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931.
Metal-enhanced fluorescence (MEF) of quantum dots (QDs) and its potential application in microarray-based immunoassays was investigated using silver nanoparticles (AgNPs) prepared by the in situ photoreduction of Ag+ inside a multilayer film consisting of poly(ethyleneimine) (PEI) and hyaluronic acid (HA). UV–Vis spectroscopy, X-ray diffraction, atomic force microscopy, scanning electron microscopy, and transmission electron microscopy confirmed the formation of well-dispersed AgNPs within the multilayer films, the thickness and the amount of which depended on the number of HA layers. Using AgNPs-containing hybrid multilayered films, it was possible to observe the MEF effect of adsorbed QDs, which could be tuned by the thickness of interlayer spacer film prepared of the layer-by-layer assembly of PEI and poly(styrene sulfonate). When the MEF-inducing hybrid film was used as a platform for immunoassay, a significant improvement in the fluorescence signal and sensitivity of the biosensing were observed in the presence of AgNPs in comparison with films that did not contain the nanoparticles. 相似文献
932.
Desolvation and Dehydrogenation of Solvated Magnesium Salts of Dodecahydrododecaborate: Relationship between Structure and Thermal Decomposition
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![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Prof. Dr. Xuenian Chen Prof. Dr. Yi‐Hsin Liu Dr. Anne‐Marie Alexander Dr. Judith C. Gallucci Dr. Son‐Jong Hwang Dr. Hima Kumar Lingam Dr. Zhenguo Huang Cong Wang Dr. Huizhen Li Dr. Qianyi Zhao Prof. Dr. Umit S. Ozkan Prof. Dr. Sheldon G. Shore Prof. Dr. Ji‐Cheng Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(24):7325-7333
Attempts to synthesize solvent‐free MgB12H12 by heating various solvated forms (H2O, NH3, and CH3OH) of the salt failed because of the competition between desolvation and dehydrogenation. This competition has been studied by thermogravimetric analysis (TGA) and temperature‐programmed desorption (TPD). Products were characterized by IR, solution‐ and solid‐state NMR spectroscopy, elemental analysis, and single‐crystal or powder X‐ray diffraction analysis. For hydrated salts, thermal decomposition proceeded in three stages, loss of water to form first hexahydrated then trihydrated, and finally loss of water and hydrogen to form polyhydroxylated complexes. For partially ammoniated salts, two stages of thermal decomposition were observed as ammonia and hydrogen were released with weight loss first of 14 % and then 5.5 %. Thermal decomposition of methanolated salts proceeded through a single step with a total weight loss of 32 % with the release of methanol, methane, and hydrogen. All the gaseous products of thermal decomposition were characterized by using mass spectrometry. Residual solid materials were characterized by solid‐state 11B magic ‐ angle spinning (MAS) NMR spectroscopy and X‐ray powder diffraction analysis by which the molecular structures of hexahydrated and trihydrated complexes were solved. Both hydrogen and dihydrogen bonds were observed in structures of [Mg(H2O)6B12H12] ? 6 H2O and [Mg(CH3OH)6B12H12] ? 6 CH3OH, which were determined by single‐crystal X‐ray diffraction analysis. The structural factors influencing thermal decomposition behavior are identified and discussed. The dependence of dehydrogenation on the formation of dihydrogen bonds may be an important consideration in the design of solid‐state hydrogen storage materials. 相似文献
933.
All‐Inorganic Nanocrystals as a Glue for BiSbTe Grains: Design of Interfaces in Mesostructured Thermoelectric Materials
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Dr. Jae Sung Son Hao Zhang Dr. Jaeyoung Jang Dr. Bed Poudel Al Waring Luke Nally Prof. Dr. Dmitri V. Talapin 《Angewandte Chemie (International ed. in English)》2014,53(29):7466-7470
Nano‐ and mesostructuring is widely used in thermoelectric (TE) materials. It introduces numerous interfaces and grain boundaries that scatter phonons and decrease thermal conductivity. A new approach has been developed for the rational design of the interfaces in TE materials by using all‐inorganic nanocrystals (NCs) that serve as a “glue” for mesoscopic grains. For example, circa 10 nm Bi NCs capped with (N2H5)4Sb2Te7 chalcogenidometallate ligands can be used as an additive to BiSbTe particles. During heat treatment, NCs fill up the voids between particles and act as a “glue”, joining grains in hot‐pressed pellets or solution‐processed films. The chemical design of NC glue allowed the selective enhancement or decrease of the majority‐carrier concentration near the grain boundaries, and thus resulted in doped or de‐doped interfaces in granular TE material. Chemically engineered interfaces can be used as to optimize power factor and thermal conductivity. 相似文献
934.
