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71.
Ramin Zakeri 《Molecular simulation》2013,39(18):1488-1497
ABSTRACTIn this research, the numerical simulation of a soft polymer micro actuator performance has been investigated using the dissipative particle dynamics method in electro-osmotic flow. Effective factors including electro-osmotic flow and polymer chain parameters have been studied. First of all, considering a wide range of electro-osmotic parameters, the validation of analytical results is carried out in a simple micro channel. The electric field and zeta potential changes are linearly related to the flow rate, and the kh parameter behaves nonlinearly to around the kh?=?10. In the following, a convergent–divergent channel is used for the soft micro actuator simulation in which a polymer chain as a heart of actuation is embedded in the middle. As the main control parameter, the direction of the electric field is changed every 4?s, and it leads to a reciprocating motion. The numerical results indicate that the displacement of the soft polymer chain will be increased by enhancing the electric field, the number of beads, decreasing the harmonic bond coefficient and also exposing more length of a polymer chain in front of fluid flow. The results of this study may be useful for some future applications such as artificial fibres and muscles. 相似文献
72.
Xian-Ming Zhang Jie-Sheng Chen Cai-Rong Ding Xiao-Ming Chen 《Inorganica chimica acta》2004,357(5):1389-1396
Three cluster-based coordination polymers, namely [Zn3(bpy)3(hip)2] · 5H2O (1), [Co3(bpy)3(hip)2] · 5H2O (2) and [Cd3(bpy)3(hip)2] (3) (bpy=2,2′-bipyridine, hip=4-hydroxyl-isophthalate) were synthesized and structurally characterized. X-ray single-crystal structural analyses revealed that both 1 and 2 crystallize in the chiral space group P21, while 3 crystallizes in the centric space group Pccn. Compounds 1 and 2 are isomorphous and both have (4,4) topological layered structures constructed from trinuclear metal clusters. Compound 3 also shows layered structure of (4,4) topology constructed from trinulear Cd(II) cores. The layers are stacked in a staggered ?ABAB? fashion in 1 and 2 but in an overlapped ?AAA? fashion in 3. There are two types of coordination modes of hip ligand in 1 and 2 but only one in 3. The structural difference between 1 (or 2) and 3 may be attributed to the difference of metal ion nature such as the ionic radius and coordination preference, resulting in the different orientation fashions of the auxiliary bpy ligands, stacking fashions of the layers, as well as chirality of the crystals. The chiral structures of 1 and 2 were also confirmed by measurements of powder second-harmonic-generation (SHG) measurements, which show that 1 and 2 have SHG intensity of 0.50 and 0.02 relative to that of urea, respectively. 相似文献
73.
Xin-Hui Zhou 《Inorganica chimica acta》2006,359(5):1442-1448
Six copper(I) complexes {[Cu2(L1)(PPh3)2I2] · 2CH2Cl2}n (1), {[Cu2(L2)(PPh3)2]BF4}n (2), [Cu2(L3)(PPh3)4I2] · 2CH2Cl2 (3), [Cu2(L4)(PPh3)4I2] (4), [Cu2(L5)(PPh3)2I2] (5) and [Cu2(L6)(PPh3)2I2] (6) have been prepared by reactions of bis(schiff base) ligands: pyridine-4-carbaldehyde azine (L1), 1,2-bis(4′-pyridylmethyleneamino)ethane (L2), pyridine-3-carbaldehyde azine (L3), 1,2-bis(3′-pyridylmethyleneamino)ethane (L4), pyridine-2-carbaldehyde azine (L5), 1,2-bis(2′-pyridylmethyleneamino)ethane (L6) with PPh3 and copper(I) salt, respectively. Ligand L1 or L2 links (PPh3)2Cu2(μ-I)2 units to form an infinite coordination polymer chain. Ligand 3 or 4 acts as a monodentate ligand to coordinate two copper(I) atoms yielding a dimer. Ligand 5 or 6 chelates two copper(I) atoms using pyridyl nitrogen and imine nitrogen to form a dimer. Complexes 1-4 exhibit photoluminescence in the solid state at room temperature. The emission has been attributed to be intraligand π-π* transition mixed with MLCT characters. 相似文献
74.
A sensitive fluorescent nanosensor for chloramphenicol based on molecularly imprinted polymer‐capped CdTe quantum dots 下载免费PDF全文
A novel fluorescent nanosensor using molecularly imprinted silica nanospheres embedded CdTe quantum dots (CdTe@SiO2@MIP) was developed for detection and quantification of chloramphenicol (CAP). The imprinted sensor was prepared by synthesis of molecularly imprinting polymer (MIP) on the hydrophilic CdTe quantum dots via reverse microemulsion method using small amounts of solvents. The resulting CdTe@SiO2@MIP nanoparticles were characterized by fluorescence, UV–vis absorption and FT‐IR spectroscopy and transmission electron microscopy. They preserved 48% of fluorescence quantum yield of the parent quantum dots. CAP remarkably quenched the fluorescence of prepared CdTe@SiO2@MIP, probably via electron transfer mechanism. Under the optimal conditions, the relative fluorescence intensity of CdTe@SiO2@MIP decreased with increasing CAP by a Stern–Volmer type equation in the concentration range of 40–500 µg L–1. The corresponding detection limit was 5.0 µg L–1. The intra‐day and inter‐day values for the precision of the proposed method were all <4%. The developed sensor had a good selectivity and was applied to determine CAP in spiked human and bovine serum and milk samples with satisfactory results. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
75.
