Electro-optical properties cholesteric liquid of polymer stabilized crystal film＊

Liquid crystals （LCs） and polymers are extensively used in various electro-optical applications. In this paper, normal mode polymer stabilized cholesteric LC film is prepared and studied. The effects of chiral dopant and monomer concentrations on the electro-optical properties, such as contrast ratio, driving voltage, hysteresis width and response time, are investigated. The reasons of electro-optical properties influenced by the concentrations of the materials are discussed. Through the proper material recipe, the electro-optical properties of polymer stabilized cholesteric LC film can be optimized.

Electro-Optical Properties of Carbon Nanotubes Obtained by High Density Plasma Chemical Vapor Deposition

In this work, we studied the electro-optical properties of high-aligned carbon nanotubes deposited at room temperature. For this, we used the High Density Plasma Chemical Vapor Deposition system. This system uses a new concept of plasma generation: a planar coil is coupled to an RF system for plasma generation. This was used together with an electrostatic shield, for plasma densification, thereby obtaining high-density plasmas. The carbon nanotubes were deposited using pure methane plasmas. Three methods were used for the surface modification of the sample: reference substrate (silicon wafer only submitted to a chemical cleaning), silicon wafer with surface roughness generated by plasma etching, silicon wafer with a thin iron film and silicon wafer with diamond nano powder used as precursor materials. For each kind of silicon wafer surface, the carbon nanotubes were deposited with two different deposition times (two and three hours). The carbon nanotubes structural characteristics were analyzed by Atomic Force Microscope and Scanning Electronic Microscope. The carbon nanotubes electrical characteristics were observed by Raman Spectroscopy and the carbon nanotubes electro-optical properties were analyzed by current vs voltage electrical measurements and photo-luminescence spectroscopy measurements. The photoelectric effect in the carbon nanotubes were determined by photo-induced current measurements. In this work, we obtained carbon nanotubes with semiconductor properties and carbon nanotubes with metallic properties. The electro-optical effects depend strongly on the substrate preparation and the deposition parameters of the carbon nanotubes. The carbon nanotubes are high aligned and show singular properties that can be used for many applications.

Electro-optical properties of high birefringence liquid crystal compounds with isothiocyanate and naphthyl group

Liquid crystal（LC） compound with isothiocyanate and naphthyl group is an attractive high birefringence LC material,and can be used in optical devices. In this paper, the electro-optical properties of a series of this type of LC compounds were investigated. The melting points and enthalpy values of these LC compounds were higher than those of corresponding compounds with the phenyl group. These compounds exhibited high birefringence with a maximum value of 0.66. Fluorine substitution in the molecular almost does not affect the birefringence value. When these LC compounds with the naphthyl group were dissolved in a commercial LC mixture, the electro-optical properties depending on temperature were investigated. In the low-temperature region, LC mixtures with the naphthyl-group LC compounds exhibited higher viscosity than pure commercial LCs. In the high-temperature region, viscosity values very closely approached each other. When response performance was investigated, figure-of-merit（FoM） values were measured. The Fo M values of LC mixtures containing LC compounds with naphthyl group were lower than those of reference benzene LCs in the low-temperature region. However, in the high-temperature region, the results were reversed. These isothiocyanate LC compounds with naphthyl group can be applied in special fast-response LC device, particularly the ones used under high-temperature conditions.

Electro-optical properties and(E,F) phase diagram of fluorinated chiral smectic liquid crystals

Fluorinated smectic liquid crystals each with a biphenyl benzoate rigid core are investigated. Molecular structures of the studied compounds have difference only in fluorine position and the length of the carbon chain. Dielectric relaxation study and electro-optical measurements are carried out with the classical SSFLC geometry. The field-induced phase transitions are studied and the（E,T） phase diagram is established.

All-optical switching and nonlinear optical properties of HBT in ethanol solution

This paper demonstrates an all-optical switching model system comprising a single pulsed pump beam at 355 nm and a CW He-Ne signal beam at 632.8 nm with 2-（2＇-hydroxyphenyl）benzothiazole （HBT） in ethanol solution. The origins of the optical switching effect were discussed. By the study of nonlinear optical properties for HBT in ethanol solvent, this paper verified that the excited-state intramolecular proton transfer （ESIPT） effect of HBT and the thermal effect of solvent worked on quite different time scales and together induced the change of the refractive index of HBT solution, leading to the signal beam deflection. The results indicated that the HBT molecule could be an excellent candidate for high-speed and high-sensitive optical switching devices.

