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排序方式: 共有1325条查询结果,搜索用时 15 毫秒
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Hajime Maeda Kazuhiro Tanaka Mona Aratani Masahito Segi 《Photochemistry and photobiology》2019,95(3):762-772
Substances containing ethynylpyrenes linked to either one or four benzocrown ethers were synthesized, and their absorption and fluorescence spectroscopic responses to metal ions were assessed. Addition of metal perchlorates to solutions of these substances promotes short wavelength shifts in their absorption and fluorescence maxima and increases in their fluorescence intensities. The magnitudes of the fluorescence intensity increases are dependent on the ring size and number of the crown ether and the nature of the metal cation. Association constants for complex formation were calculated using fluorescence intensity versus concentration data. Analysis using Job's plots showed that the substances containing one benzocrown ether moiety form 1:1 complexes with metal ions. Results of experiments employing repeated addition and removal of Mg(ClO4)2 demonstrate that the ON‐OFF fluorescence response can be repeated at least three times. Results of molecular orbital calculations show that complexation with metal ions lowers the energies of both the π and π* levels of the ethynylpyrene moiety and that in some cases the vacant orbital on the metal becomes the LUMO of the complex. An explanation of the spectroscopic changes promoted by metal ions is proposed in terms of electrostatic repulsion and structural regulation. 相似文献
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Kazunori Masuko Chiharu Kumano Ryo Sugawara Kazuhiro Nakabayashi Hideharu Mori 《Journal of polymer science. Part A, Polymer chemistry》2021,59(15):1664-1677
A series of amino-acid-based amphiphilic diblock copolymer nano-objects having different morphologies were developed by reversible addition–fragmentation chain-transfer (RAFT) dispersion polymerization of styrene (St) in methanol. This was mediated by six different hydrophilic poly(N-acryloyl amino acid) macro-chain transfer agents (CTAs), including three carboxylic-acid-containing ones, poly(N-acryloyl-l -proline) (PAProOH), poly(N-acryloyl-4-trans-hydroxy-l -proline) (PAHypOH), and poly(N-acryloyl-l -threonine) (PAThrOH) prepared by RAFT polymerization, and their methyl ester forms, PAProOMe, PAHypOMe, and PAThrOMe. The effects of polymerization conditions on RAFT dispersion polymerization of St using a dithiocarbamate-terminated PAProOH was investigated. A systematic study of the effects of monomer conversion and concentration afforded the formation of various morphologies (i.e., spheres, worms, and vesicles). The effects of hydrogen-bonding and ionic interactions of the macro-CTAs on the assembled structures of the nano-objects were evaluated using six different macro-CTAs. Transforming the products from methanol to water via dialysis produced amino-acid-based block copolymer nano-objects, exhibiting pH-responsive morphological change, in aqueous solution. 相似文献
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Junki Ochi Kazuhiro Yuhara Prof. Kazuo Tanaka Prof. Yoshiki Chujo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(20):e202200155
It is still challenging to realize a dual-emission system, in which two luminescent bands simultaneously appear by photoexcitation, in solid with organic dyes due to the difficulty in regulation of electronic properties in the excited state and concentration quenching. o-Carborane is known to be a versatile platform for constructing solid-state emitters since the sphere boron cluster is favorable for suppressing intermolecular interactions and subsequently concentration quenching. Here, we show solid-state dual-emissive o-carborane derivatives. We prepared 4 types of o-carborane derivatives and found dual-emission behaviors both in solution and solid states. By regulating the rotation at the o-carborane unit with the intramolecular CcageH⋅⋅⋅O interaction, the dual-emission intensity ratios were changed. Finally, it was demonstrated that the overall photoluminescence spectra can be estimated using the binding energy of intramolecular interactions. 相似文献
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Atsushi Sato Shimpei Okubo Kazuhiro Asai Shoken Ishii Kohei Mizutani 《Applied physics. B, Lasers and optics》2014,117(2):621-631
The effect of lower-laser-level lifetimes on Q-switched pulse generation in a dual-wavelength solid-state laser with a common upper laser level was numerically and experimentally investigated. A rate-equation model that accounts for finite lower-laser-level lifetimes was developed, and for a Nd:YAG laser operating at 1064 and 1319 nm, numerical simulations of dual-wavelength pulse generation were performed with and without the effects of lower-laser-level lifetimes. In the laser experiments, characteristics of the dual-wavelength Q-switched pulses agree reasonably well with theoretical predictions. As a result, we found that both the total energy of the two Q-switched pulses and the ratio of 1064–1319-nm pulse energies were strongly affected by the lower-laser-level lifetimes when the Q-switched pulse width was comparable or shorter than the lower-laser-level lifetime. 相似文献
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Spontaneous Formation of Microgroove Arrays on the Surface of p‐Type Porous Silicon Induced by a Turing Instability in Electrochemical Dissolution 下载免费PDF全文
Prof. Dr. Kazuhiro Fukami Tomoko Urata Prof. Dr. Katharina Krischer Prof. Dr. Naoya Nishi Prof. Dr. Tetsuo Sakka Dr. Atsushi Kitada Prof. Dr. Kuniaki Murase 《Chemphyschem》2015,16(8):1613-1618
Self‐organization plays an imperative role in recent materials science. Highly tunable, periodic structures based on dynamic self‐organization at micrometer scales have proven difficult to design, but are desired for the further development of micropatterning. In the present study, we report a microgroove array that spontaneously forms on a p‐type silicon surface during its electrodissolution. Our detailed experimental results suggest that the instability can be classified as Turing instability. The characteristic scale of the Turing‐type pattern is small compared to self‐organized patterns caused by the Turing instabilities reported so far. The mechanism for the miniaturization of self‐organized patterns is strongly related to the semiconducting property of silicon electrodes as well as the dynamics of their surface chemistry. 相似文献
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Inside Cover: Spontaneous Formation of Microgroove Arrays on the Surface of p‐Type Porous Silicon Induced by a Turing Instability in Electrochemical Dissolution (ChemPhysChem 8/2015) 下载免费PDF全文
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Dr. Trapti Aggarwal Kenshiro Hada Yusuke Murata Dr. Yuji Sumii Kazuhiro Tanagawa Kiyoteru Niina Soichiro Mori Dr. Jorge Escorihuela Prof. Dr. Norio Shibata 《Angewandte Chemie (International ed. in English)》2023,62(33):e202307090
Alkyne hydroamination is an effective approach for the production of enamines and enamine-containing N-heterocycles. However, stereoselectivity control is a considerable challenge in this reaction because of the electronic repulsion between an incoming nitrogen lone pair and the alkyne π-system. Herein, we propose a methodology involving β-regio- and Z-selective alkyne hydroamination by using tetrafluoro-λ6-sulfanyl (SF4) alkynes under superbasic, naked anion conditions. The reaction is compatible with a wide variety of N-heterocycles, including indoles, carbazoles, pyrazoles, and imidazoles, and selectively furnishes SF4-linked Z-vinyl enamines with β-regioselectively. Moreover, the method can be extended to the β- and Z-controlled, base-mediated alkyne hydrophenoxylation with phenols to provide SF4-linked Z-vinyl ethers in high yields. As the SF4 unit has attracted attention as a bioisostere for alkynes, p-benzenes, bicyclo[1.1.1]pentyl (BCP) groups, and cubanes in medicinal chemistry, this chemistry represents an effective approach to creating novel drug candidates incorporating SF4-containing molecules. 相似文献