr 6 were prepared in organic solvents and studied for correlation between photocurrent generation and photoluminescence (PL) emission. The CsPbBr 3 crystals, which have a 3D perovskite structure, showed a highly sensitive photoresponse and poor PL signal. In contrast, Cs 4 PbBr 6 crystals, which have a 0D perovskite structure, exhibited more than 1 order of magnitude higher PL intensity than CsPbBr 3 , which generated an ultralow photoresponse under illumination. Their contrasting optoelectrical characteristics were attributed to different exciton binding energies, induced by coordination geometry of the [PbBr 6 ] 4- octahedron sublattices. This work correlated the local structures of lead in the primitive perovskite and its derivatives to PL spectra as well as photoconductivity.

  2. Optically stimulated luminescence properties of Tm3+ doped KMgF3 fluoro perovskite

    International Nuclear Information System (INIS)

    Camargo, L.; Marcazzo, J.; Perez C, L.; Cruz Zaragoza, E.; Martinez O, S. A.

    2017-10-01

    In this work the optically stimulated luminescence (OSL) properties of undoped and Tm 3+ doped KMgF 3 fluoro perovskite have been investigated for the first time. OSL efficiency for stimulation with different wavelengths has been analyzed for each compound. The maximum OSL emission was found with blue light stimulation. The radioluminescence (Rl) spectra have shown two emission peaks at 455 and 360 nm, which can be ascribed to the 1 D 2 - 3 F 4 and 1 D 2 - 3 H 6 transitions of the Tm 3+ cations. It has been found that doping with Thulium 0.5 mol % renders the most intense OSL emission. Furthermore, several dosimetric properties such as OSL response as a function of dose, reproducibility of the OSL signal after several cycles of irradiation readout and the minimum detectable dose have been investigated. Finally, the OSL response of KMgF 3 : Tm 3+ has been compared to that of commercial Al 2 O 3 :C and the possible application of this fluoro perovskite to OSL dosimetry has been evaluated. (Author)

  3. Electric and magnetic properties of oxidic titanium bronzes of rare earths Lnsub(2/3+x)TiOsub(3+-y) with perovskite structure

    International Nuclear Information System (INIS)

    Bazuev, G.V.; Makarova, O.V.; Shvejkin, G.P.

    1983-01-01

    A study was made on electric and magnetic properties of oxidic titanium bronzes of rare earths and their dependence on rare earth nature and the degree of rare earth sublattice filling was followed. Data on Lnsub(2/3)TiOsub(3-y) (Ln-Ce, Nd) anion-deficient perovskites are given as well. Investigated Cesub(2/3)TiOsub(2.985) and Ndsub(2/3)TiOsub(2.875) phases as well as defectless with respect to oxygen Lnsub(2/3)TiOsub(3) phases have rhombic structure of perovskite type with ordered position of Ln 3 + cations and vacancies. Specific electric resistance and thermoelectromotive force factor were determined in vacuum at 290-1173 K for samples in the form of parallelepiped of 3x5x25 mm 3 size. Magnetic susceptibility chi was determined at 77-300 K by Faraday method using a device based on magnetic balancewith electromagnetic compensation. Relative error during chi measuring didn't exceed +-2%. Collectivized behaviour of d-electrons of Ti 3 + cations in oxidic titanium bronzes of rare earths: Lnsub(2/3+x)TiOsub(3+-y) (Ln-La, Ce, Nd; 0 < x < 1/3), conditioned by formation of narrow, partly filled π*-zone, was established on the basis of measuring specific electric resistance and magnetic susceptibility

  4. 2:1 Charge disproportionation in perovskite-structure oxide La{sub 1/3}Ca{sub 2/3}FeO{sub 3} with unusually-high-valence Fe{sup 3.67+}

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Haichuan; Hosaka, Yoshiteru; Seki, Hayato; Saito, Takashi; Ichikawa, Noriya [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Shimakawa, Yuichi, E-mail: shimak@scl.kyoto-u.ac.jp [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Integrated Research Consortium on Chemical Sciences, Uji, Kyoto 611-0011 (Japan)

    2017-02-15

    La{sub 1/3}Ca{sub 2/3}FeO{sub 3} with unusually-high-valence Fe{sup 3.67+} was synthesized at a high pressure and high temperature. The compound crystallizes in a √2a×2a×√2a perovskite cell in which the La and Ca ions at the A site are disordered. At 217 K the Fe{sup 3.67+} shows charge disproportionation to Fe{sup 3+} and Fe{sup 5+} in a ratio of 2:1, and this disproportionation is accompanied by transitions in magnetic and transport properties. The charge-disproportionated Fe{sup 3+} and Fe{sup 5+} are arranged along the <111> direction of the cubic perovskite cell. The local electronic and magnetic environments of Fe in La{sub 1/3}Ca{sub 2/3}FeO{sub 3} are quite similar to those of Fe in La{sub 1/3}Sr{sub 2/3}FeO{sub 3}, and the 2:1 charge disproportionation pattern of Fe{sup 3+} and Fe{sup 5+} in La{sub 1/3}Ca{sub 2/3}FeO{sub 3} is also the same as that in La{sub 1/3}Sr{sub 2/3}FeO{sub 3}. - Graphical abstract: The perovskite-structure oxide La{sub 1/3}Ca{sub 2/3}FeO{sub 3} with unusually-high-valence Fe{sup 3.67+} shows charge disproportionation to Fe{sup 3+} and Fe{sup 5+} in a ratio of 2:1, and the charge-disproportionated Fe{sup 3+} and Fe{sup 5+} are arranged along the <111> direction of the cubic perovskite cell. - Highlights: • La{sub 1/3}Ca{sub 2/3}FeO{sub 3} with unusually-high-valence Fe{sup 3.67+} was synthesized at a high pressure and high temperature. • At 217 K the Fe{sup 3.67+} shows charge disproportionation (CD) to Fe{sup 3+} and Fe{sup 5+} in a ratio of 2:1. • The charge-disproportionated Fe{sup 3+} and Fe{sup 5+} are arranged along the <111> direction of the cubic perovskite cell. • The disproportionation is accompanied by transitions in magnetic and transport properties.

  5. Post-perovskite transitions in CaB4+O3 at high pressure

    International Nuclear Information System (INIS)

    Akaogi, M; Shirako, Y; Kojitani, H; Takamori, S; Yamaura, K; Takayama-Muromachi, E

    2010-01-01

    High-pressure phase transitions in CaRhO 3 were examined using a multianvil apparatus up to 27 GPa and 1930 o C. CaRhO 3 perovskite transforms to post-perovskite via a monoclinic intermediate phase with increasing pressure. Volume changes for the transitions of perovskite - intermediate phase and of intermediate phase - post-perovskite are -1.1 and -0.7 %, respectively. CaRhO 3 post-perovskite is the fourth quenchable post-perovskite oxide found so far. By high-temperature calorimetric experiments, enthalpy of the perovskite - post-perovskite transition in CaRuO 3 was measured as 15.2±3.3 kJ/mol. Combining the datum with those of CaIrO 3 , it is shown that CaIrO 3 perovskite is energetically less stable than CaRuO 3 perovskite. This is consistent with the fact that orthorhombic distortion of CaIrO 3 perovskite is larger than CaRuO 3 , as indicated with the tilt-angle of octahedral framework of perovskite structure. The transition pressure from perovskite to post-perovskite in CaBO 3 (B = Ru, Rh, Ir) increases almost linearly with decreasing the tilt-angle, suggesting that the perovskite - post-perovskite transition may result from instability of the perovskite structure with pressure.

  6. Engineering of CH 3 NH 3 PbI 3 Perovskite Crystals by Alloying Large Organic Cations for Enhanced Thermal Stability and Transport Properties

    KAUST Repository

    Peng, Wei

    2016-07-28

    The number of studies on organic–inorganic hybrid perovskites has soared in recent years. However, the majority of hybrid perovskites under investigation are based on a limited number of organic cations of suitable sizes, such as methylammonium and formamidinium. These small cations easily fit into the perovskite\\'s three-dimensional (3D) lead halide framework to produce semiconductors with excellent charge transport properties. Until now, larger cations, such as ethylammonium, have been found to form 2D crystals with lead halide. Here we show for the first time that ethylammonium can in fact be incorporated coordinately with methylammonium in the lattice of a 3D perovskite thanks to a balance of opposite lattice distortion strains. This inclusion results in higher crystal symmetry, improved material stability, and markedly enhanced charge carrier lifetime. This crystal engineering strategy of balancing opposite lattice distortion effects vastly increases the number of potential choices of organic cations for 3D perovskites, opening up new degrees of freedom to tailor their optoelectronic and environmental properties.

  7. Structural properties, electric response and magnetic behaviour of La2SrFe2CoO9 triple complex perovskite

    Science.gov (United States)

    Casallas, F.; Vera, E.; Landínez, D.; Parra, C.; Roa, J.

    2016-02-01

    The triple perovskite La2SrFe2CoO9 was prepared by the solid state reaction method from the high purity precursor powders La2O3, SrCO3, Fe2O3, Co2O3 (99.9%). The crystalline structure was studied by X-ray diffraction experiments and Rietveld refinement analysis. Results reveal that this material crystallizes in an orthorhombic triple perovskite belonging to the space group Pnma (#62) with lattice constants a=5.491978(2)Ǻ, b=7.719842(2)Ǻ and c=5.436260(3)Ǻ. The granular surface morphology was studied from images of Scanning Electron Microscopy. The electric response was studied by the Impedance Spectroscopy technique from 10.0mHz up to 0.1MHz, at different temperatures (77-300K). Measurements of magnetization as a function of temperature permitted to determine the occurrence of a paramagnetic - ferromagnetic transition for a Curie temperature of 280K, which suggests it application in nanoelectronic devices. From the fit of the magnetic response with the Curie- Weiss equation it was concluded that the effective magnetic moment is particularly large due to the contribution of La, Fe and Co cations.

  8. Engineering of CH 3 NH 3 PbI 3 Perovskite Crystals by Alloying Large Organic Cations for Enhanced Thermal Stability and Transport Properties

    KAUST Repository

    Peng, Wei; Miao, Xiaohe; Adinolfi, Valerio; Alarousu, Erkki; El Tall, Omar; Emwas, Abdul-Hamid M.; Zhao, Chao; Walters, Grant; Liu, Jiakai; Ouellette, Olivier; Pan, Jun; Banavoth, Murali; Sargent, Edward H.; Mohammed, Omar F.; Bakr, Osman

    2016-01-01

    The number of studies on organic–inorganic hybrid perovskites has soared in recent years. However, the majority of hybrid perovskites under investigation are based on a limited number of organic cations of suitable sizes, such as methylammonium and formamidinium. These small cations easily fit into the perovskite's three-dimensional (3D) lead halide framework to produce semiconductors with excellent charge transport properties. Until now, larger cations, such as ethylammonium, have been found to form 2D crystals with lead halide. Here we show for the first time that ethylammonium can in fact be incorporated coordinately with methylammonium in the lattice of a 3D perovskite thanks to a balance of opposite lattice distortion strains. This inclusion results in higher crystal symmetry, improved material stability, and markedly enhanced charge carrier lifetime. This crystal engineering strategy of balancing opposite lattice distortion effects vastly increases the number of potential choices of organic cations for 3D perovskites, opening up new degrees of freedom to tailor their optoelectronic and environmental properties.

  9. Unrecognized vitamin D3 deficiency is common in Parkinson disease: Harvard Biomarker Study.

    Science.gov (United States)

    Ding, Hongliu; Dhima, Kaltra; Lockhart, Kaitlin C; Locascio, Joseph J; Hoesing, Ashley N; Duong, Karen; Trisini-Lipsanopoulos, Ana; Hayes, Michael T; Sohur, U Shivraj; Wills, Anne-Marie; Mollenhauer, Brit; Flaherty, Alice W; Hung, Albert Y; Mejia, Nicte; Khurana, Vikram; Gomperts, Stephen N; Selkoe, Dennis J; Schwarzschild, Michael A; Schlossmacher, Michael G; Hyman, Bradley T; Sudarsky, Lewis R; Growdon, John H; Scherzer, Clemens R

    2013-10-22

    To conclusively test for a specific association between the biological marker 25-hydroxy-vitamin D3, a transcriptionally active hormone produced in human skin and liver, and the prevalence and severity of Parkinson disease (PD). We used liquid chromatography/tandem mass spectrometry to establish an association specifically between deficiency of 25-hydroxy-vitamin D3 and PD in a cross-sectional and longitudinal case-control study of 388 patients (mean Hoehn and Yahr stage of 2.1 ± 0.6) and 283 control subjects free of neurologic disease nested in the Harvard Biomarker Study. Plasma levels of 25-hydroxy-vitamin D3 were associated with PD in both univariate and multivariate analyses with p values = 0.0034 and 0.047, respectively. Total 25-hydroxy-vitamin D levels, the traditional composite measure of endogenous and exogenous vitamin D, were deficient in 17.6% of patients with PD compared with 9.3% of controls. Low 25-hydroxy-vitamin D3 as well as total 25-hydroxy-vitamin D levels were correlated with higher total Unified Parkinson's Disease Rating Scale scores at baseline and during follow-up. Our study reveals an association between 25-hydroxy-vitamin D3 and PD and suggests that thousands of patients with PD in North America alone may be vitamin D-deficient. This finding has immediate relevance for individual patients at risk of falls as well as public health, and warrants further investigation into the mechanism underlying this association.

  10. Topotactic reduction as a route to new close-packed anion deficient perovskites: structure and magnetism of 4H-BaMnO(2+x).

    Science.gov (United States)

    Hadermann, Joke; Abakumov, Artem M; Adkin, Josephine J; Hayward, Michael A

    2009-08-05

    The anion-deficient perovskite 4H-BaMnO(2+x) has been obtained by a topotactic reduction, with LiH, of the hexagonal perovskite 4H-BaMnO(3-x). The crystal structure of 4H-BaMnO(2+x) was solved using electron diffraction and X-ray powder diffraction and further refined using neutron powder diffraction (S.G. Pnma, a = 10.375(2) A, b = 9.466(2) A, c = 11.276(3) A, at 373 K). The orthorhombic superstructure arises from the ordering of oxygen vacancies within a 4H (chch) stacking of close packed c-type BaO(2.5) and h-type BaO(1.5) layers. The ordering of the oxygen vacancies transforms the Mn(2)O(9) units of face-sharing MnO(6) octahedra into Mn(2)O(7) (two corner-sharing tetrahedra) and Mn(2)O(6) (two edge-sharing tetrahedra) groups. The Mn(2)O(7) and Mn(2)O(6) groups are linked by corner-sharing into a three-dimensional framework. The structures of the BaO(2.5) and BaO(1.5) layers are different from those observed previously in anion-deficient perovskites providing a new type of order pattern of oxygen atoms and vacancies in close packed structures. Magnetization measurements and neutron diffraction data reveal 4H-BaMnO(2+x) adopts an antiferromagnetically ordered state below T(N) approximately 350 K.

  11. Increased Risk for Vitamin D Deficiency in Obese Children with Both Celiac Disease and Type 1 Diabetes

    Directory of Open Access Journals (Sweden)

    Nithya Setty-Shah

    2014-01-01

    Full Text Available Background. It is unknown whether the coexistence of type 1 diabetes (T1D and celiac disease (CD increases the risk for vitamin D deficiency. Aims. To determine the vitamin D status and the risk for vitamin D deficiency in prepubertal children with both T1D and CD compared to controls, TID, and CD. Subjects and Methods. Characteristics of 62 prepubertal children of age 2–13 y with either CD + T1D (n=22, 9.9 ± 3.1 y, CD only (n=18, 8.9 ± 3.3 y, or T1D only (n=22, 10.1 ± 2.8 y were compared to 49 controls of the age of 8.0 ± 2.6 years. Vitamin D deficiency was defined as 25(OHD 85th but 95th percentile. Results. The 4 groups had no difference in 25(OHD (ANOVA P=0.123 before stratification into normal-weight versus overweight/obese subtypes. Following stratification, 25(OHD differed significantly between the subgroups (F(3,98=10.109, ANOVA P<0.001. Post-hoc analysis showed a significantly lower 25(OHD in the overweight/obese CD + T1D compared to the overweight/obese controls (P=0.039 and the overweight/obese CD (P=0.003. Subjects with CD + T1D were 3 times more likely to be vitamin D deficient (OR = 3.1 [0.8–11.9], P=0.098, compared to controls. Conclusions. The coexistence of T1D and CD in overweight/obese prepubertal children may be associated with lower vitamin D concentration.

  12. Synthesis, structure and total conductivity of A-site doped LaTiO3−δ perovskites

    International Nuclear Information System (INIS)

    Bradha, M.; Hussain, S.; Chakravarty, Sujay; Amarendra, G.; Ashok, Anuradha

    2015-01-01

    Highlights: • A-site divalent alkaline earth metal doped LaTiO 3−δ perovskites were synthesised by sol–gel method. • Structural studies revealed no change in crystal symmetry but change in cell dimensions after doping. • After doping divalent cations in A-site, an enhancement in total conductivity was observed in LaTiO 3−δ . • Temperature dependent electrical property was observed in all synthesised perovskites. - Abstract: Oxygen deficient perovskites LaTiO 3−δ and La 0.8 A 0.2 TiO 3−δ (A = Ba, Sr, Ca) were synthesized by sol–gel method. The effect of divalent dopants on microstructure is investigated in detail using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The oxidation states of La 3+ and Ti 3+ ions have been deduced using X-ray Photoelectron Spectroscopy (XPS). Impedance spectroscopy was used to analyze the total conductivity, an increase in conductivity was observed after doping in the A-site with divalent cations Ba, Ca and Sr. Among the investigated perovskites La 0.8 Ca 0.2 TiO 3−δ exhibited the maximum conductivity of 1.22 × 10 −2 S/cm in air atmosphere at 650 °C

  13. Residual tensile stresses and piezoelectric properties in BiFeO3-Bi(Zn1/2Ti1/2O3-PbTiO3 ternary solid solution perovskite ceramics

    Directory of Open Access Journals (Sweden)

    Weilin Zheng

    2016-08-01

    Full Text Available For low dielectric loss perovskite-structured (1-x-yBiFeO3-xBi(Zn1/2Ti1/2O3-yPbTiO3 (BF-BZT-PT (x = 0.04-0.15 and y = 0.15-0.26 ceramics in rhombohedral/tetragonal coexistent phase, structural phase transitions were studied using differential thermal analyzer combined with temperature-dependent dielectric measurement. Two lattice structural phase transitions are disclosed in various BF-BZT-PT perovskites, which is different from its membership of BiFeO3 exhibiting just one lattice structural phase transition at Curie temperature TC= 830oC. Consequently, residual internal tensile stresses were revealed experimentally through XRD measurements on ceramic pellets and counterpart powders, which are reasonably attributed to special structural phase transition sequence of BF-BZT-PT solid solution perovskites. Low piezoresponse was observed and argued extrinsically resulting from residual tensile stresses pinning ferroelectric polarization switching. Post-annealing and subsequent quenching was found effective for eliminating residual internal stresses in those BZT-less ceramics, and good piezoelectric property of d33 ≥ 28 pC/N obtained for 0.70BF-0.08BZT-0.22PT and 0.05 wt% MnO2-doped 0.70BF-0.04BZT-0.26PT ceramics with TC ≥ 640oC, while it seemed no effective for those BZT-rich BF-BZT-PT ceramics with x = 0.14 and 0.15 studied here.

  14. Perovskite-based heterostructures integrating ferromagnetic-insulating La0.1Bi0.9MnO3

    Science.gov (United States)

    Gajek, M.; Bibes, M.; Barthélémy, A.; Varela, M.; Fontcuberta, J.

    2005-05-01

    We report on the growth of thin films and heterostructures of the ferromagnetic-insulating perovskite La0.1Bi0.9MnO3. We show that the La0.1Bi0.9MnO3 perovskite grows single phased, epitaxially, and with a single out-of-plane orientation either on SrTiO3 substrates or onto strained La2/3Sr1/3MnO3 and SrRuO3 ferromagnetic-metallic buffer layers. We discuss the magnetic properties of the La0.1Bi0.9MnO3 films and heterostructures in view of their possible potential as magnetoelectric or spin-dependent tunneling devices.

  15. Trapping charges at grain boundaries and degradation of CH3NH3Pb(I1-x Br x )3 perovskite solar cells

    Science.gov (United States)

    Phuong Nguyen, Bich; Kim, Gee Yeong; Jo, William; Kim, Byeong Jo; Jung, Hyun Suk

    2017-08-01

    The electrical properties of CH3NH3Pb(I1-x Br x )3 (x = 0.13) perovskite materials were investigated under ambient conditions. The local work function and the local current were measured using Kelvin probe force microscopy and conductive atomic force microscopy, respectively. The degradation of the perovskite layers depends on their grain size. As the material degrades, an additional peak in the surface potential appears simultaneously with a sudden increase and subsequent relaxation of the local current. The potential bending at the grain boundaries and the intragrains is the most likely reason for the change of the local current surface of the perovskite layers. The improved understanding of the degradation mechanism garnered from this study helps pave the way toward an improved photo-conversion efficiency in perovskite solar cells.

  16. Effects of Fe-Enrichment on the Equation of State and Stability of (Mg,Fe)SiO3 Perovskite and Post-Perovskite

    Science.gov (United States)

    Dorfman, S. M.; Holl, C. M.; Meng, Y.; Prakapenka, V.; Duffy, T. S.

    2010-12-01

    Fe-enrichment in the deep lower mantle has been proposed as an explanation for seismic anomalies such as large low shear velocity provinces (LLSVPs) and ultralow velocity zones (ULVZs). In order to resolve the effect of Fe on the stability and equation of state of the lower mantle’s dominant constituent, (Mg,Fe)SiO3 perovskite, we have studied Fe-rich natural orthopyroxenes, (Mg0.61Fe0.37Ca0.02)SiO3 and (Mg0.25Fe0.70Ca0.05)SiO3 (compositions determined by microprobe analysis), at lower mantle P-T conditions. Pyroxene starting materials were mixed with Au (pressure calibrant and laser absorber) and loaded with NaCl or Ne (pressure medium and thermal insulator) in a symmetric diamond anvil cell. X-ray diffraction experiments at pressures up to 122 GPa with in-situ laser heating were performed at the GSECARS (13-ID-D) and HPCAT (16-ID-B) sectors of the Advanced Photon Source. Heating samples to 2000 K produced single-phase orthorhombic GdFeO3-type perovskite at 63 GPa for the Mg# 61 composition and at 72 GPa for the Mg# 25 composition. At lower pressures (56 GPa for Mg# 61, 67 GPa for Mg# 25), heating both compositions resulted in a mixture of perovskite, SiO2 and (Mg,Fe)O. These measurements provide new constraints on the dependence of (Mg,Fe)SiO3 perovskite stability on pressure and composition. Upon further compression to 93 GPa and higher pressures with laser heating, Mg# 25 perovskite transformed to a two-phase mixture of perovskite and post-perovskite. This is consistent with previous findings that Fe substitution destabilizes (Mg,Fe)SiO3 perovskite relative to (Mg,Fe)SiO3 post-perovskite (Mao et al. 2004, Caracas and Cohen 2005). The bulk modulus at 80 GPa (K80) is ~550 GPa for both Fe-rich perovskites, comparable to values measured for MgSiO3 perovskite (Lundin et al. 2008). However, the volume of Fe-rich perovskites increases linearly with Fe-content. The (Mg0.25Fe0.70Ca0.05)SiO3 perovskite is 3% greater at 80 GPa than V80 for the Mg end

  17. Electric and magnetic properties of oxidic titanium bronzes of rare earths Lnsub(2/3+x)TiOsub(3+-y) with perovskite structure

    Energy Technology Data Exchange (ETDEWEB)

    Bazuev, G V; Makarova, O V; Shvejkin, G P [AN SSSR, Sverdlovsk. Inst. Khimii

    1983-01-01

    A study was made on electric and magnetic properties of oxidic titanium bronzes of rare earths and their dependence on rare earth nature and the degree of rare earth sublattice filling was followed. Data on Lnsub(2/3)TiOsub(3-y) (Ln-Ce, Nd) anion-deficient perovskites are given as well. Investigated Cesub(2/3)TiOsub(2.985) and Ndsub(2/3)TiOsub(2.875) phases as well as defectless with respect to oxygen Lnsub(2/3)TiOsub(3) phases have rhombic structure of perovskite type with ordered position of Ln/sup 3 +/ cations and vacancies. Specific electric resistance and thermoelectromotive force factor were determined in vacuum at 290-1173 K for samples in the form of parallelepiped of 3x5x25 mm/sup 3/ size. Magnetic susceptibility chi was determined at 77-300 K by Faraday method using a device based on magnetic balance with electromagnetic compensation. Relative error during chi measuring didn't exceed +-2%. Collectivized behaviour of d-electrons of Ti/sup 3 +/ cations in oxidic titanium bronzes of rare earths: Lnsub(2/3+x)TiOsub(3+-y) (Ln-La, Ce, Nd; 0 < x < 1/3), conditioned by formation of narrow, partly filled ..pi..*-zone, was established on the basis of measuring specific electric resistance and magnetic susceptibility.

  18. Micropatterned 2D Hybrid Perovskite Thin Films with Enhanced Photoluminescence Lifetimes.

    Science.gov (United States)

    Kamminga, Machteld E; Fang, Hong-Hua; Loi, Maria Antonietta; Ten Brink, Gert H; Blake, Graeme R; Palstra, Thomas T M; Ten Elshof, Johan E

    2018-04-18

    The application of luminescent materials in display screens and devices requires micropatterned structures. In this work, we have successfully printed microstructures of a two-dimensional (2D), orange-colored organic/inorganic hybrid perovskite ((C 6 H 5 CH 2 NH 3 ) 2 PbI 4 ) using two different soft lithography techniques. Notably, both techniques yield microstructures with very high aspect ratios in the range of 1.5-1.8. X-ray diffraction reveals a strong preferential orientation of the crystallites along the c-axis in both patterned structures, when compared to nonpatterned, drop-casted thin films. Furthermore, (time-resolved) photoluminescence (PL) measurements reveal that the optical properties of (C 6 H 5 CH 2 NH 3 ) 2 PbI 4 are conserved upon patterning. We find that the larger grain sizes of the patterned films with respect to the nonpatterned film give rise to an enhanced PL lifetime. Thus, our results demonstrate easy and cost-effective ways to manufacture patterns of 2D organic/inorganic hybrid perovskites, while even improving their optical properties. This demonstrates the potential use of color-tunable 2D hybrids in optoelectronic devices.

  19. Vitamin D Deficiency Among Professional Basketball Players.

    Science.gov (United States)

    Fishman, Matthew P; Lombardo, Stephen J; Kharrazi, F Daniel

    2016-07-01

    Vitamin D plays an important role in several systems of the human body. Various studies have linked vitamin D deficiency to stress and insufficiency fractures, muscle recovery and function, and athletic performance. The prevalence of vitamin D deficiency in the elite athletic population has not been extensively studied, and very few reports exist among professional athletes. There is a high prevalence of vitamin D deficiency or insufficiency among players attending the National Basketball Association (NBA) Combine. Cross-sectional study; Level of evidence, 3. This is a retrospective review of data previously collected as part of the routine medical evaluation of players in the NBA Combines from 2009 through 2013. Player parameters evaluated were height, weight, body mass index (BMI), and vitamin D level. Statistical analysis using t tests and analysis of variance was used to detect any correlation between the player parameters and vitamin D level. Vitamin D levels were categorized as deficient (32 ng/mL). After institutional review board approval was submitted to the NBA, the NBA released deidentified data on 279 players who participated in the combines from 2009 through 2013. There were 90 players (32.3%) who were deficient, 131 players (47.0%) who were insufficient, and 58 players (20.8%) who were sufficient. A total of 221 players (79.3%) were either vitamin D deficient or insufficient. Among all players included, the average vitamin D level was 25.6 ± 10.2 ng/mL. Among the players who were deficient, insufficient, and sufficient, the average vitamin D levels were 16.1 ± 2.1 ng/mL, 25.0 ± 3.4 ng/mL, and 41.6 ± 8.6 ng/mL, respectively. Player height and weight were significantly increased in vitamin D-sufficient players compared with players who were not sufficient (P = .0008 and .009, respectively). Player age and BMI did not significantly differ depending on vitamin D status (P = .15 and .77, respectively). There is a high prevalence of vitamin D deficiency

  20. Hybrid perovskite resulting from the solid-state reaction between the organic cations and perovskite layers of alpha1-(Br-(CH(2))(2)-NH(3))(2)PbI(4).

    Science.gov (United States)

    Sourisseau, Sebastien; Louvain, Nicolas; Bi, Wenhua; Mercier, Nicolas; Rondeau, David; Buzaré, Jean-Yves; Legein, Christophe

    2007-07-23

    The alpha1-(Br-(CH(2))(2)-NH(3))(2)PbI(4) hybrid perovskite undergoes a solid-state transformation, that is, the reaction between the organic cations and the perovskite layers to give the new hybrid perovskite (Br-(CH(2))(2)-NH(3))(2-x)(I-(CH(2))(2)-NH(3))(x)PbBr(x)I(4-x), based on mixed halide inorganic layers. This transformation has been followed by a conventional powder X-ray diffraction system equipped with a super speed detector, and both solid-state (13)C NMR and ESI/MS measurements have been adopted in the estimation of the rate of halide substitution. The first reaction step leads to the special composition of x approximately 1 (A phase), while the complete substitution is not achieved even at elevated temperature (x(max) approximately 1.85 (B phase)). This unprecedented solid-state reaction between organic and inorganic components of a hybrid perovskite can be considered as a completely new strategy to achieve interesting hybrid perovskites.

  1. Vitamin D deficiency among healthy Egyptian females.

    Science.gov (United States)

    Botros, Raif M; Sabry, Inas M; Abdelbaky, Rania S; Eid, Yara M; Nasr, Merihan S; Hendawy, Laila M

    2015-01-01

    Vitamin D deficiency is becoming endemic in many parts of the world. To study vitamin D status in Egyptian females of different age groups. A cross-sectional study was conducted on 404 females, who were categorized into group 1 (51 nursing females); group 2 (50 pregnant females); group 3 (208 females of childbearing age); group 4 (38 elderly females); and group 5 (57 geriatric females). Females completed a questionnaire regarding dietary calcium and vitamin D intake, sun exposure, and clothing habits, and performed laboratory tests including calcium, PO4, alkaline phosphatase, intact PTH, and 25-OH vitamin D levels. Median and IQR of vitamin D levels across groups 1, 2, 3 and 5 were in the deficient range, being lowest in groups 3, 5, and 1, respectively. Vitamin D deficiency was found in 72.6% of the nursing group, 54% of the pregnant group, 72% of the childbearing age group, 39.5% of the elderly group, and 77.2% of the geriatric group. Vitamin D was significantly higher in non-veiled females [23ng/dl] as compared to veiled females [16.7ng/dl]. Vitamin D levels with poor, fair, and good sun exposure were 14.1, 14, and 37ng/dl, respectively. These results show a high prevalence of vitamin D deficiency among healthy Egyptian females. Copyright © 2015 SEEN. Published by Elsevier España, S.L.U. All rights reserved.

  2. CYP2R1 mutations causing vitamin D-deficiency rickets.

    Science.gov (United States)

    Thacher, Tom D; Levine, Michael A

    2017-10-01

    CYP2R1 is the principal hepatic 25-hydroxylase responsible for the hydroxylation of parent vitamin D to 25-hydroxyvitamin D [25(OH)D]. Serum concentrations of 25(OH)D reflect vitamin D status, because 25(OH)D is the major circulating metabolite of vitamin D. The 1α-hydroxylation of 25(OH)D in the kidney by CYP27B1 generates the fully active vitamin D metabolite, 1,25-dihydroxyvitamin D (1,25(OH) 2 D). The human CYP2R1 gene, located at 11p15.2, has five exons, coding for an enzyme with 501 amino acids. In Cyp2r1-/- knockout mice, serum 25(OH)D levels were reduced by more than 50% compared wild-type mice. Genetic polymorphisms of CYP2R1 account for some of the individual variability of circulating 25(OH)D values in the population. We review the evidence that inactivating mutations in CYP2R1 can lead to a novel form of vitamin D-deficiency rickets resulting from impaired 25-hydroxylation of vitamin D. We sequenced the promoter, exons and intron-exon flanking regions of the CYP2R1 gene in members of 12 Nigerian families with rickets in more than one family member. We found missense mutations (L99P and K242N) in affected members of 2 of 12 families. The L99P mutation had previously been reported as a homozygous defect in an unrelated child of Nigerian origin with rickets. In silico analyses predicted impaired CYP2R1 folding or reduced interaction with substrate vitamin D by L99P and K242N mutations, respectively. In vitro studies of the mutant CYP2R1 proteins in HEK293 cells confirmed normal expression levels but completely absent or markedly reduced 25-hydroxylase activity by the L99P and K242N mutations, respectively. Heterozygous subjects had more moderate biochemical and clinical features of vitamin D deficiency than homozygous subjects. After an oral bolus dose of 50,000 IU of vitamin D 2 or vitamin D 3 , heterozygous subjects had lower increases in serum 25(OH)D than control subjects, and homozygous subjects had minimal increases, supporting a semidominant

  3. Characterization of SrCo1.5Ti1.5Fe9O19 hexagonal ferrite synthesized by sol-gel combustion and solid state route

    International Nuclear Information System (INIS)

    Vinaykumar, R.; Mazumder, R.; Bera, J.

    2017-01-01

    Co-Ti co-substituted SrM hexagonal ferrite (SrCo 1.5 Ti 1.5 Fe 9 O 19 ) was synthesized by sol-gel combustion and solid state route. The effects of sources of TiO 2 raw materials; titanium tetra-isopropoxide (TTIP) and titanyl nitrate (TN) on the phase formation behavior and properties of the ferrite were studied. The thermal decomposition behavior of the gel was studied using TG-DSC. The phase formation behavior of the ferrite was studied by using X-ray powder diffraction and FTIR analysis. Phase formation was comparatively easier in the TN-based sol-gel process. The morphology of powder and sintered ferrite was investigated using scanning electron microscope. Magnetic properties like magnetization, coercivity, permeability, tan δ µ and dielectric properties were investigated. The ferrite synthesized by sol-gel based chemical route showed higher saturation magnetization, permeability and permittivity compared to the ferrite synthesized by solid state route. - Highlights: • SrCo 1.5 Ti 1.5 Fe 9 O 19 ferrite was successfully prepared by sol–gel combustion process. • Sol-gel synthesis of the ferrite using titanyl nitrate has been reported first time. • Phase formation was easier in the titanyl nitrate based sol-gel process. • Better magneto-dielectric properties were observed in sol-gel processed ferrite.

  4. Two-Dimensional CH₃NH₃PbI₃ Perovskite: Synthesis and Optoelectronic Application.

    Science.gov (United States)

    Liu, Jingying; Xue, Yunzhou; Wang, Ziyu; Xu, Zai-Quan; Zheng, Changxi; Weber, Bent; Song, Jingchao; Wang, Yusheng; Lu, Yuerui; Zhang, Yupeng; Bao, Qiaoliang

    2016-03-22

    Hybrid organic-inorganic perovskite materials have received substantial research attention due to their impressively high performance in photovoltaic devices. As one of the oldest functional materials, it is intriguing to explore the optoelectronic properties in perovskite after reducing it into a few atomic layers in which two-dimensional (2D) confinement may get involved. In this work, we report a combined solution process and vapor-phase conversion method to synthesize 2D hybrid organic-inorganic perovskite (i.e., CH3NH3PbI3) nanocrystals as thin as a single unit cell (∼1.3 nm). High-quality 2D perovskite crystals have triangle and hexagonal shapes, exhibiting tunable photoluminescence while the thickness or composition is changed. Due to the high quantum efficiency and excellent photoelectric properties in 2D perovskites, a high-performance photodetector was demonstrated, in which the current can be enhanced significantly by shining 405 and 532 nm lasers, showing photoresponsivities of 22 and 12 AW(-1) with a voltage bias of 1 V, respectively. The excellent optoelectronic properties make 2D perovskites building blocks to construct 2D heterostructures for wider optoelectronic applications.

  5. The efficiency limit of CH3NH3PbI3 perovskite solar cells

    International Nuclear Information System (INIS)

    Sha, Wei E. I.; Ren, Xingang; Chen, Luzhou; Choy, Wallace C. H.

    2015-01-01

    With the consideration of photon recycling effect, the efficiency limit of methylammonium lead iodide (CH 3 NH 3 PbI 3 ) perovskite solar cells is predicted by a detailed balance model. To obtain convincing predictions, both AM 1.5 spectrum of Sun and experimentally measured complex refractive index of perovskite material are employed in the detailed balance model. The roles of light trapping and angular restriction in improving the maximal output power of thin-film perovskite solar cells are also clarified. The efficiency limit of perovskite cells (without the angular restriction) is about 31%, which approaches to Shockley-Queisser limit (33%) achievable by gallium arsenide (GaAs) cells. Moreover, the Shockley-Queisser limit could be reached with a 200 nm-thick perovskite solar cell, through integrating a wavelength-dependent angular-restriction design with a textured light-trapping structure. Additionally, the influence of the trap-assisted nonradiative recombination on the device efficiency is investigated. The work is fundamentally important to high-performance perovskite photovoltaics

  6. Emergence of non-Fermi liquid behaviors in 5d perovskite SrIrO3 thin films: Interplay between correlation, disorder, and spin-orbit coupling

    Science.gov (United States)

    Biswas, Abhijit; Kim, Ki-Seok; Jeong, Yoon H.

    2016-02-01

    We investigate the effects of compressive strain on the electrical resistivity of 5d iridium based perovskite SrIrO3 by depositing epitaxial films of thickness 35 nm on various substrates such as GdScO3 (110), DyScO3 (110), and SrTiO3 (001). Surprisingly, we find anomalous transport behaviors as expressed by ρ∝Tε in the temperature dependent resistivity, where the temperature exponent ε evolves continuously from 4/5 to 1 and to 3/2 with an increase of compressive strain. Furthermore, magnetoresistance always remains positive irrespective of resistivity upturns at low temperatures. These observations imply that the delicate interplay between correlation and disorder in the presence of strong spin-orbit coupling is responsible for the emergence of the non-Fermi liquid behaviors in 5d perovskite SrIrO3 thin films. We offer a theoretical framework for the interpretation of the experimental results.

  7. PbBr3 Perovskite Crystals

    KAUST Repository

    Wei, Tzu-Chiao

    2018-01-31

    Researchers have recently revealed that hybrid lead halide perovskites exhibit ferroelectricity, which is often associated with other physical characteristics, such as a large nonlinear optical response. In this work, the nonlinear optical properties of single crystal inorganic–organic hybrid perovskite CH3NH3PbBr3 are studied. By exciting the material with a 1044 nm laser, strong two-photon absorption-induced photoluminescence in the green spectral region is observed. Using the transmission open-aperture Z-scan technique, the values of the two-photon absorption coefficient are observed to be 8.5 cm GW−1, which is much higher than that of standard two-photon absorbing materials that are industrially used in nonlinear optical applications, such as lithium niobate (LiNbO3), LiTaO3, KTiOPO4, and KH2PO4. Such a strong two-photon absorption effect in CH3NH3PbBr3 can be used to modulate the spectral and spatial profiles of laser pulses, as well as to reduce noise, and can be used to strongly control the intensity of incident light. In this study, the superior optical limiting, pulse reshaping, and stabilization properties of CH3NH3PbBr3 are demonstrated, opening new applications for perovskites in nonlinear optics.

  8. Emergence of non-Fermi liquid behaviors in 5d perovskite SrIrO{sub 3} thin films: Interplay between correlation, disorder, and spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, Abhijit [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of); Kim, Ki-Seok [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of); Institute of Edge of Theoretical Science (IES), POSTECH, Pohang 790-784 (Korea, Republic of); Jeong, Yoon H., E-mail: yhj@postech.ac.kr [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of)

    2016-02-15

    We investigate the effects of compressive strain on the electrical resistivity of 5d iridium based perovskite SrIrO{sub 3} by depositing epitaxial films of thickness 35 nm on various substrates such as GdScO{sub 3} (110), DyScO{sub 3} (110), and SrTiO{sub 3} (001). Surprisingly, we find anomalous transport behaviors as expressed by ρ∝T{sup ε} in the temperature dependent resistivity, where the temperature exponent ε evolves continuously from 4/5 to 1 and to 3/2 with an increase of compressive strain. Furthermore, magnetoresistance always remains positive irrespective of resistivity upturns at low temperatures. These observations imply that the delicate interplay between correlation and disorder in the presence of strong spin-orbit coupling is responsible for the emergence of the non-Fermi liquid behaviors in 5d perovskite SrIrO{sub 3} thin films. We offer a theoretical framework for the interpretation of the experimental results. - Highlights: • We studied the effect of compressive strain on the perovskite SrIrO{sub 3} thin films. • We revealed non-Fermi liquid behaviors in the transport properties. • Irrespective of weak localization effects, magnetoresistance remains positive. • Mott-Anderson-Griffiths scenario is proposed to account for the NFL behaviors.

  9. Perovskite oxide SrTiO3 as an efficient electron transporter for hybrid perovskite solar cells

    KAUST Repository

    Bera, Ashok

    2014-12-11

    In this work, we explored perovskite oxide SrTiO3 (STO) for the first time as the electron-transporting layer in organolead trihalide perovskite solar cells. The steady-state photoluminescence (PL) quenching and transient absorption experiments revealed efficient photoelectron transfer from CH3NH3PbI3-xClx to STO. Perovskite solar cells with meso-STO exhibit an open circuit voltage of 1.01 V, which is 25% higher than the value of 0.81 V achieved in the control device with the conventional meso-TiO2. In addition, an increase of 17% in the fill factor was achieved by tailoring the thickness of the meso-STO layer. We found that the application of STO leads to uniform perovskite layers with large grains and complete surface coverage, leading to a high shunt resistance and improved performance. These findings suggest STO as a competitive candidate as electron transport material in organometal perovskite solar cells.

  10. Perovskite oxide SrTiO3 as an efficient electron transporter for hybrid perovskite solar cells

    KAUST Repository

    Bera, Ashok; Wu, Kewei; Sheikh, Arif D.; Alarousu, Erkki; Mohammed, Omar F.; Wu, Tao

    2014-01-01

    In this work, we explored perovskite oxide SrTiO3 (STO) for the first time as the electron-transporting layer in organolead trihalide perovskite solar cells. The steady-state photoluminescence (PL) quenching and transient absorption experiments revealed efficient photoelectron transfer from CH3NH3PbI3-xClx to STO. Perovskite solar cells with meso-STO exhibit an open circuit voltage of 1.01 V, which is 25% higher than the value of 0.81 V achieved in the control device with the conventional meso-TiO2. In addition, an increase of 17% in the fill factor was achieved by tailoring the thickness of the meso-STO layer. We found that the application of STO leads to uniform perovskite layers with large grains and complete surface coverage, leading to a high shunt resistance and improved performance. These findings suggest STO as a competitive candidate as electron transport material in organometal perovskite solar cells.

  11. Resurrection of vitamin D deficiency and rickets

    Science.gov (United States)

    Holick, Michael F.

    2006-01-01

    The epidemic scourge of rickets in the 19th century was caused by vitamin D deficiency due to inadequate sun exposure and resulted in growth retardation, muscle weakness, skeletal deformities, hypocalcemia, tetany, and seizures. The encouragement of sensible sun exposure and the fortification of milk with vitamin D resulted in almost complete eradication of the disease. Vitamin D (where D represents D2 or D3) is biologically inert and metabolized in the liver to 25-hydroxyvitamin D [25(OH)D], the major circulating form of vitamin D that is used to determine vitamin D status. 25(OH)D is activated in the kidneys to 1,25-dihydroxyvitamin D [1,25(OH)2D], which regulates calcium, phosphorus, and bone metabolism. Vitamin D deficiency has again become an epidemic in children, and rickets has become a global health issue. In addition to vitamin D deficiency, calcium deficiency and acquired and inherited disorders of vitamin D, calcium, and phosphorus metabolism cause rickets. This review summarizes the role of vitamin D in the prevention of rickets and its importance in the overall health and welfare of infants and children. PMID:16886050

  12. Optically stimulated luminescence properties of Tm{sup 3+} doped KMgF{sub 3} fluoro perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Camargo, L.; Marcazzo, J. [UNCPBA, Facultad de Ciencias Exactas, Instituto de Fisica Arroyo Seco, Gral. Pinto 399, B7000GHG Tandil, Buenos Aires (Argentina); Perez C, L.; Cruz Zaragoza, E. [UNAM, Instituto de Ciencias Nucleares, Apdo. Postal 70543, 04510 Ciudad de Mexico (Mexico); Martinez O, S. A., E-mail: jmarcass@exa.unicen.edu.ar [Universidad Pedagogica y Tecnologica de Colombia, Grupo de Fisica Nuclear Aplicada y Simulacion, Av. Central del Norte 39-115, 150003 Tunja, Bocaya (Colombia)

    2017-10-15

    In this work the optically stimulated luminescence (OSL) properties of undoped and Tm{sup 3+} doped KMgF{sub 3} fluoro perovskite have been investigated for the first time. OSL efficiency for stimulation with different wavelengths has been analyzed for each compound. The maximum OSL emission was found with blue light stimulation. The radioluminescence (Rl) spectra have shown two emission peaks at 455 and 360 nm, which can be ascribed to the {sup 1}D{sub 2}-{sup 3}F{sub 4} and {sup 1}D{sub 2}-{sup 3}H{sub 6} transitions of the Tm{sup 3+} cations. It has been found that doping with Thulium 0.5 mol % renders the most intense OSL emission. Furthermore, several dosimetric properties such as OSL response as a function of dose, reproducibility of the OSL signal after several cycles of irradiation readout and the minimum detectable dose have been investigated. Finally, the OSL response of KMgF{sub 3}: Tm{sup 3+} has been compared to that of commercial Al{sub 2}O{sub 3}:C and the possible application of this fluoro perovskite to OSL dosimetry has been evaluated. (Author)

  13. Should vitamin D deficiency be corrected before parathyroidectomy?

    Science.gov (United States)

    Randle, Reese W; Balentine, Courtney J; Wendt, Elizabeth; Schneider, David F; Chen, Herbert; Sippel, Rebecca S

    2016-07-01

    Vitamin D deficiency is common in patients with hyperparathyroidism, but the importance of replacement before surgery is controversial. We aimed to evaluate the impact of vitamin D deficiency on the extent of resection and risk of postoperative hypocalcemia for patients undergoing parathyroidectomy for primary hyperparathyroidism. We identified patients with primary hyperparathyroidism undergoing parathyroid surgery between 2000 and 2015 using a prospectively maintained database. Patients with normal (≥30 ng/mL) vitamin D were compared to those with levels less than 30 ng/mL. There were 1015 (54%) patients with normal vitamin D and 872 (46%) patients with vitamin D deficiency undergoing parathyroidectomy for primary hyperparathyroidism. Vitamin D deficiency was associated with higher preoperative parathyroid hormone (median 90 versus 77 pg/mL, P vitamin D. To achieve similar cure rates, patients with vitamin D deficiency were less likely to require removal of more than one gland (20% versus 30%, P vitamin D. Patients with vitamin D deficiency had similar rates of persistent (1.5% versus 2.0%, P = 0.43) and recurrent (1.7% versus 2.6%, P = 0.21) hyperparathyroidism. Postoperatively, both groups had equivalent rates of transient (2.3% versus 2.3%, P = 0.97) and permanent (0.2% versus 0.4%, P = 0.52) hypocalcemia. Restoring vitamin D in deficient patients should not delay the appropriate surgical treatment of primary hyperparathyroidism. Deficient patients are more likely to be cured with the excision of a single adenoma and no more likely to suffer persistence, recurrence, or hypocalcemia than patients with normal vitamin D. Copyright © 2016 Elsevier Inc. All rights reserved.

  14. Thermal engineering of lead-free nanostructured CH3NH3SnCl3 perovskite material for thin-film solar cell

    Science.gov (United States)

    Moyez, Sk Abdul; Roy, Subhasis

    2018-01-01

    Perovskite solar cell is a kind of revolutionary investigation in the field of renewable energy which is capable of mitigates the deficiencies of silicon solar cell and its uprising efficiency can bring blessing to society. The presence of lead (Pb) in perovskite solar cell can make worst and negative impact on environment and is not desirable for our society. In this paper, general plans are anticipated by replacement of Pb with tin (Sn) in open atmosphere to fabricate the CH3NH3SnCl3 photovoltaic cells in chlorine (Cl)-rich environment. Excess uses of Cl has positive influences on morphological growth of the film and it also suppresses the oxidation tendency of tin (Sn) with existing oxygen in atmosphere and maintains same chemical atmosphere as bulk. Various characterization tools like X-ray diffraction, scanning electron microscope (SEM) have been used to study the effect of annealing temperature on crystal stricture, phase formation, impurities, and morphologies of the film. Finally, photovoltaic performance was reported using the solar simulator under 1.5 sun illumination.

  15. Resolution of the crystal structure of the deficient perovskite LaNiO2.5 from neutron powder diffraction data

    International Nuclear Information System (INIS)

    Alonso, J.A.; Martinez-Lope, M.J.

    1996-01-01

    The oxygen-deficient perovskite LaNiO 2.5 has been prepared by controlled reduction of LaNiO 3 with Zr metal. The XRD pattern could be indexed in a monoclinic unit-cell with dimensions a 0 xa 0 xa 0 (a 0 : lattice parameter of the ideal cubic perovskite). The indexing of the neutron powder diffraction pattern needed a doubled cell to account for the superstructure reflections originated by the oxygen vacancy ordering and the tilting of the Ni coordination polyhedra. The structure was solved and refined from the neutron powder data. The oxygen vacancies are ordered in such a way that square planar NiO 4 and NiO 6 octahedra alternate in the ab plane along the [110] direction. Both kinds of Ni polyhedra are fairly distorted and tilted in order to optimize the La-O distances, giving rise to a highly strained structure of metastable character. In fact, the compound readily takes oxygen, above 175 C in air, to give the much more stable LaNiO 3 perovskite. (orig.)

  16. Performance evaluation of Mn and Fe doped SrCo0.9Nb0.1O3-δ cathode for IT-SOFC application

    Science.gov (United States)

    Bele, Lokesh; Lenka, R. K.; Patro, P. K.; Muhmood, L.; Mahata, T.; Sinha, P. K.

    2018-02-01

    Cathode materials of Mn and Fe doped SrCo0.9Nb0.1O3-δ, are synthesized by solid state route for intermediate temperature fuel cell applications. Phase pure material is obtained after calcining the precursors at 1100 °C. Phase compatibility is observed between this novel cathode material with gadolinia doped ceria (GDC) electrolyte material as reflected in the diffraction pattern. The state of art YSZ electrolyte is not compatible with this cathode material. Average thermal expansion coefficient of the material varies between 17 to 22 X 10-6 K-1 on doping, from room temperature to 800 °C. Increase in thermal expansion coefficient is observed with Mn and Fe doping associated with the loss of oxygen from the crystal. The electrical conductivity of the cathode material decreases with Fe and Mn doping. Mn doped samples show lowest conductivity. From the symmetric cell measurement lower area specific resistance (0.16 Ω-cm2) is obtained for un-doped samples, at 850 °C. From the initial results it can be inferred that Mn/Fe doping improves neither the thermal expansion co-efficient nor the electrochemical activity.

  17. Synthesis, structure and total conductivity of A-site doped LaTiO{sub 3−δ} perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Bradha, M. [Nanotech Research Facility, PSG Institute of Advanced Studies, Coimbatore 641 004, TN (India); Hussain, S.; Chakravarty, Sujay [UGC-DAE CSR, Kalpakkam Node, Kokilamedu 603 104, TN (India); Amarendra, G. [UGC-DAE CSR, Kalpakkam Node, Kokilamedu 603 104, TN (India); Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, TN (India); Ashok, Anuradha, E-mail: anu.machina@gmail.com [Nanotech Research Facility, PSG Institute of Advanced Studies, Coimbatore 641 004, TN (India)

    2015-03-25

    Highlights: • A-site divalent alkaline earth metal doped LaTiO{sub 3−δ} perovskites were synthesised by sol–gel method. • Structural studies revealed no change in crystal symmetry but change in cell dimensions after doping. • After doping divalent cations in A-site, an enhancement in total conductivity was observed in LaTiO{sub 3−δ}. • Temperature dependent electrical property was observed in all synthesised perovskites. - Abstract: Oxygen deficient perovskites LaTiO{sub 3−δ} and La{sub 0.8}A{sub 0.2}TiO{sub 3−δ} (A = Ba, Sr, Ca) were synthesized by sol–gel method. The effect of divalent dopants on microstructure is investigated in detail using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The oxidation states of La{sup 3+} and Ti{sup 3+} ions have been deduced using X-ray Photoelectron Spectroscopy (XPS). Impedance spectroscopy was used to analyze the total conductivity, an increase in conductivity was observed after doping in the A-site with divalent cations Ba, Ca and Sr. Among the investigated perovskites La{sub 0.8}Ca{sub 0.2}TiO{sub 3−δ} exhibited the maximum conductivity of 1.22 × 10{sup −2} S/cm in air atmosphere at 650 °C.

  18. The Role of Vitamin D Deficiency in the Incidence, Progression, and Complications of Type 1 Diabetes Mellitus

    Directory of Open Access Journals (Sweden)

    Marlene Chakhtoura

    2013-01-01

    Full Text Available The “nonclassic” role of 1,25-dihydroxyvitamin D3 (1,25(OH2D3 has been recently widely recognized. In type 1 diabetes mellitus (T1D, it plays an immunomodulatory role through the vitamin D receptor (VDR present on pancreatic and immune cells. Specific VDR allelic variants have been associated with T1D in many countries. Furthermore, vitamin D deficiency has been prevalent in T1D, and the seasonal and latitude variability in the incidence of T1D can be partly explained by the related variability in vitamin D level. In fact, retrospective studies of vitamin D supplementation during pregnancy or infancy showed a lower incidence of T1D. We will review the different mechanisms of the vitamin D protective effect against insulitis and present the available data on the role of vitamin D deficiency in the control, progression, and complications of T1D.

  19. Quantum confinement effect and exciton binding energy of layered perovskite nanoplatelets

    Directory of Open Access Journals (Sweden)

    Qiang Wang

    2018-02-01

    Full Text Available We report the preparation of monolayer (n = 1, few-layer (n = 2–5 and 3D (n = ∞ organic lead bromide perovskite nanoplatelets (NPLs by tuning the molar ratio of methylammonium bromide (MABr and hexadecammonium bromide (HABr. The absorption spectrum of the monolayer (HA2PbBr4 perovskite NPLs shows about 138 nm blue shift from that of 3D MAPbBr3 perovskites, which is attributed to strong quantum confinement effect. We further investigate the two-photon photoluminescence (PL of the NPLs and measure the exciton binding energy of monolayer perovskite NPLs using linear absorption and two-photon PL excitation spectroscopy. The exciton binding energy of monolayer perovskite NPLs is about 218 meV, which is far larger than tens of meV in 3D lead halide perovskites.

  20. Vitamin D deficiency in early pregnancy.

    Directory of Open Access Journals (Sweden)

    Shannon K Flood-Nichols

    Full Text Available Vitamin D deficiency is a common problem in reproductive-aged women in the United States. The effect of vitamin D deficiency in pregnancy is unknown, but has been associated with adverse pregnancy outcomes. The objective of this study was to analyze the relationship between vitamin D deficiency in the first trimester and subsequent clinical outcomes.This is a retrospective cohort study. Plasma was collected in the first trimester from 310 nulliparous women with singleton gestations without significant medical problems. Competitive enzymatic vitamin D assays were performed on banked plasma specimens and pregnancy outcomes were collected after delivery. Logistic regression was performed on patients stratified by plasma vitamin D concentration and the following combined clinical outcomes: preeclampsia, preterm delivery, intrauterine growth restriction, gestational diabetes, and spontaneous abortion.Vitamin D concentrations were obtained from 235 patients (mean age 24.3 years, range 18-40 years. Seventy percent of our study population was vitamin D insufficient with a serum concentration less than 30 ng/mL (mean serum concentration 27.6 ng/mL, range 13-71.6 ng/mL. Logistic regression was performed adjusting for age, race, body mass index, tobacco use, and time of year. Adverse pregnancy outcomes included preeclampsia, growth restriction, preterm delivery, gestational diabetes, and spontaneous abortion. There was no association between vitamin D deficiency and composite adverse pregnancy outcomes with an adjusted odds ratio of 1.01 (p value 0.738, 95% confidence intervals 0.961-1.057.Vitamin D deficiency did not associate with adverse pregnancy outcomes in this study population. However, the high percentage of affected individuals highlights the prevalence of vitamin D deficiency in young, reproductive-aged women.

  1. Improvement of CH3NH3PbI3 thin film using the additive 1,8-diiodooctane for planar heterojunction perovskite cells

    Science.gov (United States)

    Abdulrahman, Solh; Wang, Chunhua; Cao, Chenghao; Zhang, Chujun; Yang, Junliang; Jiang, Li

    2017-10-01

    The thin-film quality is critical for obtaining high-performance perovskite solar cells (PSCs). The additive 1,8-diiodooctane (DIO) was used to control the morphology and structure of CH3NH3PbI3 perovskite thin films, and planar heterojunction (PHJ) PSCs with an architecture of ITO/PEDOT: PSS/CH3NH3PbI3/PCBM/Al was fabricated. It was found that the DIO played an important role on CH3NH3PbI3 thin-film quality and the performance of PHJ-PSCs. With the optimal volume ratio of 2%, the compact and uniform high-quality CH3NH3PbI3 thin films with enhanced crystallinity and less roughness were achieved, resulting in the great improvement of power conversion efficiency (PCE) from about 4.5% to over 9.0%. The research results indicate that the additive DIO is a simple and effective method to produce high-quality perovskite thin film and accordingly develop high-performance PHJ-PSCs.

  2. Deficiency of 25-Hydroxyvitamin D and Dyslipidemia in Indian Subjects

    Directory of Open Access Journals (Sweden)

    Jaydip Ray Chaudhuri

    2013-01-01

    Full Text Available Background. Vitamin D deficiency is widespread throughout the world. Several reports have incriminated vitamin D deficiency as the cause of rickets, osteomalacia, and other chronic diseases. Recent studies have suggested a possible link between deficiency of 25-hydroxyvitamin D and dyslipidemia. Aim. To investigate the association between 25-hydroxyvitamin D deficiency and dyslipidemia in Indian subjects. Methodology. We recruited 150 asymptomatic consecutive subjects from patients’ attendees at the Departments of Neurology and Medicine in Yashoda Hospital, Hyderabad, India. Study period was from October 2011 to March 2012. All subjects underwent 25-hydroxyvitamin D assay by chemiluminescent microparticle immunoassay, fasting blood sugar and lipid profile, calcium, phosphorus, alkaline phosphatase, and C-reactive protein (CRP. Results. Out of 150 subjects, men were 82 (54.6%, and mean age was 49.4 (±15.6 years. Among risk factors, hypertension was noted in 63/150 (42%, 25-hydroxyvitamin D deficiency in 59/150 (39.3%, diabetes in 45/150 (30%, dyslipidemia in 60 (40%, smoking in 35/150 (23.3%, and alcoholism in 27/150 (18%. Deficiency of 25-hydroxyvitamin D was significantly associated with dyslipidemia (P=0.0001, mean serum glucose (P=0.0002 mean CRP (P=0.04, and mean alkaline phosphatase (P=0.01. Multivariate analysis showed that 25-hydroxyvitamin D deficiency was independently associated with dyslipidemia (odds ratio: 1.9; 95% CI : 1.13.5. Conclusions. We found that deficiency of 25-hydroxyvitamin D was independently associated with dyslipidemia in Indian subjects.

  3. Stable Graphene-Two-Dimensional Multiphase Perovskite Heterostructure Phototransistors with High Gain.

    Science.gov (United States)

    Shao, Yuchuan; Liu, Ye; Chen, Xiaolong; Chen, Chen; Sarpkaya, Ibrahim; Chen, Zhaolai; Fang, Yanjun; Kong, Jaemin; Watanabe, Kenji; Taniguchi, Takashi; Taylor, André; Huang, Jinsong; Xia, Fengnian

    2017-12-13

    Recently, two-dimensional (2D) organic-inorganic perovskites emerged as an alternative material for their three-dimensional (3D) counterparts in photovoltaic applications with improved moisture resistance. Here, we report a stable, high-gain phototransistor consisting of a monolayer graphene on hexagonal boron nitride (hBN) covered by a 2D multiphase perovskite heterostructure, which was realized using a newly developed two-step ligand exchange method. In this phototransistor, the multiple phases with varying bandgap in 2D perovskite thin films are aligned for the efficient electron-hole pair separation, leading to a high responsivity of ∼10 5 A W -1 at 532 nm. Moreover, the designed phase alignment method aggregates more hydrophobic butylammonium cations close to the upper surface of the 2D perovskite thin film, preventing the permeation of moisture and enhancing the device stability dramatically. In addition, faster photoresponse and smaller 1/f noise observed in the 2D perovskite phototransistors indicate a smaller density of deep hole traps in the 2D perovskite thin film compared with their 3D counterparts. These desirable properties not only improve the performance of the phototransistor, but also provide a new direction for the future enhancement of the efficiency of 2D perovskite photovoltaics.

  4. Investigating Recombination and Charge Carrier Dynamics in a One-Dimensional Nanopillared Perovskite Absorber.

    Science.gov (United States)

    Kwon, Hyeok-Chan; Yang, Wooseok; Lee, Daehee; Ahn, Jihoon; Lee, Eunsong; Ma, Sunihl; Kim, Kyungmi; Yun, Seong-Cheol; Moon, Jooho

    2018-05-22

    Organometal halide perovskite materials have become an exciting research topic as manifested by intense development of thin film solar cells. Although high-performance solar-cell-based planar and mesoscopic configurations have been reported, one-dimensional (1-D) nanostructured perovskite solar cells are rarely investigated despite their expected promising optoelectrical properties, such as enhanced charge transport/extraction. Herein, we have analyzed the 1-D nanostructure effects of organometal halide perovskite (CH 3 NH 3 PbI 3- x Cl x ) on recombination and charge carrier dynamics by utilizing a nanoporous anodized alumina oxide scaffold to fabricate a vertically aligned 1-D nanopillared array with controllable diameters. It was observed that the 1-D perovskite exhibits faster charge transport/extraction characteristics, lower defect density, and lower bulk resistance than the planar counterpart. As the aspect ratio increases in the 1-D structures, in addition, the charge transport/extraction rate is enhanced and the resistance further decreases. However, when the aspect ratio reaches 6.67 (diameter ∼30 nm), the recombination rate is aggravated due to high interface-to-volume ratio-induced defect generation. To obtain the full benefits of 1-D perovskite nanostructuring, our study provides a design rule to choose the appropriate aspect ratio of 1-D perovskite structures for improved photovoltaic and other optoelectrical applications.

