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PubMed | Taras Shevchenko National University, Institute of Semiconductor Physics of Ukraine, STC Institute for Single Crystals NAS of Ukraine and National Oo Bogomoletz Medical University
Type: Journal Article | Journal: Dalton transactions (Cambridge, England : 2003) | Year: 2016

The influence of molybdenum content in the solid solutions of Bi1-x/3V1-xMoxO4 (x = 0.05-0.20) on the morphology, band gap, structure and light-driven water oxidation properties has been studied by scanning electron microscopy, X-ray powder diffraction and vibrational spectroscopy (Raman and infrared). To find out the peculiarities of structural changes for bismuth scheelite-related oxides containing both vanadium and molybdenum crystals of Bi0.98V0.93Mo0.07O4 have been grown from a K-Bi-V-Mo-O high-temperature melt and characterized by single crystal X-ray diffraction. For the scheelite-related framework both V and Mo were found to occupy the same positions lowering the point group symmetry of tetrahedra from 4/m to 2/m giving monoclinic distortion for solid solutions with x = 0.05-0.10. The most promising photocatalytic performance was obtained for Bi0.96Mo0.10V0.90O4, in which the oxygen evolution could reach 21 M in 50 s under visible light of LEDs, = 470 10 nm, and 820 E cm(-2) s(-1). The changes in catalytic properties are shown to be governed by a crystal structure strain with a maximum obtained for the boundary sample between the monoclinic and tetragonal phase.


Terebilenko K.V.,Taras Shevchenko National University | Slobodyanik N.S.,Taras Shevchenko National University | Ogorodnyk I.V.,Taras Shevchenko National University | Baumer V.N.,STC Institute for Single Crystals NAS of Ukraine | Baumer V.N.,University of Kharkiv
Crystal Research and Technology | Year: 2014

A number of NASICON-related MIGe2(PO 4)3 (MI - Na, K, Ag) have been prepared using a high-temperature solution method in the molten system MI-Ge-P-O (MI - Na, K) based on the solubility data for GeO2 at 1123 K for the Na-P-O system and 1173 K for the K-P-O one. The single crystals of AgGe2(PO4)3 were obtained after crystallization of a melt with Ag/P = 1.4. It crystallizes in the trigonal system, space group R-3, cell parameters a = 8.06340(1) Å, c = 21.8385(4) Å, Z = 6. The framework is built up from two GeO6 units that are isolated from each other by PO4 tetrahedra to form the main building block of the structure [Ge2(PO4)3]-. Two types of silver cations M1 and M2 are found to have different coordination requirements shown by the bond valence sum calculations. MIGe2(PO 4)3 have been prepared using high-temperature solution method in the molten system MI-Ge-P-O. Single crystals of AgGe 2(PO4)3 have been obtained which crystallizes in a trigonal system. The framework is built from two GeO6 which are isolated from each other by PO4 tetrahedra to form the main building block of the structure [Ge2(PO4)3]-. Two types of silver cations are found to have different coordination requirements shown by the Bond Valence Sum calculations. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Pogorelov V.,Taras Shevchenko National University | Kutulya L.,STC Institute for Single Crystals NAS of Ukraine | Shkol'Nikova N.,STC Institute for Single Crystals NAS of Ukraine | Golub P.,Taras Shevchenko National University | And 2 more authors.
Journal of Molecular Structure | Year: 2012

For substances 4-(n-hexyloxy)phenyl-4′-(n-octyloxy)benzoate and 4-(n-octyloxy)phenyl-4′-(n-hexyloxy)benzoate forming liquid-crystalline mesophases the Raman spectra in the region of 1000-3000 cm-1 were measured and assigned. The information on molecular geometry was obtained by quantum-chemical simulation. The calculations were made using the Gaussian-03 package at the HF/3-21G level of theory. Separately we investigated the temperature dependence of Raman spectra for the vibrational bands in the spectral range 1100-1350 and 1550-1750 cm-1 during the cooling process. The cooling rate was 1-2 K/min, and quasi-static condition of appropriate temperature processes was achieved in such a way. Noticeable changes in Raman spectra with temperature changing indicating the phase transitions are reported. © 2012 Elsevier B.V. All rights reserved.


