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991.
Formation of the unstable cis-formic acid in solid argon matrix is induced by direct excitation of the 6<--0 transition of the nu(OH) vibration of the trans-formic acid. The experiment utilizes strongly focused laser beam that produces relatively high isomerization rate despite the low cross section of the absorption. Raman spectroscopy in a backscattering geometry is used for detection of the reactants and the products. This experimental arrangement allow us to use the same laser source for simultaneous pumping and Raman excitation, and it also guarantees that the excited and probed volumes overlap. The presented method has a high potential for solid state investigations of chemical reactions on the ground electronic state. 相似文献
992.
Mitsumi M Ueda H Furukawa K Ozawa Y Toriumi K Kurmoo M 《Journal of the American Chemical Society》2008,130(43):14102-14104
Partially oxidized one-dimensional (1D) Pt-Pt chain compounds [Pt2(MeCS2)4]4ClO4.5PhCN (1) and [Pt2(EtCS2)4]5(ClO4)2 (2) were synthesized by electrocrystallization of diplatinum(II,II) complexes from different solvents. 1 and 2 consist of 1D Pt-Pt chains of stacked Pt-Pt dimers with short interdimer S...S contacts. Depending on the number of ClO4- per dimer and their positions, 1 forms a regular stack of Pt-Pt dimers, whereas 2 forms pentamer of dimers in the 1D chain. 1 exhibits high electrical conductivity (4.2-8.0 S cm-1) at 300 K and metallic behavior above 125 K. 2 is a semiconductor. 1 exhibits almost temperature independent magnetic susceptibility (ca. 1.1 x 10-4 emu mol-1) which is attributed to Pauli paramagnetism, whereas the spin degree of freedom in 2 has been lost. Although the basic structures are closely related, they exhibited different solid-state properties that depend on the valence state of the platinum atoms and the periodicity within the 1D chain. 相似文献
993.
Kai K Yoshida Y Kageyama H Saito G Ishigaki T Furukawa Y Kawamata J 《Journal of the American Chemical Society》2008,130(47):15938-15943
Preparation of single-layer manganese oxide nanosheets (monosheets) comprised of edge-shared MnO(6) octahedra has relied on multistep processing involving a high-temperature solid-state synthesis of bulk templates, and ion-exchange and exfoliation reactions in solutions, requiring high cost and long processing time. Here we demonstrate the first single-step approach to directly access the MnO(2) monosheets, by the chemical oxidation of Mn(2+) ions in the presence of tetramethylammonium cations in an aqueous solution. Of importance is that this template-free reaction readily proceeds within a day at room temperature. The ability of the MnO(2) monosheets to self-assemble allows aggregation, to form layered structures with potassium cations and cationic tetrathiafulvalene analogues as intercalants. Furthermore, Langmuir-Blodgett (LB) films composed of the MnO(2) monosheets were successfully fabricated by the LB deposition method, in which about one layer of the monosheets was deposited for each process. 相似文献
994.
Four novel chiral anionic surfactants having carbohydrate hydrophilic heads, sodium n-dodecyl 1-thio-beta-D-glucopyranoside 6-hydrogen sulfate (6-betaGlcD), sodium n-dodecyl 1-thio-beta-L-glucopyranoside 6-hydrogen sulfate (6-betaGlcL), sodium n-dodecyl 1-thio-beta-L-fucopyranoside 3-hydrogen sulfate (3-betaFucL), and sodium n-dodecyl 1-thio-alpha-L-rhamnopyranoside 3-hydrogen sulfate (3-alphaRhaL), were synthesized by selective sulfation of the corresponding thioglycosides. Their CMC determined by fluorescence using pyrene as a probe in water was 1.3-2.7 mM. These surfactants found to be useful as chiral selectors for enantiomeric separation by MEKC. The enantiomeric separation was optimized with respect to pH, buffer concentration, and surfactant concentration. Under the optimized conditions (50 mM phosphate buffer at pH 6.5, 30 mM surfactant, 20 kV), the enantiomeric separations of five dansylated amino acids (Dns-AAs) were achieved within approximately 20 min with the migration order of Val相似文献
995.
