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排序方式: 共有269条查询结果,搜索用时 15 毫秒
261.
Yuki Arakawa Yukito Sasaki Naoki Haraguchi Shinichi Itsuno Hideto Tsuji 《Liquid crystals》2018,45(6):821-830
We synthesised a novel family of liquid crystalline 1,4-phenylene bis(4-alkylthio benzoates), of which homologues with different alkyl chain lengths of 1–8 were designed, to investigate the structure–property relationship. The mesogenic incidence and tendency were found to be strongly dependent on the carbon numbers in the terminal alkyl chains. Even members formed widely monotropic or enantiotropic nematic (N) phases compared to odd members that showed either none or monotropic-narrower ones. The temperature dependence of birefringence (Δn) for the hexylthio homologue was evaluated and compared to that for a hexyloxy counterpart. It was found that the hexylthio homologue exhibited higher Δn values than the hexyloxy counterpart over the entire range of near TIN–T. In addition, wide-angle X-ray diffraction measurements, using magnetically aligned specimens, found enhanced cybotactic nematic tendency with smectic (Sm) A-like temperature dependence for the hexylthio analogue, due to the intermolecular attractive S···S interaction, in comparison with the hexyloxy analogue exhibiting N phase with clear Sm C-type clusters. We revealed the actual benefits of alkylthio groups in the fluid N phase. 相似文献
262.
Kou P. Kawahara Wataru Matsuoka Dr. Hideto Ito Prof. Dr. Kenichiro Itami 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(16):6445-6450
Nitrogen-containing polycyclic aromatic compounds (N-PACs) are an important class of compounds in materials science. Reported here is a new aza-annulative π-extension (aza-APEX) reaction that allows rapid access to a range of N-PACs in 11–84 % yields from readily available unfunctionalized aromatics and imidoyl chlorides. In the presence of silver hexafluorophosphate, arenes and imidoyl chlorides couple in a regioselective fashion. The follow-up oxidative treatment with p-chloranil affords structurally diverse N-PACs, which are very difficult to synthesize. DFT calculations reveal that the aza-APEX reaction proceeds through the formal [4+2] cycloaddition of an arene and an in situ generated diarylnitrilium salt, with sequential aromatizations having relatively low activation energies. Transformation of N-PACs into nitrogen-doped nanographenes and their photophysical properties are also described. 相似文献
263.
Kimata M Terashima T Kurita N Satsukawa H Harada A Kodama K Takehana K Imanaka Y Takamasu T Kihou K Lee CH Kito H Eisaki H Iyo A Fukazawa H Kohori Y Harima H Uji S 《Physical review letters》2011,107(16):166402
Cyclotron resonance (CR) measurements for the Fe-based superconductor KFe(2)As(2) are performed. One signal for CR is observed, and is attributed to the two-dimensional α Fermi surface at the Γ point. We found a large discrepancy in the effective masses of CR [(3.4±0.05)m(e) (m(e) is the free-electron mass)] and de Haas-van Alphen results, a direct evidence of mass enhancement due to electronic correlation. A comparison of the CR and de Haas-van Alphen results shows that both intra- and interband electronic correlations contribute to the mass enhancement in KFe(2)As(2). 相似文献
264.
Hideto Minami Hiroki Fukaumi Masayoshi Okubo Toyoko Suzuki 《Colloid and polymer science》2013,291(1):45-51
Encapsulation of ionic liquid, 1-hexyl-3-methylimidazolium bis(trifluoromethane sulfonyl)amide ([Hmim][TFSA]), was carried out by microsuspension polymerization of ethylene glycol dimethacrylate (EGDM) utilizing the self-assembling of phase-separated polymer method, which had been proposed by us for the preparation of hollow polymer particles. After the optimization of the polymerization conditions, ionic liquid-encapsulated polymer particles, which have smooth surface morphology and a single hollow structure, were successfully prepared. Encapsulation efficiency of [Hmim][TFSA] was significantly improved from about 20–70 % by changing the shell polymer from polyEGDM homopolymer to poly(EGDM-butyl methacrylate) (50/50, w/w) copolymer, which was likely to have relatively low affinity for [Hmim][TFSA]. Additionally, ionic liquid-encapsulated polymer particles displaying ionic conductivity were successfully prepared using triethylene glycol dimethacrylate as divinyl monomer instead of EGDM. 相似文献
265.
