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131.
Paraskar AS Reddy AR Patra A Wijsboom YH Gidron O Shimon LJ Leitus G Bendikov M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(34):10639-10647
Surprisingly, despite its very high mobility in a single crystal, rubrene shows very low mobility in vacuum-sublimed or solution-processed organic thin-film transistors. We synthesized several rubrene analogues with electron-withdrawing and electron-donating substituents and found that most of the substituted rubrenes are not planar in the solid state. Moreover, we conclude (based on experimental and calculated data) that even parent rubrene is not planar in solution and in thin films. This discovery explains why high mobility is reported in rubrene single crystals, but rubrene shows very low field-effect mobility in thin films. The substituted rubrenes obtained in this work have significantly better solubility than parent rubrene and some even form films and not crystals after evaporation of the solvent. Thus, substituted rubrenes are promising materials for organic light-emitting diode (OLED) applications. 相似文献
132.
O. V. Platonova S. B. Volkova S. A. Malin E. A. Veretennikov B. M. Laskin A. S. Malin 《Russian Journal of Applied Chemistry》2008,81(3):513-515
Heat exchangers of circulating type are used extensively in the heat exchange processes. Circulation of liquid in these devices is ensured by mechanical mixing devices, and heat exchange is enhanced by the increase of the heat exchange surface. The application of the upright heat exchange elements like double pipes providing a cross-flow regime in the device is the most effective. Calculation of the apparatus with the vertical heat-exchange elements for determination of constructive and regime parameters at maximum output of the device was presented. 相似文献
133.
Bergenstråhle M Wohlert J Larsson PT Mazeau K Berglund LA 《The journal of physical chemistry. B》2008,112(9):2590-2595
Solid-state nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy has often been used to study cellulose structure, but some features of the cellulose NMR spectrum are not yet fully understood. One such feature is a doublet around 84 ppm, a signal that has been proposed to originate from C4 atoms at cellulose fibril surfaces. The two peaks yield different T1, differing by approximately a factor of 2 at 75 MHz. In this study, we calculate T1 from C4-H4 vector dynamics obtained from molecular dynamics computer simulations of cellulose I beta-water interfacial systems. Calculated and experimentally obtained T1 values for C4 atoms in surface chains fell within the same order of magnitude, 3-20 s. This means that the applied force field reproduces relevant surface dynamics for the cellulose-water interface sufficiently well. Furthermore, a difference in T1 of about a factor of 2 in the range of Larmor frequencies 25-150 MHz was found for C4 atoms in chains located on top of two different crystallographic planes, namely, (110) and (10). A previously proposed explanation that the C4 peak doublet could derive from surfaces parallel to different crystallographic planes is herewith strengthened by computationally obtained evidence. Another suggested basis for this difference is that the doublet originates from C4 atoms located in surface anhydro-glucose units with hydroxymethyl groups pointing either inward or outward. This was also tested within this study but was found to yield no difference in calculated T1. 相似文献
134.
Dr. Qiang Wen Dr. Naveen Malik Dr. Yoseph Addadi Maren Weißenfels Vivek Singh Dr. Linda J. W. Shimon Dr. Michal Lahav Prof. Milko E. van der Boom 《Angewandte Chemie (International ed. in English)》2023,62(4):e202214041
In this study, the precise positioning and alignment of arrays of two different guest molecules in a crystalline host matrix has been engineered and resulted in new optically active materials. Sub-nm differences in the diameters of two types of 1D channels are sufficient for size-selective inclusion of dyes. Energy transport occurs between the arrays of different dyes that are included in parallel-positioned nanochannels by Förster resonance energy transfer (FRET). The color of individual micro-sized crystals are dependent on their relative position under polarized light. This angular-dependent behavior is a result of the geometrically constrained orientation of the dyes by the crystallographic packing of the host matrix and is concentration dependent. 相似文献
135.
A homonuclear dipolar decoupling scheme based on windowed phase-modulated Lee-Goldburg (wPMLG) pulse sequences that causes a"z-rotation" of the spins for high-resolution proton NMR spectroscopy of solids is described and analyzed. This supercycled scheme suppresses the effect of pulse imperfections on the spectra and significantly relaxes the off-resonance dependence of the line-narrowing efficiency and scale factor. This leads to a broad spectral window that is free of artifacts such as zero lines, image peaks, and localized rotor-radio-frequency resonances. High-resolution (1)H spectra and two-dimensional homonuclear (1)H-(1)H correlation spectra of standard amino acids, obtained by a combination of this supercycled scheme with magic angle spinning frequencies up to 25 kHz, are demonstrated. 相似文献
136.