Sol-Gel Processed Indium-Doped Zinc Oxide Thin Films and Their Electrical and Optical Properties

Transparent conducting films of zinc oxide and indium-doped zinc oxide have been prepared by a simple and economical sol-gel technique. This process is feasible for the fabrication of high quality TCO thin films when the processing parameters are optimized. It was found that the out-diffusion of oxygen during the vacuum annealing step was a crucial factor to prepare thin layer with superior properties. Annealing lowers the resistivity down to 4.7 10-3?Ω&#183cm for the 1 at.% doped films due to the liberation of high-valency In-dopants and the enhanced film density. At high indium concentrations, the free electron density stabilizes because an increasing number of dopant atoms form some kinds of neutral defects. The neutralized indium atoms do not contribute free electrons. The feasibility to deposit highly transparent ZnO thin films has been demonstrated.

Crystal Growth, Thermal, Mechanical and Optical Properties of a New Organic Nonlinear Optical Material: Ethyl P-Dimethylamino Benzoate (EDMAB)

An organic material, namely, ethyl p-dimethylamino benzoate was crystallized for the first time by solution growth technique using pure and mixed solvents. Growth kinetics and morphology changes with solvents were investigated based on solute –solvent interactions of pure and mixed solvents. An appropriate mixed solvent for high quality crystals with well-defined morphology is reported. The absence of solvent molecules and the presence of various functional groups of the grown sample were qualitatively confirmed by FTIR spectroscopic studies. Thermal properties of the grown sample were analyzed by TG and DTA analysis. Mechanical properties of the EDMAB crystal were investigated by micro hardness studies. Moreover, the grown crystal shows high transparency in the visible and near IR regions. The material shows relatively high SHG efficiency than that of KDP.

SYNTHESIS AND PROPERTIES OF POLYACETYLENES CONTAINING CARBAZOLE AND AMINO ACID MOIETIES

Novel 9-proparylcarbazole monomers containing amino acid moieties,2-N(tert-butoxycarbonyl)-L-alanine- 9-proparylcarbazole ester(1),2-N-(tert-butoxycarbonyl)-L-O-cyclohexyl-L-glutamic acid-9-proparylcarbazole ester(2) and 2-N-(tert-butoxycarbonyl)-L-phenylalanine-9-proparylcarbazole ester(3) were synthesized and polymerized with (nbd)Rh^+[η~6-C_6H_5B^-(C_6H_5)_3]to give the corresponding polymers with number-average molecular weights ranging from 7050 to 10500 in 70%-86%yields.The polymers were completely so...

Effects of morphology and concentration of CuS nanoparticles on alignment and electro-optic properties of nematic liquid crystal

Nanoparticles （NPs） with flower-like and frame morphologies were synthesized from CuS, a remarkable transition-metal sulfide. We introduced two kinds of CuS NPs into a nematic liquid crystal （LC） 4-cyano-4＇-n-pentylbiphenyl （5CB） and investigated the morphology- and concentration-dependent alignment and electro-optic （E-O） effects of CuS NPs on 5CB. A trace amount of flower-like CuS NPs induced a uniform homeotropic orientation of LC molecules; this is attributable to the obtained desirable compact nanosheet structure. Moreover, both flower-like and frame CuS NPs induced a remarkable improvement in the E-O properties of 5CB, and the flower-like CuS/5CB system exhibited a better performance. The doped CuS NPs in the LC host suppressed the shielding effect and strengthened the electric field, resulting in outstanding E-O properties. At a doping concentration of 0.05 wt.%, CuS NPs were well-dispersed and achieved the optimum E-O performance. This study provides a novel method for inducing a uniform orientation and enhanced E-O properties of LC molecules by doping with extraordinary CuS NPs, leading to potential applications in establishing flexible LC displays.

Facet-dependent electro-optical properties of cholesteric liquid crystals doped with Cu2O nanocrystals

Excellent electro-optical （E-O） performances are essential for high-quality reflective cholesteric liquid crystal （LC） displays, but are often limited by the high driving voltages required by these displays. Dispersing functional nanomaterials into the LCs has emerged as a promising approach to achieve outstanding E-O properties. In this work, we report the facet-controlled E-O properties of a chiral nematic LC （N＊LC） doped with cubic, octahedral, and rhornbic dodecahedral Cu20. The outstanding E-O properties of the doped systems are related to the interaction between the liquid crystals and Cu20 dopants with different exposed crystal planes. Doping with octahedral and rhombic dodecahedral Cu20 reduces the stability of the planar state, as a result of both the surface abundance of active Cu atoms that interact with the polarized LC molecules, and the large amounts of vertexes and edges on the crystal surfaces, which accelerate the transition from the planar to the focal conic state under an applied electric field. Rhombic Cu20 is the most effective dopant for improving the E-O properties of the present LCs, resulting in a 65.31% reduction of the threshold voltage. The facet and morphology effects highlighted in this work provide a new pathway to develop excellent energy-saving meso-materials with exposed high-reactivity facets, improving their potential applications in electro-optical technologies and information displays.

