Effect of ZnO film thickness on the performance of organic light emitting diodes

The electrical and optical properties of the ZnO layers and of the ITO/ZnO bilayers are investigated. We show that a ZnO layer of about 120 nm is the best compromise to obtain simultaneously a high transmittance and conductivity. Moreover an X-ray diffraction analysis underscores that an amorphous ITO deposited on a polycrystalline ZnO could change into a polycrystalline ITO. The modifications of the ITO layer by a preliminary deposition of a 120 nm thick ZnO underlayer enables us to decrease the threshold voltage of organic light emitting diodes.     

Interaction of liposomes with silica nanocapsules: from lipid bilayer coating to multi-liposomal composites

A new delivery system has been developed that combines liposomes and silica nanocapsules. It was found that in the presence of cationic unilamellar liposomes, silica nanocapsules are instantly coated with a lipid bilayer. In contrast, cationic stealth liposomes modified with polyethylene glycol can adsorb on the surface of silica to form multi-liposomal composites in which the liposomes remain intact.     

FTIR and Raman analysis of l‐cysteine ethyl ester HCl interaction with dipalmitoylphosphatidylcholine in anhydrous and hydrated states

Interactions of l ‐cysteine ethyl ester hydrochloride (CE), a bioactive cysteine derivative, with dipalmitoylphosphatidylcholine (DPPC) were investigated. To gain a deeper insight into analyzing l ‐cysteine ethyl ester HCl interaction with liposomes of DPPC in anhydrous and hydrated states, we performed experimental studies by infrared (Fourier transform infrared spectroscopy) and Raman spectroscopies. The results revealed that the interaction of CE with the phospholipid head groups was the same in absence or presence of water. In both states, the wavenumber of the PO₂⁻ group and C N bond of the choline group decreased. This behavior can be ascribed to the replacement of hydration water and binding to the phosphate group. In the Raman spectrum results for the anhydrous and gel states, the S H stretching band of the CE shifted to lower frequencies with a decrease in its force constant. Biologically active lipophilic molecules such as CE should be studied in terms of their interaction with lipid bilayers prior to the development of advanced lipid carrier systems such as liposomes. The results of these studies provide information on membrane integrity and physicochemical properties that are essential for the rational design of lipidic drug delivery systems. Copyright © 2015 John Wiley & Sons, Ltd.     

Induction of B1, B6 and Biaxial Smectic A Phases in Binary Mixtures of Compounds with Rod-Like and Bent-Core Molecules

Abstract

We have studied a binary mixture of compounds, one of which has rod-like molecules and the other bent-core molecules. The rod-like molecules are biphilic in nature with a long alkoxy chain attached to an aromatic moeity only at one end, and exhibit the bilayer SmA₂ phase, even though they do not have the highly polar cyano or nitro groups. The compound with bent-core molecules exhibit the B₂ phase which has polarized layers with tilted molecules. Three liquid crystalline phases are induced in the binary mixtures, depending on the concentration: the 2-dimensionally ordered B₁ phase for compositions with 15 to 63 mol% of the rod-like molecules and the B₆ phase for 63 to 87 mol%. The sequence obtained on increasing the concentration of rod-like molecules is the same as that seen on shortening the chain length of the BC molecules. Between 87 to 95.5 mol% of the rod-like molecules, a new biaxial smectic A₂ (SmA_2b ) phase is induced. On the basis of several observations, we argue that it corresponds to a structure in which the BC molecules are reoriented with their arrow directions pointed along the layer normal. The SmA₂ to SmA_2b transition corresponds to an orientational transition of the bent-core molecules in the anisotropic SmA₂ background medium.     

Effect of a nonuniform magnetic field on the Landau states in a biased AA-stacked graphene bilayer

We study the Landau states in the biased AA-stacked graphene bilayer under an exponentially decaying magnetic field along one spatial dimension. The results show that the energy eigenvalues of the system are strongly dependent on the inhomogeneity of the magnetic field and the bias voltage between the graphene layers, and in particular the reordering and mixing of finite Landau states could occur. Moreover, we also demonstrate that the current carrying states induced by the decaying magnetic field propagate vertically to the magnetic-field gradient within the graphene sample and can be further modulated by the bias voltage between the layers.     

