排序方式: 共有139条查询结果,搜索用时 15 毫秒
31.
Serap Beli Simon J. Coles Derya Davarc David B. Davies Michael B. Hursthouse Adem Kl 《Polyhedron》2007,26(18):5283-5292
Reaction of cyclophosphazene, N3P3Cl6 (1), with the sodium derivative of the fluorinated diol, 2,2,3,3,4,4-hexafluoropentane-1,5-diol (2), in THF solution at room temperature afforded five isolated products, whose structures have been characterised by X-ray crystallography and 1H, 19F and 31P NMR spectroscopy: the mono-spiro compound, N3P3Cl4(OCH2CF2CF2CF2CH2O) (3), its ansa isomer (4), a di-spiro derivative N3P3Cl2(OCH2CF2CF2CF2CH2O)2 (5), its spiro-ansa (6) isomer and the tri-spiro compound N3P3(OCH2CF2CF2CF2CH2O)3 (7). Quantitative 31P NMR measurements of the soluble portion of the reaction mixture show that in the reaction of (1) with the sodium derivative of the fluorinated pentanediol (2) there is a small preference for spiro compounds compared to ansa compounds (ratio ca. 1.3:1), similar to the analogous reaction of (1) with the sodium derivative of the fluorinated butanediol where there is a slightly greater proportion of spiro compared to ansa compounds (ratio ca. 1.5:1). The relative proportions of spiro and ansa compounds is likely to depend on the fine balance in stabilities of the different medium-sized rings in the fluorinated pentanediol (spiro, 8- and ansa, 10-membered rings) compared to the fluorinated butanediol (spiro, 7- and ansa, nine-membered rings) derivatives of cyclophosphazene. 相似文献
32.
The TiO2 nanoparticles are electrospun with polyacrylonitrile (PAN) polymer solution onto the discharged battery coal (DBC) electrode and the results are evaluated as a supercapacitor. The morphology and chemical composition of the synthesized TiO2 nanoparticles and PAN+TiO2 nanocomposite fibers were characterized by Scanning electron microscopy, thermogravimetry and FTIR analysis. Supercapacitor measurements and electrochemical characterizations of the electrodes examined by cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical measurements showed that the best current value was obtained from PAN and TiO2 coated DBC. The performances of both PAN and PAN+TiO2 coated DBC electrodes were investigated as supercapacitors. PAN+TiO2/DBC showed the best specific capacitance value of 156.00 F g−1 and PAN/DBC showed 74.93 F g−1. In addition, PAN+TiO2/DBC exhibited reliable stability performance over 2000.00 cycles. 相似文献
33.
Arzum Erdem Pagona Papakonstantinou Hayley Murphy Martin McMullan Hakan Karadeniz Surbhi Sharma 《Electroanalysis》2010,22(6):611-617
Disposable graphite pencil electrodes (PGE) modified with multiwalled carbon nanotubes (MWCNTs)‐streptavidin (STR) conjugates were used for electrochemical monitoring of label‐free DNA hybridization. The surface morphology of PGE electrode before and after hybridization was characterized by scanning electron microscopy. Electrochemical impedance spectroscopy was used to monitor each step of the construction of the DNA biosensor. The biosensor was demonstrated to have excellent selectivity, being able to differentiate complementary sequences from a noncomplementary ones and in addition select the target sequence of DNA from a mixture of other DNA without loss in current sensitivity. 相似文献
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35.
A. Birkan Seluk N. Tuluolu S. Karadeniz S. Bilge Ocak 《Physica B: Condensed Matter》2007,400(1-2):149-154
In this work, the investigation of the interface state density and series resistance from capacitance–voltage (C–V) and conductance–voltage (G/ω−V) characteristics in In/SiO2/p-Si metal–insulator–semiconductor (MIS) structures with thin interfacial insulator layer have been reported. The thickness of SiO2 film obtained from the measurement of the oxide capacitance corrected for series resistance in the strong accumulation region is 220 Å. The forward and reverse bias C–V and G/ω−V characteristics of MIS structures have been studied at the frequency range 30 kHz–1 MHz at room temperature. The frequency dispersion in capacitance and conductance can be interpreted in terms of the series resistance (Rs) and interface state density (Dit) values. Both the series resistance Rs and density of interface states Dit are strongly frequency-dependent and decrease with increasing frequency. The distribution profile of Rs–V gives a peak at low frequencies in the depletion region and disappears with increasing frequency. Experimental results show that the interfacial polarization contributes to the improvement of the dielectric properties of In/SiO2/p-Si MIS structures. The interface state density value of In/SiO2/p-Si MIS diode calculated at strong accumulation region is 1.11×1012 eV−1 cm−2 at 1 MHz. It is found that the calculated value of Dit (≈1012 eV−1 cm−2) is not high enough to pin the Fermi level of the Si substrate disrupting the device operation. 相似文献
36.