  5. High-pressure crystal growth and electromagnetic properties of 5d double-perovskite Ca3OsO6

    International Nuclear Information System (INIS)

    Feng, Hai Luke; Shi, Youguo; Guo, Yanfeng; Li, Jun; Sato, Akira; Sun, Ying; Wang, Xia; Yu, Shan; Sathish, Clastin I.; Yamaura, Kazunari

    2013-01-01

    Single crystals of the osmium-containing compound Ca 3 OsO 6 have been successfully grown under high-pressure conditions, for the first time. The crystal structure of Ca 3 OsO 6 were characterized as an ordered double-perovskite structure of space group P2 1 /n with the Ca and Os atoms being fully ordered at the perovskite B-site. The electromagnetic analysis shows that the crystal exhibits a semiconductor-like behavior below 300 K and undergoes an antiferromagnetic transition at 50 K. - Graphical Abstract: Schematic image of crystal structure of Ca 3 OsO 6 as determined by X-ray diffraction, where the gray and black octahedrons are occupied by Ca and Os, respectively. Top inset reveals an optic image of a typical Ca 3 OsO 6 single crystal. Highlights: ► Single crystals of Ca 3 OsO 6 have been successfully grown under high-pressure. ► Ca 3 OsO 6 crystalizes into an ordered double-perovskite structure. ► The Ca 3 OsO 6 undergoes an antiferromagnetic transition at 50 K

  6. 2D halide perovskite-based van der Waals heterostructures: contact evaluation and performance modulation

    Science.gov (United States)

    Guo, Yaguang; Saidi, Wissam A.; Wang, Qian

    2017-09-01

    Halide perovskites and van der Waals (vdW) heterostructures are both of current interest owing to their novel properties and potential applications in nano-devices. Here, we show the great potential of 2D halide perovskite sheets (C4H9NH3)2PbX4 (X  =  Cl, Br and I) that were synthesized recently (Dou et al 2015 Science 349 1518-21) as the channel materials contacting with graphene and other 2D metallic sheets to form van der Waals heterostructures for field effect transistor (FET). Based on state-of-the-art theoretical simulations, we show that the intrinsic properties of the 2D halide perovskites are preserved in the heterojunction, which is different from the conventional contact with metal surfaces. The 2D halide perovskites form a p-type Schottky barrier (Φh) contact with graphene, where tunneling barrier exists, and a negative band bending occurs at the lateral interface. We demonstrate that the Schottky barrier can be turned from p-type to n-type by doping graphene with nitrogen atoms, and a low-Φh or an Ohmic contact can be realized by doping graphene with boron atoms or replacing graphene with other high-work-function 2D metallic sheets such as ZT-MoS2, ZT-MoSe2 and H-NbS2. This study not only predicts a 2D halide perovskite-based FETs, but also enhances the understanding of tuning Schottky barrier height in device applications.

  7. Synthesis and magnetic properties of a new borophosphate SrCo2BPO7 with a four-column ribbon structure.

    Science.gov (United States)

    Gou, Wenbin; He, Zhangzhen; Yang, Ming; Zhang, Weilong; Cheng, Wendan

    2013-03-04

    A new borophosphate SrCo2BPO7 is synthesized by a conventional high-temperature solid-state reaction. The titled compound is found to crystallize in monoclinic system with space group P21/c, which displays a distorted four-column ribbon structure. Both BO3 triangles and PO4 tetrahedra are isolated, while irregular triangles built by Co(2+) ions are found to exist between the connecting ribbons. Magnetic behaviors are investigated by means of susceptibility, magnetization, and heat capacity measurements. The results confirm that SrCo2BPO7 possesses a three-dimensional antiferromagnetic ordering at 25 K. The possible spin arrangements in the system are also suggested.

  8. Modulation of renal Ca2+ transport protein genes by dietary Ca2+ and 1,25-dihydroxyvitamin D3 in 25-hydroxyvitamin D3-1alpha-hydroxylase knockout mice.

    NARCIS (Netherlands)

    Hoenderop, J.G.J.; Dardenne, O.; Abel, M. van; Kemp, J.W.C.M. van der; Os, C.H. van; Arnaud, R. St.; Bindels, R.J.M.

    2002-01-01

    Pseudovitamin D-deficiency rickets (PDDR) is an autosomal disease characterized by hyperparathyroidism, rickets, and undetectable levels of 1,25-dihydroxyvitaminD3 (1,25(OH)2D3). Mice in which the 25-hydroxyvitamin D3-1alpha-hydroxylase (1alpha-OHase) gene was inactivated presented the same clinical

  9. NaIrO3-A pentavalent post-perovskite

    International Nuclear Information System (INIS)

    Bremholm, M.; Dutton, S.E.; Stephens, P.W.; Cava, R.J.

    2011-01-01

    Sodium iridium (V) oxide, NaIrO 3, was synthesized by a high pressure solid state method and recovered to ambient conditions. It is found to be isostructural with CaIrO 3 , the much-studied structural analog of the high-pressure post-perovskite phase of MgSiO 3 . Among the oxide post-perovskites, NaIrO 3 is the first example with a pentavalent cation. The structure consists of layers of corner- and edge-sharing IrO 6 octahedra separated by layers of NaO 8 bicapped trigonal prisms. NaIrO 3 shows no magnetic ordering and resistivity measurements show non-metallic behavior. The crystal structure, electrical and magnetic properties are discussed and compared to known post-perovskites and pentavalent perovskite metal oxides. -- Graphical abstract: Sodium iridium(V) oxide, NaIrO 3 , synthesized by a high pressure solid state method and recovered to ambient conditions is found to crystallize as the post-perovskite structure and is the first example of a pentavalent ABO 3 post-perovskite. Research highlights: → NaIrO 3 post-perovskite stabilized by pressure. → First example of a pentavalent oxide post-perovskite. → Non-metallic and non-magnetic behavior of NaIrO 3 .

  10. Serum alkaline phosphatase screening for vitamin D deficiency states

    International Nuclear Information System (INIS)

    Shaheen, S.; Barrakzai, Q.

    2012-01-01

    Objective: To determine whether serum vitamin D levels are correlated with serum levels of alkaline phosphatase or not. Study Design: Cross-sectional, observational study. Place and Duration of Study: Multi-centre study, conducted at Liaquat National Hospital and Medical College, National Medical Centre and Medicare Hospital, Karachi, from January to October 2009. Methodology: Patients attending the Orthopaedic OPDs with complaints of pain in different body regions and serum vitamin D/sub 3/ levels of greater or equal to 30 ng/ml were included in the study. Patients with vitamin D deficiency were further categorized into mild deficiency or insufficiency (vit. D/sub 3/ = 20-29 ng/ml), moderate deficiency (vit. D/sub 3/ = 5 - 19 ng/ml) and severe deficiency forms (vit. D/sub 3/ < 5 ng/ml). Pearson correlation was applied to test the correlation of serum alkaline phosphatase levels with serum vitamin D/sub 3/ levels. P-value < 0.05 was considered to be significant. Results: Out of 110 samples, 26 had mild (23%), 61 had moderate (55%) and 21 had severe (19.1%) vitamin D deficiencies. All of the patients in the three groups had alkaline phosphatase with in normal limits and the total mean value of the enzyme was 135.97 +- 68.14I U/L. The inter group comparison showed highest values of alkaline phosphatase in the moderate vitamin D deficiency group. The correlation coefficient of alkaline phosphatase and serum vitamin D/sub 3/ levels was r =0.05 (p =0.593). Conclusion: Serum vitamin D/sub 3/ levels may not be correlated with increased serum alkaline phosphatase levels. Therefore, alkaline phosphatase may not be used as a screening test to rule out vitamin D deficiency. (author)

  11. General working principles of CH3NH3PbX3 perovskite solar cells.

    Science.gov (United States)

    Gonzalez-Pedro, Victoria; Juarez-Perez, Emilio J; Arsyad, Waode-Sukmawati; Barea, Eva M; Fabregat-Santiago, Francisco; Mora-Sero, Ivan; Bisquert, Juan

    2014-02-12

    Organometal halide perovskite-based solar cells have recently realized large conversion efficiency over 15% showing great promise for a new large scale cost-competitive photovoltaic technology. Using impedance spectroscopy measurements we are able to separate the physical parameters of carrier transport and recombination in working devices of the two principal morphologies and compositions of perovskite solar cells, viz. compact thin films of CH3NH3PbI(3-x)Clx and CH3NH3PbI3 infiltrated on nanostructured TiO2. The results show nearly identical spectral characteristics indicating a unique photovoltaic operating mechanism that provides long diffusion lengths (1 μm). Carrier conductivity in both devices is closely matched, so that the most significant differences in performance are attributed to recombination rates. These results highlight the central role of the CH3NH3PbX3 semiconductor absorber in carrier collection and provide a new tool for improved optimization of perovskite solar cells. We report for the first time a measurement of the diffusion length in a nanostructured perovskite solar cell.

  12. Vitamin D3 deficiency increases DNA damage and modify the expression of genes associated with hypertension in normotensive and hypertensive rats

    Directory of Open Access Journals (Sweden)

    Carla Silva Machado

    2015-05-01

    Full Text Available Vitamin D3 is a lipophilic micronutrient obtained from the diet (salmon, sardines, mackerel and cod liver oil or by the conversion of 7-dehydrocholesterol on skin after exposure to UVB radiation. This vitamin participates in several cellular processes, contributes to the maintenance of calcium concentrations, acts on phosphorus absorption, and is also related to the development and progression of chronic diseases. In hypertension, it is known that vitamin D3 act on renin-angiotensin-aldosterone system, regulates the gene expression and can induce or attenuate oxidative DNA damage. Vitamin D3 deficiency is present in 30-50% of human population (Pilz et al., 2009, and has been associated with increase of chromosomal instability and DNA damage (Nair-Shalliker; Armstrong; Fenech, 2012. Since experimental and clinical studies have suggested a relationship between vitamin D3 and blood pressure, the aim of this study was to evaluate whether vitamin D3 deficiency or supplementation lead to an increase or decrease in DNA damage, regulates the expression of genes associated with hypertension and changes the systolic blood pressure. Spontaneously hypertensive rats (SHR, used as a model of human essential hypertension, and their normotensive controls (Wistar Kyoto – WKY were fed a control diet (vitamin D3 at 1.000 UI/kg, a deficient diet (vitamin D3 at 0 UI/kg or a supplemented diet (vitamin D3 at 10.000 UI/kg for 12 weeks. DNA damage was assessed by comet assay in cardiac muscle tissue and blood tissue, following the methodology proposed by Singh et al. (1988 and Tice et al. (2000; gene expression of 84 genes was assessed by RT2ProfilerTM PCR Array in cardiac muscle tissue; and systolic blood pressure was measured weekly by a noninvasive method using tail plethysmography. In SHR and WKY rats, vitamin D3 deficiency increased DNA damage in the blood tissue and did not change the DNA damage in cardiac muscle tissue; vitamin D3 supplementation maintained the

  13. Impact of Three Doses of Vitamin D3 on Serum 25(OH)D Deficiency and Insufficiency in At-Risk Schoolchildren.

    Science.gov (United States)

    Sacheck, Jennifer M; Van Rompay, Maria I; Chomitz, Virginia R; Economos, Christina D; Eliasziw, Misha; Goodman, Elizabeth; Gordon, Catherine M; Holick, Michael F

    2017-12-01

    We investigated the daily dose of vitamin D needed to achieve serum 25-hydroxyvitamin D [25(OH)D] sufficiency among schoolchildren at risk for deficiency. The Daily D Health Study was a randomized double-blind vitamin D supplementation trial among racially/ethnically diverse schoolchildren (n = 685) in the northeastern United States. Children were supplemented with vitamin D3 at 600, 1000, or 2000 IU/d for 6 months. Measurements included serum 25(OH)D at baseline (October to December), 3 months (January to March), 6 months (April to June), and 12 months (6 months after supplementation). At baseline, mean ± standard deviation serum 25(OH)D level was 22.0 ± 6.8 ng/mL, with 5.5% severely vitamin D deficient (D were found among black (17.9 ± 6.7 ng/mL) and Asian children (18.9 ± 4.8 ng/mL), with no baseline differences by weight status. Serum 25(OH)D increased over 6 months in all three dose groups. The 2000 IU/d group achieved a higher mean serum 25(OH)D level than the other two dose groups (33.1 vs 26.3 and 27.5 ng/mL; P D at 12 months. Children at risk for vitamin D deficiency benefited from daily sustained supplementation of 2000 IU/d compared with lower doses closer to the current recommended daily allowance for vitamin D intake. This benefit occurred over the winter months, when serum 25(OH)D level tend to fall. Copyright © 2017 Endocrine Society

  14. Vitamin D Deficiency Prevalence and Predictors in Early Pregnancy among Arab Women

    Directory of Open Access Journals (Sweden)

    Sara Al-Musharaf

    2018-04-01

    Full Text Available Data regarding the prevalence and predictors of vitamin D deficiency during early pregnancy are limited. This study aims to fill this gap. A total of 578 Saudi women in their 1st trimester of pregnancy were recruited between January 2014 and December 2015 from three tertiary care antenatal clinics in Riyadh, Saudi Arabia. Information collected includes socio-economic, anthropometric, and biochemical data, including serum vitamin D (25(OHD levels, intake of calcium and vitamin D, physical activity, and sun exposure indices. Pregnant women with 25(OHD levels <50 nmol/L were considered vitamin D deficient. The majority of participants (n = 468 (81% were vitamin D deficient. High levels of indoor activity, whole body clothing, multiparity, total cholesterol/HDL ratio(>3.5, low HDL-cholesterol, and living in West Riyadh were significant independent predictors for vitamin D deficiency, with odds ratios (ORs (95% confidence interval of 25.4 (5.5–117.3, 17.8 (2.3–138.5, 4.0 (1.7–9.5, 3.3 (1.4–7.9, 2.8 (1.2–6.4, and 2.0 (1.13.5, respectively. Factors like increased physical activity, sun exposure at noon, sunrise or sunset, high educational status, and residence in North Riyadh were protective against vitamin D deficiency with ORs 0.2 (0.1–0.5; 0.2 (0.1–0.6; 0.3 (0.1–0.9; and 0.4 (0.2–0.8, respectively. All ORs were adjusted for age, BMI, sun exposure, parity, summer season, vitamin D intake, multivitamin intake, physical activity, education, employment, living in the north, and coverage with clothing. In conclusion, the prevalence of vitamin D deficiency among Saudi women during early pregnancy was high (81%. Timely detection and appropriate supplementation with adequate amounts of vitamin D should reduce the risks of vitamin D deficiency and its complications during pregnancy.

  15. System Ba/sub 2/Gdsub(2/3)vacantsub(1/3)Usub(1-x)Wsub(x)O/sub 6/ and hexagonal perovskites of an 18-layer type

    Energy Technology Data Exchange (ETDEWEB)

    Wischert, W; Schittenhelm, H J; Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Inst. fuer Chemie

    1978-04-01

    In the system Ba/sub 2/Gdsub(2/3)vacantsub(1/3)Usub(1-x)Wsub(x)O/sub 6/ the formation of a continuous solid solution series is observed. With x <= 0.9 the mixed crystals have a cubic 1:1 ordered perovskite structure. With x >= 0.95 the compounds are polymorphic: besides an cubic 1:1 ordered perovskite type for x = 0.95; 0.99 and 1.00 one hexagonal layer structure exists. This lattice is in all cases rhombohedral (space group R3m) and represents an 18 L-type. Likewise the compounds Ba/sub 2/Bsub(2/3)sup(III)vacantsub(1/3)Wsup(VI)O/sub 6/ with Bsup(III) Tb-Lu and Y belong to the 18 L-type.

  16. Vitamin D Deficiency in Patients with Tuberculosis

    International Nuclear Information System (INIS)

    Iftikhar, R.; Kamran, S. M.; Haider, E.; Qadir, A.; Usman, H. B.

    2013-01-01

    Objective: To determine the frequency and association of Vitamin D deficiency in patients with tuberculosis. Study Design: Case control study. Place and Duration of Study: Medical Department, Combined Military Hospital, Kharian, from July 2010 to June 2012. Methodology: One hundred and five outdoor patients of tuberculosis were selected with 255 gender matched controls. Tuberculosis was diagnosed by presence of acid fast bacilli in sputum smears, positive culture for Mycobacterium tuberculosis or demonstration of chronic caseating granulomatous inflammation in tissue specimens. Controls were drawn randomly from general population. Serum 25 hydroxyvitamin D [25 (OH) D3] levels < 25 ng/ml was considered Vitamin D deficiency. The results were analyzed on SPSS version 17. Results: Mean Vitamin D levels were 23.23 A+- 6.81 ng/ml in cases, 29.27 A+- 8.89 ng/ml in controls (p < 0.0001). Vitamin D deficiency was found in 57% of cases and 33% controls (p < 0.0001). Mean Vitamin D levels were significantly lower in females with tuberculosis (20.84 ng/ml) as compared to males (25.03 ng/ml, p = 0.002). Mean BMI in patients of tuberculosis with Vitamin D deficiency were 19.51 A+- 1.77 kg/m2 and in patients with normal Vitamin D were 21.65 A+- 1.79 kg/m2 (p < 0.0001). Mean Vitamin D levels in patients with multi-drug resistant tuberculosis was lower to a mean of 15.41 A+- 4.67 ng/ml (p < 0.0001). Conclusion: There is significant deficiency of Vitamin D in patients with tuberculosis as compared to controls. This deficiency is more pronounced in females, individuals with low BMI, extra pulmonary and MDR tuberculosis. (author)

  17. High-pressure stability relations, crystal structures, and physical properties of perovskite and post-perovskite of NaNiF3

    International Nuclear Information System (INIS)

    Shirako, Y.; Shi, Y.G.; Aimi, A.; Mori, D.; Kojitani, H.; Yamaura, K.; Inaguma, Y.; Akaogi, M.

    2012-01-01

    NaNiF 3 perovskite was found to transform to post-perovskite at 16–18 GPa and 1273–1473 K. The equilibrium transition boundary is expressed as P (GPa)=−2.0+0.014×T (K). Structure refinements indicated that NaNiF 3 perovskite and post-perovskite have almost regular NiF 6 octahedra consistent with absence of the first-order Jahn–Teller active ions. Both NaNiF 3 perovskite and post-perovskite are insulators. The perovskite underwent a canted antiferromagnetic transition at 156 K, and the post-perovskite antiferromagnetic transition at 22 K. Magnetic exchange interaction of NaNiF 3 post-perovskite is smaller than that of perovskite, reflecting larger distortion of Ni–F–Ni network and lower dimension of octahedral arrangement in post-perovskite than those in perovskite. - Graphical abstract: Perovskite–post-perovskite transition in NaNiF 3 at high pressure Highlights: ► NaNiF 3 perovskite (Pv) transforms to post-perovskite (pPv) at 16 GPa and 1300 K. ► The equilibrium transition boundary is expressed as P (GPa)=−2.0+0.014 T (K). ► Antiferromagnetic transition occurs at 156 K in Pv and 22 K in pPv.

  18. Mechanism of formation of perovskite phase and dielectric properties of Pb(Zn,Mg)1/3Nb2/3O3 ceramics prepared by columbite precursor routes

    International Nuclear Information System (INIS)

    Jang, H.M.; Cho, S.R.; Lee, K.M.

    1995-01-01

    The mechanism of formation of the perovskite phase and the dielectric properties of Pb(Zn,Mg) 1/3 Nb 2/3 O 3 (PZMN) ceramics were examined using two different types of columbite precursors, (Mg,Zn)Nb 2 O 6 (MZN) and MgNb 2 O 6 + ZnNb 2 O 6 (MN + ZN). The formation of perovskite phase in the PbO + MN + ZN system is characterized by an initial rapid formation of Mg-rich perovskite phase, followed by a sluggish formation of Zn-rich perovskite phase. On the other hand, due to the formation of pyrochlore phase of mixed divalent cations Pb 2-x (Zn,Mg) y Nb 2-y O 7-x-3y/2 , the pyrochlore/perovskite transformation in the PbO + MZN system proceeded uniformly with a spatial homogeneity. Further analysis suggested that the formation of perovskite phase is a diffusion-controlled process. The degree of diffuseness of the rhombohedral/cubic phase transition (DPT) is higher in the PbO + MN + ZN system than in the PbO + MZN specimen for T > T max (temperature of the dielectric permittivity maximum), indicating a broadened compositional distribution of the B-site cations in the PbO + MN + ZN system

  19. Antiferroelectric Nature of CH3NH3PbI3-xClx Perovskite and Its Implication for Charge Separation in Perovskite Solar Cells

    Science.gov (United States)

    Sewvandi, Galhenage A.; Kodera, Kei; Ma, Hao; Nakanishi, Shunsuke; Feng, Qi

    2016-07-01

    Perovskite solar cells (PSCs) have been attracted scientific interest due to high performance. Some researchers have suggested anomalous behavior of PSCs to the polarizations due to the ion migration or ferroelectric behavior. Experimental results and theoretical calculations have suggested the possibility of ferroelectricity in organic-inorganic perovskite. However, still no studies have been concretely discarded the ferroelectric nature of perovskite absorbers in PSCs. Hysteresis of P-E (polarization-electric field) loops is an important evidence to confirm the ferroelectricity. In this study, P-E loop measurements, in-depth structural study, analyses of dielectric behavior and the phase transitions of CH3NH3PbI3-xClx perovskite were carried out and investigated. The results suggest that CH3NH3PbI3-xClx perovskite is in an antiferroelectric phase at room temperature. The antiferroelectric phase can be switched to ferroelectric phase by the poling treatment and exhibits ferroelectric-like hysteresis P-E loops and dielectric behavior around room temperature; namely, the perovskite can generate a ferroelectric polarization under PSCs operating conditions. Furthermore, we also discuss the implications of ferroelectric polarization on PSCs charge separation.

  20. Molecular Self-Assembly Fabrication and Carrier Dynamics of Stable and Efficient CH3 NH3 Pb(1-x) Snx I3 Perovskite Solar Cells.

    Science.gov (United States)

    Fan, Jiandong; Liu, Chong; Li, Hongliang; Zhang, Cuiling; Li, Wenzhe; Mai, Yaohua

    2017-10-09

    The Sn-based perovskite solar cells (PSCs) provide the possibility of swapping the Pb element toward developing toxic-free PSCs. Here, we innovatively employed a molecular self-assembly approach to obtain a series CH 3 NH 3 Pb (1-x) Sn x I 3 (0≤x≤1) perovskite thin films with full coverage. The optimized planar CH 3 NH 3 Pb 0.75 Sn 0.25 I 3 PSC with inverted structure was consequently realized with a maximum power conversion efficiency (PCE) over 14 %, which displayed a stabilized power output (SPO) over 12 % within 200 s at 0.6 V forward bias. Afterward, we investigated the factors that limited the efficiency improvement of hybrid Sn-Pb PSCs, and analyzed the possible reason of the hysteresis effect occurred even in the inverted structure cell. Particularly, the oxidation of hybrid Sn-Pb perovskite thin film was demonstrated to be the main reason that limited its further efficiency improvement. The imbalance of charge transport was intensified, which was associated with the increased hole defect-state density and decreased electron defect-state density after Sn was introduced. This study helps tackle the intractable issue regarding the toxic Pb in perovskite devices and is a step forward toward realizing lead-free PSCs with high stability and efficiency. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Solar Thermochemical Energy Storage Through Carbonation Cycles of SrCO3/SrO Supported on SrZrO3.

    Science.gov (United States)

    Rhodes, Nathan R; Barde, Amey; Randhir, Kelvin; Li, Like; Hahn, David W; Mei, Renwei; Klausner, James F; AuYeung, Nick

    2015-11-01

    Solar thermochemical energy storage has enormous potential for enabling cost-effective concentrated solar power (CSP). A thermochemical storage system based on a SrO/SrCO3 carbonation cycle offers the ability to store and release high temperature (≈1200 °C) heat. The energy density of SrCO3/SrO systems supported by zirconia-based sintering inhibitors was investigated for 15 cycles of exothermic carbonation at 1150 °C followed by decomposition at 1235 °C. A sample with 40 wt % of SrO supported by yttria-stabilized zirconia (YSZ) shows good energy storage stability at 1450 MJ m(-3) over fifteen cycles at the same cycling temperatures. After further testing over 45 cycles, a decrease in energy storage capacity to 1260 MJ m(-3) is observed during the final cycle. The decrease is due to slowing carbonation kinetics, and the original value of energy density may be obtained by lengthening the carbonation steps. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Excitonic and Polaronic Properties of 2D Hybrid Organic–Inorganic Perovskites

    KAUST Repository

    Yin, Jun

    2017-01-20

    We theoretically characterize the unusual white-light emission properties of two-dimensional (2D) hybrid organic inorganic perovskites with an APbX(4) structure (where A is a bidentate organic cation and X = Cl, Br). In addition to band structure calculations including corrections due to spin orbit couplings and electron hole interactions, a computationally intensive molecular cluster approach is exploited to describe the excitonic and polaronic properties of these 2D perovskites at the atomistic level. Upon adding or removing an electron from the neutral systems, we find that strongly localized small polarons form in the 2D clusters. The polaron charge density is distributed over just lattice sites, which is consistent with the calculated large polaron binding energies, on the order of similar to 0.4-1.2 eV.

  3. [Osteomalacia and vitamin D deficiency].

    Science.gov (United States)

    Rader, C P; Corsten, N; Rolf, O

    2015-09-01

    Vitamin D and calcium deficiency has a higher incidence in the orthopedic-trauma surgery patient population than generally supposed. In the long term this can result in osteomalacia, a form of altered bone mineralization in adults, in which the cartilaginous, non-calcified osteoid does not mature to hard bone. The current value of vitamin D and its importance for bones and other body cells are demonstrated. The causes of vitamin D deficiency are insufficient sunlight exposure, a lack of vitamin D3 and calcium, malabsorption, and rare alterations of VDR signaling and phosphate metabolism. The main symptoms are bone pain, fatigue fractures, muscular cramps, muscle pain, and gait disorders, with an increased incidence of falls in the elderly. Osteopathies induced by pharmaceuticals, tumors, rheumatism or osteoporosis have to be considered as the main differential diagnoses. In addition to the recording of symptoms and medical imaging, the diagnosis of osteomalacia should be ensured by laboratory parameters. Adequate treatment consists of the high-dose intake of vitamin D3 and the replacement of phosphate if deficient. Vitamin D is one of the important hormone-like vitamins and is required in all human cells. Deficiency of vitamin D has far-reaching consequences not only for bone, but also for other organ systems.

  4. A Quantitative Point-of-Need Assay for the Assessment of Vitamin D3 Deficiency.

    Science.gov (United States)

    Vemulapati, S; Rey, E; O'Dell, D; Mehta, S; Erickson, D

    2017-10-26

    Vitamin D is necessary for the healthy growth and development of bone and muscle. Vitamin D deficiency, which is present in 42% of the US population, is often undiagnosed as symptoms may not manifest for several years and long-term deficiency has been linked to osteoporosis, diabetes and cancer. Currently the majority of vitamin D testing is performed in large-scale commercial laboratories which have high operational costs and long times-to-result. Development of a low-cost point-of-need assay could be transformative to deficiency analysis in limited-resource settings. The best biomarker of vitamin D status, 25hydroxyvitamin D 3 (25(OH)D 3 ), however, is particularly challenging to measure in such a format due to complexities involved in sample preparation, including the need to separate the marker from its binding protein. Here we present a rapid diagnostic test for the accurate, quantitative assessment of 25(OH)D 3 in finger-stick blood. The assay is accompanied by a smartphone-assisted portable imaging device that can autonomously perform the necessary image processing. To achieve accurate quantification of 25(OH)D 3 , we also demonstrate a novel elution buffer that separates 25(OH)D 3 from its binding protein in situ, eliminating the need for sample preparation. In human trials, the accuracy of our platform is 90.5%.

  5. Modulation of electronic and optical properties in mixed halide perovskites CsPbCl3xBr3(1-x) and CsPbBr3xI3(1-x)

    Science.gov (United States)

    Zhou, Ziqi; Cui, Yu; Deng, Hui-Xiong; Huang, Le; Wei, Zhongming; Li, Jingbo

    2017-03-01

    The recent discovery of lead halide perovskites with band gaps in the visible presents important potential in the design of high efficient solar cells. CsPbCl3, CsPbBr3 and CsPbI3 are stable compounds within this new family of semiconductors. By performing the first-principles calculation, we explore the structural, electronic and optical properties of CsPbCl3xBr3(1-x) and CsPbBr3xI3(1-x) with various compositions of halide atoms. Structural stability is demonstrated with halide atoms distributing randomly at the halide atomic sites. CsPbCl3xBr3(1-x) and CsPbBr3xI3(1-x) exhibit the modulation of their band gaps by varying the halide composition. Our results also indicate that CsPbCl3xBr3(1-x) and CsPbBr3xI3(1-x) with different halide compositions are suitable to application to solar cells for the general features are well preserved. Good absorption to lights of different wavelengths has been obtained in these mixed halide perovskites.

  6. Vitamin D/dietary calcium deficiency rickets and pseudo-vitamin D deficiency rickets

    Science.gov (United States)

    Glorieux, Francis H; Pettifor, John M

    2014-01-01

    This review describes the pathogenesis, clinical presentation and biochemical perturbations found in privational (nutritional) rickets and pseudo-vitamin D deficiency rickets (PDDR), an autosomal recessive condition with loss of function mutations in CYP27B1. It may seem strange to combine a discussion on privational rickets and PDDR as a single topic, but privational rickets and PDDR present with similar clinical signs and symptoms and with similar perturbations in bone and mineral metabolism. Of interest is the characteristic lack of features of rickets at birth in infants with PDDR, a finding which has also been reported in infants born to vitamin D-deficient mothers. This highlights the independence of the fetus and neonate from the need for vitamin D to maintain calcium homeostasis during this period. The variable roles of vitamin D deficiency and dietary calcium deficiency in the pathogenesis of privational rickets are discussed and the associated alterations in vitamin D metabolism highlighted. Although PDDR is a rare autosomal recessive disorder, results of long-term follow-up are now available on the effect of treatment with calcitriol, and these are discussed. Areas of uncertainty, such as should affected mothers breastfeed their infants, are emphasized. PMID:24818008

  7. Water-Induced Dimensionality Reduction in Metal-Halide Perovskites

    KAUST Repository

    Turedi, Bekir

    2018-03-30

    Metal-halide perovskite materials are highly attractive materials for optoelectronic applications. However, the instability of perovskite materials caused by moisture and heat-induced degradation impairs future prospects of using these materials. Here we employ water to directly transform films of the three-dimensional (3D) perovskite CsPbBr3 to stable two-dimensional (2D) perovskite-related CsPb2Br5. A sequential dissolution-recrystallization process governs this water induced transformation under PbBr2 rich condition. We find that these post-synthesized 2D perovskite-related material films exhibit excellent stability against humidity and high photoluminescence quantum yield. We believe that our results provide a new synthetic method to generate stable 2D perovskite-related materials that could be applicable for light emitting device applications.

  8. Small polarons in 2D perovskites

    KAUST Repository

    Cortecchia, Daniele; Yin, Jun; Birowosuto, Muhammad D.; Lo, Shu-Zee A.; Gurzadyan, Gagik G.; Bruno, Annalisa; Bredas, Jean-Luc; Soci, Cesare

    2017-01-01

    We demonstrate that white light luminescence in two-dimensional (2D) perovskites stems from photoinduced formation of small polarons confined at specific sites of the inorganic framework in the form of self-trapped electrons and holes. We discuss their application in white light emitting devices and X-ray scintillators.

  9. Small polarons in 2D perovskites

    KAUST Repository

    Cortecchia, Daniele

    2017-11-02

    We demonstrate that white light luminescence in two-dimensional (2D) perovskites stems from photoinduced formation of small polarons confined at specific sites of the inorganic framework in the form of self-trapped electrons and holes. We discuss their application in white light emitting devices and X-ray scintillators.

  10. Characterization of the Valence and Conduction Band Levels of n = 1 2D Perovskites: A Combined Experimental and Theoretical Investigation

    KAUST Repository

    Silver, Scott; Yin, Jun; Li, Hong; Bredas, Jean-Luc; Kahn, Antoine

    2018-01-01

    This study presents a combined experimental and theoretical study of the electronic structure of two 2D metal halide perovskite films. Ultraviolet and inverse photoemission spectroscopies are performed on solution-processed thin films of the n = 1

  11. Developmental vitamin D deficiency causes abnormal brain development.

    Science.gov (United States)

    Eyles, D W; Feron, F; Cui, X; Kesby, J P; Harms, L H; Ko, P; McGrath, J J; Burne, T H J

    2009-12-01

    There is now clear evidence that vitamin D is involved in brain development. Our group is interested in environmental factors that shape brain development and how this may be relevant to neuropsychiatric diseases including schizophrenia. The origins of schizophrenia are considered developmental. We hypothesised that developmental vitamin D (DVD) deficiency may be the plausible neurobiological explanation for several important epidemiological correlates of schizophrenia namely: (1) the excess winter/spring birth rate, (2) increased incidence of the disease in 2nd generation Afro-Caribbean migrants and (3) increased urban birth rate. Moreover we have published two pieces of direct epidemiological support for this hypothesis in patients. In order to establish the "Biological Plausibility" of this hypothesis we have developed an animal model to study the effect of DVD deficiency on brain development. We do this by removing vitamin D from the diet of female rats prior to breeding. At birth we return all dams to a vitamin D containing diet. Using this procedure we impose a transient, gestational vitamin D deficiency, while maintaining normal calcium levels throughout. The brains of offspring from DVD-deficient dams are characterised by (1) a mild distortion in brain shape, (2) increased lateral ventricle volumes, (3) reduced differentiation and (4) diminished expression of neurotrophic factors. As adults, the alterations in ventricular volume persist and alterations in brain gene and protein expression emerge. Adult DVD-deficient rats also display behavioural sensitivity to agents that induce psychosis (the NMDA antagonist MK-801) and have impairments in attentional processing. In this review we summarise the literature addressing the function of vitamin D on neuronal and non-neuronal cells as well as in vivo results from DVD-deficient animals. Our conclusions from these data are that vitamin D is a plausible biological risk factor for neuropsychiatric disorders and that

  12. Tolerance factor rules for Sr1-x-yCaxBayMnO3 perovskites

    International Nuclear Information System (INIS)

    Dabrowski, B.; Chmaissem, O.; Mais, J.; Kolesnik, S.; Jorgensen, J.D.; Short, S.

    2003-01-01

    Synthesis of new perovskite Sr 1-x-y Ca x Ba y MnO 3-δ compounds is described in detail and dependence of their phase stability and structural distortions on the tolerance factor is discussed. Oxygen contents have been measured over extended temperature and composition ranges. Neutron powder diffraction was used to precisely measure the A-O and Mn-O bond lengths and derive accurate interatomic distances [Ca-O], [Sr-O], [Ba-O], and [Mn-O]. By using these parameters instead of tabulated ionic radii we have derived the functional dependence of the tolerance factor t=t(x,y,T,δ) on composition, temperature, and oxygen content. At a fixed oxygen content, the tolerance factor is an increasing function of temperature as a result of greater thermal expansion of the average bond relative to the bond. We find that the stability of the perovskite phase at high temperature is governed, as expected, by the magnitude of tolerance factor (t≤1) which can be adjusted by controlling the oxygen content 3-δ. This dependence of the tolerance factor on oxygen content and temperature can be utilized to design synthesis conditions for the controlled formation of the new, kinetically stable, perovskite phases

  13. Influence of hydration water on CH3NH3PbI3 perovskite films prepared through one-step procedure.

    Science.gov (United States)

    Wang, Ziyi; Yuan, Sijian; Li, Dahai; Jin, Feng; Zhang, Rongjun; Zhan, Yiqiang; Lu, Ming; Wang, Songyou; Zheng, Yuxiang; Guo, Junpeng; Fan, Zhiyong; Chen, Liangyao

    2016-10-31

    Organic-inorganic perovskites were fabricated through a one-step procedure with different levels of hydration water in precursor solutions. The optical properties of CH3NH3PbI3 films were investigated through spectroscopic ellipsometry and photoluminescence measurements. With the measured optical constants, the efficiency limit of perovskite solar cells is predicted with a detailed balance model. By comparing the optical measurement to that of planar heterojunction solar cells, we conclude that the radiative efficiency and porosity of the perovskite film significantly influence the performance of perovskite solar cells. An optimized hydration-water concentration is obtained for the 3CH3NH3I:1PbAc2•xH2O precursor solution. The results can provide guidance for further optimization of the device performance of perovskite solar cells by utilizing hydration water.

  14. Amine treatment induced perovskite nanowire network in perovskite solar cells: efficient surface passivation and carrier transport

    Science.gov (United States)

    Xiao, Ke; Cui, Can; Wang, Peng; Lin, Ping; Qiang, Yaping; Xu, Lingbo; Xie, Jiangsheng; Yang, Zhengrui; Zhu, Xiaodong; Yu, Xuegong; Yang, Deren

    2018-02-01

    In the fabrication of high efficiency organic-inorganic metal halide perovskite solar cells (PSCs), an additional interface modifier is usually applied for enhancing the interface passivation and carrier transport. In this paper, we develop an innovative method with in-situ growth of one-dimensional perovskite nanowire (1D PNW) network triggered by Lewis amine over the perovskite films. To our knowledge, this is the first time to fabricate PSCs with shape-controlled perovskite surface morphology, which improved power conversion efficiency (PCE) from 14.32% to 16.66% with negligible hysteresis. The amine molecule can passivate the trap states on the polycrystalline perovskite surface to reduce trap-state density. Meanwhile, as a fast channel, the 1D PNWs would promote carrier transport from the bulk perovskite film to the electron transport layer. The PSCs with 1D PNW modification not only exhibit excellent photovoltaic performances, but also show good stability with only 4% PCE loss within 30 days in the ambient air without encapsulation. Our results strongly suggest that in-situ grown 1D PNW network provides a feasible and effective strategy for nanostructured optoelectronic devices such as PSCs to achieve superior performances.

  15. Charge/orbital ordering structure in ordered perovskite Sm sub 1 sub / sub 2 Ba sub 1 sub / sub 2 MnO sub 3

    CERN Document Server

    Uchida, M; Akahoshi, D; Kumai, R; Tomioka, Y; Tokura, Y; Arima, T H

    2002-01-01

    In an A-site ordered perovskite manganite Sm sub 1 sub / sub 2 Ba sub 1 sub / sub 2 MnO sub 3 , a new charge/orbital ordering pattern was found at room temperature. Electron diffraction studies revealed a series of superlattice reflections with modulation vectors at q sub 2 =(1/2, 1/2, 1/2) as well as at q sub 1 =(1/4, 1/4, 0) in the tetragonal setting (a sub p x a sub p x 2a sub p , a sub p being the cubic perovskite lattice parameter). Together with the results of the resonant X-ray scattering and the charge-transport and magnetization measurements, a new model for the three-dimensional charge/orbital ordering in the ordered perovskite is proposed. (author)

  16. Crystal Structure Formation of CH3NH3PbI3-xClx Perovskite

    Directory of Open Access Journals (Sweden)

    Shiqiang Luo

    2016-02-01

    Full Text Available Inorganic-organic hydride perovskites bring the hope for fabricating low-cost and large-scale solar cells. At the beginning of the research, two open questions were raised: the hysteresis effect and the role of chloride. The presence of chloride significantly improves the crystallization and charge transfer property of the perovskite. However, though the long held debate over of the existence of chloride in the perovskite seems to have now come to a conclusion, no prior work has been carried out focusing on the role of chloride on the electronic performance and the crystallization of the perovskite. Furthermore, current reports on the crystal structure of the perovskite are rather confusing. This article analyzes the role of chloride in CH3NH3PbI3-xClx on the crystal orientation and provides a new explanation about the (110-oriented growth of CH3NH3PbI3 and CH3NH3PbI3-xClx.

  17. Observation of Internal Photoinduced Electron and Hole Separation in Hybrid Two-Dimentional Perovskite Films.

    Science.gov (United States)

    Liu, Junxue; Leng, Jing; Wu, Kaifeng; Zhang, Jun; Jin, Shengye

    2017-02-01

    Two-dimensional (2D) organolead halide perovskites are promising for various optoelectronic applications. Here we report a unique spontaneous charge (electron/hole) separation property in multilayered (BA) 2 (MA) n-1 Pb n I 3n+1 (BA = CH 3 (CH 2 ) 3 NH 3 + , MA = CH 3 NH 3 + ) 2D perovskite films by studying the charge carrier dynamics using ultrafast transient absorption and photoluminescence spectroscopy. Surprisingly, the 2D perovskite films, although nominally prepared as "n = 4", are found to be mixture of multiple perovskite phases, with n = 2, 3, 4 and ≈ ∞, that naturally align in the order of n along the direction perpendicular to the substrate. Driven by the band alignment between 2D perovskites phases, we observe consecutive photoinduced electron transfer from small-n to large-n phases and hole transfer in the opposite direction on hundreds of picoseconds inside the 2D film of ∼358 nm thickness. This internal charge transfer efficiently separates electrons and holes to the upper and bottom surfaces of the films, which is a unique property beneficial for applications in photovoltaics and other optoelectronics devices.

  18. The role of nonmagnetic d{sup 0} vs. d{sup 10}B-type cations on the magnetic exchange interactions in osmium double perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Hai L., E-mail: Hai.Feng@cpfs.mpg.de [Max Planck Institute for Chemical Physics of Solids, Dresden 01187 (Germany); Yamaura, Kazunari [Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Tjeng, Liu Hao [Max Planck Institute for Chemical Physics of Solids, Dresden 01187 (Germany); Jansen, Martin, E-mail: M.Jansen@fkf.mpg.de [Max Planck Institute for Chemical Physics of Solids, Dresden 01187 (Germany); Max Planck Institute for Solid State Research, Stuttgart 70569 (Germany)

    2016-11-15

    Polycrystalline samples of double perovskites Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) were synthesized by solid state reactions. They adopt the cubic double perovskite structures (space group, Fm-3m) with ordered B and Os arrangements. Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) show antiferromagnetic transitions at 93 K, 69 K, and 28 K, respectively. The Weiss-temperatures are −590 K for Ba{sub 2}ScOsO{sub 6}, −571 K for Ba{sub 2}YOsO{sub 6}, and −155 K for Ba{sub 2}InOsO{sub 6}. Sc{sup 3+} and Y{sup 3+} have the open-shell d{sup 0} electronic configuration, while In{sup 3+} has the closed-shell d{sup 10}. This indicates that a d{sup 0} B-type cation induces stronger overall magnetic exchange interactions in comparison to a d{sup 10}. Comparison of Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) to their Sr and Ca analogues shows that the structural distortions weaken the overall magnetic exchange interactions. - Graphical abstract: Magnetic properties of osmium double perovskites Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) were studied. Comparison of Ba{sub 2}BOsO{sub 6}indicates that a d{sup 0} B-type cation induces stronger overall magnetic exchange interactions in comparison to a d{sup 10}. - Highlights: • Magnetic properties of double perovskites Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) were studied. • A d{sup 0}B-type cation induces stronger magnetic interactions than a d{sup 10}. • Structural distortions weaken the overall Os{sup 5+}-Os{sup 5+} magnetic interactions.

  19. Efficient Lead-Free Solar Cells Based on Hollow {en}MASnI3 Perovskites.

    Science.gov (United States)

    Ke, Weijun; Stoumpos, Constantinos C; Spanopoulos, Ioannis; Mao, Lingling; Chen, Michelle; Wasielewski, Michael R; Kanatzidis, Mercouri G

    2017-10-18

    Tin-based perovskites have very comparable electronic properties to lead-based perovskites and are regarded as possible lower toxicity alternates for solar cell applications. However, the efficiency of tin-based perovskite solar cells is still low and they exhibit poor air stability. Here, we report lead-free tin-based solar cells with greatly enhanced performance and stability using so-called "hollow" ethylenediammonium and methylammonium tin iodide ({en}MASnI 3 ) perovskite as absorbers. Our results show that en can improve the film morphology and most importantly can serve as a new cation to be incorporated into the 3D MASnI 3 lattice. When the cation of en becomes part of the 3D structure, a high density of SnI 2 vacancies is created resulting in larger band gap, larger unit cell volume, lower trap-state density, and much longer carrier lifetime compared to classical MASnI 3 . The best-performing {en}MASnI 3 solar cell has achieved a high efficiency of 6.63% with an open circuit voltage of 428.67 mV, a short-circuit current density of 24.28 mA cm -2 , and a fill factor of 63.72%. Moreover, the {en}MASnI 3 device shows much better air stability than the neat MASnI 3 device. Comparable performance is also achieved for cesium tin iodide solar cells with en loading, demonstrating the broad scope of this approach.

  20. Micropatterned 2D Hybrid Perovskite Thin Films with Enhanced Photoluminescence Lifetimes

    NARCIS (Netherlands)

    Kamminga, Machteld E.; Fang, Hong Hua; Loi, Maria Antonietta; Ten Brink, Gert H.; Blake, Graeme R.; Palstra, Thomas T.M.; Ten Elshof, Johan E.

    2018-01-01

    The application of luminescent materials in display screens and devices requires micropatterned structures. In this work, we have successfully printed microstructures of a two-dimensional (2D), orange-colored organic/inorganic hybrid perovskite ((C6H5CH2NH3)2PbI4) using two different soft

  1. Characterization and carbon monoxide oxidation activity of La1-ySryCr1-xRuxO3 perovskites

    Directory of Open Access Journals (Sweden)

    C. MARINOVA

    2000-01-01

    Full Text Available The oxidation of CO over La1-ySryCr1-xRuxO3 perovskite type oxides with y=0.3 and 0 £ x £ 0.100 have been studied. X-ray fluorescence analysis confirmed that content of elements in the bulk corresponds to the established nominal perovskite stoichiometry, indicating that no significant oxidation of ruthenium into volatile polyvalent oxides with their consequented escape from the sample occurred in air up to the temperature of 1000°C. According to X-ray diffraction analysis, all sampls achieved the perovskite hexagonal with the presence of some SrCrO4. X-ray photoelectron spectroscopy analysis of ruthenium samples shows higher Ru and Sr surface concentraitions than in the bulk. The binding energy for Ru3p is virtually the same in all samples and consistent with that of Ru4+ (463.6-464.3eV. Kinetic studies were performed in a differential recycle reactor with a recycling ratio 80. The results show that substitution of Ru4+ for Cr3+ in La1-ySryCrO3 leads to a significant increase in both the activity and the activation energy. The global CO oxidation rate, referred on the BET surface area, correlates with the surface Ru4+ atomic concentraiton. Hence, the activity reflect the surface enrichment in ruthenium. Moreover, an identical apparent activation energy E = 93 kJ/mol and the same specific rate per ruthenium surface ion were obtained for samples with a Ru content x ³ 0.05 suggest that exposed Ru4+ ions mainly participate in the reaction.

  2. High-Pressure Single-Crystal Structures of 3D Lead-Halide Hybrid Perovskites and Pressure Effects on their Electronic and Optical Properties.

    Science.gov (United States)

    Jaffe, Adam; Lin, Yu; Beavers, Christine M; Voss, Johannes; Mao, Wendy L; Karunadasa, Hemamala I

    2016-04-27

    We report the first high-pressure single-crystal structures of hybrid perovskites. The crystalline semiconductors (MA)PbX3 (MA = CH3NH3 (+), X = Br(-) or I(-)) afford us the rare opportunity of understanding how compression modulates their structures and thereby their optoelectronic properties. Using atomic coordinates obtained from high-pressure single-crystal X-ray diffraction we track the perovskites' precise structural evolution upon compression. These structural changes correlate well with pressure-dependent single-crystal photoluminescence (PL) spectra and high-pressure bandgaps derived from density functional theory. We further observe dramatic piezochromism where the solids become lighter in color and then transition to opaque black with compression. Indeed, electronic conductivity measurements of (MA)PbI3 obtained within a diamond-anvil cell show that the material's resistivity decreases by 3 orders of magnitude between 0 and 51 GPa. The activation energy for conduction at 51 GPa is only 13.2(3) meV, suggesting that the perovskite is approaching a metallic state. Furthermore, the pressure response of mixed-halide perovskites shows new luminescent states that emerge at elevated pressures. We recently reported that the perovskites (MA)Pb(Br x I1-x )3 (0.2 < x < 1) reversibly form light-induced trap states, which pin their PL to a low energy. This may explain the low voltages obtained from solar cells employing these absorbers. Our high-pressure PL data indicate that compression can mitigate this PL redshift and may afford higher steady-state voltages from these absorbers. These studies show that pressure can significantly alter the transport and thermodynamic properties of these technologically important semiconductors.

  3. HASHIMOTO THYROIDITIS NOT ASSOCIATED WITH VITAMIN D DEFICIENCY.

    Science.gov (United States)

    Yasmeh, Joseph; Farpour, Farzin; Rizzo, Vincent; Kheradnam, Sharon; Sachmechi, Issac

    2016-07-01

    Vitamin D deficiency is associated with several autoimmune diseases. This study assessed whether vitamin D deficiency is associated with Hashimoto thyroiditis (HT). Two groups of patients were selected for which serum 25-hydroxyvitamin D (25(OH)D) levels had been measured: (1) a study group of patients diagnosed with HT as indicated by thyroid antibodies, and (2) a healthy control group. Each group was separated by sex and then controlled for age and body mass index (BMI). Groups' mean 25(OH)D levels were compared by analysis of variance (ANOVA), and percent frequencies of vitamin D sufficiency, insufficiency, and deficiency were compared with a Z-test. The correlations between 25(OH)D levels and thyroid antibodies and thyroid-stimulating hormone (TSH) levels were also tested. The mean 25(OH)D levels for the HT and control groups were significantly different in females (30.75 vs. 27.56 ng/mL, respectively) but not in males (14.24 vs. 13.26 ng/mL). HT females had a higher rate of vitamin D sufficiency (51.7% vs. 31.1%) and a lower rate of insufficiency (48.3% vs. 68.9%) relative to control females. No such differences were found in the male groups. None of the females were vitamin D deficient, but almost all males were. A significant (P = .016) positive correlation (rs = 0.436) between 25(OH)D and TPOAb was observed in males. HT is not associated with higher rates of vitamin D deficiency relative to a control group. BMI = body mass index HT = Hashimoto thyroiditis 25(OH)D = 25-hydroxyvitamin D TgAb = thyroglobulin antibody TSH = thyroid-stimulating hormone TPOAb = thyroid-peroxidase antibody VDR = Vitamin D receptor.

  4. Low-Dimensional Organic Tin Bromide Perovskites and Their Photoinduced Structural Transformation.

    Science.gov (United States)

    Zhou, Chenkun; Tian, Yu; Wang, Mingchao; Rose, Alyssa; Besara, Tiglet; Doyle, Nicholas K; Yuan, Zhao; Wang, Jamie C; Clark, Ronald; Hu, Yanyan; Siegrist, Theo; Lin, Shangchao; Ma, Biwu

    2017-07-24

    Hybrid organic-inorganic metal halide perovskites possess exceptional structural tunability, with three- (3D), two- (2D), one- (1D), and zero-dimensional (0D) structures on the molecular level all possible. While remarkable progress has been realized in perovskite research in recent years, the focus has been mainly on 3D and 2D structures, with 1D and 0D structures significantly underexplored. The synthesis and characterization of a series of low-dimensional organic tin bromide perovskites with 1D and 0D structures is reported. Using the same organic and inorganic components, but at different ratios and reaction conditions, both 1D (C 4 N 2 H 14 )SnBr 4 and 0D (C 4 N 2 H 14 Br) 4 SnBr 6 can be prepared in high yields. Moreover, photoinduced structural transformation from 1D to 0D was investigated experimentally and theoretically in which photodissociation of 1D metal halide chains followed by structural reorganization leads to the formation of a more thermodynamically stable 0D structure. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Plastic Properties of MgSiO3 Post-Perovskite in the Lower Mantle : Do We Care about Twinning ?

    Science.gov (United States)

    Carrez, P.; Goryaeva, A.; Cordier, P.

    2017-12-01

    Plastic properties of post-perovskite MgSiO3 are believed to be one of the key issues for the understanding of seismic anisotropy at the bottom of the D'' layer. Unfortunately, results from high pressure deformation experiments have led to several conflicting interpretations regarding slip systems and dislocation activities. Whereas, plastic slip has attracted much more attention, twinning mechanism has not been addressed despite some experimental evidence on low-pressure analogues. Based on a hierarchical mechanical model of the emission of 1/6 partial dislocations, we present a twin nucleation model in MgSiO3 and CaIrO3 post-perovskite. Relying on first-principles calculations, we show that {110} twin wall formation resulting from the interaction of multiple twin dislocations occurs for twinning stress comparable to the easiest slip system in post-perovskite. Dislocations activities and twinning being competitive strain producing mechanism, twinning has to be considered in future interpretation of crystallographic preferred orientations in post-perovskite.

  6. Vitamin D Deficiency among Newborns in Amman, Jordan

    Science.gov (United States)

    Khuri-Bulos, Najwa; Lang, Ryan D.; Blevins, Meridith; Kudyba, Katherine; Lawrence, Lindsey; Davidson, Mario; Faouri, Samir; Halasa, Natasha B.

    2014-01-01

    Objective: Vitamin D deficiency is well recognized in selected Middle Eastern countries, but neonatal vitamin D status is not well studied in Jordan and other nearby countries. The aim of this study is to determine the prevalence of vitamin D deficiency in Jordanian newborns and risk factors associated with low levels. Methods: This is a prospective cohort study of newborn infants who were delivered at the Al Bashir Government Hospital in Amman, Jordan, from January 31, 2010, to January 27, 2011. Heel stick blood samples for 25-hydroxyvitamin D [25(OH)D] levels were obtained within 96 hours of birth. Maternal dress pattern, vitamin supplementation, smoke exposure during pregnancy, mode of delivery, gestational age, and birth weight were documented. Results: Samples were obtained from 3,731 newborns. Median gestational age was 39 weeks, median birth weight was 3.1 kilograms, median maternal age was 27 years, and median newborn 25(OH)D level was 8.6nmol/L. A total of 3,512 newborns (94.1%) in this study were vitamin D deficient (< 50 nmol/L). Lower gestational age, maternal smoke exposure, and birth during winter months were associated with lower infant vitamin D levels, while vitamin D supplementation and time spent outside during pregnancy were associated with higher vitamin D levels. Conclusions: The prevalence of severely low vitamin D levels in newborn infants in Amman, Jordan, is substantial, even in newborns born during the spring and summer months. Vitamin D supplementation is needed in this population. PMID:24373276

  7. Determination of stoichiometry and concentration of trace elements in thin BaxSr1-xTiO3 perovskite layers.

    Science.gov (United States)

    Becker, J S; Boulyga, S F

    2001-07-01

    This paper describes an analytical procedure for determining the stoichiometry of BaxSr1-xTiO3 perovskite layers using inductively coupled plasma mass spectrometry (ICP-MS). The analytical results of mass spectrometry measurements are compared to those of X-ray fluorescence analysis (XRF). The performance and the limits of solid-state mass spectrometry analytical methods for the surface analysis of thin BaxSr1-xTiO3 perovskite layers sputtered neutral mass spectrometry (SNMS)--are investigated and discussed.

  8. Luminescence of Mn{sup 4+} in the orthorhombic perovskite, LaGaO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, A.M., E-mail: srivastava@ge.com [GE Global Research, One Research Circle, Niskayuna, New York 12309 (United States); Camardello, S.J. [GE Global Research, One Research Circle, Niskayuna, New York 12309 (United States); Brik, M.G. [College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); Institute of Physics, University of Tartu, Ravila 14C, Tartu 50411 (Estonia); Institute of Physics, Jan Dlugosz University, PL-42200 Czestochowa (Poland)

    2017-03-15

    The optical properties of Mn{sup 4+} (3d{sup 3}) in the orthorhombic perovskite, LaGaO{sub 3} are investigated. The Mn{sup 4+} energy levels are calculated using the exchange charge model of crystal-field theory. The calculated Mn{sup 4+} energy levels are in good agreement with the experimental spectroscopic data. The results of our calculations yield the crystal-field splitting and Racah parameters of Dq=1926 cm{sup −1}, B=780 cm{sup −1} and C=2878 cm{sup −1}, with C/B=3.7. The emission spectrum is assigned on the basis of the zero phonon line corresponding to the {sup 2}E{sub g}→{sup 4}A{sub 2g} transition and its vibrational sidebands. A comparative study of the variation in the crystal-field splitting and the Mn{sup 4+} {sup 2}E{sub g} energy level position in materials with the perovskite structure is also presented.

  9. Phase Stability and Electronic Structure of Prospective Sb-Based Mixed Sulfide and Iodide 3D Perovskite (CH3NH3)SbSI2.

    Science.gov (United States)

    Li, Tianyang; Wang, Xiaoming; Yan, Yanfa; Mitzi, David B

    2018-06-29

    Lead-free antimony-based mixed sulfide and iodide perovskite phases have recently been reported to be synthesized experimentally and to exhibit reasonable photovoltaic performance. Through a combination of experimental validation and computational analysis, we show no evidence of the formation of the mixed sulfide and iodide perovskite phase, MASbSI 2 (MA = CH 3 NH 3 + ), and instead that the main products are a mixture of the binary and ternary compounds (Sb 2 S 3 and MA 3 Sb 2 I 9 ). Density functional theory calculations also indicate that such a mixed sulfide and iodide perovskite phase should be thermodynamically less stable compared with binary/ternary anion-segregated secondary phases and less likely to be synthesized under equilibrium conditions. Additionally, band structure calculations show that this mixed sulfide and iodide phase, if possible to synthesize (e.g., under nonequilibrium conditions), should have a suitable direct band gap for photovoltaic application.

  10. Modeling defects and plasticity in MgSiO3 post-perovskite: Part 1-generalized stacking faults.

    Science.gov (United States)

    Goryaeva, Alexandra M; Carrez, Philippe; Cordier, Patrick

    In this work, we examine the transferability of a pairwise potential model (derived for MgSiO 3 perovskite) to accurately compute the excess energies of the generalized stacking faults (GSF, also called γ -surfaces) in MgSiO 3 post-perovskite. All calculations have been performed at 120 GPa, a pressure relevant to the D″ layer. Taking into account an important aspect of crystal chemistry for complex materials, we consider in detail all possible locations of slip planes in the post-perovskite structure. The γ -surface calculations emphasize the easiness of glide of slip systems with the smallest shear vector [100] and of the [001](010) slip system. Our results are in agreement with previous ab initio calculations. This validates the use the chosen potential model for further full atomistic modeling of dislocations in MgSiO 3 post-perovskite.

  11. Vitamin D deficiency and its risk factors in Malaysian children with epilepsy.

    Science.gov (United States)

    Fong, Choong Yi; Kong, Ann Nie; Poh, Bee Koon; Mohamed, Ahmad Rithauddin; Khoo, Teik Beng; Ng, Rui Lun; Noordin, Mazidah; Nadarajaw, Thiyagar; Ong, Lai Choo

    2016-08-01

    Long-term use of antiepileptic drugs (AEDs) is a significant risk factor for vitamin D deficiency in children with epilepsy. The aims of our study were to evaluate the prevalence and risk factors for vitamin D deficiency among Malaysian children with epilepsy. Cross-sectional study of ambulant children with epilepsy on long-term AEDs for >1 year seen in three tertiary hospitals in Malaysia from April 2014 to April 2015. Detailed assessment of pubertal status, skin pigmentation, sunshine exposure behavior, physical activity, dietary vitamin D and calcium intake, anthropometric measurements and bone health blood tests (vitamin D, alkaline phosphatase, calcium, phosphate, and parathyroid hormone levels) were obtained on all patients. Vitamin D deficiency was defined as 25-hydroxy vitamin D [25(OH)D] levels ≤35 nmol/L and insufficiency as 25(OH)D levels of 36-50 nmol/L. A total of 244 children (146 male) participated in the study. Ages ranged between 3.7 and 18.8 years (mean 12.3 years). 25(OH)D levels ranged between 7.5 and 140.9 nmol/L (mean 53.9 nmol/L). Vitamin D deficiency was identified in 55 patients (22.5%), and a further 48 (19.7%) had vitamin D insufficiency. Multivariate logistic regression analysis identified polytherapy >1 AED (odds ratio [OR] 2.16, 95% confidence interval [CI] 1.07-4.36), age >12 years (OR 4.16, 95% CI 1.13-15.30), Indian ethnicity (OR 6.97, 95% CI 2.48-19.55), sun exposure time 30-60 min/day (OR 2.44, 95% CI 1.05-5.67), sun exposure time <30 min/day (OR 3.83, 95% CI 1.61-9.09), and female (OR 2.61, 95% CI 1.31-5.20) as statistically significant (p < 0.05) risk factors for vitamin D deficiency. Despite living in the tropics, a high proportion of Malaysian children with epilepsy are at risk of vitamin D deficiency. Targeted strategies including vitamin D supplementation and lifestyle advice of healthy sunlight exposure behavior should be implemented among children with epilepsy, particularly for those at high risk of having vitamin D

  12. A niobium and tantalum co-doped perovskite cathode for solid oxide fuel cells operating below 500 °C

    Science.gov (United States)

    Li, Mengran; Zhao, Mingwen; Li, Feng; Zhou, Wei; Peterson, Vanessa K.; Xu, Xiaoyong; Shao, Zongping; Gentle, Ian; Zhu, Zhonghua

    2017-01-01

    The slow activity of cathode materials is one of the most significant barriers to realizing the operation of solid oxide fuel cells below 500 °C. Here we report a niobium and tantalum co-substituted perovskite SrCo0.8Nb0.1Ta0.1O3−δ as a cathode, which exhibits high electroactivity. This cathode has an area-specific polarization resistance as low as ∼0.16 and ∼0.68 Ω cm2 in a symmetrical cell and peak power densities of 1.2 and 0.7 W cm−2 in a Gd0.1Ce0.9O1.95-based anode-supported fuel cell at 500 and 450 °C, respectively. The high performance is attributed to an optimal balance of oxygen vacancies, ionic mobility and surface electron transfer as promoted by the synergistic effects of the niobium and tantalum. This work also points to an effective strategy in the design of cathodes for low-temperature solid oxide fuel cells. PMID:28045088

  13. Quantum Dots in Two-Dimensional Perovskite Matrices for Efficient Near-Infrared Light Emission

    KAUST Repository

    Yang, Zhenyu

    2017-03-13

    Quantum-dot-in-perovskite solids are excellent candidates for infrared light-emitting applications. The first generation of dot-in-perovskite light-emitting diodes (LEDs) has shown bright infrared electroluminescence with tunable emission wavelength; however, their performance has been limited by degradation of the active layer at practical operating voltages. This arises from the instability of the three-dimensional (3D) organolead halide perovskite matrix. Herein we report the first dot-in-perovskite solids that employ two-dimensional (2D) perovskites as the matrix. 2D perovskite passivation is achieved via an in situ alkylammonium/alkylamine substitution carried out during the quantum dot (QD) ligand exchange process. This single-step film preparation process enables deposition of the QD/perovskite active layers with thicknesses of 40 nm, over seven times thinner than the first-generation dot-in-perovskite thin films that relied on a multistep synthesis. The dot-in-perovskite film roughness improved from 31 nm for the first-generation films to 3 nm for films as a result of this new approach. The best devices exhibit external quantum efficiency peaks exceeding 2% and radiances of ∼1 W sr–1 m–2, with an improved breakdown voltage up to 7.5 V. Compared to first-generation dot-in-perovskites, this new process reduces materials consumptions 10-fold and represents a promising step toward manufacturable devices.

  14. Quantum Dots in Two-Dimensional Perovskite Matrices for Efficient Near-Infrared Light Emission

    KAUST Repository

    Yang, Zhenyu; Voznyy, Oleksandr; Walters, Grant; Fan, James Z.; Liu, Min; Kinge, Sachin; Hoogland, Sjoerd; Sargent, Edward H.

