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排序方式: 共有632条查询结果,搜索用时 31 毫秒
21.
Hiroko Shikata Kazuki Nakanishi Kazuyuki Hirao 《Journal of Sol-Gel Science and Technology》2000,19(1-3):769-773
Microcrystalline silicalite-1 was formed on the inner surface of macroporus silica glasses prepared by the sol-gel process. By heating a homogeneous precursor solution at 100°C under a hydrothermal condition, 2–5 m of plate-like particles of silicalite-1 were deposited. With an increase of mixing time of the precursor solution, the number of silicalite-1 particles increased, accompanied by the relative decrease of the particle size. Depending on the temperature and the duration of the heat-treatment of the macroporous silica, the amount of deposited silicalite-1 varied. Below 1000°C, the amount increased with the heat-treatment temperature, as a result of the competition between the precipitation of silicalite-1 and the dissolution of silica from the macroporous silica glass under a strongly basic condition. On the other hand, above 1000°C the amount of deposited silicalite-1 decreased in accordance with the decrease of the macropore diameter by the heat-treatment, because of the limited transport of the dissolved silicate species through the smaller macropores. 相似文献
22.
Stereoblock poly(lactic acid) consisting of D- and L-lactate stereosequences can be successfully synthesized by solid-state polycondensation of a 1:1 mixture of poly(L-lactic acid) and poly(D-lactic acid). In the first step, melt-polycondensation of L- and D-lactic acids is conducted to synthesize poly(L-lactic acid) and poly(D-lactic acid) with a medium-molecular-weight, respectively. In the next step, these poly(L-lactic acid) and poly(D-lactic acid) are melt-blended in 1:1 ratio to allow formation of their stereocomplex. In the last step, this melt-blend is subjected to solid-state polycondensation at temperature where the dehydrative condensation is allowed to promote chain extension in the amorphous phase with the stereocomplex crystals preserved. Finally, stereoblock poly(lactic acid) having high-molecular-weight is obtained. The stereoblock poly(lactic acid) synthesized by this way shows a higher melting temperature in consequence of the controlled block lengths and the resulting higher-molecular-weight. The product characterization as well as the optimization of the polymerization conditions is described. Changes in M(w) of stereoblock poly(lactic acid) (sb-PLA) as a function of the reaction time. 相似文献
23.
Tachi Y Aita K Teramae S Tani F Naruta Y Fukuzumi S Itoh S 《Inorganic chemistry》2004,43(15):4558-4560
A dicopper(I) complex supported by a novel asymmetric pentapyridine dinucleating ligand, consisting of tetradentate and tridentate metal-binding sites, has been synthesized and characterized. The dicopper(I) complex reacted with molecular oxygen at a low temperature to give an unprecedented mu-peroxo dicopper(II) complex presumably having a mu-eta1:eta2 binding mode, the spectroscopic features and the reactivity of which have been explored in detail. 相似文献
24.
Since the aggregation-induced emission (AIE) phenomenon was first reported by Tang et al., much effort has been devoted to the development of solid-state luminescent molecules by chemists worldwide. Our group successfully developed fluorinated tolanes as novel compact π-conjugated luminophores with blue photoluminescence (PL) in the crystalline state. Moreover, we reported the yellow-green PL molecules based on their electron-density distributions. In the present study, we designed and synthesized fluorinated tolanes with various amine-based donors and evaluated their photophysical properties. The carbazole-substituted fluorinated tolane exhibited strong PL in the solution state, whereas piperidine- or phenothiazine-substituted fluorinated tolanes showed a dramatic decrease in PL efficiency. Notably, fluorinated tolanes with piperidine or phenothiazine substituents displayed yellow-to-orange PL in the crystalline state; this may have occurred because these tolanes exhibited tightly packed structures formed by intermolecular interactions, such as H···F hydrogen bonds, which suppressed the non-radiative deactivation process. Moreover, fluorinated tolanes with amine-based donors exhibited AIE characteristics. We believe that these yellow-to-orange solid PL molecules can contribute to the development of new solid luminescent materials. 相似文献
25.
