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151.
152.
Hyeonbin Ha Youngik Kim Dopil Kim Jihyun Lee Yoodae Song Suyeon Kim Prof. Dr. Myung Hwan Park Prof. Dr. Youngjo Kim Hyungjun Kim Prof. Minyoung Yoon Prof. Dr. Min Kim 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(63):14414-14420
The effect of metal on the degree of flexibility upon evacuation of metal–organic frameworks (MOFs) has been revealed with positional control of the organic functionalities. Although Co-, Cu-, and Zn-based DMOFs (DMOF = DABCO MOF, DABCO = 1,4-diazabicyclo[2.2.2]octane) with ortho-ligands (2,3-NH2Cl) have frameworks that are inflexible upon evacuation, MOFs with para-ligands (2,5-NH2Cl) showed different N2 uptake amounts after evacuation by metal exchange. Considering that the structural analyses were not fully sufficiently different to explain the drastic changes in N2 adsorption after evacuation, quantum chemical simulation was explored. A new index (η) was defined to quantify the regularity around the metal based on differences in the oxygen-metal-oxygen angles. Within 2,5-NH2Cl, the η value becomes larger as the metal are varied from Co to Zn. A large η value means that the structures around the metal center are less ordered. These results can be used to explain flexibility changes upon evacuation by altering the metal cation in this regioisomeric system. 相似文献
153.
154.
Lee N Cho HR Oh MH Lee SH Kim K Kim BH Shin K Ahn TY Choi JW Kim YW Choi SH Hyeon T 《Journal of the American Chemical Society》2012,134(25):10309-10312
Multimodal imaging is highly desirable for accurate diagnosis because it can provide complementary information from each imaging modality. In this study, a sol-gel reaction of tantalum(V) ethoxide in a microemulsion containing Fe(3)O(4) nanoparticles (NPs) was used to synthesize multifunctional Fe(3)O(4)/TaO(x) core/shell NPs, which were biocompatible and exhibited a prolonged circulation time. When the NPs were intravenously injected, the tumor-associated vessel was observed using computed tomography (CT), and magnetic resonance imaging (MRI) revealed the high and low vascular regions of the tumor. 相似文献
155.
Dae-Woo Jeon Seung-Jae Lee Tak Jeong Jong Hyeob Baek Jae-Woo Park Lee-Woon Jang Myoung Kim In-Hwan Lee Jin-Woo Ju 《Journal of Crystal Growth》2012,338(1):134-138
Chemical lift-off of (11–22) semipolar GaN using triangular cavities was investigated. The (11–22) semipolar GaN was grown using epitaxial lateral overgrowth by metal-organic chemical vapor deposition on m-plane sapphire, in such a way as to keep N terminated surface of c-plane GaN exposed in the cavities. After regrowing 300 μm thick (11–22) semipolar GaN by hydride vapor phase epitaxy for a free-standing (11–22) semipolar GaN substrate, the triangular cavities of the templates were chemically etched in molten KOH. The (000-2) plane in the triangular cavities can be etched in the [0002] direction with the high lateral etching rate of 196 μm/min. The resulting free-standing (11–22) semipolar GaN substrate was confirmed to be strain-free by the Raman analysis. 相似文献
156.
The potential for long-term operation of a lithium-oxygen battery using a non-carbonate-based electrolyte 总被引:1,自引:0,他引:1
HD Lim KY Park H Gwon J Hong H Kim K Kang 《Chemical communications (Cambridge, England)》2012,48(67):8374-8376
Herein we demonstrate the feasibility of extended cycle operation of a Li-O(2) battery by simple control of the discharge/charge protocol. By avoiding electrolyte decomposition and the deep discharge state of the air electrode, we were able to construct a Li-O(2) cell capable of efficiently cycling over 50 times with high energy density. 相似文献
157.
