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排序方式: 共有600条查询结果,搜索用时 15 毫秒
61.
FU Yao-Tsung YI YuanPing COROPCEANU Veaceslav RISKO Chad AZIZ Saadullah G. BRDAS Jean-Luc 《中国科学:化学(英文版)》2014,57(10):1330-1339
We review some of the computational methodologies used in our research group to develop a better understanding of the geometric and electronic structures of organic-organic interfaces present in the active layer of organic solar cells. We focus in particular on the exciton-dissociation and charge-transfer processes at the pentacene-fullerene interface. We also discuss the local morphology at this interface on the basis of molecular dynamics simulations. 相似文献
62.
William K. Bell Brandon M. Rawlings Brian K. Long R. Chad Webb B. Keith Keitz Lukas Häußling C. Grant Willson 《Journal of polymer science. Part A, Polymer chemistry》2014,52(19):2769-2775
A series of photocrosslinkable polymers bearing hyperpolarizable side chain chromophores was synthesized, poled and evaluated on the basis of the thermal stability of Second Harmonic Generation (SHG). Photoinitiation allowed for control of the onset of curing. Crosslinking was monitored by infrared spectroscopy and optimal conversion was achieved by applying a slow temperature ramp during exposure. The ultimate stability of the poled polymers was directly related to the number of crosslinking substituents that were attached to the chromophore pendant group. With two reactive groups per chromophore significant SHG was retained at temperatures above the initial polymer glass transition temperature. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2769–2775 相似文献
63.
Inversion twinning in a second polymorph of the hydrochloride salt of the recreational drug ethylone
T. Stanley Cameron J. Stuart Grossert Chad R. Maheux Idralyn Q. Alarcon Catherine R. Copeland Anthony Linden 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(4):266-270
A second polymorph of the hydrochloride salt of the recreational drug ethylone, C12H16NO3+·Cl−, is reported [systematic name: (±)‐2‐ethylammonio‐1‐(3,4‐methylenedioxyphenyl)propane‐1‐one chloride]. This polymorph, denoted form (A), appears in crystallizations performed above 308 K. The originally reported form (B) [Wood et al. (2015). Acta Cryst. C 71 , 32–38] crystallizes preferentially at room temperature. The conformations of the cations in the two forms differ by a 180° rotation about the C—C bond linking the side chain to the aromatic ring. Hydrogen bonding links the cations and anions in both forms into similar extended chains in which any one chain contains only a single enantiomer of the chiral cation, but the packing of the ions is different. In form (A), the aromatic rings of adjacent chains interleave, but pack equally well if neighbouring chains contain the same or opposite enantiomorph of the cation. The consequence of this is then near perfect inversion twinning in the structure. In form (B), neighbouring chains are always inverted, leading to a centrosymmetric space group. The question as to why the polymorphs crystallize at slightly different temperatures has been examined by density functional theory (DFT) and lattice energy calculations and a consideration of packing compactness. The free energy (ΔG) of the crystal lattice for polymorph (A) lies some 52 kJ mol−1 above that of polymorph (B). 相似文献
64.
Shunzhi Wang William Morris Yangyang Liu C. Michael McGuirk Yu Zhou Prof. Joseph T. Hupp Prof. Omar K. Farha Prof. Chad A. Mirkin 《Angewandte Chemie (International ed. in English)》2015,54(49):14738-14742
A method for modifying the external surfaces of a series of nanoscale metal–organic frameworks (MOFs) with 1,2‐dioleoyl‐sn‐glycero‐3‐phosphate (DOPA) is presented. A series of zirconium‐based nanoMOFs of the same topology (UiO‐66, UiO‐67, and BUT‐30) were synthesized, isolated as aggregates, and then conjugated with DOPA to create stably dispersed colloids. BET surface area analysis revealed that these structures maintain their porosity after surface functionalization, providing evidence that DOPA functionalization only occurs on the external surface. Additionally, dye‐labeled ligand loading studies revealed that the density of DOPA on the surface of the nanoscale MOF correlates to the density of metal nodes on the surface of each MOF. Importantly, the surface modification strategy described will allow for the general and divergent synthesis and study of a wide variety of nanoscale MOFs as stable colloidal materials. 相似文献
65.