Kinoshita K Minami H Tarutani Y Tajima K Okubo M Yanagimoto H 《Langmuir : the ACS journal of surfaces and colloids》2011,27(8):4474-4480
Polystyrene (PS)/aluminum hydroxide (Al(OH)(3)) composite particles were successfully prepared by the sol-gel process of aluminum isopropoxide (Al(OPr(i))(3)) in a hydrophilic ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF(4)]) using ammonium hydroxide (NH(4)OH) as a catalyst in the presence of PS seed. Transmission electron microscopy observation of ultrathin cross-sections of the composite particles revealed that the composite particles had a core-shell morphology consisting of a PS core and a Al(OH)(3) shell having high crystallinity. The amount of secondary nucleated Al(OH)(3) could be reduced by dropwise addition of NH(4)OH. Moreover, PS/η-Al(2)O(3) composite particles were successfully prepared by heat treatment of PS/Al(OH)(3) at 300 °C in N(2) atmosphere, which is below the decomposition temperature of PS. 相似文献
266.
Hideto Yoshida Tetsuya Uchiyama Hideo Kohno Seiji Takeda 《Applied Surface Science》2008,254(23):7586-7590
The growth process of carbon nanotubes (CNTs) under CNT-CNT and CNT-substrate interactions has been observed directly by environmental transmission electron microscopy. Even a free standing CNT occasionally swings during the growth until it touches the substrate. In addition, we show that the growth direction of CNTs changes due to the interaction between CNTs. 相似文献
267.
Undoped and Si-doped AlGaN/AlN multiple quantum wells(MQWs) were grown on AlN/Sapphire templates by metalorganic phase vapor epitaxy.High-resolution x-ray diffraction measurements showed the high interface quality of the MQWs little affected by Si-doping.Room-temperature(RT) cathodoluminescence measurements demonstrated a significant enhancement of the RT deep ultraviolet emission at about 240 nm from the AlGaN/AlN MQWs by Si doping.The mechanism of the improved emission efficiency was that the Si-doping partially screens the internal electric field and thus leads to the increase of the overlap between electron and hole wavefunctions.Further theoretical simulation also supports the above results. 相似文献
268.
Hisayasu Ishibashi Dr. Manuel Rondelli Hiroki Shudo Prof. Dr. Takehisa Maekawa Prof. Dr. Hideto Ito Prof. Dr. Kiichi Mizukami Prof. Dr. Nobuo Kimizuka Prof. Dr. Akiko Yagi Prof. Dr. Kenichiro Itami 《Angewandte Chemie (International ed. in English)》2023,62(44):e202310613
The active metal template (AMT) strategy is a powerful tool for the formation of mechanically interlocked molecules (MIMs) such as rotaxanes and catenanes, allowing the synthesis of a variety of MIMs, including π-conjugated and multicomponent macrocycles. Cycloparaphenylene (CPP) is an emerging molecule characterized by its cyclic π-conjugated structure and unique properties. Therefore, diverse modifications of CPPs are necessary for its wide application. However, most CPP modifications require early stage functionalization and the direct modification of CPPs is very limited. Herein, we report the synthesis of a catenane consisting of [9]CPP and a 2,2′-bipyridine macrocycle as a new CPP analogue that contains a reliable synthetic scaffold enabling diverse and concise post-modification. Following the AMT strategy, the [9]CPP-bipyridine catenane was successfully synthesized through Ni-mediated aryl-aryl coupling. Catalytic C−H borylation/cross-coupling and metal complexation of the bipyridine macrocycle moiety, an effective post-functionalization method, were also demonstrated with the [9]CPP-bipyridine catenane. Single-crystal X-ray structural analysis revealed that the [9]CPP-bipyridine catenane forms a tridentated complex with an Ag ion inside the CPP ring. This interaction significantly enhances the phosphorescence lifetime through improved intermolecular interactions. 相似文献
269.