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151.
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153.
Lee D Choe YJ Lee M Jeong DH Paik SR 《Langmuir : the ACS journal of surfaces and colloids》2011,27(21):12782-12787
The enhancement of weak Raman signals has been challenged to obtain high-quality signals of surface-enhanced Raman scattering (SERS). By employing the Parkinson's disease-related protein of α-synuclein, we introduce SERS-active gold nanoparticles (AuNPs) individually isolated with an ultrathin α-synuclein shell and their 2-D array into a tightly packed monolayer on a glass support, which permits a quantitative SERS measurement of phthalocyanine tetrasulfonate (PcTS), a chemical ligand of the pathological protein. Subsequently, the PcTS-bound SERS substrate was also shown to be capable of discriminating two biologically important metal ions of iron and copper by detecting copper ion to the sub-ppm level in a highly selective manner via the in situ chemical reaction of metal chelation to PcTS. The strategy of using the protein-based 2-D AuNP SERS platform, therefore, could be further developed into a custom-made protein-based biosensor system for the detection of not only specific chemical/biological ligands of the immobilized coat proteins but also their biochemical reactivities. 相似文献
154.
The physical properties and phase transition mechanisms of MCr(SO4)2·12H2O (M=Rb and Cs) single crystals have been investigated. The phase transition temperatures, NMR spectra, and the spin-lattice relaxation times T1 of the 87Rb and 133Cs nuclei in the two crystals were determined using DSC and FT NMR spectroscopy. The resonance lines and relaxation times of the 87Rb and 133Cs nuclei undergo significant changes at the phase transition temperatures. The sudden changes in the splitting of the Rb and Cs resonance lines are attributed to changes in the local symmetry of their sites, and the changes in the temperature dependences of T1 are related to variations in the symmetry of the octahedra of water molecules surrounding Rb+ and Cs+. We also compared these 87Rb and 133Cs NMR results with those obtained for the trivalent cations Cr and Al in MCr(SO4)2·12H2O and MAl(SO4)2·12H2O crystals. 相似文献
155.
Gillett-Kunnath MM Paik JI Jensen SM Taylor JD Sevov SC 《Inorganic chemistry》2011,50(22):11695-11701
Ni-centered deltahedral Sn(9) clusters with a charge of 4-, i.e., [Ni@Sn(9)](4-), were extracted in ethylenediamine in high yield directly from intermetallic precursors with the nominal composition "K(4)Sn(9)Ni(3)". The new endohedral clusters were crystallized and structurally characterized in K[K(18-crown-6)](3)[Ni@Sn(9)]·3benzene (1a, triclinic, P1?, a = 10.2754(5) ?, b = 19.5442(9) ?, and c = 20.5576(13) ?, α = 73.927(3)°, β = 79.838(4)°, and γ = 84.389(3)°, V = 3899.6(4) ?(3), Z = 2) and K[K(2,2,2-crypt)](3)[Ni@Sn(9)] (1b, triclinic, P1, a = 15.8028(8) ?, b = 16.21350(9) ?, and c = 20.1760(12) ?, α = 98.71040(10)°, β = 104.4690(10)°, and γ = 118.3890(10)°, V = 4181.5(4) ?(3), Z = 2). The alternative method of a post-synthetic insertion of a Ni atom in empty Sn(9) clusters by a reaction with Ni(cod)(2) predominantly produces the more-oxidized clusters with a charge of 3-, i.e., the recently reported [Ni@Sn(9)](3-). Nonetheless, using substoichiometric amounts of 18-crown-6 as a cation sequestering agent, we also have been able to isolate the 4- clusters as a minor phase from such reactions. They were structurally characterized in K[K(en)][K(18-crown-6)](2)[Ni@Sn(9)]·0.5en (2, monoclinic, P2(1)/n, a = 10.4153(5) ?, b = 25.6788(11) ?, and c = 20.6630(9) ?, β = 102.530(2)°, V = 5394.7(4) ?(3), Z = 2). The ability of the Ni-centered clusters to exist with both 3- and 4- charges parallels the same ability of the empty clusters and is very promising for similarly rich chemistry involving electron transfer and flexible "oxidation states". We also report the synthesis and characterization of the endohedral heteroatomic dimer [{Ni@Sn(8)(μ-Ge)(1/2)}(2)](4-) composed of two [Ni@(Sn(8)Ge)]-clusters fused at the Ge-vertex. The dimer was synthesized by reacting an ethylenediamine solution of a ternary precursor with the nominal composition "K(4)Ge(4.5)Sn(4.5)", which is known to produce heteroatomic Ge(9-x)Sn(x) clusters, with Ni(cod)(2). It is isostructural with the reported [{Ni@Sn(8)(μ-Sn)(1/2)}(2)](4-) and is structurally characterized in [K-(2,2,2-crypt)](4)[{Ni@Sn(8)(μ-Ge)(1/2)}(2)]·2en (3, monoclinic, C2/c, a = 30.636(2) ?, b = 16.5548(12) ?, and c = 28.872(2) ?, β = 121.2140(10)°, V = 12523.5(15) ?(3), Z = 4). 相似文献
156.
157.