Radical Compatibility with Nonaqueous Electrolytes and Its Impact on an All‐Organic Redox Flow Battery 下载免费PDF全文
Dr. Xiaoliang Wei Dr. Wu Xu Dr. Jinhua Huang Dr. Lu Zhang Dr. Eric Walter Dr. Chad Lawrence Dr. M. Vijayakumar Dr. Wesley A. Henderson Dr. Tianbiao Liu Dr. Lelia Cosimbescu Dr. Bin Li Dr. Vincent Sprenkle Dr. Wei Wang 《Angewandte Chemie (International ed. in English)》2015,54(30):8684-8687
Nonaqueous redox flow batteries hold the promise of achieving higher energy density because of the broader voltage window than aqueous systems, but their current performance is limited by low redox material concentration, cell efficiency, cycling stability, and current density. We report a new nonaqueous all‐organic flow battery based on high concentrations of redox materials, which shows significant, comprehensive improvement in flow battery performance. A mechanistic electron spin resonance study reveals that the choice of supporting electrolytes greatly affects the chemical stability of the charged radical species especially the negative side radical anion, which dominates the cycling stability of these flow cells. This finding not only increases our fundamental understanding of performance degradation in flow batteries using radical‐based redox species, but also offers insights toward rational electrolyte optimization for improving the cycling stability of these flow batteries. 相似文献
66.
Digital microfluidics based on electrowetting-on-dielectric (EWOD) has recently emerged as one of the most promising technologies to realize integrated and highly flexible lab-on-a-chip systems. In such EWOD-based digital microfluidic devices, the aqueous droplets have traditionally been manipulated either directly in air or in an immiscible fluid such as silicone oil. However, both transporting mediums have important limitations and neither offers the flexibility required to fulfil the needs of several applications. In this paper, we report on an alternative mode of operation for EWOD-based devices in which droplets enclosed in a thin layer of oil are manipulated in air. We demonstrate the possibility to perform on-chip the fundamental fluidic operations by using such water-oil core-shell droplets and compare systematically the results with the traditional approach where the aqueous droplets are manipulated directly in air or oil. We show that the core-shell configuration combines several advantages of both the air and oil mediums. In particular, this configuration not only reduces the operation voltage of EWOD-based devices but also leads to higher transport velocities when compared with the manipulation of droplets directly in air or oil. 相似文献
67.
Vecitis CD Park H Cheng J Mader BT Hoffmann MR 《The journal of physical chemistry. A》2008,112(18):4261-4270
The perfluorinated surfactants perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are recognized as widespread in the environment as well as recalcitrant toward most conventional water treatment technologies. In this study, acoustic cavitation as driven by high-frequency ultrasound is shown to be effective in the degradation of aqueous solutions of PFOS and PFOA and effective over a wide range of concentrations from 10 nM to 10 muM for a given compound. Sulfur, fluorine, and carbon mass balances indicate that mineralization occurs immediately following the degradation of the initial perfluorinated surfactant. Near complete conversion of PFOS and PFOA to CO, CO2, F-, and SO42- occurs due to pyrolytic reactions at the surface and vapor phase of transiently collapsing cavitation bubbles. The initial PFOS or PFOA pyrolytic degradation occurs at the bubble-water interface and involves the loss of the ionic functional group leading to the formation of the corresponding 1H-fluoroalkane or perfluoroolefin. The fluorochemical intermediates undergo a series of pyrolytic reactions in the bubble vapor leading to C1 fluoro-radicals. Secondary vapor-phase bimolecular reactions coupled with concomitant hydrolysis converts the C1 fluoro-radicals to carbon monoxide, carbon dioxide, and HF, forming a proton and fluoride upon dissolution. Sonochemical half-lives, which are calculated from high-temperature gas-phase kinetics, are consistent with kinetic observations and suggest that mineralization occurs shortly after initial perfluorinated surfactant interfacial pyrolysis. 相似文献
68.
The Suzuki reaction in water using parts per million concentrations of palladium is reported using potassium trifluoroborates as alternatives to boronic acids as substrates. 相似文献
69.
70.
Oh BK Park S Millstone JE Lee SW Lee KB Mirkin CA 《Journal of the American Chemical Society》2006,128(36):11825-11829
Two-component triblock magnetic nanorods with gold end blocks and nickel interior blocks have been synthesized and used as affinity templates for the simultaneous and efficient separation of a three-component protein mixture. The gold blocks were selectively functionalized with 11-amino-1-undecanethiol, and then glutaraldehyde was used to covalently attach nitrostreptavidin to them. His-tagged proteins bind to the nickel block and biotin-tagged proteins bind to the functionalized gold ends, allowing one to separate a mixture of three proteins with a single material. Each surface-bound protein can be released selectively using imidazole for the His-tagged protein and biotin for the biotinylated protein. 相似文献