    2017-01-01

    Quantum-dot-in-perovskite solids are excellent candidates for infrared light-emitting applications. The first generation of dot-in-perovskite light-emitting diodes (LEDs) has shown bright infrared electroluminescence with tunable emission wavelength; however, their performance has been limited by degradation of the active layer at practical operating voltages. This arises from the instability of the three-dimensional (3D) organolead halide perovskite matrix. Herein we report the first dot-in-perovskite solids that employ two-dimensional (2D) perovskites as the matrix. 2D perovskite passivation is achieved via an in situ alkylammonium/alkylamine substitution carried out during the quantum dot (QD) ligand exchange process. This single-step film preparation process enables deposition of the QD/perovskite active layers with thicknesses of 40 nm, over seven times thinner than the first-generation dot-in-perovskite thin films that relied on a multistep synthesis. The dot-in-perovskite film roughness improved from 31 nm for the first-generation films to 3 nm for films as a result of this new approach. The best devices exhibit external quantum efficiency peaks exceeding 2% and radiances of ∼1 W sr–1 m–2, with an improved breakdown voltage up to 7.5 V. Compared to first-generation dot-in-perovskites, this new process reduces materials consumptions 10-fold and represents a promising step toward manufacturable devices.

  15. Factors Associated with Vitamin D Testing, Deficiency, Intake, and Supplementation in Patients with Chronic Pain.

    Science.gov (United States)

    Gaikwad, Manasi; Vanlint, Simon; Moseley, G Lorimer; Mittinty, Murthy N; Stocks, Nigel

    2017-11-02

    Vitamin D deficiency is a public health issue, with reports of six- to twenty-five-fold rise in vitamin D testing. Vitamin D deficiency has been linked to many chronic diseases such as diabetes mellitus, cardiovascular disease, depression, and chronic pain. Identifying factors associated with risk of deficiency in individuals with chronic pain will help minimize time and cost. This study aims to examine the factors associated with vitamin D testing, intake, and physician-advised supplementation in individuals with chronic pain. Using a cross-sectional design, data were collected from 465 individuals with chronic pain. These data were analyzed using penalized logistic regression with the LASSO technique. Fifty-seven percent reported being tested for vitamin D, about 40% reported being diagnosed with vitamin D deficiency, and of those who had been tested, 60% reported taking vitamin D supplementation. The findings suggest older age (OR 3.12, CI [1.02, 9.50]) and higher mean pain intensity score (OR 2.02, CI [1.13, 3.59]) increased an individual's chance of being vitamin D deficient. Unemployment or on leave due to pain (OR 1.79, [CI 1.03, 3.11]), part-time employment (OR 1.86, CI [1.02, 3.39]), and being a resident of Australia (OR 2.32, CI [1.13, 4.72]) increased chances of being tested for vitamin D. Being diagnosed with vitamin D deficiency (OR 6.67, CI [2.75, 16.19]), unemployed or on leave due to pain (OR 3.71, CI [1.25, 11.00]), and in part-time employment (OR 2.69, CI [0.86, 8.38]) were associated with physician-advised vitamin D supplementation. Our results may have practical implications, as identifying pretest risk factors may assist in identifying who is at risk of vitamin D deficiency, whom to test, and when to treat.

  16. High-pressure synthesis and structural, physical properties of CaIr1-xPtxO3 and CaIr1-xRhxO3

    Science.gov (United States)

    Hirai, S.; Bromiley, G. D.; Klemme, S.; Irifune, T.; Ohfuji, H.; Attfield, P.; Nishiyama, N.

    2010-12-01

    in terms of materials science applications. To our knowledge, this will be the first report on structural, magnetic and charge-transport properties of B-site substituted solid solutions of post-perovskite oxides with 4d/5d transition metals. High-quality polycrystalline samples of CaIr1-xPtxO3 and CaIr1-xRhxO3 have been obtained at high pressures, and structural, magnetic and charge-transport properties of the compounds will be reported. ODF analysis reveals that solutions of CaIrO3, CaPtO3 and CaRhO3 exhibit similar grain growth features to the mother compound, although growth in [0 1 0] plays a more dominant role than the growth in [0 0 1] for the solid solutions. CaIrO3 is a characteristic hard magnet suitable for applications such as magnetic recording, with TN = 108K. A new phase of CaIr1-xPtxO3 synthesized at a high P/T condition has Raman modes which resemble those of CaIrO3 perovskite, suggesting this phase has a perovskite structure.The instability of the perovskite phase of CaIr1-xPtxO3 reveals why the post-perovskite to peovskite phase transition has not been observed for CaPtO3 unlike the case for CaIrO3, CaRhO3 and CaRuO3.

  17. Ultralow Self-Doping in 2D Hybrid Perovskite Single Crystals

    KAUST Repository

    Peng, Wei

    2017-06-28

    Unintentional self-doping in semiconductors through shallow defects is detrimental to optoelectronic device performance. It adversely affects junction properties and it introduces electronic noise. This is especially acute for solution-processed semiconductors, including hybrid perovskites, which are usually high in defects due to rapid crystallization. Here, we uncover extremely low self-doping concentrations in single crystals of (C6H5C2H4NH3)2PbI4・(CH3NH3PbI3)n-1 (n=1, 2, and 3)—over three orders of magnitude lower than those of typical three-dimensional hybrid perovskites—by analyzing their conductivity behavior. We propose that crystallization of hybrid perovskites containing large organic cations suppresses defect formation and thus favors a low self-doping level. To exemplify the benefits of this effect, we demonstrate extraordinarily high light-detectivity (1013 Jones) in (C6H5C2H4NH3)2PbI4・(CH3NH3PbI3)n-1 photoconductors due to the reduced electronic noise, which makes them particularly attractive for the detection of weak light signals. Furthermore, the low self-doping concentration reduces the equilibrium charge carrier concentration in (C6H5C2H4NH3)2PbI4・(CH3NH3PbI3)n-1, advantageous in the design of p-i-n heterojunction solar cells by optimizing band alignment and promoting carrier depletion in the intrinsic perovskite layer, thereby enhancing charge extraction.

  18. Efficient CH3NH3PbI3 perovskite/fullerene planar heterojunction hybrid solar cells with oxidized Ni/Au/Cu transparent electrode

    Science.gov (United States)

    Lai, Wei-Chih; Lin, Kun-Wei; Guo, Tzung-Fang; Chen, Peter; Liao, Yuan-Yu

    2018-02-01

    We demonstrated the performance of inverted CH3NH3PbI3 perovskite-based solar cells (SCs) with a thermally oxidized nickel/gold/copper (Ni/Au/Cu) trilayer transparent electrode. Oxidized Ni/Au/Cu is a high transparent layer and has less resistance than the oxidized Ni/Au layer. Like the oxidized Ni/Au layer, oxidized Ni and Cu in oxidized Ni/Au/Cu could perform as a hole transport layer of the perovskite-based SCs. It leads to improved perovskite SC performance on an open circuit voltage of 1.01 V, a short circuit current density of 14.36 mA/cm2, a fill factor of 76.7%, and a power conversion efficiency (η%) of 11.1%. The η% of perovskite SCs with oxidized Ni (10 nm)/Au (6 nm)/Cu (1 nm) improved by approximately 10% compared with that of perovskite SCs with oxidized Ni/Au.

  19. Low-Dimensional Organic-Inorganic Halide Perovskite: Structure, Properties, and Applications.

    Science.gov (United States)

    Misra, Ravi K; Cohen, Bat-El; Iagher, Lior; Etgar, Lioz

    2017-10-09

    Three-dimensional (3D) perovskite has attracted a lot of attention owing to its success in photovoltaic (PV) solar cells. However, one of its major crucial issues lies in its stability, which has limited its commercialization. An important property of organic-inorganic perovskite is the possibility of forming a layered material by using long organic cations that do not fit into the octahedral cage. These long organic cations act as a "barrier" that "caps" 3D perovskite to form the layered material. Controlling the number of perovskite layers could provide a confined structure with chemical and physical properties that are different from those of 3D perovskite. This opens up a whole new batch of interesting materials with huge potential for optoelectronic applications. This Minireview presents the synthesis, properties, and structural orientation of low-dimensional perovskite. It also discusses the progress of low-dimensional perovskite in PV solar cells, which, to date, have performance comparable to that of 3D perovskite but with enhanced stability. Finally, the use of low-dimensional perovskite in light-emitting diodes (LEDs) and photodetectors is discussed. The low-dimensional perovskites are promising candidates for LED devices, mainly because of their high radiative recombination as a result of the confined low-dimensional quantum well. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Stability and carrier mobility of organic-inorganic hybrid perovskite CH3NH3PbI3 in two-dimensional limit

    Science.gov (United States)

    Huang, Kui; Lai, Kang; Yan, Chang-Lin; Zhang, Wei-Bing

    2017-10-01

    Recently, atomically thin organic-inorganic hybrid perovskites have been synthesized experimentally, which opens up new opportunities for exploring their novel properties in the 2D limit. Based on the comparative density functional theory calculation with and without spin-orbit coupling effects, the stability, electronic structure, and carrier mobility of the two-dimensional organic-inorganic hybrid perovskites MAPbI3 (MA = CH3NH3) have been investigated systemically. Two single-unit-cell-thick 2D MAPbI3 terminated by PbI2 and CH3NH3I are constructed, and their thermodynamic stabilities are also evaluated using the first-principles constrained thermodynamics method. Our results indicate that both 2D MAPbI3 with different terminations can be stable under certain conditions and have a suitable direct bandgap. Moreover, they are also found to have termination-dependent band edge and carrier mobility. The acoustic-phonon-limited carrier mobilities estimated using the deformation theory and effective mass approximation are on the order of thousands of square centimeters per volt per second and also highly anisotropic. These results indicate that 2D MAPbI3 are competitive candidates for low-dimensional photovoltaic applications.

  1. A New Lead Iodide Perovskite based on Large Organic Cation for Solar Cell Application.

    Science.gov (United States)

    Ma, Chunqing; Shen, Dong; Lo, Ming Fai; Lee, Chun-Sing

    2018-06-06

    Methylammonium (CH3NH3+) and formamidinium ((NH2)2CH+) based lead iodide perovskites are currently the two commonly used organic-inorganic lead iodide perovskites for solar cell application. Till now, there is still no alternative organic cations, which can produce perovskites with bandgaps spanning the visible spectrum (i.e. solar cell application. Here, a new perovskite using large propane-1,3-diammonium cation (n-Pr(NH3)22+) with a chemical structure of (n-Pr(NH3)2)0.5PbI3 is demonstrated. X-ray diffraction (XRD) result shows that the new perovskite exhibits a three-dimensional (3D), tetragonal phase. The bandgap of the new perovskite is ~ 1.6 eV, which is desirable for photovoltaic application. A (n-Pr(NH3)2)0.5PbI3 perovskite solar cell (PSC) yields a power conversion efficiency (PCE) of 5.1%. More importantly, this new perovskite is composed of larger hydrophobic cation that provides a better moisture resistance compared to CH3NH3PbI3 perovskite. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Oxygen vacancies at the spinel/perovskite γ-Al{sub 2}O{sub 3}/SrTiO{sub 3} heterointerface probed by resonant photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Schuetz, Philipp; Pfaff, Florian; Zapf, Michael; Gabel, Judith; Dudy, Lenart; Berner, Goetz; Sing, Michael; Claessen, Ralph [Physikalisches Institut and Roentgen Center for Complex Material Systems (RCCM), Universitaet Wuerzburg (Germany); Chen, Yunzhong; Pryds, Nini [Department of Energy Conversion and Storage, Technical University of Denmark, Risoe (Denmark); Schlueter, Christoph; Lee, Tien-Lin [Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot (United Kingdom)

    2016-07-01

    The spinel/perovskite heterointerface between the band insulators γ-Al{sub 2}O{sub 3} and SrTiO{sub 3} hosts a two-dimensional electron system (2DES) with exceptionally high electron mobility. Soft x-ray resonant photoelectron spectroscopy at the Ti L absorption edge is used to probe the Ti 3d derived interface states. Marked differences in the resonance behavior are found for the SrTiO{sub 3} valence band and the different interface states, which are observed in the band gap of SrTiO{sub 3}. A comparison to X-ray absorption spectra of Ti 3d{sup 0} and Ti 3d{sup 1} systems reveals the presence of different types of electronic states with Ti 3d character, i.e., oxygen vacancy induced, trapped in-gap states and itinerant states contributing to the 2DES. Exposure to low doses of oxygen during irradiation allows for the reversible manipulation of the oxygen stoichiometry, thus revealing the presence of an oxygen vacancy-induced state, which is characteristic for this spinel/perovskite interface.

  3. Possible association between vitamin D deficiency and restless legs syndrome

    Directory of Open Access Journals (Sweden)

    Oran M

    2014-05-01

    Full Text Available Mustafa Oran,1 Cuneyt Unsal,2 Yakup Albayrak,2 Feti Tulubas,3 Keriman Oguz,4 Okan Avci,1 Nilda Turgut,4 Recep Alp,4 Ahmet Gurel3 1Department of Internal Medicine, 2Department of Psychiatry, 3Department of Biochemistry, 4Department of Neurology, Namik Kemal University, Faculty of Medicine, Tekirdağ, Turkey Background and aim: Restless legs syndrome (RLS is a distressing sleep disorder that occurs worldwide. Although there have been recent developments in understanding the pathophysiology of RLS, the exact mechanism of the disease has not been well elucidated. An increased prevalence of neurologic and psychiatric diseases involving dopaminergic dysfunction in vitamin D-deficient patients led us to hypothesize that vitamin D deficiency might result in dopaminergic dysfunction and consequently, the development of RLS (in which dopaminergic dysfunction plays a pivotal role. Thus, the aim of this study was to evaluate the relationship between vitamin D deficiency and RLS. Methods: One hundred and fifty-five consecutive patients, 18–65 years of age, who were admitted to the Department of Internal Medicine with musculoskeletal symptoms and who subsequently underwent neurological and electromyography (EMG examination by the same senior neurologist, were included in this study. The patients were divided into two groups according to serum 25-hydroxyvitamin D (25(OHD (a vitamin D metabolite used as a measure of vitamin D status level: 36 patients with serum 25(OHD levels ≥20 ng/mL comprised the normal vitamin D group, and 119 patients with serum 25(OHD levels <20 ng/mL comprised the vitamin D deficiency group. The two groups were compared for the presence of RLS and associated factors. Results: The two groups were similar in terms of mean age, sex, mean body mass index (BMI, and serum levels of calcium, phosphate, alkaline phosphatase (ALP, and ferritin. The presence of RLS was significantly higher in the vitamin D deficiency group (χ2=12.87, P<0

  4. The electronic and optical properties of CH3NH3MoI3 perovskite

    Science.gov (United States)

    Kansara, Shivam; Sonvane, Yogesh; Gupta, Sanjeev K.

    2018-05-01

    In this work, a first-principles theoretical study of hybrid perovskite CH3NH3MoI3 is performed using PBE exchange-correlation approximations in density functional theory. The results of electronic band structure are 0.90 eV (M-point: Direct) and 0.60 eV (R-X point: Indirect), respectively. We have also calculated the dielectric properties such as real, imaginary, extension coefficient (K) and reflectivity (R) properties of hybrid perovskite CH3NH3MoI3. The low-bandgap molecules are used to absorb near-IR range and typically having a bandgap smaller than 1.6 eV. This is particularly attractive in organic photovoltaics (OPV), photodetectors (PDs), and ambipolar field-effect transistors (FETs).

  5. General Strategy for Rapid Production of Low-Dimensional All-Inorganic CsPbBr3 Perovskite Nanocrystals with Controlled Dimensionalities and Sizes.

    Science.gov (United States)

    Liu, Wenna; Zheng, Jinju; Cao, Sheng; Wang, Lin; Gao, Fengmei; Chou, Kuo-Chih; Hou, Xinmei; Yang, Weiyou

    2018-02-05

    Currently, all-inorganic CsPbX 3 (X = Br, I, Cl) perovskite nanocrystals (NCs) are shining stars with exciting potential applications in optoelectronic devices such as solar cells, light-emitting diodes, lasers, and photodetectors, due to their superior performance in comparison to their organic-inorganic hybrid counterparts. In the present work, we report a general strategy based on a microwave technique for the rapid production of low-dimensional all-inorganic CsPbBr 3 perovskite NCs with tunable morphologies within minutes. The effect of the key parameters such as the introduced ligands, solvents, and PbBr 2 precursors and microwave powers as well as the irradiation times on the production of perovskite NCs was systematically investigated, which allowed their growth with tunable dimensionalities and sizes. As a proof of concept, the ratio of OA to OAm as well as the concentration of PbBr 2 precursor played important roles in triggering the anisotropic growth of the perovskite NCs, favoring their growth into 1D/2D single-crystalline nanostructures. Meanwhile, their sizes could be tailored by controlling the microwave powers and irradiation times. The mechanism for the tunable growth of perovskite NCs is discussed.

  6. Facile Synthesis of CeO2-LaFeO3 Perovskite Composite and Its Application for 4-(Methylnitrosamino-1-(3-Pyridyl-1-Butanone (NNK Degradation

    Directory of Open Access Journals (Sweden)

    Kaixuan Wang

    2016-04-01

    Full Text Available A facile and environmentally friendly surface-ion adsorption method using CeCO3OH@C as template was demonstrated to synthesize CeO2-LaFeO3 perovskite composite material. The obtained composite was characterized by X-ray diffraction (XRD, fourier transform infrared spectra (FT-IR, field-emission scanning electron microscopy (FE-SEM, transmission electron microscopy (TEM, thermo-gravimetric analysis and differential scanning calorimetry (TG-DSC, N2 adsorption/desorption isotherms and X-ray photoelectron spectra (XPS measurements. The catalytic degradation of nitrosamine 4-(methylnitrosamino-1-(3-pyridyl-1-butanone (NNK was tested to evaluate catalytic activity of the CeO2-LaFeO3 composite. Much better activity was observed for the CeO2-LaFeO3 composite comparing with CeO2 and LaFeO3. These results suggested that perovskite composite materials are a promising candidate for the degradation of tobacco-specific nitrosamines (TSNAs.

  7. Water-Induced Dimensionality Reduction in Metal-Halide Perovskites

    KAUST Repository

    Turedi, Bekir; Lee, Kwangjae; Dursun, Ibrahim; Alamer, Badriah Jaber; Wu, Zhennan; Alarousu, Erkki; Mohammed, Omar F.; Cho, Namchul; Bakr, Osman

    2018-01-01

    . Here we employ water to directly transform films of the three-dimensional (3D) perovskite CsPbBr3 to stable two-dimensional (2D) perovskite-related CsPb2Br5. A sequential dissolution-recrystallization process governs this water induced transformation

  8. Polarized emission from CsPbX3 perovskite quantum dots

    Science.gov (United States)

    Wang, Dan; Wu, Dan; Dong, Di; Chen, Wei; Hao, Junjie; Qin, Jing; Xu, Bing; Wang, Kai; Sun, Xiaowei

    2016-06-01

    Compared to organic/inorganic hybrid perovskites, full inorganic perovskite quantum dots (QDs) exhibit higher stability. In this study, full inorganic CsPbX3 (X = Br, I and mixed halide systems Br/I) perovskite QDs have been synthesized and interestingly, these QDs showed highly polarized photoluminescence which is systematically studied for the first time. Furthermore, the polarization of CsPbI3 was as high as 0.36 in hexane and 0.40 as a film. The CsPbX3 perovskite QDs with high polarization properties indicate that they possess great potential for application in new generation displays with wide colour gamut and low power consumption.Compared to organic/inorganic hybrid perovskites, full inorganic perovskite quantum dots (QDs) exhibit higher stability. In this study, full inorganic CsPbX3 (X = Br, I and mixed halide systems Br/I) perovskite QDs have been synthesized and interestingly, these QDs showed highly polarized photoluminescence which is systematically studied for the first time. Furthermore, the polarization of CsPbI3 was as high as 0.36 in hexane and 0.40 as a film. The CsPbX3 perovskite QDs with high polarization properties indicate that they possess great potential for application in new generation displays with wide colour gamut and low power consumption. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01915c

  9. A new-type inorganic [KNbO{sub 3}]{sub 0.9}[BaCo{sub 1/2}Nb{sub 1/2}O{sub 3-δ}]{sub 0.1} perovskite oxide as sensitizer for photovoltaic cell

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Limin [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou (China); University of Chinese Academy of Sciences, Beijing (China); Jia, Junhong; Yi, Gewen [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou (China)

    2017-02-15

    An electrode with [KNbO{sub 3}]{sub 0.9}[BaCo{sub 1/2}Nb{sub 1/2}O{sub 3-δ}]{sub 0.1} (KBCNO) perovskite oxide as sensitizer and well-aligned TiO{sub 2} nanorod arrays is prepared via conventional standard solid-state synthesis method, followed by pulsed laser deposition technique for the first time. Enhanced absorption in visible light region is observed for KBCNO rate at TiO{sub 2} NRs photoelectrode, which is mainly because the inserted Co 3d electronic states can hybridize with O 2p states in the gap of KBCNO, reducing the band gap to 1.90 eV. Additionally, the oxygen vacancies existing in KBCNO can not only serve as photoinduced charge traps and adsorption sites but also prevent recombination of photoinduced electron-hole, giving rise to enhanced separation of photogenerated electron-hole pair and leading to an improved performance in solar energy conversion. The KBCNO rate at TiO{sub 2} NRs photoelectrode exhibits an energy conversion efficiency of 0.183% under one sun illumination. This work provide further insight for improving the efficiency of utilization of solar energy by using a new composite perovskite oxides material, which may be promising rational categories of material for solar conversion and storage devices. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Rickets and vitamin D deficiency in Alaska native children.

    Science.gov (United States)

    Singleton, Rosalyn; Lescher, Rachel; Gessner, Bradford D; Benson, Matthew; Bulkow, Lisa; Rosenfeld, John; Thomas, Timothy; Holman, Robert C; Haberling, Dana; Bruce, Michael; Bartholomew, Michael; Tiesinga, James

    2015-07-01

    Rickets and vitamin D deficiency appeared to increase in Alaskan children starting in the 1990s. We evaluated the epidemiology of rickets and vitamin D deficiency in Alaska native (AN) children in 2001-2010. We analyzed 2001-2010 visits with rickets or vitamin D deficiency diagnosis for AN and American Indian children and the general US population aged rickets/vitamin D deficient cases and age- and region-matched controls. In AN children, annual rickets-associated hospitalization rate (2.23/100,000 children/year) was higher than the general US rate (1.23; 95% CI 1.08-1.39). Rickets incidence increased with latitude. Rickets/vitamin D deficiency cases were more likely to have malnutrition (OR 38.1; 95% CI 4.9-294), had similar breast-feeding prevalence, and were less likely to have received vitamin D supplementation (OR 0.23; 95% CI 0.1-0.87) than controls. Our findings highlight the importance of latitude, malnutrition, and lack of vitamin D supplementation as risk factors for rickets.

  11. Oxygen storage capacity and structural properties of Ni-doped LaMnO3 perovskites

    International Nuclear Information System (INIS)

    Ran, Rui; Wu, Xiaodong; Weng, Duan; Fan, Jun

    2013-01-01

    Graphical abstract: Dynamic OSC of (a) fresh and (b) aged LaMn 1−x Ni x O 3 perovskites (0.1 Hz). Aged condition: 1050 °C, 5 h, 7% steam in air. The LaMn 1−x Ni x O 3 perovskites exhibit considerable dynamic OSC in comparison to CeO 2 –ZrO 2 (CZ), even after 1050 °C hydrothermal ageing for 5 h. Highlights: •Ni-doped LaMnO 3 perovskites exhibit very large dynamic OSC and high oxygen storage rate. •Mn 4+ is favourable to the releasable oxygen. •Doping of Ni ions increase the Mn 4+ content and the oxygen vacancies. •Doping of Ni ions reduce the BO 6 distortion in the LaMnO 3 perovskites. -- Abstract: A series of Ni doped LaMnO 3 perovskites were prepared by a sol–gel method as oxygen storage materials. Powder X-ray diffraction (XRD), X-ray adsorption fine structure (XAFS), oxygen storage capacity (OSC) and H 2 -temperature program reduction (TPR) measurements were performed to investigate the OSC of the perovskites as well as the effects of Ni on the structural properties. The results showed that the Ni-doped LaMnO 3 perovskite exhibited very large dynamic OSC and high oxygen release rate, which provided a possibility to serve as an oxygen storage material candidate in three-way catalysts. The available oxygen species below 500 °C primarily originated from the redox reaction between Mn 4+ and Mn 3+ , and the more Mn 4+ were favourable to the releasable oxygen. The doping of appropriate Ni ions promoted the OSC of the LaMnO 3 perovskites by increasing the Mn 4+ content and adjusting the structural defects. On the other hand, the doped Ni ions could make the BO 6 distortion disappearing in the LaMnO 3 perovskites to reduce the lattice oxygen activity

  12. LaMn1-xFe xO3 and LaMn0.1-xFe0.90Mo x O3 perovskites: synthesis, characterization and catalytic activity in H2O2 reactions

    Directory of Open Access Journals (Sweden)

    Fabiano Magalhães

    2008-09-01

    Full Text Available In this work two perovskites were prepared: LaMn1-xFe xO3, and LaMn0.1-x Fe0.90Mo xO3. XRD and Mössbauer spectroscopy suggest the formation of pure phase perovskite with the incorporation of Fe and Mo in the structure. The catalytic activity of these materials was studied in two reactions with H2O2: the decomposition to O2, and the oxidation of the model organic contaminant methylene blue. The perovskite composition strongly affects the catalytic activity, while Fe decreases the H2O2 decomposition Mo strongly improves dye oxidation.

  13. Enhanced Crystalline Phase Purity of CH3NH3PbI3-xClx Film for High-Efficiency Hysteresis-Free Perovskite Solar Cells.

    Science.gov (United States)

    Yang, Yingguo; Feng, Shanglei; Xu, Weidong; Li, Meng; Li, Li; Zhang, Xingmin; Ji, Gengwu; Zhang, Xiaonan; Wang, Zhaokui; Xiong, Yimin; Cao, Liang; Sun, Baoquan; Gao, Xingyu

    2017-07-12

    Despite rapid successful developments toward promising perovskite solar cells (PSCs) efficiency, they often suffer significant hysteresis effects. Using synchrotron-based grazing incidence X-ray diffraction (GIXRD) with different probing depths by varying the incident angle, we found that the perovskite films consist of dual phases with a parent phase dominant in the interior and a child phase with a smaller (110) interplanar space (d (110) ) after rapid thermal annealing (RTA), which is a widely used post treatment to improve the crystallization of solution-processed perovskite films for high-performance planar PSCs. In particular, the child phase composition gradually increases with decreasing depth till it becomes the majority on the surface, which might be one of the key factors related to hysteresis in fabricated PSCs. We further improve the crystalline phase purity of the solution-processed CH 3 NH 3 PbI 3-x Cl x perovskite film (referred as g-perovskite) by using a facile gradient thermal annealing (GTA), which shows a uniformly distributed phase structure in pinhole-free morphology with less undercoordinated Pb and I ions determined by synchrotron-based GIXRD, grazing incidence small-angle X-ray scattering, scanning electron microscopy, and X-ray photoelectron spectroscopy. Regardless of device structures (conventional and inverted types), the planar heterojunction PSCs employing CH 3 NH 3 PbI 3-x Cl x g-perovskite films exhibit negligible hysteresis with a champion power conversion efficiency of 17.04% for TiO 2 -based conventional planar PSCs and 14.83% for poly(3,4-ethylenedioxythiophene:poly(styrenesulfonate) (PEDOT:PSS)-based inverted planar PSCs. Our results indicate that the crystalline phase purity in CH 3 NH 3 PbI 3-x Cl x perovskite film, especially in the surface region, plays a crucial role in determining the hysteresis effect and device performance.

  14. Simplified Perovskite Solar Cell with 4.1% Efficiency Employing Inorganic CsPbBr3 as Light Absorber.

    Science.gov (United States)

    Duan, Jialong; Zhao, Yuanyuan; He, Benlin; Tang, Qunwei

    2018-04-17

    Perovskite solar cells with cost-effectiveness, high power conversion efficiency, and improved stability are promising solutions to the energy crisis and environmental pollution. However, a wide-bandgap inorganic-semiconductor electron-transporting layer such as TiO 2 can harvest ultraviolet light to photodegrade perovskite halides, and the high cost of a state-of-the-art hole-transporting layer is an economic burden for commercialization. Here, the building of a simplified cesium lead bromide (CsPbBr 3 ) perovskite solar cell with fluorine-doped tin oxide (FTO)/CsPbBr 3 /carbon architecture by a multistep solution-processed deposition technology is demonstrated, achieving an efficiency as high as 4.1% and improved stability upon interfacial modification by graphene quantum dots and CsPbBrI 2 quantum dots. This work provides new opportunities of building next-generation solar cells with significantly simplified processes and reduced production costs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Light-emitting diodes based on two-dimensional PA2(CsPbBr3)n-1PbBr4 layered perovskites%基于PA2(CsPbBr3)n-1PbBr4二维层状钙钛矿的电致发光二极管

    Institute of Scientific and Technical Information of China (English)

    孟妍; 牛连斌; 许龙; 林春燕; 熊自阳; 熊祖洪; 陈平

    2018-01-01

    remains a major concern.To circumvent this problem,all-inorganic halide perovskites exhibiting higher thermal and chemical stability,such as cesium lead bromide (CsPbBr3),have been used as alternative emitters in PeLED.Despite the advantages described above,both the brightness and the EQE of CsPbBr3-based PeLED remain limited.One important reason for low efficiency of CsPbBr3-based PeLED is the facile dissociation of excitons in 3D perovskites due to their small exciton binding energy.One promising way to enhance the exciton binding energy is reducing the grain size of perovskites.Herein,we report a solution process to form highly uniform and ultra-fiat perovskite films with nanometre-sized grains that allow us to demonstrate efficient PeLED.By mixing long-chain ammonium halides of CH3CH2CH2NH3Br (PABr) with the 3D CsPbBr3 perovskite precursor solution,the growth of 3D perovskite grains are dramatically impeded and the PA2(CsPbBr3)n-1PbBr4 quantum dots with grain size of ~100 nm were achieved.This is because the long-chain ammonium ions cannot fill the comer of PbBr4 octahedral layers and therefore impedes the 3D perovskite formation.Moreover,the nanometre-sized grains feature reduced dimensionality,starting a transition from 3D to 2D layered (so-called Ruddlesden-Popper phase) perovskite structures.The SEM image show the morphology of PA2(CsPbBr3)n-1PbBr4 layer was dense and uniform,which is very important to suppress the leaking current in the PeLED.We found that PA2(CsPbBr3)n-1PbBr4 film mainly consists of two different 2D structures,namely PA2PbBr4 (n=l) and PA2(CsPbBr3)PbBr4 (n=2),according to the analysis of XRD pattern.Compared to the single UVs absorption peak of CsPbBr3 at ~520 nm,PA2(CsPbBr3)n-1PbBr4 film show multiple absorption peaks,indicating several extonic states are formed upon light excitation.Although several extonic states exist,photoluminescence (PL) with only one peak of 506 nm was observed in PA2(CsPbBr3)n-1PbBr4 film.We suspect that the energy

  16. Room temperature three-photon pumped CH3NH3PbBr3 perovskite microlasers

    Science.gov (United States)

    Gao, Yisheng; Wang, Shuai; Huang, Can; Yi, Ningbo; Wang, Kaiyang; Xiao, Shumin; Song, Qinghai

    2017-03-01

    Hybrid lead halide perovskites have made great strides in next-generation light-harvesting and light emitting devices. Recently, they have also shown great potentials in nonlinear optical materials. Two-photon absorption and two-photon light emission have been thoroughly studied in past two years. However, the three-photon processes are rarely explored, especially for the laser emissions. Here we synthesized high quality CH3NH3PbBr3 perovskite microstructures with solution processed precipitation method and studied their optical properties. When the microstructures are pumped with intense 1240 nm lasers, we have observed clear optical limit effect and the band-to-band photoluminescence at 540 nm. By increasing the pumping density, whispering-gallery-mode based microlasers have been achieved from CH3NH3PbBr3 perovskite microplate and microrod for the first time. This work demonstrates the potentials of hybrid lead halide perovskites in nonlinear photonic devices.

  17. Pressure-Induced Metallization of the Halide Perovskite (CH 3 NH 3 )PbI 3

    Energy Technology Data Exchange (ETDEWEB)

    Jaffe, Adam; Lin, Yu [Photon; Mao, Wendy L. [Photon; Karunadasa, Hemamala I.

    2017-03-10

    We report the metallization of the hybrid perovskite semiconductor (MA)PbI3 (MA = CH3NH3+) with no apparent structural transition. We tracked its bandgap evolution during compression in diamond-anvil cells using absorption spectroscopy and observed strong absorption over both visible and IR wavelengths at pressures above ca. 56 GPa, suggesting the imminent closure of its optical bandgap. The metallic character of (MA)PbI3 above 60 GPa was confirmed using both IR reflectivity and variable-temperature dc conductivity measurements. The impressive semiconductor properties of halide perovskites have recently been exploited in a multitude of optoelectronic applications. Meanwhile, the study of metallic properties in oxide perovskites has revealed diverse electronic phenomena. Importantly, the mild synthetic routes to halide perovskites and the templating effects of the organic cations allow for fine structural control of the inorganic lattice. Pressure-induced closure of the 1.6 eV bandgap in (MA)PbI3 demonstrates the promise of the continued study of halide perovskites under a range of thermodynamic conditions, toward realizing wholly new electronic properties.

  18. Generalized trends in the formation energies of perovskite oxides

    DEFF Research Database (Denmark)

    Zeng, Zhenhua; Calle-Vallejo, Federico; Mogensen, Mogens Bjerg

    2013-01-01

    Generalized trends in the formation energies of several families of perovskite oxides (ABO3) and plausible explanations to their existence are provided in this study through a combination of DFT calculations, solid-state physics analyses and simple physical/chemical descriptors. The studied...... elements at the A site of perovskites comprise rare-earth, alkaline-earth and alkaline metals, whereas 3d and 5d metals were studied at the B site. We also include ReO3-type compounds, which have the same crystal structure of cubic ABO3 perovskites except without A-site elements. From the observations we...... extract the following four conclusions for the perovskites studied in the present paper: for a given cation at the B site, (I) perovskites with cations of identical oxidation state at the A site possess close formation energies; and (II) perovskites with cations of different oxidation states at the A site...

  19. Photostriction of CH3NH3PbBr3 Perovskite Crystals

    KAUST Repository

    Wei, Tzu-Chiao

    2017-07-17

    Organic-inorganic hybrid perovskite materials exhibit a variety of physical properties. Pronounced coupling between phonon, organic cations, and the inorganic framework suggest that these materials exhibit strong light-matter interactions. The photoinduced strain of CH3 NH3 PbBr3 is investigated using high-resolution and contactless in situ Raman spectroscopy. Under illumination, the material exhibits large blue shifts in its Raman spectra that indicate significant structural deformations (i.e., photostriction). From these shifts, the photostrictive coefficient of CH3 NH3 PbBr3 is calculated as 2.08 × 10-8 m2 W-1 at room temperature under visible light illumination. The significant photostriction of CH3 NH3 PbBr3 is attributed to a combination of the photovoltaic effect and translational symmetry loss of the molecular configuration via strong translation-rotation coupling. Unlike CH3 NH3 PbI3 , it is noted that the photostriction of CH3 NH3 PbBr3 is extremely stable, demonstrating no signs of optical decay for at least 30 d. These results suggest the potential of CH3 NH3 PbBr3 for applications in next-generation optical micro-electromechanical devices.

  20. Vitamin D Deficiency in Patients with Systemic Lupus Erythematosus

    Directory of Open Access Journals (Sweden)

    Suzan M. Attar

    2013-01-01

    Full Text Available Objectives: Hypovitaminosis D is common in the general population. Many studies that have been conducted to show the association between vitamin D deficiency and systemic lupus erythematosus (SLE reveal that deficiencies in vitamin D are common in this group of patients. Our aim was to study the relationship between 25(OHD and disease activity in patients with SLE.Methods: Retrospective cohort study of patients with SLE who were followed up at King Abdulaziz University Hospital, Jeddah, from January 2007 to November 2010. Demographic and clinical data were recorded and the 25(OHD levels of the patients were measured. Chi square tests, Student’s t-test, ANOVA and Pearson tests were used for data analysis. ANOVA test was followed by Bonferroni correction. A p-value <0.05 was considered significant.Results: Ninety-five patients with SLE were enrolled in the study. The levels of 25(OHD were significantly lower in patients with active SLE (n=41; 43% than in those with inactive disease (n=54; 57%; p=0.04. The mean (SD levels were 22.3 (14 nmol/L for patients with active disease against 25.0 (14 nmol/L for patients with inactive SLE. No correlation was detected between 25(OH D levels and disease activity score evaluated by SLEDAI-2K. By Pearson correlation, a significant negative correlation existed between 25(OH D and anti ds-DNA (r=-0.38; p<0.001; a positive correlation existed between 25(OHD levels and C4 (r=0.25; p=0.25. By chi square testing, azathioprine treatment (OR=3.5, low C4 (OR= 2.23, low C3 (OR=1.92, and active disease (OR=1.6 were associated with 25(OHD deficiency in SLE patients.Conclusion: Vitamin D deficiency is frequent in patients with SLE. Patients with SLE have a higher risk of developing 25(OHD deficiency in the presence of low serum C3 and C4 levels, and high anti-dsDNA levels.

  1. Tunable White-Light Emission in Single-Cation-Templated Three-Layered 2D Perovskites (CH 3 CH 2 NH 3 ) 4 Pb 3 Br 10–x Cl x

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Lingling; Wu, Yilei; Stoumpos, Constantinos C.; Traore, Boubacar [Institut; Katan, Claudine [Institut; Even, Jacky [Fonctions; Wasielewski, Michael R.; Kanatzidis, Mercouri G.

    2017-08-16

    Two-dimensional (2D) hybrid halide perovskites come as a family (B)2(A)n-1PbnX3n+1 (B and A= cations; X= halide). These perovskites are promising semiconductors for solar cells and optoelectronic applications. Among the fascinating properties of these materials is white-light emission, which has been mostly observed in single-layered 2D lead bromide or chloride systems (n = 1), where the broad emission comes from the transient photoexcited states generated by self-trapped excitons (STEs) from structural distortion. Here we report a multilayered 2D perovskite (n = 3) exhibiting a tunable white-light emission. Ethylammonium (EA+) can stabilize the 2D perovskite structure in EA4Pb3Br10–xClx (x = 0, 2, 4, 6, 8, 9.5, and 10) with EA+ being both the A and B cations in this system. Because of the larger size of EA, these materials show a high distortion level in their inorganic structures, with EA4Pb3Cl10 having a much larger distortion than that of EA4Pb3Br10, which results in broadband white-light emission of EA4Pb3Cl10 in contrast to narrow blue emission of EA4Pb3Br10. The average lifetime of the series decreases gradually from the Cl end to the Br end, indicating that the larger distortion also prolongs the lifetime (more STE states). The band gap of EA4Pb3Br10–xClx ranges from 3.45 eV (x = 10) to 2.75 eV (x = 0), following Vegard’s law. First-principles density functional theory calculations (DFT) show that both EA4Pb3Cl10 and EA4Pb3Br10 are direct band gap semiconductors. The color rendering index (CRI) of the series improves from 66 (EA4Pb3Cl10) to 83 (EA4Pb3Br0.5Cl9.5), displaying high tunability and versatility of the

  2. Ultralow Self-Doping in 2D Hybrid Perovskite Single Crystals

    KAUST Repository

    Peng, Wei; Yin, Jun; Ho, Kang-Ting; Ouellette, Olivier; de Bastiani, Michele; Banavoth, Murali; El Tall, Omar; Shen, Chao; Miao, Xiaohe; Pan, Jun; Alarousu, Erkki; He, Jr-Hau; Ooi, Boon S.; Mohammed, Omar F.; Sargent, Edward H.; Bakr, Osman

    2017-01-01

    -processed semiconductors, including hybrid perovskites, which are usually high in defects due to rapid crystallization. Here, we uncover extremely low self-doping concentrations in single crystals of (C6H5C2H4NH3)2PbI4・(CH3NH3PbI3)n-1 (n=1, 2, and 3)—over three orders

  3. Chemically tailoring the dopant emission in manganese-doped CsPbCl{sub 3} perovskite nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Das Adhikari, Samrat; Dutta, Sumit K.; Dutta, Anirban; Guria, Amit K.; Pradhan, Narayan [Department of Materials Science, Indian Association for the Cultivation of Science, Kolkata (India)

    2017-07-17

    Doping in perovskite nanocrystals adopts different mechanistic approach in comparison to widely established doping in chalcogenide quantum dots. The fast formation of perovskites makes the dopant insertions more competitive and challenging. Introducing alkylamine hydrochloride (RNH{sub 3}Cl) as a promoting reagent, precise controlled doping of Mn{sup II} in CsPbCl{sub 3} perovskite nanocrystals is reported. Simply, by changing the amount of RNH{sub 3}Cl, the Mn incorporation and subsequent tuning in the excitonic as well as Mn d-d emission intensities are tailored. Investigations suggested that RNH{sub 3}Cl acted as the chlorinating source, controlled the size, and also helps in increasing the number of particles. This provided more opportunity for Mn ions to take part in reaction and occupied the appropriate lattice positions. Carrying out several reactions with varying reaction parameters, the doping conditions are optimized and the role of the promoting reagent for both doped and undoped systems are compared. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Raman spectra of MgSiO3 . 10% Al2O3-perovskite at various pressures and temperatures

    International Nuclear Information System (INIS)

    Liu Lingun; Irifune, T.

    1995-01-01

    Variations of Raman spectra of MgSiO 3 . 10% Al 2 O 3 -perovskite were investigated up to about 270 kbar at room temperature and in the range 108-425 K at atmospheric pressure. Like MgSiO 3 -perovskite, the Raman frequencies of MgSiO 3 . 10% Al 2 O 3 -perovskite increase nonlinearly with increasing pressure and decrease linearly with increasing temperature within the experimental uncertainties and the range investigated. A comparison of these data with those of MgSiO 3 -perovskite suggests that MgSiO 3 . 10% Al 2 O 3 -perovskite is slightly more compressible than MgSiO 3 -perovskite, and that the volume thermal expansion for MgSiO 3 . 10% Al 2 O 3 -perovskite is also slightly greater than that for MgSiO 3 -perovskite. (orig.)

  5. Performance Improvement of CH3NH3PbI3 Perovskite Solar Cell by CH3SH Doping

    Directory of Open Access Journals (Sweden)

    Hong Li

    2016-03-01

    Full Text Available Organometal halide perovskites have recently emerged as an appealing candidate in photovoltaic devices due to their excellent properties. Therefore, intense efforts have been devoted to find the ideal organics for perovskite solar cells. In response, we investigate the doping effect of CH3SH organic on the structure and related performance of a CH3NH3PbI3 perovskite solar cell, via in situ synchrotron- based grazing incidence X-ray diffraction (GIXRD, together with scanning electron microscopy (SEM. In situ GIXRD investigations clearly illustrated the transformation and modification of the perovskite structure induced by the organic dopant, which subsequently led to the enhance‐ ment of the power conversion efficiency of fabricated solar cells. Notably, nanoporous morphology and nanocrystal‐ line structures were discovered in the perovskite film by SEM; they were also confirmed by the increase in broad‐ ening peaks/features in the GIXRD measurements. Overall, our study may ultimately result in an attractive strategy for the fabrication of high performance perovskite solar cells.

  6. Annealing Effect on (FAPbI31−x(MAPbBr3x Perovskite Films in Inverted-Type Perovskite Solar Cells

    Directory of Open Access Journals (Sweden)

    Lung-Chien Chen

    2016-09-01

    Full Text Available This study determines the effects of annealing treatment on the structure and the optical and electronic behaviors of the mixed (FAPbI31−x(MAPbBr3x perovskite system. The experimental results reveal that (FAPbI31−x(MAPbBr3x (x ~ 0.2 is an effective light-absorbing material for use in inverted planar perovskite solar cells owing to its large absorbance and tunable band gap. Therefore, good band-matching between the (FAPbI31−x(MAPbBr3x and C60 in photovoltaic devices can be controlled by annealing at various temperatures. Accordingly, an inverted mixed perovskite solar cell with a record efficiency of 12.0% under AM1.5G irradiation is realized.

  7. O3 perovskite ceramic

    Indian Academy of Sciences (India)

    The prepared sample remains as double phases with the perovskite struc- ture. The structure ... Ferroelectric oxides with perovskite structure are the subject of many investigations. ... in optical devices and heterojunction solar cells. 1765 ...

  8. Short alleles revealed by PCR demonstrate no heterozygote deficiency at minisatellite loci D1S7, D7S21, and D12S11

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, S.; Castro, A.; Fernandez-Fernandez, I.; Pancorbo, M.M. de [Universidad del Pais Vasco, Vizcaya (Spain)

    1997-02-01

    Short VNTR alleles that go undetected after conventional Southern blot hybridization may constitute an alternative explanation for the heterozygosity deficiency observed at some minisatellite loci. To examine this hypothesis, we have employed a screening procedure based on PCR amplification of those individuals classified as homozygotes in our databases for the loci D1S7, D7S21, and D12S11. The results obtained indicate that the frequency of these short alleles is related to the heterozygosity deficiency observed. For the most polymorphic locus, D1S7, {approximately}60% of those individuals previously classified as homozygotes were in fact heterozygotes for a short allele. After the inclusion of these new alleles, the agreement between observed and expected heterozygosity, along with other statistical tests employed, provide additional evidence for lack of population substructuring. Comparisons of allele frequency distributions reveal greater differences between racial groups than between closely related populations. 45 refs., 3 figs., 6 tabs.

  9. Vitamin D deficiency in mice impairs colonic antibacterial activity and predisposes to colitis.

    Science.gov (United States)

    Lagishetty, Venu; Misharin, Alexander V; Liu, Nancy Q; Lisse, Thomas S; Chun, Rene F; Ouyang, Yi; McLachlan, Sandra M; Adams, John S; Hewison, Martin

    2010-06-01

    Vitamin D insufficiency is a global health issue. Although classically associated with rickets, low vitamin D levels have also been linked to aberrant immune function and associated health problems such as inflammatory bowel disease (IBD). To test the hypothesis that impaired vitamin D status predisposes to IBD, 8-wk-old C57BL/6 mice were raised from weaning on vitamin D-deficient or vitamin D-sufficient diets and then treated with dextran sodium sulphate (DSS) to induce colitis. Vitamin D-deficient mice showed decreased serum levels of precursor 25-hydroxyvitamin D(3) (2.5 +/- 0.1 vs. 24.4 +/- 1.8 ng/ml) and active 1,25-dihydroxyvitamin D(3) (28.8 +/- 3.1 vs. 45.6 +/- 4.2 pg/ml), greater DSS-induced weight loss (9 vs. 5%), increased colitis (4.71 +/- 0.85 vs. 1.57 +/- 0.18), and splenomegaly relative to mice on vitamin D-sufficient chow. DNA array analysis of colon tissue (n = 4 mice) identified 27 genes consistently (P < 0.05) up-regulated or down-regulated more than 2-fold in vitamin D-deficient vs. vitamin D-sufficient mice, in the absence of DSS-induced colitis. This included angiogenin-4, an antimicrobial protein involved in host containment of enteric bacteria. Immunohistochemistry confirmed that colonic angiogenin-4 protein was significantly decreased in vitamin D-deficient mice even in the absence of colitis. Moreover, the same animals showed elevated levels (50-fold) of bacteria in colonic tissue. These data show for the first time that simple vitamin D deficiency predisposes mice to colitis via dysregulated colonic antimicrobial activity and impaired homeostasis of enteric bacteria. This may be a pivotal mechanism linking vitamin D status with IBD in humans.

  10. High-pressure crystal growth and electromagnetic properties of 5d double-perovskite Ca3OsO6

    Science.gov (United States)

    Feng, Hai Luke; Shi, Youguo; Guo, Yanfeng; Li, Jun; Sato, Akira; Sun, Ying; Wang, Xia; Yu, Shan; Sathish, Clastin I.; Yamaura, Kazunari

    2013-05-01

    Single crystals of the osmium-containing compound Ca3OsO6 have been successfully grown under high-pressure conditions, for the first time. The crystal structure of Ca3OsO6 were characterized as an ordered double-perovskite structure of space group P21/n with the Ca and Os atoms being fully ordered at the perovskite B-site. The electromagnetic analysis shows that the crystal exhibits a semiconductor-like behavior below 300 K and undergoes an antiferromagnetic transition at 50 K.

  11. Efficacy and safety of vitamin D3 B.O.N intramuscular injection in Korean adults with vitamin D deficiency

    Directory of Open Access Journals (Sweden)

    Han Seok Choi

    2016-12-01

    Conclusion: Intramuscular injection of vitamin D3 200,000 IU was superior to placebo in terms of its impact on serum 25(OHD concentrations, and is considered to be safe and effective in Korean adults with vitamin D deficiency.

  12. Two-Dimensional Halide Perovskites for Emerging New- Generation Photodetectors

    DEFF Research Database (Denmark)

    Tang, Yingying; Cao, Xianyi; Chi, Qijin

    2018-01-01

    Compared to their conventional three-dimensional (3D) counterparts, two-dimensional (2D) halide perovskites have attracted more interests recently in a variety of areas related to optoelectronics because of their unique structural characteristics and enhanced performances. In general, there are two...... distinct types of 2D halide perovskites. One represents those perovskites with an intrinsic layered crystal structure (i.e. MX6 layers, M = metal and X = Cl, Br, I), the other defines the perovskites with a 2D nanostructured morphology such as nanoplatelets and nanosheets. Recent studies have shown that 2D...... halide perovskites hold promising potential for the development of new-generation photodetectors, mainly arising from their highly efficient photoluminescence and absorbance, color tunability in the visible-light range and relatively high stability. In this chapter, we present the summary and highlights...

  13. First principles investigation of half-metallicity and spin gapless semiconductor in CH3NH3Cr x Pb1- x I3 mixed perovskites

    Science.gov (United States)

    Huang, H. M.; Zhu, Z. W.; Zhang, C. K.; He, Z. D.; Luo, S. J.

    2018-04-01

    The structural, electronic and magnetic properties of organic-inorganic hybrid mixed perovskites CH3NH3Cr x Pb1- x I3 ( x = 0.25, 0.50, 0.75, 1.00) in cubic, tetragonal and orthorhombic phases have been investigated by first-principles calculation. The results indicate that the tetragonal CH3NH3Cr0.75Pb0.25I3 is a spin gapless semiconductor with Curie temperature of 663 K estimated using mean field approximation. All other CH3NH3Cr x Pb1- x I3 mixed perovskites are half-metallic ferromagnets together with 100% spin polarization, and their total magnetic moment are 4.00, 8.00, 12.00 and 16.00 µB per unit cell for x = 0.25, 0.50, 0.75 and 1.00, respectively. The effect of , and orientation of organic cation CH3NH3 + on the electronic properties of CH3NH3Cr0.50Pb0.50I3 was investigated. The results show that the CH3NH3 + in different orientations have a slight effect on the lattice constants, the energy gap in minority-spin states, half-metallic gap, local magnetic moment, and Curie temperature.

  14. Formability of ABX3 (X=F,Cl,Br,I) halide perovskites

    International Nuclear Information System (INIS)

    Li Chonghea; Lu Xionggang; Ding Weizhong; Feng Liming; Gao Yonghui; Guo Ziming

    2008-01-01

    In this study a total of 186 complex halide systems were collected; the formabilities of ABX 3 (X = F, Cl, Br and I) halide perovskites were investigated using the empirical structure map, which was constructed by Goldschmidt's tolerance factor and the octahedral factor. A model for halide perovskite formability was built up. In this model obtained, for all 186 complex halides systems, only one system (CsF-MnF 2 ) without perovskite structure and six systems (RbF-PbF 2 , CsF- BeF 2 , KCl-FeCl 2 , TlI-MnI 2 , RbI-SnI 2 , TlI-PbI 2 ) with perovskite structure were wrongly classified, so its predicting accuracy reaches 96%. It is also indicated that both the tolerance factor and the octahedral factor are a necessary but not sufficient condition for ABX 3 halide perovskite formability, and a lowest limit of the octahedral factor exists for halide perovskite formation. This result is consistent with our previous report for ABO 3 oxide perovskite, and may be helpful to design novel halide materials with the perovskite structure. (orig.)

  15. Study of transport properties of bodies with a perovskite structure: application to the MgSiO3 perovskite

    International Nuclear Information System (INIS)

    Kapusta, Benedicte

    1990-01-01

    After some recalls on transport in ionic solids (Nernst-Einstein relationship, variation of ionic conductivity, hybrid conduction, fast ionic conduction), this research thesis presents the physical properties of perovskites and more particularly the structure and stability of the MgSiO 3 perovskite: structure and elastic properties, electric conductivity and transport properties in compounds with a perovskite structure. Then, the author reports the experimental study of the KZnF 3 perovskite (a structural analogous of MgSiO 3 ): measurements of electric conductivity under pressure, measurements under atmospheric pressure, result discussion. The next part addresses the numerical simulation of MgSiO 3 : simulation techniques (generalities on molecular dynamics, model description), investigation of structural, elastic and thermodynamic properties, diffusion properties in quadratic phase [fr

  16. Synthesis and characterization of a-site doped LaTiO3 nano perovskites

    International Nuclear Information System (INIS)

    Bradha, M.; Ashok, Anuradha

    2013-01-01

    Nano-sized lanthanum titanate perovskites (La (1-x) A x TiO 3 ) (A= Ba, Sr, Ca) were prepared by sol-gel method and calcined at 800℃. The synthesised perovskites were characterized by Thermogravimetry/ Differential thermal analysis (TGA/DTA), X-ray diffraction (XRD) and High Resolution Transmission Electron Microscopy (HRTEM) etc. LaTiO 3 is a perovskite having prominent interest for a variety of applications such as dielectric, insulators, charge-transport properties etc. It is a defect perovskite, with transport properties varying from insulating to metallic based on oxygen stoichiometry. In a quest to observe the effect of the nano size on its properties, lanthanum titanate (LaTiO 3 ) nano perovskites with different dopants on the A-site were prepared by using sol-gel method. In the present work we discuss the synthesis and structural analysis of (La 0.8 A 0.2 TiO 3 ). Phase purity and structural analysis of the calcined samples were performed by powder X-ray diffraction (XRD, with CuKα radiation). In addition to this, morphology and crystal structure was examined by Transmission Electron Microscopy (TEM) using a JEOL JEM 2100 HRTEM. HRTEM studies indicate that the nano perovskites are of size around 20 nm. Ring pattern in SAED also confirms that the perovskite is polycrystalline/nanocrystalline. More detailed study on high resolution images and crystal structure shed light on the reason for the properties exhibited by this perovskites

  17. Zero-Dimensional Cs4PbBr6 Perovskite Nanocrystals

    KAUST Repository

    Zhang, Yuhai

    2017-02-09

    Perovskite nanocrystals (NCs) have become leading candidates for solution-processed optoelectronics applications. While substantial work has been published on 3-D perovskite phases, the NC form of the zero-dimensional (0-D) phase of this promising class of materials remains elusive. Here we report the synthesis of a new class of colloidal semiconductor NCs based on Cs4PbBr6, the 0-D perovskite, enabled through the design of a novel low-temperature reverse microemulsion method with 85% reaction yield. These 0-D perovskite NCs exhibit high photoluminescence quantum yield (PLQY) in the colloidal form (PLQY: 65%), and, more importantly, in the form of thin film (PLQY: 54%). Notably, the latter is among the highest values reported so far for perovskite NCs in the solid form. Our work brings the 0-D phase of perovskite into the realm of colloidal NCs with appealingly high PLQY in the film form, which paves the way for their practical application in real devices.

  18. Efficient perovskite light-emitting diodes featuring nanometre-sized crystallites

    Science.gov (United States)

    Xiao, Zhengguo; Kerner, Ross A.; Zhao, Lianfeng; Tran, Nhu L.; Lee, Kyung Min; Koh, Tae-Wook; Scholes, Gregory D.; Rand, Barry P.

    2017-01-01

    Organic-inorganic hybrid perovskite materials are emerging as highly attractive semiconductors for use in optoelectronics. In addition to their use in photovoltaics, perovskites are promising for realizing light-emitting diodes (LEDs) due to their high colour purity, low non-radiative recombination rates and tunable bandgap. Here, we report highly efficient perovskite LEDs enabled through the formation of self-assembled, nanometre-sized crystallites. Large-group ammonium halides added to the perovskite precursor solution act as a surfactant that dramatically constrains the growth of 3D perovskite grains during film forming, producing crystallites with dimensions as small as 10 nm and film roughness of less than 1 nm. Coating these nanometre-sized perovskite grains with longer-chain organic cations yields highly efficient emitters, resulting in LEDs that operate with external quantum efficiencies of 10.4% for the methylammonium lead iodide system and 9.3% for the methylammonium lead bromide system, with significantly improved shelf and operational stability.

  19. Ba2+ Doped CH3NH3PbI3 to Tune the Energy State and Improve the Performance of Perovskite Solar Cells

    International Nuclear Information System (INIS)

    Zhang, Hanbing; Shang, Ming-hui; Zheng, Xiaoying; Zeng, Zhaobing; Chen, Renjie; Zhang, Ying; Zhang, Jing; Zhu, Yuejin

    2017-01-01

    Highlights: •Ba doping enlarges the energy band gap of MAPb 1-x Ba x I 3 . •Voc and Jsc are enhanced in perovskite solar cells. •DFT calculation proves the experiment results. -- Abstract: Elements substitution and doping in perovskite CH 3 NH 3 PbI 3 exhibit versatile tunability of energy band structure and opto-electric properties. Ba 2+ is chosen to substitute Pb 2+ for its similar valence state and ionic radius with Pb 2+ . Ba 2+ doping in perovskite (mol% <5) slightly enlarges the optic energy gap by conduction band minimum(CBM) upshifting to vacuum energy level, which is due to the smaller electronegativity of Ba than Pb. The enlarged band gap is also verified by density function theory calculations. In n-i-p structure perovskite solar cells (PSCs), because of the higher CBM of doped perovskite, the Fermi energy difference between n and p side is enlarged and the electron injection from the perovskite to TiO 2 is improved. Thus, both the photovoltage and photocurrent are improved by small amount Ba 2+ doping, resulting optimized 17.4% efficiency under AM1.5. This work reveals the relationship between the doping element property and the energy band structure of the perovskite, and highlights the doping method to improve the performance of PSCs.

  20. Refurbished dry methane on catalysts Ni / BaTiO 1x In x o 3d

    International Nuclear Information System (INIS)

    Garcia, Veronica; Caldes, Maria T; Joubert Olivier

    2008-01-01

    The effect of the support on the catalytic performance of Ni catalysts in carbon dioxide reforming of methane was studied using perovskite based supports BaTi 1x In x O 3d, known by their ionic and electronic conductivity properties. The results of the investigation showed that there is a close relationship between the catalytic activity and the reducibility of the support.

  1. Association between vitamin D deficiency and heart failure risk in the elderly.

    Science.gov (United States)

    Porto, Catarina Magalhães; Silva, Vanessa De Lima; da Luz, João Soares Brito; Filho, Brivaldo Markman; da Silveira, Vera Magalhães

    2018-02-01

    The aim of this study was to evaluate the association between vitamin D deficiency and risk of heart failure in elderly patients of cardiology outpatient clinics. A cross-sectional study with an analytical approach was employed. Clinical data were collected from the elderly from August 2015 to February 2016. The dependent variable was the risk of heart failure; the independent variable was vitamin D deficiency; and intervening factors were age, gender, education, ethnicity, hypertension, diabetes mellitus, hypothyroidism, renal failure, dementia, stroke, dyslipidaemia, depression, smoking, alcoholism, obesity, andropause, and cardiac arrhythmia. To analyse the association between vitamin D deficiency and risk of heart failure, we used the bivariate logistic analysis, followed by analysis through the multivariate logistic regression model. Of the 137 elderly, the study found the following: women (75.9%); overweight (48.2%); obese (30.6%); increase in the index waist/hip (88.3%); dyslipidaemia (94.2%) and hypertension (91.2%); coronary artery disease (35.0%); and 27.7% with cardiac arrhythmia or left ventricular hypertrophy. Sixty-five per cent of the elderly were deficient in vitamin D. The risk of heart failure was significantly associated with vitamin D deficiency [odds ratio (OR): 12.19; 95% confidence interval (CI) = 4.23-35.16; P = 0.000], male gender (OR: 15.32; 95% CI = 3.39-69.20, P = 0.000), obesity (OR: 4.17; 95% CI = 1.36-12.81; P = 0.012), and cardiac arrhythmia (OR: 3.69; 95% CI = 1.23-11.11; P = 0.020). There was a high prevalence of vitamin D deficiency in the elderly, and the evidence shows a strong association between vitamin D deficiency and increased risk of heart failure in this population. © 2017 The Authors. ESC Heart Failure published by John Wiley & Sons Ltd on behalf of the European Society of Cardiology.

  2. Coherent intergrowth of simple cubic and quintuple tetragonal perovskites in the system Nd_2_−_εBa_3_+_ε(Fe_,Co)_5O_1_5_−_δ

    International Nuclear Information System (INIS)

    Kundu, Asish K.; Yu Mychinko, Mikhail; Caignaert, Vincent; Lebedev, Oleg I.; Volkova, Nadezhda E.; Deryabina, Ksenia M.; Cherepanov, Vladimir A.; Raveau, Bernard

    2015-01-01

    Investigation of the Nd_2_−_εBa_3_+_ε(Fe,Co)_5O_1_5_−_δ system, combining X-ray diffraction and electron microscopy, has allowed a tetragonal quintuple ordered perovskite “a_p×a_p×5a_p” phasoid inter-grown within a single cubic perovskite matrix to be evidenced for ε=0. This nanoscale chemically twinned perovskite is compared with other members, Ln=Sm, Eu, Pr. The unusual long range ordering of the layers develops strains due to size mismatch between Ba"2"+ and Ln"3"+ cations. Importantly, two factors allow the strains to be decreased: (i) special intergrowths of double (LnBaFe_2O_6_−_δ) and triple (LnBa_2Fe_3O_9_−_δ) perovskite ribbons/layers oriented at 90°, (ii) nanoscale chemical twinning. The spin locking effect of the nano-domain boundaries upon the magnetic properties of these perovskites is discussed. - Graphical abstract: Nd_2Ba_3Fe_5O_1_4_._5_4 is a tetragonal quintuple perovskite phasoid embedded in a simple cubic perovskite matrix, which shows collinear antiferromagnetic behavior.

  3. Effect of Different CH3NH3PbI3 Morphologies on Photovoltaic Properties of Perovskite Solar Cells

    Science.gov (United States)

    Chen, Lung-Chien; Lee, Kuan-Lin; Wu, Wen-Ti; Hsu, Chien-Feng; Tseng, Zong-Liang; Sun, Xiao Hong; Kao, Yu-Ting

    2018-05-01

    In this study, the perovskite layers were prepared by two-step wet process with different CH3NH3I (MAI) concentrations. The cell structure was glass/FTO/TiO2-mesoporous/CH3NH3PbI3 (MAPbI3)/spiro-OMeTAD/Ag. The MAPbI3 perovskite films were prepared using high and low MAI concentrations in a two-step process. The perovskite films were optimized at different spin coating speed and different annealing temperatures to enhance the power conversion efficiency (PCE) of perovskite solar cells. The PCE of the resulting device based on the different perovskite morphologies was discussed. The PCE of the best cell was up to 17.42%, open circuit voltage of 0.97 V, short current density of 24.06 mA/cm2, and fill factor of 0.747.

