Characterization of Zr6Nb2O17 synthesized by a peroxo route as a novel solid acid

Cataloged from PDF version of article.The impregnation of hydrated zirconia at pH 0.5 with a solution of peroxoniobium(V) complex, [Nb2(O2)3] 4+, ensuring a ZrO2:Nb2O5 mole ratio of 6:1 followed by calcination at 873 K resulted in the formation of a Zr6Nb2O17 solid solution. The structure of this compound was confirmed by XRD. The surface acidity was investigated by in situ FT-IR spectroscopy using 2,6-dimethylpyridine (lutidine). Zr6Nb2O17 has a sufficient amount of Brønsted acid sites necessary for the stabilization of dispersed Pd(II) species. The potential of the Pd-promoted Zr6Nb2O17 as a catalyst for the reduction of NO with methane was evaluated by studying the reactivity of adsorbed NOx species toward the hydrocarbon. 2007 Elsevier B.V. All rights reserved

Silver nitrate/oligo(ethylene oxide) surfactant/mesoporous silica nanocomposite films and monoliths

A lyotropic, liquid crystalline (LC) phase of a silver nitrate/oligo(ethylene oxide), water, and acid mixture was used for one-pot synthesis of mesoporous silica materials in which Ag+ ions are uniformly distributed. We established that the AgNO3-to-surfactant mole ratio is very important in a 50 wt% surfactant/water system to preserve the hexagonal LC phase before and after the addition of the silica source. Below a 0.6 AgNO3-to-surfactant mole ratio, the mixture is liquid crystalline and serves as a template for silica polymerization. However, between 0.6 and 0.8 AgNO3-to-surfactant mole ratios, one must control the composition of the mixture during the polymerization processes. Above a 0.8 mole ratio, Ag+ ions undergo phase separation from the reaction mixture by complexing with the surfactant molecules. The resulting silica materials obtained from AgNO3/surfactant ratio above 0.8 have anisotropy but without a hexagonal mesophase. Here, we establish a AgNO3 concentration range in which the LC phase is preserved to template the synthesis of mesoporous silica, and we discuss the structural behavior of the mixtures at AgNO3/surfactant mole ratios of 0.00-2.00, using POM, PXRD, FTIR, and UV-Vis absorption spectroscopy. © 2001 Academic Press

Characterization of LaMnAl11O19 by FT-IR spectroscopy of adsorbed NO and NO/O-2

Cataloged from PDF version of article.The nature of the NOx species produced during the adsorption of NO at room temperature and during its coadsorption with oxygen on LaMnAl11O19 sample with magnetoplumbite structure obtained by a sol–gel process has been investigated by means of in situ FT-IR spectroscopy. The adsorption of NO leads to formation of anionic nitrosyls and/or cis-hyponitrite ions and reveals the presence of coordinatively unsaturated Mn3+ ions. Upon NO/O2 adsorption at room temperature various nitro–nitrato structures are observed. The nitro–nitrato species produced with the participation of electrophilic oxygen species decompose at 350 8C directly to N2 and O2. No NO decomposition is observed in absence of molecular oxygen. The adsorbed nitro–nitrato species are inert towards the interaction with methane and block the active sites (Mn3+ ions) for its oxidation. Noticeable oxidation of the methane on the NOx -precovered sample is observed at temperatures higher than 350 8C due to the liberation of the active sites as a result of decomposition of the surface nitro–nitrato species. Mechanism explaining the promoting effect of the molecular oxygen in the NO decomposition is proposed. (c)2005 Elsevier B.V. All rights reserved

Spectroscopic investigation of nitrate-metal and metal-surfactant interactions in the solid AgNO3/C12EO10 and liquid-crystalline [M(H2O)n](NO3)2/C12EO 10 systems

