4－戊基－4＇－氰基联苯液晶的分子二阶非线性光学极化率测量方法

在玻璃衬底上制得单层硬脂酸的Ｌａｎｇｍｕｉｒ－Ｂｌｏｄｇｅｔｔ（ＬＢ）膜，做为４－戊基－４＇－氰基联苯（５ＣＢ）液晶的取向层，在取向层上旋涂一层５ＣＢ液晶，用透射二次谐波方法测量出５ＣＢ液晶分子二阶非线性光学极化率，其值为β＝７×１０－２９ｅｓｕ．对比文献值，测量得到的结果符合较好．     

利用核磁共振氢谱的哈勒分析获得分子序列取向参数

本文通过全氢液晶材料的核磁共振氢谱（¹H NMR）的哈勒关联研究推测了分子序列取向参数,包括随温度变化的双峰距离及全谱图的半高峰宽.通过哈勒拟合并外推所得到的4'-正戊基-4'-氰基联苯（5CB）和混合液晶E7分子取向参数,与其它方法获得的取值一致.     

相位延迟法平行排列丝状液晶在静磁场中扭曲效应研究

对平行排列5CB（4′-n-penty1-4-cyanobinpheny1)丝状液晶在静磁场中扭曲变形做了严格的数值解,给出了严格分布情况;利用光学“4*4”矩阵算法,计算了线偏振光在严格分布下的传输情况;在实验方面,应用光学相位延迟法对平行排列5CB丝状液晶在静磁场中（温度27℃）线偏振光的通过情况进行了测量.理论计算和实验结果说明在非长螺距近似条件下可用线偏振光对平行排列丝状液晶的物理性质进行实验研究.     

纳米级润滑膜分子排列取向的拉曼光谱表征技术

利用激光拉曼散射技术,对剪切作用下受限于钢球与石英盘之间的纳米级液晶5 CB的分子排列取向进行研究. 结果表明,在特定的实验条件下,可以得到高信噪比的纳米级润滑膜的拉曼散射信号(20∶1). 同时发现,当激光偏振方向与剪切运动方向平行(垂直)时,所得拉曼信号强度达到最大(小)值,表明纳米级液晶5 CB分子在剪切诱导作用下,沿剪切运动方向趋于定向排列. 另外,当钢球与石英盘之间的剪切速度逐渐增大时,受限的纳米级液晶5 CB的拉曼信号强度也逐渐增大. 最后,利用根据相对光强干涉原理研制的纳米膜厚测量仪对纳米级 关键词： 薄膜润滑 分子排列取向 拉曼散射     

电场作用下5CB液晶分子的近壁面层黏弹性的QCM研究

利用石英晶体微天平(quartz crystal microbalance,QCM)研究了电场对5CB液晶分子的近壁面层黏弹性的影响.对QCM结果的分析发现,电场作用对液晶的黏度影响分为两部分,通过建立含吸附膜的双层膜模型,分析了QCM的两部分结果,发现电场对近壁面吸附层及体相层的影响是不同的.根据QCM的双层膜模型,对近壁面层液晶分子的黏弹性及膜厚进行了定量的分析计算,结果表明5CB在石英晶体上电极附近有一层约100nm厚的近壁面吸附层,其复剪切黏度随电场强度的增加而减小,这与5CB液晶的体相黏度变化规 关键词： 5CB液晶 石英晶体微天平 近壁面 黏弹性     

聚甲基丙烯酸肉桂酰氧基乙酯的光化学反应在液晶分子排列取向中的作用

研究了光聚合物材料聚甲基丙烯酸肉桂酰氧基乙酯(CEMC)对液晶材料LC-6710A的取向作用,取向层表面在光化学反应前后的变化;测量了光控取向膜液晶盒中液晶分子的预倾角及单面光控取向扭曲向列液晶显示器(TNLCD)的电光特性和时间响应特性,研究了这种材料的光化学反应过程,以及液晶分子排列取向的机理.     

