Electronic properties of 2H-stacking bilayer MoS2 measured by terahertz time-domain spectroscopy

Bilayer (BL) molybdenum disulfide (MoS₂) is one of the most important electronic structures not only in valleytronics but also in realizing twistronic systems on the basis of the topological mosaics in moiré superlattices. In this work, BL MoS₂ on sapphire substrate with 2H-stacking structure is fabricated. We apply the terahertz (THz) time-domain spectroscopy (TDS) for examining the basic optoelectronic properties of this kind of BL MoS₂. The optical conductivity of BL MoS₂ is obtained in temperature regime from 80 K to 280 K. Through fitting the experimental data with the theoretical formula, the key sample parameters of BL MoS₂ can be determined, such as the electron density, the electronic relaxation time and the electronic localization factor. The temperature dependence of these parameters is examined and analyzed. We find that, similar to monolayer (ML) MoS₂, BL MoS₂ with 2H-stacking can respond strongly to THz radiation field and show semiconductor-like optoelectronic features. The theoretical calculations using density functional theory (DFT) can help us to further understand why the THz optoelectronic properties of BL MoS₂ differ from those observed for ML MoS₂. The results obtained from this study indicate that the THz TDS can be applied suitably to study the optoelectronic properties of BL MoS₂ based twistronic systems for novel applications as optical and optoelectronic materials and devices.     

Micro‐ and Nano‐Technologies for Lipid Bilayer‐Based Ion‐Channel Functional Assays

Ion channel proteins provide gated pores that allow ions to passively flow across cell membranes. Owing to their crucial roles in regulating transmembrane ion flow, ion channel proteins have attracted the attention of pharmaceutical investigators as drug targets for use in the studies of both therapeutics and side effects. In this review, we discuss the current technologies that are used in the formation of ion channel‐integrated bilayer lipid membranes (BLMs) in microfabricated devices as a potential platform for next‐generation drug screening systems. Advances in BLM fabrication methodology have allowed the preparation of BLMs in sophisticated formats, such as microfluidic, automated, and/or array systems, which can be combined with channel current recordings. A much more critical step is the integration of the target channels into BLMs. Current technologies for the functional reconstitution of ion channel proteins are presented and discussed. Finally, the remaining issues of the BLM‐based methods for recording ion channel activities and their potential applications as drug screening systems are discussed.     

双层金属纳米光栅的TE偏振光异常透射特性

根据在亚波长金属光栅表面添加电介质会引起TE偏振光的透射异常性, 应用严格耦合波理论和时域有限差分方法, 研究了双层金属纳米光栅在TE偏振光入射时产生的异常透射现象. 利用等效折射率方法建立了双层金属光栅的等效模型, 得到了TE偏振光透射率与聚合物的折射率、厚度以及金属层厚度的变化关系. 确认了结构中聚合物是透射异常出现的必要条件, TE偏振光以波导电磁模式在其中传播, 并认为类Fabry-Perot腔谐振是透射峰值产生的主要原因.     

Experimental and numerical approach on interfacial properties of W/Al bilayer films for electronic devices manufacturing

The aim of this article is to provide a systematic method for performing experimental tests and theoretical evaluations on interfacial adhesion properties of the W/Al bilayer thin films interface. Samples W/Al bilayer thin films assembly is deposited on the quartz glass by using radio frequency magnetron sputtering. Based on the analysis of the experimental indentation data, the elastic modulus and hardness of the sample are investigated. The test results show that both of the values are easily influenced by the indentation depth. At the meantime, a finite element model is built to simulate the interface mechanical properties. The analysis shows that stress is mainly centralized close to the indenter and the maximum stress occurs in the lower layer Al film, not in the upper W film. The comparison between the experiment and the simulation shows the validity of the test and the modeling of each other to a certain extent. The investigation builds a basis for future work such as the fabrication of W/Al bilayer thin films for micro/nano manufacturing.     

双层超晶格伊辛模型磁矩的性质

运用相关有效场理论推导出双层超晶格伊辛模型磁矩的计算公式,然后对蜂窝结构和正方结构模型的磁矩做了进一步的数值计算,并绘出相应的磁矩曲线,得到磁矩变化规律·     

Phase transitions in phosphatidylcholine foam bilayers

Foam bilayers from individual and mixed phosphatidylcholines are experimentally studied at different temperatures. Occurrence of a chain-melting phase transition in the foam bilayers is detected by two independent parameters—the critical concentrationC _c for formation of foam bilayer and the foam bilayer thickness. The data forC _c are discussed on the basis of the hole-nucleation theory, which applies the Ising model to foam bilayers and uses the mean-field approximation for interpretation of their stability. This allows the determination of the binding energy of a phospholipid molecule in gel and liquid-crystalline foam bilayers. New possibilities to relate the microscopic and macroscopic characteristics of foam bilayers are demonstrated.     

I–V characteristics and critical currents in superconducting/ferromagnetic bilayers

Current–voltage (I–V) characteristics and critical current density, J_c, for the onset of vortex motion were measured at different magnetic fields, H, and temperatures, T, in a superconducting (S)/ferromagnetic (F) bilayer and in a single Nb film. We choose Nb as a superconductor and a weak ferromagnetic alloy, Pd_1−xNi_x with x = 16, as F. We found that J_c was smaller for the S/F bilayer with respect to the single Nb film. The result was related to the reduced value of the superconducting order parameter in the bilayer.     

Phospholipid Bilayers as Molecular Models for Drug-Cell Membrana Interactions. The Case of the Antiinflamatory Drug Diclofenac

Phospholipids are amphipatic molecules with long hydrophobic acyl chains and zwitterionic polar heads which assemble into different types of molecular aggregates. The most relevant is the bilayer because of its relation with cell membranes, which are very complex entities. For this reason, simpler molecular models based on phospholipids bilayers are widely used. We have determined the bilayer structure of phospholipids located in the outer and inner monolayers of most cell membranes, and use them as molecular models to study the way different chemicals of biological interest interact with cell membranes. We present the results of our studies on the nonsteroidal anti-inflammatory drug diclofenac, from which little is known about its effects on human erythrocytes. This report presents the following evidence that diclofenac interacts with the human red cell membrane: a) X-ray diffraction and fluorescence spectroscopy of phospholipids bilayers show that diclofenac interacts with a class of lipids found in the outer moiety of the erythrocyte membrane; b) in isolated unsealed human erythrocyte membranes the drug induced a disordering effect on the acyl chains of the membrane lipid bilayer; c) in scanning electron microscopy studies on human erythrocytes it was observed that the drug induced morphological changes different from their normal biconcave shape.     

Influence of Naphthalene Moiety on Mesomorphism

Compounds containing naphthalene moiety are synthesized and the liquid crystalline properties studied by texture observations. The mesomorphic properties of these compounds are compared with related compounds to understand the influence of broad units such as naphthalene on mesomorphism. It is observed that there is a limit to which the end alkoxy group can be extended in a mesogen. The method of preparation, and properties of these compounds are given.