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941.
Katrine Qvortrup Michael xman Petersen Tue Hassenkam Mogens Brndsted Nielsen 《Tetrahedron letters》2009,50(40):5613-5616
A new tetrathiafulvalene (TTF)–perylene diimide (PDI) conjugate is prepared from an azide-functionalized TTF and an acetylenic PDI employing a Cu(I)-catalyzed Huisgen-Meldal-Sharpless reaction (‘click chemistry’). Thus, the TTF donor and PDI acceptor units are linked together by a 1,2,3-triazole unit. The molecules are found to assemble on a mica surface, forming fibrilar structures. 相似文献
942.
Chang Heon Lee Kih Soo Joe Won Ho Kim Euo Chang Jung Kwang Yong Jee 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(2):361-370
A sequential separation procedure has been developed for the determination of transuranic elements and fission products in
uranium metal ingot samples from an electrolytic reduction process for a metallization of uranium dioxide to uranium metal
in a medium of LiCl-Li2O molten salt at 650 °C. Pu, Np and U were separated using anion-exchange and tri-n-butylphosphate (TBP) extraction chromatography.
Cs, Sr, Ba, Ce, Pr, Nd, Sm, Eu, Gd, Zr and Mo were separated in several groups from Am and Cm using TBP and di(2-ethylhexyl)phosphoric
acid (HDEHP) extraction chromatography. Effect of Fe, Ni, Cr and Mg, which were corrosion products formed through the process,
on the separation of the analytes was investigated in detail. The validity of the separation procedure was evaluated by measuring
the recovery of the stable metals and 239Pu, 237Np, 241Am and 244Cm added to a synthetic uranium metal ingot dissolved solution. 相似文献
943.
The mechanical properties, morphologies, and gas barriers of hybrid films of cellulose with two different organoclays are
compared. Dodecyltriphenyl-phosphonium-mica (C12PPh-mica) and hexadecyl-mica (C16-mica) were used as reinforcing fillers in the fabrication of the cellulose hybrid films. The cellulose hybrid films were
synthesized from N-methyl-morpholine-N-oxide (NMMO) solutions with the two organo-micas, and solvent-cast at room temperature under vacuum, yielding 15–20 μm thick
films of cellulose hybrids with various clay contents. We found that the addition of only a small amount of organoclay is
sufficient to improve the mechanical properties and gas barriers of the cellulose hybrid films. Even polymers with low organoclay
contents (1–7 wt %) were found to exhibit much higher strength and modulus values than pure cellulose. The addition of C12PPh-mica was more effective than that of C16-mica with regards to the initial tensile modulus, whereas the addition of C16-mica was more effective than that of C12PPh-mica with regards to the gas barrier of the cellulose matrix. The intercalations of the polymer chains in the clays were
examined with wide-angle X-ray diffraction (XRD) and electron microscopy (SEM and TEM). 相似文献
944.
945.
Ye Ji Kim Sun Min Kim Eun Jin Cho Hideo Hosono Jung Woon Yang Sung Wng Kim 《Chemical science》2015,6(6):3577-3581
A simple and highly efficient transfer hydrogenation of alkynes and alkenes by using a two-dimensional electride, dicalcium nitride ([Ca2N]+·e–), as an electron transfer agent is disclosed. Excellent yields in the transformation are attributed to the remarkable electron transfer efficiency in the electride-mediated reactions. It is clarified that an effective discharge of electrons from the [Ca2N]+·e– electride in alcoholic solvents is achieved by the decomposition of the electride via alcoholysis and the generation of ammonia and Ca(OiPr)2. We found that the choice of solvent was crucial for enhancing the electron transfer efficiency, and a maximum efficiency of 80% was achieved by using a DMF mixed isopropanol co-solvent system. This is the highest value reported to date among single electron transfer agents in the reduction of C–C multiple bonds. The observed reactivity and efficiency establish that electrides with a high density of anionic electrons can readily participate in the reduction of organic functional groups. 相似文献
946.
Yonghwi Kim Tao Yang Gyeongwon Yun Mohammad Bagher Ghasemian Jaehyoung Koo Eunsung Lee Sung June Cho Kimoon Kim 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(45):13471-13476
A new approach to the synthesis of hierarchical micro‐ and mesoporous MOFs from microporous MOFs involves a simple hydrolytic post‐synthetic procedure. As a proof of concept, a new microporous MOF, POST‐66(Y), was synthesized and its transformation into a hierarchical micro‐ and mesoporous MOF by water treatment was studied. This method produced mesopores in the range of 3 to 20 nm in the MOF while maintaining the original microporous structure, at least in part. The degree of micro‐ and mesoporosity can be controlled by adjusting the time and temperature of hydrolysis. The resulting hierarchical porous MOF, POST‐66(Y)‐wt, can be utilized to encapsulate nanometer‐sized guests such as proteins, and the enhanced stability and recyclability of an encapsulated enzyme is demonstrated. 相似文献
947.