新显色剂四(4-甲氧基-4-磺酸基苯基)卟啉与Fe~(3+)的高灵敏反应的研究与应用

本文提出以四 (4 -甲氧基 - 4 -磺酸基苯基 )卟啉 (p- OCH3TPPS4 )为显色剂 ,在 p H=3.5— 5 .5的条件下测定痕量铁的新体系 ,络合物最大吸收波长为 4 4 6nm,表观摩尔吸收系数ε=2 .0× 10 4 L· mol-1· cm-1,Fe3+ 在 0— 10 μg/ 2 5 m L 范围内符合比耳定律 ,应用本法测定花生仁皮中铁 ,回收率可达 95 .0 %—10 8.4 %     

4-硝基-4′-氨基偶氮苯的光学性质研究

采用紫外可见吸收和二次谐波产生技术研究了“推-拉”型偶氮苯分子Langmuir-Blodgett(LB)膜的光谱和二阶非线性光学特性.4-硝基-4′-氨基偶氮苯(NAA)分子能制成很好的LB多层膜,在稀溶液中以单体的反式异构体形式存在,在膜中主要以J-聚集体的形式存在,LB膜的紫外可见吸收谱的吸收峰较之溶液的发生了52 nm的红移.NAALB膜的二阶非线性极化率χ(2)为19.59×10－8 esu,一阶超极化率β值较大,约为1.974×10－29 esu.其光学二阶非线性起源于电偶极子机制.     

Meso-5,10,15,20-四(4-甲氧基苯基)卟啉荧光熄灭法测定铅

基于铅对荧光试剂 Meso- 5 ,10 ,15 ,2 0 -四 (4 -甲氧基苯基 )卟啉 (TMOPP)的荧光熄灭 ,建立了测定微量铅的荧光分析方法。在 p H9.5的 Tris- HCl缓冲体系中 ,最大激发波长和发射波长分别为 4 2 4 nm和6 5 7nm,测定铅浓度的线性范围为 5 .5 0× 10 -7— 7.5 0× 10 -5mol/ L,检出限为 8.5 0× 10 -8mol/ L。用于环境水样中铅含量的分析 ,结果满意。     

4-(2-羟基-4-硝基苯偶氮)-1-苯基-3-甲基吡唑啉酮光度法测定烟草中镁

研究了 4 - (2 -羟基 - 4-硝基苯偶氮 ) - 1-苯基 - 3-甲基吡唑啉酮 (HNAPMP)与镁的显色反应 ,在 p H=10的硼砂 -氢氧化钠缓冲介质中 ,HNAPMP与镁反应生成 2∶ 1稳定络合物 ,λmax=5 2 2 nm,ε=3.5 8× 10 4L·mol-1· cm-1。镁含量在 0— 2 0 μg/2 5 m L范围内符合比耳定律 ,方法用于烟草样品中镁含量的测定 ,结果令人满意     

Influence of the flow on the anchoring of nematic liquid crystals on Langmuir-Blodgett monolayers studied by optical second-harmonic generation

The influence of capillary flow on the alignment of the nematic liquid crystal 5CB on fatty acid Langmuir-Blodgett monolayers was studied by optical second-harmonic generation (SHG). The surface dipole sensitivity of the technique allows probing the orientation of the first liquid crystal monolayer in the presence of the liquid crystal bulk. It was found that capillary flow causes the first monolayer of liquid crystal molecules in contact with the fatty acid monolayer to be oriented in the flow direction with a large pretilt (78 degrees), resulting in a quasi-planar alignment with splay-bend deformation of the nematic director in the bulk. The large pretilt angle also suggests that the Langmuir-Blodgett film itself is affected by the flow. The quasi-planar flow-induced alignment was found to be metastable. Once the flow ceases, circular domains of homeotropic orientation nucleate in the sample and expand until the whole sample becomes homeotropic. This relaxation process from flow-induced quasi-planar to surface-induced homeotropic alignment was also monitored by SHG. It was found that in the homeotropic state the first nematic layer presents a pretilt of 38 degrees almost isotropically distributed in the plane of the cell, with a slight preference for the direction of the previous flow. Received 8 November 2000 and Received in final form 12 March 2001     