Wrinkling of a bilayer resting on a soft substrate under in-plane compression

The wrinkling problem of a bilayer film resting on a soft substrate under in-plane compression is investigated via theoretical analysis and numerical simulations. Such a system may undergo two different wrinkling modes, namely surface wrinkling of the top single layer on a composite substrate or bilayer wrinkling on a homogeneous substrate, depending on the geometric and material parameters. In the present paper, a theoretical solution is first derived for the former case, while a solution available in the literature is applied for the latter. The solution derived here can degenerate both to the classical solution for a stiff layer resting on a semi-infinite soft substrate and that for a stiff layer lying on a compliant substrate of finite thickness. A series of finite element simulations are performed to demonstrate the accuracy of the theoretical solution. In addition, it is found that, at a given compressive strain, a certain change in the elastic modulus of the intermediate layer may lead to a dramatic surface pattern transformation between the two wrinkling modes, indicating a novel approach to realise surface pattern switching.     

三维各向异性超常媒质交错结构的亚波长谐振特性研究

以填充各向异性超常媒质矩形波导中的电磁场解为基础,通过建立与求解填充各向异性超常媒质交错结构的矩形谐振腔的谐振方程,深入研究了三维各向异性超常媒质交错结构的亚波长谐振特性.结果发现,三维各向异性超常媒质交错结构的亚波长谐振条件具有更为多样性的物理解,在固定参数下,其物理解的个数往往超过一个,还针对谐振结构的横向尺寸对亚波长谐振条件的影响进行了讨论.结果表明,随着横向尺寸的减小亚波长谐振条件的物理解数量将逐渐增多直至趋于无穷.这意味着即使超常媒质的本构参数无法控制,仍然可以通过调节谐振结构的横向尺寸来得到亚波长谐振腔. 关键词： 各向异性 超常媒质 交错结构 亚波长谐振     

H-bond refinement for electron transfer membrane-bound protein–protein complexes: Cytochrome c oxidase and cytochrome c552

In this study we propose a protocol to evaluate membrane-bound cytochrome c oxidase–cytochrome c552 docking candidates. An initial rigid docking algorithm generates docking poses of the cytochrome c oxidase–cytochrome c552, candidates are then aggregated into a 512-DPPC membrane model and solvated in explicit solvent. Molecular dynamic simulations are performed to induce conformational changes to membrane-bound protein complexes. Lastly each protein–protein complex is optimized in terms of its hydrogen bond network, evaluated energetically and ranked. The protocol is directly applicable to other membrane-protein complexes, such as protein–ligand systems.     

Molecular dynamics simulation of nonsteroidal antiinflammatory drugs,naproxen and relafen,in a lipid bilayer membrane

Naproxen and relafen, as nonsteroidal antiinflammatory drugs, were simulated in neutral and charged forms and their effects on a lipid bilayer membrane were investigated by molecular dynamics simulation using Groningen machine for chemical simulations software (GROMACS). Simulation of 10 systems was performed, which included different dosages of the drug molecules, naproxen and Relafen, in charged and neutral forms, and a mixture of naproxen and Relafen in neutral forms. The effects of the mixture and the individual drugs' dosages on membrane properties, such as electrostatic potential, order parameter, diffusion coefficients, and hydrogen bond formation, were analyzed. Hydration of the drugs in the membrane system was investigated using radial distribution function analysis. Using fully hydrated dimyristoylphosphatidylcholine (DMPC) as a reference system, 128 lipid molecules and water molecules were simulated exclusively, and the same simulation technique was performed on 10 other systems, including drug mixtures and a DMPC membrane. Angular distributions of lipid chains of the membrane were calculated, and the effects of the drug insertion and chain orientation in the membrane were evaluated. © 2013 Wiley Periodicals, Inc.