  4. Association between vitamin D deficiency and anemia in inflammatory bowel disease patients with ileostomy

    Directory of Open Access Journals (Sweden)

    Andre Fialho

    2015-07-01

    Full Text Available Background: Vitamin D deficiency is commonly seen in patients with inflammatory bowel disease (IBD. Vitamin D deficiency in IBD patients with ileostomy has not been systemically studied. The aim of the study was to assess the frequency and risk factors associated with low 25(OH D3 levels in those patients. Methods: 112 eligible IBD patients with ileostomy were studied. Demographic, clinical, and endoscopic variables were analyzed. Vitamin D levels before and after ileostomy were compared when available. Levels of serum 25(OHD3 <20 ng/mL were classed as being deficient. Results: 112 eligible ileostomy patients were included. The mean vitamin D level was 21.47 ± 1.08 ng/dl. Low levels of vitamin D (<30 ng/dl were present in 92 patients (82%. Vitamin D deficiency (<20 ng/dL was seen in 55 patients (49%. There was no difference between patients with or without vitamin D deficiency regarding demographic variables, medication use and duration of ileostomy. Neo-ileal inflammation on endoscopy was not associated with vitamin D deficiency (p = 0.155. Lower levels of phosphorus (p = 0.020 or hemoglobin (p = 0.019 and shorter duration of IBD (p = 0.047 were found in patients with vitamin D deficiency. In multivariate analysis, lower levels of phosphorus (odds ratio [OR]: 1.83, 95% confidence interval [CI]: 1.16–2.89, p = 0.009 and hemoglobin (OR: 1.32, 95% CI: 1.08–1.60, p = 0.006 remained significantly associated with vitamin D deficiency. Conclusion: Vitamin D deficiency is common in IBD patients with ileostomy and is associated with low hemoglobin levels. Further studies are needed to evaluate vitamin D supplementation as a possible adjuvant in the treatment of anemia of chronic disease in IBD patients. Resumo: Introdução: A deficiência de vitamina D em pacientes com doença inflamatória intestinal submetidos a ileostomia não foi estudada sistematicamente. O objetivo desse estudo foi avaliar a frequência e os fatores de

  5. Phase formation and UV luminescence of Gd{sup 3+} doped perovskite-type YScO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, Yuhei; Ueda, Kazushige, E-mail: kueda@che.kyutech.ac.jp

    2016-10-15

    Synthesis of pure and Gd{sup 3+}doped perovskite-type YScO{sub 3} was attempted by a polymerized complex (PC) method and solid state reaction (SSR) method. Crystalline phases and UV luminescence of samples were examined with varying heating temperatures. The perovskite-type single phase was not simply formed in the SSR method, as reported in some literatures, and two cubic C-type phases of starting oxide materials remained forming slightly mixed solid solutions. UV luminescence of Gd{sup 3+} doped samples increased with an increase in heating temperatures and volume of the perovskite-type phase. In contrast, a non-crystalline precursor was crystallized to a single C-type phase at 800 °C in the PC method forming a completely mixed solid solution. Then, the phase of perovskite-type YScO{sub 3} formed at 1200 °C and its single phase was obtained at 1400 °C. It was revealed that high homogeneousness of cations was essential to generate the single perovskite-phase of YScO{sub 3}. Because Gd{sup 3+} ions were also dissolved into the single C-type phase in Gd{sup 3+} doped samples, intense UV luminescence was observed above 800 °C in both C-type phase and perovskite-type phase. - Graphical abstract: A pure perovskite-type YScO{sub 3} phase was successfully synthesized by a polymerized complex (PC) method. The perovskite-type YScO{sub 3} was generated through a solid solution of C-type (Y{sub 0.5}Sc{sub 0.5}){sub 2}O{sub 3} with drastic change of morphology. The PC method enabled a preparation of the single phase of the perovskite-type YScO{sub 3} at lower temperature and in shorter heating time. Gd{sup 3+} doped perovskite-type YScO{sub 3} was found to show a strong sharp UV emission at 314 nm. - Highlights: • Pure YScO{sub 3} phase was successfully synthesized by polymerized complex (PC) method. • Pure perovskite-type YScO{sub 3} phase was generated from pure C-type (Y{sub 0.5}Sc{sub 0.5}){sub 2}O{sub 3} one. • YScO{sub 3} was obtained at lower temperature and

  6. On the physiological role of 1,24,25-trihydroxyvitamin D/sub 3/

    Energy Technology Data Exchange (ETDEWEB)

    Castillo, L. (Univ. of Wisconsin, Madison); Tanaka, Y.; DeLuca, H.F.; Ikekawa, N.

    1978-01-01

    The extent, onset and duration of the biological activity of 1,24(R),25-trihydroxyvitamin D/sub 3/, 1,24(S),25-trihydroxyvitamin D/sub 3/ has been compared with that of 1,25-dihydroxyvitamin D/sub 3/ in the elevation of serum phosphorus, healing of rickets, stimulation of intestinal calcium transport, mobilization of calcium from bone in vitamin D-deficient rats and induction 25-hydroxyvitamin D/sub 3/-24-hydroxylase in chickens. The 1,24,25-trihydroxyvitamin D/sub 3/ S and R isomers are approximately equal in activity but both are less active than 1,25-dihydroxyvitamin D/sub 3/. In some systems their duration of activity is also less than that of 1,25-dihydroxyvitamin D/sub 3/. The time course of response to the 3 forms of vitamin D is approximately equal. These results strongly suggest that 1,24(R),25-trihydroxyvitamin D/sub 3/ is not a further activation product of 1,25-dihydroxyvitamin D/sub 3/, but is likely a product leading to inactivation.

  7. Transparent and flexible photodetectors based on CH3NH3PbI3 perovskite nanoparticles

    Science.gov (United States)

    Jeon, Young Pyo; Woo, Sung Jun; Kim, Tae Whan

    2018-03-01

    Transparent and flexible photodetectors (PDs) based on CH3NH3PbI3 perovskite nanoparticles (NPs) were fabricated by using co-evaporation of methyl ammonium iodide and lead iodide. X-ray diffraction patterns and high-resolution transmission electron microscopy images demonstrated the formation of perovskite NPs. The optical transmittance of the perovskite NPs/glass was above 80% over the entire range of visible wavelengths, indicative of high transparency. The PDs based on CH3NH3PbI3 perovskite NPs were sensitive to a broad range of visible light from 450 to 650 nm. The currents in the PDs under exposure to red, green, and blue light-emitting diodes were enhanced to 5, 10, and 20 times that of the PD in the dark, respectively. The rise and the decay times of the PDs were 50 and 120 μs. The current in the perovskite NP PD on a polyethylene terephthalate substrate was enhanced by approximately 69% when the NP PD was exposed to a blue LED emitting at a wavelength of 459 nm. Despite multiple bending, the transparent and flexible PDs based on methyl ammonium iodide and lead iodide NPs showed reproducibility and high stability in performance.

  8. Growth of MAPbBr3 perovskite crystals and its interfacial properties with Al and Ag contacts for perovskite solar cells

    Science.gov (United States)

    Najeeb, Mansoor Ani; Ahmad, Zubair; Shakoor, R. A.; Alashraf, Abdulla; Bhadra, Jolly; Al-Thani, N. J.; Al-Muhtaseb, Shaheen A.; Mohamed, A. M. A.

    2017-11-01

    In this work, the MAPbBr3 perovskite crystals were grown and the interfacial properties of the poly-crystalline MAPbBr3 with Aluminum (Al) and Silver (Ag) contacts has been investigated. MAPbBr3 crystals are turned into the poly-crystalline pellets (PCP) using compaction technique and the Al/PCP, Al/interface layer/PCP, Ag/PCP, and Ag/interface layer/PCP contacts were investigated. Scanning Electron Microscopic (SEM), Energy-dispersive X-ray spectroscopy (EDX) and current-voltage (I-V) characteristic technique were used to have an insight of the degradation mechanism happening at the Metal/perovskite interface. The Ag/PCP contact appears to be stable, whereas Al is found to be highly reactive with the MAPbBr3 perovskite crystals due to the infiltration setback of Al in to the perovskite crystals. The interface layer showed a slight effect on the penetration of Al in to the perovskite crystals however it does not seem to be an appropriate solution. It is noteworthy that the stability of the underlying metal/perovskite contact is very crucial towards the perovskite solar cells with extended device lifetime.

  9. Chlorine Incorporation in the CH3NH3PbI3 Perovskite: Small Concentration, Big Effect.

    Science.gov (United States)

    Quarti, Claudio; Mosconi, Edoardo; Umari, Paolo; De Angelis, Filippo

    2017-01-03

    The role of chlorine doping in CH 3 NH 3 PbI 3 represents an important open issue in the use of hybrid perovskites for photovoltaic applications. In particular, even if a positive role of chlorine doping on perovskite film formation and on material morphology has been demonstrated, an inherent positive effect on the electronic and photovoltaic properties cannot be excluded. Here we carried out periodic density functional theory and Car-Parrinello molecular dynamics simulations, going down to ∼1% doping, to investigate the effect of chlorine on CH 3 NH 3 PbI 3 . We found that such a small doping has important effects on the dynamics of the crystalline structure, both with respect to the inorganic framework and with respect to the cation libration motion. Together, we observe a dynamic spatial localization of the valence and conduction states in separated spatial material regions, which takes place in the 10 -1 ps time scale and which could be the key to ease of exciton dissociation and, likely, to small charge recombination in hybrid perovskites. Moreover, such localization is enhanced by chlorine doping, demonstrating an inherent positive role of chlorine doping on the electronic properties of this class of materials.

  10. Surface passivation of mixed-halide perovskite CsPb(BrxI1-x)3 nanocrystals by selective etching for improved stability.

    Science.gov (United States)

    Jing, Qiang; Zhang, Mian; Huang, Xiang; Ren, Xiaoming; Wang, Peng; Lu, Zhenda

    2017-06-08

    In recent years, there has been an unprecedented rise in the research of halide perovskites because of their important optoelectronic applications, including photovoltaic cells, light-emitting diodes, photodetectors and lasers. The most pressing question concerns the stability of these materials. Here faster degradation and PL quenching are observed at higher iodine content for mixed-halide perovskite CsPb(Br x I 1-x ) 3 nanocrystals, and a simple yet effective method is reported to significantly enhance their stability. After selective etching with acetone, surface iodine is partially etched away to form a bromine-rich surface passivation layer on mixed-halide perovskite nanocrystals. This passivation layer remarkably stabilizes the nanocrystals, making their PL intensity improved by almost three orders of magnitude. It is expected that a similar passivation layer can also be applied to various other kinds of perovskite materials with poor stability issues.

  11. Growth and luminescence properties of Pr3+-doped single crystalline films of garnets and perovskites

    International Nuclear Information System (INIS)

    Gorbenko, V.; Zorenko, Yu.; Savchyn, V.; Zorenko, T.; Pedan, A.; Shkliarskyi, V.

    2010-01-01

    Peculiarities of growth of single crystalline films (SCF) of Pr 3+ doped Y 3 Al 5 O 12 and Lu 3 Al 5 O 12 garnets and YAlO 3 and LuAlO 3 perovskites by the liquid phase epitaxy method from melt-solutions based on PbO-B 2 O 3 flux as well as luminescent and scintillation properties of these SCFs were studied in this work. Dependence the intensity of the Pr 3+ d-f and f-f-luminescence on the activator concentration and influence of Pb 2+ flux dopant on the light yield of SCFs of the mentioned garnets and perovskites were analyzed.

  12. Jahn-Teller distortions, cation ordering and octahedral tilting in perovskites

    International Nuclear Information System (INIS)

    Lufaso, M.W.; Woodward, P.M.

    2004-01-01

    In transition metal oxides, preferential occupation of specific d orbitals on the transition metal ion can lead to the development of a long-range ordered pattern of occupied orbitals. This phenomenon, referred to as orbital ordering, is usually observed indirectly from the cooperative Jahn-Teller distortions (CJTDs) that result as a consequence of the orbital ordering. This paper examines the interplay between orbital ordering, octahedral tilting and cation ordering in perovskites. Both ternary AMX 3 perovskites containing an active Jahn-Teller (J-T) ion on the octahedral site and quaternary A 2 MM'X 6 perovskites containing a J-T ion on one-half of the octahedral sites have been examined. In AMX 3 perovskites, the tendency is for the occupied 3d 3x 2 -r 2 and 3d 3z 2 -r 2 orbitals to order in the ac plane, as exemplified by the crystal structures of LaMnO 3 and KCuF 3 . This arrangement maintains a favorable coordination environment for the anion sites. In AMX 3 perovskites, octahedral tilting tends to enhance the magnitude of the J-T distortions. In A 2 MM'X 6 perovskites, the tendency is for the occupied 3d 3z 2 -r 2 orbitals to align parallel to the c axis. This pattern maintains a favorable coordination environment about the symmetric M'-cation site. The orbital ordering found in rock-salt ordered A 2 MM'X 6 perovskites is compatible with octahedral rotations about the c axis (Glazer tilt system a 0 a 0 c - ) but appears to be incompatible with GdFeO 3 -type octahedral tilting (tilt system - b + a - ). (orig.)

  13. Effect of vitamin D deficiency in Korean patients with acute respiratory distress syndrome.

    Science.gov (United States)

    Park, Sojung; Lee, Min Gi; Hong, Sang-Bum; Lim, Chae-Man; Koh, Younsuck; Huh, Jin Won

    2018-06-20

    Vitamin D modulates innate and adaptive immune responses, and vitamin D deficiency is associated with increased mortality in hospitalized patients with pneumonia. We evaluated the prevalence of vitamin D deficiency in Korean patients with acute respiratory distress syndrome (ARDS) and its effect on the clinical outcomes of ARDS. We retrospectively analyzed the data of 108 patients who had a measured serum level of 25-hydroxy vitamin D3 (25(OH)D3) at the time of diagnosis with ARDS. The clinical outcomes were evaluated based on 25(OH)D3 levels of 20 ng/mL and stratified by quartiles of 25(OH)D3 levels. The mean age of patients was 59.4 years old; 77 (71.3%) were male. Vitamin D deficiency was found in 103 patients (95.4%). The mean 25(OH)D3 level was 8.3 ± 7.0 ng/mL. Neither in-hospital mortality (40.0% vs. 68.0%) nor 6-month mortality (40.0% vs. 71.8%) significantly differed between groups. There were no significant differences in 25(OH)D3 level between survivors (8.1 ± 7.6 ng/mL) and non-survivors (8.5 ± 6.8 ng/mL, p = 0.765). There were no trends toward a difference in mortality among quartiles of 25(OH)D3 levels. However, 25(OH)D3 levels were inversely related with length of hospital stay and intensive care unit stay among in-hospital survivors. Vitamin D deficiency was prevalent in Korean patients with ARDS. However, levels of vitamin D were not associated with mortality. A large, prospective study is needed to evaluate the effects of vitamin D deficiency on clinical outcomes of ARDS.

  14. Efficiency enhancement of perovskite solar cells using structural and morphological improvement of CH3NH3PbI3 absorber layers

    Science.gov (United States)

    Alidaei, Maryam; Izadifard, Morteza; Ghazi, Mohammad E.; Ahmadi, Vahid

    2018-01-01

    Perovskite solar cells have been heavily investigated due to their unique properties such as high power conversion efficiency (PCE), low-cost fabrication by solution processes, high diffusion length, large absorption coefficient, and direct and tunable band gap. PCE of perovskite devices is strongly dependent on the absorber layer properties such as morphology, crystallinity, and compactness, which are required to be optimized. In this work, the CH3NH3PbI3 (170-480 nm) absorber layers with various methylammonium iodine (MAI) concentrations (7, 10, 20 and 40 mg ml-1) and perovskite solar cells with the fluorine-doped tin oxide (400 nm)/C-TiO2 (30 nm)/Meso-TiO2 (400 nm)/CH3NH3PbI3 (170-480 nm)/P3HT (30 nm)/Au (100 nm) structure were fabricated. A two-step solution process was used for deposition of the CH3NH3PbI3 absorber layers. The morphology, crystal structure, and optical properties of the perovskite layer grown on glass and also the photovoltaic properties of the fabricated solar cells were studied. The results obtained showed that by controlling the deposition conditions, due to the reduction in charge recombination, PCE enhancement of the perovskite solar cell (up to 11.6%) was accessible.

  15. Systematic study of photoluminescence upon band gap excitation in perovskite-type titanates R 1/2Na1/2TiO3:Pr (R=La, Gd, Lu, and Y)

    International Nuclear Information System (INIS)

    Inaguma, Yoshiyuki; Tsuchiya, Takeshi; Katsumata, Tetsuhiro

    2007-01-01

    Pr 3+ -doped perovskites R 1/2 Na 1/2 TiO 3 :Pr (R=La, Gd, Lu, and Y) were synthesized, and their structures, optical absorption and luminescent properties were investigated, and the relationship between structures and optical properties are discussed. Optical band gap of R 1/2 Na 1/2 TiO 3 increases in the order R=La, Gd, Y, and Lu, which is primarily due to a decrease in band width accompanied by a decrease in Ti-O-Ti bond angle. Intense red emission assigned to f-f transition of Pr 3+ from the excited 1 D 2 level to the ground 3 H 4 state upon the band gap photo-excitation (UV) was observed for all compounds. The wavelength of emission peaks was red-shifted in the order R=La, Gd, Y, and Lu, which originates from the increase in crystal field splitting of Pr 3+ . This is attributed to the decrease in inter-atomic distances of Pr-O together with the inter-atomic distances (R, Na)-O, i.e., increase in covalency between Pr and O. The results indicate that the luminescent properties in R 1/2 Na 1/2 TiO 3 :Pr are governed by the relative energy level between the ground and excited state of 4f 2 for Pr 3+ , and the conduction and valence band, which is primarily dependent on the structure, e.g., the tilt of TiO 6 octahedra and the Pr-Ti inter-atomic distance and the site symmetry of Pr ion. - Graphical abstract: The red intense emission assigned to f-f transition of Pr 3+ from the excited 1 D 2 level to the ground 3 H 4 state upon the band gap photo-excitation (UV) was observed upon the band gap photo-excitation in perovskites R 1/2 Na 1/2 TiO 3 :Pr(R=La, Gd, Lu, and Y). It was found that the systematic changes in their luminescent properties are strongly dependent on the structure

  16. Thermally induced A'-A site exchange in novel layered perovskites Ag2[Ca1.5M3O10] (M = Nb, Ta).

    Science.gov (United States)

    Bhuvanesh, Nattamai S P; Woodward, Patrick M

    2002-12-04

    We have synthesized and characterized new layered perovskites Ag2[A1.5M3O10] (A = Ca, M = Nb, Ta), from their lithium analogues, by soft-chemical ion exchange. These oxides show topotactic irreversible thermally induced A'-A site exchange, resulting in Ag1.1Ca0.9[Ca0.6Ag0.9M3O10], conferred from our high-temperature X-ray and ionic conductivity studies. The latter phases are the first compounds where Ag+ ions reside in both A' and A sites in layered perovskites. The absence of similar phase transition for A = Sr suggests that these transitions strongly depend on the size, charge, and the coordination preference of A' and A cations. This result provides a new synthetic tool for modifying the occupation of the 12-coordinate A site of layered perovskites using soft chemical routes.

  17. Influence of the sintering temperature on the Sr content in a Ca_(_1_−_x_−_y_)Ce_xSr_yAl_zTi_(_1_−_z_)O_3 perovskite (x = 0.04–0.16) co-doped with Ce

    International Nuclear Information System (INIS)

    Kamel, Nour-el-hayet; Mouheb, Yasmina; Kamel, Ziane; Moudir, Dalila; Aouchiche, Fairouz; Arabi, Azeddine

    2016-01-01

    A Sr-Ce co-doped perovskite, with the chemical formula: Ca_(_1_−_x_−_y_)Ce_xSr_yAl_zTi_(_1_−_z_)O_3 (y = 0.04, 0.08, 0.12 and 0.16, x = 0.05) is synthesized by sol–gel process. The influence of the sintering temperature, Ts, on the rate of inserted Sr was investigated at 1223, 1373 and 1473 K. The Sr amount sequestered in the perovskite reaches 85% (y = 0.16, 9.50 wt%) for Ts = 1373 K, giving sintering densities between 3.520 and 4.400. XRD analysis reveals an orthorhombic CaTiO_3 structure. The lattice parameters obey to Vegard’s law for Ts = 1373 and 1473 K. SEM analysis shows orthorhombic grains of 0.514 μm × 1 μm mean dimensions. MCC1 and MCC2 tests, performed on minerals sintered at 1373 K, indicate that the most durable one is that containing 9.50 wt% Sr. MCC1 test gave 6.998·10"−"6 g/cm"2 d of Sr, and MCC2 2.143·10"−"4 g/cm"2 d of Ce. The temperature favors the Sr dissolution to the detriment of Ce. The Ca dissolution rate reaches 1.002·10"−"6 to 2.005·10"−"6 g/cm"2 d. - Highlights: • Ca_(_1_−_x_−_y_)Ce_xSr_yAl_zTi_(_1_−_z_)O_3 perovskite is synthesized by sol–gel. • The influence of the sintering temperature, Ts, on the rate of inserted Sr was investigated at 1223, 1373 and 1473 K. • 85% of total Sr was sequestered in the perovskite for Ts = 1373 K. • MCC1 and MCC2 leach tests indicate that the most durable mineral is that containing 9.50 wt.% Sr. • MCC1 test gave 8.10 10"−"1"0 kg/m"2.d Sr. The lower is the leaching temperature the higher is the mineral durability.

  18. Three-dimensional oriented attachment growth of single-crystal pre-perovskite PbTiO3 hollowed fibers

    KAUST Repository

    Zhao, Ruoyu

    2017-12-11

    Hollowed single-crystal pre-perovskite PbTiO fibers (PP-PTF) were successfully synthesized via a polyvinyl alcohol (PVA) assisted hydrothermal process. The as-prepared PP-PTF were characterized to be 0.3-1 μm in diameter and tens of micrometers in length by adjusting the concentration of PVA to 0.8 g L. Microstructure characterization of the samples at different reaction times revealed that PP-PTF were formed via a three-dimensional (3D) hierarchical oriented attachment (OA) growth process. The initial growth units were determined to be single-crystal pre-perovskite PbTiO fibers with a diameter of 10-20 nm. Zeta potential measurement suggested that the main driving force of the OA process is the surface electrostatic force, which is induced by the incompletely bonded Pb and O atomic layers on the surface of the {110} plane. Moreover, molecular dynamics simulations have been employed to reveal a stable configuration of the initial pre-perovskite PbTiO growth units, agreeing well with the experimental results.

  19. Fabrication and Characterization of CH3NH3PbI3−x−yBrxCly Perovskite Solar Cells

    Directory of Open Access Journals (Sweden)

    Atsushi Suzuki

    2016-05-01

    Full Text Available Fabrication and characterization of CH3NH3PbI3−x−yBrxCly perovskite solar cells using mesoporous TiO2 as electron transporting layer and 2,2′,7,7′-tetrakis-(N,N-di-4-methoxyphenylamino-9,9′-spirobifluorene as a hole-transporting layer (HTL were performed. The purpose of the present study is to investigate role of halogen doping using iodine (I, bromine (Br and chlorine (Cl compounds as dopant on the photovoltaic performance and microstructures of CH3NH3PbI3−x−yBrxCly perovskite solar cells. The X-ray diffraction identified a slight decrease of crystal spacing in the perovskite crystal structure doped with a small amount of I, Br, and Cl in the perovskite compounds. Scanning electron microscopy (SEM and energy dispersive X-ray spectroscopy (EDX showed the perovskite crystal behavior depended on molar ratio of halogen of Pb, I, Br and Cl. Incorporation of the halogen doping into the perovskite crystal structure improved photo generation, carrier diffusion without carrier recombination in the perovskite layer and optimization of electronic structure related with the photovoltaic parameters of open-circuit voltage, short-circuit current density and conversion efficiency. The energy diagram and photovoltaic mechanisms of the perovskite solar cells were discussed in the context of the experimental results.

  20. Perovskite phases in the systems Asup(II)O-UO/sub 3/. 1. Tetragonal perovskite Ba/sub 2/Basub(7/8)vacantsub(1/8)UO/sub 5/sub(7/8)

    Energy Technology Data Exchange (ETDEWEB)

    Griffiths, A J; Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.)

    1979-10-01

    The new tetragonal compound Ba/sub 2/Basub(7/8)vacantsub(1/8)UO/sub 5/sub(7/8) (a = 2 x 6.31/sub 2/ A; c = 2 x 8.76/sub 7/ A) has been found besides Ba/sub 3/UO/sub 6/ (triclinic) in the BaO-UO/sub 3/ system. It crystallizes with a superstructure of perovskite type. The differences in properties between Ba/sub 3/UO/sub 6/ and Ba/sub 2/Basub(7/8)vacantsub(1/8) UO/sub 5/sub(7/8) are discussed.

  1. New lithium-ion conducting perovskite oxides related to (Li, La)TiO3

    Indian Academy of Sciences (India)

    Unknown

    We describe the synthesis and lithium-ion conductivity of new perovskite-related oxides ... work on lithium-ion conducting perovskite oxides containing d0 cations. Keywords. ..... On the other hand, Nb/Ta compounds show a higher conductivity.

  2. Functional engineering of perovskite nanosheets. Impact of lead substitution on exfoliation in the solid solution RbCa{sub 2-x}Pb{sub x}Nb{sub 3}O{sub 10}

    Energy Technology Data Exchange (ETDEWEB)

    Ziegler, Christian; Lotsch, Bettina V. [Max Planck Institute for Solid State Research, Stuttgart (Germany); Department of Chemistry, University of Munich (LMU), Munich (Germany); Nanosystems Initiative Munich (NIM) and Center for Nanoscience (CeNS), Munich (Germany); Dennenwaldt, Teresa [Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf (Germany); Ecole Polytechnique Federale de Lausanne (Switzerland); Weber, Daniel; Duppel, Viola; Kamella, Claudia; Tuffy, Brian; Moudrakovski, Igor [Max Planck Institute for Solid State Research, Stuttgart (Germany); Podjaski, Filip [Max Planck Institute for Solid State Research, Stuttgart (Germany); Ecole Polytechnique Federale de Lausanne (Switzerland); Scheu, Christina [Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf (Germany)

    2017-11-17

    Tuning the chemical composition and structure for targeted functionality in two-dimensional (2D) nanosheets has become a major objective in the rapidly growing area of 2D materials. In the context of photocatalysis, both miniaturization and extending the light absorption of UV active photocatalysts are major assets. Here, we investigate the solid solution between two photocatalytic systems known from literature to evolve H{sub 2} from water/methanol under UV - RbCa{sub 2}Nb{sub 3}O{sub 10} (E{sub g} = 3.7 eV) - and visible light irradiation - RbPb{sub 2}Nb{sub 3}O{sub 10} (E{sub g} = 3.0 eV) - by synthesizing hypothetical RbCa{sub 2-x}Pb{sub x}Nb{sub 3}O{sub 10}. While the calcium niobate can easily be exfoliated into individual nanosheets via cation-proton exchange and subsequent treatment with tetra-n-butylammonium hydroxide (TBAOH), the lead niobate barely yields nanosheets. Spectroscopic and microscopic analysis suggest that this is caused by volatilization of Pb during synthesis, leading to a local 3D linkage of RbPb{sub 2}Nb{sub 3}O{sub 10} perovskite units with Pb deficient units. On the one hand, this linkage progressively prevents exfoliation along with an increasing Pb content. On the other hand, introducing Pb into the perovskite blocks successively leads to bandgap narrowing, thus gradually enhancing the light harvesting capability of the solid solution. Finding a compromise between this narrowing of the bandgap and the possibility of exfoliation, visible light sensitized nanosheets can be engineered in good yield for an initial molar ratio of Ca:Pb ≥ 1:1. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Vitamin D-Dependent Rickets Type 1B (25-Hydroxylase Deficiency): A Rare Condition or a Misdiagnosed Condition?

    Science.gov (United States)

    Molin, Arnaud; Wiedemann, Arnaud; Demers, Nick; Kaufmann, Martin; Do Cao, Jérémy; Mainard, Laurent; Dousset, Brigitte; Journeau, Pierre; Abeguile, Geneviève; Coudray, Nadia; Mittre, Hervé; Richard, Nicolas; Weryha, Georges; Sorlin, Arthur; Jones, Glenville; Kottler, Marie-Laure; Feillet, Francois

    2017-09-01

    Vitamin D requires a two-step activation by hydroxylation: The first step is catalyzed by hepatic 25-hydroxylase (CYP2R1, 11p15.2) and the second one is catalyzed by renal 1α-hydroxylase (CYP27B1, 12q13.1), which produces the active hormonal form of 1,25-(OH) 2 D. Mutations of CYP2R1 have been associated with vitamin D-dependent rickets type 1B (VDDR1B), a very rare condition that has only been reported to affect 4 families to date. We describe 7 patients from 2 unrelated families who presented with homozygous loss-of-function mutations of CYP2R1. Heterozygous mutations were present in their normal parents. We identified a new c.124_138delinsCGG (p.Gly42_Leu46delinsArg) variation and the previously published c.296T>C (p.Leu99Pro) mutation. Functional in vitro studies confirmed loss-of-function enzymatic activity in both cases. We discuss the difficulties in establishing the correct diagnosis and the specific biochemical pattern, namely, very low 25-OH-D suggestive of classical vitamin D deficiency, in the face of normal/high concentrations of 1,25-(OH) 2 D. Siblings exhibited the three stages of rickets based on biochemical and radiographic findings. Interestingly, adult patients were able to maintain normal mineral metabolism without vitamin D supplementation. One index case presented with a partial improvement with 1alfa-hydroxyvitamin D 3 or alfacalcidol (1α-OH-D 3 ) treatment, and we observed a dramatic increase in the 1,25-(OH) 2 D serum concentration, which indicated the role of accessory 25-hydroxylase enzymes. Lastly, in patients who received calcifediol (25-OH-D 3 ), we documented normal 24-hydroxylase activity (CYP24A1). For the first time, and according to the concept of personalized medicine, we demonstrate dramatic improvements in patients who were given 25-OH-D therapy (clinical symptoms, biochemical data, and bone densitometry). In conclusion, the current study further expands the CYP2R1 mutation spectrum. We note that VDDR1B could be easily

  4. Optical characterization of voltage-accelerated degradation in CH3NH3PbI3 perovskite solar cells.

    Science.gov (United States)

    Handa, Taketo; Tex, David M; Shimazaki, Ai; Aharen, Tomoko; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

    2016-05-16

    We investigate the performance degradation mechanism of CH3NH3PbI3 perovskite solar cells under bias voltage in air and nitrogen atmospheres using photoluminescence and electroluminescence techniques. When applying forward bias, the power conversion efficiency of the solar cells decreased significantly in air, but showed no degradation in nitrogen atmosphere. Time-resolved photoluminescence measurements on these devices revealed that the application of forward bias in air accelerates the generation of non-radiative recombination centers in the perovskite layer buried in the device. We found a negative correlation between the electroluminescence intensity and the injected current intensity in air. The irreversible change of the perovskite grain surface in air initiates the degradation of the perovskite solar cells.

  5. Electron Transfer from Triplet State of TIPS-Pentacene Generated by Singlet Fission Processes to CH3NH3PbI3 Perovskite.

    Science.gov (United States)

    Lee, Sangsu; Hwang, Daesub; Jung, Seok Il; Kim, Dongho

    2017-02-16

    To reveal the applicability of singlet fission processes in perovskite solar cell, we investigated electron transfer from TIPS-pentacene to CH 3 NH 3 PbI 3 (MAPbI 3 ) perovskite in film phase. Through the observation of the shorter fluorescence lifetime in TIPS-pentacene/MAPbI 3 perovskite bilayer film (5 ns) compared with pristine MAPbI 3 perovskite film (20 ns), we verified electron-transfer processes between TIPS-pentacene and MAPbI 3 perovskite. Furthermore, the observation of singlet fission processes, a faster decay rate, TIPS-pentacene cations, and the analysis of kinetic profiles of the intensity ratio between 500 and 525 nm in the TA spectra of the TIPS-pentacene/MAPbI 3 perovskite bilayer film indicate that electron transfer occurs from triplet state of TIPS-pentacene generated by singlet fission processes to MAPbI 3 perovskite conduction band. We believe that our results can provide useful information on the design of solar cells sensitized by singlet fission processes and pave the way for new types of perovskite solar cells.

  6. Calcium doped MAPbI3 with better energy state alignment in perovskite solar cells

    Science.gov (United States)

    Lu, Chaojie; Zhang, Jing; Hou, Dagang; Gan, Xinlei; Sun, Hongrui; Zeng, Zhaobing; Chen, Renjie; Tian, Hui; Xiong, Qi; Zhang, Ying; Li, Yuanyuan; Zhu, Yuejin

    2018-05-01

    The organic-inorganic perovskite material with better energy alignment in the solar cell device will have a profound impact on the solar cell performance. It is valuable to tune the energy states by element substitution and doping in perovskites. Here, we present that Ca2+ is incorporated into CH3NH3PbI3, which up-shifts the valence band maximum and the conduction band minimum, leading to a difference between the bandgap and the Fermi level in the device. Consequently, Ca2+ incorporation results in an enhancement of the photovoltage and photocurrent, achieving a summit efficiency of 18.3% under standard 1 sun (AM 1.5). This work reveals the doped perovskite to improve the solar cell performance by tuning the energy state.

  7. A randomized clinical trial in vitamin D-deficient adults comparing replenishment with oral vitamin D3 with narrow-band UV type B light: effects on cholesterol and the transcriptional profiles of skin and blood.

    Science.gov (United States)

    Ponda, Manish P; Liang, Yupu; Kim, Jaehwan; Hutt, Richard; Dowd, Kathleen; Gilleaudeau, Patricia; Sullivan-Whalen, Mary M; Rodrick, Tori; Kim, Dong Joo; Barash, Irina; Lowes, Michelle A; Breslow, Jan L

    2017-05-01

    Background: Vitamin D deficiency, defined as a serum 25-hydroxyvitamin D [25(OH)D] concentration light. Objective: We tested the hypothesis that, in vitamin D-deficient adults, the replenishment of vitamin D with UVB exposure would lower LDL-cholesterol concentrations compared with the effect of oral vitamin D 3 supplementation. Design: We performed a randomized clinical trial in vitamin D-deficient adults and compared vitamin D replenishment between subjects who received oral vitamin D 3 ( n = 60) and those who received narrow-band UVB exposure ( n = 58) ≤6 mo. Results: There was no difference in the change from baseline LDL-cholesterol concentrations between oral vitamin D 3 and UVB groups (difference in median of oral vitamin D 3 minus that of UVB: 1.5 mg/dL; 95% CI: -5.0, 7.0 mg/dL). There were also no differences within groups or between groups for changes in total or HDL cholesterol or triglycerides. Transcriptional profiling of skin and blood, however, revealed significant upregulation of immune pathway signaling with oral vitamin D 3 but significant downregulation with UVB. Conclusions: Correcting vitamin D deficiency with either oral vitamin D 3 or UVB does not improve the lipid profile. Beyond cholesterol, these 2 modalities of raising 25(OH)D have disparate effects on gene transcription. This trial was registered at clinicaltrials.gov as NCT01688102. © 2017 American Society for Nutrition.

  8. High-Performance CH3NH3PbI3-Inverted Planar Perovskite Solar Cells with Fill Factor Over 83% via Excess Organic/Inorganic Halide.

    Science.gov (United States)

    Jahandar, Muhammad; Khan, Nasir; Lee, Hang Ken; Lee, Sang Kyu; Shin, Won Suk; Lee, Jong-Cheol; Song, Chang Eun; Moon, Sang-Jin

    2017-10-18

    The reduction of charge carrier recombination and intrinsic defect density in organic-inorganic halide perovskite absorber materials is a prerequisite to achieving high-performance perovskite solar cells with good efficiency and stability. Here, we fabricated inverted planar perovskite solar cells by incorporation of a small amount of excess organic/inorganic halide (methylammonium iodide (CH 3 NH 3 I; MAI), formamidinium iodide (CH(NH 2 ) 2 I; FAI), and cesium iodide (CsI)) in CH 3 NH 3 PbI 3 perovskite film. Larger crystalline grains and enhanced crystallinity in CH 3 NH 3 PbI 3 perovskite films with excess organic/inorganic halide reduce the charge carrier recombination and defect density, leading to enhanced device efficiency (MAI+: 14.49 ± 0.30%, FAI+: 16.22 ± 0.38% and CsI+: 17.52 ± 0.56%) compared to the efficiency of a control MAPbI 3 device (MAI: 12.63 ± 0.64%) and device stability. Especially, the incorporation of a small amount of excess CsI in MAPbI 3 perovskite film leads to a highly reproducible fill factor of over 83%, increased open-circuit voltage (from 0.946 to 1.042 V), and short-circuit current density (from 18.43 to 20.89 mA/cm 2 ).

  9. Phase transition in metastable perovskite Pb(AlNb)0,5O3

    International Nuclear Information System (INIS)

    Zhabko, T.E.; Olekhnovich, N.M.; Shilin, A.D.

    1987-01-01

    Dielectric properties of metastable perovskite Pb(AlNb) 0.5 O 3 and X-ray temperature investigations of both perovskite and pyrochlore modifications of the given compound are studied. Samples with the perovskite structure are prepared from the pyrochlorephase at 4-5 GPa pressure and 1170-1270 K. Ferroelectric phase transition is shown to occur in the metastable perovskite phase Pb(AlNb) 0.5 O 3 at 170 K

  10. Band gap and mobility of epitaxial perovskite BaSn1 -xHfxO3 thin films

    Science.gov (United States)

    Shin, Juyeon; Lim, Jinyoung; Ha, Taewoo; Kim, Young Mo; Park, Chulkwon; Yu, Jaejun; Kim, Jae Hoon; Char, Kookrin

    2018-02-01

    A wide band-gap perovskite oxide BaSn O3 is attracting much attention due to its high electron mobility and oxygen stability. On the other hand, BaHf O3 was recently reported to be an effective high-k gate oxide. Here, we investigate the band gap and mobility of solid solutions of BaS n1 -xH fxO3 (x =0 -1 ) (BSHO) as a basis to build advanced perovskite oxide heterostructures. All the films were epitaxially grown on MgO substrates using pulsed laser deposition. Density functional theory calculations confirmed that Hf substitution does not create midgap states while increasing the band gap. From x-ray diffraction and optical transmittance measurements, the lattice constants and the band-gap values are significantly modified by Hf substitution. We also measured the transport properties of n -type La-doped BSHO films [(Ba ,La ) (Sn ,Hf ) O3 ] , investigating the feasibility of modulation doping in the BaSn O3/BSHO heterostructures. The Hall measurement data revealed that, as the Hf content increases, the activation rate of the La dopant decreases and the scattering rate of the electrons sharply increases. These properties of BSHO films may be useful for applications in various heterostructures based on the BaSn O3 system.

  11. Vitamin D deficiency among the elderly: insights from Qatar.

    Science.gov (United States)

    Alhamad, Hanadi Khamis; Nadukkandiyil, Navas; El-Menyar, Ayman; Abdel Wahab, Luay; Sankaranarayanan, Anoop; Al Sulaiti, Essa Mubarak

    2014-06-01

    Vitamin D (VitD) deficiency is associated with comorbidities in the elderly. The present study investigates the prevalence of VitD deficiency among the elderly in Qatar. A retrospective study conducted between April 2010 and April 2012 that involved chart reviews. All elderly patients of age ≥65 years in geriatrics facilities including Rumailah hospital, skilled nursing facility and home healthcare services in Qatar were included in the study. Patient characteristics and outcomes were analyzed and compared according to the severity of VitD deficiency. Correlation of VitD with comorbidities was analyzed. Mean follow-up period was 6 months. A total of 889 patients were enrolled; the majority (66%) were females and the mean age was 75 ± 8.7 years. Patient comorbidities included hypertension (76.5%), diabetes mellitus (63%), dyslipidemia, (47.5%), dementia (26%) coronary artery disease (24%) and cerebrovascular accident (24%). The mean baseline serum VitD level was 24.4 ± 13.5 ng/ml; 72% of patients had VitD deficiency: mild (31%), moderate (30%) and severe (11%). Patients with severe VitD deficiency had significantly higher HbA1c levels compared with patients with optimal VitD (P = 0.03). High density lipoprotein (HDL-C) levels were significantly lower in severe VitD deficiency patients compared with optimal VitD patients (P = 0.04). There was a positive correlation between HDL-C and VitD level (r = 0.17, P = 0.001), whereas HbA1c levels showed negative correlation with VitD (r = -0.15, P = 0.009). A high prevalence of VitD deficiency (72%) was observed among the elderly in Qatar. Lower VitD was associated with higher HbA1c and lower HDL-C levels. Further studies are warranted to evaluate whether VitD supplementation controls diabetes mellitus (DM) and low HDL-C levels among the elderly.

  12. High-temperature compressive creep behaviour of perovskite-type oxides SrTi1-xFexO3

    NARCIS (Netherlands)

    ten Donkelaar, S.F.P.; Stournari, V.; Malzbender, J.; Nijmeijer, Arian; Bouwmeester, Henricus J.M.

    2015-01-01

    Compressive creep tests have been performed on mixed ionic-electronic conducting perovskite-type oxides SrTi1-xFexO3- (STF, x = 0.3, 0.5 and 0.7). Observed activation energies and stress exponents, at 800–1000 ◦C and in the stress range 10 100 MPa, indicate that the steady-state creep rate of STF

  13. X-ray absorption investigation of the valence state and electronic structure of La1−xCaxCoO3−δ in comparison with La1−xSrxCoO3−δ and La1−xSrxFeO3−δ

    International Nuclear Information System (INIS)

    Haas, O.; Ludwig, Chr.; Bergmann, U.; Singh, R.N.; Braun, A.; Graule, T.

    2011-01-01

    3d metal K-shell X-ray absorption spectra of perovskites with the composition La 1−x Ca x CoO 3−δ (x=0, 0.2, 0.4, 0.5, 0.6, 0.8), La 1−x Sr x CoO 3−δ (x=0, 0.1, 0.2, 0.3, 0.4, 0.5) and La 1−x Sr x FeO 3−δ (x=0, 0.2, 0.4, 0.5, 0.6, 0.8) are compared on the basis of pre-edges, white line features and extended fine structures. The measurements were performed at 300 K and for La 1−x Ca x CoO 3−δ also at temperatures as low as 10–20 K. Going to low-temperature the measurements indicate an increase in t 2g ⁎ and a decrease in e g ⁎ orbital occupancy, which is most accentuated in the LaCoO 3 sample. Virtually no Co K-edge shift was observed for the La 1−x Ca x CoO 3−δ and La 1−x Sr x CoO 3−δ compounds and the Co–O distances are also not significantly reduced when La 3+ is partially substituted by Ca 2+ or Sr 2+ . From the pre-edge features of these perovskites we are tended to conclude that the t 2g ⁎ orbitals are less, and the e g ⁎ orbitals are more occupied with increasing x in the Ca and Sr substituted compounds, whereas the total d-electron density is not changing. These results indicate that cobalt prefers a valence state of 3 + in these Co perovskites. This could also be confirmed with iodometric titrations. The Fe perovskites behave differently. In contrast to the Co perovskites, for La 1−x Sr x FeO 3−δ perovskites the Fe K-edge is shifted, the pre-edge features intensity is increasing and the Fe–O bond length is decreasing with increasing x. The valence states of the iron in the La 1−x Sr x FeO 3−δ perovskites in fact increase as much as x increases. - Graphical abstract: Co K and Fe K pre-edge of La 1−x Ca x CoO 3−δ and La 1−x Sr x FeO 3−δ perovskites one of the evidences in favor of δ=x/2 for the Co-perovskites and δ=0 for the Fe-perovskites. Highlights: ► XAS a valuable tool to evaluate the valence states of Co and Fe perovskites. ► For La 1−x Ca x CoO 3−δ and La 1−x Sr x CoO 3

  14. 1,25-Dihydroxyvitamin D3 regulates genes responsible for detoxification in intestine

    International Nuclear Information System (INIS)

    Kutuzova, Galina D.; DeLuca, Hector F.

    2007-01-01

    1α,25-Dihydroxyvitamin D 3 (1,25-(OH) 2 D 3 ), the biologically active form of vitamin D 3 , not only plays a major role in mammalian calcium and phosphorous homeostasis but also exerts pleiotropic effects on cell proliferation, differentiation and the immune system. Further, vitamin D is believed to play a significant role in the prevention of colon, prostate, and breast cancer and in reducing the risk of autoimmune diseases. To gain insight into the mechanism whereby vitamin D can have such diverse actions, we have employed microarray technology. We studied the effect of a single dose of 1,25-(OH) 2 D 3 on gene expression in the intestine of vitamin D-deficient rats. Within 6 h, 1,25-(OH) 2 D 3 stimulates the expression of several phase I and phase II biotransformation genes. There is also an increased expression of antioxidant genes. These results support the idea that vitamin D is a significant factor in detoxification and protection against environmental toxins

  15. Electrical Stress Influences the Efficiency of CH3 NH3 PbI3 Perovskite Light Emitting Devices.

    Science.gov (United States)

    Zhao, Lianfeng; Gao, Jia; Lin, YunHui L; Yeh, Yao-Wen; Lee, Kyung Min; Yao, Nan; Loo, Yueh-Lin; Rand, Barry P

    2017-06-01

    Organic-inorganic hybrid perovskite materials are emerging as semiconductors with potential application in optoelectronic devices. In particular, perovskites are very promising for light-emitting devices (LEDs) due to their high color purity, low nonradiative recombination rates, and tunable bandgap. Here, using pure CH 3 NH 3 PbI 3 perovskite LEDs with an external quantum efficiency (EQE) of 5.9% as a platform, it is shown that electrical stress can influence device performance significantly, increasing the EQE from an initial 5.9% to as high as 7.4%. Consistent with the enhanced device performance, both the steady-state photoluminescence (PL) intensity and the time-resolved PL decay lifetime increase after electrical stress, indicating a reduction in nonradiative recombination in the perovskite film. By investigating the temperature-dependent characteristics of the perovskite LEDs and the cross-sectional elemental depth profile, it is proposed that trap reduction and resulting device-performance enhancement is due to local ionic motion of excess ions, likely excess mobile iodide, in the perovskite film that fills vacancies and reduces interstitial defects. On the other hand, it is found that overstressed LEDs show irreversibly degraded device performance, possibly because ions initially on the perovskite lattice are displaced during extended electrical stress and create defects such as vacancies. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Structural characterization of a new vacancy ordered perovskite modification found for Ba3Fe3O7F (BaFeO2.333F0.333): Towards understanding of vacancy ordering for different perovskite-type ferrites

    International Nuclear Information System (INIS)

    Clemens, Oliver

    2015-01-01

    The new vacancy ordered perovskite-type compound Ba 3 Fe 3 O 7 F (BaFeO 2.33 F 0.33 ) was prepared by topochemical low-temperature fluorination of Ba 2 Fe 2 O 5 (BaFeO 2.5 ) using stoichiometric amounts of polyvinylidene difluoride (PVDF). The vacancy order was found to be unique so far for perovskite compounds, and the connectivity pattern can be explained by the formula Ba 3 (FeX 6/2 ) (FeX 5/2 ) (FeX 3/2 X 1/1 ), with X=O/F. Mössbauer measurements were used to confirm the structural analysis and agree with the presence of Fe 3+ in the above mentioned coordination environments. Group–subgroup relationships were used to build a starting model for the structure solution and to understand the relationship to the cubic perovskite structure. Furthermore, a comparison of a variety of vacancy-ordered iron-containing perovskite-type structures is given, highlighting the factors which favour one structure type over the other depending on the composition. - Graphical abstract: The crystal structure of Ba 3 Fe 3 O 7 F in comparison to other perovskite type ferrites. - Highlights: • The crystal structure of Ba 3 Fe 3 O 7 F in comparison to other perovskite type ferrites. • Ba 3 Fe 3 O 7 F was synthesized by low temperature fluorination of Ba 2 Fe 2 O 5 . • Ba 3 Fe 3 O 7 F shows a unique vacancy order not found for other perovskite type compounds. • The structure of Ba 3 Fe 3 O 7 F was solved using group–subgroup relationships. • A systematic comparison to other ferrite type compounds reveals structural similarities and differences. • The A-site coordination of the cation is shown to play an important role for the type of vacancy order found

  17. Transport, Optical, and Magnetic Properties of the Conducting Halide Perovskite CH 3NH 3SnI 3

    Science.gov (United States)

    Mitzi, D. B.; Feild, C. A.; Schlesinger, Z.; Laibowitz, R. B.

    1995-01-01

    A low-temperature ( T ≤ 100°C) solution technique is described for the preparation of polycrystalline and single crystal samples of the conducting halide perovskite, CH 3NH 3SnI 3. Transport, Hall effect, magnetic, and optical properties are examined over the temperature range 1.8-300 K, confirming that this unusual conducting halide perovskite is a low carrier density p-type metal with a Hall hole density, 1/ RHe ≃ 2 × 10 19 cm -3. The resistivity of pressed pellet samples decreases with decreasing temperature with resistivity ratio ρ(300 K)/ρ(2 K) ≃ 3 and room temperature resistivity ρ(300 K) ≃ 7 mΩ-cm. A free-carrier infrared reflectivity spectrum with a plasma edge observed at approximately 1600 cm -1 further attests to the metallic nature of this compound and suggests a small optical effective mass, m* ≃ 0.2.

  18. Vitamin D Deficiency Is Associated With the Severity of Radiation-Induced Proctitis in Cancer Patients

    International Nuclear Information System (INIS)

    Ghorbanzadeh-Moghaddam, Amir; Gholamrezaei, Ali; Hemati, Simin

    2015-01-01

    Purpose: Radiation-induced injury to normal tissues is a common complication of radiation therapy in cancer patients. Considering the role of vitamin D in mucosal barrier hemostasis and inflammatory responses, we investigated whether vitamin D deficiency is associated with the severity of radiation-induced acute proctitis in cancer patients. Methods and Materials: This prospective observational study was conducted in cancer patients referred for pelvic radiation therapy. Serum concentration of 25-hydroxyvitamin D was measured before radiation therapy. Vitamin D deficiency was defined as 25-hydroxyvitamin D concentrations of <35 nmol/L and <40 nmol/L in male and female patients, respectively, based on available normative data. Acute proctitis was assessed after 5 weeks of radiation therapy (total received radiation dose of 50 Gy) and graded from 0 to 4 using Radiation Therapy Oncology Group (RTOG) criteria. Results: Ninety-eight patients (57.1% male) with a mean age of 62.8 ± 9.1 years were studied. Vitamin D deficiency was found in 57 patients (58.1%). Symptoms of acute proctitis occurred in 72 patients (73.4%) after radiation therapy. RTOG grade was significantly higher in patients with vitamin D deficiency than in normal cases (median [interquartile range] of 2 [0.5-3] vs 1 [0-2], P=.037). Vitamin D deficiency was associated with RTOG grade of ≥2, independent of possible confounding factors; odds ratio (95% confidence interval) = 3.07 (1.27-7.50), P=.013. Conclusions: Vitamin D deficiency is associated with increased severity of radiation-induced acute proctitis. Investigating the underlying mechanisms of this association and evaluating the effectiveness of vitamin D therapy in preventing radiation-induced acute proctitis is warranted

  19. Vitamin D Deficiency Is Associated With the Severity of Radiation-Induced Proctitis in Cancer Patients

    Energy Technology Data Exchange (ETDEWEB)

    Ghorbanzadeh-Moghaddam, Amir [Medical Student' s Research Center, Isfahan University of Medical Sciences, Isfahan (Iran, Islamic Republic of); Gholamrezaei, Ali, E-mail: Gholamrezaei@med.mui.ac.ir [Medical Student' s Research Center, Isfahan University of Medical Sciences, Isfahan (Iran, Islamic Republic of); Poursina Hakim Research Institution, Isfahan (Iran, Islamic Republic of); Hemati, Simin [Department of Radiotherapy Oncology, Isfahan University of Medical Sciences, Isfahan (Iran, Islamic Republic of)

    2015-07-01

    Purpose: Radiation-induced injury to normal tissues is a common complication of radiation therapy in cancer patients. Considering the role of vitamin D in mucosal barrier hemostasis and inflammatory responses, we investigated whether vitamin D deficiency is associated with the severity of radiation-induced acute proctitis in cancer patients. Methods and Materials: This prospective observational study was conducted in cancer patients referred for pelvic radiation therapy. Serum concentration of 25-hydroxyvitamin D was measured before radiation therapy. Vitamin D deficiency was defined as 25-hydroxyvitamin D concentrations of <35 nmol/L and <40 nmol/L in male and female patients, respectively, based on available normative data. Acute proctitis was assessed after 5 weeks of radiation therapy (total received radiation dose of 50 Gy) and graded from 0 to 4 using Radiation Therapy Oncology Group (RTOG) criteria. Results: Ninety-eight patients (57.1% male) with a mean age of 62.8 ± 9.1 years were studied. Vitamin D deficiency was found in 57 patients (58.1%). Symptoms of acute proctitis occurred in 72 patients (73.4%) after radiation therapy. RTOG grade was significantly higher in patients with vitamin D deficiency than in normal cases (median [interquartile range] of 2 [0.5-3] vs 1 [0-2], P=.037). Vitamin D deficiency was associated with RTOG grade of ≥2, independent of possible confounding factors; odds ratio (95% confidence interval) = 3.07 (1.27-7.50), P=.013. Conclusions: Vitamin D deficiency is associated with increased severity of radiation-induced acute proctitis. Investigating the underlying mechanisms of this association and evaluating the effectiveness of vitamin D therapy in preventing radiation-induced acute proctitis is warranted.

  20. Ligand-Stabilized Reduced-Dimensionality Perovskites

    KAUST Repository

    Quan, Li Na; Yuan, Mingjian; Comin, Riccardo; Voznyy, Oleksandr; Beauregard, Eric M.; Hoogland, Sjoerd; Buin, Andrei; Kirmani, Ahmad R.; Zhao, Kui; Amassian, Aram; Kim, Dong Ha; Sargent, Edward H.

    2016-01-01

    Metal halide perovskites have rapidly advanced thin film photovoltaic performance; as a result, the materials’ observed instabilities urgently require a solution. Using density functional theory (DFT), we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers introduces quantitatively appreciable van der Waals interactions; and these drive an increased formation energy and should therefore improve material stability. Here we report the reduced-dimensionality (quasi-2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three-dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoichiometry in materials synthesis. We achieved the first certified hysteresis-free solar power conversion in a planar perovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity.

  1. Ligand-Stabilized Reduced-Dimensionality Perovskites

    KAUST Repository

    Quan, Li Na

    2016-02-03

    Metal halide perovskites have rapidly advanced thin film photovoltaic performance; as a result, the materials’ observed instabilities urgently require a solution. Using density functional theory (DFT), we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers introduces quantitatively appreciable van der Waals interactions; and these drive an increased formation energy and should therefore improve material stability. Here we report the reduced-dimensionality (quasi-2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three-dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoichiometry in materials synthesis. We achieved the first certified hysteresis-free solar power conversion in a planar perovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity.

  2. Predictors of Vitamin D Deficiency in Predialysis Patients with Stage ...

    African Journals Online (AJOL)

    Objective: Vitamin D status and risk factors of Vitamin D deficiency in chronic kidney disease (CKD) patients in China have been seldom reported before. In this study, we aim to investigate serum 25‑hydroxyvitamin D [25(OH)D] status and find the predictors of Vitamin D deficiency in predialysis patients with Stage 3–5 CKDs ...

  3. Strong Photonic-Band-Gap Effect on the Spontaneous Emission in 3D Lead Halide Perovskite Photonic Crystals.

    Science.gov (United States)

    Zhou, Xue; Li, Mingzhu; Wang, Kang; Li, Huizeng; Li, Yanan; Li, Chang; Yan, Yongli; Zhao, Yongsheng; Song, Yanlin

    2018-03-25

    Stimulated emission in perovskite-embedded polymer opal structures is investigated. A polymer opal structure is filled with a perovskite, and perovskite photonic crystals are prepared. The spontaneous emission of the perovskite embedded in the polymer opal structures exhibits clear signatures of amplified spontaneous emission (ASE) via gain modulation. The difference in refractive-index contrast between the perovskite and the polymer opal is large enough for retaining photonic-crystals properties. The photonic band gap has a strong effect on the fluorescence emission intensity and lifetime. The stimulated emission spectrum exhibits a narrow ASE rather than a wide fluorescence peak in the thin film. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. The inverse perovskite nitrides (Sr{sub 3}N{sub 2/3-x})Sn, (Sr{sub 3}N{sub 2/3-x})Pb, and (Sr{sub 3}N)Sb. Flux crystal growth, crystal structures, and physical properties

    Energy Technology Data Exchange (ETDEWEB)

    Pathak, Manisha; Bobnar, Matej; Ormeci, Alim; Prots, Yurii; Hoehn, Peter [Chemische Metallkunde, Max-Planck-Institut fuer Chemische Physik fester Stoffe, Dresden (Germany); Stoiber, Dominik; Niewa, Rainer [Institut fuer Anorganische Chemie, Universitaet Stuttgart (Germany)

    2018-02-15

    Black single crystals with metallic luster of (Sr{sub 3}N{sub 2/3-x})E (E = Sn, Pb) and (Sr{sub 3}N)Sb were grown in lithium flux from strontium nitride, Sr{sub 2}N, and tin, lead, or antimony, respectively. Nitrogen deficiency in the tin and the lead compound is a result of the higher ionic charge of the tetrelide ions E{sup 4-} as compared to the antimonide ion Sb{sup 3-}. In contrast to microcrystalline samples from solid state sinter reactions obtained earlier, the flux synthesis induces nitrogen order in the nitrogen deficient tetrelides. The antimony compound crystallizes as inverse cubic perovskite [a = 517.22(5) pm, Z = 1, space group Pm3m, no. 221] with fully occupied nitrogen site, whereas the nitrogen deficient tin and lead compounds exhibit partially ordered arrangements and a certain phase width in respect to nitrogen contents. For the tetrelides, the nitrogen order leads to a cubic 2 x 2 x 2 superstructure [E = Sn: a = 1045.64(8) pm for x = 0, a = 1047.08(7) pm for x = 0.08; and E = Pb: a = 1050.7(1) pm for x = 0, space group Fm3m, no. 225] as derived from single-crystal X-ray diffraction data. The metallic tetrelides show diamagnetic behavior, which is consistent with electronic structure calculations. (copyright 2018 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Leaf-architectured 3D Hierarchical Artificial Photosynthetic System of Perovskite Titanates Towards CO2 Photoreduction Into Hydrocarbon Fuels

    Science.gov (United States)

    Zhou, Han; Guo, Jianjun; Li, Peng; Fan, Tongxiang; Zhang, Di; Ye, Jinhua

    2013-01-01

    The development of an “artificial photosynthetic system” (APS) having both the analogous important structural elements and reaction features of photosynthesis to achieve solar-driven water splitting and CO2 reduction is highly challenging. Here, we demonstrate a design strategy for a promising 3D APS architecture as an efficient mass flow/light harvesting network relying on the morphological replacement of a concept prototype-leaf's 3D architecture into perovskite titanates for CO2 photoreduction into hydrocarbon fuels (CO and CH4). The process uses artificial sunlight as the energy source, water as an electron donor and CO2 as the carbon source, mimicking what real leaves do. To our knowledge this is the first example utilizing biological systems as “architecture-directing agents” for APS towards CO2 photoreduction, which hints at a more general principle for APS architectures with a great variety of optimized biological geometries. This research would have great significance for the potential realization of global carbon neutral cycle. PMID:23588925

  6. Comparison of vitamin D deficiency and magnitude of severity of vitamin D deficiency in cirrhotic and non-cirrhotic patients with chronic hepatitis C in a tertiary care hospital Rawalpindi, Pakistan

    International Nuclear Information System (INIS)

    Hamid, S.; Faheem, M.; Ambreen, S.; Tirmizi, A.; Umar, M.

    2017-01-01

    Objective: To determine Vitamin D deficiency in both cirrhotic and non-cirrhotic patients with chronic hepatitis C (CHC). Methodology: We conducted a cross-sectional study at Centre for Liver and Digestive Diseases (CLD), Holy Family Hospital, Rawalpindi, Pakistan from August 2015 to February 2016 and included 120 Patients with CHC with or without cirrhosis. Two groups were formed and vitamin D levels were measured and level of severity was assessed. Results: Out of 120 patients, 94(78.3%) patients had Vitamin D deficiency. 63(100%) cirrhotic patients and 31 54.4%) non cirrhotic patients had Vitamin D deficiency. In cirrhotic patients, 26(41.3%) had mild and 36(58.7%) had moderate Vitamin D deficiency while in non-cirrhotic patients 25(43.9%) had mild and 6(10.5%) had moderate deficiency. No patient with severe Vitamin D deficiency was observed. Conclusion: Most of the patients infected with CHC suffer from vitamin D deficiency. This was observed more in cirrhotic patients than non-cirrhotic patients. Moreover, positive correlation was observed among vitamin D deficiency and stage of fibrosis. (author)

  7. Structural chemistry and magnetic properties of the perovskite Sr{sub 3}Fe{sub 2}TeO{sub 9}

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Yawei; Hunter, Emily C. [Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom); Battle, Peter D., E-mail: peter.battle@chem.ox.ac.uk [Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom); Sena, Robert Paria; Hadermann, Joke [EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium); Avdeev, Maxim [Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234 (Australia); Cadogan, J.M. [School of Physical, Environmental and Mathematical Sciences, UNSW Canberra at the Australian Defence Force Academy, Canberra BC 2610 (Australia)

    2016-10-15

    A polycrystalline sample of perovskite-like Sr{sub 3}Fe{sub 2}TeO{sub 9} has been prepared in a solid-state reaction and studied by a combination of electron microscopy, Mössbauer spectroscopy, magnetometry, X-ray diffraction and neutron diffraction. The majority of the reaction product is shown to be a trigonal phase with a 2:1 ordered arrangement of Fe{sup 3+} and Te{sup 6+} cations. However, the sample is prone to nano-twinning and tetragonal domains with a different pattern of cation ordering exist within many crystallites. Antiferromagnetic ordering exists in the trigonal phase at 300 K and Sr{sub 3}Fe{sub 2}TeO{sub 9} is thus the first example of a perovskite with 2:1 trigonal cation ordering to show long-range magnetic order. At 300 K the antiferromagnetic phase coexists with two paramagnetic phases which show spin-glass behaviour below ~80 K. - Graphical abstract: Sr{sub 3}Fe{sub 2}TeO{sub 9} has a 2:1 ordered arrangement of Fe{sup 3+} and Te{sup 6+} cations over the octahedral sites of a perovskite structure and is antiferromagnetic at room temperature. - Highlights: • 2:1 Cation ordering in a trigonal perovskite. • Magnetically ordered trigonal perovskite. • Intergrowth of nanodomains in perovskite microstructure.

  8. The Recombination Mechanism and True Green Amplified Spontaneous Emission in CH3NH3PbBr3 Perovskite

    KAUST Repository

    Priante, Davide

    2015-08-01

    when optically pumped using 475 nm laser pulses, thus supporting the assignment of carrier absorption and re-excitation mentioned above. This dissertation work led to the following article: D. Priante, I. Dursun, M. S. Alias, D. Shi, V. A. Melnikov, T. K. Ng, O. F. Mohammed, O. M. Bakr, and B. S. Ooi, "The recombination mechanisms leading to amplified spontaneous emission at the true-green wavelength in CH3NH3PbBr3 perovskites", Applied Physics Letters, 106, 081902, 2015. DOI: 10.1063/1.4913463

  9. Synthesis and structural study of the transition metal doped rhodium perovskites

    International Nuclear Information System (INIS)

    Ting, J.; Kennedy, B.; Zhang, Z.