聚酰亚胺LB膜上液晶表面锚定的研究

通过测试光延迟研究了聚酰亚胺ＬＢ膜的光学各向异性，分析了在ＬＢ膜成膜过程中成膜分子的流动取向特性，并研究了液晶的表面锚定能，分析了ＬＢ膜上液晶的取向机制．聚酰亚胺ＬＢ膜的链段的取向程度较强摩擦情形的聚酰亚胺表面的链段取向要差．强摩擦的聚酰亚胺会比聚酰亚胺ＬＢ膜具有更好的排列液晶分子的能力．ＬＢ膜的流动取向模式使得聚酰亚胺成膜分子沿拉伸方向形成一定的有序排列，并诱导液晶分子定向排列，液晶和聚合物分子相互作用是液晶表面排列的主要动力 关键词：     

Molecular organization and aggregation in Langmuir and Langmuir-Blodgett films of azo dye/liquid crystal mixtures

A study of azo dye/liquid crystal mixtures in monolayers formed at air-water (Langmuir films) and air-solid substrate (Langmuir-Blodgett films) interfaces was performed. Three azo dyes with various molecular structure and two liquid crystal materials: 4-octyl-4′-cyanobiphenyl (8CB) and trans-4-octyl(4′-cyanophenyl)-cyclohexane (8PCH) were used. The morphology of Langmuir films was monitored by means of a Brewster angle microscope (BAM). Moreover, a surface pressure and electronic absorption spectra of the monolayer spread on the water surface of dye/liquid crystal mixtures as a function of a mean molecular area were simultaneously recorded. In addition, the absorption for Langmuir-Blodgett films deposited on quartz plates was measured. Information about intermolecular interactions in the mixtures of the nonamphiphilic dye and the liquid crystal with polar terminal group was obtained. Conclusions about the formation of self-aggregates between dye molecules have been drawn. The influence of the dye molecular structure and its concentration on aggregates’ geometry was found.     

Solid-state morphology of aromatic-aliphatic polyester crystallized from smectic liquid crystal

The solid-state morphology of poly(hexamethylene p,p'-bi-benzoate) (BB-6) and its dependence on the texture of the smectic liquid crystal state from which it crystallized were studied using electron microscopy, polarizing optical microscopy, and small-angle x-ray diffractometry. Thin films of BB-6 suitable for the microscopy were prepared by casting a hot solution of the polymer in tetrabromoethane onto mica at 150°C. The as-cast film of BB-6 was first heated to 260°C, maintained in the smectic range (210°C), and then cooled gradually to room temperature. A number of types of defect structures—such as Dupan cyclides, edge dislocation, tilt walls, and disclinations — were observed in the solid BB-6 formed from the smectic melt. On the basis of the electron microscopy and small-angle x-ray diffractometry, it is suggested that folded-chain crystals are formed during the crystallization from the smectic melt. Electron microscopic observations of the solid BB-6 and its orientation behavior under shear can be reasonably explained by assuming the presence of a precursory chain-folded layer structure in the smectic liquid crystal of BB-6.     

Langmuir-Blodgett film and nematic interface

The orientation induced by a Langmuir-Blodgett film on a Nematic Liquid Crystal (NLC) is theoretically analyzed. We show that the effective surface energy is due to different contributions connected with steric and van der Waals interactions between the nematic and the solid substrate. The analysis shows that the Langmuir-Blodgett film orientation depends on the surface density of the molecules. The initial homeotropic orientation may become unstable giving rise to a tilted film. The average orientation of the nematic molecules is also analyzed. We show that, in the event in which the steric interaction Nematic-Langmuir-Blodgett film is very large with respect to the dispersion interaction Nematic-Substrate, the nematic orientation coincides with the one of the film. On the contrary, when the two interactions are comparable, the orientation of the two media may differ. In particular, we analyze how the stable orientation depends on the surface molecular density of the film.     

Crystal growth of small-molecule organic semiconductors with nucleation additive

In this study, we employ a nucleation additive 4-octylbenzoic acid (OBA) with an optimized solvent evaporation method to regulate crystal orientation and grain width of small-molecule organic semiconductors. When 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) was utilized as a benchmark material to mix with the additive, a self-assembled OBA interfacial layer was formed and promoted uniform deposition of nucleation seeds. As a result, the TIPS pentacene/OBA blend crystalline film exhibited crystal alignment in long range order, attributing to a 11-fold reduction of the crystal misorientation angle and a 4-fold increase of the grain width. We further discussed the important correlation between the effective hole mobility, grain boundaries, grain width and length, and nucleation sites. Organic thin film transistors were fabricated to test charge transport, yielding a hole mobility of up to 0.17 cm²/V. This work provides a new pathway to modulate the nucleation and crystallization events of organic semiconductors, and can potentially be applied to optimize the thin film morphology and electrical performance of organic semiconducting materials in general.     