Shimon Brooks 《Annales Henri Poincare》2016,17(3):615-643
We consider the question of quantum unique ergodicity (QUE) for quasimodes on surfaces of constant negative curvature, and conjecture the order of quasimodes that should satisfy QUE. We then show that this conjecture holds for Eisenstein series on \({SL(2,\mathbb{Z})\backslash\mathbb{H}}\) , extending results of Luo–Sarnak and Jakobson. Moreover, we observe that the equidistribution results of Luo–Sarnak and Jakobson extend to quasimodes of much weaker order—for which QUE is known to fail on compact surfaces—though in this scenario the total mass of the limit measures will decrease. We interpret this stronger equidistribution property in the context of arithmetic QUE, in light of recent joint work with Lindenstrauss (Invent Math 198(1), 219–259, 2014) on joint quasimodes. 相似文献
137.
Dr. Chen Shahar Dr. Sounak Dutta Dr. Haim Weissman Dr. Linda J. W. Shimon Dr. Holger Ott Prof. Boris Rybtchinski 《Angewandte Chemie (International ed. in English)》2016,55(1):179-182
Understanding and controlling organic crystallization in solution is a long‐standing challenge. Herein, we show that crystallization of an aromatic amphiphile based on perylene diimide in aqueous media involves initially formed amorphous spherical aggregates that evolve into the crystalline phase. The initial appearance of the crystalline order is always confined to the spherical aggregates that are precursors for crystalline evolution. The change in the solvation of the prenucleation phase drives the crystallization process towards crystals that exhibit very different structure and photofunction. The initial molecular structure and subsequent crystal evolution can be regulated by tuning the hydrophobicity at various stages of crystallization, affording dissimilar crystalline products or hindering crystallization. Thus, the key role of the precrystalline states in organic crystal evolution enables a new strategy to control crystallization by precrystalline state manipulation. 相似文献
138.
Dr. Ranjeesh Thenarukandiyil Dr. Vanaparthi Satheesh Dr. Linda J. W. Shimon Dr. Graham de Ruiter 《化学:亚洲杂志》2021,16(8):999-1006
During the past decade earth-abundant metals have become increasingly important in homogeneous catalysis. One of the reactions in which earth-abundant metals have found important applications is the hydroboration of unsaturated C−C and C−X bonds (X=O or N). Within these set of transformations, the hydroboration of challenging substrates such as nitriles, carbonates and esters still remain difficult and often relies on elaborate ligand designs and highly reactive catalysts (e. g., metal alkyls/hydrides). Here we report an effective methodology for the hydroboration of challenging C≡N and C=O bonds that is simple and applicable to a wide set of substrates. The methodology is based on using a manganese(II) triflate salt that, in combination with commercially available potassium tert-butoxide and pinacolborane, catalyzes the hydroboration of nitriles, carbonates, and esters at room temperature and with near quantitative yields in less than three hours. Additional studies demonstrated that other earth-abundant metal triflate salts can facilitate this reaction as well, which is further discussed in this report. 相似文献
139.
Peilei Yang Chaoyang Zhang Malin Li Xu Yang Prof. Dr. Chunzhong Wang Dr. Xiaofei Bie Prof. Dr. Yingjin Wei Prof. Dr. Gang Chen Prof. Dr. Fei Du 《Chemphyschem》2015,16(16):3408-3412
As a promising positive electrode material for sodium‐ion batteries (SIBs), layered sodium oxides have attracted considerable attention in recent years. In this work, stoichiometric P2‐phase NaCo0.5Mn0.5O2 was prepared through the conventional solid‐state reaction, and its structural and physical properties were studied in terms of XRD, XPS, and magnetic susceptibility. Furthermore, the P2‐NaCo0.5Mn0.5O2 electrode delivered a discharge capacity of 124.3 mA h g?1 and almost 100 % initial coulombic efficiency over the potential window of 1.5–4.15 V. It also showed good cycle stability, with a reversible capacity and capacity retention reaching approximately 85 mA h g?1 and 99 %, respectively, at the 5 C rate after 100 cycles. Additionally, cyclic voltammetry and ex situ XRD were employed to explain the electrochemical behavior at the different electrochemical stages. Owing to the applicable performances, P2‐NaCo0.5Mn0.5O2 can be considered as a potential positive electrode material for SIBs. 相似文献
140.
Vesna Bacheva Dr. Federico Paratore Dr. Shimon Rubin Dr. Govind V. Kaigala Prof. Moran Bercovici 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(31):12994-12999
We present a new concept for on-chip separation that leverages bidirectional flow, to tune the dispersion regime of molecules and particles. The system can be configured so that low diffusivity species experience a ballistic transport regime and are advected through the chamber, whereas high diffusivity species experience a diffusion dominated regime with zero average velocity and are retained in the chamber. We detail the means of achieving bidirectional electroosmotic flow using an array of alternating current (AC) field-effect electrodes, experimentally demonstrate the separation of particles and antibodies from dyes, and present a theoretical analysis of the system, providing engineering guidelines for its design and operation. 相似文献