Dr. Jun Harada Haruka Takahashi Rin Notsuka Mika Takehisa Dr. Yukihiro Takahashi Tomoyasu Usui Dr. Hiroki Taniguchi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(3):e202215286
Among ferroelectric crystals based on small molecules, plastic/ferroelectric crystals are currently receiving particular attention because they can be used as bulk polycrystals. Herein, we show that an ionic molecular ferroelectric crystal, guanidinium tetrafluoroborate, exhibits significant malleability and multiaxial ferroelectricity despite the absence of a plastic crystal phase. Powder samples of this crystal can be processed into transparent bulk crystalline plates either by press-forming or by melt-growing. The plates show high ferroelectric performance and related properties, demonstrating the largest hitherto reported spontaneous polarization for bulk polycrystals of small-molecule-based ferroelectrics. Owing to the ready availability of large-scale materials and processability into various bulk crystalline forms, this ferroelectric crystal represents a highly promising functional material that will boost research on diverse applications as bulk crystals. 相似文献
996.
Atomic layer deposition as pore diameter adjustment tool for nanoporous aluminum oxide injection molding masks 总被引:2,自引:0,他引:2
Miikkulainen V Rasilainen T Puukilainen E Suvanto M Pakkanen TA 《Langmuir : the ACS journal of surfaces and colloids》2008,24(9):4473-4477
The wetting properties of polypropylene (PP) surfaces were modified by adjusting the dimensions of the surface nanostructure. The nanostructures were generated by injection molding with nanoporous anodized aluminum oxide (AAO) as the mold insert. Atomic layer deposition (ALD) of molybdenum nitride film was used to control the pore diameters of the AAO inserts. The original 50-nm pore diameter of AAO was adjusted by depositing films of thickness 5, 10, and 15 nm on AAO. Bis(tert-butylimido)-bis(dimethylamido)molybdenum and ammonia were used as precursors in deposition. The resulting pore diameters in the nitride-coated AAO inserts were 40, 30, and 20 nm, respectively. Injection molding of PP was conducted with the coated inserts, as well as with the non-coated insert. Besides the pore diameter, the injection mold temperature was varied with temperatures of 50, 70, and 90 degrees C tested. Water contact angles of PP casts were measured and compared with theoretical contact angles calculated from Wenzel and Cassie-Baxter theories. The highest contact angle, 140 degrees , was observed for PP molded with the AAO mold insert with 30-nm pore diameter. The Cassie-Baxter theory showed better fit than the Wenzel theory to the experimental values. With the optimal AAO mask, the nanofeatures in the molded PP pieces were 100 nm high. In explanation of this finding, it is suggested that some sticking and stretching of the nanofeatures occurs during the molding. Increase in the mold temperature increased the contact angle. 相似文献
997.
Purity certified reference materials (CRMs) are playing a key role in metrological traceability, because they form the basis
for many traceability chains in chemistry. Recently, the National Metrology Institute of Japan (NMIJ) has developed two purity
CRMs for creatinine (NMIJ CRM 6005-a) and urea (NMIJ CRM 6006-a), because the concentrations of these two compounds are frequently
measured in clinical laboratories for monitoring the renal functions. In the certification of purity CRMs, it is essential
that the materials have been thoroughly characterized for purity, and the purity should preferably be determined directly
by a primary method of measurements. In the development of these two CRMs, we used the purified materials as candidates. The
certified values were assigned based on the results of two different methods; acidimetric titration and nitrogen determination
by the Kjeldahl method. Since both methods cannot distinguish some impurities from the target compounds, major impurities
in the candidate materials were also identified, quantified, and subtracted. These CRMs can provide a traceability link between
routine clinical methods and SI units.
Presented at BERM-11, October 2007, Tsukuba, Japan. 相似文献
998.