La,V共掺杂的Bi_4Ti_3O_(12)铁电薄膜的溶胶-凝胶法制备及性能测试

采用溶胶-凝胶(sol-gel)工艺在Pt/TiO2/SiO2/p-Si(100)衬底上制备出Bi4Ti3O12(BIT)和Bi3.25La0.75Ti2.97V0.03O12(BLTV)铁电薄膜,研究了La,V共掺杂对BIT薄膜的晶体结构和电学性能的影响.BIT薄膜为c轴择优取向,BLTV薄膜为随机取向,拉曼光谱分析表明V掺杂降低了TiO6(或VO6)八面体的对称性,也增强了Ti—O键(或V—O键)杂化.BLTV薄膜的剩余极化Pr为25.4μC/cm2,远大于BIT薄膜的9.2μC/cm2,表现出良好的铁电性能.疲劳、漏电流测试显示BLTV薄膜具有优良的抗疲劳特性和漏电流特性,表明La,V共掺杂能有效地降低薄膜中的氧空位.     

InP在两种化学腐蚀系统中的腐蚀特性

本文研究了各种浓度的Br2:CH3OH和Br2:HBr:H2O两种腐蚀系统分别对用负性KPP和正性AZ1350J光致光刻胶直接掩蔽[001]InP的腐蚀特性。分别给出了腐蚀速率与溴浓度,腐蚀深度与时间的关系曲线。同时从结晶学角度定性解释了腐蚀速率与溴浓度,腐蚀方向与腐蚀图形的依赖关系。     

Self-aggregates formation of tetrachloroperylene acid esters in Langmuir and Langmuir-Blodgett films

Using Langmuir and Langmuir-Blodgett techniques molecular films of chlorinated perylene derivatives, namely tetra-n-butyl-1,6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxylate (PCn for n = 1, 5, 9) have been studied. The Langmuir films of pure compounds and mixed with liquid crystalline 4-octyl-4′-cyanobiphenyl (8CB) were characterized by surface pressure-mean molecular area isotherms. An additive rule reveals miscibility of all the dyes with 8CB but shows different types of intermolecular interaction forces. The pure and mixed Langmuir films were transferred onto quartz plates and characterized spectroscopically. Absorption and fluorescence spectra were recorded for the samples in form of diluted chloroform solution, the dye with 8CB mixtures in monomolecular Langmuir-Blodgett films and in liquid crystal cells. Different tendency to aggregation of the dye with short and long alkyl chains was observed. It is shown that the dye molecule stacking and aggregation of the chlorinated perylene dyes depend on the dye concentration and are related to the torsion of the perylene core.     

Synthesis of ZnAl2O4/α-Al2O3 complex substrates and growth of GaN films

With the solid phase reaction between pulsed-laser-deposited (PLD) ZnOfilm and α-Al2O3 substrate, ZnAl2O4/α-Al2O3 complex substrates were synthesized. X-ray diffraction (XRD) spectra show that as the reaction proceeds, ZnAl2O4 changes from the initial (111)-oriented single crystal to poly-crystal, and then to inadequate (111) orientation. Corresponding scanning electron microscope (SEM)images indicate that the surface morphology of ZnAl2O4 transforms from uniform islands to stick structures, and then to bulgy-line structures. In addition, XRDspectra present that ZnAl2O4 prepared at low temperature is unstable at the environment of higher temperature. On the as-obtained ZnAl2O4/α-Al2O3 substrates, GaN films were grown without any nitride buffer using light-radiation heating low-pressure MOCVD (LRH-LP-MOCVD). XRD spectra indicate that GaN film on this kind of complex substrate changes from c-axis single crystal to poly-crystal as ZnAl2O4 layer is thickened. For the single crystal GaN, its full width at half maximum (FWHM) of X-ray rocking curve is 0.4°. Results indicate that islands on thin ZnAl2O4 layer can promote nucleation at initial stage of GaN growth, which leadsto the (0001)-oriented GaN film.