Félidj N Truong SL Aubard J Lévi G Krenn JR Hohenau A Leitner A Aussenegg FR 《The Journal of chemical physics》2004,120(15):7141-7146
Lithographically designed two-dimensional arrays consisting of gold nanoparticles deposited on a smooth gold film are used as substrate to examine the SERS effect of the trans-1,2-bis (4-pyridyl) ethylene molecule. These arrays display two plasmon bands instead of the single one observed for the same arrays of particles but deposited on indium tin oxide coated glass. Laser excitation within the short wavelength band does not bring about any SERS spectrum, while excitation within the long wavelength band yields SERS spectra with a gain per molecule rising up to 10(8). The simultaneous investigation of extinction and Raman spectra of arrays exhibiting various topography parameters enables us to suggest an interpretation for both the occurrence of the two plasmon resonances and for the high Raman enhancement. We suggest to assign the short wavelength band to a plasmon wave propagating at the gold glass interface and the long wavelength one to an air/gold surface plasmon mode modified by particle-particle interaction. 相似文献
948.
Adams CM Kjeldsen F Zubarev RA Budnik BA Haselmann KF 《Journal of the American Society for Mass Spectrometry》2004,15(7):1087-1098
First results are reported on the application of ECD in analysis of 2+ and 3+ ions of stereoisomers of Trp-cage (NLYIQWLKDGGPSSGRPPPS), the smallest and fastest-folding protein, which exhibits a tightly folded tertiary structure in solution. The chiral recognition based on the ratios of the abundances of z(18) and z(19) fragments in ECD of 2+ ions was excellent even for a single amino acid (Tyr) D-substitution (R(chiral) = 8.6). The chiral effect decreased with an increase of temperature at the electrospray ion source, as well as at a higher degree of ionization, 3+ ions (R(chiral) = 1.5). A general approach is suggested for charge localization in n+ ions by analysis of ECD mass spectra of (n + 1)+ ions. Application of this approach to 3+ Trp-cage ions revealed the protonation probability order in 2+ ions: Arg(16) > Gln(5) > approximately N-terminus. The ECD results for native form of the 2+ ions favor the preservation of the solution-phase tertiary structure, and chiral recognition through the interaction between the charges and the neutral bond network. Conversely, ECD of 3+ ions supports the dominance of ionic hydrogen bonding which determines a different gas-phase structure than found in solution. Vibrational activation of 2+ ions indicated greater stability of the native form, but the fragmentation patterns did not provide stereoisomer differentiation, thus underlying the special position of ECD among other MS/MS fragmentation techniques. Further ECD studies should yield more structural information as well as quantitative single-amino acid D/L content measurements in proteins. 相似文献
949.
A simple and extractionless HPLC method using fluorescence detection was developed for the determination of rosiglitazone in human plasma. After deproteinization using perchloric acid the plasma samples were directly injected onto the HPLC system. The mobile phase was composed of acetonitrile (52%) and 20 mm ammonium acetate (48%, pH 7.5), and analysis was run at a flow rate of 0.2 mL/min with the detector operating at 247 nm for excitation wavelength and at 367 nm for emission wavelength, respectively. The method has a mean recovery of 97%, while the intra-day and inter-day precisions were all less than 7%. This method is simple, specific, sensitive and requires only a small plasma volume with short analytical time, and is suitable for the determination of plasma rosiglitazone in routine measurements for pharmacokinetic studies. 相似文献
950.
The vacuum-ultraviolet (VUV) pulsed-field ionization-photoelectron (VUV-PFI-PE) spectra of trans-1-bromopropene (trans-CH(3)CH[Double Bond]CHBr) and cis-1-bromopropene (cis-CH(3)CH[Double Bond]CHBr) have been measured in the energy region of 74 720-76 840 cm(-1). The simulation of fine structures observed in the origin VUV-PFI-PE vibrational bands of these molecules has provided the ionization energies (IEs) of trans-1-bromopropene and cis-1-bromopropene to be 74 779.3+/-2.0 cm(-1) (9.2715+/-0.0002 eV) and 75 140.2+/-2.0 cm(-1) (9.3162+/-0.0002 eV), respectively. The vibrational bands resolved in these VUV-PFI-PE spectra at energies 0-1700 cm(-1) above the IEs of trans-1-bromopropene and cis-1-bromopropene have been assigned based on theoretical vibrational frequencies and calculated Franck-Condon factors for the ionization transitions. 相似文献