    2009-01-01

    Full text: One of the most common structures encountered in solid state chemistry is the perovskite structure. With a general formula of AB0 3, the A-type cations are 12-coordinate within a cubo-octahedral environment, while the B-type cations are 6-coordinate, forming an interconnecting three-dimensional octahedral network with neighbouring oxygen anions. While the ideal perovskite structure is cubic in Pm 3 m, many perovskites exhibit symmetry lowering tilting of the corner-sharing B0 6o ctahedral units as a result of A- and B-type cation size disparity. This is also evident in substituted perovskites, where two cations occupy the smaller octahedral site, AB 1- xB' x0 3' Electronic effects can also lower the symmetry. The two most commonly observed effects are the polarisation of the B-cation with a d 0 electronic configuration and Jahn-Teller distortion where the B-cation has a d 4 or d 9 electronic configuration, such as Mn 3+ or Cu 2+ respectively. Manganese containing perovskites have been shown in some compounds to exhibit long-range orbital ordering, giving rise to interesting properties. Heavier transition metals such as ruthenium and iridium have been previously incorporated into these perovskites as an avenue to regulate the properties of these materials. Two orthorhombic rhodium perovskite structures are presented, LaMn 0 . 5 Rh 0 . 5 O 3 and LaCu 05 Rh 0 . 5 O 3 ' A combination of synchrotron x-ray and neutron powder diffraction has been used to elucidate their structures, and have shown both B- and B'-type cations to be disordered across the same crystallographic site for both compounds. x-ray absorption spectroscopy measurements have been used to provide an insight into the valence states of the cations, which show a valency of +3.5 for rhodium due to an extensive charge delocalisation between copper and rhodium.

  10. Broadband-Emitting 2 D Hybrid Organic-Inorganic Perovskite Based on Cyclohexane-bis(methylamonium) Cation.

    Science.gov (United States)

    Neogi, Ishita; Bruno, Annalisa; Bahulayan, Damodaran; Goh, Teck Wee; Ghosh, Biplab; Ganguly, Rakesh; Cortecchia, Daniele; Sum, Tze Chien; Soci, Cesare; Mathews, Nripan; Mhaisalkar, Subodh Gautam

    2017-10-09

    A new broadband-emitting 2 D hybrid organic-inorganic perovskite (CyBMA)PbBr 4 based on highly flexible cis-1,3-bis(methylaminohydrobromide)cyclohexane (CyBMABr) core has been designed, synthesized, and investigated, highlighting the effects of stereoisomerism of the templating cation on the formation and properties of the resulting perovskite. The new 2 D material has high exciton binding energy of 340 meV and a broad emission spanning from 380 to 750 nm, incorporating a prominent excitonic band and a less intense broad peak at room temperature. Significant changes in the photoluminescence (PL) spectrum were observed at lower temperatures, showing remarkable enhancement in the intensity of the broadband at the cost of excitonic emission. Temperature-dependent PL mapping indicates the effective role of only a narrow band of excitonic absorption in the generation of the active channel for emission. Based on the evidences obtained from the photophysical investigations, we attributed the evolution of the broad B-band of (CyBMA)PbBr 4 to excitonic self-trapped states. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Tailoring the Energy Landscape in Quasi-2D Halide Perovskites Enables Efficient Green-Light Emission

    KAUST Repository

    Quan, Li Na; Zhao, Yongbiao; Garcí a de Arquer, F. Pelayo; Sabatini, Randy; Walters, Grant; Voznyy, Oleksandr; Comin, Riccardo; Li, Yiying; Fan, James Z.; Tan, Hairen; Pan, Jun; Yuan, Mingjian; Bakr, Osman; Lu, Zhenghong; Kim, Dong Ha; Sargent, Edward H.

    2017-01-01

    Organo-metal halide perovskites are a promising platform for optoelectronic applications in view of their excellent charge-transport and bandgap tunability. However, their low photoluminescence quantum efficiencies, especially in low-excitation regimes, limit their efficiency for light emission. Consequently, perovskite light-emitting devices are operated under high injection, a regime under which the materials have so far been unstable. Here we show that, by concentrating photoexcited states into a small subpopulation of radiative domains, one can achieve a high quantum yield, even at low excitation intensities. We tailor the composition of quasi-2D perovskites to direct the energy transfer into the lowest-bandgap minority phase and to do so faster than it is lost to nonradiative centers. The new material exhibits 60% photoluminescence quantum yield at excitation intensities as low as 1.8 mW/cm2, yielding a ratio of quantum yield to excitation intensity of 0.3 cm2/mW; this represents a decrease of 2 orders of magnitude in the excitation power required to reach high efficiency compared with the best prior reports. Using this strategy, we report light-emitting diodes with external quantum efficiencies of 7.4% and a high luminescence of 8400 cd/m2.

  12. Tailoring the Energy Landscape in Quasi-2D Halide Perovskites Enables Efficient Green-Light Emission

    KAUST Repository

    Quan, Li Na

    2017-05-10

    Organo-metal halide perovskites are a promising platform for optoelectronic applications in view of their excellent charge-transport and bandgap tunability. However, their low photoluminescence quantum efficiencies, especially in low-excitation regimes, limit their efficiency for light emission. Consequently, perovskite light-emitting devices are operated under high injection, a regime under which the materials have so far been unstable. Here we show that, by concentrating photoexcited states into a small subpopulation of radiative domains, one can achieve a high quantum yield, even at low excitation intensities. We tailor the composition of quasi-2D perovskites to direct the energy transfer into the lowest-bandgap minority phase and to do so faster than it is lost to nonradiative centers. The new material exhibits 60% photoluminescence quantum yield at excitation intensities as low as 1.8 mW/cm2, yielding a ratio of quantum yield to excitation intensity of 0.3 cm2/mW; this represents a decrease of 2 orders of magnitude in the excitation power required to reach high efficiency compared with the best prior reports. Using this strategy, we report light-emitting diodes with external quantum efficiencies of 7.4% and a high luminescence of 8400 cd/m2.

  13. Developmental Vitamin D (DVD) Deficiency Reduces Nurr1 and TH Expression in Post-mitotic Dopamine Neurons in Rat Mesencephalon.

    Science.gov (United States)

    Luan, Wei; Hammond, Luke Alexander; Cotter, Edmund; Osborne, Geoffrey William; Alexander, Suzanne Adele; Nink, Virginia; Cui, Xiaoying; Eyles, Darryl Walter

    2018-03-01

    Developmental vitamin D (DVD) deficiency has been proposed as an important risk factor for schizophrenia. Our previous study using Sprague Dawley rats found that DVD deficiency disrupted the ontogeny of mesencephalic dopamine neurons by decreasing the mRNA level of a crucial differentiation factor of dopamine cells, the nuclear receptor related 1 protein (Nurr1). However, it remains unknown whether this reflects a reduction in dopamine cell number or in Nurr1 expression. It is also unclear if any particular subset of developing dopamine neurons in the mesencephalon is selectively affected. In this study, we employed state-of-the-art spinning disk confocal microscopy optimized for the imaging of tissue sections and 3D segmentation to assess post-mitotic dopamine cells on a single-cell basis in the rat mesencephalon at embryonic day 15. Our results showed that DVD deficiency did not alter the number, morphology, or positioning of post-mitotic dopamine cells. However, the ratio of Nurr1+TH+ cells in the substantia nigra pars compacta (SNc) compared with the ventral tegmental area (VTA) was increased in DVD-deficient embryos. In addition, the expression of Nurr1 in immature dopamine cells and mature dopamine neurons in the VTA was decreased in DVD-deficient group. Tyrosine hydroxylase was selectively reduced in SNc of DVD-deficient mesencephalon. We conclude that DVD deficiency induced early alterations in mesencephalic dopamine development may in part explain the abnormal dopamine-related behaviors found in this model. Our findings may have broader implications for how certain environmental risk factors for schizophrenia may shape the ontogeny of dopaminergic systems and by inference increase the risk of schizophrenia.

  14. Highly Emissive Divalent-Ion-Doped Colloidal CsPb1–xMxBr3 Perovskite Nanocrystals through Cation Exchange

    Science.gov (United States)

    2017-01-01

    Colloidal CsPbX3 (X = Br, Cl, and I) perovskite nanocrystals (NCs) have emerged as promising phosphors and solar cell materials due to their remarkable optoelectronic properties. These properties can be tailored by not only controlling the size and shape of the NCs but also postsynthetic composition tuning through topotactic anion exchange. In contrast, property control by cation exchange is still underdeveloped for colloidal CsPbX3 NCs. Here, we present a method that allows partial cation exchange in colloidal CsPbBr3 NCs, whereby Pb2+ is exchanged for several isovalent cations, resulting in doped CsPb1–xMxBr3 NCs (M= Sn2+, Cd2+, and Zn2+; 0 50%), sharp absorption features, and narrow emission of the parent CsPbBr3 NCs. The blue-shift in the optical spectra is attributed to the lattice contraction that accompanies the Pb2+ for M2+ cation exchange and is observed to scale linearly with the lattice contraction. This work opens up new possibilities to engineer the properties of halide perovskite NCs, which to date are demonstrated to be the only known system where cation and anion exchange reactions can be sequentially combined while preserving the original NC shape, resulting in compositionally diverse perovskite NCs. PMID:28260380

  15. Role of the chemical substitution on the structural and luminescence properties of the mixed halide perovskite thin MAPbI_3_−_xBr_x (0 ≤ x ≤ 1) films

    International Nuclear Information System (INIS)

    Atourki, Lahoucine; Vega, Erika; Marí, Bernabé; Mollar, Miguel; Ait Ahsaine, Hassan; Bouabid, Khalid; Ihlal, Ahmed

    2016-01-01

    Highlights: • X-ray diffraction analyses indicate the formation of a tetragonal phase I4/mcm up to x = 0.4 and a cubic perovskite with space group Pm3 m across in the composition range of 0.6 ≤ x ≤ 1. • Perovskite films exhibit a very high absorbance in the visible and short infrared. • As the fraction of bromide change, the adsorption edge of thin film perovskite can be tuned along the visible spectrum from 543 nm to 785 nm. • The incorporating of bromide into MAPbI_3_−_xBr_x shifts the PL emission to shorter wavelengths. - Abstract: Mixed bromide iodide lead perovskites were prepared from methylamine, lead nitrate and the corresponding hydroX acid (X = I, Br), they were then deposited as thin films on ITO substrate by the spin coating process. X-ray diffraction analyses indicated the formation of a tetragonal phase I4/mcm up to x = 0.4 and a cubic perovskite with space group Pm3 m in the composition range of 0.6 ≤ x ≤ 1. Mixed lead perovskites showed a high absorbance in the UV–vis range. The band gap energy of thin films were estimated from absorbance spectral measurements, it was found that the onset of the absorption edge for MAPbI_3_−_xBr_x (x < 1) thin films is ranging between 1.58 to 1.72 eV. Photoluminescence emission energies for mixed halide perovskites presented intermediate values from 781 nm (MAPbI_3) to 545 nm (MAPbBr_3).

  16. Sn2+—Stabilization in MASnI3 perovskites by superhalide incorporation

    Science.gov (United States)

    Xiang, Junxiang; Wang, Kan; Xiang, Bin; Cui, Xudong

    2018-03-01

    Sn-based hybrid halide perovskites are a potential solution to replace Pb and thereby reduce Pb toxicity in MAPbI3 perovskite-based solar cells. However, the instability of Sn2+ in air atmosphere causes a poor reproducibility of MASnI3, hindering steps towards this goal. In this paper, we propose a new type of organic metal-superhalide perovskite of MASnI2BH4 and MASnI2AlH4. Through first-principles calculations, our results reveal that the incorporation of BH4 and AlH4 superhalides can realize an impressive enhancement of oxidation resistance of Sn2+ in MASnI3 perovskites because of the large electron transfer between Sn2+ and [BH4]-/[AlH4]-. Meanwhile, the high carrier mobility is preserved in these superhalide perovskites and only a slight decrease is observed in the optical absorption strength. Our studies provide a new path to attain highly stable performance and reproducibility of Sn-based perovskite solar cells.

  17. CHST14/D4ST1 deficiency: New form of Ehlers-Danlos syndrome.

    Science.gov (United States)

    Kosho, Tomoki

    2016-02-01

    Carbohydrate sulfotransferase 14/dermatan 4-O-sulfotransferase-1 (CHST14/D4ST1) deficiency represents a specific form of Ehlers-Danlos syndrome (EDS) caused by recessive loss-of-function mutations in CHST14. The disorder has been independently termed "adducted thumb-clubfoot syndrome", "EDS, Kosho type", and "EDS, musculocontractural type". To date, 31 affected patients from 21 families have been described. Clinically, CHST14/D4ST1 deficiency is characterized by multiple congenital malformations (craniofacial features including large fontanelle, hypertelorism, short and downslanting palpebral fissures, blue sclerae, short nose with hypoplastic columella, low-set and rotated ears, high palate, long philtrum, thin upper lip vermilion, small mouth, and micro-retrognathia; multiple congenital contractures including adduction-flexion contractures and talipes equinovarus as well as other visceral or ophthalmological malformations) and progressive multisystem fragility-related complications (skin hyperextensibility, bruisability, and fragility with atrophic scars; recurrent dislocations; progressive talipes or spinal deformities; pneumothorax or pneumohemothorax; large subcutaneous hematomas; and diverticular perforation). Etiologically, multisystem fragility is presumably caused by impaired assembly of collagen fibrils resulting from loss of dermatan sulfate (DS) in the decorin glycosaminoglycan side chain that promotes electrostatic binding between collagen fibrils. This is the first reported human disorder that specifically affects biosynthesis of DS. Its clinical characteristics indicate that CHST14/D4ST1 and, more fundamentally, DS, play a critical role in fetal development and maintenance of connective tissues in multiple organs. Considering that patients with CHST14/D4ST1 deficiency develop progressive multisystem fragility-related manifestations, establishment of a comprehensive and detailed natural history and health-care guidelines as well as further elucidation

  18. Vitamin D deficiency among northern Native Peoples: a real or apparent problem?

    Directory of Open Access Journals (Sweden)

    Peter Frost

    2012-03-01

    Full Text Available Vitamin D deficiency seems to be common among northern Native peoples, notably Inuit and Amerindians. It has usually been attributed to: (1 higher latitudes that prevent vitamin D synthesis most of the year; (2 darker skin that blocks solar UVB; and (3 fewer dietary sources of vitamin D. Although vitamin D levels are clearly lower among northern Natives, it is less clear that these lower levels indicate a deficiency. The above factors predate European contact, yet pre-Columbian skeletons show few signs of rickets—the most visible sign of vitamin D deficiency. Furthermore, because northern Natives have long inhabited high latitudes, natural selection should have progressively reduced their vitamin D requirements. There is in fact evidence that the Inuit have compensated for decreased production of vitamin D through increased conversion to its most active form and through receptors that bind more effectively. Thus, when diagnosing vitamin D deficiency in these populations, we should not use norms that were originally developed for European-descended populations who produce this vitamin more easily and have adapted accordingly.

  19. Multiferroic Double Perovskites ScFe1-xCrxO3 (1 /6 ≤x ≤5 /6 ) for Highly Efficient Photovoltaics and Spintronics

    Science.gov (United States)

    Cai, Tian-Yi; Liu, Shi-Chen; Ju, Sheng; Liu, Cheng-You; Guo, Guang-Yu

    2017-09-01

    Ferroelectric oxides are attractive materials for constructing efficient solar cells. Nevertheless, a wide band gap of nearly 3.0 eV in these ferroelectric oxides would result in poor overall sunlight absorption and, hence, low energy conversion efficiency. Here, by systematic first-principles density-functional calculations, we demonstrate that double-perovskite semiconductors ScFe1-xCrxO3 (1 /6 ≤x ≤5 /6 ) with a narrow band gap of approximately 1.8 eV would simultaneously exhibit large ferroelectric polarization (100 μ C /cm2 ) and ferrimagnetic magnetization (170 emu/cm3 ). Within a Schottky-based model for a typical sandwich solar-cell structure, a power-conversion efficiency of 9.0% can be reached by neglecting all other sources of photovoltaicity in ferroelectric materials. This value is larger than the largest value of 8.1% observed in ferroelectric oxides. Furthermore, these double perovskites are found to be single-spin semiconductors, and the obtained photocurrent is fully spin polarized over almost the entire Sun spectrum. These fascinating advantages would make ScFex Cr1 -xO3 (1 /6 ≤x ≤5 /6 ) semiconductors promising candidates for highly efficient solar cells and spin photovoltaic devices.

  20. Organic-inorganic perovskites containing trivalent metal halide layers: the templating influence of the organic cation layer.

    Science.gov (United States)

    Mitzi, D B

    2000-12-25

    Thin sheetlike crystals of the metal-deficient perovskites (H2AEQT)M2/3I4 [M = Bi or Sb; AEQT = 5,5"'-bis-(aminoethyl)-2,2':5',2'':5'',2'''-quaterthiophene] were formed from slowly cooled ethylene glycol/2-butanol solutions containing the bismuth(III) or antimony(III) iodide and AEQT.2HI salts. Each structure was refined in a monoclinic (C2/m) subcell, with the lattice parameters a = 39.712(13) A, b = 5.976(2) A, c = 6.043(2) A, beta = 92.238(5) degrees, and Z = 2 for M = Bi and a = 39.439(7) A, b = 5.952(1) A, c = 6.031(1) A, beta = 92.245(3) degrees, and Z = 2 for M = Sb. The trivalent metal cations locally adopt a distorted octahedral coordination, with M-I bond lengths ranging from 3.046(1) to 3.218(3) A (3.114 A average) for M = Bi and 3.012(1) to 3.153(2) A (3.073 A average) for M = Sb. The new organic-inorganic hybrids are the first members of a metal-deficient perovskite family consisting of (Mn+)2/nV(n-2)/nX4(2-) sheets, where V represents a vacancy (generally left out of the formula) and the metal cation valence, n, is greater than 2. The organic layers in the AEQT-based organic-inorganic hybrids feature edge-to-face aromatic interactions among the rigid, rodlike quaterthiophene moieties, which may help to stabilize the unusual metal-deficient layered structures.

  1. Glycemic changes after vitamin D supplementation in patients with type 1 diabetes mellitus and vitamin D deficiency

    International Nuclear Information System (INIS)

    Khalid S Aljabri; Somoa A Bokhari; Murtadha J. Khan

    2010-01-01

    A prospective, nonblinded and nonrandomized controlled trial was conducted to test the hypothesis that vitamin D supplementation would improve glycemic control in patients with type 1 diabetes mellitus who have vitamin D deficiency. Patients and 0 Eighty patients with type 1 diabetes mellitus who had 25-hydroxyvitamin D levels less than 50 nmol/L were assigned to receive 4000 IU of vitamin D3. Calcium supplements were provided to ensure a total calcium intake of 1200 mg/d. Glycosylated hemoglobin and 25-hydroxyvitamin D levels were measured at baseline and at 12 weeks.There was a significant difference in mean (SD) glycosylated hemoglobin level (%) between the groups that achieved 25-hydroxyvitamin D levels of 51 nmol/L at 12 weeks (P=.02). There was a significant difference in glycosylated hemoglobin change from baseline between the groups that achieved 25-hydroxyvitamin D levels of 51 nmol/L at 12 weeks (P=.04). There was a significant difference in 25-hydroxyvitamin D level between the groups that achieved glycosylated hemoglobin levels of 9.9 at 12 weeks (P=.001). Patients were more likely to achieve lower glycosylated hemoglobin levels at 12 weeks if they had higher 25-hydroxyvitamin D levels at 12 weeks (r=-0.4, P=.001).There was an observed effect of vitamin D supplementation on glycemic control in vitamin D-replete, type 1 diabetes mellitus patients. Further studies are needed to determine if these findings are applicable (Author).

  2. Role of bromine doping on the photovoltaic properties and microstructures of CH3NH3PbI3 perovskite solar cells

    International Nuclear Information System (INIS)

    Suzuki, Atsushi; Okada, Hiroshi; Oku, Takeo

    2016-01-01

    Organic-inorganic hybrid heterojunction solar cells containing CH 3 NH 3 PbI 3 perovskite compound were fabricated using mesoporous TiO 2 as the electronic transporting layer and spirobifluorence as the hole-transporting layer. The purpose of the present study is to investigate role of bromine (Br) doping on the photovoltaic properties and microstructure of CH 3 NH 3 PbI 3 perovskite solar cells. Photovoltaic, optical properties and microstructures of perovskite-based solar cells were investigated. The X-ray diffraction identified crystal structure of the perovskite layer doped with Br in the solar cell. Scanning electron microscopy observation showed a different behavior of surface morphology and the perovskite crystal structure on the TiO 2 mesoporous structure depending on extent amount of hydrogen doping of Br. The role of bromide halogen doping on the perovskite crystal structure and photovoltaic properties was due to improvement of carrier mobility, optimization of electron structure, band gap related with the photovoltaic parameters of V oc , J sc and η. Energy diagram and photovoltaic mechanism of the perovskite solar cells varied with halogen doping was discussed by experimental results

  3. An efficient synthesis of 1α,25-dihydroxyvitamin D3 LC-biotin.

    Science.gov (United States)

    Kattner, Lars; Bernardi, Dan

    2017-10-01

    In recent years the apparent impact of vitamin D deficiency on human health has gained increased awareness. Consequently, the development of appropriate assays to measure the status of medicinally most relevant vitamin D metabolites in human blood, serum or relevant tissue is continuously being improved. Particularly, assaying of 1α,25-dihydroxyvitamin D 3 , in turn considered as the most active metabolite, is mainly indicated in disorders leading to calcaemia or those resulting from an impaired 1α-hydroxylation of 25-hydroxyvitamin D 3 . Thus, in some competitive protein binding and ELISA assays, biotin-linked 1α,25-dihydroxyvitamin D 3 (1α,25-dihydroxyvitamin D 3 LC-biotin) is employed for measurement of actual calicitriol concentration. A new efficient synthesis of 1α,25-dihydroxyvitamin D 3 LC-biotin is described, starting with readily available vitamin D 2 , and combining a classical approach to access 1α,25-dihydroxyvitamin D 3 , appropriate OH-protective group transformations, and a C-3-O-alkylation, suitable to connect the biotin-linker in a reliable, selective and high yielding strategy. The developed methodology is applicable to the synthesis of a wide variety of C-3-OH-linked vitamin D 3 and D 2 derivatives. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Rationale and Design of Khuzestan Vitamin D Deficiency Screening Program in Pregnancy: A Stratified Randomized Vitamin D Supplementation Controlled Trial.

    Science.gov (United States)

    Rostami, Maryam; Ramezani Tehrani, Fahimeh; Simbar, Masoumeh; Hosseinpanah, Farhad; Alavi Majd, Hamid

    2017-04-07

    Although there have been marked improvements in our understanding of vitamin D functions in different diseases, gaps on its role during pregnancy remain. Due to the lack of consensus on the most accurate marker of vitamin D deficiency during pregnancy and the optimal level of 25-hydroxyvitamin D, 25(OH)D, for its definition, vitamin D deficiency assessment during pregnancy is a complicated process. Besides, the optimal protocol for treatment of hypovitaminosis D and its effect on maternal and neonatal outcomes are still unclear. The aim of our study was to estimate the prevalence of vitamin D deficiency in the first trimester of pregnancy and to compare vitamin D screening strategy with no screening. Also, we intended to compare the effectiveness of various treatment regimens on maternal and neonatal outcomes in Masjed-Soleyman and Shushtar cities of Khuzestan province, Iran. This was a two-phase study. First, a population-based cross-sectional study was conducted; recruiting 1600 and 900 first trimester pregnant women from health centers of Masjed-Soleyman and Shushtar, respectively, using stratified multistage cluster sampling with probability proportional to size (PPS) method. Second, to assess the effect of screening strategy on maternal and neonatal outcomes, Masjed-Soleyman participants were assigned to a screening program versus Shushtar participants who became the nonscreening arm. Within the framework of the screening regimen, an 8-arm blind randomized clinical trial was undertaken to compare the effects of various treatment protocols. A total of 800 pregnant women with vitamin D deficiency were selected using simple random sampling from the 1600 individuals of Masjed-Soleyman as interventional groups. Serum concentrations of 25(OH)D were classified as: (1) severe deficient (20ng/ml). Those with severe and moderate deficiency were randomly divided into 4 subgroups and received vitamin D3 based on protocol and were followed until delivery. Data was analyzed

  5. Vitamin D deficiency is associated with urinary tract infection in children.

    Science.gov (United States)

    Shalaby, Sherein Abdelhamid; Handoka, Nesrein Mosad; Amin, Rasha Emad

    2018-01-01

    In humans, vitamin D has been shown to play a role in infectious diseases, but its association with acquisition and a complicated course of febrile urinary tract infections (UTIs) has not been investigated. We aimed to investigate the association between 25-hydroxyvitamin D (25(OH)D 3 ) levels and the risk of first time febrile UTI in children. This prospective case-control study included 50 children with first febrile UTI, with no risk factors for UTI, and 50 age- and sex-matched healthy siblings as controls. White blood cell count, serum C-reactive protein, calcium, phosphorus, alkaline phosphatase and parathormone were measured in all studied children. Vitamin D status was determined by measuring plasma 25(OH)D 3 level. Deficiency was defined as a plasma 25(OH)D 3 level ≤ 25 nmol/l. Children with UTI had significantly lower mean serum levels of 25(OH)D 3 (10.5 ±2.7 nmol/l) than those of controls (25.9 ±5.6 nmol/l) ( p UTI had significantly higher serum levels of 25(OH)D 3 compared to those with acute pyelonephritis (12.4 ±2.59 vs. 8.2 ±3.2 nmol/l; p UTI (OR = 1.94, 95% CI: 1.61-2.82; p = 0.04). Vitamin D deficiency (≤ 25 nmol/l) was an independent risk factor for UTI in children.

  6. Influence of iridium on the reactivity of LaFeO3 base perovskites

    DEFF Research Database (Denmark)

    Kindermann, L.; Das, D.; Bahadur, D.

    1998-01-01

    The influence of iridium on the reactivity of powder mixtures made of perovskites and 8 mol% yttria stabilized zirconia (8 YSZ) is reported. Iridium is added to the perovskites of the composition (La0.6M0.4)(z)Fe0.8TM0.2O3-delta (M = Sr, Ca; TM = Mn, Co; z = 0.90, 1.00) via the gaseous phase....... Iridium is present in the perovskite lattice as Ir4+ replacing iron as is evident from XRD and TEM/EDX results. Compatibility studies carried out at 1000 degrees C demonstrate that iridium has considerable influence on the reactivity. The results are discussed with respect to the stability...... of the perovskites, thermodynamic activities, Ir(IV)-O bonding, tolerance factor and oxygen migration....

  7. Evidence for a different electronic configuration as a primary effect during compression of orthorhombic perovskites: The case of Nd M3 +O3 (M =Cr ,Ga )

    Science.gov (United States)

    Ardit, M.; Dondi, M.; Merli, M.; Cruciani, G.

    2018-02-01

    (Mg ,Fe ) Si O3 perovskite is the most abundant mineral of the Earth's lower mantle, and compounds with the perovskite structure are perhaps the most widely employed ceramics. Hence, they attract both geophysicists and material scientists. Several investigations attempted to predict their structural evolution at high pressure, and recent advancements highlighted that perovskites having ions with the same formal valence at both polyhedral sites (i.e., 3 +:3 + ) define different compressional patterns when transition metal ions (TMI) are involved. In this study, in situ high-pressure synchrotron XRD measurements coupled with ab initio simulations of the electronic population of NdCr O3 perovskite are compared with the compressional feature of NdGa O3 . Almost identical from a steric point of view (C r3 + and G a3 + have almost the same ionic radius), the different electronic configuration of octahedrally coordinated ions - which leads to a redistribution of electrons at the 3 d orbitals for C r3 + - allows the crystal field stabilization energy (CFSE) to act as a vehicle of octahedral softening in NdCr O3 or it turns octahedra into rigid units when CFSE is null as in NdGa O3 . Besides to highlight that different electronic configurations can act as a primary effect during compression of perovskite compounds, our findings have a deep repercussion on the way the compressibility of perovskites have to be modeled.

  8. The Recombination Mechanism and True Green Amplified Spontaneous Emission in CH3NH3PbBr3 Perovskite

    KAUST Repository

    Priante, Davide

    2015-01-01

    . M. Bakr, and B. S. Ooi, "The recombination mechanisms leading to amplified spontaneous emission at the true-green wavelength in CH3NH3PbBr3 perovskites", Applied Physics Letters, 106, 081902, 2015. DOI: 10.1063/1.4913463

  9. Investigation on the structural, magnetic and magnetocaloric properties of nanocrystalline Pr-deficient Pr1-xSrxMnO3-δ manganites

    Science.gov (United States)

    Arun, B.; Athira, M.; Akshay, V. R.; Sudakshina, B.; Mutta, Geeta R.; Vasundhara, M.

    2018-02-01

    We have investigated the structural, magnetic and magnetocaloric properties of nanocrystalline Pr-deficient Pr1-xSrxMnO3Perovskite manganites. Rietveld refinement of the X-ray powder diffraction patterns confirms that all the studied compounds have crystallized into an orthorhombic structure with Pbnm space group. Transmission electron microscopy analysis reveals nanocrystalline compounds with crystallite size less than 50 nm. The selected area electron diffraction patterns reveal the highly crystalline nature of the compounds and energy dispersive X-ray spectroscopic analysis shows that the obtained compositions are nearly identical with the nominal one. The oxygen stoichiometry is estimated by iodometric titration method and stoichiometric compositions are confirmed by X-ray Fluorescence Spectrometry analysis. A large bifurcation is observed in the ZFC/FC curves and Arrott plots not show a linear relation but have a convex curvature nature. The temperature dependence of inverse magnetic susceptibility at higher temperature confirms the existence of ferromagnetic clusters. The experimental results reveal that the reduction of crystallite size to nano metric scale in Pr-deficient manganites adversely influences structural, magnetic and magnetocaloric properties as compared to its bulk counterparts reported earlier.

  10. Excitonic and Polaronic Properties of 2D Hybrid Organic–Inorganic Perovskites

    KAUST Repository

    Yin, Jun; Li, Hong; Cortecchia, Daniele; Soci, Cesare; Bredas, Jean-Luc

    2017-01-01

    calculations including corrections due to spin orbit couplings and electron hole interactions, a computationally intensive molecular cluster approach is exploited to describe the excitonic and polaronic properties of these 2D perovskites at the atomistic level

  11. Stability Issues on Perovskite Solar Cells

    Directory of Open Access Journals (Sweden)

    Xing Zhao

    2015-11-01

    Full Text Available Organo lead halide perovskite materials like methylammonium lead iodide (CH3NH3PbI3 and formamidinium lead iodide (HC(NH22PbI3 show superb opto-electronic properties. Based on these perovskite light absorbers, power conversion efficiencies of the perovskite solar cells employing hole transporting layers have increased from 9.7% to 20.1% within just three years. Thus, it is apparent that perovskite solar cell is a promising next generation photovoltaic technology. However, the unstable nature of perovskite was observed when exposing it to continuous illumination, moisture and high temperature, impeding the commercial development in the long run and thus becoming the main issue that needs to be solved urgently. Here, we discuss the factors affecting instability of perovskite and give some perspectives about further enhancement of stability of perovskite solar cell.

  12. New dielectric material systems of Sr{sub x}Nd{sub 2(1}–{sub x)/3}TiO{sub 3} perovskites-like at microwave frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Qu, Jingjing [Department of Information Engineering, Guilin University of Aerospace Technology, Guilin 541004 (China); Liu, Fei, E-mail: liufeiguet@163.com [College of Material Science and Engineering, Central South University, Changsha 410083 (China); College of Material Science and Engineering, Guilin University of Electronic Technology, Guilin 541004 (China); Wei, Xing [Department of Information Engineering, Guilin University of Aerospace Technology, Guilin 541004 (China); Yuan, Changlai [College of Material Science and Engineering, Guilin University of Electronic Technology, Guilin 541004 (China); Liu, Xinyu [College of Material Science and Engineering, Central South University, Changsha 410083 (China); College of Material Science and Engineering, Guilin University of Electronic Technology, Guilin 541004 (China); Huang, Xianpei [College of Material Science and Engineering, Guilin University of Electronic Technology, Guilin 541004 (China); Liu, Xiao [College of Material Science and Engineering, Central South University, Changsha 410083 (China); College of Material Science and Engineering, Guilin University of Electronic Technology, Guilin 541004 (China)

    2016-04-15

    Perovskite compounds, Sr{sub x}Nd{sub 2(1−x)/3}TiO{sub 3} (SNTx) with x ranging from 0.05 to 0.2, were prepared by the conventional solid–state reaction method. X-ray diffraction patterns illustrated that high density and single phase products were obtained for all samples, indicating that a small level of Sr addition could substantially stabilise the structure and maintain a single phase for Nd{sub 2/3}TiO{sub 3} ceramics. But there was also an orthorhombic space groups transition from Pnma to P4/mmm when x was above 0.18. In addition, the dielectric constant (ε{sub r}) of SNTx ceramics had improved from ∼85.6 to ∼112 with increasing x value due to the larger ionic polarizability of Sr{sup 2+} than that of Nd{sup 3+}. Notably, the product of dielectric Q value and resonant frequency (Q × f) of ∼295–650 at 3.07–3.32 GHz was strongly dependent on the grain size and the cation deficient in the present systems. Either increasing grain size or decreasing A-site vacancies led to an increase in the Q × f value. Besides, a temperature coefficient of resonant frequency (τ{sub f}) of the SNTx ceramics sintered at their optimum densification temperature gradually increases from 191.7 ppm/°C (x = 0.05) to 221.3 ppm/°C (x = 0.2), which results from the lower rattling effect and higher symmetry in BO{sub 6} octahedra of perovskite structure according to bond valence theory and tolerance factor (t). - Highlights: • A small level of Sr addition could stabilise the structure for Nd{sub 2/3}TiO{sub 3} ceramics. • The rattling effect of BO{sub 6} octahedra increases with decreasing B-site bond valence. • There was an orthorhombic space groups transition from Pnma to P4/mmm. • Homogeneous grain size and decreasing A-site vacancies led to an increase in Q × f.

  13. Magnetism in ordered metallic perovskite compound GdPd3BxC1-x

    International Nuclear Information System (INIS)

    Pandey, Abhishek; Mazumdar, Chandan; Ranganathan, R.; Dattagupta, S.

    2009-01-01

    We report results of dc-magnetization, ac-susceptibility and magnetoresistance measurements on crystalline metallic-perovskite compounds GdPd 3 B x C 1-x (x=0.25, 0.50, 0.75 and 1.00) and the parent cubic compound GdPd 3 . The interest in these materials stems from the observation of negative temperature coefficient of resistance and negative thermal expansion in some of the members of this series. In the present study, we show that by substitution of non-magnetic elements, boron and carbon, the nature of the magnetic interaction can be varied from dominating ferromagnetic to antiferromagnetic and finally to a canted magnetic structure without altering the crystal symmetry of the compounds. The variation of magnetic interaction by modifying the lattice parameter resembles Ruderman-Kittel-Kasuya-Yosida (RKKY) oscillations.

  14. Relativistic GW calculations on CH3NH3PbI3 and CH3NH3SnI3 perovskites for solar cell applications.

    Science.gov (United States)

    Umari, Paolo; Mosconi, Edoardo; De Angelis, Filippo

    2014-03-26

    Hybrid AMX3 perovskites (A = Cs, CH3NH3; M = Sn, Pb; X = halide) have revolutionized the scenario of emerging photovoltaic technologies, with very recent results demonstrating 15% efficient solar cells. The CH3NH3PbI3/MAPb(I(1-x)Cl(x))3 perovskites have dominated the field, while the similar CH3NH3SnI3 has not been exploited for photovoltaic applications. Replacement of Pb by Sn would facilitate the large uptake of perovskite-based photovoltaics. Despite the extremely fast progress, the materials electronic properties which are key to the photovoltaic performance are relatively little understood. Density Functional Theory electronic structure methods have so far delivered an unbalanced description of Pb- and Sn-based perovskites. Here we develop an effective GW method incorporating spin-orbit coupling which allows us to accurately model the electronic, optical and transport properties of CH3NH3SnI3 and CH3NH3PbI3, opening the way to new materials design. The different CH3NH3SnI3 and CH3NH3PbI3 electronic properties are discussed in light of their exploitation for solar cells, and found to be dominantly due to relativistic effects. These effects stabilize the CH3NH3PbI3 material towards oxidation, by inducing a deeper valence band edge. Relativistic effects, however, also increase the material band-gap compared to CH3NH3SnI3, due to the valence band energy downshift (~0.7 eV) being only partly compensated by the conduction band downshift (~0.2 eV).

  15. Atomically thin two-dimensional organic-inorganic hybrid perovskites

    Science.gov (United States)

    Dou, Letian; Wong, Andrew B.; Yu, Yi; Lai, Minliang; Kornienko, Nikolay; Eaton, Samuel W.; Fu, Anthony; Bischak, Connor G.; Ma, Jie; Ding, Tina; Ginsberg, Naomi S.; Wang, Lin-Wang; Alivisatos, A. Paul; Yang, Peidong

    2015-09-01

    Organic-inorganic hybrid perovskites, which have proved to be promising semiconductor materials for photovoltaic applications, have been made into atomically thin two-dimensional (2D) sheets. We report the solution-phase growth of single- and few-unit-cell-thick single-crystalline 2D hybrid perovskites of (C4H9NH3)2PbBr4 with well-defined square shape and large size. In contrast to other 2D materials, the hybrid perovskite sheets exhibit an unusual structural relaxation, and this structural change leads to a band gap shift as compared to the bulk crystal. The high-quality 2D crystals exhibit efficient photoluminescence, and color tuning could be achieved by changing sheet thickness as well as composition via the synthesis of related materials.

  16. Generalized trends in the formation energies of perovskite oxides.

    Science.gov (United States)

    Zeng, ZhenHua; Calle-Vallejo, Federico; Mogensen, Mogens B; Rossmeisl, Jan

    2013-05-28

    Generalized trends in the formation energies of several families of perovskite oxides (ABO3) and plausible explanations to their existence are provided in this study through a combination of DFT calculations, solid-state physics analyses and simple physical/chemical descriptors. The studied elements at the A site of perovskites comprise rare-earth, alkaline-earth and alkaline metals, whereas 3d and 5d metals were studied at the B site. We also include ReO3-type compounds, which have the same crystal structure of cubic ABO3 perovskites except without A-site elements. From the observations we extract the following four conclusions for the perovskites studied in the present paper: for a given cation at the B site, (I) perovskites with cations of identical oxidation state at the A site possess close formation energies; and (II) perovskites with cations of different oxidation states at the A site usually have quite different but ordered formation energies. On the other hand, for a given A-site cation, (III) the formation energies of perovskites vary linearly with respect to the atomic number of the elements at the B site within the same period of the periodic table, and the slopes depend systematically on the oxidation state of the A-site cation; and (IV) the trends in formation energies of perovskites with elements from different periods at the B site depend on the oxidation state of A-site cations. Since the energetics of perovskites is shown to be the superposition of the individual contributions of their constituent oxides, the trends can be rationalized in terms of A-O and B-O interactions in the ionic crystal. These findings reveal the existence of general systematic trends in the formation energies of perovskites and provide further insight into the role of ion-ion interactions in the properties of ternary compounds.

  17. Synthesis and Structure of A New Perovskite, SrCuO 2.5

    Science.gov (United States)

    Chen, Bai-Hao; Walker, Dave; Scott, Bruce A.; Mitzi, David B.

    1996-02-01

    A new oxygen-deficient perovskite, SrCuO2.5, was prepared at 950°C and 100 kbar pressure in a multianvil apparatus. Rietveld profile analysis, using X-ray powder diffraction data, was employed for the structural determination. SrCuO2.5is orthorhombic,Pbam(No. 55),Z= 4,a= 5.424(2) Â,b= 10.837(4) Â, andc= 3.731(1) Â, which is related to the perovskite subcell by root{2}ap× 2root{2}ap×ap, whereapis the simple cubic perovskite lattice parameter. It consists of corner-shared CuO5square pyramids with oxygen vacancy ordering in the CuO2layers. The ordered oxygen vacancies create parallel pseudo-hexagonal tunnels where the Sr atoms reside, forming SrO10polyhedra. Structural features with respect to oxygen vacancies, superstructures, and distortions are analogous to the type of ordering observed in Sr2CuO3+δ. Superconductivity was not observed in SrCuO2.5down to 5 K.

  18. Carrier injection and recombination processes in perovskite CH3NH3PbI3 solar cells studied by electroluminescence spectroscopy

    Science.gov (United States)

    Handa, Taketo; Okano, Makoto; Tex, David M.; Shimazaki, Ai; Aharen, Tomoko; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

    2016-02-01

    Organic-inorganic hybrid perovskite materials, CH3NH3PbX3 (X = I and Br), are considered as promising candidates for emerging thin-film photovoltaics. For practical implementation, the degradation mechanism and the carrier dynamics during operation have to be clarified. We investigated the degradation mechanism and the carrier injection and recombination processes in perovskite CH3NH3PbI3 solar cells using photoluminescence (PL) and electroluminescence (EL) imaging spectroscopies. By applying forward bias-voltage, an inhomogeneous distribution of the EL intensity was clearly observed from the CH3NH3PbI3 solar cells. By comparing the PL- and EL-images, we revealed that the spatial inhomogeneity of the EL intensity is a result of the inhomogeneous luminescence efficiency in the perovskite layer. An application of bias-voltage for several tens of minutes in air caused a decrease in the EL intensity and the conversion efficiency of the perovskite solar cells. The degradation mechanism of perovskite solar cells under bias-voltage in air is discussed.

  19. Fabrication and characterization of perovskite solar cells added with MnCl2, YCl3 or poly(methyl methacrylate)

    Science.gov (United States)

    Taguchi, Masaya; Suzuki, Atsushi; Tanaka, Hiroki; Oku, Takeo

    2018-01-01

    Perovskite-type CH3NH3PbI3-based photovoltaic devices were fabricated and characterized. Effects of manganese (Mn), yttrium (Y) compounds addition into the perovskite crystal on the photovoltaic properties were investigated. Also, the effects of poly(methyl methacrylate) (PMMA) addition on perovskite layer on the photovoltaic properties were investigated. When 3 % MnCl2 was added, the short circuit current density and conversion efficiency were improved by promoting the crystal growth of perovskite phase. The photoelectric conversion efficiency for 0.9 mg mL-1 PMMA added was 7.36 %. Open circuit voltage and fill factor were improved by 5 % YCl3 addition.

  20. High-pressure BaCrO_3 polytypes and the 5H–BaCrO_2_._8 phase

    International Nuclear Information System (INIS)

    Arévalo-López, Angel M.; Paul Attfield, J.

    2015-01-01

    Polytypism of BaCrO_3 perovskites has been investigated at 900–1100 °C and pressures up to 22 GPa. Hexagonal 5H, 4H, and 6H perovskites are observed with increasing pressure, and the cubic 3C perovskite (a=3.99503(1) Å) is observed in bulk form for the first time at 19–22 GPa. An oxygen-deficient material with limiting composition 5H–BaCrO_2_._8 is synthesised at 1200 °C under ambient pressure. This contains double tetrahedral Cr"4"+ layers and orders antiferromagnetically below 260 K with a (0 0 1/2) magnetic structure. - Graphical abstract: Hexagonal 5H, 4H, and 6H perovskites polytypes of BaCrO_3 are observed with increasing pressure and the cubic 3C perovskite is stabilised in bulk form for the first time at 19–22 GPa. Oxygen-deficient 5H–BaCrO_2_._8 synthesised at ambient pressure contains double tetrahedral Cr"4"+ layers and orders antiferromagnetically below 260 K with a (0 0 1/2) magnetic structure.

  1. Light-Independent Ionic Transport in Inorganic Perovskite and Ultrastable Cs-Based Perovskite Solar Cells.

    Science.gov (United States)

    Zhou, Wenke; Zhao, Yicheng; Zhou, Xu; Fu, Rui; Li, Qi; Zhao, Yao; Liu, Kaihui; Yu, Dapeng; Zhao, Qing

    2017-09-07

    Due to light-induced effects in CH 3 NH 3 -based perovskites, such as ion migration, defects formation, and halide segregation, the degradation of CH 3 NH 3 -based perovskite solar cells under maximum power point is generally implicated. Here we demonstrated that the effect of light-enhanced ion migration in CH 3 NH 3 PbI 3 can be eliminated by inorganic Cs substitution, leading to an ultrastable perovskite solar cell. Quantitatively, the ion migration barrier for CH 3 NH 3 PbI 3 is 0.62 eV under dark conditions, larger than that of CsPbI 2 Br (0.45 eV); however, it reduces to 0.07 eV for CH 3 NH 3 PbI 3 under illumination, smaller than that for CsPbI 2 Br (0.43 eV). Meanwhile, photoinduced halide segregation is also suppressed in Cs-based perovskites. Cs-based perovskite solar cells retained >99% of the initial efficiency (10.3%) after 1500 h of maximum power point tracking under AM1.5G illumination, while CH 3 NH 3 PbI 3 solar cells degraded severely after 50 h of operation. Our work reveals an uncovered mechanism for stability improvement by inorganic cation substitution in perovskite-based optoelectronic devices.

  2. Regulation of gene expression by dietary Ca2+ in kidneys of 25-hydroxyvitamin D3-1 alpha-hydroxylase knockout mice.

    NARCIS (Netherlands)

    Hoenderop, J.G.J.; Chon, H.; Gkika, D.; Bluyssen, H.A.; Holstege, F.C.; St. Arnaud, R.; Braam, B.; Bindels, R.J.M.

    2004-01-01

    BACKGROUND: Pseudovitamin D deficiency rickets (PDDR) is an autosomal disease, characterized by undetectable levels of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), rickets and secondary hyperparathyroidism. Mice in which the 25-hydroxyvitamin D3-1 alpha-hydroxylase (1 alpha-OHase) gene was inactivated,

  3. Acoustic phonons in the hexagonal perovskite CsNiCl3 around the Gamma-point

    DEFF Research Database (Denmark)

    Visser, D.; Monteith, A.R.; Rønnow, H.M.

    2000-01-01

    The acoustic phonon dispersion curves of the hexagonal perovskite CsNiCl3 were measured at room temperature in the vicinity of the Gamma-point along the [0 0 1] and [1 1 0] directions. The derived velocity of sound values for the longitudinal and transverse acoustic phonons are compared with the ......The acoustic phonon dispersion curves of the hexagonal perovskite CsNiCl3 were measured at room temperature in the vicinity of the Gamma-point along the [0 0 1] and [1 1 0] directions. The derived velocity of sound values for the longitudinal and transverse acoustic phonons are compared...

  4. Synthesis and characterization of perovskite-type Sr{sub x}Y{sub 1−x}FeO{sub 3−δ} (0.63≤x<1.0) and Sr{sub 0.75}Y{sub 0.25}Fe{sub 1−y}M{sub y}O{sub 3−δ} (M=Cr, Mn, Ni), (y=0.2, 0.33, 0.5)

    Energy Technology Data Exchange (ETDEWEB)

    Biendicho, J.J. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); The ISIS Facility, STFC Rutherford Appleton Laboratory, Didcot, OX11 0QX Oxfordshire (United Kingdom); Shafeie, S. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Frenck, L. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Université Pierre et Marie Curie, 75005 Paris (France); Gavrilova, D. [M.V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Böhme, S. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Technische Universität Chemnitz, Institut für Chemie, Straße der Nationen 62, D-09111 Chemnitz (Germany); Bettanini, A.M. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Department of Molecular Sciences and Nanosystems, University Ca’ Foscari of Venice, 30123 Venice (Italy); Svedlindh, P. [Department of Engineering Sciences, Uppsala University, Box 534, SE-751 21 Uppsala (Sweden); Hull, S. [The ISIS Facility, STFC Rutherford Appleton Laboratory, Didcot, OX11 0QX Oxfordshire (United Kingdom); Zhao, Z. [School of Industrial Engineering and Management, Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Istomin, S.Ya., E-mail: istomin@icr.chem.msu.ru [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); M.V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Grins, J.; Svensson, G. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden)

    2013-04-15

    Oxygen-deficient ferrates with the cubic perovskite structure Sr{sub x}Y{sub 1−x}FeO{sub 3−δ} were prepared in air (0.71≤x≤0.91) as well as in N{sub 2} (x=0.75 and 0.79) at 1573 K. The oxygen content of the compounds prepared in air increases with increasing strontium content from 3−δ=2.79(2) for x=0.75 to 3−δ=2.83(2) for x=0.91. Refinement of the crystal structure of Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} using TOF neutron powder diffraction (NPD) data shows high anisotropic atomic displacement parameter (ADP) for the oxygen atom resulting from a substantial cation and anion disorder. Electron diffraction (ED) and high-resolution electron microscopy (HREM) studies of Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} reveal a modulation along 〈1 0 0〉{sub p} with G± ∼0.4〈1 0 0〉{sub p} indicating a local ordering of oxygen vacancies. Magnetic susceptibility measurements at 5–390 K show spin-glass behaviour with dominating antiferromagnetic coupling between the magnetic moments of Fe cations. Among the studied compositions, Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} shows the lowest thermal expansion coefficient (TEC) of 10.5 ppm/K in air at 298–673 K. At 773–1173 K TEC increases up to 17.2 ppm/K due to substantial reduction of oxygen content. The latter also results in a dramatic decrease of the electrical conductivity in air above 673 K. Partial substitution of Fe by Cr, Mn and Ni according to the formula Sr{sub 0.75}Y{sub 0.25}Fe{sub 1−y}M{sub y}O{sub 3−δ} (y=0.2, 0.33, 0.5) leads to cubic perovskites for all substituents with y=0.2. Their TECs are higher in comparison with un-doped Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79}. Only M=Ni has increased electrical conductivity compared to un-doped Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79}. - Graphical abstract: Oxygen-deficient ferrates with the cubic perovskite structure Sr{sub x}Y{sub 1−x}FeO{sub 3−δ} were prepared both in air (0.71≤x≤0.91) and N{sub 2} (x=0.75 and 0.79) at 1573 K. Refinement of the

  5. Clinical implications of vitamin D deficiency

    Directory of Open Access Journals (Sweden)

    Beata Matyjaszek-Matuszek

    2015-06-01

    Full Text Available Vitamin D deficiency is a common medical problem worldwide and its prevalence rises along with latitude, obesity, sedentary lifestyle, limited sunlight exposure and aging. A great body of evidence has shown that patients with vitamin D deficiency have increased cardiovascular risks and total mortality. Conversely, the presence of comorbidities progressive with age such as abdominal obesity, insulin resistance, type 2 diabetes and hypertension places the patients at an increased risk of vitamin D deficiency. The multidirectional effect of vitamin D deficiency is present in different phases of the aging process. Based on the literature review, the risk factors for vitamin D insufficiency most often found in post-menopausal women include limited sun exposure and time spent outdoors, inadequate dietary vitamin D intake, winter season and increased age. Vitamin D supplementation in this group might offer prevention of falls and fractures and may be beneficial for cardiovascular health, what may be especially important in osteoporotic and elderly populations. Prevention and treatment processes involve education regarding sunlight exposure and pharmacological cholecalciferol supplementation according to the recommendations for Central Europe. This manuscript reviews the role of vitamin D and its deficiency and considers their clinical implications, with particular regard to peri- and postmenopausal women.

  6. Dendrimer ligands-capped CH3NH3PbBr3 perovskite nanocrystals with delayed halide exchange and record stability against both moisture and water

    Science.gov (United States)

    Xu, Yiren; Xu, Shuhong; Shao, Haibao; Jiang, Han; Cui, Yiping; Wang, Chunlei

    2018-06-01

    CH3NH3PbBr3 perovskite nanocrystals (NCs) suffer from poor stability because of their high sensitivity to environmental moisture and water. To solve this problem, previous works mainly focus on embedding perovskite NCs into water-resistant matrix to form large composites (size of microns or larger). As an alternative solution without serious changing of NC size, enhancing the stability of perovskite NCs themselves by ligand engineering is rarely reported. In this work, we used hyperbranched polyamidoamine (PAMAM) dendrimers with two different generations (G0 and G4) to synthesize CH3NH3PbBr3 perovskite NCs with high photoluminescence (PL) quantum yields (QY) above 70% and a new record stability. A novel dendrimers generation-dependent stability of perovskite NCs was observed. The water-resistance time is 18 h (27 h) for perovskite NCs capped by G0 (G4) generation of PAMAM, which is 7 times (11 times) longer than that of traditional oleic acid-capped NCs. Similar PAMAM generation-related stability is also observed in moisture-resistance tests. The stability time against moisture is 500 h (800 h) for G0 (G4) generation of PAMAM-capped perovskite NCs, which is a new record stability time against moisture for CH3NH3PbBr3 perovskite NCs. In addition, our results also indicate that PAMAM ligands outside perovskite NCs can dramatically slow down the speed of halide exchange. Even for the mixture of perovskite NCs with two different halide composition, the original luminescence properties of PAMAM-capped perovskite NCs can retain after mixing. In view of slow halide exchange speed, excellent water and moisture stability, PAMAM dendrimers-capped perovskite NCs and their mixture are available as color conversion single layer in fabrication of light-emitting diodes (LED).

  7. Dendrimer ligands-capped CH3NH3PbBr3 perovskite nanocrystals with delayed halide exchange and record stability against both moisture and water.

    Science.gov (United States)

    Xu, Yiren; Xu, Shuhong; Shao, Haibao; Jiang, Han; Cui, Yiping; Wang, Chunlei

    2018-06-08

    CH 3 NH 3 PbBr 3 perovskite nanocrystals (NCs) suffer from poor stability because of their high sensitivity to environmental moisture and water. To solve this problem, previous works mainly focus on embedding perovskite NCs into water-resistant matrix to form large composites (size of microns or larger). As an alternative solution without serious changing of NC size, enhancing the stability of perovskite NCs themselves by ligand engineering is rarely reported. In this work, we used hyperbranched polyamidoamine (PAMAM) dendrimers with two different generations (G0 and G4) to synthesize CH 3 NH 3 PbBr 3 perovskite NCs with high photoluminescence (PL) quantum yields (QY) above 70% and a new record stability. A novel dendrimers generation-dependent stability of perovskite NCs was observed. The water-resistance time is 18 h (27 h) for perovskite NCs capped by G0 (G4) generation of PAMAM, which is 7 times (11 times) longer than that of traditional oleic acid-capped NCs. Similar PAMAM generation-related stability is also observed in moisture-resistance tests. The stability time against moisture is 500 h (800 h) for G0 (G4) generation of PAMAM-capped perovskite NCs, which is a new record stability time against moisture for CH 3 NH 3 PbBr 3 perovskite NCs. In addition, our results also indicate that PAMAM ligands outside perovskite NCs can dramatically slow down the speed of halide exchange. Even for the mixture of perovskite NCs with two different halide composition, the original luminescence properties of PAMAM-capped perovskite NCs can retain after mixing. In view of slow halide exchange speed, excellent water and moisture stability, PAMAM dendrimers-capped perovskite NCs and their mixture are available as color conversion single layer in fabrication of light-emitting diodes (LED).

  8. A Single-Crystal Neutron Diffraction Study on Magnetic Structure of the Quasi-One-Dimensional Antiferromagnet SrCo_2V_2O_8

    International Nuclear Information System (INIS)

    Liu Juan-Juan; Wang Jin-Chen; Luo Wei; Sheng Jie-Ming; Bao Wei; He Zhang-Zhen; Danilkin, S. A.

    2016-01-01

    The magnetic structure of the spin-chain antiferromagnet SrCo_2V2O_8 is determined by single-crystal neutron diffraction experiment. The system undergoes a long-range magnetic order below the critical temperature T_N = 4.96 K. The moment of 2.16μ_B per Co at 1.6 K in the screw chain running along the c axis alternates in the c axis. The moments of neighboring screw chains are arranged antiferromagnetically along one in-plane axis and ferromagnetically along the other in-plane axis. This magnetic configuration breaks the four-fold symmetry of the tetragonal crystal structure and leads to two equally populated magnetic twins with the antiferromagnetic vector in the a or b axis. The very similar magnetic state to the isostructural BaCo_2V_2O_8 warrants SrCo_2V_2O_8 as another interesting half-integer spin-chain antiferromagnet for investigation on quantum antiferromagnetism. (paper)

  9. Stable high efficiency two-dimensional perovskite solar cells via cesium doping

    KAUST Repository

    Zhang, Xu

    2017-08-15

    Two-dimensional (2D) organic-inorganic perovskites have recently emerged as one of the most important thin-film solar cell materials owing to their excellent environmental stability. The remaining major pitfall is their relatively poor photovoltaic performance in contrast to 3D perovskites. In this work we demonstrate cesium cation (Cs) doped 2D (BA)(MA)PbI perovskite solar cells giving a power conversion efficiency (PCE) as high as 13.7%, the highest among the reported 2D devices, with excellent humidity resistance. The enhanced efficiency from 12.3% (without Cs) to 13.7% (with 5% Cs) is attributed to perfectly controlled crystal orientation, an increased grain size of the 2D planes, superior surface quality, reduced trap-state density, enhanced charge-carrier mobility and charge-transfer kinetics. Surprisingly, it is found that the Cs doping yields superior stability for the 2D perovskite solar cells when subjected to a high humidity environment without encapsulation. The device doped using 5% Cs degrades only ca. 10% after 1400 hours of exposure in 30% relative humidity (RH), and exhibits significantly improved stability under heating and high moisture environments. Our results provide an important step toward air-stable and fully printable low dimensional perovskites as a next-generation renewable energy source.

  10. Perovskite Solar Cell

    Indian Academy of Sciences (India)

    Organic–inorganic halide perovskite, a newcomerin the solar cell industry has proved its potential forincreasing efficiency rapidly from 3.8% in 2009 to 22.1% in2016. High efficiency, flexibility, and cell architecture of theemerging hybrid halide perovskite have caught the attentionof researchers and technologists in the field.

  11. Prevalence of Vitamin D Deficiency in Adult Outpatients With Bipolar Disorder or Schizophrenia.

    Science.gov (United States)

    Boerman, Remco; Cohen, Dan; Schulte, Peter F J; Nugter, Annet

    2016-12-01

    Several studies show an association between schizophrenia and low levels of vitamin D. To date, there are only few studies about the prevalence of vitamin D deficiency in patients with bipolar disorder. We hypothesized that vitamin D deficiency is less common among patients with bipolar disorder than among patients with schizophrenia or schizoaffective disorder. A second hypothesis is that vitamin D deficiency is more prevalent among patients with schizophrenia, schizoaffective disorder, or bipolar disorders than among the general Dutch population.Most studies have been conducted with hospitalized patients; in this study, we only included outpatients. All outpatients of a center for bipolar disorders and all outpatients of 3 flexible assertive community treatment teams were asked to participate in this cross-sectional study. We included 118 patients with bipolar disorder and 202 patients with schizophrenia or schizoaffective disorder. Vitamin D levels were deficient in 30.3% (95% confidence interval, 25.5-35.6) of the cases. The type of psychiatric disorder was not a predictor of vitamin D deficiency. The absolute difference in risk of deficiency between the study population and the Dutch Caucasian population was 23.8% (95% confidence interval, 18.3%-29.3%). In this study, vitamin D deficiency was 4.7 times more common among outpatients with bipolar disorder, schizophrenia, or schizoaffective disorder than among the Dutch general population.Given the high prevalence of vitamin D deficiency, we believe that outpatients with bipolar disorder, schizophrenia, or schizoaffective disorder should be considered at risk of having low levels of vitamin D. Annual measurement of vitamin D levels in psychiatric outpatients with these disorders seems to be justified to maintain bone health, muscle strength, and to prevent osteoporosis.

  12. VitaminA, E, and D deficiencies in tunisian very low birth weight neonates: prevalence and risk factors.

    Science.gov (United States)

    Fares, Samira; Sethom, Mohamed Marouane; Khouaja-Mokrani, Chahnez; Jabnoun, Sami; Feki, Moncef; Kaabachi, Naziha

    2014-06-01

    Preterm neonates are at high risk of vitamin deficiencies, which may expose them to increased morbidity and mortality. This study aimed to determine the prevalence and risk factors for vitamin A, E, and D deficiencies in Tunisian very low birth weight (VLBW) neonates. A total of 607 VLBW and 300 term neonates were included in the study. Plasma vitamins A and E were assessed by high performance liquid chromatography and vitamin D was assessed by radioimmunoassay. Prevalence of vitamin A, E, and D deficiencies were dramatically elevated in VLBW neonates and were significantly higher than term neonates (75.9% vs. 63.3%; 71.3% vs. 55.5%; and 65.2% vs. 40.4%, respectively). In VLBW neonates, the prevalence of vitamin deficiencies was significantly higher in lower classes of gestational age and birth weight. Vitamin E deficiency was associated with pre-eclampsia [odds ratio (OR) (95% confidence interval, 95% CI), 1.56 (1.01-2.44); p < 0.01] and gestational diabetes [4.01 (1.05-17.0); p < 0.01]. Vitamin D deficiency was associated with twin pregnancy [OR (95% CI), 2.66 (1.33-5.35); p < 0.01] and pre-eclampsia [2.89 (1.36-6.40); p < 0.01]. Vitamin A, E, and D deficiencies are very common in Tunisian VLBW neonates and are associated with pre-eclampsia. Improved nutritional and health support for pregnant women and high dose vitamins A, E, and D supplementation in VLBW neonates are strongly required in Tunisia. Copyright © 2013. Published by Elsevier B.V.

