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71.
Dr. Tomokazu Umeyama Junya Mihara Noriyasu Tezuka Prof. Dr. Yoshihiro Matano Kati Stranius Dr. Vladimir Chukharev Prof. Dr. Nikolai V. Tkachenko Prof. Dr. Helge Lemmetyinen Dr. Kei Noda Prof. Dr. Kazumi Matsushige Prof. Dr. Tetsuya Shishido Dr. Zheng Liu Kaori Hirose‐Takai Prof. Dr. Kazu Suenaga Prof. Dr. Hiroshi Imahori 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(14):4250-4257
Chemically converted graphene (CCG) covalently linked with porphyrins has been prepared by a Suzuki coupling reaction between iodophenyl‐functionalized CCG and porphyrin boronic ester. The covalently linked CCG–porphyrin composite was designed to possess a short, rigid phenylene spacer between the porphyrin and the CCG. The composite material formed stable dispersions in DMF and the structure was characterized by spectroscopic, thermal, and microscopic measurements. In steady‐state photoluminescence spectra, the emission from the porphyrin linked to the CCG was quenched strongly relative to that of the porphyrin reference. Fluorescence lifetime and femtosecond transient absorption measurements of the porphyrin‐linked CCG revealed a short‐lived porphyrin singlet excited state (38 ps) without yielding the porphyrin radical cation, thereby substantiating the occurrence of energy transfer from the porphyrin excited state to the CCG and subsequent rapid decay of the CCG excited state to the ground state. Consistently, the photocurrent action spectrum of a photoelectrochemical device with a SnO2 electrode coated with the porphyrin‐linked CCG exhibited no photocurrent response from the porphyrin absorption. The results obtained here provide deep insight into the interaction between graphenes and π‐conjugated systems in the excited and ground states. 相似文献
72.
A homocoupling reaction mechanism of bromobenzene mediated by the [Ni(cod)(bpy)] (cod = 1,5-cyclooctadiene; bpy = 2,2'-bipyridine) complex was investigated by means of in situ time-resolved X-ray absorption fine structure (XAFS) and factor analysis. A dimer intermediate [Ni(bpy)(Ph)Br](2) proposed in the previous studies by other groups is too dilute to observe with the XAFS technique; however, the structures and concentrations on the time course of a reactant [Ni(cod)(bpy)], an intermediate [Ni(bpy)(Ph)Br(dmf)(2)], and a byproduct [Ni(bpy)Br(2)(dmf)] during reaction are revealed by this combination. 相似文献
73.
74.
Y. Nakajima T. Shibauchi H. Shishido K. Behnia M. Hedo T. Matsumoto Y. Onuki Y. Matsuda 《Journal of Physics and Chemistry of Solids》2008,69(12):3261-3264
We observe several non-Fermi liquid behaviors in the normal-state transport properties of CeMIn5 (M: Rh and Co) under pressure at low temperatures: (1) The dc-resistivity shows T-linear dependence, ρxx∝T. (2) The magnitude of Hall coefficient |RH| increases rapidly with decreasing temperature, and reaches a value much larger than |1/ne| at low temperatures. (3) The magnetoresistance displays T- and H-dependence that strongly violate Kohler's rule, and is well scaled by the tangent of the Hall angle, . These non-Fermi liquid properties in the electron transport are remarkably pronounced when the AF fluctuations are enhanced in the vicinity of the quantum critical point. Since all of these salient features have been also reported for high-Tc cuprates, we infer that the non-Fermi liquid transport properties capture universal features of strongly correlated electron systems in the presence of strong antiferromagnetic fluctuations. 相似文献
75.
R. Okazaki H. Shishido M. Konczykowski Y. ōnuki 《Journal of Physics and Chemistry of Solids》2008,69(12):3208-3210
We report local magnetization measurements on the heavy fermion superconductor CeCoIn5 using a micro-Hall probe. Below a critical point T0 (), the local magnetization shows a clear jump at the superconducting transition temperatures for both H∥a and H∥c, indicating that the phase transition at the upper critical field Hc2 becomes a first-order phase transition. In addition, we observed an undershoot behavior of magnetization jump above (H∥c), which suggests a rapid change of textured superconducting structure with vortices and the nodal planes expected in the Fulde-Ferrell-Larkin-Ovchinnikov state. 相似文献
76.
