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51.
52.
Molecular dynamics computer simulations are used to study the structure and dynamics of 1-nm wide films of poly(ethylene oxide) (PEO) confined between mica-type layered silicates of different cation exchange capacities (CEC). The simulation setup mimics experimental systems formed by intercalation of PEO in montmorillonite alumino-silicates with varied inherent charges. It is shown that the presence and population of lithium has a significant influence on the behavior of the system, in addition to the confinement-induced effects caused by the extreme spatial restriction. The structural features of the confined PEO are strongly altered with the number of Li+, which determines the polymer/inorganic interactions. The combination of the nanoconfinement and the presence of lithium preclude regular ordered arrangements of PEO, similar to those observed in the bulk unconfined polymer. The segmental dynamics of PEO in confinement are also greatly influenced by the presence of lithium, because of the strong interaction between Li+ and the oxygen of the PEO backbone. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3460–3477, 2005 相似文献
53.
Polina Angelova Kalina Kostova Karsten Hinrichs Dimiter Tsankov 《Central European Journal of Chemistry》2005,3(4):658-667
New 4-substituted benzyl esters of 16-mercaptohexadecanoic acid were prepared by developing a practicable synthetic procedure
and using readily available staring materials. The compounds synthesized have been characterized by NMR, MS, IR spectra and
elemental analysis. The mercapto derivatives are precursors for the formation of self-assembled monolayers on metal substrates.
Dedicated to Professor Dr. Manfred Hesse on the occasion of his 70
th
birthday 相似文献
54.
研究了在CdSe/ZnSe自组装量子点中CdSe量子点的发光随着激发光强度变化的特性。发现当激发强度(I)变化3个数量级的时候,量子点发光的峰位、峰形都没有发生明显的变化。通过公式L∝Ik(其中I是激发光强度,L是量子点发光强度,k是非线性系数)得到非线性系数k值。实验结果表明:在温度由21 K升高到300 K的过程中,k值随温度变化可以分为3个区域:当温度低于120 K时,k值接近于1;然后,随着温度升高,k值慢慢变小;最后,随温度进一步升高,k值由200 K时的0.946迅速减少到0.870。结合发光随温度变化的实验结果,确认在120 K以下发光主要来源于束缚激子复合。在温度由200 K升高到300 K的过程中,非线性系数的单调减小主要归因于随着温度的升高,发光部分来自于由自由电子或空穴到束缚态能级(FB)的复合。进一步通过分析量子点发光的积分强度随着温度的变化的实验结果,发现发光强度随温度升高而减弱的主要原因是材料中的缺陷或者位错等提供非辐射渠道。 相似文献
55.
Self-assembly of decylphosphonic acid (DPA) and octadecylphosphonic acid (ODPA) was studied on aluminum films using XPS, ToF-SIMS and surface wettability. Modified aluminum films were tested for passivation against silanization and subsequent oligonucleotide attachment. Passivation ratios of at least 450:1 compared to unprotected aluminum were obtained, as quantified by attachment of radio-labeled oligos. 相似文献
56.
介绍了所设计的虚拟实验系统,对系统方案、基本功能以及在设计过程中所遇到的一些设计问题进行分析并提出了解决方法。 相似文献
57.
InAs/GaAs submonolayer quantum-dot superluminescent diodes with active multimode interferometer configuration 总被引:1,自引:0,他引:1
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With a chirped InAs/GaAs SML-QD (quantum dot) structure serving as the active region, the superluminescent diodes emitting at wavelength of around 970nm are fabricated. By using an active multimode interferometer configuration, these devices exhibit high continue-wave output powers from the narrow ridge waveguides. At continue-wave injection current of 800mA, an output power of 18.5mW, and the single Gaussian-like emission spectrum centered at 972nm with a full width at half maximum of 18nm are obtained. 相似文献
58.
Arindam Sannyal Joonkyung Jang Md. Shajahan Joyanta K. Saha 《Journal of computational chemistry》2019,40(30):2636-2642
Atomic force microscope technique is widely used for the spatial narrow deposition of molecules inside the bare space of preexisting self-assembled monolayer (SAM) matrix. Using molecular dynamics simulation, we studied the formation of positively patterned SAM from a globule of 1-octadecanethiol (ODT) on predesigned SAM matrix of 1-dodecanethiol (DDT) and effect of temperature on it. The alkyl chains of ODT SAM were densely packed and ordered by means of chemisorption through sulfur atoms. The circular SAM of ODT contained defects due to the molecules those were standing upside down or trapped inside ODT SAM. We found that with the increase of temperature, these defects moved out by flipping of inverted ODT molecules or building spaces to be adsorbed on Au surface. The ODT molecules on the top of the pile of stable circular SAM or those are upside down and trapped disperse in a unique fashion namely serial pushing through which molecules firstly make a free space to enter inside the adsorbed thiol molecules and then push neighboring molecules to get enough space to be adsorbed on the gold surface. The stability of ODT SAM was confirmed by analyzing different structural properties such as tilt angle, tilt orientation. and backbone orientation. We also calculated the diffusion coefficient of the ODT molecules which were on the top of SAM island. © 2019 Wiley Periodicals, Inc. 相似文献
59.
Self-assembled monolayers (SAMs) based on oligopeptides have garnered immense interest for a wide variety of innovative biomedical and electronic applications. However, to exploit their full potential, it is necessary to understand and control the surface chemistry of oligopeptides. Herein, we report on how different electrical potentials affect the adsorption kinetics, stability and surface coverage of charged oligopeptide SAMs on gold surfaces. Kinetic analysis using electrochemical surface plasmon resonance (e-SPR) reveals a slower oligopeptide adsorption rate at more positive or negative electrical potentials. Additional analysis of the potential-assisted formed SAMs by X-ray photoelectron spectroscopy demonstrates that an applied electrical potential has minimal effect on the packing density. These findings not only reveal that charged oligopeptides exhibit a distinct potential-assisted assembly behaviour but that an electrical potential offers another degree of freedom in controlling their adsorption rate. 相似文献
60.
Dr. Hiromichi Nakahara Dr. Marie Pierre Krafft Prof. Osamu Shibata 《Chemphyschem》2020,21(17):1966-1970
We found that monolayers of dipalmitoylphosphatidylcholine (DPPC) and semi-fluorinated tetrablock di(F10H16) self-assemble to form a new type of large, complex flower-like patterns on the surface of water and on solid substrates. The hierarchical organization of these unusual self-assemblies was investigated using compression and surface potential isotherms, in situ fluorescence and Brewster angle microscopies, and atomic force microscopy after transfer. 相似文献