  13. Vitamin D deficiency in Fibromyalgia

    International Nuclear Information System (INIS)

    Bhatty, S.A.; Shaikh, N.A.; Irfan, M.; Kashif, S.M.; Vaswani, A.S.; Sumbhai, A.; Gunpat

    2010-01-01

    Objective: To check the Vitamin D levels in patients diagnosed as fibromyagia in our population. Methods: Study was done at Medical OPD of Civil Hospital Karachi, from January to March 2009. Female patients diagnosed as Fibromyalgia according to American College of Rheumatology (ACR) criteria and exclusion of systemic illness on examination, and normal reports of blood CP, ESR, serum calcium, phosphate and Alkaline Phosphatase, were asked to get Vitamin D levels in their serum. Vitamin D deficiency is defined as 30 ng/ml. Result: Forty female patients were included in the study. The mean age was 37.65 +- 11.5 years. Mean Vitamin D level was 17.41 +- 5.497 ng/ml. Thirty two (80%) of patients had Vitamin D deficiency, mean levels of 15.855 +- 4.918 ng/ml and 8(20%) had Vitamin D insufficiency, mean levels of 23.64 +- 2.39 ng/ml. Patients with vitamin D deficiency and age less than 45 years were 22 (68.75%), had mean vitamin D level 16.87 +- 4.48 ng/ml whereas in age ranging from 46-75 years were 10 (31.25%) had mean vitamin D level 16.09 +- 6.45 ng/ml. Conclusion: Vitamin D deficiency is frequently seen in patients diagnosed as fibromyalgia and nonspecific musculoskeletal pain in our population. Although the sample size of the study is small, but the figures are so alarming that it is an eye opener towards the need of a population based study, including normal population as well as those presenting with musculoskeletal pain. (author)

  14. Potassium doped methylammonium lead iodide (MAPbI3) thin films as a potential absorber for perovskite solar cells; structural, morphological, electronic and optoelectric properties

    Science.gov (United States)

    Muzammal uz Zaman, Muhammad; Imran, Muhammad; Saleem, Abida; Kamboh, Afzal Hussain; Arshad, Muhammad; Khan, Nawazish Ali; Akhter, Parvez

    2017-10-01

    In this article, we have demonstrated the doping of K in the light absorbing CH3NH3PbI3 perovskite i.e. (M = CH3, A = NH3; x = 0-1). One of the major merits of methylammonium lead iodide (CH3NH3PbI3) perovskites is that they act as efficient absorbing material of light in photovoltaic cell imparting long carrier lifetime and optimum band gap. The structural, morphological, electronic and optoelectric properties of potassium (K) doped light absorber methylammonium lead iodide (CH3NH3PbI3) perovskites are reported here i.e. Kx(MA)1-xPbI3 (M = CH3, A =NH3; x = 0-1). The thin films of perovskites (x = 0-1) were deposited by spin coating on cleaned FTO substrates and characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), current-voltage (IV), X-ray photoelectron spectroscopy (XPS) and Diffused reflectance spectroscopy (DRS) analysis. The organic constituents i.e. MA = CH3NH3, in perovskites solar cells induce instability even at the room temperature. To overcome such instabilities we have replaced the organic constituents by K because both of them have electropositive nature. Potassium successfully replaces the CH3NH3. Initially, this compound grows in a tetragonal crystal structure, however, beyond 30% doping of potassium orthorhombic distortions are induced in the parent tetragonal unit cell. Such phase transformation is microscopically visible in the electron micrographs of doped samples; cubic grains for MAPbI3 begin to transform into strip like structures in K-doped samples. The resistance of the samples is decreased for partial K-doping, which we suggested to be arising due to the electropositive nature of K. It is observed that the binding energy difference between Pb4f and I3d core levels are very similar in all the investigated systems and show formal oxidation states. Also, the partially doped samples showed increased absorption and bandgaps around 1.5 eV which is an optimum value for solar absorption.

  15. Sensing properties of perovskite oxide La0.5SR0.5Co0-3-d obtained by using pulsed laser deposition

    NARCIS (Netherlands)

    Dam, T.V.A.; Olthuis, Wouter; Bergveld, Piet

    2004-01-01

    La1−xSrxCoO3−δ belongs to the group of perovskite oxides of the ABO3 structure, with a trivalent rare earth in the A position (La) and a trivalent metal ion in the B position (Co). Doping with divalent Sr-ions at the trivalent La-positions creates oxygen vacancies which give the oxide catalytic

  16. Preparation and characterization of La1-xCexCoO3 perovskite oxides for energy materials

    International Nuclear Information System (INIS)

    Nyamdavaa, E.; Sevjidsuren, G.; Altantsog, P.; Yuanga, E.

    2016-01-01

    Cerium-doped lanthanum cobaltite perovskites (La 1-x Ce x CoO 3 with x = 0,0.2, 0.4) were prepared by the sol-gel method (calcined for 5 h at 750°C) and characterized by X-ray diffraction (XRD), X-ray absorption (XAS), energy-dispersive X-ray spectroscopy (EDS), and BET surface area analysis. The results showed that the cerium doping promoted the structural transformation of LaCoO 3 from rhombohedral into the cubic structure. High specific surface area and small crystallite size are achieved at x = 0.2. The XAS results confirmed the formation of compound La 1-x Ce x CoO 3 . [ru

  17. Enhancement of photoresponse property of perovskite solar cell by aluminium chloride (AlCl3)

    Science.gov (United States)

    Ghosh, S. S.; Sil, A.

    2018-05-01

    The fabrication of a three layer solar cell device is a new area of research. The formation of perovskite phase is evident from x-ray diffraction and its particle size is observed by microstructural analysis. A thin layer of gold coating over the device increases the surface conductivity. Direct contact between a SnCl2 or AlCl3 based perovskite with the gold coating increases the durability of the film but decreases the hole transport properties due to absence of an organic hole transport material. The absorbance spectroscopy analysis gives characteristic peaks showing the evidence of ITO, TiO2 (rutile) and Sn2+ complexes present in the Sn-perovskite film or Al3+ complexes present within the Al-perovskite cell. The desired absorbance near 550 nm due to Al3+ complexes causes a much higher flow of current on illumination and thus is also evidenced by the presence of comparatively high intensity PL spectra in the Al-perovskite system which occurred due to free exciton formation near band edge excitation. The fill factor of the devices is estimated as ∼0.83 and ∼0.65 for Sn-perovskite and Al-perovskite devices respectively. The PCE values of Sn-perovskite and Al-perovskite devices are calculated 0.39% and 0.96% respectively, which establish Al-perovskite film as a useful component for future solar cell device manufacturing.

  18. Nanocrystalline La1-xSrxCo1-yFe yO3 perovskites fabricated by the micro-emulsion route for high frequency response devices fabrications

    KAUST Repository

    Azhar Khan, Muhammad; Khan, Kamran; Mahmood, Azhar; Murtaza, Gulam; Akhtar, Majid Niaz; Ali, Irshad M.; Shahid, Muhammad; Shakir, Imran; Farooq Warsi, Muhammad

    2014-01-01

    Nanocrystalline La1-xSrxCo1-yFe yO3 (x=0.00-0.60) perovskites were fabricated by a cheap economic route (i.e. micro-emulsion method) and characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), fourier transform infrared (FTIR

  19. Clinical correlates of vitamin D deficiency in established psychosis.

    Science.gov (United States)

    Lally, J; Gardner-Sood, P; Firdosi, M; Iyegbe, C; Stubbs, B; Greenwood, K; Murray, R; Smith, S; Howes, O; Gaughran, F

    2016-03-22

    Suboptimal vitamin D levels have been identified in populations with psychotic disorders. We sought to explore the relationship between vitamin D deficiency, clinical characteristics and cardiovascular disease risk factors among people with established psychosis. Vitamin D levels were measured in 324 community dwelling individuals in England with established psychotic disorders, along with measures of mental health, cardiovascular risk and lifestyle choices. Vitamin D deficiency was defined as serum 25-hydroxyvitamin D (25-OHD) levels below 10 ng/ml (equivalent to Vitamin D as above 30 ng/ml (>50 nmol/L). The mean 25-OHD serum level was 12.4 (SD 7.3) ng/ml, (range 4.0-51.7 ng/ml). Forty nine percent (n = 158) were vitamin D deficient, with only 14 % (n = 45) meeting criteria for sufficiency. Accounting for age, gender, ethnicity and season of sampling, serum 25-OHD levels were negatively correlated with waist circumference (r = -0.220, p vitamin D deficiency. Lower vitamin D levels are associated with increased cardiovascular disease risk factors and in particular metabolic syndrome. Further research is needed to define appropriate protocols for vitamin D testing and supplementation in practice to see if this can improve cardiovascular disease risk. ISRCTN number is ISRCTN58667926 Date of registration: 23/04/2010.

  20. Tunable thermodynamic activity of La x Sr1-x Mn y Al1-y O3-δ (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) perovskites for solar thermochemical fuel synthesis.

    Science.gov (United States)

    Ezbiri, M; Takacs, M; Theiler, D; Michalsky, R; Steinfeld, A

    2017-02-28

    Nonstoichiometric metal oxides with variable valence are attractive redox materials for thermochemical and electrochemical fuel processing. To guide the design of advanced redox materials for solar-driven splitting of CO 2 and/or H 2 O to produce CO and/or H 2 (syngas), we investigate the equilibrium thermodynamics of the La x Sr 1- x Mn y Al 1- y O 3- δ perovskite family (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) and La 0.6 Ca 0.4 Mn 0.8 Al 0.2 O 3- δ , and compare them to those of CeO 2 as the baseline. Oxygen nonstoichiometry measurements from 1573 to 1773 K and from 0.206 to 180 mbar O 2 show a tunable reduction extent, increasing with increasing Sr content. Maximal nonstoichiometry of 0.32 is established with La 0.2 Sr 0.8 Mn 0.8 Al 0.2 O 3- δ at 1773 K and 2.37 mbar O 2 . As a trend, we find that oxygen capacities are most sensitive to the A-cation composition. Partial molar enthalpy, entropy and Gibbs free energy changes for oxide reduction are extracted from the experimental data using defect models for Mn 4+ /Mn 3+ and Mn 3+ /Mn 2+ redox couples. We find that perovskites exhibit typically decreasing enthalpy changes with increasing nonstoichiometries. This desirable characteristic is most pronounced by La 0.6 Sr 0.4 Mn 0.4 Al 0.6 O 3- δ , rendering it attractive for CO 2 and H 2 O splitting. Generally, perovskites show lower enthalpy and entropy changes than ceria, resulting in more favorable reduction but less favorable oxidation equilibria. The energy penalties due to larger temperature swings and excess oxidants are discussed in particular. Using electronic structure theory, we conclude with a practical methodology estimating thermodynamic activity to rationally design perovskites with variable stoichiometry and valence.

  1. Vitamin D and iron deficiencies in children and adolescents with cerebral palsy.

    Science.gov (United States)

    Le Roy, C; Barja, S; Sepúlveda, C; Guzmán, M L; Olivarez, M; Figueroa, M J; Alvarez, M

    2018-01-13

    Children and adolescents with cerebral palsy (CP) are at a greater risk of malnutrition and micronutrient deficiencies. Two deficiencies that we can study and treat are vitaminD (VD) and iron deficiencies; however, no studies have described these deficiencies in Chile. To describe the status of VD and iron in patients with CP and evaluate the relationship with certain factors associated with deficiencies of these micronutrients. We performed a descriptive, cross-sectional study including 69 patients aged between 2 and 21years, from two public hospitals. Data were obtained on demographic variables, motor function, use of feeding tube, and pharmacological treatment. We performed a nutritional assessment according to patterns of CP and determined 25-hydroxyvitaminD (25[OH]D) ferritin, and albumin levels. Patients' mean age was 11.1±4.9years; 43 (62.3%) were male; and 56 (81.2%) had moderate-to-severe CP. Thirty-five (50.7%) used a nasogastric tube and/or gastrostomy; 15.4% were underweight and 73.8% were eutrophic, all with normal height. Twenty (29%) and 4 patients (6.2%) received VD and iron supplementation, respectively. Albuminaemia was normal in all patients. Mean 25(OH)D level was 24.3±8.8ng/mL; 33 patients (47.8%) had insufficiency and 21 (30.4%) deficiency; 36 patients (52.2%) had low ferritin levels. There was no association between 25(OH)D level and the other variables studied. Low ferritin levels were found to be associated with older age (P=.03), being male (P=.006), and feeding tube use (P=.006). The patients studied mainly had moderate-to-severe CP, with a high frequency of suboptimal VD values and low plasma ferritin; few patients received VD and/or iron supplementation. We suggest monitoring 25(OH)D and ferritin levels due to the high rate of deficiency of these nutrients; public hospitals should be equipped with drugs to treat these deficiencies. Copyright © 2017 Sociedad Española de Neurología. Publicado por Elsevier España, S.L.U. All rights

  2. Decreasing the electronic confinement in layered perovskites through intercalation.

    Science.gov (United States)

    Smith, Matthew D; Pedesseau, Laurent; Kepenekian, Mikaël; Smith, Ian C; Katan, Claudine; Even, Jacky; Karunadasa, Hemamala I

    2017-03-01

    We show that post-synthetic small-molecule intercalation can significantly reduce the electronic confinement of 2D hybrid perovskites. Using a combined experimental and theoretical approach, we explain structural, optical, and electronic effects of intercalating highly polarizable molecules in layered perovskites designed to stabilize the intercalants. Polarizable molecules in the organic layers substantially alter the optical and electronic properties of the inorganic layers. By calculating the spatially resolved dielectric profiles of the organic and inorganic layers within the hybrid structure, we show that the intercalants afford organic layers that are more polarizable than the inorganic layers. This strategy reduces the confinement of excitons generated in the inorganic layers and affords the lowest exciton binding energy for an n = 1 perovskite of which we are aware. We also demonstrate a method for computationally evaluating the exciton's binding energy by solving the Bethe-Salpeter equation for the exciton, which includes an ab initio determination of the material's dielectric profile across organic and inorganic layers. This new semi-empirical method goes beyond the imprecise phenomenological approximation of abrupt dielectric-constant changes at the organic-inorganic interfaces. This work shows that incorporation of polarizable molecules in the organic layers, through intercalation or covalent attachment, is a viable strategy for tuning 2D perovskites towards mimicking the reduced electronic confinement and isotropic light absorption of 3D perovskites while maintaining the greater synthetic tunability of the layered architecture.

  3. CH3 NH3 PbBr3 Perovskite Nanocrystals as Efficient Light-Harvesting Antenna for Fluorescence Resonance Energy Transfer.

    Science.gov (United States)

    Muthu, Chinnadurai; Vijayan, Anuja; Nair, Vijayakumar C

    2017-05-04

    Hybrid perovskites have created enormous research interest as a low-cost material for high-performance photovoltaic devices, light-emitting diodes, photodetectors, memory devices and sensors. Perovskite materials in nanocrystal form that display intense luminescence due to the quantum confinement effect were found to be particularly suitable for most of these applications. However, the potential use of perovskite nanocrystals as a light-harvesting antenna for possible applications in artificial photosynthesis systems is not yet explored. In the present work, we study the light-harvesting antenna properties of luminescent methylammonium lead bromide (CH 3 NH 3 PbBr 3 )-based perovskite nanocrystals using fluorescent dyes (rhodamine B, rhodamine 101, and nile red) as energy acceptors. Our studies revealed that CH 3 NH 3 PbBr 3 nanocrystals are an excellent light-harvesting antenna, and efficient fluorescence resonance energy transfer occurs from the nanocrystals to fluorescent dyes. Further, the energy transfer efficiency is found to be highly dependent on the number of anchoring groups and binding ability of the dyes to the surface of the nanocrystals. These observations may have significant implications for perovskite-based light-harvesting devices and their possible use in artificial photosynthesis systems. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Impaired bone formation in Pdia3 deficient mice.

    Directory of Open Access Journals (Sweden)

    Yun Wang

    Full Text Available 1α,25-Dihydroxyvitamin D3 [1α,25(OH2D3] is crucial for normal skeletal development and bone homeostasis. Protein disulfide isomerase family A, member 3 (PDIA3 mediates 1α,25(OH2D3 initiated-rapid membrane signaling in several cell types. To understand its role in regulating skeletal development, we generated Pdia3-deficient mice and examined the physiologic consequence of Pdia3-disruption in embryos and Pdia3+/- heterozygotes at different ages. No mice homozygous for the Pdia3-deletion were found at birth nor were there embryos after E12.5, indicating that targeted disruption of the Pdia3 gene resulted in early embryonic lethality. Pdia3-deficiency also resulted in skeletal manifestations as revealed by µCT analysis of the tibias. In comparison to wild type mice, Pdia3 heterozygous mice displayed expanded growth plates associated with decreased tether formation. Histomorphometry also showed that the hypertrophic zone in Pdia3+/- mice was more cellular than seen in wild type growth plates. Metaphyseal trabecular bone in Pdia3+/- mice exhibited an age-dependent phenotype with lower BV/TV and trabecular numbers, which was most pronounced at 15 weeks of age. Bone marrow cells from Pdia3+/- mice exhibited impaired osteoblastic differentiation, based on reduced expression of osteoblast markers and mineral deposition compared to cells from wild type animals. Collectively, our findings provide in vivo evidence that PDIA3 is essential for normal skeletal development. The fact that the Pdia3+/- heterozygous mice share a similar growth plate and bone phenotype to nVdr knockout mice, suggests that PDIA3-mediated rapid membrane signaling might be an alternative mechanism responsible for 1α,25(OH2D3's actions in regulating skeletal development.

  5. Effects of GeI2 or ZnI2 addition to perovskite CH3NH3PbI3 photovoltaic devices

    Science.gov (United States)

    Tanaka, Hiroki; Ohishi, Yuya; Oku, Takeo

    2018-01-01

    CH3NH3PbI3 added with GeI2 or ZnI2 perovskite photovoltaic devices were fabricated characterized. The surface coverages of the perovskite layers were improved by the addition of GeI2 or ZnI2. Formation of PbI2 observed for the pristine CH3NH3PbI3 was suppressed by the GeI2 or ZnI2 addition, which resulted in the improvement of the conversion efficiencies of the perovskite photovoltaic devices.

  6. Solid-state epitaxial effects in structurally diphasic xerogel of Pb(Mg1/3Nb2/3)O3

    International Nuclear Information System (INIS)

    Ravindranathan, P.; Komarneni, S.; Roy, R.

    1990-01-01

    Lead magnesium niobate (PMN), Pb(Mg 1/3 Nb 2/3 )O 3 , with perovskite structure has been prepared using structurally diphasic PMN gels. The diphasic gels were made using various concentrations of perovskite PMN seeds. The unseeded gel calcined at 775 degrees C for 2 h gave ∼ 98% of perovskite PMN phase. The use of 1% PMN perovskite seed not only led to a pure perovskite phase but also lowered the crystallization temperature of these gels by about 75 degrees C. These results show that isostructural seeding helps to lower the crystallization temperature of perovskite PMN phase

  7. Modulating Excitonic Recombination Effects through One-Step Synthesis of Perovskite Nanoparticles for Light-Emitting Diodes.

    Science.gov (United States)

    Kulkarni, Sneha A; Muduli, Subas; Xing, Guichuan; Yantara, Natalia; Li, Mingjie; Chen, Shi; Sum, Tze Chien; Mathews, Nripan; White, Tim J; Mhaisalkar, Subodh G

    2017-10-09

    The primary advantages of halide perovskites for light-emitting diodes (LEDs) are solution processability, direct band gap, good charge-carrier diffusion lengths, low trap density, and reasonable carrier mobility. The luminescence in 3D halide perovskite thin films originates from free electron-hole bimolecular recombination. However, the slow bimolecular recombination rate is a fundamental performance limitation. Perovskite nanoparticles could result in improved performance but processability and cumbersome synthetic procedures remain challenges. Herein, these constraints are overcome by tailoring the 3D perovskite as a near monodisperse nanoparticle film prepared through a one-step in situ deposition method. Replacing methyl ammonium bromide (CH 3 NH 3 Br, MABr) partially by octyl ammonium bromide [CH 3 (CH 2 ) 7 NH 3 Br, OABr] in defined mole ratios in the perovskite precursor proved crucial for the nanoparticle formation. Films consisting of the in situ formed nanoparticles displayed signatures associated with excitonic recombination, rather than that of bimolecular recombination associated with 3D perovskites. This transition was accompanied by enhanced photoluminescence quantum yield (PLQY≈20.5 % vs. 3.40 %). Perovskite LEDs fabricated from the nanoparticle films exhibit a one order of magnitude improvement in current efficiency and doubling in luminance efficiency. The material processing systematics derived from this study provides the means to control perovskite morphologies through the selection and mixing of appropriate additives. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Charge carrier transport mechanisms in perovskite CdTiO3 fibers

    Directory of Open Access Journals (Sweden)

    Z. Imran

    2014-06-01

    Full Text Available Electrical transport properties of electrospun cadmium titanate (CdTiO3 fibers have been investigated using ac and dc measurements. Air annealing of as spun fibers at 1000 °C yielded the single phase perovskite fibers having diameter ∼600 nm - 800 nm. Both the ac and dc electrical measurements were carried out at temperatures from 200 K – 420 K. The complex impedance plane plots revealed a single semicircular arc which indicates the interfacial effect due to grain boundaries of fibers. The dielectric properties obey the Maxwell-Wagner theory of interfacial polarization. In dc transport study at low voltages, data show Ohmic like behavior followed by space charge limited current (SCLC with traps at higher voltages at all temperatures (200 K – 420 K. Trap density in our fibers system is Nt = 6.27 × 1017 /cm3. Conduction mechanism in the sample is governed by 3-D variable range hopping (VRH from 200 K – 300 K. The localized density of states were found to be N(EF = 5.51 × 1021 eV−1 cm−3 at 2 V. Other VRH parameters such as hopping distance (Rhop and hopping energy (Whop were also calculated. In the high temperature range of 320 K – 420 K, conductivity follows the Arrhenius law. The activation energy found at 2 V is 0.10 eV. Temperature dependent and higher values of dielectric constant make the perovskite CdTiO3 fibers efficient material for capacitive energy storage devices.

  9. First-principles study of structural stability and elastic property of pre-perovskite PbTiO3

    International Nuclear Information System (INIS)

    Liu Yong; Ni Li-Hong; Ren Zhao-Hui; Xu Gang; Li Xiang; Song Chen-Lu; Han Gao-Rong

    2012-01-01

    The structural stability and the elastic properties of a novel structure of lead titanate, which is named pre- perovskite PbTiO 3 (PP-PTO) and is constructed with TiO 6 octahedral columns arranged in a one-dimensional manner, are investigated by using first-principles calculations. PP-PTO is energetically unstable compared with conventional perovskite phases, however it is mechanically stable. The equilibrium transition pressures for changing from pre- perovskite to cubic and tetragonal phases are −0.5 GPa and −1.4 GPa, respectively, with first-order characteristics. Further, the differences in elastic properties between pre-perovskite and conventional perovskite phases are discussed for the covalent bonding network, which shows a highly anisotropic character in PP-PTO. This study provides a crucial insight into the structural stabilities of PP-PTO and conventional perovskite. (condensed matter: structural, mechanical, and thermal properties)

  10. Role of the chemical substitution on the structural and luminescence properties of the mixed halide perovskite thin MAPbI{sub 3−x}Br{sub x} (0 ≤ x ≤ 1) films

    Energy Technology Data Exchange (ETDEWEB)

    Atourki, Lahoucine, E-mail: lahoucine.atourki@edu.uiz.ac.ma [Materials and Renewable Energy Laboratory, Faculty of Science, Ibn Zohr University, Agadir (Morocco); Vega, Erika; Marí, Bernabé; Mollar, Miguel [Instituto de Diseño y Fabricación (IDF), Universitat Politécnica de València, València (Spain); Ait Ahsaine, Hassan [Laboratoire Matériaux et environnement LME, Faculté des Sciences d' Agadir, Université Ibn Zohr, Agadir (Morocco); Bouabid, Khalid; Ihlal, Ahmed [Materials and Renewable Energy Laboratory, Faculty of Science, Ibn Zohr University, Agadir (Morocco)

    2016-05-15

    Highlights: • X-ray diffraction analyses indicate the formation of a tetragonal phase I4/mcm up to x = 0.4 and a cubic perovskite with space group Pm3 m across in the composition range of 0.6 ≤ x ≤ 1. • Perovskite films exhibit a very high absorbance in the visible and short infrared. • As the fraction of bromide change, the adsorption edge of thin film perovskite can be tuned along the visible spectrum from 543 nm to 785 nm. • The incorporating of bromide into MAPbI{sub 3−x}Br{sub x} shifts the PL emission to shorter wavelengths. - Abstract: Mixed bromide iodide lead perovskites were prepared from methylamine, lead nitrate and the corresponding hydroX acid (X = I, Br), they were then deposited as thin films on ITO substrate by the spin coating process. X-ray diffraction analyses indicated the formation of a tetragonal phase I4/mcm up to x = 0.4 and a cubic perovskite with space group Pm3 m in the composition range of 0.6 ≤ x ≤ 1. Mixed lead perovskites showed a high absorbance in the UV–vis range. The band gap energy of thin films were estimated from absorbance spectral measurements, it was found that the onset of the absorption edge for MAPbI{sub 3−x}Br{sub x} (x < 1) thin films is ranging between 1.58 to 1.72 eV. Photoluminescence emission energies for mixed halide perovskites presented intermediate values from 781 nm (MAPbI{sub 3}) to 545 nm (MAPbBr{sub 3}).

  11. Cs 1x Rb x PbCl 3 and Cs 1x Rb x PbBr 3 Solid Solutions: Understanding Octahedral Tilting in Lead Halide Perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Linaburg, Matthew R.; McClure, Eric T.; Majher, Jackson D.; Woodward, Patrick M.

    2017-04-03

    The structures of the lead halide perovskites CsPbCl3 and CsPbBr3 have been determined from X-ray powder diffraction data to be orthorhombic with Pnma space group symmetry. Their structures are distorted from the cubic structure of their hybrid analogs, CH3NH3PbX3 (X = Cl, Br), by tilts of the octahedra (Glazer tilt system a–b+a–). Substitution of the smaller Rb+ for Cs+ increases the octahedral tilting distortion and eventually destabilizes the perovskite structure altogether. To understand this behavior, bond valence parameters appropriate for use in chloride and bromide perovskites have been determined for Cs+, Rb+, and Pb2+. As the tolerance factor decreases, the band gap increases, by 0.15 eV in Cs1–xRbxPbCl3 and 0.20 eV in Cs1–xRbxPbBr3, upon going from x = 0 to x = 0.6. The band gap shows a linear dependence on tolerance factor, particularly for the Cs1–xRbxPbBr3 system. Comparison with the cubic perovskites CH3NH3PbCl3 and CH3NH3PbBr3 shows that the band gaps of the methylammonium perovskites are anomalously large for APbX3 perovskites with a cubic structure. This comparison suggests that the local symmetry of CH3NH3PbCl3 and CH3NH3PbBr3 deviate significantly from the cubic symmetry of the average structure.

  12. Association Between Severe Vitamin D Deficiency, Lung Function and Asthma Control.

    Science.gov (United States)

    Beyhan-Sagmen, Seda; Baykan, Ozgur; Balcan, Baran; Ceyhan, Berrin

    2017-04-01

    To examine the relationship between severe vitamin D deficiency, asthma control, and pulmonary function in Turkish adults with asthma. One hundred six asthmatic patients underwent pulmonary function tests skin prick test, peripheral blood eosinophil counts, IgE, body mass index and vitamin D levels were determined. Patients were divided into 2 subgroups according to vitamin D levels (vitamin D level<10ng/ml and vitamin D level≥10 ng/ml). Asthma control tests were performed. The mean age of subgroup i (vitamin D level<10) was 37±10 and the mean age of subgroup ii (vitamin D level≥10ng/ml) was 34±8. Sixty-six percent of patients had severe vitamin D deficiency (vitamin D level<10 ng/ml). There was a significant trend towards lower absolute FEV 1 (L) values in patients with lower vitamin D levels (P=.001). Asthma control test scores were significantly low in the severe deficiency group than the other group (P=.02). There were a greater number of patients with uncontrolled asthma (asthma control test scores<20) in the severe vitamin D deficiency group (P=.040). Patients with severe vitamin D deficiency had a higher usage of inhaled corticosteroids than the group without severe vitamin D deficiency (P=.015). There was a significant trend towards lower absolute FEV 1 (L) (P=.005, r=.272) values in patients with lower vitamin D levels. Vitamin D levels were inversely related with body mass index (P=.046). The incidence of severe vitamin D deficiency was high in adult Turkish asthmatics. In addition, lower vitamin D levels were associated with poor asthma control and decreased pulmonary function. Copyright © 2016 SEPAR. Publicado por Elsevier España, S.L.U. All rights reserved.

  13. Crystallographic Investigations into Properties of Acentric Hybrid Perovskite Single Crystals NH(CH3)3SnX3(X = Cl, Br)

    KAUST Repository

    Dang, Yangyang; Zhong, Cheng; Zhang, Guodong; Ju, Dianxing; Wang, Lei; Xia, Shengqing; Xia, Haibing; Tao, Xutang

    2016-01-01

    substitute for the lead in the halides perovskites and solving the ambiguous crystal structures and phase transition of NH(CH3)3SnX3 (X = Cl, Br). Here, we report the bulk crystal growths and different crystal morphologies of orthorhombic hybrid perovskites

  14. Single-crystal perovskite CH3NH3PbBr3 prepared by cast capping method for light-emitting diodes

    Science.gov (United States)

    Nguyen, Van-Cao; Katsuki, Hiroyuki; Sasaki, Fumio; Yanagi, Hisao

    2018-04-01

    In this study, electroluminescence from single crystals of CH3NH3PbBr3 perovskite is explored. The cast capping method was applied to fabricate simple devices with an ITO/CH3NH3PbBr3/ITO structure. The devices showed a low operation voltage of 2 V and a pure green luminescence with full width at half maximum of ∼20 nm. However, the emission occurring at the crystal edges demonstrated blinking with a subsecond time interval, which is similar to the previously reported photoluminescence behavior of nanocrystal perovskites. This electroluminescence blinking may provide new insight into the recombination processes depending on the carrier traps and defects of emission layers in perovskite light-emitting devices.

  15. Synthesis of 25-hydroxy-[26,27-3H]vitamin D2, 1,25-dihydroxy-[26,27-3H]vitamin D2 and their (24R)-epimers

    International Nuclear Information System (INIS)

    Sicinski, R.R.; Tanaka, Y.; Phelps, M.; Schnoes, H.K.; DeLuca, H.F.

    1987-01-01

    Synthesis of a C-24-epimeric mixture of 25-hydroxy-[26,27- 3 H]vitamin D2 and a C-24-epimeric mixture of 1,25-dihydroxy-[26,27- 3 H]vitamin D2 by the Grignard reaction of the corresponding 25-keto-27-nor-vitamin D2 and 1 alpha-acetoxy-25-keto-27-nor-vitamin D3 with tritiated methyl magnesium bromide is described. Separation of epimers by high-performance liquid chromatography afforded pure radiolabeled vitamins of high specific activity (80 Ci/mmol). The identities and radiochemical purities of 25-hydroxy-[26,27- 3 H[vitamin D2 and 1,25-dihydroxy-[26,27- 3 H]vitamin D2 D2 were established by cochromatography with synthetic 25-hydroxyvitamin D2 or 1,25-dihydroxyvitamin D2. Biological activity of 25-hydroxy-[26,27- 3 H]vitamin D2 was demonstrated by its binding to the rat plasma binding protein for vitamin D compounds, and by its in vitro conversion to 1,25-dihydroxy-[26,27- 3 H]vitamin D2 by kidney homogenate prepared from vitamin D-deficient chickens. The biological activity of 1,25-dihydroxy-[26,27- 3 H]vitamin D2 was demonstrated by its binding to the chick intestinal receptor for 1,25-dihydroxyvitamin D3

  16. Influence of the sintering temperature on the Sr content in a Ca{sub (1−x−y)}Ce{sub x}Sr{sub y}Al{sub z}Ti{sub (1−z)}O{sub 3} perovskite (x = 0.04–0.16) co-doped with Ce

    Energy Technology Data Exchange (ETDEWEB)

    Kamel, Nour-el-hayet; Mouheb, Yasmina, E-mail: mouhebyascrna@hotmail.com; Kamel, Ziane; Moudir, Dalila; Aouchiche, Fairouz; Arabi, Azeddine

    2016-08-15

    A Sr-Ce co-doped perovskite, with the chemical formula: Ca{sub (1−x−y)}Ce{sub x}Sr{sub y}Al{sub z}Ti{sub (1−z)}O{sub 3} (y = 0.04, 0.08, 0.12 and 0.16, x = 0.05) is synthesized by sol–gel process. The influence of the sintering temperature, Ts, on the rate of inserted Sr was investigated at 1223, 1373 and 1473 K. The Sr amount sequestered in the perovskite reaches 85% (y = 0.16, 9.50 wt%) for Ts = 1373 K, giving sintering densities between 3.520 and 4.400. XRD analysis reveals an orthorhombic CaTiO{sub 3} structure. The lattice parameters obey to Vegard’s law for Ts = 1373 and 1473 K. SEM analysis shows orthorhombic grains of 0.514 μm × 1 μm mean dimensions. MCC1 and MCC2 tests, performed on minerals sintered at 1373 K, indicate that the most durable one is that containing 9.50 wt% Sr. MCC1 test gave 6.998·10{sup −6} g/cm{sup 2} d of Sr, and MCC2 2.143·10{sup −4} g/cm{sup 2} d of Ce. The temperature favors the Sr dissolution to the detriment of Ce. The Ca dissolution rate reaches 1.002·10{sup −6} to 2.005·10{sup −6} g/cm{sup 2} d. - Highlights: • Ca{sub (1−x−y)}Ce{sub x}Sr{sub y}Al{sub z}Ti{sub (1−z)}O{sub 3} perovskite is synthesized by sol–gel. • The influence of the sintering temperature, Ts, on the rate of inserted Sr was investigated at 1223, 1373 and 1473 K. • 85% of total Sr was sequestered in the perovskite for Ts = 1373 K. • MCC1 and MCC2 leach tests indicate that the most durable mineral is that containing 9.50 wt.% Sr. • MCC1 test gave 8.10 10{sup −10} kg/m{sup 2}.d Sr. The lower is the leaching temperature the higher is the mineral durability.

  17. Hexagonal perovskites with cationic vacancies. 5. Structure determination on H-Ba/sub 2/Lusub(2/3)vacantsub(1/3)WO/sub 6/ - a novel rhombohedral stacking polytype with 18 layers

    Energy Technology Data Exchange (ETDEWEB)

    Wischert, W; Schittenhelm, H J; Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Inst. fuer Chemie

    1979-01-01

    Compounds of type Ba/sub 2/Bsub(2/3)sup(III)vacantsub(1/3)Wsup(VI)O/sub 6/ with Bsup(III) = Gd-Lu, Y are polymorphic. They crystallize in a cubic 1:1 ordered perovskite structure and in a new rhombohedral perovskite stacking polytype of 18 L respectively. By intensity calculations out of the three possible stacking sequences (4)(2), (5)(1) and (3)1(1)1 (all space group R3m) the sequence (5)(1) can be selected. For H-Ba/sub 2/Lusub(2/3)vacant sub(1/3)WO/sub 6/ the refined R' factor is 14.1%. The structure contains groups of three octahedra connected with another by common faces which are linked with each other by three corner sharing octahedra. In the block of three face sharing octahedra the central octahedral lattice site is vacant, the two outer positions are occupied by tungsten atoms. According to this distribution a direct contact of occupied face sharing octahedra is absent.

  18. Perovskite nanocrystals: across-dimensional attachment, film-scale assembly on a flexible substrate and their fluorescence properties

    Science.gov (United States)

    Huang, Wenyi; Liu, Jiajia; Bai, Bing; Huang, Liu; Xu, Meng; Liu, Jia; Rong, Hongpan; Zhang, Jiatao

    2018-03-01

    Perovskite nanocrystals (NCs), which are a good fluorescence candidate with excellent photoelectric properties, have opened new avenues in the fabrication of highly efficient solar cells, light-emitting diodes (LEDs), and other optoelectronic devices. Further advances will rely on the multitude of compositional, structural variants that enable the formation of lower-dimensionality layered and three-dimensional (3D) perovskites with architectural innovations. In this work, the perovskite film was fabricated on a flexible substrate using simple dip-coating technology and 3D assemblies of perovskite NCs were obtained through an attachment process. Original perovskite NCs had a rectangular or square morphology with high particle uniformity and the narrow and symmetric fluorescence emission peak was adjustable at 515-527 nm. The controllable self-assembly of the micron size cuboid-like 3D assembly had an apparent enhancement on peak (111) in the x-ray diffraction (XRD) pattern. Surface ligands not only play a role in the attachment process but also keep the independence of each NC in 3D assemblies. Such assembly of the perovskite film maintained the original perovskite NCs fluorescence emission peak and narrow full width at the half-maximum (FWHM), which is of great importance for the investigation of future devices.

  19. High-Dose versus Low-Dose Vitamin D Supplementation and Arterial Stiffness among Individuals with Prehypertension and Vitamin D Deficiency

    Directory of Open Access Journals (Sweden)

    Amanda Zaleski

    2015-01-01

    Full Text Available Introduction. Vitamin D deficiency is associated with the onset and progression of hypertension and cardiovascular disease (CVD. However, mechanisms underlying vitamin D deficiency-mediated increased risk of CVD remain unknown. We sought to examine the differential effect of high-dose versus low-dose vitamin D supplementation on markers of arterial stiffness among ~40 vitamin D deficient adults with prehypertension. Methods. Participants were randomized to high-dose (4000 IU/d versus low-dose (400 IU/d oral vitamin D3 for 6 months. 24 hr ambulatory blood pressure (BP, carotid-femoral pulse wave velocity, and pulse wave analyses were obtained at baseline and after 6 months of vitamin D supplementation. Results. There were no changes in resting BP or pulse wave velocity over 6 mo regardless of vitamin D dose (all p>0.202. High-dose vitamin D decreased augmentation index and pressure by 12.3 ± 5.3% (p=0.047 and 4.0 ± 1.5 mmHg (p=0.02, respectively. However, these decreases in arterial stiffness were not associated with increases in serum 25-hydroxyvitamin D over 6 mo (p=0.425. Conclusion. High-dose vitamin D supplementation appears to lower surrogate measures of arterial stiffness but not indices of central pulse wave velocity. Clinical Trial Registration. This trial is registered with www.clinicaltrials.gov (Unique Identifier: NCT01240512.

  20. Vitamin D Deficiency and Lower Urinary Tract Symptoms in Women.

    Science.gov (United States)

    Aydogmus, H; Demirdal, U S

    2018-06-09

    The association of vitamin D deficiency and pelvic floor dysfunction has been examined by numerous studies. Lower urinary tract symptoms (LUTS) associated with bladder filling and voiding functions are common in both sexes. A recent study reports a higher incidence of LTUS in men over 50 years old with vitamin D deficiency. The aim of the study is to investigate whether there is a difference in the Lower Urinary Tract Symptoms frequency between women with vitamin D deficiency and the control group or not. In this case control study, a total of 150 women who had a measured vitamin D level within a month were divided into two groups, one with a serum vitamin D deficiency and the other with a normal vitamin D level. Both groups were evaluated in terms of menopausal status, numbers of pregnancy and delivery, pelvic examination findings, pelvic floor muscle strength, level of pelvic organ prolapse, LUTS scores, and the findings were recorded. Both groups were compared for the presence of lower urinary system symptoms. The BFLUTS validated for Turkish-speaking populations was used to assess lower urinary system symptoms. Statistical analyses were performed via IBM SPSS Statistics 23.0. The results were considered significant at p D deficiency was detected in 67.3% of the participants. No significant differences were found between the groups regarding variables that could affect lower urinary system symptoms such as menopausal status, presence of pelvic organ prolapse and neonatal weight (fetal macrosomia) The Pelvic Floor Muscle Strength was significantly lower in the group with vitamin D deficiency than the control group. BFLUTS scores of premenopausal women with vitamin D deficiency were found to be similar to the control group, likewise no significant differences in the BFLUTS scores were detected in postmenopausal women. Although vitamin D deficiency causes a significant reduction in pelvic floor muscle strength, no significant correlation was found between lower

  1. Conducting tin halides with a layered organic-based perovskite structure

    Science.gov (United States)

    Mitzi, D. B.; Feild, C. A.; Harrison, W. T. A.; Guloy, A. M.

    1994-06-01

    THE discovery1 of high-temperature superconductivity in layered copper oxide perovskites has generated considerable fundamental and technological interest in this class of materials. Only a few other examples of conducting layered perovskites are known; these are also oxides such as (La1-xSrx)n+1 MnnO3n+1 (ref. 2), Lan+1NinO3n+1 (ref. 3) and Ban+1PbnO3n+1 (ref. 4), all of which exhibit a trend from semiconducting to metallic behaviour with increasing number of perovskite layers (n). We report here the synthesis of a family of organic-based layered halide perovskites, (C4H9NH3)2(CH3NH3)n-1Snnl3n+1 which show a similar transition from semiconducting to metallic behaviour with increasing n. The incorporation of an organic modulation layer between the conducting tin iodide sheets potentially provides greater flexibility for tuning the electrical properties of the perovskite sheets, and we suggest that such an approach will prove valuable for exploring the range of transport properties possible with layered perovskites.

  2. Efficient Generation of Long-Lived Triplet Excitons in 2D Hybrid Perovskite.

    Science.gov (United States)

    Younts, Robert; Duan, Hsin-Sheng; Gautam, Bhoj; Saparov, Bayrammurad; Liu, Jie; Mongin, Cedric; Castellano, Felix N; Mitzi, David B; Gundogdu, Kenan

    2017-03-01

    Triplet excitons form in quasi-2D hybrid inorganic-organic perovskites and diffuse over 100 nm before radiating with >11% photoluminescence quantum efficiency (PLQE) at low temperatures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Interfacial Interactions in Monolayer and Few-Layer SnS/CH3 NH3 PbI3 Perovskite van der Waals Heterostructures and Their Effects on Electronic and Optical Properties.

    Science.gov (United States)

    Li, Jian-Cai; Wei, Zeng-Xi; Huang, Wei-Qing; Ma, Li-Li; Hu, Wangyu; Peng, Ping; Huang, Gui-Fang

    2018-02-05

    A high light-absorption coefficient and long-range hot-carrier transport of hybrid organic-inorganic perovskites give huge potential to their composites in solar energy conversion and environmental protection. Understanding interfacial interactions and their effects are paramount for designing perovskite-based heterostructures with desirable properties. Herein, we systematically investigated the interfacial interactions in monolayer and few-layer SnS/CH 3 NH 3 PbI 3 heterostructures and their effects on the electronic and optical properties of these structures by density functional theory. It was found that the interfacial interactions in SnS/CH 3 NH 3 PbI 3 heterostructures were van der Waals (vdW) interactions, and they were found to be insensitive to the layer number of 2D SnS sheets. Interestingly, although their band gap decreased upon increasing the layer number of SnS, the near-gap electronic states and optical absorption spectra of these heterostructures were found to be strikingly similar. This feature was determined to be critical for the design of 2D layered SnS-based heterostructures. Strong absorption in the ultraviolet and visible-light regions, type II staggered band alignment at the interface, and few-layer SnS as an active co-catalyst make 2D SnS/CH 3 NH 3 PbI 3 heterostructures promising candidates for photocatalysis, photodetectors, and solar energy harvesting and conversion. These results provide first insight into the nature of interfacial interactions and are useful for designing hybrid organic-inorganic perovskite-based devices with novel properties. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Organic-Inorganic Perovskites: Structural Versatility for Functional Materials Design.

    Science.gov (United States)

    Saparov, Bayrammurad; Mitzi, David B

    2016-04-13

    Although known since the late 19th century, organic-inorganic perovskites have recently received extraordinary research community attention because of their unique physical properties, which make them promising candidates for application in photovoltaic (PV) and related optoelectronic devices. This review will explore beyond the current focus on three-dimensional (3-D) lead(II) halide perovskites, to highlight the great chemical flexibility and outstanding potential of the broader class of 3-D and lower dimensional organic-based perovskite family for electronic, optical, and energy-based applications as well as fundamental research. The concept of a multifunctional organic-inorganic hybrid, in which the organic and inorganic structural components provide intentional, unique, and hopefully synergistic features to the compound, represents an important contemporary target.

  5. Vitamin D Deficiency and Cardiometabolic Risks: A Juxtaposition of Arab Adolescents and Adults.

    Directory of Open Access Journals (Sweden)

    Nasser M Al-Daghri

    Full Text Available The recent exponential surge in vitamin D research reflects the global epidemic of vitamin D deficiency and its potential impact on several chronic diseases in both children and adults. Several subpopulations, including Arab adolescent boys and girls, remain understudied. This study aims to fill this gap. A total of 2225 apparently healthy Saudi adolescents (1187 boys and 1038 girls, aged 13-17 years old and 830 adults (368 men and 462 women, aged 18-50 years old were respectively recruited from different public schools and medical practices within Riyadh, Saudi Arabia. Anthropometrics were taken and fasting blood samples withdrawn to examine serum glucose and lipid profile by routine analysis and 25-hydroxyvitamin D by ELISA. Almost half of the girls (47.0% had vitamin D deficiency as compared to only 19.4% of the boys (p<0.001, 36.8% of the adult women and 17.7% of the adult men (p<0.001. Furthermore, in boys there were more significant inverse associations between serum 25(OHvitamin D levels and cardiometabolic indices than girls, while in contrast women had more significant associations than men. Vitamin D deficiency was significantly associated with diabetes mellitus type 2 (DMT2 [OR 3.47 (CI1.26-5.55; p<0.05] and pre-DM [OR 2.47 (CI 1.48-4.12; p<0.01] in boys. Furthermore, vitamin D insufficiency was significantly associated with abdominal obesity in boys [OR 2.75 (CI 1.1-7.1; p<0.05]. These associations for DMT2 and abdominal obesity were not observed in adult males, girls and adult women. Vitamin D deficiency/insufficiency and hyperglycemia is high among Arab adolescents. Vitamin D deficiency is mostly associated with cardiometabolic risk factors in adolescent Arab boys. This indicates a sex- and age-related disadvantage for boys with low vitamin D status and challenges the extra-skeletal protection of vitamin D correction in adolescent females.

  6. Conducting Layered Organic-inorganic Halides Containing -Oriented Perovskite Sheets.

    Science.gov (United States)

    Mitzi, D B; Wang, S; Feild, C A; Chess, C A; Guloy, A M

    1995-03-10

    Single crystals of the layered organic-inorganic perovskites, [NH(2)C(I=NH(2)](2)(CH(3)NH(3))m SnmI3m+2, were prepared by an aqueous solution growth technique. In contrast to the recently discovered family, (C(4)H(9)NH(3))(2)(CH(3)NH(3))n-1SnnI3n+1, which consists of (100)-terminated perovskite layers, structure determination reveals an unusual structural class with sets of m -oriented CH(3)NH(3)SnI(3) perovskite sheets separated by iodoformamidinium cations. Whereas the m = 2 compound is semiconducting with a band gap of 0.33 +/- 0.05 electron volt, increasing m leads to more metallic character. The ability to control perovskite sheet orientation through the choice of organic cation demonstrates the flexibility provided by organic-inorganic perovskites and adds an important handle for tailoring and understanding lower dimensional transport in layered perovskites.

  7. Role of bromine doping on the photovoltaic properties and microstructures of CH{sub 3}NH{sub 3}PbI{sub 3} perovskite solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Atsushi; Okada, Hiroshi; Oku, Takeo [Department of Materials Science, The University of Shiga Prefecture 2500 Hassaka, Hikone, Shiga, 522-8533 (Japan)

    2016-02-01

    Organic-inorganic hybrid heterojunction solar cells containing CH{sub 3}NH{sub 3}PbI{sub 3} perovskite compound were fabricated using mesoporous TiO{sub 2} as the electronic transporting layer and spirobifluorence as the hole-transporting layer. The purpose of the present study is to investigate role of bromine (Br) doping on the photovoltaic properties and microstructure of CH{sub 3}NH{sub 3}PbI{sub 3} perovskite solar cells. Photovoltaic, optical properties and microstructures of perovskite-based solar cells were investigated. The X-ray diffraction identified crystal structure of the perovskite layer doped with Br in the solar cell. Scanning electron microscopy observation showed a different behavior of surface morphology and the perovskite crystal structure on the TiO{sub 2} mesoporous structure depending on extent amount of hydrogen doping of Br. The role of bromide halogen doping on the perovskite crystal structure and photovoltaic properties was due to improvement of carrier mobility, optimization of electron structure, band gap related with the photovoltaic parameters of V{sub oc}, J{sub sc} and η. Energy diagram and photovoltaic mechanism of the perovskite solar cells varied with halogen doping was discussed by experimental results.

  8. Critical reappraisal of vitamin D deficiency.

    Science.gov (United States)

    Audran, Maurice; Briot, Karine

    2010-03-01

    The current surge of interest in vitamin D is fuelled not only by evidence that vitamin D supplementation decreases the risk of osteoporotic fractures but also by vast observational studies indicating a variety of beneficial extraskeletal effects (including decreases in the risks of cancer, inflammatory diseases, and even death). Serum 25-hydroxyvitamin D (25(OH)D) assay is now a highly reliable method for evaluating vitamin D stores in individual patients. Nevertheless, the normal or desirable 25(OH)D range for patients seen in everyday clinical practice needs to be more accurately defined. Maintaining serum 25(OH)D above 75 nmol/L is currently recommended to ensure optimal bone health, but higher levels may be required to obtain some of the extraskeletal benefits. Naturally occurring vitamin D is by far the most widely used form for correcting vitamin D deficiency, and the hydroxylated derivatives have only a few highly specific indications. However, controversy persists about the optimal modalities of natural vitamin D supplementation in terms of the type of vitamin (D2 or D3), schedule (once daily or at wider intervals), and route (oral or injectable). For chronic supplementation to protect against bone loss, a daily dosage of at least 800 IU seems required. Higher dosages (e.g., 100,000 to 200,000 IU every 2 months for 6 months) may be needed to correct established vitamin D deficiency; a repeat 25(OH)D assay after 4 to 6 months may help to assess the treatment response and to adjust the subsequent vitamin D dosage. The current emphasis is on the detection of vitamin D deficiency in the general population and in subgroups at risk for osteoporosis followed by an assessment of severity and the initiation of appropriate treatment. From a public health perspective, supplying at least 800 IU per day seems useful and safe. Copyright 2010 Société française de rhumatologie. Published by Elsevier SAS. All rights reserved.

  9. Vitamin D Deficiency

    Science.gov (United States)

    ... to other diseases. In children, it can cause rickets. Rickets is a rare disease that causes the bones ... and children are at higher risk of getting rickets. In adults, severe vitamin D deficiency leads to ...

  10. Pressure-induced amorphization of La1/3TaO3

    International Nuclear Information System (INIS)

    Noked, O.; Melchior, A.; Shuker, R.; Livneh, T.; Steininger, R.; Kennedy, B.J.; Sterer, E.

    2013-01-01

    La 1/3 TaO 3 , an A-site cation deficient perovskite, has been studied under pressure by synchrotron X-ray powder diffraction and Raman spectroscopy. It undergoes irreversible pressure induced amorphization at P=18.5 GPa. An almost linear unit cell volume decrease vs. pressure is observed from ambient pressure up to the phase transition. The Raman spectroscopy also shows amorphization at the same pressure, with positive shifts of all modes as a function of pressure. The pressure dependence of the E g and A 1g Raman modes arising from the octahedral oxygen network is discussed. - Graphical abstract: La 1/3 Tao 3 exhibits linear pressure–volume relation until irreversible pressure induced amorphization at 18.5 Gpa. - Highlights: • La 1/3 TaO 3 has been studied under pressure by synchrotron XRD and Raman spectroscopy. • La 1/3 TaO 3 undergoes irreversible pressure induced amorphization around 18.5 GPa. • The transition is manifested in both XRD and Raman measurements. • A linear P–V relation is observed from ambient pressure up to the phase transition

  11. Dielectric properties of hybrid perovskites and drift-diffusion modeling of perovskite cells

    Science.gov (United States)

    Pedesseau, L.; Kepenekian, M.; Sapori, D.; Huang, Y.; Rolland, A.; Beck, A.; Cornet, C.; Durand, O.; Wang, S.; Katan, C.; Even, J.

    2016-03-01

    A method based on DFT is used to obtained dielectric profiles. The high frequency Ɛ∞(z) and the static Ɛs(z) dielectric profiles are compared for 3D, 2D-3D and 2D Hybrid Organic Perovskites (HOP). A dielectric confinement is observed for the 2D materials between the high dielectric constant of the inorganic part and the low dielectric constant of the organic part. The effect of the ionic contribution on the dielectric constant is also shown. The quantum and dielectric confinements of 3D HOP nanoplatelets are then reported. Finally, a numerical simulation based on the SILVACO code of a HOP based solar cell is proposed for various permittivity of MAPbI3.

  12. Planar structured perovskite solar cells by hybrid physical chemical vapor deposition with optimized perovskite film thickness

    Science.gov (United States)

    Wei, Xiangyang; Peng, Yanke; Jing, Gaoshan; Cui, Tianhong

    2018-05-01

    The thickness of perovskite absorber layer is a critical parameter to determine a planar structured perovskite solar cell’s performance. By modifying the spin coating speed and PbI2/N,N-dimethylformamide (DMF) solution concentration, the thickness of perovskite absorber layer was optimized to obtain high-performance solar cells. Using a PbI2/DMF solution of 1.3 mol/L, maximum power conversion efficiency (PCE) of a perovskite solar cell is 15.5% with a perovskite film of 413 nm at 5000 rpm, and PCE of 14.3% was also obtained for a solar cell with a perovskite film of 182 nm thick. It is derived that higher concentration of PbI2/DMF will result in better perovskite solar cells. Additionally, these perovskite solar cells are highly uniform. In 14 sets of solar cells, standard deviations of 11 sets of solar cells were less than 0.50% and the smallest standard deviation was 0.25%, which demonstrates the reliability and effectiveness of hybrid physical chemical vapor deposition (HPCVD) method.

  13. Rh promoted La0.75Sr0.25(Fe0.8Co0.2)1−xGaxO3perovskite catalysts: Characterization and catalytic performance for methane partial oxidation to synthesis gas

    International Nuclear Information System (INIS)

    Palcheva, R.; Olsbye, U.; Palcut, M.; Rauwel, P.; Tyuliev, G.; Velinov, N.; Fjellvåg, H.H.

    2015-01-01

    Graphical abstract: - Highlights: • Perovskites type-oxide La 0.75 Sr 0.25 (Fe 0.8 Co 0.2 ) 1−x Ga x O 3-δ (x = 0.1, 0.25, 0.4) prepared by the sol–gel citrate method. • Bulk and surface analysis to determine catalysts composition evolution. • Anaerobic catalytic partial oxidation of methane to syngas at 600 °C in a pulse apparatus over Rh promoted perovskites. • The catalysts showed high stability and selectivity. - Abstract: Synthesis gas production via selective oxidation of methane at 600 °C in a pulse reaction over La 0.75 Sr 0.25 (Fe 0.8 Co 0.2 ) 1−x Ga x O 3-δ (x = 0.1, 0.25, 0.4) perovskite-supported rhodium catalysts, was investigated. The perovskite oxides were prepared by sol–gel citrate method and characterized by X-ray Diffraction (XRD), Moessbauer Spectroscopy (MS), Temperature Programmed Reduction (TPR-H 2 ), X-ray Photoelectron Spectroscopy (XPS) and High Resolution Transmission Electron Microscopy (HRTEM). According to XRD analysis, the synthesized samples were a single perovskite phase. The perovskite structure of Ga substituted samples remained stable after TPR-H 2 , as confirmed by XRD. Data of MS identified Fe 3+ ions in two distinctive coordination environments, and Fe 4+ ions. The Rh 2 O 3 thin overlayer was detected by the HRTEM for the Rh impregnated perovskite oxides. During the interaction of methane with oxidized perovskite-supported Rh (0.5 wt.%) catalysts, besides CO, H 2 , and surface carbon, CO 2 and H 2 O were formed. The Rh perovskite catalyst with x = 0.25 gallium exhibits the highest catalytic activity of 83% at 600 °C. The CO selectivity was affected by the reducibility of La 0.75 Sr 0.25 (Fe 0.8 Co 0.2 ) 1−x Ga x O 3perovskite materials.

  14. Catalytic N 2O decomposition on Pr 0.8Ba 0.2MnO 3 type perovskite catalyst for industrial emission control

    Czech Academy of Sciences Publication Activity Database

    Kumar, S.; Vinu, A.; Šubrt, Jan; Bakardjieva, Snejana; Rayalu, S.; Teraoka, Y.; Labhsetwar, N.

    2012-01-01

    Roč. 198, 1-SI (2012), s. 125-132 ISSN 0920-5861 R&D Projects: GA MŠk LC523 Institutional support: RVO:61388980 Keywords : Ba substituted perovskite * catalyst * honeycomb * N 2O decomposition * perovskite * praseodymium manganate Subject RIV: CA - Inorganic Chemistry Impact factor: 2.980, year: 2012

  15. Synthesis under pressure and characterizations through optical spectroscopy of jahn-teller cations (LS Ni3+, is Co3+) as probes diluted in a perovskite matrix

    Science.gov (United States)

    Sanz-Ortiz, M. N.; Rodríguez, F.; Baranov, A.; Demazeau, G.

    2008-07-01

    The objective is to explore through optical spectroscopy and magnetic measurements the coordination and electronic structures of transition-metal ions introduced as impurities with unusual valence states in the oxide perovskite LaAlO3. The selected transition-metal ions Ni3+(3d7) and Co3+(3d6) are characterized by an electronic configuration likely leading to an orbital degenerate E state in Oh symmetry, and thus electron-lattice coupling due to the Jahn-Teller effect may induce low symmetry distortion around the impurity oxygen octahedron. We show that a sol-gel process followed by high oxygen pressure treatments yields stabilization of trivalent state in oxide perovskite. Information about the coordination, electronic structure and aggregation around the magnetic impurity was obtained from X-ray diffraction, FTIR and optical spectroscopy. Finally, evidence on the possible existence of intermediate spin state in Co3+ is under consideration.

  16. Synthesis under pressure and characterizations through optical spectroscopy of jahn-teller cations (LS Ni3+, is Co3+) as probes diluted in a perovskite matrix

    International Nuclear Information System (INIS)

    Sanz-Ortiz, M N; RodrIguez, F; Baranov, A; Demazeau, G

    2008-01-01

    The objective is to explore through optical spectroscopy and magnetic measurements the coordination and electronic structures of transition-metal ions introduced as impurities with unusual valence states in the oxide perovskite LaAlO 3 . The selected transition-metal ions Ni 3+ (3d 7 ) and Co 3+ (3d 6 ) are characterized by an electronic configuration likely leading to an orbital degenerate E state in Oh symmetry, and thus electron-lattice coupling due to the Jahn-Teller effect may induce low symmetry distortion around the impurity oxygen octahedron. We show that a sol-gel process followed by high oxygen pressure treatments yields stabilization of trivalent state in oxide perovskite. Information about the coordination, electronic structure and aggregation around the magnetic impurity was obtained from X-ray diffraction, FTIR and optical spectroscopy. Finally, evidence on the possible existence of intermediate spin state in Co 3+ is under consideration

  17. Using Low Temperature Photoluminescence Spectroscopy to Investigate CH3NH3PbI3 Hybrid Perovskite Degradation

    Directory of Open Access Journals (Sweden)

    Khaoula Jemli

    2016-07-01

    Full Text Available Investigating the stability and evaluating the quality of the CH3NH3PbI3 perovskite structures is quite critical both to the design and fabrication of high-performance perovskite devices and to fundamental studies of the photophysics of the excitons. In particular, it is known that, under ambient conditions, CH3NH3PbI3 degrades producing some PbI2. We show here that low temperature Photoluminescence (PL spectroscopy is a powerful tool to detect PbI2 traces in hybrid perovskite layers and single crystals. Because PL spectroscopy is a signal detection method on a black background, small PbI2 traces can be detected, when other methods currently used at room temperature fail. Our study highlights the extremely high stability of the single crystals compared to the thin layers and defects and grain boundaries are thought to play an important role in the degradation mechanism.

  18. Magnetic and Electric Properties of , ( Layered Perovskites

    Directory of Open Access Journals (Sweden)

    A. I. Ali

    2013-01-01

    Full Text Available The electric and magnetic properties of layered perovskites have been investigated systematically over the doping range . It was found that both Sr1.5Y0.5CoO4 and Sr1.4Y0.6CoO4 undergo ferromagnetic (FM transition around 145 K and 120 K, respectively. On the other hand, Sr1.3Y0.7CoO4 and Sr1.2Y0.8CoO4 compounds showed paramagnetic behavior over a wide range of temperatures. In addition, spin-glass transition ( was observed at 10 K for Sr1.3Y0.7CoO4. All investigated samples are semiconducting-like within the temperature range of 10–300 K. The temperature dependence of the electrical resistivity, , was described by two-dimensional variable range hopping (2D-VRH model at 50 K < ≤ 300 K. Comparison with other layered perovskites was discussed in this work.

  19. Nanocrystalline La1-xSrxCo1-yFe yO3 perovskites fabricated by the micro-emulsion route for high frequency response devices fabrications

    KAUST Repository

    Azhar Khan, Muhammad

    2014-09-01

    Nanocrystalline La1-xSrxCo1-yFe yO3 (x=0.00-0.60) perovskites were fabricated by a cheap economic route (i.e. micro-emulsion method) and characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). TGA analysis showed ~35% weight loss. The crystallite size determined by XRD and SEM ranged from 30 to 80 nm and ~30 to 50 nm, respectively. The dielectric behavior was evaluated in the range of 1.0×106 Hz to 3.0×10 9 Hz at 298 K, the dielectric parameters resulting appreciably enhanced by co-doping with Sr and Fe. The maximum dielectric parameters (ε′=103.35, ε″=58.92 and tan δ=0.57) were observed for La0.4Sr0.6Co0.4Fe0.6O 3 at 15×106 Hz. Results suggest the potential use of these nanocrystalline perovskites in GHz-operated microwave devices. © 2014 Elsevier Ltd and Techna Group S.r.l.

  20. Anomalous perovskite PbRuO3 stabilized under high pressure

    Science.gov (United States)

    Cheng, J.-G.; Kweon, K. E.; Zhou, J.-S.; Alonso, J. A.; Kong, P.-P.; Liu, Y.; Jin, Changqing; Wu, Junjie; Lin, Jung-Fu; Larregola, S. A.; Yang, Wenge; Shen, Guoyin; MacDonald, A. H.; Manthiram, Arumugam; Hwang, G. S.; Goodenough, John B.

    2013-01-01

    Perovskite oxides ABO3 are important materials used as components in electronic devices. The highly compact crystal structure consists of a framework of corner-shared BO6 octahedra enclosing the A-site cations. Because of these structural features, forming a strong bond between A and B cations is highly unlikely and has not been reported in the literature. Here we report a pressure-induced first-order transition in PbRuO3 from a common orthorhombic phase (Pbnm) to an orthorhombic phase (Pbn21) at 32 GPa by using synchrotron X-ray diffraction. This transition has been further verified with resistivity measurements and Raman spectra under high pressure. In contrast to most well-studied perovskites under high pressure, the Pbn21 phase of PbRuO3 stabilized at high pressure is a polar perovskite. More interestingly, the Pbn21 phase has the most distorted octahedra and a shortest Pb—Ru bond length relative to the average Pb—Ru bond length that has ever been reported in a perovskite structure. We have also simulated the behavior of the PbRuO3 perovskite under high pressure by first principles calculations. The calculated critical pressure for the phase transition and evolution of lattice parameters under pressure match the experimental results quantitatively. Our calculations also reveal that the hybridization between a Ru:t2g orbital and an sp hybrid on Pb increases dramatically in the Pbnm phase under pressure. This pressure-induced change destabilizes the Pbnm phase to give a phase transition to the Pbn21 phase where electrons in the overlapping orbitals form bonding and antibonding states along the shortest Ru—Pb direction at P > Pc. PMID:24277807

  1. Shape-Controlled Synthesis of All-Inorganic CsPbBr3 Perovskite Nanocrystals with Bright Blue Emission.

    Science.gov (United States)

    Liang, Zhiqin; Zhao, Suling; Xu, Zheng; Qiao, Bo; Song, Pengjie; Gao, Di; Xu, Xurong

    2016-10-26

    We developed a colloidal synthesis of CsPbBr 3 perovskite nanocrystals (NCs) at a relative low temperature (90 °C) for the bright blue emission which differs from the original green emission (∼510 nm) of CsPbBr 3 nanocubes as reported previously. Shapes of the obtained CsPbBr 3 NCs can be systematically engineered into single and lamellar-structured 0D quantum dots, as well as face-to-face stacking 2D nanoplatelets and flat-lying 2D nanosheets via tuning the amounts of oleic acid (OA) and oleylamine (OM). They exhibit sharp excitonic PL emissions at 453, 472, 449, and 452 nm, respectively. The large blue shift relative to the emission of CsPbBr 3 bulk crystal can be ascribed to the strong quantum confinement effects of these various nanoshapes. PL decay lifetimes are measured, ranging from several to tens of nanoseconds, which infers the higher ratio of exciton radiative recombination to the nonradiative trappers in the obtained CsPbBr 3 NCs. These shape-controlled CsPbBr 3 perovskite NCs with the bright blue emission will be widely used in optoelectronic applications, especially in blue LEDs which still lag behind compared to the better developed red and green LEDs.