Naofumi Ohtsu Masaoki Oku Akiko Nomura Takamasa Sugawara Toetsu Shishido Kazuaki Wagatsuma 《Applied Surface Science》2008,254(11):3288-3294
Initial oxidation of iron and manganese mono-silicides (FeSi and MnSi) surfaces was studied by X-ray photoelectron spectroscopy (XPS). Clean surfaces of these silicides were prepared by fracturing in an ultra high vacuum, and then the fractured surfaces were oxidized by exposing to high-purity oxygen at pressures up to 1.3 Pa. For the clean FeSi surface, positive chemical shifts of the Fe 2p3/2 and Si 2p peaks from elemental Fe and Si were 0.5 eV and 0.1 eV, respectively. For the clean MnSi surface, a negative chemical shift of the Si 2p peak from elemental Si was 0.1 eV. Iron on the FeSi surface was oxidized at an oxygen pressure of 1.3 Pa, whereas the silicon was oxidized under the pressure of 1.3 × 10−6 Pa, indicating that oxidation of silicon occurred prior to that of iron. Manganese and silicon on the MnSi were simultaneously oxidized in the range from 1.3 × 10−6 Pa to 1.3 × 10−3 Pa; however, over the pressure of 1.3 Pa, the oxidation of manganese occurs prior to that of silicon. These oxidation behaviors at low oxygen pressures were similar to those of the FeSi and MnSi fractured in air. 相似文献
77.
We have studied similarity rules of quasistatic minor hysteresis loops for Fe and Ni single crystals in the wide temperature range from 10 to 600 K. Two similarity rules of MR*/Ma*∼3/4 and WR*/WF*∼1/6, were found in a medium field range where irreversible movement of Bloch walls plays a crucial role for magnetization; Ma*, MR*, WF*, and WR* are magnetization, remanence, hysteresis loss, and remanence work of a minor hysteresis loop. The similarity rules hold true, being almost independent of kinds of ferromagnets, applied stress, and temperature. The origin was discussed from the viewpoint of pinning effects due to dislocations as well as eddy current effects which become predominant at low temperatures for samples with low dislocation density. 相似文献
78.
A novel tandem [2 + 2] cycloaddition-Dieckmann condensation via ynolate anions is described. Ynolate anions are useful for the formation of reactive beta-lactone enolates via a pathway not involving the enolization of the corresponding beta-lactones. The [2 + 2] cycloaddition of ynolate anions with delta- or gamma-keto esters, followed by Dieckmann condensation, gives bicyclic beta-lactones, which are easily decarboxylated to produce synthetically useful 2,3-disubstituted cyclopentenones and cyclohexenones in one pot. This tandem reaction was applied to a novel, one-pot synthesis of highly substituted naphthalenes. 相似文献
79.
Noriyuki Kuramoto Yuichi Shishido Katsutoshi Nagai 《Journal of polymer science. Part A, Polymer chemistry》1997,35(10):1967-1972
Thermosensitive and redox-active polymers were prepared by copolymerization of N-ethyl- or N,N-diethylacrylamides with vinylferrocene (VFc). LCST (lower critical solution temperature) of the aqueous copolymer solution was decreased by increasing the ferrocene content in the copolymer. The oxidation of ferrocene led to a significant increase in LCST due to the transition from hydrophobic to hydrophilic character of the ferrocene moiety in the copolymer. The ferrocene content in the copolymer increases with increasing differences between the LCST's of the oxidation and reduction states. The transition could be made reversible by redox reaction using L -ascorbic acid as an oxidant and cerium sulfate as a reductant. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1967–1972, 1997 相似文献
80.
Shinji Watanabe Osamu Shishido Miki Murata Yuzuru Masuda 《Macromolecular rapid communications》1998,19(1):75-77
Polymer microspheres with mercapto groups were synthesized by polycondensation of 1,6-dibromohexane and 1,3-propanedithiol in the presence of a polystyrene latex and a nonionic surfactant. The sulfur content of the obtained particles is comparable with the one calculated according to the feed ratio, which shows that the polycondensation proceeds quantitatively in the particles. A higher molar ratio of dithiol against dibromide used in the polycondensation results in microspheres with higher mercapto group content. 相似文献