Younkee Paik Barbara Poliks Cristian C. Rusa Alan E. Tonelli Jacob Schaefer 《Journal of Polymer Science.Polymer Physics》2007,45(11):1271-1282
Molecular motions of single polycarbonate (PC) chains threaded into crystalline γ‐cyclodextrin (γ‐CD) channels were examined using solid‐state 13C NMR and molecular dynamics simulations. The location of PC within the channels was confirmed by spin diffusion from a PC 13C label to natural‐abundance 13C of the γ‐CD. Rotor‐encoded longitudinal magnetization (RELM) (under 7‐kHz magic‐angle sample‐spinning conditions) was combined with multiple‐pulse 1H‐1H dipolar decoupling to detect large‐amplitude phenyl‐ring motion in both bulk PC and polycarbonate γ‐cyclodextrin inclusion compound (PC‐γ‐CD). The RELM results indicate that the phenyl rings in PC‐γ‐CD undergo 180° flips faster than 10 kHz just as in bulk PC. The molecular dynamics simulations show that the frequency of the phenyl‐ring flips depends on the cooperative motions of PC atoms and neighboring atoms of the γ‐CD channel. The distribution of protonated aromatic‐carbon laboratory and rotating‐frame 13C spin‐lattice relaxation rates for bulk PC and PC‐γ‐CD are similar but not identical. The distributions for both systems arise from site heterogeneities. For bulk PC, the heterogeneity is attributed to variations in local chain packing, and for PC‐γ‐CD the heterogeneity arises from variations in the location of the PC phenyl rings in the γ‐CD channel. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1271–1282, 2007 相似文献
158.
Dr. Lin‐Hua Xie Prof. Myunghyun Paik Suh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(35):11590-11597
A new porous organic polymer, SNU‐C1 , incorporating two different CO2‐attracting groups, namely, carboxy and triazole groups, has been synthesized. By activating SNU‐C1 with two different methods, vacuum drying and supercritical‐CO2 treatment, the guest‐free phases, SNU‐C1‐va and SNU‐C1‐sca , respectively, were obtained. Brunauer–Emmett–Teller (BET) surface areas of SNU‐C1‐va and SNU‐C1‐sca are 595 and 830 m2g?1, respectively, as estimated by the N2‐adsorption isotherms at 77 K. At 298 K and 1 atm, SNU‐C1‐va and SNU‐C1‐sca show high CO2 uptakes, 2.31 mmol g?1 and 3.14 mmol g?1, respectively, the high level being due to the presence of abundant polar groups (carboxy and triazole) exposed on the pore surfaces. Five separation parameters for flue gas and landfill gas in vacuum‐swing adsorption were calculated from single‐component gas‐sorption isotherms by using the ideal adsorbed solution theory (IAST). The data reveal excellent CO2‐separation abilities of SNU‐C1‐va and SNU‐C1‐sca , namely high CO2‐uptake capacity, high selectivity, and high regenerability. The gas‐cycling experiments for the materials and the water‐treated samples, experiments that involved treating the samples with a CO2‐N2 gas mixture (15:85, v/v) followed by a pure N2 purge, further verified the high regenerability and water stability. The results suggest that these materials have great potential applications in CO2 separation. 相似文献
159.
Myung‐Ho Choi Hye Jeong Park Dae Ho Hong Prof. Myunghyun Paik Suh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(51):17432-17438
Two different 3D porous metal–organic frameworks, [Zn4O(NTN)2]?10 DMA?7 H2O ( SNU‐150 ) and [Zn5(NTN)4(DEF)2][NH2(C2H5)2]2?8 DEF?6 H2O ( SNU‐151 ), are synthesized from the same metal and organic building blocks but in different solvent systems, specifically, in the absence and the presence of a small amount of acid. SNU‐150 is a doubly interpenetrated neutral framework, whereas SNU‐151 is a non‐interpenetrated anionic framework containing diethylammonium cations in the pores. Comparisons of the N2, H2, CO2, and CH4 gas adsorption capacities as well as the CO2 adsorption selectivity over N2 and CH4 in desolvated SNU‐150′ (BET: 1852 m2 g?1) and SNU‐151′ (BET: 1563 m2 g?1) samples demonstrate that the charged framework is superior to the neutral framework for gas storage and gas separation, despite its smaller surface area and different framework structure. 相似文献
160.
Hydrogen Storage in a Potassium‐Ion‐Bound Metal–Organic Framework Incorporating Crown Ether Struts as Specific Cation Binding Sites 下载免费PDF全文
Dr. Dae‐Woon Lim Seung An Chyun Prof. Myunghyun Paik Suh 《Angewandte Chemie (International ed. in English)》2014,53(30):7819-7822
To develop a metal–organic framework (MOF) for hydrogen storage, SNU‐200 incorporating a 18‐crown‐6 ether moiety as a specific binding site for selected cations has been synthesized. SNU‐200 binds K+, NH4+, and methyl viologen(MV2+) through single‐crystal to single‐crystal transformations. It exhibits characteristic gas‐sorption properties depending on the bound cation. SNU‐200 activated with supercritical CO2 shows a higher isosteric heat (Qst) of H2 adsorption (7.70 kJ mol?1) than other zinc‐based MOFs. Among the cation inclusions, K+ is the best for enhancing the isosteric heat of the H2 adsorption (9.92 kJ mol?1) as a result of the accessible open metal sites on the K+ ion. 相似文献