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91.
Okazaki T Okubo S Nakanishi T Joung SK Saito T Otani M Okada S Bandow S Iijima S 《Journal of the American Chemical Society》2008,130(12):4122-4128
We report optical band gap modifications of single-walled carbon nanotubes upon C60 insertions by using photoluminescence and the corresponding excitation spectroscopy. The shifts in optical transition energies strongly depend on the tube diameter (dt) and the "2n + m" family type, which can be explained by the local strain and the hybridization between the nanotube states and the C60 molecular orbitals. The present results provide possible design rules for nanotube-based heterostructures having a specific type of electronic functionality. 相似文献
92.
Synthesis of monopyrenylalkylamine derivative 1 and its fluorescence behavior for Cu2+ in H2O/CH3CN (1:1, v/v) were investigated. Upon Cu2+ binding, 1, bearing a sulfonamide group, exhibited a marked excimer emission at 455 nm along with a weak monomer emission at 375 nm. The excimer emission, driven by formation of an intermolecular pyrenyl static excimer upon Cu2+ binding to the sulfonamide group, is rationalized by experimental and theoretical DFT calculation results. 相似文献
93.
A theoretical analysis of buoyancy-driven instability under transient basic fields is conducted in an initially quiescent,
fluid-saturated, horizontal porous layer. Darcy’s law is used to explain characteristics of fluid motion and the anisotropy
of permeability is considered. Under the Boussinesq approximation and the principle of exchange of stabilities, the stability
equations are derived by using the linear stability theory and the energy method. The linear stability equations are analyzed
numerically by using the frozen-time model and the linear amplification theory and the global stability limits are obtained
numerically from the energy method. For the various anisotropic ratios, the critical times are predicted as a function of
the Darcy–Rayleigh number and the critical Darcy–Rayleigh number is also obtained. The present predictions are compared each
another and with existing theoretical ones. 相似文献
94.
Hye Jin Kim Xiao-Jun Li Dong-Cheol Kim Tai Kyoung Kim Jae Hak Sohn Haeun Kwon Dongho Lee Youn-Chul Kim Joung Han Yim Hyuncheol Oh 《Molecules (Basel, Switzerland)》2021,26(18)
Chemical investigation of the Antarctic lichen-derived fungal strain Acremonium sp. SF-7394 yielded a new amphilectane-type diterpene, acrepseudoterin (1), and a new acorane-type sesquiterpene glycoside, isocordycepoloside A (2). In addition, three known fungal metabolites, (−)-ternatin (3), [D-Leu]-ternatin (4), and pseurotin A (5), were isolated from the EtOAc extract of the fungal strain. Their structures were mainly elucidated by analyzing their NMR and MS data. The absolute configuration of 1 was proposed by electronic circular dichroism calculations, and the absolute configuration of the sugar unit in 2 was determined by a chemical method. The inhibitory effects of the isolated compounds on protein tyrosine phosphatase 1B (PTP1B) were evaluated by enzymatic assays; results indicated that acrepseudoterin (1) and [D-Leu]-ternatin (4) dose-dependently inhibited the enzyme activity with IC50 values of 22.8 ± 1.1 μM and 14.8 ± 0.3 μM, respectively. Moreover, compound 1 was identified as a competitive inhibitor of PTP1B. 相似文献
95.
Dong Geun Jo Changeun Kim Sinjae Lee Sooyeon Yun Seewon Joung 《Molecules (Basel, Switzerland)》2022,27(5)
In this study, we describe the synthesis of cyclic N-acyl amidines from readily available N-heteroarenes. The synthetic methodology utilized the versatile N-silyl enamine intermediates from the hydrosilylation of N-heteroarenes for the [3 + 2] cycloaddition reaction step. We evaluated various acyl azides and selected an electronically activated acyl azide, thereby achieving a reasonable yield of cyclic N-acyl amidines. We analyzed the relationship between the reactivity of each step and the electronic nature of substrates using in situ nuclear magnetic resonance spectroscopy. In addition, we demonstrated gram-scale synthesis using the proposed methodology. 相似文献
96.
Joung Sook Hong Yong Kyung Kim Kyung Hyun Ahn Seung Jong Lee Chongyoup Kim 《Rheologica Acta》2007,46(4):469-478
We investigated the effect of organically modified nanoclay (organoclay) on immiscible polymer blends [polybutylene terephthalate
(PBT)/polyethylene (PE)] with a special focus on the role of clay as a compatibilizer. When organoclay (Nanofil 919; Sud-Chemie,
Inc.) is added to the blend, the clay first locates at the interface and then selectively locates in the PBT phase due to
its affinity with PBT. This results in effective size reduction and narrowed size distribution of the dispersed phase. However,
with a small amount of organoclay, it is observed that the clay locates at the interface regardless of its affinity for a
specific component to minimize the chemical potential. The interfacial tension change of the blend with the addition of organoclay
was quantitatively predicted from extensional force measurement. When the blend is subjected to an extension, the interfacial
tension functions as a resistance against drop deformation. When we added organoclay to the blend, the extensional force was
significantly reduced, which means that the contribution of the interfacial tension to the total force is reduced. For a 10/90
PBT/PE blend, the interfacial tension was reduced from 5.76 to 0.14 cN m−1 when 1 wt% of organoclay was added. This interfacial tension reduction arises from the localization of the organoclay at
the interface and its nonhomogeneous distribution along the interface, suppressing the coalescence between the droplets, which
is a role of a compatibilizer. Conclusively, the immiscible polymer blends can be compatibilized with organoclay. The organoclay
changes the blend morphology by interfacial tension reduction due to the localization of the organoclay at the interface and
by the viscosity ratio change due to the selective localization by its affinity to a specific component in the blend. 相似文献
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