Odynets I.V.,Taras Shevchenko National University | Babaryk A.A.,Taras Shevchenko National University | Baumer V.N.,STC Institute for Single Crystals NAS of Ukraine | Slobodyanik N.S.,Taras Shevchenko National University | Shiskin O.V.,STC Institute for Single Crystals NAS of Ukraine
Zeitschrift fur Anorganische und Allgemeine Chemie | Year: 2011

Potassium-containing zirconium(IV)/titanium(IV) tantalum(V) oxides, K 3TiTa7O21 (1) and K3ZrTa 7O21 (2), of K3Nb8O 21-type of compounds are afforded from potassium-molybdate flux. Both compounds crystallize in the hexagonal space group P63/mcm (no. 193) with a = 908.69(2), c = 1202.83(7) pm and c/a = 1.324 (Z = 2) for 1 and a = 913.30(3), c = 1219.21(6) pm and c/a = 1.335 (Z = 2) for 2, respectively. The Structural motif of [MTa7O21]3- (M = Ti 4+ or Zr4+) consists of edge-shared (M,Ta) 6O24-units that are similar to corner-sharing Ta 6O27 units of synthetic soro-silicate K3Ta 3Si2O13 and double borate K3Ta 3B2O12. The solid state bandgap measurements revealed that calculated values (3.26 eV for K3TiTa7O 21 and 3.14 eV for K3ZrTa7O21) are dependent on aperture of Ta-O-Ta bond angle as it was previously shown for perovskite-type tantalate photocatalysts. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Terebilenko K.V.,Taras Shevchenko National University | Kirichok A.A.,Taras Shevchenko National University | Baumer V.N.,STC Institute for Single Crystals NAS of Ukraine | Sereduk M.,Taras Shevchenko National University | And 2 more authors.
Journal of Solid State Chemistry | Year: 2010

AgFeP2O7 has been synthesized by flux crystallization and characterized by single crystal and powder X-ray diffraction (sp. gr. P21/c, a=7.3298(2), b=7.9702(2), c=9.5653(2) Å, β=111.842(1)°, V=518.68(2) Å3) and FTIR-spectroscopy. The structure is composed of isolated iron octahedra and phosphate tetrahedra interconnected into 3D network with hexagonal channels, where silver counter-ions are located. The magnetic behavior of the compound approaches the Curie-Weiss equation with a Weiss constant θ=-165.9 K indicating strong antiferromagnetic interaction between iron(III) ions. © 2010 Elsevier Inc. All rights reserved.


Slobodyanik N.S.,Taras Shevchenko National University | Terebilenko K.V.,Taras Shevchenko National University | Ogorodnyk I.V.,Taras Shevchenko National University | Zatovsky I.V.,Taras Shevchenko National University | And 3 more authors.
Inorganic Chemistry | Year: 2012

The possibility of PO 4 3- for MoO 4 2- partial substitution in the langbeinite framework has been studied by exploration of the K-Fe(Sc)-Mo(W)-P-O systems using the high-temperature solution method. It was shown that 1/3PO 4 3- for MoO 4 2- substitution leads to formation of three novel compounds K 2Fe(MoO 4)(PO 4) 2, K 2Sc(MoO 4)(PO 4) 2, and K 2Sc(WO 4)(PO 4) 2 with slightly increased lattice parameters and significant distortion of the anion tetrahedra without structure changes. In contrast, the antiferromagnetic structure is modified by substitution in the low-temperature region. The structural peculiarities are discussed in light of bond-valence sums calculations. © 2012 American Chemical Society.


Malyukin Y.V.,Institute for Scintillation Materials of Ukraine | Sorokin A.V.,Institute for Scintillation Materials of Ukraine | Semynozhenko V.P.,STC Institute for Single Crystals NAS of Ukraine
Low Temperature Physics | Year: 2016

