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排序方式: 共有271条查询结果,搜索用时 15 毫秒
51.
52.
Taki M Desaki M Ojida A Iyoshi S Hirayama T Hamachi I Yamamoto Y 《Journal of the American Chemical Society》2008,130(38):12564-12565
We described here a coumarin-based dual-excitation ratiometric probe for cadmium, CadMQ. This fluorescence sensor has high quantum yields of 0.59 and 0.70 in the metal-free and Cd2+-bound forms, respectively, and has a dissociation constant of 0.16 nM for Cd2+. CadMQ is cell permeable and locates within the acidic compartments of the cells. We further show that CadMQ is a useful tool to ratiometrically probe the change in the intracellular Cd2+ levels with the use of two excited wavelengths. 相似文献
53.
54.
Shinobu Itoh Masayasu Taki Shigehisa Takayama Shigenori Nagatomo Teizo Kitagawa Norio Sakurada Ryuichi Arakawa Shunichi Fukuzumi 《Angewandte Chemie (International ed. in English)》1999,38(18):2774-2776
Profound insights into the catalytic mechanism of galactose oxidase (GO) are offered by new models of the active form of the metalloenzyme. The important role of the CuII center in the oxidation of benzyl alcohol to benzaldehyde by the CuII–phenoxyl radical complex of ligand 1 has been revealed by comparison with the reactivity of the corresponding ZnII–phenoxyl radical complex; py=2-pyridyl. 相似文献
55.
N. Tate W. Nomura T. Yatsui M. Naruse M. Ohtsu 《Applied physics. B, Lasers and optics》2009,96(1):1-4
Optical near-field interactions exhibit hierarchical responses in the nanometer scale allowing unique functions in nanophotonic
systems. Such hierarchical properties in optical near-fields originate various physical entities in the nanometer scale. Engineering
nanomaterial compositions, while maintaining geometrically equivalent conditions, leads to characteristic hierarchical responses.
We experimentally demonstrate such material-dependent optical near-field hierarchy using core–shell-type nanostructures composed
of gold and silver. 相似文献
56.
We observed a quantum confinement effect in vertically well-aligned ultrafine ZnO nanorods using polarized excitation photoluminescence
measurements. Room-temperature and low-temperature photoluminescence spectra revealed that free excitons were confined in
the nanorods. The magnitude of the energy shift due to the quantum confinement in the ultrafine ZnO nanorods was 6 meV at
room temperature, which corresponded to the luminescence from ZnO nanorods 12.8 nm in diameter. The diameter estimated from
the spectra was comparable to the value measured from SEM images. 相似文献
57.
Cho J Furutachi H Fujinami S Tosha T Ohtsu H Ikeda O Suzuki A Nomura M Uruga T Tanida H Kawai T Tanaka K Kitagawa T Suzuki M 《Inorganic chemistry》2006,45(7):2873-2885
The reaction of [Ni2(OH)2(Me2-tpa)2]2+ (1) (Me2-tpa = bis(6-methyl-2-pyridylmethyl)(2-pyridylmethyl)amine) with H2O2 causes oxidation of a methylene group on the Me2-tpa ligand to give an N-dealkylated ligand and oxidation of a methyl group to afford a ligand-based carboxylate and an alkoxide as the final oxidation products. A series of sequential reaction intermediates produced in the oxidation pathways, a bis(mu-oxo)dinickel(III) ([Ni2(O)2(Me2-tpa)2]2+ (2)), a bis(mu-superoxo)dinickel(II) ([Ni2(O2)2(Me2-tpa)2]2+ (3)), a (mu-hydroxo)(mu-alkylperoxo)dinickel(II) ([Ni2(OH)(Me2-tpa)(Me-tpa-CH2OO)]2+ (4)), and a bis(mu-alkylperoxo)dinickel(II) ([Ni2(Me-tpa-CH2OO)2]2+ (5)), was isolated and characterized by various physicochemical measurements including X-ray crystallography, and their oxidation pathways were investigated. Reaction of 1 with H2O2 in methanol at -40 degrees C generates 2, which is extremely reactive with H2O2, producing 3. Complex 2 was isolated only from disproportionation of the superoxo ligands in 3 in the absence of H2O2 at -40 degrees C. Thermal decomposition of 2 under N2 generated an N-dealkylated ligand Me-dpa ((6-methyl-2-pyridylmethyl)(2-pyridylmethyl)amine) and a ligand-coupling dimer (Me-tpa-CH2)2. The formation of (Me-tpa-CH2)2 suggests that a ligand-based radical Me-tpa-CH2* is generated as a reaction intermediate, probably produced by H-atom abstraction by the oxo group. An isotope-labeling