Interactions of the nitrate ions in various metal nitrate salts with CnH2n-1(CH2CH2O)mOH (CnEOm)-type nonionic surfactants have been investigated both in the solid and in the liquid-crystalline (LC) systems. In the ternary system, the mixture of salt/water/CnEOm has a mesophase up to a certain concentration of salt, and the nitrate ions in this phase are usually in a free-ion form. However, upon the evaporation of the water phase, the nitrate ion interacts with the metal center and coordinates as either a bidentate or unidentate ligand. It is this interaction that makes the AgNO3 ternary system undergo a phase separation by releasing solid Ag(CnEOm)xNO3 complex crystals. In contrast, the salt/surfactant systems maintain their stable LC phases for months. Note also that the salt/surfactant systems consist of transition-metal aqua complexes in which the coordinated water molecules play a significant role in the self-assembly and organization of the nonionic surfactant molecules into an LC mesophase. Throughout this work, Fourier transform infrared spectroscopy has been extensively used to investigate the interactions of the nitrate ions with a metal center and the metal ions with the surfactant molecules. Polarized optical microscopy and X-ray diffraction techniques have been applied to investigate the nature of the crystalline and LC phases

In situ FT-IR investigation of the reduction of NO with CO over Au/CeO2-Al2O3 catalyst in the presence and absence of H-2

Cataloged from PDF version of article.he NO + CO + H-2 reaction over CeO2, Au/CeO2 (3 wt% Au), Au/CeO2-Al2O3 (2.9 wt% Au, 20 wt% Al2O3) and CeO2-Al2O3 mixed support prepared by co-precipitation has been Studied by FT-IR spectroscopy at elevated temperatures. Formation of NCO species has been detected on all of the samples. The presence of metallic gold is not necessary for the generation of the isocyanates on ceria and the mixed ceria-alumina support. The NCO species are produced by a process involving the dissociation of NO on the oxygen vacancies of the support, followed by the reaction between N atoms lying oil the surface and CO molecules. Gold plays an important role in the modification of ceria leading to Ce3+ and oxygen vacancies formation, and causes significant lowering of the reduction temperature of CeO2 and CeO2-Al2O3 enhancing the reducibility of ceria surface layers. The role of H-2 is to keep the surface reduced during the course of the reaction. The onset temperature, at which the interaction between the surface isocyanates and No begins, is low (100 degrees C). This explains the high activity of the Au/CeO2-Al2O3 catalyst with 100% selectivity in the reduction of NO by CO at low temperature (200 degrees C) and in the presence of H-2 (C) 2008 Elsevier B.V. All rights reserve

Anisotropic Emission from Multilayered Plasmon Resonator Nanocomposites of Isotropic Semiconductor Quantum Dots

Cataloged from PDF version of article.We propose and demonstrate a nanocomposite localized surface plasmon resonator embedded into an artificial three-dimensional construction. Colloidal semiconductor quantum dots are assembled between layers of metal nanoparticles to create a highly strong plasmon-exciton interaction in the plasmonic cavity. In such a multilayered plasmonic resonator architecture of isotropic CdTe quantum dots, we observed polarized light emission of 80% in the vertical polarization with an enhancement factor of 4.4, resulting in a steady-state anisotropy value of 0.26 and reaching the highest quantum efficiency level of 30% ever reported for such CdTe quantum dot solids. Our electromagnetic simulation results are in good agreement with the experimental characterization data showing a significant emission enhancement in the vertical polarization, for which their fluorescence decay lifetimes are substantially shortened by consecutive replication of our unit cell architecture design. Such strongly plasmon-exciton coupling nanocomposites hold great promise for future exploitation and development of quantum dot plasmonic biophotonics and quantum dot plasmonic optoelectronics

Observation of anisotropic emission from semiconductor quantum dots in nanocomposites of metal nanoparticles

[No abstract available

The synthesis of mesostructured silica films and monoliths functionalised by noble metal nanoparticles