We present thoroughly analyzed experimental results that demonstrate the anomalous manifestation of the exciton self-trapping effect, which is already well-known in bulk crystals, in ordered molecular nanoclusters called J-aggregates. Weakly-coupled one-dimensional (1D) molecular chains are the main structural feature of J-aggregates, wherein the electron excitations are manifested as 1D Frenkel excitons. According to the continuum theory of Rashba-Toyozawa, J-aggregates can have only self-trapped excitons, because 1D excitons must adhere to barrier-free self-trapping at any exciton-phonon coupling constant g = εLR/2β, wherein εLR is the lattice relaxation energy, and 2β is the half-width of the exciton band. In contrast, very often only the luminescence of free, mobile excitons would manifest in experiments involving J-aggregates. Using the Urbach rule in order to analyze the low-frequency region of the low-temperature exciton absorption spectra has shown that J-aggregates can have both a weak (g < 1) and a strong (g > 1) exciton-phonon coupling. Moreover, it is experimentally demonstrated that under certain conditions, the J-aggregate excited state can have both free and self-trapped excitons, i.e., we establish the existence of a self-trapping barrier for 1D Frenkel excitons. We demonstrate and analyze the reasons behind the anomalous existence of both free and self-trapped excitons in J-aggregates, and demonstrate how exciton-self trapping efficiency can be managed in J-aggregates by varying the values of g, which is fundamentally impossible in bulk crystals. We discuss how the exciton-self trapping phenomenon can be used as an alternate interpretation of the wide band emission of some J-aggregates, which has thus far been explained by the strongly localized exciton model.


Zubatyuk R.I.,STC Institute for Single Crystals NAS of Ukraine | Shishkin O.V.,STC Institute for Single Crystals NAS of Ukraine | Ihmels H.,University of Siegen | Lebedyeva I.A.,Kharkiv Polytechnic Institute | Povstyanoy M.V.,Kharkiv Polytechnic Institute
Acta Crystallographica Section E: Structure Reports Online | Year: 2010

In the title compound, C18H19N3O 3, the tetrahydro-pyrimidone ring adopts a distorted boat conformation. In the crystal structure, inter-molecular N-H⋯O hydrogen bonds link the molecules into centrosymmetric dimers, which are further linked via inter-molecular C-H⋯π inter-actions. In addition, an intra-molecular C-H⋯O hydrogen bond occurs.


Svechkarev D.,University of Kharkiv | Doroshenko A.,University of Kharkiv | Baumer V.,STC Institute for Single Crystals NAS of Ukraine | Dereka B.,University of Kharkiv
Journal of Luminescence | Year: 2011

Synthesis of the quinoline-substituted 3-hydroxychromone is reported, spectral and fluorescent properties of the title compound are investigated in different solvents. The question of the possibility of the participation of the substituent heterocycle's nitrogen atom in H-bond formation as well as in the ESIPT process is discussed. Quantum-chemical modeling provides evidence that the structure with an alternative H-bond to nitrogen is more energetically favorable and strongly prevails in solutions. However, our calculations together with the experimental data reveal that the excited species with the intramolecular N..HO hydrogen bond type undergoes rapid radiationless deactivation. This leads to a conclusion that the low-intensity dual-band fluorescence of the title compound in solutions originates from the traces of the conformation with the traditional "flavonol-like" H-bond to the carbonyl oxygen atom. A possibility to reversibly tune the direction of the intramolecular H-bond formation and thus regulate the ESIPT process pathway is demonstrated by the example of protonation/deprotonation of the title compound in a methylene chloride solution. © 2010 Elsevier B.V. All rights reserved.


Ogorodnikov I.N.,Ural Federal University | Pustovarov V.A.,Ural Federal University | Puzikov V.M.,STC Institute for Single Crystals NAS of Ukraine | Salo V.I.,STC Institute for Single Crystals NAS of Ukraine | Voronov A.P.,STC Institute for Single Crystals NAS of Ukraine
Optical Materials | Year: 2012

We report experimental study on luminescence and optical properties of single crystals KH 2PO 4 (KDP) doped with Tl + ions (KDP:Tl) carried out at 10-480 K. The 4.5 eV photoluminescence (PL) of KDP:Tl originates from radiative electronic transitions 3P 1 → 1S 0 in the Tl + ions upon excitation by UV-photons, X-rays, and electron beam. This luminescence can be induced by direct photoexcitation, or through the recombination process with participation of the lattice defects located in the vicinity of Tl + ion. These excitation mechanisms lead to different temperature behavior of the luminescence intensity. The PL excitation spectra of KDP crystals containing a small amount of the Tl + ions (0.001-0.008 wt.%) comprises peaks at 5.7-5.8, 6.9, and 7.3-7.4 eV, corresponding subsequently to the A-, B- and C-optical transitions in Tl +. The PL time response has single-exponential behavior with an average lifetime of τ = 280 ± 8 ns. Under exposure to ionizing radiation (X-rays, or electron beam) the intensity of the Tl + luminescence increases depending on the exposure time. The origin of this phenomenon was associated with creation of defects in the hydrogen sublattice of KDP. © 2012 Elsevier B.V. All rights reserved.

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