Intense Chiral Optical Phenomena in Racemic Polymers by Cocrystallization With Chiral Guest Molecules: A Brief Overview 下载免费PDF全文
This review is devoted to the chiral optical behavior of films of racemic polymers whose chirality is induced by cocrystallization with nonracemic (also temporary) guest molecules. We provide examples of macromolecular amplification of chirality, produced by molecular and supramolecular mechanisms, on industrially relevant polymers like poly(2,6‐dimethyl‐1,4‐phenylene)oxide (PPO) and syndiotactic polystyrene (s‐PS). Chirality 28:29–38, 2016. © 2015 Wiley Periodicals, Inc. 相似文献
76.
In order to examine a procedure whereby the points of covalent attachment between the components of a protein-polymer conjugate could be determined, horse heart cytochrome c was attached to a beaded copolymer of N-acrylylpyrrolidine, N,N′-bis(acrylyl)-1,2-diaminoethane and N-acrylyl-1,6-aminohexane through a cleavable azo linkage. Studies of protein removed from this conjugate showed that attachment of the polymer to cytochrome occurred predominantly through single lysine residues on the protein surface; lysine-25 was tentatively identified as the residue most extensively utilized in this way. Protein was also linked to the polymer by two lysine residues and a significant amount of protein was irreversibly attached to the polymer under the reaction conditions used. 相似文献
77.
Marie Francene A. Cutiongco Benjamin Kim Kiat Teo Evelyn King Fai Yim 《Journal of visualized experiments : JoVE》2015,(102)
Various scaffolds used in tissue engineering require a controlled biochemical environment to mimic the physiological cell niche. Interfacial polyelectrolyte complexation (IPC) fibers can be used for controlled delivery of various biological agents such as small molecule drugs, cells, proteins and growth factors. The simplicity of the methodology in making IPC fibers gives flexibility in its application for controlled biomolecule delivery. Here, we describe a method of incorporating IPC fibers into two different polymeric scaffolds, hydrophilic polysaccharide and hydrophobic polycaprolactone, to create a multi-component composite scaffold. We showed that IPC fibers can be easily embedded into these polymeric structures, enhancing the capability for sustained release and improved preservation of biomolecules. We also created a composite polymeric scaffold with topographical cues and sustained biochemical release that can have synergistic effects on cell behavior. Composite polymeric scaffolds with IPC fibers represent a novel and simple method of recreating the cellular niche. 相似文献
78.
Kotchakorn JuntapramNalena Praphairaksit Krisana SiraleartmukulNongnuj Muangsin 《Carbohydrate polymers》2012,87(4):2399-2408
Two mucoadhesive thiolated polymers were synthesized by the covalent attachment of homocysteine thiolactone (HT) to chitosan and N,N,N-trimethyl-chitosan (TM-chitosan) at various chitosan:HT ratios. The amount of thiol and disulphide groups immobilized on the chitosan influenced the polymer's mucoadhesion positively and negatively, respectively, with the optimal chitosan:HT (w/w) ratio being found to be 1:0.1. The interaction between mucin and chitosan and its three derivatives was highest for the thiolated chitosan derivatives but was pH dependent. HT-chitosan and TM-HT-chitosan, with the thiol groups of 64.15 and 32.48 μmol/g, respectively, displayed a 3.67- and 6.33-fold stronger mucoadhesive property compared to that of the unmodified chitosan at pH 1.2, but these differences were only ∼1.7-fold at pH 6.4. The swelling properties of TM-HT-chitosan and HT-chitosan were higher than that of chitosan and TM-chitosan, attaining a swelling ratio of up to 240% and 140%, respectively, at pH 1.2 within 2 h. 相似文献
79.
Polymer Solar Cells: High‐Efficiency Inverted Polymer Photovoltaics via Spectrally Tuned Absorption Enhancement (Adv. Energy Mater. 14/2014) 下载免费PDF全文
80.
Steven A. Hawks Florent Deledalle Jizhong Yao Dylan G. Rebois Gang Li Jenny Nelson Yang Yang Thomas Kirchartz James R. Durrant 《Liver Transplantation》2013,3(9):1201-1209
We explore the interrelation between density of states, recombination kinetics, and device performance in efficient poly[4,8‐bis‐(2‐ethylhexyloxy)‐benzo[1,2‐b:4,5‐b']dithiophene‐2,6‐diyl‐alt‐4‐(2‐ethylhexyloxy‐1‐one)thieno[3,4‐b]thiophene‐2,6‐diyl]:[6,6]‐phenyl‐C71‐butyric acid methyl ester (PBDTTT‐C:PC71BM) bulk‐heterojunction organic solar cells. We modulate the active‐layer density of states by varying the polymer:fullerene composition over a small range around the ratio that leads to the maximum solar cell efficiency (50–67 wt% PC71BM). Using transient and steady‐state techniques, we find that nongeminate recombination limits the device efficiency and, moreover, that increasing the PC71BM content simultaneously increases the carrier lifetime and drift mobility in contrast to the behavior expected for Langevin recombination. Changes in electronic properties with fullerene content are accompanied by a significant change in the magnitude or energetic separation of the density of localized states. Our comprehensive approach to understanding device performance represents significant progress in understanding what limits these high‐efficiency polymer:fullerene systems. 相似文献