An investigation on a novel PDLC film's fabrication and its electro-optical properties

A polymer dispersed liquid crystal (PDLC) film that has good electro-optical properties is produced by the method of polymerized-induced phase separation. Based on the application foreground, its capability parameters, such as contrast ratio, work voltage, and visual angle, are characterized for the first time by a white light but not a fixed wavelength light. The results show the PDLC film has a low work-voltage of 20 V, more than 150° visual angle, high stability, and long lifetime. The differences between plastic and glass ITO-coated substrates of PDLC films are also studied in this paper. The plastic substrate has better property and will have a wider perspective especially in the portable, tender and folded display devices. Due to adjustable properties of film by electric field, PDLC has the potential application for display device, sensor, switch, grating, and new generation analytical apparatus.

羟基和交联剂对PDLC膜电-光性能的影响

通过选用含有羟基的丙烯酸酯类单体制备聚合物分散液晶(PDLC)膜,研究了羟基的存在和不同的制膜工艺条件对PDLC膜电-光性能及稳定性的影响。通过分别添加具有刚性和柔性的交联剂,使羟基参与交联,研究了PDLC膜电-光性能及稳定性的变化规律。研究表明向单体中添加含有羟基的分子结构不同的丙烯酸酯,可提高PDLC膜中聚合物网络与两片ITO膜之间的结合力,降低PDLC膜的驱动电压。添加柔性交联剂二异氰酸己酯对PDLC膜的稳定性和黏结性影响较小,适量添加二异氰酸己酯可在保持一定对比度的情况下降低PDLC膜的驱动电压。

添加液晶对PDLC膜电-光性能参数的影响

以甲基丙烯酸β羟乙酯为聚合单体,以SLC7011-100为液晶材料,利用紫外光聚合分相法制备了PDLC薄膜。通过调节单体和液晶成分的比例,在尽可能提高膜的对比度的情况下降低驱动电压,以获得电-光性能良好的PDLC膜。分别向体系添加壬烷氧基和癸烷氧基联苯氰基液晶、烷基联苯氰基类液晶5CB和8CB,考察了PDLC膜电-光性能的变化,结果表明,添加液晶的含量和分子结构对PDLC膜的折射率、对比度等电-光性能参数有较大影响。

种子层及掺杂浓度对溶胶-凝胶法制备ZnO∶Al薄膜光电性能的影响

本文采用溶胶-凝胶法以提拉的方式在普通玻璃基底上制备出n型掺杂具有优良光电性能的氧化锌掺铝（AZO）薄膜,并以磁控溅射AZO薄膜为种子层引导液相法所制备AZO薄膜生长。Al掺杂浓度区间为0.25at%～5.00at%。通过X射线衍射仪、场发射扫描电子显微镜、轮廓仪、方块电阻测试仪、霍尔效应测试仪、紫外-可见-红外分光光度计分别研究了薄膜物相、微观结构、膜厚及光电性能,进一步分析了Al掺杂浓度、种子层对薄膜光电性能的影响。结果表明：经10次提拉所制备薄膜可见光透过率85%以上。Al掺杂浓度、种子层的引入对AZO薄膜的光电性能有重要影响。无种子层时,掺杂浓度为0.50at%的AZO薄膜在5%H2、95%N2还原气氛下于550℃保温60 min得到最优电学性能,方块电阻约为166Ω/□,电阻率约为1.99×10-3Ω·cm;预镀AZO种子层所制备薄膜方块电阻下降到约42Ω/□,电阻率下降到约7.56×10-4Ω·cm。

1-(反式-4-烷基环己基)-苯基-2-含氟苯基取代乙炔类液晶的合成与性能

以烷基环已酮和溴苯为起始原料,通过格氏反应、氢解、傅克酰化、维格特氧化、乙酰氯加成、脱氯化氢等9步反应,合成了末端为4-F、3,4-F,F、3-F及3,5-F,F基团的4个1-(反式-4-烷基环己基)-苯基-2-含氟苯基取代乙炔类液晶化合物,总收率为6.7%～7.6%,产物结构经IR,1HNMR确认.其中氯代二芳基取代乙烯(Ⅷ)的合成采用简便的乙酰氯加成反应得到,使反应缩短了两步.化合物添加到液晶的基础配方中,能同时改善基础配方的低温和高温性能,提高其双折射率,增加响应速度.