Acceptorless Dehydrogenative Oxidation of Secondary Alcohols Catalysed by Cp*IrIII–NHC Complexes
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Prof. Süleyman Gülcemal Prof. Derya Gülcemal Dr. George F. S. Whitehead Prof. Jianliang Xiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10513-10522
A series of new IrIII complexes with carbene ligands that contain a range of benzyl wingtip groups have been prepared and fully characterised by NMR spectroscopy, HRMS, elemental analysis and X‐ray diffraction. All the complexes were active in the acceptorless dehydrogenation of alcohol substrates in 2,2,2‐trifluoroethanol to give the corresponding carbonyl compounds. The most active complex bore an electron‐rich carbene ligand; this complex was used to catalyse the highly efficient and chemoselective dehydrogenation of a wide range of secondary alcohols to their respective ketones, with turnover numbers up to 1660. Mechanistic studies suggested that the turnover of the dehydrogenation reaction is limited by the H2‐formation step. 相似文献
37.
As higher radiation levels are associated with granodiorite area and the maps are more practical to interpret the results of radiological survey, the distributions of the specific activities of 226Ra, 232Th, 40K in soil-granite samples and indoor 222Rn activities throughout the granodiorite area of Bergama (Pergamon) were mapped in detail. Samples from the granites and soils underlying Kozak-Bergama (Pergamon) granodiorite area were collected and analyzed by HPGe gamma spectrometry system, while indoor radon levels in 20 dwellings of rural areas at this area were measured by the alpha track etch integrated method. This paper represents the baseline maps of natural radioactivity levels (226Ra, 232Th, 40K and 222Rn) and corresponding absorbed dose rates from outdoors terrestrial gamma radiation. 相似文献
38.
Design of novel substituted phthalocyanines; synthesis and fluorescence,DFT, photovoltaic properties
Mehmet Salih AIRTA Derya GÜNG
RDÜ SOLUN Ümit YILDIKO Abdullah
ZKARTAL 《Turkish Journal of Chemistry》2020,44(6):1574
The 4-(2-[3,4-dimethoxyphenoxy] phenoxy) phthalonitrile was synthesized as the starting material of new syntheses. Zinc, copper, and cobalt phthalocyanines were achieved by reaction of starting compound with Zn(CH3COO)2, CuCl2, and CoCl2 metal salts. Basic spectroscopic methods such as nuclear magnetic resonance electronic absorption, mass and infrared spectrometry were used in the structural characterization of the compounds. Absorption, excitation, and emission measurements of the fluorescence zinc phthalocyanine compound were also investigated in THF. Then, structural, energy, and electronic properties for synthesized metallophthalocyanines were determined by quantum chemical calculations, including the DFT method. The bandgap of HOMO and LUMO was determined to be chemically active. Global reactivity (I, A, η, s, μ, χ, ω) and nonlinear properties were studied. In addition, molecular electrostatic potential (MEP) maps were drawn to identify potential reactive regions of metallophthalocyanine (M-Pc) compounds. Photovoltaic performances of phthalocyanine compounds for dye sensitive solar cells were investigated. The solar conversion efficiency of DSSC based on copper, zinc, and cobalt phthalocyanine compounds was 1.69%, 1.35%, and 1.54%, respectively. The compounds have good solubility and show nonlinear optical properties. Zinc phthalocyanine gave fluorescence emission. 相似文献
39.
Quantitative Mobility Spectrum Analysis for Determination of Electron and Magneto Transport Properties of Te-Doped GaSb 下载免费PDF全文
S. Acar M. Kasap B. Y. Isik S. Oezcelik N. Tugluoglu S. Karadeniz 《中国物理快报》2005,22(9):2363-2366
Resistivity, magnetoresistivity and Hall effect measurements in n-type Te-doped GaSb grown by the liquid encapsuled Czochralski technique are carried out as functions of temperature (35-350 K) and magnetic field (0-1.35 T). The power law model is used to explain the temperature-dependent resistivity. The magnetic-field-dependent data are analysed using the quantitative mobility spectrum analysis technique. The effect of individual band parameters (nL, nr, μL, μr, p and μp) on both the electron and magneto transports have been discussed. The EL - Er energy separation between the L and conduction band edges is also derived. 相似文献
40.
Emin Aydın Ali Delice Derya Demiroğlu 《BSHM Bulletin: Journal of the British Society for the History of Mathematics》2016,31(3):215-229
Research in history of mathematics gained momentum in the past two decades in Turkey. The present paper aims to describe the patterns in the history of mathematics research in Turkey and to analyse the research in Turkey using a mathematics education framework. The qualitative paradigm and a case study design are used in the study. The obtained data were analysed by using the document analysis technique with the help of a content analysis. The study group which is comprised of twenty-two postgraduate theses at master's or doctoral level were purposefully selected from the higher education council postgraduate theses database. Findings indicate a dearth of research in the area and that most of the theses are done in the area of mathematics education. Moreover, the focus, in general, was on attitudinal variables, and cognitive aspects seemed to be ignored. 相似文献