排序方式: 共有23条查询结果,搜索用时 78 毫秒
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Tomasz Stawski Janusz Szklarzewicz Krzysztof Lewiński 《Transition Metal Chemistry》2006,31(3):353-361
The single crystal X-ray structure of (AsPh4)[W(bpy)(CN)6] is described. The structure of octa- and hepta-coordinated intermediates of substitutional photolysis of [Mo(CN)8]4− ion in aqueous media were determined by performing semi-empirical calculations. On the basis of obtained results as well
as on empirical data the photolysis scheme has been postulated. 相似文献
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Summary The kinetics of nucleophilic addition of dipropylamine to vinyl groups of starch acrylate has been investigated. The reactions were carried out under pseudo-first order conditions in tetrahydrofuran with excess amine within the temperature range from 25 to 45oC. Pseudo-first-order rate constants for addition and the activation energy have been determined. 相似文献
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Dawid Stawski 《Polymer Testing》2009,28(2):223-225
Low viscosity polypropylene is a new group of homopolymers for the manufacture of melt-blown nonwovens. The thermooxidative degradation of isotactic polypropylene was studied. Experiments using varied sample size and flow rates were undertaken to determine possible effects of these experimental parameters on the low viscosity thermo-oxidation process. It was found that the results of thermogravimetric analysis (temperature of 50%) of low viscosity polypropylene samples very strongly depend on the weight of the sample. The influence of gas flow conditions, sample pan geometry and sample melt flow rates parameters on the results of thermogravimetric analysis has not been observed. 相似文献
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Stawski TM Besselink R Veldhuis SA Castricum HL Blank DH ten Elshof JE 《Journal of colloid and interface science》2012,369(1):184-192
The evolution of nanostructure in sol-gel derived lead zirconate titanate (PZT) and zirconia precursor sols at different hydrolysis ratios was investigated by small angle X-ray scattering (SAXS). The shape of the clusters in the zirconia sol could be described by the length-polydisperse cylindrical form factor. The zirconia-based clusters were characterized by a cross-sectional radius, r(0), of 0.28 nm and a practically monodisperse length of ca. 1.85 nm. These clusters were probably constructed of zirconia-related tetrameric building blocks. Similar cylindrical structural motifs were observed in PZT precursor sols with [H(2)O]/[Zr+Ti]=9.26 and 27.6, but the polydispersity in length was much higher. Clear scattering contributions from Ti and Pb centers were not detected, which was interpreted in terms of a homogeneous distribution of unbound lead ions in solution and the relatively low scattering intensity from any Ti-based clusters or oligomers that may have been present in the sols. 相似文献
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Stawski TM Veldhuis SA Castricum HL Keim EG Eeckhaut G Bras W Blank DH ten Elshof JE 《Langmuir : the ACS journal of surfaces and colloids》2011,27(17):11081-11089
The structural evolution of sol-gel derived lead zirconate titanate (PZT) precursor films during and after physical drying was investigated by transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), selected area electron diffraction (SAED), and time-resolved X-ray diffraction (XRD). Films were deposited from initial 0.3 mol/dm(3) precursor sols with varying hydrolysis ratios. Zr-rich grains of 1-10 nm size, embedded in a Pb-, Zr-, and Ti-containing amorphous matrix were found in as-dried films. The Zr-rich regions were crystalline at hydrolysis ratios [H(2)O]/[PZT] < 27.6, and amorphous at ratios > 100. X-ray diffraction analysis of PZT and zirconia sols revealed that the crystalline nanoparticles in both sols are identical and are probably composed of nanosized zirconium oxoacetate-like clusters. This study demonstrates that time-resolved X-ray diffraction combined with electron energy loss spectroscopy mapping is a powerful tool to monitor the nanoscale structural evolution of sol-gel derived thin films. 相似文献
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Wojciech Stawski Karolina Hurej Janusz Skonieczny Miosz Pawlicki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(32):11062-11066
The formation of a precisely designed environment predefined for stabilizing electron‐deficient atoms, such as boron(III), is an important approach for optimizing the properties of a chromophore. A triphyrin(2.1.1) motif built on the extended π‐system of a tetraphyrin(1.1.1.1) skeleton creates a new coordination environment, with a CNN set of donors confined in a limited space predefined for binding small cations. The entrapment of boron(III) in the triphyrin(2.1.1) sector, with formation of a direct B?C bond, significantly changes the optical response and the global aromatic character of the compound, leading to an extension of the π‐delocalisation. 相似文献
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Formation Mechanism of a Nano-Ring of Bismuth Cations and Mono-Lacunary Keggin-Type Phosphomolybdate
Dr. Inês C. B. Martins Dominik Al-Sabbagh Dr. Ursula Bentrup Dr. Julien Marquardt Dr. Thomas Schmid Dr. Ernesto Scoppola Werner Kraus Dr. Tomasz M. Stawski Dr. Ana Guilherme Buzanich Dr. Kirill V. Yusenko Dr. Steffen Weidner Dr. Franziska Emmerling 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(27):e202200079
A new hetero-bimetallic polyoxometalate (POM) nano-ring was synthesized in a one-pot procedure. The structure consists of tetrameric units containing four bismuth-substituted monolacunary Keggin anions including distorted [BiO8] cubes. The nano-ring is formed via self-assembly from metal precursors in aqueous acidic medium. The compound (NH4)16[(BiPMo11O39)4] ⋅ 22 H2O; (P4Bi4Mo44) was characterized by single-crystal X-ray diffraction, extended X-ray absorption fine structure spectroscopy (EXAFS), Raman spectroscopy, matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF), and thermogravimetry/differential scanning calorimetry mass spectrometry (TG-DSC-MS). The formation of the nano-ring in solution was studied by time-resolved in situ small- and wide-angle X-ray scattering (SAXS/WAXS) and in situ EXAFS measurements at the Mo−K and the Bi−L3 edge indicating a two-step process consisting of condensation of Mo-anions and formation of Bi−Mo-units followed by a rapid self-assembly to yield the final tetrameric ring structure. 相似文献
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