ZIF-8对向列相液晶电-光性能的提升（英文）

ZIF-8(沸石咪唑酯骨架结构材料)是一种金属有机物骨架结构材料,因其极高的比表面积、出色的热稳定性而被广泛应用于各种性质研究中。ZIF-8通过传统的水热法在甲醇溶液中合成,其颗粒尺寸约为250nm,形貌为菱形十二面体。研究发现,合成的ZIF-8材料具有良好的热稳定性及相当大的比表面积。将其掺杂进液晶中会增强液晶的电-光性能,增强效果与掺杂浓度有关。在向列相液晶4-氰基-4′-戊基联苯(5CB)中,ZIF-8可以吸附杂质离子,抑制屏蔽效应,最终使液晶驱动电压降低,响应加快。在掺杂浓度为0.05%(w,质量分数)时,液晶体系的电-光性能改善最明显,阈值电压(V_(th))最小达到0.92 V,饱和电压(V_(sat))达到1.31 V,响应时间仅为10.04 ms。而当掺杂浓度大于0.05%(w)时,ZIF-8在液晶盒中发生团聚,影响液晶分子的有序排布,同时吸附杂质离子减少,不利于液晶电-光性能的改善。

聚合物分散液晶PMMA-5CB的制备及电光性能

以聚合引发相分离的方法制备了聚甲基丙烯酸甲酯（PMMA）基聚合物分散液晶（PDLC）。通过差示量热扫描仪（DSC）、偏光显微镜（POM）对不同液晶5CB（4-氰基-4′-戊基联苯）含量的PDLC热力学行为和液晶分散状态进行了表征。在电压为0~30 V、波长为633 nm处,用紫外可见分光光度计（UV-Vis）对PDLC的电光性能进行了研究。结果表明当w（5CB）达到20%以上时,PDLC发生相分离现象;当w（5CB）=30%时,液晶的分散状态最佳,电光效应最强。

基于ZnTe_(1-x)Y_x(Y=O,S,Se)中间带光伏材料光电性能的第一性原理研究

采用基于密度泛函理论框架下的第一性原理方法计算了高失配三元合金ZnTe1-xYx(Y=O,S,Se)的能带结构、电子特性与光学性能。通过对半导体态密度的计算证实了在闪锌矿结构的ZnTe中掺杂O、S或Se原子可能得到独立的中间带结构,该结构可提高光伏材料对能量低于母体半导体带隙光子的吸收效率。研究结果表明,中间带在ZnTe1-xOx中是由掺杂的O原子的2p态与处于导带的Zn原子的4s态耦合而成,符合能带反交叉模型。另外,与ZnTe1-xSx和ZnTe1-xSex相比,随着掺杂O浓度的变化,ZnTe1-xOx的中间带表现出较高的稳定性主要是因为O与Te之间存在最大的电负性差。

基于芴和2，4-二氟苯的寡聚物的合成与表征

为了对比不同分子结构的芴类寡聚物在光物理性质上的差异,将9,9-二(十二烷基)-芴(F1)和2,4-二氟苯硼酸通过Suzuki偶联反应合成并表征了一系列寡聚物:2-(2,4-二氟苯)-9,9-二(十二烷基)-芴(FF1)、2,7-二(2,4-二氟苯)-9,9-二(十二烷基)-芴(FF2)、二-(2-(2,4-二氟苯基)-9,9-二(十二烷基)-芴)-7-(2,4-二氟苯)-9,9-二(十二烷基)-芴(FF3)以及1-溴-3,5-二(2-(2,4-二氟苯)9,9-二(十二烷基)-芴)-苯(FF4)。依照F1,FF1,FF2和FF3的次序,由π-π*跃迁导致的最大紫外吸收依次红移,而寡聚物FF4的最大紫外吸收相对于寡聚物FF3要蓝移,其薄膜的最大荧光发射相比于寡聚物FF3要红移。这说明分子的线形、支化结构和由此引起的聚集态结构的变化对其光物理性能都有重要影响。密度泛函理论计算和实验结果基本一致。通过光降解实验还发现含氟寡聚物具备较好的光稳定性。

液晶电光效应探究性试验

液晶电光效应是液晶材料在电场作用下发生的一种特色光学现象,这种现象在显示技术、光通讯、无损检测、电子录像和核磁共振等领域有着广泛的应用。文章介绍了液晶电光效应的原理及其特性,在此基础上通过试验验证了液晶的电光特性,以期为液晶材料及其相关行业的发展提供借鉴。