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41.
42.
Molecular Heterojunctions of Oligo(phenylene ethynylene)s with Linear to Cruciform Framework
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Zhongming Wei Tim Hansen Marco Santella Xintai Wang Christian R. Parker Xingbin Jiang Tao Li Magni Glyvradal Karsten Jennum Emil Glibstrup Nicolas Bovet Xiaowei Wang Wenping Hu Gemma C. Solomon Mogens Brøndsted Nielsen Xiaohui Qiu Thomas Bjørnholm Kasper Nørgaard Bo W. Laursen 《Advanced functional materials》2015,25(11):1700-1708
Electrical transport properties of molecular junctions are fundamentally affected by the energy alignment between molecular frontier orbitals (highest occupied molecular orbital (HOMO) or lowest unoccupied molecular orbital (LUMO)) and Fermi level (or work function) of electrode metals. Dithiafulvene (DTF) is used as substituent group to the oligo(phenylene ethynylene) (OPE) molecular wires and different molecular structures based on OPE3 backbone (with linear to cruciform framework) are achieved, with viable molecular orbitals and HOMO–LUMO energy gaps. OPE3, OPE3–DTF, and OPE3–tetrathiafulvalene (TTF) can form good self‐assembled monolayers (SAMs) on Au substrates. Molecular heterojunctions based on these SAMs are investigated using conducting probe–atomic force microscopy with different tips (Ag, Au, and Pt) and Fermi levels. The calibrated conductance values follow the sequence OPE3–TTF > OPE3–DTF > OPE3 irrespective of the tip metal. Rectification properties (or diode behavior) are observed in case of the Ag tip for which the work function is furthest from the HOMO levels of the OPE3s. Quantum chemical calculations of the transmission qualitatively agree with the experimental data and reproduce the substituent effect of DTF. Zero‐bias conductance, and symmetric or asymmetric couplings to the electrodes are investigated. The results indicate that improved fidelity of molecular transport measurements may be achieved by systematic studies of homologues series of molecular wires applying several different metal electrodes. 相似文献
43.
Titanium dioxide pigments used in commercial polymers are generally coated with a neutral, alumina/silica gel-coat to improve the pigment physical properties and also to reduce the chemical activity of the titania surface. Production of an acidic alumina/silica coating on titania pigments gives them a chemical activity similar to that previously found in dry clays. This activity is sufficient to increase greatly the bonding of basic organic materials to the pigment surfaces. The enhanced bonding can lead to materials with highly organophilic surfaces. The property changes in polymer composites brought about by these acidic pigments are discussed. 相似文献
44.
Satyanarayana Reddy Jaggavarapu Anand Solomon Kamalakaran Jagadeesh Babu Nanubolu Venkata Prasad Jalli Sravan Kumar Gangisetty Gopikrishna Gaddamanugu 《Tetrahedron letters》2014
Efficient and facile synthesis of 7H-benzopyrano[3,2-c]coumarins has been achieved by mild base promoted reaction of 4-chloro-3-formylcoumarin with diversely functionalized resorcinols. All the products were obtained as pure precipitates from the reaction mixture and the structure of the product was confirmed by X-ray analysis. 相似文献
45.
Solomon Tesfaye Hannah Braun Kaleab Asres Ephrem Engidawork Anteneh Belete Ilias Muhammad Christian Schulze Nadin Schultze Sebastian Guenther Patrick J. Bednarski 《Molecules (Basel, Switzerland)》2021,26(12)
Medicinal plants have been traditionally used to treat cancer in Ethiopia. However, very few studies have reported the in vitro anticancer activities of medicinal plants that are collected from different agro-ecological zones of Ethiopia. Hence, the main aim of this study was to screen the cytotoxic activities of 80% methanol extracts of 22 plants against human peripheral blood mononuclear cells (PBMCs), as well as human breast (MCF-7), lung (A427), bladder (RT-4), and cervical (SiSo) cancer cell lines. Active extracts were further screened against human large cell lung carcinoma (LCLC-103H), pancreatic cancer (DAN-G), ovarian cancer (A2780), and squamous cell carcinoma of the esophagus (KYSE-70) by using the crystal violet cell proliferation assay, while the vitality of the acute myeloid leukemia (HL-60) and histiocytic lymphoma (U-937) cell lines was monitored in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) microtiter assay. Euphorbia schimperiana, Acokanthera schimperi, Kniphofia foliosa, and Kalanchoe petitiana exhibited potent antiproliferative activity against A427, RT-4, MCF-7, and SiSo cell lines, with IC50 values ranging from 1.85 ± 0.44 to 17.8 ± 2.31 µg/mL. Furthermore, these four extracts also showed potent antiproliferative activities against LCLC-103H, DAN-G, A2780, KYSE-70, HL-60, and U-937 cell lines, with IC50 values ranging from 0.086 to 27.06 ± 10.8 µg/mL. Hence, further studies focusing on bio-assay-guided isolation and structural elucidation of active cytotoxic compounds from these plants are warranted. 相似文献
46.