  2. Dental caries and vitamin D3 in children with growth hormone deficiency: A STROBE compliant study.

    Science.gov (United States)

    Wójcik, Dorota; Krzewska, Aleksandra; Szalewski, Leszek; Pietryka-Michałowska, Elżbieta; Szalewska, Magdalena; Krzewski, Szymon; Pels, Elżbieta; Beń-Skowronek, Iwona

    2018-02-01

    Vitamin D may prevent dental caries. To date, no attempts have been made to examine the correlation between the incidence of caries and the concentrations of vitamin D in children with pituitary growth hormone deficiency.The study observed patients of the Department of Endocrinology and Diabetology of the University Paediatric Hospital of the Medical University of Lublin treated with human recombinant growth hormone for pituitary growth hormone deficiency (GHD). The study was conducted between October 2014 and June 2015. The study group consisted of 121 children and adolescents (6-17 years old), including 56 children from rural areas and 65 children from urban areas. The study group was stratified by area of residence.In our study, the increase in vitamin D3 [25(OH)D] levels reduced the D component by 0.66 per each 10 ng/mL of vitamin D3 concentration. The percentage of children with active caries in rural areas is 91.07% (n = 51), which is significantly higher than the percentage of children with active caries in urban areas (81.54%, n = 53).To date, information regarding the potential possibility of reducing the incidence of dental caries by means of increasing the levels of vitamin D was sidelined by paediatricians and dentists alike. Therefore, this aspect of caries prevention should be highlighted.

  3. Severe Vitamin D Deficiency in HIV-infected Pregnant Women is Associated with Preterm Birth

    Science.gov (United States)

    Jao, Jennifer; Freimanis, Laura; Mussi-Pinhata, Marisa M.; Cohen, Rachel A.; Monteiro, Jacqueline Pontes; Cruz, Maria Leticia; Branch, Andrea; Sperling, Rhoda S.; Siberry, George K.

    2017-01-01

    Background Low maternal vitamin D has been associated with preterm birth (PTB). HIV-infected pregnant women are at risk for PTB, but data on maternal vitamin D and PTB in this population is scarce. Methods In a cohort of Latin American HIV-infected pregnant women from the NICHD International Site Development Initiative (NISDI) protocol, we examined the association between maternal vitamin D status and PTB. Vitamin D status was defined as the following 25-hydroxyvitamin D levels: severe deficiency (PTBs =36 wks (interquartile range: 34-36)]. In multivariate analysis, severe vitamin D deficiency was associated with PTB [Odds Ratio=4.7, 95% Confidence Interval: 1.3-16.8)]. Conclusion Severe maternal vitamin D deficiency is associated with PTB in HIV-infected Latin American pregnant women. Further studies are warranted to determine if vitamin D supplementation in HIV-infected women may impact PTB. PMID:27716863

  4. Room-Temperature Atomic Layer Deposition of Al2 O3 : Impact on Efficiency, Stability and Surface Properties in Perovskite Solar Cells.

    Science.gov (United States)

    Kot, Malgorzata; Das, Chittaranjan; Wang, Zhiping; Henkel, Karsten; Rouissi, Zied; Wojciechowski, Konrad; Snaith, Henry J; Schmeisser, Dieter

    2016-12-20

    In this work, solar cells with a freshly made CH 3 NH 3 PbI 3 perovskite film showed a power conversion efficiency (PCE) of 15.4 % whereas the one with 50 days aged perovskite film only 6.1 %. However, when the aged perovskite was covered with a layer of Al 2 O 3 deposited by atomic layer deposition (ALD) at room temperature (RT), the PCE value was clearly enhanced. X-ray photoelectron spectroscopy study showed that the ALD precursors are chemically active only at the perovskite surface and passivate it. Moreover, the RT-ALD-Al 2 O 3 -covered perovskite films showed enhanced ambient air stability. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Decreased heterotopic osteogenesis in vitamin-D-deficient, but normocalcemic guinea pigs

    Science.gov (United States)

    Dziedzic-Goclawska, A.; Toverud, S. U.; Kaminski, A.; Boass, A.; Yamauchi, M.

    1992-01-01

    The effect of vitamin D deficiency unhampered by hypocalcemia on de novo bone formation was studied in guinea pigs. Heterotopic induction of osteogenesis was evaluated 4 weeks after intramuscular transplantation of allogenic urinary bladder transitional epithelium from vitamin-D-repleted (+D) donors into +D and -D recipients. In -D recipients the frequency of osteogenesis and the amount of induced bone were significantly diminished; induced bone was less mature, scantly cellular woven bone poorly repopulated with bone marrow. No effect of vitamin D deficiency on orthotopic bone growth and on mineralization of orthotopic and heterotopically induced bone was observed. It is proposed that in addition to inducing factors (BMPs, growth factors) which may be responsible for transformation of mesenchymal cells to osteoprogenitor cells, normal concentrations of 1,25-(OH)2D3 may be required for proliferation and further differentiation of these cells into osteoblasts and for expression of genes engaged in extracellular matrix formation and maturation.

  6. [Vitamin D deficiency and morbimortality in critically ill paediatric patients].

    Science.gov (United States)

    García-Soler, Patricia; Morales-Martínez, Antonio; Rosa-Camacho, Vanessa; Lillo-Muñoz, Juan Antonio; Milano-Manso, Guillermo

    2017-08-01

    To determine the prevalence and risks factors of vitamin D deficiency, as well as its relationship with morbidity and mortality in a PICU. An observational prospective study in a tertiary children's University Hospital PICU conducted in two phases: i: cohorts study, and ii: prevalence study. The study included 340 critically ill children with ages comprising 6 months to 16 years old. Chronic kidney disease, known parathyroid disorders, and vitamin D supplementation. Total 25-hydroxyvitamin D [25(OH)D] was measured in the first 48hours of admission to a PICU. Parathormone, calcium, phosphate, blood gases, blood count, C-reactive protein, and procalcitonin were also analysed. A record was also made of demographic features, characteristics of the episode, and complications during the PICU stay. The overall prevalence rate of vitamin D deficiency was 43.8%, with a mean of 22.28 (95% CI 21.15-23.41) ng/ml. Patients with vitamin D deficiency were older (61 vs 47 months, P=.039), had parents with a higher level of academic studies (36.5% vs 20%, P=.016), were admitted more often in winter and spring, had a higher PRISM-III (6.8 vs 5.1, P=.037), a longer PICU stay (3 vs 2 days, P=.001), and higher morbidity (61.1% vs 30.4%, P<001) than the patients with sufficient levels of 25(OH)D. Patients who died had lower levels of 25(OH)D (14±8.81ng/ml versus 22.53±10.53ng/ml, P=.012). Adjusted OR for morbidity was 5.44 (95%CI; 2.5-11.6). Vitamin D deficiency is frequent in critically ill children, and it is related to both morbidity and mortality, although it remains unclear whether it is a causal relationship or it is simply a marker of severity in different clinical situations. Copyright © 2016 Asociación Española de Pediatría. Publicado por Elsevier España, S.L.U. All rights reserved.

  7. Stable, easily sintered BaCe0.5Zr0.3Y0.16Zn0.04O3-δ electrolyte-based proton-conducting solid oxide fuel cells by gel-casting and suspension spray

    International Nuclear Information System (INIS)

    Lin Bin; Dong Yingchao; Wang Songlin; Fang Daru; Ding Hanping; Zhang Xiaozhen; Liu Xingqin; Meng Guangyao

    2009-01-01

    Protonic ceramic membrane fuel cells (PCMFCs) based on oxide proton conductors exhibit more advantages than traditional solid oxide fuel cells (SOFCs) based on oxygen-ion conducting electrolytes, such as low activation energy and high energy efficiency. In order to develop a simple and cost-effective route to fabricate PCMFCs with SrCo 0.9 Sb 0.1 O 3-δ (SCS) cubic perovskite cathode, a dense BaCe 0.5 Zr 0.3 Y 0.16 Zn 0.04 O 3-δ (BCZYZn) electrolyte was fabricated in situ metal oxide on a porous anode support by gel-casting and suspension spray, which is cost-effective, easy to realize, and suitable for mass-production. The key part of this process is to directly spray well-mixed suspension of BaCO 3 , CeO 2 , ZrO 2 , Y 2 O 3 and ZnO instead of pre-synthesized BCZYZn ceramic powder on the anode substrate. With SCS cubic perovskite cathode synthesized by gel-casting on the bi-layer, single cells were assembled and tested with H 2 as fuel and the static air as oxidant. An open-circuit potential of 0.987 V, a maximum power density of 364 mW cm -2 , and a low polarization resistance of the electrodes of 0.07 Ω cm 2 was achieved at 700 deg. C.

  8. Higher visceral fat area increases the risk of vitamin D insufficiency and deficiency in Chinese adults.

    Science.gov (United States)

    Zhang, Meilin; Li, Ping; Zhu, Yufeng; Chang, Hong; Wang, Xuan; Liu, Weiqiao; Zhang, Yuwen; Huang, Guowei

    2015-01-01

    Visceral fat area (VFA), a novel sex-specific index for visceral fat obesity (VFO) might play a major role in the development of vitamin D deficiency. However, the association between VFA and vitamin D insufficiency and deficiency in Chinese population is less clear. The aim of this study was to explore the population-level association between VFA and vitamin D insufficiency and deficiency among Chinese men and women. This cross-sectional study involved 1105 adults aged 20-70 years living in Tianjin who were randomly selected and medically examined. All subjects underwent the bioelectrical impedance analysis (BIA) method to estimate the VFA. Serum 25-hydroxyvitamin D3 (25(OH) D3) level was assayed by the high-performance liquid chromatography (HPLC) method and defined insufficiency and deficiency following recommended cutoffs. The association between VFA and vitamin D insufficiency and deficiency was estimated using binary regression analysis. The total prevalence of vitamin D insufficiency (25(OH) D3: 20-29 μg/L) and deficiency (25(OH) D3  0.05). Moreover, increased VFA was observed to be associated with higher vitamin D insufficiency or deficiency risk with a positive dose-response trend (P for trend convenience surrogate marker for visceral adipose measurement and could be used in identifying the risk of vitamin D insufficiency and deficiency in routine health examination.

  9. New vanadium oxides with perovskite type structure: AThV/sub 2/O/sub 6/ (A=Ca,Sr)

    Energy Technology Data Exchange (ETDEWEB)

    Vidyasagar, K; Gopalakrishnan, J

    1982-07-01

    New perovskite oxides of the formula AThV/sub 2/O/sub 6/ (A=Ca,Sr) have been prepared by reduction of the corresponding AThV/sub 2/O/sub 8/ under hydrogen atmosphere. CaThV/sub 2/O/sub 6/ crystallizes in an orthorhombic LaVO/sub 3/ type structure, while the strontium compound exhibiting cation-deficient nonstoichiometry. SrThsub(1-x)V/sub 2/O/sub 6/ (x approx. 0.4), is cubic. The magnetic susceptibility behaviour of the calcium compound is similar to that of V/sup 3 +/ perovskites, while the strontium compound exhibits a large increase in susceptibility below 130K, the behaviour being likely to be associated with the mixed-valence character of vanadium.

  10. Photovoltaic performance of textured silicon solar cells with MAPbBr3 perovskite nanophosphors to induce luminescent down-shifting

    Science.gov (United States)

    Ho, Wen-Jeng; Li, Guan-Yi; Liu, Jheng-Jie; Lin, Zong-Xian; You, Bang-Jin; Ho, Chun-Hung

    2018-04-01

    This study employed a two-step multi-cycle spin-coating method for the application of MAPbBr3 perovskite nanophosphors on textured silicon solar cells with the aim of enhancing photovoltaic performance through luminescent down-shifting (LDS). The surface morphology and dimensions of the MAPbBr3 perovskite nanophosphors were examined using scanning electron microscopy in conjunction with ImageJ software. The LDS effects of the nanophosphors were revealed by measuring photo-luminance, optical reflectance, and external quantum efficiency. The photovoltaic performance of cells with and without MAPbBr3 perovskite nanophosphors was evaluated according to photovoltaic current density-voltage (J-V) under AM 1.5 G solar illumination. Compared to uncoated cells, two-layer and one-layer coatings of MAPbBr3 perovskite nanophosphors were shown to enhance conversion efficiency by 4.56% and 3.38%, respectively.

  11. Evolution of Photoluminescence, Raman, and Structure of CH3NH3PbI3 Perovskite Microwires Under Humidity Exposure

    Science.gov (United States)

    Segovia, Rubén; Qu, Geyang; Peng, Miao; Sun, Xiudong; Shi, Hongyan; Gao, Bo

    2018-03-01

    Self-assembled organic-inorganic CH3NH3PbI3 perovskite microwires (MWs) upon humidity exposure along several weeks were investigated by photoluminescence (PL) spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD). We show that, in addition to the common perovskite decomposition into PbI2 and the formation of a hydrated phase, humidity induced a gradual PL redshift at the initial weeks that is stabilized for longer exposure ( 21 nm over the degradation process) and an intensity enhancement. Original perovskite Raman band and XRD reflections slightly shifted upon humidity, indicating defects formation and structure distortion of the MWs crystal lattice. By correlating the PL, Raman, and XRD results, it is believed that the redshift of the MWs PL emission was originated from the structural disorder caused by the incorporation of H2O molecules in the crystal lattice and radiative recombination through moisture-induced subgap trap states. Our study provides insights into the optical and structural response of organic-inorganic perovskite materials upon humidity exposure.

  12. Highly Efficient Spectrally Stable Red Perovskite Light-Emitting Diodes.

    Science.gov (United States)

    Tian, Yu; Zhou, Chenkun; Worku, Michael; Wang, Xi; Ling, Yichuan; Gao, Hanwei; Zhou, Yan; Miao, Yu; Guan, Jingjiao; Ma, Biwu

    2018-05-01

    Perovskite light-emitting diodes (LEDs) have recently attracted great research interest for their narrow emissions and solution processability. Remarkable progress has been achieved in green perovskite LEDs in recent years, but not blue or red ones. Here, highly efficient and spectrally stable red perovskite LEDs with quasi-2D perovskite/poly(ethylene oxide) (PEO) composite thin films as the light-emitting layer are reported. By controlling the molar ratios of organic salt (benzylammonium iodide) to inorganic salts (cesium iodide and lead iodide), luminescent quasi-2D perovskite thin films are obtained with tunable emission colors from red to deep red. The perovskite/polymer composite approach enables quasi-2D perovskite/PEO composite thin films to possess much higher photoluminescence quantum efficiencies and smoothness than their neat quasi-2D perovskite counterparts. Electrically driven LEDs with emissions peaked at 638, 664, 680, and 690 nm have been fabricated to exhibit high brightness and external quantum efficiencies (EQEs). For instance, the perovskite LED with an emission peaked at 680 nm exhibits a brightness of 1392 cd m -2 and an EQE of 6.23%. Moreover, exceptional electroluminescence spectral stability under continuous device operation has been achieved for these red perovskite LEDs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Composition-dependent emission linewidth broadening in lead bromide perovskite (APbBr3, A = Cs and CH3NH3) nanoparticles.

    Science.gov (United States)

    Ham, Sujin; Chung, Heejae; Kim, Tae-Woo; Kim, Jiwon; Kim, Dongho

    2018-02-01

    Lead halide perovskite nanoparticles (NPs) are attractive as they exhibit excellent color purity and have a tunable band gap, and can thus be applied in highly efficient photovoltaic and light-emitting diodes. Fundamental studies of emission linewidth broadening due to spectral shifts in perovskite NPs may suggest a way to improve their color purity. However, the carrier-induced Stark shift that causes spectral diffusion still requires investigation. In this study, we explore composition-related emission linewidth broadening by comparing CsPbBr3 and CH 3 NH 3 PbBr 3 (MAPbBr3) perovskite NPs. We find that the MAPbBr3 NPs are more sensitive to fluctuations in the local electric fields than the CsPbBr3 NPs due to an intrinsic difference in the dipole moment between the two A cations (Cs and MA), which shows a carrier-induced Stark shift. The results indicate that the compositions of perovskite NPs are closely associated with emission linewidth broadening and they also provide insights into the development of NP-based devices with high color purity.

  14. Perovskite structures in the formation of nano-rods in REBa2Cu3O7-δ films self-organization to perovskite structures

    International Nuclear Information System (INIS)

    Mukaida, Masashi; Kai, Hideki; Shingai, Yuki

    2009-01-01

    Cubic perovskite structure has been found to play an important role for the nano-rod formation in REBa 2 Cu 3 O 7-δ films. BaWO 4 , with a sheelite structure, and BaNb 2 O 6 , with a tungsten bronze structure, were doped into REBa 2 Cu 3 O 7-δ targets. Laser-deposited, these materials form nano-rods in REBa 2 Cu 3 O 7-δ films accompanied by Ln elements, resulting in the composition of a pseudo-cubic perovskite structure. This was confirmed by selected area electron diffraction patterns (SADP) and composition mapping using energy-dispersive X-ray spectroscopy scanning transmission electron microscope (EDS-STEM) analysis. BaWO 4 with a sheelite structure, and BaNb 2 O 6 with a tungsten bronze structure, doped into targets no longer retain their structures, but can form pseudo-cubic perovskite structures in laser-deposited REBa 2 Cu 3 O 7-δ films. The perovskite crystal structure is thought to be important for nano-rod formation in the laser deposited REBa 2 Cu 3 O 7-δ film. (author)

  15. The synthesis of 1,2,7,11b-Tetrahydroisoxazolo[2,3-d][1,4]benzodiazepin-6(5H)-ones and 1,3,3a,9b-tetrahydroisoxazolo[4,3-c]quinolin-4(5H)-ones

    OpenAIRE

    Heaney, Frances; Bourke, Sharon

    1995-01-01

    The reaction of various ethyl 3-[[2-(1-hydroxyiminoalkyl)phenyl]carbamoyl]acrylates (2) with electron deficient olefins proceeds via a sequential dipole formation, dipolar cycloaddition sequence to furnish the tetrahydroisoxazolo[2,3-d][1,4]benzodiazepin-6(5H)-ones and tetrahydroisoxazolo[4,3-c]quinolin-4(5H)-ones (4) and (6). The product distribution reflects the nature of the reacting olefin and the position and extent of substitution on the acrylate moiety.

  16. Protean manifestations of vitamin D deficiency, part 3: association with cardiovascular disease and disorders of the central and peripheral nervous systems.

    Science.gov (United States)

    Bell, David S H

    2011-05-01

    Vitamin D deficiency is associated with the risk factors of inflammation, insulin resistance and endothelial dysfunction, and left ventricular hypertrophy. As a result there is an increase in cardiovascular events (CVEs) associated with vitamin D deficiency. Vitamin D deficiency itself or secondary hyperparathyroidism or both may be responsible for the increase in CVEs. Correction of vitamin D deficiency may decrease the incidence of CVEs. Vitamin D deficiency is also associated with Alzheimer disease, schizophrenia, depression, and chronic pain and muscle weakness. Vitamin D deficiency is early treated with oral vitamin D supplements which may improve the manifestations of the diseases associated with vitamin D deficiency.

  17. Metabolic Effects of CX3CR1 Deficiency in Diet-Induced Obese Mice.

    Directory of Open Access Journals (Sweden)

    Rachana Shah

    Full Text Available The fractalkine (CX3CL1-CX3CR1 chemokine system is associated with obesity-related inflammation and type 2 diabetes, but data on effects of Cx3cr1 deficiency on metabolic pathways is contradictory. We examined male C57BL/6 Cx3cr1-/- mice on chow and high-fat diet to determine the metabolic effects of Cx3cr1 deficiency. We found no difference in body weight and fat content or feeding and energy expenditure between Cx3cr1-/- and WT mice. Cx3cr1-/- mice had reduced glucose intolerance assessed by intraperitoneal glucose tolerance tests at chow and high-fat fed states, though there was no difference in glucose-stimulated insulin values. Cx3cr1-/- mice also had improved insulin sensitivity at hyperinsulinemic-euglycemic clamp, with higher glucose infusion rate, rate of disposal, and hepatic glucose production suppression compared to WT mice. Enhanced insulin signaling in response to acute intravenous insulin injection was demonstrated in Cx3cr1-/- by increased liver protein levels of phosphorylated AKT and GSK3β proteins. There were no differences in adipose tissue macrophage populations, circulating inflammatory monocytes, adipokines, lipids, or inflammatory markers. In conclusion, we demonstrate a moderate and reproducible protective effect of Cx3cr1 deficiency on glucose intolerance and insulin resistance.

  18. Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

    Directory of Open Access Journals (Sweden)

    Ryo eWatanabe

    2013-10-01

    Full Text Available For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1–xSrxFeyMn1–yO3d(0 ≤ x≤ 1, 0.2 ≤ y≤ 0.8, perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3d catalyst with that of an industrial potassium promoted iron (Fe–K catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3d catalyst showed higher initial activity than the industrial Fe–K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3d catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe–K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3d and the Fe–K catalysts in aH2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3d catalyst while the Fe–K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3d catalyst had higher potential for activating the steam than the Fe–K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3d was superior to that of Fe–K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3d perovskite oxide.

  19. Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

    Science.gov (United States)

    Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

    2013-10-01

    For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1-xSrxFeyMn1-yO3-d(0 ≤ x≤ 1, 0.2 ≤ y≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst with that of an industrial potassium promoted iron (Fe-K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed higher initial activity than the industrial Fe-K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe-K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d and the Fe-K catalysts in aH2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst while the Fe-K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst had higher potential for activating the steam than the Fe-K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3-d was superior to that of Fe-K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d perovskite oxide.

  20. 25-hydroxy vitamin D levels, vitamin D deficiency and insufficiency in patients with bone and musculoskeletal disorders

    Directory of Open Access Journals (Sweden)

    V.V. Povoroznyuk

    2017-08-01

    Full Text Available Background. Vitamin D deficiency is prevalent in all the world countries. Recent studies show the correlation between vitamin D deficiency and musculoskeletal disorders. The purpose of this study is to examine vitamin D deficiency and insufficiency prevalence in patients of various ages, who have musculoskeletal disorders, and to reveal the influence of seasonal factors on these conditions. Materials and methods. 3460 patients of the Ukrainian Scientific Medical Center of Osteoporosis Problems, aged 1 to 92 years, who were referred by other specialists to the center for bone state evaluation, were examined. A majority of the patients presented with osteoporosis and its complications, spinal osteochondrosis, knee and hip osteoarthritis (mean age — 52.90 ± 21.10 years. Most of the patients were women (83.5 %. 25(ОНD and parathyroid hormone analyses were performed by means of electrochemiluminescent method (Elecsys 2010 analyzer, Roche Diagnostics, Germany and cobas test-systems. Statistica 6.0 software package (Copyright StatSoft, Inc., 1984–2001 was also used. Results. Among the patients with musculoskeletal pathology, the highest 25(ОНD level was noted in the age group of 1–9 years and the lowest — in the age group of 80 and over. Age negatively influenced 25(ОНD values. Prevalence of vitamin D deficiency among the patients with musculoskeletal pathology was 37.3 %, vitamin D insufficiency — 30.6 %; 32.1 % of patients had normal vitamin D status. Normal 25(OHD level was found in 38.0 % of children, 33.2 % of adults and in 29.6 % of elderly patients. Month of blood sampling had a significant influence on 25(ОНD content (F = 7.49; p < 0.001. The highest significant differences in 25(ОНD levels during the summer vs. winter months were observed in the age groups of 10–19 (18.2 %, 40–49 (17.3 %, 30–39 (16.2 % и 1–9 years (16.1 %. There were no significant seasonal differences observed in the elderly patients (60

  1. Crystal structures of the double perovskites Ba2Sr1-x Ca x WO6

    International Nuclear Information System (INIS)

    Fu, W.T.; Akerboom, S.; IJdo, D.J.W.

    2007-01-01

    Structures of the double perovskites Ba 2 Sr 1- x Ca x WO 6 have been studied by the profile analysis of X-ray diffraction data. The end members, Ba 2 SrWO 6 and Ba 2 CaWO 6 , have the space group I2/m (tilt system a 0 b - b - ) and Fm3-barm (tilt system a 0 a 0 a 0 ), respectively. By increasing the Ca concentration, the monoclinic structure transforms to the cubic one via the rhombohedral R3-bar phase (tilt system a - a - a - ) instead of the tetragonal I4/m phase (tilt system a 0 a 0 c - ). This observation supports the idea that the rhombohedral structure is favoured by increasing the covalency of the octahedral cations in Ba 2 MM'O 6 -type double perovskites, and disagrees with a recent proposal that the formation of the π-bonding, e.g., d 0 -ion, determines the tetragonal symmetry in preference to the rhombohedral one. - Graphical abstract: Enlarged sections showing the evolution of the basic (222) and (400) reflections in Ba 2 Sr 1- x Ca x WO 6 . Tick marks below are the positions of Bragg's reflections calculated using the space groups I2/m (x=0), R3-bar (x=0.25, 0.5 and 0.75) and Fm3-barm (x=1), respectively

  2. Fabrication and characterization of perovskite-based CH{sub 3}NH{sub 3}Pb{sub 1-x}Ge{sub x}I{sub 3}, CH{sub 3}NH{sub 3}Pb{sub 1-x}Tl{sub x}I{sub 3} and CH{sub 3}NH{sub 3}Pb{sub 1-x}In{sub x}I{sub 3} photovoltaic devices

    Energy Technology Data Exchange (ETDEWEB)

    Ohishi, Yuya; Oku, Takeo, E-mail: oku@mat.usp.ac.jp; Suzuki, Atsushi [Department of Materials Science, The University of Shiga Prefecture 2500 Hassaka, Hikone, Shiga 522-8533 (Japan)

    2016-02-01

    Perovskite-type CH{sub 3}NH{sub 3}PbI{sub 3}-based photovoltaic devices were fabricated and characterized. Doping effects of thallium (Tl), indium (In), or germanium (Ge) element on the photovoltaic properties and surface structures of the perovskite phase were investigated. The open circuit voltage increased by Ge addition, and fill factors were improved by adding a small amount of Ge, Tl or In. In addition, the wavelength range of incident photon conversion efficiencies was expanded by the Tl addition.

  3. Reversible modulation of CsPbBr3 perovskite nanocrystal/gold nanoparticle heterostructures.

    Science.gov (United States)

    Chen, Shanshan; Lyu, Danya; Ling, Tao; Guo, Weiwei

    2018-04-19

    A facile strategy is illustrated to reversibly modulate CsPbBr3 perovskite nanocrystal/Au nanoparticle heterostructures with the reversible formation and fragmentation of gold nanoparticles anchored to the corners and surface of CsPbBr3 perovskite nanocrystals. The modulation process was performed under ambient conditions and could be conducted for cycles.

  4. 3'-Azido-2',3'-dideoxythymidine induced deficiency of thymidine kinases 1, 2 and deoxycytidine kinase in H9 T-lymphoid cells.

    Science.gov (United States)

    Gröschel, Bettina; Kaufmann, Andreas; Höver, Gerold; Cinatl, Jaroslav; Doerr, Hans Wilhelm; Noordhuis, Paul; Loves, Willem J P; Peters, Godefridus J; Cinatl, Jindrich

    2002-07-15

    Continuous cultivation of T-lymphoid H9 cells in the presence of 3'-azido-2',3'-dideoxythymidine (AZT) resulted in a cell variant cross-resistant to both thymidine and deoxycytidine analogs. Cytotoxic effects of AZT, 2',3'-didehydro-3'-deoxythymidine as well as different deoxycytidine analogs such as 2',3'-dideoxycytidine, 2',2'-difluoro-2'-deoxycytidine (dFdC) and 1-ss-D-arabinofuranosylcytosine (Ara-C) were strongly reduced in H9 cells continuously exposed to AZT when compared to parental cells (>8.3-, >6.6-, >9.1-, 5 x 10(4)-, 5 x 10(3)-fold, respectively). Moreover, anti-HIV-1 effects of AZT, d4T, ddC and 2',3'-dideoxy-3'-thiacytidine (3TC) were significantly diminished (>222-, >25-, >400-, >200-fold, respectively) in AZT-resistant H9 cells. Study of cellular mechanisms responsible for cross-resistance to pyrimidine analogs in AZT-resistant H9 cells revealed decreased mRNA levels of thymidine kinase 1 (TK1) and lack of deoxycytidine kinase (dCK) mRNA expression. The loss of dCK gene expression was confirmed by western blot analysis of dCK protein as well as dCK enzyme activity assay. Moreover, enzyme activity of TK1 and TK2 was reduced in AZT-resistant cells. In order to determine whether lack of dCK affected the formation of the active triphosphate of the deoxycytidine analog dFdC, dFdCTP accumulation and retention was measured in H9 parental and AZT-resistant cells after exposure to 1 and 10 microM dFdC. Parental H9 cells accumulated about 30 and 100 pmol dFdCTP/10(6) cells after 4hr, whereas in AZT-resistant cells no dFdCTP accumulation was detected. These results demonstrate that continuous treatment of H9 cells in the presence of AZT selected for a thymidine analog resistant cell variant with cross-resistance to deoxycytidine analogs, due to deficiency in TK1, TK2, and dCK.

  5. VITAMIN D DEFICIENCY IN JAMMU IN SUBJECTS WITH NO COMORBIDITY- A PRELIMINARY STUDY

    Directory of Open Access Journals (Sweden)

    Sidharth Kapoor

    2017-11-01

    Full Text Available BACKGROUND Deficiency of the vitamin D may result in metabolic bone diseases leading to rickets in children or osteomalacia in adults.1,2 The vitamin D may provide protection against hypertension, cancer and multiple sclerosis.3 The vitamin D level is regulated through the interaction of various factors including intestinal absorption, renal function, serum calcium level and Parathyroid Hormone (PTH.3 The 2 main sources for vitamin D are synthesis in the skin on exposure to Ultraviolet-B (UVB light from sunlight and dietary intake. The aim of the study is to evaluate status of the vitamin D of a cohort of Jammu population with no comorbidity. A questionnaire was given to 119 patients (77 males and 42 females where information regarding intake of calcium and vitamin D supplementation, intake of calcium rich food and exposure to vitamin D was sought. MATERIALS AND METHODS Estimation of serum 25-hydroxyvitamin D (25(OH3 and plasma Parathyroid Hormone (PTH intact levels was done the subjects. Serum 25 (OH 2D3 levels did not differ significantly between males and females, although the levels were low (males 9.72 ng/mL ± 4.2 and females 8.5 ng/mL ± 4.7. RESULTS The vitamin D was still in the deficiency range even after excluding the subjects with very high PTH levels. CONCLUSION There was a high prevalence of a vitamin D deficiency in this sample of Jammu despite >70% of participants having adequate exposure to sunlight and >80% reporting adequate intake of dairy products.

  6. Overcoming Short-Circuit in Lead-Free CH3NH3SnI3 Perovskite Solar Cells via Kinetically Controlled Gas-Solid Reaction Film Fabrication Process.

    Science.gov (United States)

    Yokoyama, Takamichi; Cao, Duyen H; Stoumpos, Constantinos C; Song, Tze-Bin; Sato, Yoshiharu; Aramaki, Shinji; Kanatzidis, Mercouri G

    2016-03-03

    The development of Sn-based perovskite solar cells has been challenging because devices often show short-circuit behavior due to poor morphologies and undesired electrical properties of the thin films. A low-temperature vapor-assisted solution process (LT-VASP) has been employed as a novel kinetically controlled gas-solid reaction film fabrication method to prepare lead-free CH3NH3SnI3 thin films. We show that the solid SnI2 substrate temperature is the key parameter in achieving perovskite films with high surface coverage and excellent uniformity. The resulting high-quality CH3NH3SnI3 films allow the successful fabrication of solar cells with drastically improved reproducibility, reaching an efficiency of 1.86%. Furthermore, our Kelvin probe studies show the VASP films have a doping level lower than that of films prepared from the conventional one-step method, effectively lowering the film conductivity. Above all, with (LT)-VASP, the short-circuit behavior often obtained from the conventional one-step-fabricated Sn-based perovskite devices has been overcome. This study facilitates the path to more successful Sn-perovskite photovoltaic research.

  7. Prevalence and risk factors of vitamin D deficiency in patients with widespread musculoskeletal pain

    Directory of Open Access Journals (Sweden)

    Muharrem Çidem

    2013-12-01

    Full Text Available Objective: Vitamin D deficiency is a worldwide common health problems. Vitamin D deficiency in adults has been associated with proximal muscle weakness, skeletal mineralization defect, and an increased risk of falling. Patients with vitamin D deficiency commonly complain of widespread pain in the body. The aim of this study was to examine the prevalence and risk factors of 25-hydroxyvitamin D deficiency in patients complaining of widespread musculoskeletal pain. Methods: In this cross-sectional study, 8457 patients with widespread musculoskeletal pain (7772 females, 685 males, aged 46.7 (range 20-100 years were included. Serum 25-hydroxyvitamin D was measured with ELISA method. Patients were classified into two groups: 1 Patients with vitamin D deficiency (20 ng/ml. Results: Prevalence of vitamin D deficiency was found to be 71.7%. A binary logistic regression model showed that low 25(OHVit D level was associated with gender, age and month in which 25(OH hypovitaminosis was determined. The risk of low 25(OH Vit D was found to be 2.15 times higher in female patients and 1.52 times higher on March and 1.55 times higher on April. Conclusion: This study indicates that Vitamin D deficiency should be taken into consideration in patients with widespread musculoskeletal pain, and some precautions such as sunbathe during summer should be recommended patients having risk of vitamin D deficiency. J Clin Exp Invest 2013; 4 (4: 48-491

  8. Vitamin D deficiency in elderly people in Swedish nursing homes is associated with increased mortality.

    Science.gov (United States)

    Samefors, Maria; Östgren, Carl Johan; Mölstad, Sigvard; Lannering, Christina; Midlöv, Patrik; Tengblad, Anders

    2014-05-01

    Institutionalised elderly people at northern latitudes may be at elevated risk for vitamin D deficiency. In addition to osteoporosis-related disorders, vitamin D deficiency may influence several medical conditions conferring an increased mortality risk. The aim of this study was to explore the prevalence of vitamin D deficiency and its association with mortality. The Study of Health and Drugs in the Elderly (SHADES) is a prospective cohort study among elderly people (>65 years) in 11 nursing homes in Sweden. We analysed the levels of 25-hydroxyvitamin D₃ (25(OH)D₃) at baseline. Vital status of the subjects was ascertained and hazard ratios (HRs) for mortality according to 25(OH)D₃ quartiles were calculated. We examined 333 study participants with a mean follow-up of 3 years. A total of 147 (44%) patients died within this period. Compared with the subjects in Q4 (25(OH)D₃ >48  nmol/l), HR (with 95% CI) for mortality was 2.02 (1.31-3.12) in Q1 (25(OH)D₃ D₃ 30-37  nmol/l) (PD₃ 38-47  nmol/l) (PD₃ concentration was 40.2  nmol/l (S.D. 16.0) and 80% had 25(OH)D₃ below 50  nmol/l. The vitamin D levels decreased from baseline to the second and third measurements. Vitamin D deficiency was highly prevalent and associated with increased mortality among the elderly in Swedish nursing homes. Strategies are needed to prevent, and maybe treat, vitamin D deficiency in the elderly in nursing homes and the benefit of vitamin D supplementation should be evaluated in randomised clinical trials.

  9. Electrochemical hydrogen property improved in nano-structured perovskite oxide LaFeO3 for Ni/MH battery

    Science.gov (United States)

    Wang, Qiang; Deng, Gang; Chen, Zhiqian; Chen, Yungui; Cheng, Nanpu

    2013-02-01

    Perovskite oxide LaFeO3, as a novel candidate for the electrode of Ni/MH battery, holds high specific capacity and good cyclical durability at elevated temperatures. However, the poor electrochemical kinetics is a bottleneck for the application of this type of material. By use of nano-structured materials, there are greatly enhanced values of exchange current density I0 and hydrogen diffusion coefficient D, which resulted in an improvement of electrochemical kinetics, a much higher specific capacity and excellent stability during cycling for nano-structured LaFeO3. In theory, there is a significant possibility of further advancing the hydrogen reaction kinetics of perovskite type oxides for Ni/MH battery.

  10. Vitamin D deficiency is associated with functional decline and falls in frail elderly women despite supplementation.

    Science.gov (United States)

    Kotlarczyk, M P; Perera, S; Ferchak, M A; Nace, D A; Resnick, N M; Greenspan, S L

    2017-04-01

    We examined the impact of daily supplementation on vitamin D deficiency, function, and falls in female long-term care residents. Initial vitamin D deficiency was associated with greater functional decline and increased fall risk despite guideline-recommended supplementation, highlighting the importance of preventing vitamin D deficiency in frail elderly. Institute of Medicine (IOM) guidelines recommend 800 IU vitamin D daily for older adults and maintaining serum 25-hydroxyvitamin D [25(OH) D] above 20 ng/ml for optimal skeletal health. The adequacy of IOM guidelines for sustaining function and reducing falls in frail elderly is unknown. Female long-term care residents aged ≥65 enrolled in an osteoporosis clinical trial were included in this analysis (n = 137). Participants were classified based on baseline 25(OH) D levels as deficient (30 ng/ml, n = 71). Deficient women were provided initial vitamin D repletion (50,000 IU D 3 weekly for 8 weeks). All were supplemented with 800 IU vitamin D 3 daily for 24 months. Annual functional assessments included Activities of Daily Living (ADLs), Instrumental ADL (IADL), physical performance test (PPT), gait speed, cognition (SPMSQ), and mental health (PHQ-9). We used linear mixed models for analysis of functional measures and logistic regression for falls. Daily supplementation maintained 25(OH) D levels above 20 ng/ml in 95% of participants. All groups demonstrated functional decline. Women initially deficient had a greater decline in physical function at 12 (IADL -2.0 ± 0.4, PPT -3.1 ± 0.7, both p elderly. Further study of optimal 25(OH) D levels for maintaining function and preventing falls is needed.

  11. Vitamin D Deficiency in Community-Dwelling Elderly Is Not Associated with Age-Related Macular Degeneration.

    Science.gov (United States)

    Cougnard-Grégoire, Audrey; Merle, Bénédicte M J; Korobelnik, Jean-Francois; Rougier, Marie-Bénédicte; Delyfer, Marie-Noëlle; Féart, Catherine; Le Goff, Mélanie; Dartigues, Jean-François; Barberger-Gateau, Pascale; Delcourt, Cécile

    2015-08-01

    Elderly persons are at elevated risk of vitamin D deficiency, which is involved in various health problems. However, its relation with age-related macular degeneration (AMD) is debated. We investigated factors associated with plasma 25-hydroxyvitamin D [25(OH)D] deficiency and the associations between plasma 25(OH)D concentrations and AMD in elderly subjects. Antioxydants, Lipides Essentiels, Nutrition et maladies OculaiRes (ALIENOR) is a population-based study on eye diseases performed in elderly residents of Bordeaux, France. Plasma 25(OH)D concentrations were assessed from blood samples and categorized as D status were examined with multinomial logistic regression analysis. Associations between AMD and plasma 25(OH)D status were estimated using generalized estimating equation logistic regressions. Six hundred ninety-seven subjects with complete data were included. The prevalence of plasma 25(OH)D deficiency and insufficiency were 27.3% and 55.9%, respectively. In multivariate analysis, 25(OH)D deficiency was significantly associated with older age (P = 0.0007), females (P = 0.0007), absence of physical activity (P = 0.01), absence of vitamin D supplementation (P D insufficiency or deficiency (OR: 0.71, P = 0.12; OR: 0.73, P = 0.23, respectively) or with late AMD (OR: 1.04, P = 0.93; OR: 0.74, P = 0.59, respectively). These findings underline the very high prevalence of plasma 25(OH)D deficiency in this elderly population but do not support a specific role for vitamin D in AMD. © 2015 American Society for Nutrition.

  12. The structural, electronic, magnetic, and mechanical properties of perovskite oxides PbM1/2Nb1/2O3 (M = Fe, Co and Ni)

    Science.gov (United States)

    Erkisi, A.; Surucu, G.; Deligoz, E.

    2018-03-01

    In this study, the structural, electronic, magnetic, and mechanical properties of perovskite oxides PbM1/2Nb1/2O3 (M = Fe, Co and Ni) are investigated. The systems are treated in ferromagnetic order. The calculations are carried out in the framework of density functional theory (DFT) within the plane-wave pseudopotential method. The exchange-correlation potential is approximated by generalized-gradient spin approach (GGA). The intra-atomic Coulomb repulsion is also taken into account in calculations (GGA + U). We have considered two generalized-gradient spin approximation functionals, which are Perdew-Burke-Ernzerhof (PBE) and PBE for solids (PBEsol) for structural parameter calculations when it included Hubbard potential. Although the spin-polarized electronic band structures of PbCo1/2Nb1/2O3 and PbNi1/2Nb1/2O3 systems exhibit metallic property in ferromagnetic phase, a bandgap is observed in spin-down states of PbFe1/2Nb1/2O3 resulting in half-metallic behavior. The main reason for this behavior is attributed to the hybridization between d-states of transition metal atoms and p-states of oxygen atoms. The stability mechanically and the calculated mechanical properties by using elastic constants show that these compounds are mechanically stable in tetragonal phase and have anisotropic character mechanically.

  13. Interplay between organic cations and inorganic framework and incommensurability in hybrid lead-halide perovskite CH3NH3PbBr3

    Science.gov (United States)

    Guo, Yinsheng; Yaffe, Omer; Paley, Daniel W.; Beecher, Alexander N.; Hull, Trevor D.; Szpak, Guilherme; Owen, Jonathan S.; Brus, Louis E.; Pimenta, Marcos A.

    2017-09-01

    Organic-inorganic coupling in the hybrid lead-halide perovskite is a central issue in rationalizing the outstanding photovoltaic performance of these emerging materials. Here, we compare and contrast the evolution of the structure and dynamics of hybrid CH3NH3PbBr3 and inorganic CsPbBr3 lead-halide perovskites with temperature, using Raman spectroscopy and single-crystal x-ray diffraction. Results reveal a stark contrast between their order-disorder transitions, which are abrupt for the hybrid whereas smooth for the inorganic perovskite. X-ray diffraction observes an intermediate incommensurate phase between the ordered and the disordered phases in CH3NH3PbBr3 . Low-frequency Raman scattering captures the appearance of a sharp soft mode in the incommensurate phase, ascribed to the theoretically predicted amplitudon mode. Our work highlights the interaction between the structural dynamics of organic cation CH3NH3+ and the lead-halide framework, and unravels the competition between tendencies for the organic and inorganic moieties to minimize energy in the incommensurate phase of the hybrid perovskite structure.

  14. Conductivity of CH{sub 3}NH{sub 3}PbI{sub 3} thin film perovskite stored in ambient atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Gebremichael, Bizuneh, E-mail: bizunehme@gmail.com [Physics Department, Addis Ababa University, Addis Ababa, P.O. Box 1176 (Ethiopia); Alemu, Getachew [Physics Department, Addis Ababa University, Addis Ababa, P.O. Box 1176 (Ethiopia); Tessema Mola, Genene [School of Chemistry & Physics, University of KwaZulu-Nat al, Pietermaritzburg Campus, Private Bag X01, Scottsville 3209 (South Africa)

    2017-06-01

    Time dependent conductivity loss in CH{sub 3}NH{sub 3}PbI{sub 3} thin film perovskite stored in ambient atmosphere were studied based on electrical and optical measurements. Recent investigations on thin film perovskite solar cell suggest that in the steady state operation of the device, the V{sub oc} is unchanged by continuous illumination of light. Rather the reduction in the power conversion efficiency is caused by significant reduction of the short circuit current (J{sub sc}). In this paper, the effect of light on the optical absorption and electrical conductivity of the CH{sub 3}NH{sub 3}PbI{sub 3} thin film which is deposited on a glass substrate is investigated. The temperature dependent conductivity measurements indicated that the dominant conduction mechanism in the film perovskite is electronic rather than ionic.

  15. A Combined Variable-Temperature Neutron Diffraction and Thermogravimetric Analysis Study on a Promising Oxygen Electrode, SrCo0.9Nb0.1O3-δ, for Reversible Solid Oxide Fuel Cells.

    Science.gov (United States)

    Yang, Tianrang; Wang, Jie; Chen, Yan; An, Ke; Ma, Dong; Vogt, Thomas; Huang, Kevin

    2017-10-11

    The present study investigates the temperature-structure-stoichiometry relationship of a promising oxygen electrode SrCo 0.9 Nb 0.1 O 3-δ over a temperature (T) range from room temperature (RT) to 900 °C. The techniques employed are variable-temperature neutron diffraction (VTND) and thermogravimetric analysis (TGA). At T < 75 °C, VTND reveals a tetragonal (P4/mmm) structure with a G-type magnetic ordering. Above 75 °C, the nucleus structure remains the same, while the magnetic ordering disappears. A phase transition from tetragonal (P4/mmm) to cubic (Pm3̅m) is observed at 412 °C, where the two Co sites and three O sites in the P4/mmm phase converge to one equivalent site, respectively. The phase transition temperature coincides with the peak temperature of oxygen uptake obtained by TGA. It is also observed that the Nb dopant has no preferred Co site to occupy. The oxygen vacancies are mostly located at the O3 site surrounding the Co2 site in the P4/mmm structure. The intermediate-spin state of Co 3+ at the Co2 site is responsible for the observed distortions of CoO 6 octahedra, i.e., elongation of Co2O 6 octahedra and shortening of Co1O 6 octahedra along the c-axis, which is a phenomenon known as Jahn-Teller distortion. At high temperatures, large thermal displacement factor for O 2- is observed with high concentration of oxygen vacancies, providing a structural environment favorable to high O 2- conductivity in Nb-doped SrCoO 3 -based oxygen electrode materials.

  16. CH3 NH3 PbI3 and HC(NH2 )2 PbI3 Powders Synthesized from Low-Grade PbI2 : Single Precursor for High-Efficiency Perovskite Solar Cells.

    Science.gov (United States)

    Zhang, Yong; Kim, Seul-Gi; Lee, Do-Kyoung; Park, Nam-Gyu

    2018-05-09

    High-efficiency perovskite solar cells are generally fabricated by using highly pure (>99.99 %) PbI 2 mixed with an organic iodide in polar aprotic solvents. However, the use of such an expensive chemical may impede progress toward large-scale industrial applications. Here, we report on the synthesis of perovskite powders by using inexpensive low-grade (99 %) PbI 2 and on the photovoltaic performance of perovskite solar cells prepared from a powder-based single precursor. Pure APbI 3 [A=methylammonium (MA) or formamidinium (FA)] perovskite powders were synthesized by treating low-grade PbI 2 with MAI or FAI in acetonitrile at ambient temperature. The structural phase purity was confirmed by X-ray diffraction. The solar cell with a MAPbI 3 film prepared from the synthesized perovskite powder demonstrated a power conversion efficiency (PCE) of 17.14 %, which is higher than the PCE of MAPbI 3 films prepared by using both MAI and PbI 2 as precursors (PCE=13.09 % for 99 % pure PbI 2 and PCE=16.39 % for 99.9985 % pure PbI 2 ). The synthesized powder showed better absorption and photoluminescence, which were responsible for the better photovoltaic performance. For the FAPbI 3 powder, a solution with a yellow non-perovskite δ-FAPbI 3 powder synthesized at room temperature was found to lead to a black perovskite film, whereas a solution with the black perovskite α-FAPbI 3 powder synthesized at 150 °C was not transformed into a black perovskite film. The α↔δ transition between the powder and film was assumed to correlate with the difference in the iodoplumbates in the powder-dissolved solution. An average PCE of 17.21 % along with a smaller hysteresis [ΔPCE=PCE reverse -PCE forward )=1.53 %] was demonstrated from the perovskite solar cell prepared by using δ-FAPbI 3 powder; this PCE is higher than the average PCE of 17.05 % with a larger hysteresis (ΔPCE=2.71 %) for a device based on a conventional precursor solution dissolving MAI with high

  17. Molecular behavior of zero-dimensional perovskites

    KAUST Repository

    Yin, Jun

    2017-12-16

    Low-dimensional perovskites offer a rare opportunity to investigate lattice dynamics and charge carrier behavior in bulk quantum-confined solids, in addition to them being the leading materials in optoelectronic applications. In particular, zero-dimensional (0D) inorganic perovskites of the Cs4PbX6 (X = Cl, Br, or I) kind have crystal structures with isolated lead halide octahedra [PbX6]4− surrounded by Cs+ cations, allowing the 0D crystals to exhibit the intrinsic properties of an individual octahedron. Using both experimental and theoretical approaches, we studied the electronic and optical properties of the prototypical 0D perovskite Cs4PbBr6. Our results underline that this 0D perovskite behaves akin to a molecule, demonstrating low electrical conductivity and mobility as well as large polaron binding energy. Density functional theory calculations and transient absorption measurements of Cs4PbBr6 perovskite films reveal the polaron band absorption and strong polaron localization features of the material. A short polaron lifetime of ~2 ps is observed in femtosecond transient absorption experiments, which can be attributed to the fast lattice relaxation of the octahedra and the weak interactions among them.

  18. On the possibility of excitonic magnetism in Ir double perovskites

    Czech Academy of Sciences Publication Activity Database

    Pajskr, K.; Novák, Pavel; Pokorný, Vladislav; Kolorenč, Jindřich; Arita, R.; Kuneš, Jan

    2016-01-01

    Roč. 93, č. 3 (2016), 1-6, č. článku 035129. ISSN 1098-0121 R&D Projects: GA ČR GA13-25251S Institutional support: RVO:68378271 Keywords : spin-orbit coupling * double perovskite * excitonic magnetism Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  19. Thermal expansion behaviour in the oxygen deficient perovskites Sr2BSbO5.5 (B=Ca, Sr, Ba). Competing effects of water and oxygen ordering

    International Nuclear Information System (INIS)

    Zhou Qingdi; Kennedy, Brendan J.; Avdeev, Maxim

    2011-01-01

    Neutron diffractions studies reveal the presence of oxygen disorder in the oxygen deficient perovskites Sr 2 BSbO 5.5 (B=Ca, Sr, Ba). Synchrotron X-ray studies demonstrate that these oxides have a double perovskite-type structure with the cell size increasing as the size of the B cation increases from 8.2114(2) A for B=Ca to 8.4408(1) A for B=Ba. It is postulated that a combination of local clustering of the anions and vacancies together with water-water and water-host hydrogen bonds plays a role in defining the volume of the encapsulated water clusters and that changes in the local structure upon heating result in anomalous thermal expansion observed in variable temperature diffraction measurements. - Graphical abstract: The oxides Sr 2 BSbO 5.5 (B=Ca, Sr, Ba) have unusual anion disorder. There is a lag in the contraction in the cell size of Sr 2 CaSbO 5.5 nH 2 O established from X-ray diffraction measurements following the loss of water suggesting changes on the local structure are important. Highlights: → The average structures of the defect perovskites Sr 2 MSbO 5.5 established. → Anion and cation disorder quantified by neutron and synchrotron X-ray diffraction. → Anomalous thermal expansion due to local clustering of anions and vacancies observed.

  20. Two-Photon Absorption in Organometallic Bromide Perovskites

    KAUST Repository

    Walters, Grant

    2015-07-21

    Organometallic trihalide perovskites are solution processed semiconductors that have made great strides in third generation thin film light harvesting and light emitting optoelectronic devices. Recently it has been demonstrated that large, high purity single crystals of these perovskites can be synthesized from the solution phase. These crystals’ large dimensions, clean bandgap, and solid-state order, have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW-1 at 800 nm, comparable to epitaxial single crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

  1. Two-Photon Absorption in Organometallic Bromide Perovskites

    KAUST Repository

    Walters, Grant; Sutherland, Brandon R; Hoogland, Sjoerd; Shi, Dong; Comin, Riccardo; Sellan, Daniel P.; Bakr, Osman; Sargent, Edward H.

    2015-01-01

    Organometallic trihalide perovskites are solution processed semiconductors that have made great strides in third generation thin film light harvesting and light emitting optoelectronic devices. Recently it has been demonstrated that large, high purity single crystals of these perovskites can be synthesized from the solution phase. These crystals’ large dimensions, clean bandgap, and solid-state order, have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW-1 at 800 nm, comparable to epitaxial single crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

  2. Reduced-fat Gouda-type cheese enriched with vitamin D3 effectively prevents vitamin D deficiency during winter months in postmenopausal women in Greece.

    Science.gov (United States)

    Manios, Yannis; Moschonis, George; Mavrogianni, Christina; van den Heuvel, Eghm; Singh-Povel, Cécile M; Kiely, Mairead; Cashman, Kevin D

    2017-10-01

    The primary aim of the present study was to examine the effectiveness of daily consumption of vitamin D 3 -enriched, reduced-fat Gouda-type cheese on 25-hydroxyvitamin D (25(OH)D) concentration in postmenopausal women. Health-related quality of life (HRQL) indices were examined as secondary outcomes. This is a single-blinded (i.e., to study participants), randomized, controlled food-based dietary intervention study. A sample of 79 postmenopausal women (55-75 years old) was randomized either to a control group (CG: n = 39) or an intervention group (IG: n = 40) that consumed, as part of their usual diet, 60 g of either non-enriched or vitamin D 3 enriched Gouda-type cheese, respectively, for eight consecutive weeks (i.e., from January to March 2015). Sixty grams of enriched cheese provided a daily dose of 5.7 μg of vitamin D 3 . There was a differential response of mean (95 % CI) serum 25(OH)D levels in the IG and CG, with the former increasing and the latter decreasing significantly over the eight weeks of the trial [i.e., by 5.1 (3.4, 6.9) nmol/L vs. -4.6 (-6.4, -2.8) nmol/L, P D levels  0.1). Consumption of 60 g of vitamin D 3 -enriched, reduced-fat Gouda-type cheese provided a daily dose of 5.7 μg of additional vitamin D 3 and was effective in increasing mean serum 25(OH)D concentration and in counteracting vitamin D deficiency during winter months in postmenopausal women in Greece.

  3. Improving the Morphology of the Perovskite Absorber Layer in Hybrid Organic/Inorganic Halide Perovskite MAPbI3 Solar Cells

    Directory of Open Access Journals (Sweden)

    I. J. Ogundana

    2017-01-01

    Full Text Available Recently, perovskite solar cells have attracted tremendous attention due to their excellent power conversion efficiency, low cost, simple fabrications, and high photovoltaic performance. Furthermore, the perovskite solar cells are lightweight and possess thin film and semitransparency. However, the nonuniformity in perovskite layer constitutes a major setback to the operation mechanism, performance, reproducibility, and degradation of perovskite solar cells. Therefore, one of the main challenges in planar perovskite devices is the fabrication of high quality films with controlled morphology and least amount of pin-holes for high performance thin film perovskite devices. The poor reproducibility in perovskite solar cells hinders the accurate fabrication of practical devices for use in real world applications, and this is primarily as a result of the inability to control the morphology of perovskites, leading to large variability in the characteristics of perovskite solar cells. Hence, the focus of research in perovskites has been mostly geared towards improving the morphology and crystallization of perovskite absorber by selecting the optimal annealing condition considering the effect of humidity. Here we report a controlled ambient condition that is necessary to grow uniform perovskite crystals. A best PCE of 7.5% was achieved along with a short-circuit current density of 15.2 mA/cm2, an open-circuit voltage of 0.81 V, and a fill factor of 0.612 from the perovskite solar cell prepared under 60% relative humidity.

  4. Pyridine-induced Dimensionality Change in Hybrid Perovskite Nanocrystals

    KAUST Repository

    Ahmed, Ghada H.; Yin, Jun; Bose, Riya; Sinatra, Lutfan; Alarousu, Erkki; Yengel, Emre; AlYami, Noktan; Saidaminov, Makhsud I.; Zhang, Yuhai; Hedhili, Mohamed N.; Bakr, Osman; Bredas, Jean-Luc; Mohammed, Omar F.

    2017-01-01

    of pyridine during the synthesis of methylammonium lead bromide (MAPbBr) perovskite nanocrystals can transform three-dimensional (3D) cubes into two-dimensional (2D) nanostructures. Density functional theory (DFT) calculations show that pyridine preferentially

  5. Truncated recombinant human SP-D attenuates emphysema and type II cell changes in SP-D deficient mice

    Directory of Open Access Journals (Sweden)

    Mühlfeld Christian

    2007-10-01

    Full Text Available Abstract Background Surfactant protein D (SP-D deficient mice develop emphysema-like pathology associated with focal accumulations of foamy alveolar macrophages, an excess of surfactant phospholipids in the alveolar space and both hypertrophy and hyperplasia of alveolar type II cells. These findings are associated with a chronic inflammatory state. Treatment of SP-D deficient mice with a truncated recombinant fragment of human SP-D (rfhSP-D has been shown to decrease the lipidosis and alveolar macrophage accumulation as well as production of proinflammatory chemokines. The aim of this study was to investigate if rfhSP-D treatment reduces the structural abnormalities in parenchymal architecture and type II cells characteristic of SP-D deficiency. Methods SP-D knock-out mice, aged 3 weeks, 6 weeks and 9 weeks were treated with rfhSP-D for 9, 6 and 3 weeks, respectively. All mice were sacrificed at age 12 weeks and compared to both PBS treated SP-D deficient and wild-type groups. Lung structure was quantified by design-based stereology at the light and electron microscopic level. Emphasis was put on quantification of emphysema, type II cell changes and intracellular surfactant. Data were analysed with two sided non-parametric Mann-Whitney U-test. Main Results After 3 weeks of treatment, alveolar number was higher and mean alveolar size was smaller compared to saline-treated SP-D knock-out controls. There was no significant difference concerning these indices of pulmonary emphysema within rfhSP-D treated groups. Type II cell number and size were smaller as a consequence of treatment. The total volume of lamellar bodies per type II cell and per lung was smaller after 6 weeks of treatment. Conclusion Treatment of SP-D deficient mice with rfhSP-D leads to a reduction in the degree of emphysema and a correction of type II cell hyperplasia and hypertrophy. This supports the concept that rfhSP-D might become a therapeutic option in diseases that are

  6. Large intragrain magnetoresistance above room temperature in the double perovskite Ba2FeMoO6

    International Nuclear Information System (INIS)

    Maignan, A.; Raveau, B.; Martin, C.; Hervieu, M.

    1999-01-01

    Large intragrain magnetoresistance (MR) in the ordered double perovskite, Ba 2 FeMo 6 , is shown for the first time. The latter appears near T c (340 K), i.e., above room temperature. This effect originates from a double-exchange-like mechanism, based on antiferromagnetic coupling of localized high spin 3d 5 Fe 3+ , and itinerant 4d 1 Mo 5+ species. Besides this bulk MR, low field tunneling MR at lower temperatures (T 2 FeMoO 6 . Such a coexistence of both effects, intragrain and intergrain magnetoresistance, might extend to all members of this double perovskite family, suggesting the possibility of optimizing the MR for working at room temperature in a low magnetic field, by tuning the T c of solid solutions of such perovskites

  7. CD1d deficiency inhibits the development of abdominal aortic aneurysms in LDL receptor deficient mice.

    Directory of Open Access Journals (Sweden)

    Gijs H M van Puijvelde

    Full Text Available An abdominal aortic aneurysm (AAA is a dilatation of the abdominal aorta leading to serious complications and mostly to death. AAA development is associated with an accumulation of inflammatory cells in the aorta including NKT cells. An important factor in promoting the recruitment of these inflammatory cells into tissues and thereby contributing to the development of AAA is angiotensin II (Ang II. We demonstrate that a deficiency in CD1d dependent NKT cells under hyperlipidemic conditions (LDLr-/-CD1d-/- mice results in a strong decline in the severity of angiotensin II induced aneurysm formation when compared with LDLr-/- mice. In addition, we show that Ang II amplifies the activation of NKT cells both in vivo and in vitro. We also provide evidence that type I NKT cells contribute to AAA development by inducing the expression of matrix degrading enzymes in vSMCs and macrophages, and by cytokine dependently decreasing vSMC viability. Altogether, these data prove that CD1d-dependent NKT cells contribute to AAA development in the Ang II-mediated aneurysm model by enhancing aortic degradation, establishing that therapeutic applications which target NKT cells can be a successful way to prevent AAA development.

  8. Selective self-assembly and light emission tuning of layered hybrid perovskites on patterned graphene.

    Science.gov (United States)

    Guerra, Valentino L P; Kovaříček, Petr; Valeš, Václav; Drogowska, Karolina; Verhagen, Tim; Vejpravova, Jana; Horák, Lukáš; Listorti, Andrea; Colella, Silvia; Kalbáč, Martin

    2018-02-15

    The emission of light in two-dimensional (2-D) layered hybrid organic lead halide perovskites, namely (R-NH 3 ) 2 PbX 4 , can be effectively tuned using specific building blocks for the perovskite formation. Herein this behaviour is combined with a non-covalent graphene functionalization allowing excellent selectivity and spatial resolution of the perovskite film growth, promoting the formation of hybrid 2-D perovskite : graphene heterostructures with uniform coverage of up to centimeter scale graphene sheets and arbitrary shapes down to 5 μm. Using cryo-Raman microspectroscopy, highly resolved spectra of the perovskite phases were obtained and the Raman mapping served as a convenient spatially resolved technique for monitoring the distribution of the perovskite and graphene constituents on the substrate. In addition, the stability of the perovskite phase with respect to the thermal variation was inspected in situ by X-ray diffraction. Finally, time-resolved photoluminescence characterization demonstrated that the optical properties of the perovskite films grown on graphene are not hampered. Our study thus opens the door to smart fabrication routes for (opto)-electronic devices based on 2-D perovskites in contact with graphene with complex architectures.

  9. Maternal vitamin D deficiency associated with neonatal hypocalcaemic convulsions

    Directory of Open Access Journals (Sweden)

    Tibbott Rebecca

    2007-09-01

    Full Text Available Abstract Maternal vitamin D insufficiency is not uncommon. Infants born to mothers who are deficient in vitamin D and or calcium, usually due to cultural modifications in their diets or clothing habits, and in addition are breastfed, are at risk of developing vitamin D deficiency and hypocalcaemia. We present a case of neonatal hypocalcaemic seizures secondary to vitamin D deficiency. Rickets in children resulting from vitamin D deficiency is well documented. It is also becoming clear that there is a positive correlation between maternal vitamin D status during pregnancy and lactation and the development of rickets both in infancy and childhood. The correlation between maternal vitamin D, neonatal vitamin D and hypocalcaemia is not well documented.