Selective population transfer in electronic states of dissociative molecular systems is illustrated by adopting a control scheme based on Stark-chirped rapid adiabatic passage (SCRAP). In contrast to the discrete N-level system, dynamical Stark shift is induced in a more complex manner in the molecular electronic states. Wavepacket dynamics on the light-induced potentials, which are determined by the detuning of the pump pulse, can be controlled by additional Stark pulse in the SCRAP scheme. Complete population transfer can be achieved by either lowering the energy barrier along the adiabatic passage or placing the initial wavepacket on a well-defined dressed state suitable for the control. The determination of the pulse sequence is sufficient for controlling population transfer to the target state. 相似文献
935.
J.Y. Son 《Journal of solid state chemistry》2008,181(8):2020-2023
Epitaxial γ phase-NaxCoO2 thin films were deposited on (001) sapphire by the pulsed laser deposition method. To fabricate epitaxial Na0.5CoO2 thin films, we used a solution of iodine-dissolved acetonitrile and obtained an epitaxial Na0.5CoO2 thin film with a high crystallinity because of Na deintercalation of epitaxial Na0.7CoO2. From the spectroscopic ellipsometry analysis, we obtained the optical constants as well as the optical conductivities for the Na0.5CoO2 and Na0.7CoO2 thin films. The energy splitting between eg and a1g increased because of the structural strain of the Na0.7CoO2 thin film. It is inferred that the structural strain is the source for the lower resistivity and the preservation of the strongly correlated system up to 200 K for the Na0.7CoO2 thin film. On the other hand, the strain in the Na0.5CoO2 thin film was not affected, and the charge-ordering state and the Na content (x=0.5) only cause the charge-ordering state. 相似文献
936.
Thai Son Dang Sanjay Kumar Palit Sayan Mukherjee Thang Manh Hoang Santo Banerjee 《The European physical journal. Special topics》2016,225(1):159-170
We investigate the complexity of a hyperchaotic dynamical system perturbed by noise and various nonlinear speech and music signals. The complexity is measured by the weighted recurrence entropy of the hyperchaotic and stochastic systems. The synchronization phenomenon between two stochastic systems with complex coupling is also investigated. These criteria are tested on chaotic and perturbed systems by mean conditional recurrence and normalized synchronization error. Numerical results including surface plots, normalized synchronization errors, complexity variations etc show the effectiveness of the proposed analysis. 相似文献
937.
Ji-Won Son Qintong Hu 《International Journal of Mathematical Education in Science & Technology》2016,47(4):505-530
In order to provide insight into cross-national differences in students’ achievement, this study compares the initial treatment of the concept of function sections of Chinese and US textbooks. The number of lessons, contents, and mathematical problems were analyzed. The results show that the US curricula introduce the concept of function one year earlier than the Chinese curriculum and provide strikingly more problems for students to work on. However, the Chinese curriculum emphasizes developing both concepts and procedures and includes more problems that require explanations, visual representations, and problem solving in worked-out examples that may help students formulate multiple solution methods. This result could indicate that instead of the number of problems and early introduction of the concept, the cognitive demands of textbook problems required for student thinking could be one reason for differences in American and Chinese students’ performances in international comparative studies. Implications of these findings for curriculum developers, teachers, and researchers are discussed. 相似文献
938.
Dong Rag Son Anjanapura V. Raghu Kakarla R. Reddy 《Journal of Macromolecular Science: Physics》2016,55(11):1099-1110
The compatibility of thermally reduced graphene (TRG) with multiblock copolyesters, composed of poly(butylene terephthalate) (PBT) segments and poly(tetramethylene ether) glycol segments, was examined in detail. The morphology observed by optical microscopy and scanning electron microscopy showed that the compatibility was enhanced with increasing content of the PBT segment in the polyester. This compatibility behavior was analyzed quantitatively, by using the percolation threshold of electrical conductivity, and then further analyzed by using the Hansen solubility parameters to provide a general quantitative guideline to predict the compatibility of TRG with various polymers. The results suggest that the total solubility parameter, δT, value of TRG is larger than 24.0 (MPa)½, and thus that the compatibility with polymer is enhanced as the δT value of a polymer increases toward 24.0 (MPa)½. However, this prediction does not fit well in the presence of a comonomer such as acrylic acid, which has a high tendency to hydrogen bond with itself. 相似文献
939.
940.
Reduction on imine moiety (C=N) of quinoxalines by alkyl-/aryllithiums led to a geometrical change on the quinoxaline ring, thereby perturbing the electronic structure to turn on fluorescence emission. Such a structural change resulted in interrupted cyclic-ring systems with electron-donating amine (sp(3)-type) and electron-accepting imine (sp(2)-type) units bridged by a phenylene unit. Through either alkylation or arylation, a highly polarized electron donor-electron acceptor bipolar system was established in a single molecule with dramatically enhanced PL efficiency (up to 60%). 相似文献