Prof. Shingo Saito Toshiki Sakamoto Naoki Tanaka Ryo Watanabe Takuya Kamimura Kazuki Ota Kathryn R. Riley Keitaro Yoshimoto Yuiko Tasaki-Handa Masami Shibukawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(39):10058-10067
In DNA aptamer selection, existing methods do not discriminate aptamer sequences based on their binding affinity and function and the reproducibility of the selection is often poor, even for the selection of well-known aptamers like those that bind the commonly used model protein thrombin. In the present study, a novel single-round selection method (SR-CE selection) was developed by combining capillary electrophoresis (CE) with next generation sequencing. Using SR-CE selection, a successful semi-quantitative and semi-comprehensive aptamer selection for thrombin was demonstrated with high reproducibility for the first time. Selection rules based on dissociation equilibria and kinetics were devised to obtain families of analogous sequences. Selected sequences of the same family were shown to bind thrombin with high affinity. Furthermore, data acquired from SR-CE selection was mined by creating sub-libraries that were categorized by the functionality of the aptamers (e. g., pre-organized aptamers versus structure-induced aptamers). Using this approach, a novel fluorescent molecular recognition sensor for thrombin with nanomolar detection limits was discovered. Thus, in this proof-of-concept report, we have demonstrated the potential of a “DNA Aptaomics” approach to systematically design functional aptamers as well as to obtain high affinity aptamers. 相似文献
26.
Dr. Yuki Ohishi Kentaro Masuda Kazuki Kudo Prof. Dr. Hajime Abe Prof. Dr. Masahiko Inouye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(2):785-793
Generally, cage-shaped hosts for saccharides can bind strongly to guest molecules because of the three-dimensional preorganized hydrogen-bonding sites. However, the preparation of cage molecules is often difficult because of the low yield of the macrocyclization step. Here, we report a three-arm-shaped molecule possessing pyridine-acetylene-phenol units as a new kind of host having a preorganized three-dimensional hydrogen-bonding site. This three-arm-shaped host was readily prepared compared to a cage-shaped analogue. This host associated with lipophilic glycosides to form chiral complexes, and the association constants were sufficiently high as to be comparable to those of the cage-shaped analogue. Furthermore, this host extracted native monosaccharides into a lipophilic solvent. 相似文献
27.
Hideaki Takahashi Shin-ichiro Kurimoto Junichi Kobayashi Takaaki Kubota 《Tetrahedron letters》2018,59(51):4500-4502
A new indole alkaloid with the canthin-6-one skeleton, ishigadine A, has been isolated from an Okinawan marine sponge Hyrtios sp. The structure of ishigadine A was elucidated on the basis of spectroscopic analyses. Ishigadine A is a new canthin-6-one alkaloid possessing a hydroxy group, a 1,3-dimethyl-4-methylthioimidazolium, and a 1-propylguanidine. Ishigadine A is the third canthin-6-one alkaloid from sponges. Ishigadine A might be generated from l-arginine, l-histidine, and l-tryptophan. Ishigadine A exhibited moderate cytotoxicity against L1210 murine leukemia cells. 相似文献
28.
29.
Kaisei Matsumoto Kazuki Ueno Prof. Dr. Jun Hirotani Prof. Dr. Yutaka Ohno Prof. Dr. Haruka Omachi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(28):6118-6121
Owing to their remarkable properties, single-walled carbon nanotube thin-film transistors (SWCNT-TFTs) are expected to be used in various flexible electronics applications. To fabricate SWCNT channel layers for TFTs, solution-based film formation on a self-assembled monolayer (SAM) covered with amino groups is commonly used. However, this method uses highly oxidized surfaces, which is not suitable for flexible polymeric substrates. In this work, a solution-based SWCNT film fabrication using methoxycarbonyl polyallylamine (Moc-PAA) is reported. The NH2-terminated surface of the cross-linked Moc-PAA layer enables the formation of highly dense and uniform SWCNT networks on both rigid and flexible substrates. TFTs that use the fabricated SWCNT thin film exhibited excellent performance with small variations. The presented simple method to access SWCNT thin film accelerates the realization of flexible nanoelectronics. 相似文献
30.