  10. Rickets–vitamin D deficiency and dependency

    Science.gov (United States)

    Sahay, Manisha; Sahay, Rakesh

    2012-01-01

    Rickets is an important problem even in countries with adequate sun exposure. The causes of rickets/osteomalacia are varied and include nutritional deficiency, especially poor dietary intake of vitamin D and calcium. Non-nutritional causes include hypophosphatemic rickets primarily due to renal phosphate losses and rickets due to renal tubular acidosis. In addition, some varieties are due to inherited defects in vitamin D metabolism and are called vitamin D dependent rickets. This chapter highlights rickets/osteomalacia related to vitamin D deficiency or to inherited defects in vitamin D metabolism. Hypophosphatemic rickets and rickets due to renal tubular acidosis are discussed in other sections of the journal. PMID:22470851

  11. Rickets-vitamin D deficiency and dependency

    Directory of Open Access Journals (Sweden)

    Manisha Sahay

    2012-01-01

    Full Text Available Rickets is an important problem even in countries with adequate sun exposure. The causes of rickets/osteomalacia are varied and include nutritional deficiency, especially poor dietary intake of vitamin D and calcium. Non-nutritional causes include hypophosphatemic rickets primarily due to renal phosphate losses and rickets due to renal tubular acidosis. In addition, some varieties are due to inherited defects in vitamin D metabolism and are called vitamin D dependent rickets. This chapter highlights rickets/osteomalacia related to vitamin D deficiency or to inherited defects in vitamin D metabolism. Hypophosphatemic rickets and rickets due to renal tubular acidosis are discussed in other sections of the journal.

  12. Prevalence of vitamin D deficiency orthopedic practice-A study in Karachi

    International Nuclear Information System (INIS)

    Azam, N.; Awan, A.J.

    2012-01-01

    Objective: To study the prevalence of vit D deficiency in Karachi by evaluating the levels of vit D in patients reporting to an orthopaedic out patients department (OPD) with complaints of persistent 'r backache or generalized aches and pains. Study Design: Cross sectional descriptive study. Place and duration of study: From Aug 2008 to May 2009 in orthopaedic OPD of Pakistan Steel Mills Hospital Karachi. Patients and Methods: A non probability convenience sample was taken from 334 patients referred to orthopaedic specialist by primary care physicians for persistent backache and or generalized aches and pains, minimum for the last 6 months. A total 89 patients were included keeping in view the exclusion criteria. X-ray lumbosacral spine, and serum Vitamin D levels were advised in all cases. The normal range is 40-100 ng/ml. Value of 20-39 ng/ml was taken as mild deficiency, 5-19 ng/ml was considered as moderate and < 5 ng/ml was noted as severe deficiency. Results: There were 73 (82%) females and 16(18%) males. Mean Vitamin D3 level estimated in the study population was 7.76 ng/ml (SD= 3.50). Mean age was 40.2 years +- 10.75. Serum Vitamin D3 levels were checked and found to be moderately low in 75% of cases checked. Conclusion: Vitamin D deficiency constitutes a common reason of morbidity in Pakistan and deserves to be considered in the common differential diagnosis of backache and unexplained aches and pains. (author)

  13. First-principles prediction of structural, elastic, electronic and thermodynamic properties of the cubic SrUO{sub 3}-Perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Sahli, B. [Laboratoire de Génie Physique, Université Ibn Khaldoun, Tiaret, 14000 (Algeria); Laboratoire des Matériaux Magnétiques, Université Djillali Liabés, Sidi Bel-Abbes 22000 (Algeria); Bouafia, H., E-mail: hamza.tssm@gmail.com [Laboratoire de Génie Physique, Université Ibn Khaldoun, Tiaret, 14000 (Algeria); Abidri, B.; Abdellaoui, A. [Laboratoire des Matériaux Magnétiques, Université Djillali Liabés, Sidi Bel-Abbes 22000 (Algeria); Hiadsi, S.; Akriche, A. [Laboratoire de Microscope Electronique et Sciences des Matériaux, Université des Sciences et de la Technologie Mohamed Boudiaf, département de Génie Physique, BP1505 El m’naouar, Oran (Algeria); Benkhettou, N.; Rached, D. [Laboratoire des Matériaux Magnétiques, Université Djillali Liabés, Sidi Bel-Abbes 22000 (Algeria)

    2015-06-25

    Highlights: • The ground state properties of SrUO{sub 3}-Perovskite were investigated. • Elastic constants and their related parameters were calculated. • Electronic properties are treated using GGA-PBEsol + U approach. - Abstract: In this paper, we investigate bulk properties of the cubic SrUO{sub 3}-Perovskite in their nonmagnetic (NM), antiferromagnetic (AFM) and ferromagnetic (FM) states using all-electron self consistent Full Potential Augmented Plane Waves plus local orbital (FP-(L)APW + lo) method within PBEsol Generalized Gradiant density approximations. Our calculation allowed us to predict that the more stable magnetic state of the cubic SrUO{sub 3}-Perovskite is that of the ferromagnetic (FM). This work is the first prediction of elastic constants and their related parameters (Young modulus, shear modulus, Poisson ratio, Zener anisotropy and the Debye temperature) for this cubic compound using Mehl method. We have employed the GGA(PBEsol) and GGA(PBEsol) + U to investigate the electronic band structure, density of states and electronic charge density of SrUO{sub 3}-Perovskite. The electronic band structure calculations revealed that SrUO{sub 3} exhibits metallic behavior. On the other hand the charge density plots for [1 1 0] direction indicates a strong ionic character along the Sr–O bond while the U–O bond has strong covalent character. Finally, we have analyzed the thermodynamic properties using the quasi-harmonic Debye model to complete the fundamental characterization of cubic SrUO{sub 3}-Perovskite.

  14. High Prevalence of Vitamin D Deficiency among Pregnant Saudi Women.

    Science.gov (United States)

    Al-Faris, Nora A

    2016-02-04

    Vitamin D deficiency has emerged as a public health problem worldwide due to its important role in health and disease. The present work is intended to examine prevalence of vitamin D deficiency among pregnant Saudi women and related risk factors. A cross-sectional study was carried out at King Fahad Medical City in Riyadh, Saudi Arabia. Serum 25-hydroxy vitamin D (25(OH)D) was measured by enzyme-linked immunosorbent assay in 160 pregnant women during the first trimester of pregnancy. Socio-demographic, lifestyle and maternal characteristics were collected and vitamin D intake was assessed using a 24-h dietary recall. Weight and height were measured using standardized methods. Vitamin D deficiency (25(OH)D L) and insufficiency (25(OH)D = 50-74 nmol/L) were reported in 50% and 43.8% of the study sample, respectively. Median serum 25(OH)D concentration was 49.9 nmol/L. Adequate vitamin D intake (≥600 IU/day) was reported among only 8.1% of pregnant women. Age group, educational level, sun exposure frequency and daytime and daily practice of exercise were significantly associated with vitamin D status. Overall, vitamin D deficiency was common among pregnant Saudi women in Riyadh. Steps should be taken to address the current situation, including increased sunlight exposure, consumption of fatty fish, and vitamin D supplements.

  15. Genetic KCa3.1-deficiency produces locomotor hyperactivity and alterations in cerebral monoamine levels.

    Directory of Open Access Journals (Sweden)

    Kate Lykke Lambertsen

    Full Text Available The calmodulin/calcium-activated K(+ channel KCa3.1 is expressed in red and white blood cells, epithelia and endothelia, and possibly central and peripheral neurons. However, our knowledge about its contribution to neurological functions and behavior is incomplete. Here, we investigated whether genetic deficiency or pharmacological activation of KCa3.1 change behavior and cerebral monoamine levels in mice.In the open field test, KCa3.1-deficiency increased horizontal activity, as KCa3.1(-/- mice travelled longer distances (≈145% of KCa3.1(+/+ and at higher speed (≈1.5-fold of KCa3.1(+/+. Working memory in the Y-maze was reduced by KCa3.1-deficiency. Motor coordination on the rotarod and neuromuscular functions were unchanged. In KCa3.1(-/- mice, HPLC analysis revealed that turn-over rates of serotonin were reduced in frontal cortex, striatum and brain stem, while noradrenalin turn-over rates were increased in the frontal cortex. Dopamine turn-over rates were unaltered. Plasma catecholamine and corticosterone levels were unaltered. Intraperitoneal injections of 10 mg/kg of the KCa3.1/KCa2-activator SKA-31 reduced rearing and turning behavior in KCa3.1(+/+ but not in KCa3.1(-/- mice, while 30 mg/kg SKA-31 caused strong sedation in 50% of the animals of either genotypes. KCa3.1(-/- mice were hyperactive (≈+60% in their home cage and SKA-31-administration reduced nocturnal physical activity in KCa3.1(+/+ but not in KCa3.1(-/- mice.KCa3.1-deficiency causes locomotor hyperactivity and altered monoamine levels in selected brain regions, suggesting a so far unknown functional link of KCa3.1 channels to behavior and monoaminergic neurotransmission in mice. The tranquilizing effects of low-dose SKA-31 raise the possibility to use KCa3.1/KCa2 channels as novel pharmacological targets for the treatment of neuropsychiatric hyperactivity disorders.

  16. Morphology-photovoltaic property correlation in perovskite solar cells: One-step versus two-step deposition of CH3NH3PbI3

    Directory of Open Access Journals (Sweden)

    Jeong-Hyeok Im

    2014-08-01

    Full Text Available Perovskite CH3NH3PbI3 light absorber is deposited on the mesoporous TiO2 layer via one-step and two-step coating methods and their photovoltaic performances are compared. One-step coating using a solution containing CH3NH3I and PbI2 shows average power conversion efficiency (PCE of 7.5%, while higher average PCE of 13.9% is obtained from two-step coating method, mainly due to higher voltage and fill factor. The coverage, pore-filling, and morphology of the deposited perovskite are found to be critical in photovoltaic performance of the mesoporous TiO2 based perovskite solar cells.

  17. Synthesis and luminescence properties of KMgF{sub 3}:Tm{sup 3+} fluoro perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Perez C, L.; Cruz Z, E. [UNAM, Instituto de Ciencias Nucleares, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Marcazzo, J. [UNICEN, Instituto de Fisica Arroyo Seco, Gral. Pinto 399, B7000GHG Tandil (Argentina); Hernandez A, J. M.; Murrieta S, H., E-mail: ecruz@nucleares.unam.mx [UNAM, Instituto de Fisica, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico)

    2015-10-15

    This paper presents the thermoluminescent (Tl) and radio luminescent (Rl) properties of the KMgF{sub 3} doped with Tm{sup 3+} ions at different concentration (0.05, 0.1, 0.2, 0.5 and 1.0 mol %). The KMgF{sub 3} binary compound was synthesized by solid state reaction. The characterization of the powder material was carried out by X-ray diffraction, scanning electron microscopy and by semiquantitative EDS analysis. The luminescence property of the powder and chips with Teflon samples was studied by thermoluminescence and radioluminescence phenomena. The Tl response as a function of the given dose was analyzed in the range between 0.5 Gy and 2500 Gy and a good linear response was obtained. Tl glow curves of KMgF{sub 3}:Tm show two overlapped peaks with maximums about 101, 146 degrees C and resolved peaks at 313 and 397 degrees C. The reproducibility of the Tl signal was tested and less than 5 % was obtained. The Tl signal decay was analyzed during a period of 33 days. Furthermore, the glow curve structure was studied by the thermal bleaching and the kinetics parameters values were obtained by a deconvolution process. On the other hand, the Rl response of different concentrations of thulium under beta irradiation was studied and the maximum of light output has been obtained for KMgF{sub 3} fluoro perovskite doped with 0.5 mol % of Tm{sup 3+} . The Rl spectrum showed the emission peaks at 455 and 360 nm, which can be ascribed to the {sup 1}D{sub 2}-{sup 3} F{sub 4} and {sup 1}D{sub 2}-{sup 3}H{sub 6} transitions of the Tm{sup 3+} ions. (Author)

  18. Ketone Bodies as a Possible Adjuvant to Ketogenic Diet in PDHc Deficiency but Not in GLUT1 Deficiency.

    Science.gov (United States)

    Habarou, F; Bahi-Buisson, N; Lebigot, E; Pontoizeau, C; Abi-Warde, M T; Brassier, A; Le Quan Sang, K H; Broissand, C; Vuillaumier-Barrot, S; Roubertie, A; Boutron, A; Ottolenghi, C; de Lonlay, P

    2018-01-01

    Ketogenic diet is the first line therapy for neurological symptoms associated with pyruvate dehydrogenase deficiency (PDHD) and intractable seizures in a number of disorders, including GLUT1 deficiency syndrome (GLUT1-DS). Because high-fat diet raises serious compliance issues, we investigated if oral L,D-3-hydroxybutyrate administration could be as effective as ketogenic diet in PDHD and GLUT1-DS. We designed a partial or total progressive substitution of KD with L,D-3-hydroxybutyrate in three GLUT1-DS and two PDHD patients. In GLUT1-DS patients, we observed clinical deterioration including increased frequency of seizures and myoclonus. In parallel, ketone bodies in CSF decreased after introducing 3-hydroxybutyrate. By contrast, two patients with PDHD showed clinical improvement as dystonic crises and fatigability decreased under basal metabolic conditions. In one of the two PDHD children, 3-hydroxybutyrate has largely replaced the ketogenic diet, with the latter that is mostly resumed only during febrile illness. Positive direct effects on energy metabolism in PDHD patients were suggested by negative correlation between ketonemia and lactatemia (r 2  = 0.59). Moreover, in cultured PDHc-deficient fibroblasts, the increase of CO 2 production after 14 C-labeled 3-hydroxybutyrate supplementation was consistent with improved Krebs cycle activity. However, except in one patient, ketonemia tended to be lower with 3-hydroxybutyrate administration compared to ketogenic diet. 3-hydroxybutyrate may be an adjuvant treatment to ketogenic diet in PDHD but not in GLUT1-DS under basal metabolic conditions. Nevertheless, ketogenic diet is still necessary in PDHD patients during febrile illness.

  19. Critical Intermediate Structure That Directs the Crystalline Texture and Surface Morphology of Organo-Lead Trihalide Perovskite.

    Science.gov (United States)

    Chia, Hao-Chung; Sheu, Hwo-Shuenn; Hsiao, Yu-Yun; Li, Shao-Sian; Lan, Yi-Kang; Lin, Chung-Yao; Chang, Je-Wei; Kuo, Yen-Chien; Chen, Chia-Hao; Weng, Shih-Chang; Su, Chun-Jen; Su, An-Chung; Chen, Chun-Wei; Jeng, U-Ser

    2017-10-25

    We have identified an often observed yet unresolved intermediate structure in a popular processing with dimethylformamide solutions of lead chloride and methylammonium iodide for perovskite solar cells. With subsecond time-resolved grazing-incidence X-ray scattering and X-ray photoemission spectroscopy, supplemental with ab initio calculation, the resolved intermediate structure (CH 3 NH 3 ) 2 PbI 2 Cl 2 ·CH 3 NH 3 I features two-dimensional (2D) perovskite bilayers of zigzagged lead-halide octahedra and sandwiched CH 3 NH 3 I layers. Such intermediate structure reveals a hidden correlation between the intermediate phase and the composition of the processing solution. Most importantly, the 2D perovskite lattice of the intermediate phase is largely crystallographically aligned with the [110] planes of the three-dimensional perovskite cubic phase; consequently, with sublimation of Cl ions from the organo-lead octahedral terminal corners in prolonged annealing, the zigzagged octahedral layers of the intermediate phase can merge with the intercalated methylammonium iodide layers for templated growth of perovskite crystals. Regulated by annealing temperature and the activation energies of the intermediate and perovskite, deduced from analysis of temperature-dependent structural kinetics, the intermediate phase is found to selectively mature first and then melt along the layering direction for epitaxial conversion into perovskite crystals. The unveiled epitaxial conversion under growth kinetics controls might be general for solution-processed and intermediate-templated perovskite formation.

  20. Crystallographic and Electronic Structure of the Sr3Sb2CoO9 Triple Perovskite

    International Nuclear Information System (INIS)

    González, W; Téllez, D A Landínez; Roa-Rojas, J; Cardona, R

    2014-01-01

    Compounds The perovskites are materials with physical and chemical characteristics that make them optimal for application in the technological and scientist. When the ideal formula of perovskite ABO 3 is modified by introducing a special structural arrangement can get to get triple perovskites, which correspond to the formula A 3 B 2 B'O 9 . In this work we report the synthesis process and the study of electronic structure and crystal Sr 3 Sb 2 CoO 9 new triple perovskite. From the experiments of X-ray Diffraction and the application of the Rietveld refinement method was revealed that the system crystallizes in a perovskite structure with a characteristic triple given by the space group Immm (#71) and lattice parameters a=9.791(9) Å, b=5.656(7) Å and c=16.957(8) Å. Ab initio calculations of density of states (DOS) and electronic structure were carried out for this perovskite-like system by using the Quantum EXPRESSO code. The exchange-correlation potential was treated using the Generalized Gradient Approximation (GGA). All calculations were carried-out using spin polarization.

  1. Enhanced photovoltaic performance of CH3NH3PbBrXI3-X-based perovskite solar cells via anti-solvent extraction

    Science.gov (United States)

    Jiang, Zhaoyi; Zhang, Weijia; Lu, Chaoqun; Ma, Denghao; Liu, Haixu; Yu, Wei; Zhang, Yu; Ma, Qiang; Zhang, Yulong

    2018-06-01

    In this paper, the two-step sequential deposition method was used to prepare the CH3NH3PbBrXI3-X films by introducing CH3NH3Br in the precursors. The surface morphology of the PbI2 films was controlled by anti-solvent extraction (ASE) to improve the microstructure and photo-physical properties of the perovskite films. It was noteworthy that, compared to the compact PbI2 films, the porous PbI2 films facilitated the growth of crystals and bromine incorporation in films, and the prepared perovskite films exhibited enlarged grain size, increased light absorption, enhanced Br incorporation and prolonged carrier lifetime, which resulted in excellent photo-electrical properties of the CH3NH3PbBrXI3-X films. With porous PbI2 templates, the inverted planar perovskite solar cells based on films with appropriate Br incorporation (CH3NH3Br/CH3NH3I mole ratio = 3/7) showed a photovoltaic conversion efficiency (PCE) of 14.9%, and the stability of the devices in air was elevated. Consequently, the high-quality CH3NH3PbBrXI3-X films can be obtained with porous PbI2 templates for improving the performance of the perovskite solar cells.

  2. Dual-Function Au@Y2O3:Eu3+ Smart Film for Enhanced Power Conversion Efficiency and Long-Term Stability of Perovskite Solar Cells.

    Science.gov (United States)

    Kim, Chang Woo; Eom, Tae Young; Yang, In Seok; Kim, Byung Su; Lee, Wan In; Kang, Yong Soo; Kang, Young Soo

    2017-07-28

    In the present study, a dual-functional smart film combining the effects of wavelength conversion and amplification of the converted wave by the localized surface plasmon resonance has been investigated for a perovskite solar cell. This dual-functional film, composed of Au nanoparticles coated on the surface of Y 2 O 3 :Eu 3+ phosphor (Au@Y 2 O 3 :Eu 3+ ) nanoparticle monolayer, enhances the solar energy conversion efficiency to electrical energy and long-term stability of photovoltaic cells. Coupling between the Y 2 O 3 :Eu 3+ phosphor monolayer and ultraviolet solar light induces the latter to be converted into visible light with a quantum yield above 80%. Concurrently, the Au nanoparticle monolayer on the phosphor nanoparticle monolayer amplifies the converted visible light by up to 170%. This synergy leads to an increased solar light energy conversion efficiency of perovskite solar cells. Simultaneously, the dual-function film suppresses the photodegradation of perovskite by UV light, resulting in long-term stability. Introducing the hybrid smart Au@Y 2 O 3 :Eu 3+ film in perovskite solar cells increases their overall solar-to-electrical energy conversion efficiency to 16.1% and enhances long-term stability, as compared to the value of 15.2% for standard perovskite solar cells. The synergism between the wavelength conversion effect of the phosphor nanoparticle monolayer and the wave amplification by the localized surface plasmon resonance of the Au nanoparticle monolayer in a perovskite solar cell is comparatively investigated, providing a viable strategy of broadening the solar spectrum utilization.

  3. Reversible Changes in Resistance of Perovskite Nickelate NdNiO3 Thin Films Induced by Fluorine Substitution.

    Science.gov (United States)

    Onozuka, Tomoya; Chikamatsu, Akira; Katayama, Tsukasa; Hirose, Yasushi; Harayama, Isao; Sekiba, Daiichiro; Ikenaga, Eiji; Minohara, Makoto; Kumigashira, Hiroshi; Hasegawa, Tetsuya

    2017-03-29

    Perovskite nickel oxides are of fundamental as well as technological interest because they show large resistance modulation associated with phase transition as a function of the temperature and chemical composition. Here, the effects of fluorine doping in perovskite nickelate NdNiO 3 epitaxial thin films are investigated through a low-temperature reaction with polyvinylidene fluoride as the fluorine source. The fluorine content in the fluorinated NdNiO 3-x F x films is controlled with precision by varying the reaction time. The fully fluorinated film (x ≈ 1) is highly insulating and has a bandgap of 2.1 eV, in contrast to NdNiO 3 , which exhibits metallic transport properties. Hard X-ray photoelectron and soft X-ray absorption spectroscopies reveal the suppression of the density of states at the Fermi level as well as the reduction of nickel ions (valence state changes from +3 to +2) after fluorination, suggesting that the strong Coulombic repulsion in the Ni 3d orbitals associated with the fluorine substitution drives the metal-to-insulator transition. In addition, the resistivity of the fluorinated films recovers to the original value for NdNiO 3 after annealing in an oxygen atmosphere. By application of the reversible fluorination process to transition-metal oxides, the search for resistance-switching materials could be accelerated.

  4. Osteomalacia as a result of vitamin D deficiency.

    Science.gov (United States)

    Bhan, Arti; Rao, Ajay D; Rao, D Sudhaker

    2010-06-01

    Osteomalacia is an end-stage bone disease of chronic and severe vitamin D or phosphate depletion of any cause. Its importance has increased because of the rising incidence of vitamin D deficiency. Yet, not all cases of osteomalacia are cured by vitamin D replacement, and furthermore, not all individuals with vitamin D deficiency develop osteomalacia. Although in the past osteomalacia was commonly caused by malabsorption, nutritional deficiency now is more common. In addition, recent literature suggests that nutritional vitamin D deficiency osteomalacia follows various bariatric surgeries for morbid obesity. Bone pain, tenderness, muscle weakness, and difficulty walking are all common clinical manifestations of osteomalacia. Diagnostic work-up involves biochemical assessment of vitamin D status and may also include a transiliac bone biopsy. Treatment is based on aggressive vitamin D repletion in most cases with follow-up biopsies if patients are started on antiresorptive or anabolic agents. Copyright 2010 Elsevier Inc. All rights reserved.

  5. Vitamin D3 Loading Is Superior to Conventional Supplementation After Weight Loss Surgery in Vitamin D-Deficient Morbidly Obese Patients: a Double-Blind Randomized Placebo-Controlled Trial.

    Science.gov (United States)

    Luger, Maria; Kruschitz, Renate; Kienbacher, Christian; Traussnigg, Stefan; Langer, Felix B; Prager, Gerhard; Schindler, Karin; Kallay, Enikö; Hoppichler, Friedrich; Trauner, Michael; Krebs, Michael; Marculescu, Rodrig; Ludvik, Bernhard

    2017-05-01

    Bariatric patients often suffer from vitamin D deficiency (VDD), and both, morbid obesity and VDD, are related to non-alcoholic fatty liver disease. However, limited data are available regarding best strategies for treating VDD, particularly, in bariatric patients undergoing omega-loop gastric bypass (OLGB). Therefore, we examined the efficacy and safety of a forced vitamin D dosing regimen and intervention effects in liver fibrotic patients. In this double-blind, randomized, placebo-controlled trial, 50 vitamin D-deficient patients undergoing OLGB were randomly assigned to receive, in the first month postoperatively, oral vitamin D 3 (≤3 doses of 100,000 IU; intervention group) or placebo as loading dose (control group) with subsequent maintenance dose (3420 IU/day) in both groups until 6-month visit. Compared with control group, higher increase of 25(OH)D (67.9 (21.1) vs. 55.7 nmol/L (21.1); p = 0.049) with lower prevalence of secondary hyperparathyroidism (10 vs. 24 %; p = 0.045) was observed in intervention group. No (serious) adverse events related to study medication were found. The loading dose regimen was more effective in increasing 25(OH)D in patients with significant liver fibrosis while this was not the case for conventional supplementation (placebo with maintenance dose) (71.5 (20.5) vs. 22.5 nmol/L (13.8); p = 0.022; n = 14). Our findings indicate that a high vitamin D 3 loading dose, in the first month postoperatively, with subsequent maintenance dose is effective and safe in achieving higher vitamin D concentrations in OLGB patients. Unexpectedly, it is more effective in patients with significant liver fibrosis which is of potentially high clinical relevance and requires further investigation.

  6. Pseudovitamin D deficiency rickets—a report from the Indian subcontinent

    Science.gov (United States)

    Zargar, A. H.; Mithal, A.; Wani, A. I.; Laway, B. A.; Masoodi, S. R.; Bashir, M. I.; Ganie, M. A.

    2000-01-01

    Pseudovitamin D deficiency rickets (also called vitamin D dependent rickets type I) is one of the types of inherited rickets and is caused by a deficit in renal 25-hydroxyvitamin D 1α-hydroxylase. This form of rickets has not been reported from the Indian subcontinent. Three patients with this disorder are presented. These patients were all females aged 3-20 years and presented with growth failure and skeletal deformities. All had florid clinical and radiological rickets. The biochemical abnormalities seen included hypocalcaemia, hypophosphataemia, and hyperphosphatasia. All patients had grossly raised 25-hydroxyvitamin D concentrations and markedly low to undetectable concentrations of 1,25-dihydroxyvitamin D. A disturbing feature of this study was the late referral of the patients.


Keywords: 1α-hydroxylase; calcitriol; inherited rickets; vitamin D dependent rickets PMID:10824056

  7. Synergic nature of dielectric relaxation process in the layered perovskite halide salts: The case of 1,3- diammoniumpropylenetetrabromocadmate compound

    Science.gov (United States)

    Staśkiewicz, Beata

    2018-06-01

    The negative thermal expansion (NTE) property was a prototype to discuss the origin of difference between classical Debye relaxation process and the non-Debye behavior in the layered perovskite halide salt of chemical formula NH3(CH2)3NH3CdBr4. The analysis has been taken by dielectric relaxation spectroscopy measurements in almost six decades in frequency 5 × 102 ≤ f(ω) ≤ 1.2 × 108 and in the temperature range 315 ≤ T(K) ≤ 390. It was shown that the investigated sample exhibit an antiferrodistortive nature of phase transition between two orthorhombic structural modifications i.e. Pnma (phase I) and Ima2 (phase II) at Tc1(I → II) = 326 K, leading from an antiferroelectric to a paraelectric phase. The involvement of an odd number of carbon atoms in the alkylammonium chains in dielectric properties of examined sample is proved. Higher structural modifications, i.e. Ima2 (phase II) and P21/m (phase III), have shown significant deviations from a regular circle on the Cole-Cole diagram. Presented experimental observations are essentially important for the theoretical explanation of relaxation processes in analyzed organic - inorganic compound crystallizing in a perovskite-like topology and may provide new perspective on the fundamental aspect of relaxation response in "diammonium" series.

  8. The lanthanum gallate-based mixed conducting perovskite ceramics

    Science.gov (United States)

    Politova, E. D.; Stefanovich, S. Yu.; Aleksandrovskii, V. V.; Kaleva, G. M.; Mosunov, A. V.; Avetisov, A. K.; Sung, J. S.; Choo, K. Y.; Kim, T. H.

    2005-01-01

    The structure, microstructure, dielectric, and transport properties of the anion deficient perovskite solid solutions (La,Sr)(Ga,Mg,M)O3- with M=Fe, Ni have been studied. Substitution of iron and nickel for gallium up to about 20 and 40 at.% respectively, leads to the perovskite lattice contraction due to the cation substitutions by the transition elements. The transition from pure ionic to mixed ionic-electronic conductivity was observed for both the systems studied. Both the enhancement of total conductivity and increasing in the thermal expansion coefficient values has been proved to correlate with the increasing amount of weakly bounded oxygen species in the Fe or Ni-doped ceramics. The oxygen ionic conductivity has been estimated from the kinetic experiments using the dc-conductivity and dilatometry methods under the condition of the stepwise change of the atmosphere from nitrogen to oxygen.

  9. All-perovskite transparent high mobility field effect using epitaxial BaSnO3 and LaInO3

    Directory of Open Access Journals (Sweden)

    Useong Kim

    2015-03-01

    Full Text Available We demonstrate an all-perovskite transparent heterojunction field effect transistor made of two lattice-matched perovskite oxides: BaSnO3 and LaInO3. We have developed epitaxial LaInO3 as the gate oxide on top of BaSnO3, which were recently reported to possess high thermal stability and electron mobility when doped with La. We measured the dielectric properties of the epitaxial LaInO3 films, such as the band gap, dielectric constant, and the dielectric breakdown field. Using the LaInO3 as a gate dielectric and the La-doped BaSnO3 as a channel layer, we fabricated field effect device structure. The field effect mobility of such device was higher than 90 cm2 V−1 s−1, the on/off ratio was larger than 107, and the subthreshold swing was 0.65 V dec−1. We discuss the possible origins for such device performance and the future directions for further improvement.

  10. Interspace modification of titania-nanorod arrays for efficient mesoscopic perovskite solar cells

    International Nuclear Information System (INIS)

    Chen, Peng; Jin, Zhixin; Wang, Yinglin; Wang, Meiqi; Chen, Shixin; Zhang, Yang; Wang, Lingling; Zhang, Xintong; Liu, Yichun

    2017-01-01

    Highlights: • The fabrication of perovskite solar cells utilizing TiO_2 NR arrays. • Investigation of the interspace effect of TiO_2 NR on perovskite layer. • Understanding of the balance between perovskite capping layer and pore filling. - Abstract: Morphology of electron transport layers (ETLs) has an important influence on the device architecture and electronic processes of mesostructured solar cells. In this work, we thoroughly investigated the effect of the interspace of TiO_2 nanorod (NR) arrays on the photovoltaic performance of the perovskite solar cells (PSCs). Along with the interspace in TiO_2-NR arrays increasing, the thickness as well as the crystal size of perovskite capping layer are reduced accordingly, and the filling of perovskite in the channel becomes incomplete. Electrochemical impedance spectroscopy measurements reveal that this variation of perovskite absorber layer, induced by interspace of TiO_2 NR arrays, causes the change of charge recombination process at the TiO_2/perovskite interface, suggesting that a balance between capping layer and the perovskite filling is critical to obtain high charge collection efficiency of PSCs. A power conversion efficiency of 10.3% could be achieved through careful optimization of interspace in TiO_2-NR arrays. Our research will shed light on the morphology control of ETLs with 1D structure for heterojunction solar cells fabricated by solution-deposited method.

  11. Inside Perovskites: Quantum Luminescence from Bulk Cs4PbBr6 Single Crystals

    KAUST Repository

    de Bastiani, Michele

    2017-08-01

    Zero-dimensional perovskite-related structures (0D-PRS) are a new frontier of perovskite-based materials. 0D-PRS, commonly synthesized in powder form, manifest distinctive optical properties such as strong photoluminescence (PL), narrow emission linewidth, and high exciton binding energy. These properties make 0D-PRS compelling for several types of optoelectronic applications, including phosphor screens and electroluminescent devices. However, it would not be possible to rationally design the chemistry and structure of these materials, without revealing the origins of their optical behaviour, which is contradictory to the well-studied APbX3 perovskites. In this work, we synthesize single crystals of Cs4PbBr6 0D-PRS, and investigated the origins of their unique optical and electronic properties. The crystals exhibit a PL quantum yield higher than 40%, the highest reported for perovskite-based single crystals. Time-resolved and temperature dependent PL studies, supported by DFT calculations, and structural analysis, elucidate an emissive behaviour reminiscent of a quantum confined structure rather than a typical bulk perovskite material.

  12. Time to Do Something for Vitamin D Deficiency; A Review

    Directory of Open Access Journals (Sweden)

    Mehrnoush Kosaryan

    2015-01-01

    Full Text Available Context: Vitamin D deficiency is a common nutritional disorder in Iran. Vitamin D is an essential health factor from birth onward. This study was conducted to summarize epidemiologic researches regarding vitamin D deficiency in different parts of the country and to conclude if food fortification is necessary. Evidence Acquisition: The study was designed in Thalassemia Research Center, Sari, Iran. It was a narrative review on the current situation of vitamin D deficiency in Iran. Related literature of the studies, in Farsi and English, conducted in the recent decade were explored. Data source of the study was Medline, SID, PubMed, Scopus, Request, Web-of-knowledge, Springer, Ovid, and Google Scholar. Results: Twenty five cross-sectional researches were found regarding vitamin D status in Iran from 2003 to 2013. There was also a Meta-analysis conducted in 2008. The total amount of 25(OH D3 was measured mostly by radio immune assay (RIA method. Most of the studies were done on adults. Definition of vitamin D deficiency was based on cut off of the kit in most studies; however in some studies the serum parathyroid hormone (PTH was measured and cut off for diagnosis based on increased PTH. Maximum rate of sever vitamin D deficiency was reported as 47% in 2011. Conclusions: Vitamin D deficiency is very frequent in Iran. Dealing with a national important nutritional problem is important. One way is to fortify suitable foods or edible products such as milk or cooking oil. Increasing public awareness about the problem and motivating people to do something on their expense is another option. In the current case taking vitamin D supplements on a regular basis, daily, weekly, or any other routines which could be available and cost effective may solve the problem. For people above one year old it is recommended to take 300’000 IU (as intramuscular injection or oral dose of vitamin D as a starting dose, then 50,000 IU oral dose every three months.

  13. FoxD3 deficiency promotes breast cancer progression by induction of epithelial–mesenchymal transition

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Tian-Li [Department of General Surgery, The People’s Hospital of Wuqing, Tianjin (China); Zhao, Hong-Meng [Key Laboratory of Breast Cancer Prevention and Treatment of the Ministry of Education, Tianjin Medical University Cancer Institute and Hospital, Tianjin (China); Breast Surgery, Tianjin Medical University Cancer Institute and Hospital, Tianjin (China); Li, Yue [Department of Respiration, Affiliated Hospital of Medical College of Chinese People’s Armed Police Force, Tianjin (China); Chen, Ao-Xiang; Sun, Xuan [Key Laboratory of Breast Cancer Prevention and Treatment of the Ministry of Education, Tianjin Medical University Cancer Institute and Hospital, Tianjin (China); Breast Surgery, Tianjin Medical University Cancer Institute and Hospital, Tianjin (China); Ge, Jie, E-mail: gejie198003@163.com [Key Laboratory of Breast Cancer Prevention and Treatment of the Ministry of Education, Tianjin Medical University Cancer Institute and Hospital, Tianjin (China); Breast Surgery, Tianjin Medical University Cancer Institute and Hospital, Tianjin (China)

    2014-04-04

    Highlights: • FOXD3 is down-regulated in breast cancer tissues. • FOXD3 inhibits breast cancer cell proliferation and invasion. • FoxD3 deficiency induces epithelial–mesenchymal transition. - Abstract: The transcription factor forkhead box D3 (FOXD3) plays an important role in the development of neural crest and gastric cancer cells. However, the function and mechanisms of FOXD3 in the breast tumorigenesis and progression is still limited. Here, we report that FOXD3 is a tumor suppressor of breast cancer tumorigenicity and aggressiveness. We found that FOXD3 is down-regulated in breast cancer tissues. Patients with low FOXD3 expression have a poor outcome. Depletion of FOXD3 expression promotes breast cancer cell proliferation and invasion in vitro, whereas overexpression of FOXD3 inhibits breast cancer cell proliferation and invasion both in vitro and in vivo. In addition, depletion of FOXD3 is linked to epithelial–mesenchymal transition (EMT)-like phenotype. Our results indicate FOXD3 exhibits tumor suppressive activity and may be useful for breast therapy.

  14. FoxD3 deficiency promotes breast cancer progression by induction of epithelial–mesenchymal transition

    International Nuclear Information System (INIS)

    Chu, Tian-Li; Zhao, Hong-Meng; Li, Yue; Chen, Ao-Xiang; Sun, Xuan; Ge, Jie

    2014-01-01

    Highlights: • FOXD3 is down-regulated in breast cancer tissues. • FOXD3 inhibits breast cancer cell proliferation and invasion. • FoxD3 deficiency induces epithelial–mesenchymal transition. - Abstract: The transcription factor forkhead box D3 (FOXD3) plays an important role in the development of neural crest and gastric cancer cells. However, the function and mechanisms of FOXD3 in the breast tumorigenesis and progression is still limited. Here, we report that FOXD3 is a tumor suppressor of breast cancer tumorigenicity and aggressiveness. We found that FOXD3 is down-regulated in breast cancer tissues. Patients with low FOXD3 expression have a poor outcome. Depletion of FOXD3 expression promotes breast cancer cell proliferation and invasion in vitro, whereas overexpression of FOXD3 inhibits breast cancer cell proliferation and invasion both in vitro and in vivo. In addition, depletion of FOXD3 is linked to epithelial–mesenchymal transition (EMT)-like phenotype. Our results indicate FOXD3 exhibits tumor suppressive activity and may be useful for breast therapy

  15. Direct Vapor Growth of Perovskite CsPbBr3 Nanoplate Electroluminescence Devices.

    Science.gov (United States)

    Hu, Xuelu; Zhou, Hong; Jiang, Zhenyu; Wang, Xiao; Yuan, Shuangping; Lan, Jianyue; Fu, Yongping; Zhang, Xuehong; Zheng, Weihao; Wang, Xiaoxia; Zhu, Xiaoli; Liao, Lei; Xu, Gengzhao; Jin, Song; Pan, Anlian

    2017-10-24

    Metal halide perovskite nanostructures hold great promises as nanoscale light sources for integrated photonics due to their excellent optoelectronic properties. However, it remains a great challenge to fabricate halide perovskite nanodevices using traditional lithographic methods because the halide perovskites can be dissolved in polar solvents that are required in the traditional device fabrication process. Herein, we report single CsPbBr 3 nanoplate electroluminescence (EL) devices fabricated by directly growing CsPbBr 3 nanoplates on prepatterned indium tin oxide (ITO) electrodes via a vapor-phase deposition. Bright EL occurs in the region near the negatively biased contact, with a turn-on voltage of ∼3 V, a narrow full width at half-maximum of 22 nm, and an external quantum efficiency of ∼0.2%. Moreover, through scanning photocurrent microscopy and surface electrostatic potential measurements, we found that the formation of ITO/p-type CsPbBr 3 Schottky barriers with highly efficient carrier injection is essential in realizing the EL. The formation of the ITO/p-type CsPbBr 3 Schottky diode is also confirmed by the corresponding transistor characteristics. The achievement of EL nanodevices enabled by directly grown perovskite nanostructures could find applications in on-chip integrated photonics circuits and systems.

  16. Impaired intrinsic immunity to HSV-1 in human iPSC-derived TLR3-deficient CNS cells

    Science.gov (United States)

    Lafaille, Fabien G; Pessach, Itai M.; Zhang, Shen-Ying; Ciancanelli, Michael J.; Herman, Melina; Abhyankar, Avinash; Ying, Shui-Wang; Keros, Sotirios; Goldstein, Peter A.; Mostoslavsky, Gustavo; Ordovas-Montanes, Jose; Jouanguy, Emmanuelle; Plancoulaine, Sabine; Tu, Edmund; Elkabetz, Yechiel; Al-Muhsen, Saleh; Tardieu, Marc; Schlaeger, Thorsten M.; Daley, George Q.; Abel, Laurent; Casanova, Jean-Laurent; Studer, Lorenz; Notarangelo, Luigi D.

    2012-01-01

    In the course of primary infection with herpes simplex virus 1 (HSV-1), children with inborn errors of TLR3 immunity are prone to HSV-1 encephalitis (HSE) 13. We tested the hypothesis that the pathogenesis of HSE involves non hematopoietic central nervous system (CNS)-resident cells. We derived induced pluripotent stem cells (iPSCs) from the dermal fibroblasts of TLR3- and UNC-93B-deficient patients and from controls. These iPSCs were differentiated into highly purified populations of neural stem cells (NSCs), neurons, astrocytes and oligodendrocytes. The induction of IFN-β and/or IFN-γ1 in response to poly(I:C) stimulation was dependent on TLR3 and UNC-93B in all cells tested. However, the induction of IFN-β and IFN-γ1 in response to HSV-1 infection was impaired selectively in UNC-93B-deficient neurons and oligodendrocytes. These cells were also much more susceptible to HSV-1 infection than control cells, whereas UNC-93B-deficient NSCs and astrocytes were not. TLR3-deficient neurons were also found to be susceptible to HSV-1 infection. The rescue of UNC-93B- and TLR3-deficient cells with the corresponding wild-type allele demonstrated that the genetic defect was the cause of the poly(I:C) and HSV-1 phenotypes. The viral infection phenotype was further rescued by treatment with exogenous IFN-α/β, but not IFN-γ1.Thus, impaired TLR3- and UNC-93B-dependent IFN-α/β intrinsic immunity to HSV-1 in the CNS, in neurons and oligodendrocytes in particular, may underlie the pathogenesis of HSE in children with TLR3 pathway deficiencies. PMID:23103873

  17. Optical constants of CH3NH3PbBr3 perovskite thin films measured by spectroscopic ellipsometry

    KAUST Repository

    Alias, Mohd Sharizal

    2016-07-14

    The lack of optical constants information for hybrid perovskite of CH3NH3PbBr3 in thin films form can delay the progress of efficient LED or laser demonstration. Here, we report on the optical constants (complex refractive index and dielectric function) of CH3NH3PbBr3 perovskite thin films using spectroscopic ellipsometry. Due to the existence of voids, the refractive index of the thin films is around 8% less than the single crystals counterpart. The energy bandgap is around 2.309 eV as obtained from photoluminescence and spectrophotometry spectra, and calculated from the SE analysis. The precise measurement of optical constants will be useful in designing optical devices using CH3NH3PbBr3 thin films.

  18. Vitamin D deficiency among healthy adolescents in Al Ain, United Arab Emirates

    Science.gov (United States)

    2013-01-01

    Background Although vitamin D deficiency has been studied in various adult populations, there are few data on the prevalence of this nutritional deficiency among healthy adolescents in the United Arab Emirates (UAE). This study was conducted to determine the prevalence of vitamin D deficiency and to examine its correlates in adolescents aged 15 to 18 years. Methods This was a cross-sectional study in urban schools. Healthy adolescents (N=315) from a sample of 8 schools were randomly selected from the 142 schools in Al Ain, Abu Dhabi Emirate. Outcomes measured included serum concentrations of 25-hydroxy vitamin D (25OHD), plasma lipids, blood sugar, blood pressure and anthropometric data, nutrition and lifestyle variables. Results Fourty-one participants (19.7%) were vitamin D deficient (serum 25OHD level ≤15 ng/mL [≤37.5 nmol/L]. Using a cutoff level of 25(OH) D of ≤20 ng/ml [≤50 nmol/l] 143 participants (45.4%) were vitamin D insufficient. Overall 65.1% of study participants were either vitamin D deficient or insufficient. The prevalence of vitamin D deficiency varied between boys (10%) and girls (28%). In a final multivariate model, serum 25(OH) D concentrations were inversely correlated with female gender, consumption of fast food per week, and body mass index and positively correlated with physical activity scores after adjustment for age. Conclusions Vitamin D deficiency and insufficiency were highly prevalent in adolescents, and more common in girls. PMID:23311702

  19. Synthesis of LaNiO3 perovskite type by chelating precursor method using EDTA: optimization of chelating content

    International Nuclear Information System (INIS)

    Santos, Jose Carlos dos; Pedrosa, Anne Michelle Garrido; Mesquita, Maria Eliane; Souza, Marcelo Jose Barros de

    2011-01-01

    The perovskites are strategic materials due their catalytic, electronic and magnetic properties. These properties are influenced by the calcination and synthesis conditions. In this work was carried out the synthesis of LaNiO 3 perovskite type by chelating precursor method using EDTA and also was studied the optimization of the EDTA content in the synthesis. The synthesized materials were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TG) and Infrared Spectroscopy (FTIR). In the optimization of the EDTA content the lowest ratio of metal / EDTA used was 1.0 / 0.1, where it was possible to obtain monophasic perovskite. (author)

  20. Current state and perspectives for organo-halide perovskite solar cells. Part 1. Crystal structures and thin film formation, morphology, processing, degradation, stability improvement by carbon nanotubes. A review

    Directory of Open Access Journals (Sweden)

    Nigmat Ashurov

    2017-03-01

    Full Text Available The fundamental problems of the modern state of the studies of organic–inorganic organo-halide perovskites (OHP as basis for high efficiency thin film solar cells are discussed. Perovskite varieties and background properties are introduced. The chronology of development of the studies in this direction has been presented – structural aspects of these OHP perovskites, from early 2D to recent 3D MAPbI3 perovskites and important technological aspects of smooth thin film structure creation by various techniques, such as solvent engineering, spin- and dip - coating, vacuum deposition, cation exchange approach, nanoimprinting (particularly, a many-sided role of polymers. The most important theoretical problems such as electronic structure of lattice, impurity and defect states in pure and mixed perovskites, suppressed electron-hole recombination, extra-long lifetimes, and diffusion lengths are analyzed. Degradation effects associated with moisture and photo irradiation, as well as degradation of metallic electrodes to OHP solar cells have been considered. The application of carbon nanostructures: carbon nanotubes (CNT and graphene as stable semitransparent charge collectors to OHP perovskites is demonstrated on the example of original results of authors.

  1. Carbon nanotube charge collectors for nanoimprinted hybrid perovskite photovoltaics (Conference Presentation)

    Science.gov (United States)

    Zakhidov, Anvar A.; Haroldson, Ross; Saranin, Danila; Martinez, Patricia; Ishteev, Artur

    2017-06-01

    The hybrid (organo-inorganic) lead-halide perovskites revolutionized the field of solar cell research due to the impressive power conversion efficiencies of up to 21% recently reported in perovskite based solar cells. This talk will present first the general concepts of excitonic photovoltaics, as compared to conventional Si-type solar cells, asking a question: is hybrid perovskite PV an excitonic solar cell or not? Do we need excitons dissociation at D-A interfaces or CNT charge collectors? Then I will show our recent experimental results on the fast spectroscopy of excitons, magnetic field effect on generation of correlated (e-h) pairs. Also will discuss our Hall effect results, that allows to evaluate intrinsic charge carrier transport and direct measurements of mobility in these materials performed for the first time in steady-state dc transport regime. From these measurements, we have obtained the electron-hole recombination coefficient, the carrier diffusion length and lifetime. Our main results include the intrinsic Hall carrier mobility reaching up to 60 cm2V-1s-1 in perovskite single crystals, carrier lifetimes of up to 3 ms (surprisingly too long!), and carrier diffusion lengths as long as 650 μm (huge if compared to organic and even best inorganic materials). Our results also demonstrate that photocarrier recombination in these disordered solution-processed perovskites is as weak as in the best (high-purity single crystals) of conventional direct-band inorganic semiconductors. Moreover, as we show in our experiment, carrier trapping in perovskites is also strongly suppressed, which accounts for such long carrier lifetimes and diffusion lengths, significantly longer than similar parameters in the best inorganic semiconductors, such e.g. as GaAs. All these remarkable transport properties of hybrid perovskites need to be understood from fundamental physics point of view. Looks like we need some new concepts to explain the mysterious properties of

  2. High Br- Content CsPb(Cl yBr1- y)3 Perovskite Nanocrystals with Strong Mn2+ Emission through Diverse Cation/Anion Exchange Engineering.

    Science.gov (United States)

    Li, Fei; Xia, Zhiguo; Pan, Caofeng; Gong, Yue; Gu, Lin; Liu, Quanlin; Zhang, Jin Z

    2018-04-11

    The unification of tunable band edge (BE) emission and strong Mn 2+ doping luminescence in all-inorganic cesium lead halide perovskite nanocrystals (NCs) CsPbX 3 (X = Cl and Br) is of fundamental importance in fine tuning their optical properties. Herein, we demonstrate that benefiting from the differentiation of the cation/anion exchange rate, ZnBr 2 and preformed CsPb 1- x Cl 3 : xMn 2+ NCs can be used to obtain high Br - content Cs(Pb 1- x- z Zn z )(Cl y Br 1- y ) 3 : xMn 2+ perovskite NCs with strong Mn 2+ emission, and the Mn 2+ substitution ratio can reach about 22%. More specifically, the fast anion exchange could be realized by the soluble halide precursors, leading to anion exchange within a few seconds as observed from the strong BE emission evolution, whereas the cation exchange instead generally required at least a few hours; moreover, their exchange mechanism and dynamics process have been evaluated. The Mn 2+ emission intensity could be further varied by controlling the replacement of Mn 2+ by Zn 2+ with prolonged ion exchange reaction time. White light emission of the doped perovskite NCs via this cation/anion synergistic exchange strategy has been realized, which was also successfully demonstrated in a prototype white light-emitting diode (LED) device based on a commercially available 365 nm LED chip.

  3. Structural, magnetic and transport properties of Mn3.1Sn0.9 and Mn3.1Sn0.9N compounds

    International Nuclear Information System (INIS)

    Feng, W.J.; Li, D.; Ren, W.J.; Li, Y.B.; Li, W.F.; Li, J.; Zhang, Y.Q.; Zhang, Z.D.

    2007-01-01

    The cubic anti-perovskite Mn 3.1 Sn 0.9 N compound is prepared via nitrogenation of the hexagonal Mn 3.1 Sn 0.9 compound. A magnetic phase diagram of Mn 3.1 Sn 0.9 compound is constructed by analysis of data of its magnetic properties. For Mn 3.1 Sn 0.9 N compound, parasitic ferromagnetism exists in the temperature range of 5-370 K, besides a spin-reorientation at about 280 K. Mn 3.1 Sn 0.9 compound exhibits a metallic conducting behavior, while Mn 3.1 Sn 0.9 N displays a metal-nonmetal transition due to the electron localization caused by the static disorder. The differences of the physical properties between the both compounds, are discussed, in terms of the correlation of the hexagonal DO 19 and the cubic anti-perovskite structures, the reduction of the distances between Mn atoms, and the spin-pairing or charge transfer effect due to the electron donation by N 2p to Mn 3d states after introduction of N atoms into the interstitial sites of Mn 3.1 Sn 0.9 compound

  4. CH3NH3PbI3 grain growth and interfacial properties in meso-structured perovskite solar cells fabricated by two-step deposition

    Science.gov (United States)

    Yao, Zhibo; Wang, Wenli; Shen, Heping; Zhang, Ye; Luo, Qiang; Yin, Xuewen; Dai, Xuezeng; Li, Jianbao; Lin, Hong

    2017-12-01

    Although the two-step deposition (TSD) method is widely adopted for the high performance perovskite solar cells (PSCs), the CH3NH3PbI3 perovskite crystal growth mechanism during the TSD process and the photo-generated charge recombination dynamics in the mesoporous-TiO2 (mp-TiO2)/CH3NH3PbI3/hole transporting material (HTM) system remains unexploited. Herein, we modified the concentration of PbI2 (C(PbI2)) solution to control the perovskite crystal properties, and observed an abnormal CH3NH3PbI3 grain growth phenomenon atop mesoporous TiO2 film. To illustrate this abnormal grain growth mechanism, we propose that a grain ripening process is taking place during the transformation from PbI2 to CH3NH3PbI3, and discuss the PbI2 nuclei morphology, perovskite grain growing stage, as well as Pb:I atomic ratio difference among CH3NH3PbI3 grains with different morphology. These C(PbI2)-dependent perovskite morphologies resulted in varied charge carrier transfer properties throughout the mp-TiO2/CH3NH3PbI3/HTM hybrid, as illustrated by photoluminescence measurement. Furthermore, the effect of CH3NH3PbI3 morphology on light absorption and interfacial properties is investigated and correlated with the photovoltaic performance of PSCs.

  5. Copper-Substituted Lead Perovskite Materials Constructed with Different Halides for Working (CH3NH3)2CuX4-Based Perovskite Solar Cells from Experimental and Theoretical View.

    Science.gov (United States)

    Elseman, Ahmed Mourtada; Shalan, Ahmed Esmail; Sajid, Sajid; Rashad, Mohamed Mohamed; Hassan, Ali Mostafa; Li, Meicheng

    2018-04-11

    Toxicity and chemical instability issues of halide perovskites based on organic-inorganic lead-containing materials still remain as the main drawbacks for perovskite solar cells (PSCs). Herein, we discuss the preparation of copper (Cu)-based hybrid materials, where we replace lead (Pb) with nontoxic Cu metal for lead-free PSCs, and investigate their potential toward solar cell applications based on experimental and theoretical studies. The formation of (CH 3 NH 3 ) 2 CuX 4 [(CH 3 NH 3 ) 2 CuCl 4 , (CH 3 NH 3 ) 2 CuCl 2 I 2 , and (CH 3 NH 3 ) 2 CuCl 2 Br 2 ] was discussed in details. Furthermore, it was found that chlorine (Cl - ) in the structure is critical for the stabilization of the formed compounds. Cu-based perovskite-like materials showed attractive absorbance features extended to the near-infrared range, with appropriate band gaps. Green photoluminescence of these materials was obtained because of Cu + ions. The power conversion efficiency was measured experimentally and estimated theoretically for different architectures of solar cell devices.

  6. Thermoelectric Properties of the Perovskite-Type Oxide SrTi1-xNbxO3 Synthesized by Solid-State Reaction Method

    Science.gov (United States)

    Khan, Tamal Tahsin; Ur, Soon-Chul

    2018-05-01

    The perovskite-type oxide materials SrTi1-xNbxO3 (X = .02, 0.03, 0.04, 0.05 and 0.06) were synthesized by the conventional solid-state reaction method and the thermoelectric properties in terms of Nb doping at the B-site in the oxides were investigated in this study. The formation of single phase cubic perovskite structure was confirmed by the powder X-ray diffraction analysis. Negative conduction is shown in this materials system. The absolute value of Seebeck coefficient increased with increasing temperature over the measured temperature. The electrical conductivity decreased monotonically with increasing temperature, showing degenerating conduction behavior. The thermal conductivity, k, generally decreased with increasing temperature. The power factor increased with increasing Nb-doping level up to 5.0 mol% and hence the dimensionless figure of merit ZT, increased up to 5.0 mol%. The maximum ZT value was observed for SrTi0.95Nb0.05O3 at 873 K.

  7. Charge carrier dynamics of methylammonium lead iodide: from PbI₂-rich to low-dimensional broadly emitting perovskites.

    Science.gov (United States)

    Klein, Johannes R; Flender, Oliver; Scholz, Mirko; Oum, Kawon; Lenzer, Thomas

    2016-04-28

    We provide an investigation of the charge carrier dynamics of the (MAI)(x)(PbI2)(1-x) system in the range x = 0.32-0.90 following the recently published "pseudobinary phase-composition processing diagram" of Song et al. (Chem. Mater., 2015, 27, 4612). The dynamics were studied using ultrafast pump-supercontinuum probe spectroscopy over the pump fluence range 2-50 μJ cm(-2), allowing for a wide variation of the initial carrier density. At high MAI excess (x = 0.90), low-dimensional perovskites (LDPs) are formed, and their luminescence spectra are significantly blue-shifted by ca. 50 nm and broadened compared to the 3D perovskite. The shift is due to quantum confinement effects, and the inhomogeneous broadening arises from different low-dimensional structures (predominantly 2D, but presumably also 1D and 0D). Accurate transient carrier temperatures are extracted from the transient absorption spectra. The regimes of carrier-carrier, carrier-optical phonon and acoustic phonon scattering are clearly distinguished. Perovskites with mole fractions x ≤ 0.71 exhibit extremely fast carrier cooling (ca. 300 fs) at low fluence of 2 μJ cm(-2), however cooling slows down significantly at high fluence of 50 μJ cm(-2) due to the "hot phonon effect" (ca. 2.8 ps). A kinetic analysis of the electron-hole recombination dynamics provides second-order recombination rate constants k2 which decrease from 5.3 to 1.5 × 10(-9) cm(3) s(-1) in the range x = 0.32-0.71. In contrast, recombination in the LDPs (x = 0.90) is more than one order of magnitude faster, 6.4 × 10(-8) cm(3) s(-1), which is related to the confined perovskite structure. Recombination in these LDPs should be however still slow enough for their potential application as efficient broadband emitters or solar light-harvesting materials.

  8. A Direct Bandgap Copper-Antimony Halide Perovskite.

    Science.gov (United States)

    Vargas, Brenda; Ramos, Estrella; Pérez-Gutiérrez, Enrique; Alonso, Juan Carlos; Solis-Ibarra, Diego

    2017-07-12

    Since the establishment of perovskite solar cells (PSCs), there has been an intense search for alternative materials to replace lead and improve their stability toward moisture and light. As single-metal perovskite structures have yielded unsatisfactory performances, an alternative is the use of double perovskites that incorporate a combination of metals. To this day, only a handful of these compounds have been synthesized, but most of them have indirect bandgaps and/or do not have bandgaps energies well-suited for photovoltaic applications. Here we report the synthesis and characterization of a unique mixed metal ⟨111⟩-oriented layered perovskite, Cs 4 CuSb 2 Cl 12 (1), that incorporates Cu 2+ and Sb 3+ into layers that are three octahedra thick (n = 3). In addition to being made of abundant and nontoxic elements, we show that this material behaves as a semiconductor with a direct bandgap of 1.0 eV and its conductivity is 1 order of magnitude greater than that of MAPbI 3 (MA = methylammonium). Furthermore, 1 has high photo- and thermal-stability and is tolerant to humidity. We conclude that 1 is a promising material for photovoltaic applications and represents a new type of layered perovskite structure that incorporates metals in 2+ and 3+ oxidation states, thus significantly widening the possible combinations of metals to replace lead in PSCs.

  9. Homogeneous Emission Line Broadening in the Organo Lead Halide Perovskite CH3NH3PbI3-xClx.

    Science.gov (United States)

    Wehrenfennig, Christian; Liu, Mingzhen; Snaith, Henry J; Johnston, Michael B; Herz, Laura M

    2014-04-17

    The organic-inorganic hybrid perovskites methylammonium lead iodide (CH3NH3PbI3) and the partially chlorine-substituted mixed halide CH3NH3PbI3-xClx emit strong and broad photoluminescence (PL) around their band gap energy of ∼1.6 eV. However, the nature of the radiative decay channels behind the observed emission and, in particular, the spectral broadening mechanisms are still unclear. Here we investigate these processes for high-quality vapor-deposited films of CH3NH3PbI3-xClx using time- and excitation-energy dependent photoluminescence spectroscopy. We show that the PL spectrum is homogenously broadened with a line width of 103 meV most likely as a consequence of phonon coupling effects. Further analysis reveals that defects or trap states play a minor role in radiative decay channels. In terms of possible lasing applications, the emission spectrum of the perovskite is sufficiently broad to have potential for amplification of light pulses below 100 fs pulse duration.

  10. CsPbBr3:xEu3+ perovskite QD borosilicate glass: a new member of the luminescent material family.

    Science.gov (United States)

    Yuan, Rongrong; Shen, Lingli; Shen, Chenyang; Liu, Jianming; Zhou, Lei; Xiang, Weidong; Liang, Xiaojuan

    2018-03-29

    Eu3+ ions were introduced into the lattices of CsPbBr3 perovskite QDs and a tunable multicolour emission from CsPbBr3:xEu3+ perovskite QD glass was successfully obtained. Multicolour LEDs that were fabricated by combining the as-prepared CsPbBr3:xEu3+ QD glasses with a UV chip were also researched in this study.

  11. Symmetry mismatch-driven perpendicular magnetic anisotropy for perovskite/brownmillerite heterostructures.

    Science.gov (United States)

    Zhang, Jing; Zhong, Zhicheng; Guan, Xiangxiang; Shen, Xi; Zhang, Jine; Han, Furong; Zhang, Hui; Zhang, Hongrui; Yan, Xi; Zhang, Qinghua; Gu, Lin; Hu, Fengxia; Yu, Richeng; Shen, Baogen; Sun, Jirong

    2018-05-15

    Grouping different transition metal oxides together by interface engineering is an important route toward emergent phenomenon. While most of the previous works focused on the interface effects in perovskite/perovskite heterostructures, here we reported on a symmetry mismatch-driven spin reorientation toward perpendicular magnetic anisotropy in perovskite/brownmillerite heterostructures, which is scarcely seen in tensile perovskite/perovskite heterostructures. We show that alternately stacking perovskite La 2/3 Sr 1/3 MnO 3 and brownmillerite LaCoO 2.5 causes a strong interface reconstruction due to symmetry discontinuity at interface: neighboring MnO 6 octahedra and CoO 4 tetrahedra at the perovskite/brownmillerite interface cooperatively relax in a manner that is unavailable for perovskite/perovskite interface, leading to distinct orbital reconstructions and thus the perpendicular magnetic anisotropy. Moreover, the perpendicular magnetic anisotropy is robust, with an anisotropy constant two orders of magnitude greater than the in-plane anisotropy of the perovskite/perovskite interface. The present work demonstrates the great potential of symmetry engineering in designing artificial materials on demand.

  12. Structural and thermodynamic characterization of the perovskite-related BA{sub 1+y}UO{sub 3+x} and (BA,SR){sub 1+y}UO{sub 3+x} phases

    Energy Technology Data Exchange (ETDEWEB)

    Cordfunke, E.H.P. [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); Booij, A.S. [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); Smit-Groen, V. [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); Vlaanderen, P. van [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); IJdo, D.J.W. [Rijksuniversiteit Leiden (Netherlands). Gorlaeus Labs.

    1996-11-01

    The perovskite-type BaUO{sub 3} structure has been investigated by X-ray and neutron diffraction. The Ba/U ratio, the (Ba, Sr)/U ratio, and the oxygen stoichiometry in Ba{sub 1+y}UO{sub 3+x} were varied, and the integral enthalpies of formation determined by solution calorimetry. In addition, equilibrium oxygen partial pressures were measured using a reversible EMF cell. The chemical defect mechanism is discussed, and it is shown that a continuous series BaUO{sub 3}-Ba{sub 1+y}UO{sub 3+x}-Ba{sub 3}UO{sub 6} exist in which uranium vacancies are gradually filled up with barium ions, whereas uranium is oxidized via the pentavalent to the hexavalent state in Ba{sub 3}UO{sub 6}(=Ba{sub 2}(Ba, U)O{sub 6}). (orig.).

  13. An update on the association of vitamin D deficiency with common infectious diseases.

    Science.gov (United States)

    Watkins, Richard R; Lemonovich, Tracy L; Salata, Robert A

    2015-05-01

    Vitamin D plays an important role in modulating the immune response to infections. Deficiency of vitamin D is a common condition, affecting both the general population and patients in health care facilities. Over the last decade, an increasing body of evidence has shown an association between vitamin D deficiency and an increased risk for acquiring several infectious diseases, as well as poorer outcomes in vitamin D deficient patients with infections. This review details recent developments in understanding the role of vitamin D in immunity, the antibacterial actions of vitamin D, the association between vitamin D deficiency and common infections (like sepsis, pneumonia, influenza, methicillin-resistant Staphylococcus aureus, human immunodeficiency virus type-1 (HIV), and hepatitis C virus (HCV)), potential therapeutic implications for vitamin D replacement, and future research directions.

  14. Association of vitamin D level and vitamin D deficiency with risk of preeclampsia: A systematic review and updated meta-analysis

    Directory of Open Access Journals (Sweden)

    Soheila Akbari

    2018-04-01

    Full Text Available Objectives: Because of the immune modulatory effects of vitamin D3 in preeclampsia, we intend to have a systematic review and meta-analysis on association of both 25-hydroxy vitamin D (25-OHD level (parametric approach and 25-OHD deficiency (non-parametric approach with preeclampsia. As well, for the parametric part, we used receiver operating characteristic (ROC curve model. Materials and methods: We used Web of Science, PubMed and Science Direct data bases through searching in titles. Google Scholar search engine was use