A lyotropic AgNO3, HAuCl4 and H2PtCl6-silica liquid crystalline (LC) phase is used as a supramolecular template for a one-pot synthesis of novel noble metal or complex ion containing nanocomposite materials in the form of a film and monolith. In these structures, Ag+, AuCl4- and PtCl62- ions interact with the head group of an oligo(ethylene oxide) type non-ionic surfactant (C12H25(CH2CH2O)10OH, denoted as C12EO10) assembly that are embedded within the channels of hexagonal mesostructured silica materials. A chemical and/or thermal reduction of the metal or complex ions produces nanoparticles of these metals in the mesoporous channels and the void spaces of the silica. The LC mesophase of H2O:X:HNO3:C12EO10, (where X is AgNO3, HAuCl4 and H2PtCl6), and nanocomposite silica materials of meso-SiO2-C12EO10-X and meso-SiO2-C12EO10-M (M is the Ag, Au and Pt nanoparticles) have been investigated using polarised optical microscopy (POM), powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), Fourier transform (FT) Raman and UV-Vis absorption spectroscopy. Collectively the results indicate that the LC phase of a 50 w/w% H2O:C12EO10 is stable upon mixing with AgNO3, HAuCl4 and H2PtCl6 salts and/or acids. The metal ions or complex ions are distributed inside the channels of the mesoporous silica materials at low concentrations and may be converted into metal nanoparticles within the channels by a chemical and/or thermal reduction process. The metal nanoparticles have a broad size distribution where the platinum and silver particles are very small (typically 2-6 nm) and the gold particles are much larger (typically 5-30 nm)

Highly efficient nonradiative energy transfer mediated light harvesting in water using aqueous CdTe quantum dot antennas

Cataloged from PDF version of article.We present light harvesting of aqueous colloidal quantum dots to nonradiatively transfer their excitonic excitation energy efficiently to dye molecules in water, without requiring ligand exchange. These as-synthesized CdTe quantum dots that are used as donors to serve as light-harvesting antennas are carefully optimized to match the electronic structure of Rhodamine B molecules used as acceptors for light harvesting in aqueous medium. By varying the acceptor to donor concentration ratio, we measure the light harvesting factor, along with substantial lifetime modifications of these water-soluble quantum dots, from 25.3 ns to 7.2 ns as a result of their energy transfer with efficiency levels up to 86%. Such nonradiative energy transfer mediated light harvesting in aqueous medium holds great promise for future quantum dot multiplexed dye biodetection systems. (C) 2010 Optical Society of America

Творча спадщина М. С. Грушевського в історіодизації української діаспори

Самарська І. О. Творча спадщина М. С. Грушевського в історіодизації української діаспори / І. О. Самарська // Правове життя сучасної України: матеріали Міжнар. наук. конф. проф.-викл. та аспірант. складу / відп. за вип. В. М. Дрьомін; НУ ОЮА, Півд. регіон. центр НАПрН України. – Одеса: Фенікс, 2014. – Т. 2. – С. 140-142.Специфіка ідеологічних дискусій у самому емігрантському середовищі привернула увагу науковців до проблеми обгрунтуваності критики поглядів видатного вченого представниками державницького напрямку, де спостерігається ідеологізація історіографічного пошуку. Вагомість в емігрантському українознавстві голосу представників старшої генерації, що були активними учасниками наукового життя 20—30 х роках, а також значна зацікавленість станом вітчизняної науки, що перебувала за «залізною завісою», уможливили появу численних документально обгрунтованих досліджень, де висвітлювалися різноманітні аспекти. Недоліки діаспорного грушевськознавства були зумовлені слабкістю джерельної бази через неможливість аналізу широкого кола українознавчих видань та архівних матеріалав. Це спричинило загальну фрагментарність грушевськознавчих студій, що позначилося також і на спробах осмислити рецепцію спадщини видатного вченого його сучасниками. I все ж, незважаючи на це, доробок учених діаспори є вагомим етапом грушевськознавства, що став підгрунтям сучасних досліджень