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排序方式: 共有201条查询结果,搜索用时 15 毫秒
101.
Tim Dumslaff Yanwei Gu Giuseppe M. Patern Zijie Qiu Ali Maghsoumi Matteo Tommasini Xinliang Feng Francesco Scotognella Akimitsu Narita Klaus Müllen 《Chemical science》2020,11(47):12816
There are three possible isomers for hexa-peri-hexabenzocoronene (HBC) with two extra K-regions, but only two of them have been reported, namely with the meta- and para-configurations. Herein, we describe the synthesis of HBC 4 with two extra K-regions in the ortho-configuration, forming a longer zigzag edge compared with the other two isomers. The structure of 4 was validated by laser desorption/ionization time-of-flight mass analysis and nuclear magnetic resonance spectra, as well as Raman and infrared spectroscopies supported by density functional theory calculations. The optical properties of 4 were investigated by UV/vis absorption and ultrafast transient absorption spectroscopy. Together with the analysis of aromaticity, the influence of the zigzag edge on the π-conjugation pathway and HOMO–LUMO gaps of the three isomers were investigated.We reported the synthesis of hexa-peri-benzocoronene (HBC) with two extra K-regions adopting an ortho-configuration. The systematical study provides deep insights about the effect of zigzag edge on the π-conjugated pathway and molecular design. 相似文献
102.
Shogo Watanabe Atsushi Asano Shu Seki Masaki Sugimoto Masahito Yoshikawa Tagawa Seiichi Satoshi Tsukuda Shun-Ichiro Tanaka 《Radiation Physics and Chemistry》2009,78(12):1071-1075
The direct formation of nanowires consisting of cyclodextrins by single particle nanofabrication technique (SPNT) is investigated in the present paper. Substittuted cyclodextrin (CD) derivatives and their composite with poly(4-bromostyrene) caused efficient cross-linking reaction upon irradiation, and gave nanostructures by SPNT. Successful visualization of the nanostructures by atomic force microscopy suggested drastic increase in the surface area of the materials based on CDs, leading to considerable increase in the selective adsorption efficiency of the molecules fit to the size of the hydrophobic holes of CDs. 相似文献
103.
Hayashi Y Tanaka Y Kirimura T Tsukuda N Kuramoto E Ishikawa T 《Physical review letters》2006,96(11):115505
Acoustic pulse echoes generated by femtosecond laser irradiation were detected using time-resolved x-ray triple-crystal diffractometry. The determined time-dependent longitudinal strain component for pulse echoes in silicon and gallium arsenide plates showed that the polarity of the strain pulse was dependent on the optically induced initial stress, and that the bipolar pulse waveform was gradually deformed and broadened in the course of propagation. The three-dimensional wave front distortion of pulse echoes was shown simply as the pulse duration broadening, which was consistent with a boundary roughness for an unpolished plate. 相似文献
104.
K. Kawashima M. Kriener M. Ishii Y. Maeno J. Akimitsu 《Physica C: Superconductivity and its Applications》2008,468(6):464-470
We report normal-state and superconducting properties of the clathrate-type silver-oxide Ag6O8AgHF2. We present electrical resistivity, DC- and AC-susceptibility and specific-heat measurements of single crystalline Ag6O8AgHF2. In the normal state, Ag6O8AgHF2 exhibits metallic conductivity and a phase transition near 110 K, possibly a structural phase transition as observed in the related compound Ag6O8AgNO3. The onset of superconductivity of our samples is observed around 1.2–1.5 K, and the H–T phase diagram is determined for the first time. The upper critical field Hc2(0) is estimated to be about 2000–2200 Oe and the coherence length ξGL(0) to be 40 nm. 相似文献
105.
Substituted strontium ferrite SrFe9(Mn0.5Co0.5Zr)3/2O19 has been prepared from sol–gel method. X-ray diffraction (XRD), transmission electron microscope (TEM) and vector network analyzer, were used to analyze the structure and dynamic magnetic properties. Powders of sample show a hexagonal fine platelet structure and narrow particle size distribution. Based on microwave measurement on reflectivity, SrFe9(Mn0.5Co0.5Zr)3/2O19 may be a good candidate for electromagnetic compatibility and other practical applications at high frequency. 相似文献
106.
Masako Akimitsu Tadashi Mizoguchi Jun Akimitsu Shigeyuki Kimura 《Journal of Physics and Chemistry of Solids》1983,44(6):497-505
The magnetic structure of non-stoichiometric Fe1?xO was investigated by neutron scattering measurements on a quenched single crystal of Fe0.91O below the Néel temperature. In each defect cluster, there exist ferromagnetic moments and they are arranged antiferromagnetically with the periodicity of twice that of the atomic superstructure. Relation between the defect structure and the magnetic properties for a wide range of compositions was discussed. 相似文献
107.
Site-specific discrimination of Cytosine and 5-methylcytosine in duplex DNA by Peptide nucleic acids 总被引:2,自引:0,他引:2
For site-specific discrimination of cytosine (C) and 5-methylcytosine (mC) in duplex DNA, we developed a new method using peptide nucleic acids (PNAs). The combination of a PNA-assisted DNA displacement complex and a fluorescein-labeled probe oligomer allowed the detection of mC at the defined sites in target DNA using a restriction enzyme. After treatment of the complex with a restriction enzyme, strong fluorescence emission was observed for the complex containing C at the target site, whereas the fluorescence intensity for the complex containing mC was extremely weak. 相似文献
108.
High-resolution photoemission study of MgB2 总被引:1,自引:0,他引:1
We have performed high-resolution photoemission spectroscopy on MgB2 and observed opening of a superconducting gap with a narrow coherent peak. We found that the superconducting gap is s like with the gap value ( Delta) of 4.5+/-0.3 meV at 15 K. The temperature dependence (15-40 K) of the gap value follows well the BCS form, suggesting that 2Delta/k(B)T(c) at T = 0 is about 3. No pseudogap behavior is observed in the normal state. The present results strongly suggest that MgB2 is categorized into a phonon-mediated BCS superconductor in the weak-coupling regime. 相似文献
109.
Taketoshi Matsumoto Patricia Nickut Hironori Tsunoyama Tatsuya Tsukuda Yoshiyasu Matsumoto 《Surface science》2007,601(22):5121-5126
Deposition and fabrication of films of Au nanoclusters protected by alkanethiolate ligands are attempted on a TiO2(1 1 0) surface and the structures of films are observed by a scanning tunneling microscope (STM). Effects of oxygen and hydrogen-plasma etching in addition to UV irradiation on the structure and chemical composition of the films are also investigated by using STM and X-ray photoelectron spectroscopy. Alkanethiolate Au nanoclusters are produced using a modified Brust synthesis method and their LB films are dip-coated on TiO2(1 1 0). Alkanethiolate Au nanoclusters are weakly bound to the substrate and can be manipulated with an STM tip. Net-like structures of alkanethiolate Au nanoclusters are formed by a strong blast of air. Oxygen-plasma etching removes alkanethiolate ligands and simultaneously oxidizes Au clusters. At room temperature, prolonged oxygen-plasma etching causes agglomeration of Au nanoclusters. UV irradiation removes ligands partly, which makes Au nanoclusters less mobile. The net-like structure of alkanethiolate Au clusters produced by a blast of air is retained after oxygen and hydrogen-plasma etching. 相似文献
110.