Dr. Yuta Morinaka Dr. Rui Zhang Dr. Satoru Sato Dr. Hidefumi Nikawa Prof. Dr. Tatsuhisa Kato Prof. Dr. Ko Furukawa Prof. Dr. Michio Yamada Prof. Dr. Yutaka Maeda Dr. Michihisa Murata Prof. Dr. Atsushi Wakamiya Prof. Dr. Shigeru Nagase Prof. Dr. Takeshi Akasaka Prof. Dr. Yasujiro Murata 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(23):6588-6591
To investigate the intrinsic reactivity of atomic nitrogen, which had previously been accomplished only by examining its decay in the gas phase using special equipment, a nitrogen atom was inserted into a series of molecule-encapsulating C60 and C70 fullerenes. Among the studied endofullerenes, H2@C70 was able to encapsulate an additional nitrogen atom within the fullerene cage under radiofrequency plasma conditions. The product was analyzed by ESR spectroscopy and mass spectrometry in solution, which revealed that the nitrogen atom with a quartet ground state does not react but weakly interact with the H2 molecule, thus demonstrating the utility of such fullerenes as “nanoflasks”. 相似文献
999.
Water‐Mediated Recognition of Simple Alkyl Chains by Heart‐Type Fatty‐Acid‐Binding Protein
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Dr. Shigeru Matsuoka Dr. Shigeru Sugiyama Dr. Daisuke Matsuoka Mika Hirose Dr. Sébastien Lethu Hikaru Ano Dr. Toshiaki Hara Dr. Osamu Ichihara Dr. S. Roy Kimura Dr. Satoshi Murakami Hanako Ishida Dr. Eiichi Mizohata Dr. Tsuyoshi Inoue Dr. Michio Murata 《Angewandte Chemie (International ed. in English)》2015,54(5):1508-1511
Long‐chain fatty acids (FAs) with low water solubility require fatty‐acid‐binding proteins (FABPs) to transport them from cytoplasm to the mitochondria for energy production. However, the precise mechanism by which these proteins recognize the various lengths of simple alkyl chains of FAs with similar high affinity remains unknown. To address this question, we employed a newly developed calorimetric method for comprehensively evaluating the affinity of FAs, sub‐Angstrom X‐ray crystallography to accurately determine their 3D structure, and energy calculations of the coexisting water molecules using the computer program WaterMap. Our results clearly showed that the heart‐type FABP (FABP3) preferentially incorporates a U‐shaped FA of C10–C18 using a lipid‐compatible water cluster, and excludes longer FAs using a chain‐length‐limiting water cluster. These mechanisms could help us gain a general understanding of how proteins recognize diverse lipids with different chain lengths. 相似文献
1000.
Gas/solid chemistry in the upper, dilute region of a circulating fluidised bed combustor (CFBC) riser is addressed. The limitations
of turbulent mixing are illustrated by the example of the heterogeneous NO/CO/char reaction, relevant in CFB combustion of
nitrogen-containing solid fuels. The mass transfer of the gaseous reactants to the char surface is determined, and how the
conversion is influenced by the degree of mixing of the multiphase system by turbulent dispersion. Particle/turbulence interactions
are taken into account by a (Lagrangian) frequency spectrum of velocity fluctuations, which determine the dispersion of the
char particles described here with the Tchen–Hinze model. Chars from solid fuels characterised by fuel ratio (FR) ranging
from 0.1 (wood) via 0.5 (peat) and 1 (coal A) to 2 (coal B) were considered. The effective rate of the NO/CO/char reaction
is determined as a function of the size and type of the char particle, temperature, particle concentration, reactor dimensions
and fluidization velocity, at atmospheric pressure.
It was found that for this case the effective gas/solid conversion rate in the upper, dilute region of the riser is much lower
than the gas/solid chemistry, mainly due to mass transfer limitations for char particles with sizes of typically 300 μm. The
concentration of NO at the char particle surface is only a few % of that in the bulk gas phase. Strong influences were found
for particle size and temperature, whilst the fluidisation velocity and the reactor size have only a small influence. It is
concluded that for a typical CFB riser, for particles larger than approx. 20 μm, mass transfer has a stronger influence on
the heterogeneous NO/CO/char reduction mechanism than the ``unmixedness' due to particle eddy dispersion limitations. It
is recommended that this or a similar approach to turbulent dispersive mixing is implemented in CFD codes when these are used
for boiler and furnace calculations.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献