Theories in polymer science play an important role in how experiments are designed and results interpreted. Three areas of polymer chemistry are focussed on: step growth polymerization, particularly predictions of equal reactivity of functional groups; free radical chain polymerization with emphasis on structural irregularities and the consequences of these structures for previous theories; free radical copolymerization and the many models at present under discussion aimed at providing a theoretical basis for predicting the outcome of such copolymerization. The question of whether or not we as polymer chemists have been helped or hindered by theory is addressed. 相似文献
47.
Benjamin L. Solomon Christopher P. Landee Jan L. Wikaira 《Journal of Coordination Chemistry》2014,67(23-24):3953-3971
Using 2-amino-5-chloro-3-fluoropyridine, two new copper halide coordination complexes and two new salts have been synthesized: [(3,5-FCAP)2CuCl2] (1), [(3,5-FCAP)2CuBr2](2), (3,5-FCAPH)2[CuCl4] (3) and (3,5-FCAPH)2[CuBr4] (4) [3,5-FCAP?=?2-amino-5-chloro-3-fluoropyridine; 3,5-FCAPH?=?2-amino-5-chloro-3-fluoropyridinium]. These complexes have been analyzed through single-crystal X-ray diffraction and temperature-dependent magnetic susceptibility. Compounds 1 and 2 crystallize in the triclinic space group P-1, while 3 and 4 crystallize in the monoclinic space group P21/c. All structures were distinct, with 1 giving a bihalide bridged chain, 2 yielding a halide bridged dimer, 3 forming a two-halide bridged chain via short Cl???Cl contacts, and 4 producing a rectangular sheet via short Br???Br contacts. All four compounds exhibit anti-ferromagnetic interactions and were fit to linear chain (1 and 3), dimer (2), and rectangular 2-D sheet (4) models. The resulting J/kB values are ?3.4(1), ?31.3(8), ?0.9(1), and ?9.46(6)?K with an α value (α?=?J?/J) of 0.06(2), respectively. 相似文献
48.
A. Solomon 《The European physical journal. Special topics》2008,160(1):391-397
We find states for a multi-level system which are stable under a very general
model of dissipation, one which is governed simply by generic rate parameters; in general
such stable states are not entangled. We exhibit such a state explicitly for a
two-qubit system. We then specialize to a more physical model of dissipation, one which
is governed by pure dephasing. In such a case it is possible, by choice of the dephasing
rates, to have a stable, and limiting, entangled state under the evolution
governed by the free hamiltonian and pure decoherence. We exhibit such a choice
explicitly which has a stable and limiting two-qubit state of maximum entanglement (Bell
state). 相似文献
49.
Allan I. Solomon 《Foundations of Physics》2010,40(7):684-691
The technique of the normal ordering of non-commuting operators is an important tool in the solution of problems involving
creation and annihilation operators in quantum physics, such as in many-body theory or quantum optics. We point out the inconsistencies
in previous definitions of the two standard normal ordering procedures for such operators, and show how consistent definitions
may be made. 相似文献
50.
In this paper we propose a framework for dynamic routing systems based on their degree of dynamism. Next, we consider its impact on solution methodology and quality. Specifically, we introduce the Partially Dynamic Travelling Repairman Problem and describe several dynamic policies to minimize routing costs. The results of our computational study indicate that increasing the dynamic level results in a linear increase in route length for all policies studied. Furthermore, a Nearest Neighbour policy performed, on the average, uniformly better than the other dispatching rules studied. Among these, a Partitioning policy produced only slightly higher average route lengths. 相似文献