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排序方式: 共有214条查询结果,搜索用时 0 毫秒
201.
202.
Falzon MF Zoombelt AP Wienk MM Janssen RA 《Physical chemistry chemical physics : PCCP》2011,13(19):8931-8939
Developing new acceptor materials as alternatives to fullerene acceptors remains a challenge in the field of organic photovoltaics. We report on the synthesis and optoelectronic properties of three acceptor polymers bearing diketopyrrolopyrrole units in the main chain (PA, PB and PC). Their performance as the acceptor material in bulk heterojunction solar cells using P3HT as the donor material has been tested. The solar cells show relatively high open-circuit voltages (≥0.9 V) but low fill factors and short-circuit current densities limit the photovoltaic device performance. Formation of free charge carriers and low electron mobility are identified as the major obstacles. In blends of P3HT with PA or PB charge formation is limited, while for the P3HT:PC blend photogenerated charges recombine into the PC triplet state before they can separate, unless assisted by a reverse electric field. 相似文献
203.
Dr. Tristan Mes Dr. Seda Cantekin Dirk W. R. Balkenende Martijn M. M. Frissen Martijn A. J. Gillissen Bas F. M. De Waal Dr. Ilja K. Voets Prof. Dr. E. W. Meijer Dr. Anja R. A. Palmans 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8642-8649
The amide bond is a versatile functional group and its directional hydrogen‐bonding capabilities are widely applied in, for example, supramolecular chemistry. The potential of the thioamide bond, in contrast, is virtually unexplored as a structuring moiety in hydrogen‐bonding‐based self‐assembling systems. We report herein the synthesis and characterisation of a new self‐assembling motif comprising thioamides to induce directional hydrogen bonding. N,N′,N′′‐Trialkylbenzene‐1,3,5‐tris(carbothioamide)s (thioBTAs) with either achiral or chiral side‐chains have been readily obtained by treating their amide‐based precursors with P2S5. The thioBTAs showed thermotropic liquid crystalline behaviour and a columnar mesophase was assigned. IR spectroscopy revealed that strong, three‐fold, intermolecular hydrogen‐bonding interactions stabilise the columnar structures. In apolar alkane solutions, thioBTAs self‐assemble into one‐dimensional, helical supramolecular polymers stabilised by three‐fold hydrogen bonding. Concentration‐ and temperature‐dependent self‐assembly studies performed by using a combination of UV and CD spectroscopy demonstrated a cooperative supramolecular polymerisation mechanism and a strong amplification of supramolecular chirality. The high dipole moment of the thioamide bond in combination with the anisotropic shape of the resulting cylindrical aggregate gives rise to sufficiently strong depolarised light scattering to enable depolarised dynamic light scattering (DDLS) experiments in dilute alkane solution. The rotational and translational diffusion coefficients, Dtrans and Drot, were obtained from the DDLS measurements, and the average length, L, and diameter, d, of the thioBTA aggregates were derived (L=490 nm and d=3.6 nm). These measured values are in good agreement with the value Lw=755 nm obtained from fitting the temperature‐dependent CD data by using a recently developed equilibrium model. This experimental verification validates our common practice for determining the length of BTA‐based supramolecular polymers from model fits to experimental CD data. The ability of thioamides to induce cooperative supramolecular polymerisation makes them effective and broadly applicable in supramolecular chemistry. 相似文献
204.
Martijn Caspers Rui Okayasu Adam Skalski Reiji Tomatsu 《Comptes Rendus Mathematique》2014,352(6):507-510
The notion of the Haagerup approximation property, originally introduced for von Neumann algebras equipped with a faithful normal tracial state, is generalised to arbitrary von Neumann algebras. We discuss two equivalent characterisations, one in term of the standard form and the other in term of the approximating maps with respect to a fixed faithful normal semifinite weight. Several stability properties, in particular regarding the crossed product construction are established and certain examples are introduced. 相似文献
205.
Roland Doll David Zueco Martijn Wubs Sigmund Kohler Peter Hnggi 《Chemical physics》2008,347(1-3):243-249
We derive the exact time-evolution for a general quantum system under the influence of a bosonic bath that causes pure phase noise and demonstrate that for a Gaussian initial state of the bath, the exact result can be obtained also within a perturbative time-local master equation approach already in second order of the system–bath coupling strength. We reveal that this equivalence holds if the initial state of the bath can be mapped to a Gaussian phase-space distribution function. Moreover, we discuss the relation to the standard Bloch–Redfield approach. 相似文献
206.
Edgington LE van Raam BJ Verdoes M Wierschem C Salvesen GS Bogyo M 《Chemistry & biology》2012,19(3):340-352
Although significant efforts have been made to understand the mechanisms of caspase activation during apoptosis, many questions remain regarding how and when executioner caspases get activated. We describe the design and synthesis of an activity-based probe that labels caspase-3/-6/-7, allowing direct monitoring of all executioner caspases simultaneously. This probe has enhanced in vivo properties and reduced cross-reactivity compared to our previously reported probe, AB50. Using this probe, we find that caspase-6 undergoes a conformational change and can bind substrates even in the absence of cleavage of the proenzyme. We also demonstrate that caspase-6 activation does not require active caspase-3/-7, suggesting that it may autoactivate or be cleaved by other proteases. Together, our results suggest that caspase-6 activation proceeds through a unique mechanism that may be important for its diverse biological functions. 相似文献
207.