Tae Kyu Shim Myoung Hee Lee Doseok Kim Hyun Sung Kim Kyung Byung Yoon 《Journal of fluorescence》2012,22(6):1475-1482
Fluorescence characteristics of hemicyanine dye molecules isolated from neighboring molecules and strongly restricted inside nanosized pores of zeolite (silicalite-1) crystal were investigated. For samples in which the molecules were sufficiently far away from the others, the fluorescence decay lifetime of the molecules was about 2.2?ns. As the intermolecular distance was reduced, the steady-state fluorescence peak shifted toward the longer wavelength and the fluorescence efficiency decreased markedly. The fluorescence decay lifetime also decreased to 0.8?ns for a sample with the smallest intermolecular distance of 2.1?nm. These results were explained in terms of a dipole-dipole interaction between pairs of dye molecules. From the relation between the intermolecular distances and the fluorescence decay lifetimes of the molecules, the radius of energy transfer of hemicyanine donor-acceptor pair in zeolite matrix was determined to be 2.2?nm, in fair agreement with the calculated F?rster radius between dye molecules of the same species. 相似文献
158.
Myoung Hee YunJunghoon Lee Shinuk Cho Changduk Yang Jin Young Kim 《Current Applied Physics》2012,12(2):531-533
We have investigated the bifunctional properties using ambipolar low band gap conjugated copolymer in organic bulk-heterojunction (BHJ) solar cells. Ambipolar copolymer, poly[3,6-dithien-2-yl-2,5-di(2-decyltetradecanyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-5′,5′’-diyl-alt-benzo-2,1,3-thiadiazol-4,7-diyl] (PDTDPP-alt-BTZ), successfully works as the bifunctional material acting as both donor or acceptor. However, because of fast recombination nature and broken charge balance of hole and electron, solar cell performances were significantly limited. The results indicate that having distinct role of each component might be better for the high performance BHJ solar cells rather than bifunctional property based on good charge transport properties of both hole and electrons. 相似文献
159.
NoSoung Myoung Vladimir V. Fedorov Sergey B. Mirov Lowell E. Wenger 《Journal of luminescence》2012,132(3):600-606
Concentration dependences of the mid-IR kinetic of luminescence at 5E?5T2 transition in Fe:ZnSe and Fe:ZnS laser samples were studied in 14–300 K temperature ranges. Radiation lifetime in Fe:ZnSe samples measured using low doped samples with iron concentration 0.1×1018 cm?3 was estimated to be 57 μs. The magnetic susceptibility for higher doped (CFe=38 and 112×1018 cm?3) Fe:ZnSe samples was found to consist of a paramagnetic Curie–Weiss behavior arising from the weakly interacting Fe2+ ions and a diamagnetic ZnSe contribution plus a temperature-independent, field-dependent contribution possibly arising from very small amounts of aggregated Fe. 相似文献
160.
Moon D Kang S Park J Lee K John RP Won H Seong GH Kim YS Kim GH Rhee H Lah MS 《Journal of the American Chemical Society》2006,128(11):3530-3531
The face-driven corner-linked truncated octahedral nanocages, [Pd6L8]12+ (1, L1 = N,N',N' '-tris(3-pyridinyl)-1,3,5-benzenetricarboxamide; 2, L2 = N,N',N' '-tris(4-pyridinylmethyl)-1,3,5-benzenetricarboxamide), were prepared with eight C3-symmetric tridentate ligands and six square planar tetratopic palladium(II) ions. The combination of the nitrogen donor atom at a approximately 120 degrees kink position of the carboxamido pyridinyl group and the tilted pyridyl versus the facial plane of the ligands can provide the needed curvature for the formation of octahedral cages. The nitrogen atoms can coordinate to the square planar palladium(II) ions to form kinks with approximately 120 degrees angles at the C4-symmetric square planar corners of the truncated octahedron. Depending on the conformation of the ligand, L1, two different truncated octahedral cages of around 2.4 nm in diameters were formed. The major form of 1 with syn-conformational ligands has a cavity volume of approximately 1600 A3. The cage has 12 ports (3.4 x 3.5 A2) at all edges of the octahedron. The minor form of cage 1 with anti-conformational ligands has a slightly increased cavity volume ( approximately 1900 A3) and port size (3.3 x 8.0 A2). The insertion of a methylene group in L2 has not only increased the cavity volume of 2 to approximately 2200 A3 but also enlarged the port size to 4.1 x 8.0 A2. However, an atomic force microscopy (AFM) study of cage 2 showed that the cages had a height of 1.8 +/- 0.1 nm. This value is about 30% smaller than the calculated size of 2.6 nm from the crystal structure. This tip-induced decrease in height in cage 2 suggests the nonrigidity of cage 2. 相似文献