experiment revealed that intramolecular coupling occurs for the formation of the coupling dimer. The results indicate that the rebound of oxygen to Me-tpa-CH2* is slower than that observed for various high-valence bis(mu-oxo)dimetal complexes. In contrast, the decomposition of 2 and 3 in the presence of O2 gave carboxylate and alkoxide ligands, respectively (Me-tpa-COO- and Me-tpa-CH2O-), instead of (Me-tpa-CH2)2, indicating that the reaction of Me-tpa-CH2* with O2 is faster than the coupling of Me-tpa-CH2* to generate ligand-based peroxyl radical Me-tpa-CH2OO*. Although there is a possibility that the Me-tpa-CH2OO* species could undergo various reactions, one of the possible reactive intermediates, 4, was isolated from the decomposition of 3 under O2 at -20 degrees C. The alkylperoxo ligands in 4 and 5 can be converted to a ligand-based aldehyde by either homolysis or heterolysis of the O-O bond, and disproportionation of the aldehyde gives a carboxylate and an alkoxide via the Cannizzaro reaction. 相似文献
58.
We study the effects of Lorentz non-invariance on the physical pion velocity at the critical temperature Tc in an effective theory of hidden local symmetry (HLS) with the “vector manifestation” fixed point. We match at a “matching scale” ΛM the axial-vector current correlator in the HLS with the one in the operator product expansion for QCD, and present the matching condition to determine the bare pion velocity. We find that the physical pion velocity, which is found to be one at T=Tc when starting from the Lorentz invariant bare HLS, remains close to one with the Lorentz non-invariance, vπ(Tc)=0.83–0.99. This result is quite similar to the pion velocity in dense matter. 相似文献
59.
Akihiko Ohtsu 《Optics Communications》2010,283(20):3831-3837
The author investigated second-harmonic (SH) wave patterns generated by focused vortex beams with radial and azimuthal polarizations. Expressions for electric field components near the focus through a dielectric interface were obtained based on vector diffraction theory. Furthermore, the (110) and (001) planes of a crystal classified in the symmetry group 4?3m were considered as second order nonlinear optical medium to analyze nonlinear polarization and the intensity distributions of the SH wave in the far-field were simulated for topological charge m = 1 and 2. Numerical simulations indicated that the intensity and emission pattern of the SH wave depended principally on the electric field component and distribution near the focus. In particular, for the (001) plane, the intensity of the SH wave was strongly correlated with the existence of a longitudinal electric field. 相似文献
60.
Naoya Tate Yang Liu Tadashi Kawazoe Makoto Naruse Takashi Yatsui Motoichi Ohtsu 《Applied physics. B, Lasers and optics》2013,110(3):293-297
Although recent advances in fabrication technologies have allowed the realization of highly accurate nanometric devices and systems, most approaches still lack uniformity and mass-production capability sufficient for practical use. We have previously demonstrated a novel technique for autonomously coupling heterogeneous quantum dots to induce particular optical responses based on a simple phonon-assisted photocuring method in which a mixture of quantum dots and photocurable polymer is irradiated with light. The cured polymer sequentially encapsulates coupled quantum dots, forming what we call a nanophotonic droplet. Recently, we found that each quantum dot in the mixture is preferably coupled with other quantum dots of similar size due to a size resonance effect of the optical near-field interactions between them. Moreover, every nanophotonic droplet is likely to contain the same number of coupled quantum dots. In this paper, we describe the basic mechanisms of autonomously fabricating nanophotonic droplets, and we examine the size- and number-selectivity of the quantum dots during their coupling process. The results from experiments show the uniformity of the optical properties of mass-produced nanophotonic droplets, revealed by emission from the contained coupled quantum dots, due to the fundamental characteristics of our method. 相似文献