Hao Li Elizabeth L. Ponder Martijn Verdoes Kristijana H. Asbjornsdottir Edgar Deu Laura E. Edgington Jeong Tae Lee Christopher J. Kirk Susan D. Demo Kim C. Williamson Matthew Bogyo 《Chemistry & biology》2012,19(12):1535-1545
Highlights? Purification of Plasmodium proteasomes and labeling with an activity-based probe ? Identification of an epoxyketone-based inhibitor with parasite-specific toxicity ? Demonstration that Plasmodium is sensitive to partial inhibition of its proteasome ? Determination of key parameters for selective parasite killing with proteasome inhibitors 相似文献
208.
W Li WS Roelofs MM Wienk RA Janssen 《Journal of the American Chemical Society》2012,134(33):13787-13795
A series of diketopyrrolopyrrole (DPP)-based small band gap polymers has been designed and synthesized by Suzuki or Stille polymerization for use in polymer solar cells. The new polymers contain extended aromatic π-conjugated segments alternating with the DPP units and are designed to increase the free energy for charge generation to overcome current limitations in photocurrent generation of DPP-based polymers. In optimized solar cells with [6,6]phenyl-C(71)-butyric acid methyl ester ([70]PCBM) as acceptor, the new DPP-polymers provide significantly enhanced external and internal quantum efficiencies for conversion of photons into collected electrons. This provides short-circuit current densities in excess of 16 mA cm(-2), higher than obtained so far, with power conversion efficiencies of 5.8% in simulated solar light. We analyze external and internal photon to collected electron quantum efficiencies for the new polymers as a function of the photon energy loss, defined as the offset between optical band gap and open circuit voltage, and compare the results to those of some of the best DPP-based polymers solar cells reported in the literature. We find that for the best solar cells there is an empirical relation between quantum efficiency and photon energy loss that presently limits the power conversion efficiency in these devices. 相似文献
209.
Michael Lartey Martijn Gillissen Brian J. Adzima Kenichi Takizawa David R. Luebke Hunaid B. Nulwala 《Journal of polymer science. Part A, Polymer chemistry》2013,51(16):3359-3364
The free radical reactivity ratios between styrene and different vinyl‐1,2,3‐triazole regioisomeric monomers in 1,4‐dioxane at 65 °C have been established using nonlinear least square method. The results obtained for the reactivity ratio between regioisomers show exceptionally different polymerization behavior, highlighting the effects of the electronic and steric factors of these regioisomeric monomers. The experimental results highlight the effects of the electronic and sterics on the copolymerization behavior. In case of 1,4‐vinyl‐triazoles, it was found that without the steric effects, the reactivity is very similar to that of styrene and forms random copolymers. However, it was found that 1,5‐vinyl‐triazoles are more reactive than 1,4‐vinyl triazoles. In the case of styrene‐co‐1,4‐vinyl‐1,2,3‐triazoles, the reactivity ratios were calculated to be rstyrene: r1‐octyl‐4‐vinyl‐triazole = 1.97:0.54, rstyrene : r1‐benzyl‐4‐vinyl‐triazole = 1.62:0.50, and rstyrene: r1‐methyl‐4‐vinyl‐triazole = 0.90:0.87. On the other hand, reactivity ratios for styrene‐co‐1,5‐vinyl‐1,2,3‐triazoles were found to be rstyrene: r1‐octyl‐5‐vinyl‐triazole = 0.13:0.66 and rstyrene: r1‐benzyl‐5‐vinyl‐triazole = 0.34:0.49. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3359–3364 相似文献
210.
Verdoes M Florea BI Menendez-Benito V Maynard CJ Witte MD van der Linden WA van den Nieuwendijk AM Hofmann T Berkers CR van Leeuwen FW Groothuis TA Leeuwenburgh MA Ovaa H Neefjes JJ Filippov DV van der Marel GA Dantuma NP Overkleeft HS 《Chemistry & biology》2006,13(11):1217-1226
The proteasome is an essential evolutionary conserved protease involved in many regulatory systems. Here, we describe the synthesis and characterization of the activity-based, fluorescent, and cell-permeable inhibitor Bodipy TMR-Ahx(3)L(3)VS (MV151), which specifically targets all active subunits of the proteasome and immunoproteasome in living cells, allowing for rapid and sensitive in-gel detection. The inhibition profile of a panel of commonly used proteasome inhibitors could be readily determined by MV151 labeling. Administration of MV151 to mice allowed for in vivo labeling of proteasomes, which correlated with inhibition of proteasomal degradation in the affected tissues. This probe can be used for many applications ranging from clinical profiling of proteasome activity, to biochemical analysis of subunit specificity of inhibitors, and to cell biological analysis of the proteasome function and dynamics in living cells. 相似文献