氯酸钠晶体生长的手性对称破损研究

我们使用非搅拌的氯酸钠晶体水溶液,研究了晶体的手性对称破损问题.氯酸钠晶体溶液是通过溶解分析纯 NaClO3 粉末于去离子水中配制而成.采用 Mach-Zehnder 干涉方法和称重法测定晶体的溶解度.使用偏光显微镜鉴定了11545颗晶体的手性.这些晶体是从不同pH条件下的90个自发成核和生长实验中获得.实验结果表明:溶液的pH值可影响到氯酸钠晶体的手性分布.晶体手性分布的pH效应,可用随机动力学理论和胚晶凝聚二次成核理论来定性解释.     

基于ISIGHT的二维手性声子晶体带隙最优设计

本文首先利用有限元仿真软件COMSOL计算了二维手性声子晶体的带隙,分析了散射体参数与韧带涂层参数变化对带隙的影响规律。在此基础上,确定手性声子晶体带隙最优设计的有效参数设计空间;然后基于ISIGHT优化设计平台嵌入遗传算法,开展二维手性声子晶体带隙的最优设计。在带隙的最优设计过程中,先以二维手性声子晶体的有效构型参数为设计变量,相对带隙宽度最大为目标,设计手性声子晶体单胞构型。再以此优化单胞构型为初始构型,以手性声子晶体的有效材料参数为设计变量,相对带隙宽度最大为目标,进一步实现二维手性声子晶体带隙的最优设计。本工作极大限度地挖掘了二维手性声子晶体带隙最优设计潜能,为充分发挥手性声子晶体在减振降噪中的作用提供了可靠有效的分析设计方法。     

单一手性层状钴有机膦酸配合物的结构和性质

基于手性有机膦酸配体(3-phenyl-2-[(phosphonomethyl)amino]propanoic,2-ppapH3)和辅助含氮配体(1,3-di(4-pyridyl)propan,1,3'-dpp)合成得到一对对映体纯的钴有机膦酸配合物R(S)-Co3(2-ppap)2(1,3'-dpp)2(H2O)2·2H2O(R-1 or S-1).该配合物晶体显示了层状结构,其中{Co1O4N2}八面体,{Co2O3N2}和{Co3O3N2}三角双锥分别与{PO3C}四面体的三个角连接,形成了含有八元环的无机金属链.这些无机金属链通过1,3'-dpp交联,在ac平面上形成分子层.同时研究了配合物R-1和S-1的热稳定性和手性光学活性.     

液晶冠醚的混合物研究

液晶冠醚在1982年出现以来，由于其同时具有冠醚和液晶所具有的性质，已越来越受琶人们的重视。作为液晶类的冠醚化合物，已在仿生物膜，手性识别，显示取向，分子离子器件等方面显示出很强的应用前景。液晶冠醚的应用，要求具有恰当的液晶温度范围，但在液晶冠醚的合成设计中，     

非手性型单壁碳纳米管的对称性分析

碳纳米管有着奇特的物理性质和化学性质,该性质与其特有的几何结构有着密切的关系.本文由点群理论出发,分析了非手性型即锯齿型(n,0)和扶手椅型(n,n)单壁碳纳米管所属的点群,并对这两种类型的单壁碳纳米管的对称元进行总结.分析出n为奇数与偶数时它分属两个不同的点群.并列举了n分别取6和5时(6,0),(6,6)与(5,0),(5,5)型单壁碳纳米管分别所属的点群为D6h和D5d,并给出相应的特征标表.     

力学所发明自组装制备手性可控纳米碳管新方法

<正>纳米碳管作为潜在的第三代晶体管,其手性决定其表现出的金属导体或半导体性能。然而,如何制备手性可控的纳米碳管,成为制约纳米碳管在微纳电子、集成电路等领域应用的关键问题。国外最新实验研究表明:石墨烯纳米条带在纳米碳管的辅助下,可以自组装形成螺旋结构,有趣的是部分实验中发现了自组装纳     

新型全氟苯环乙炔类手性液晶化合物的合成及相变性质研究

本文报道了两大类液晶核中心含有柔顺亚甲氧基的四氧苯环乙炔类手性液晶化合物合成及相变性质，讨论了不同末端基团、桥键对液晶相变性的影响。     

二维碳化物晶体V2C MXene的制备与性能研究进展

V2C MXene是新型类石墨烯二维碳化物MXene的重要成员.相对于最常见的Ti3 C2 MXene,V2CMXene更难制备,但是在某些领域,具有更好的性能.本文综述V2CMXene的制备方法、性能以及应用方面的研究进展.通过对比几种V2C的制备方法,总结出相对温和、简便且较为经济的制备高纯度V2C MXene方法.分析目前所制备的V2CMXene的结构与性能,介绍其电化学性能、催化、吸附、热稳定性、光电特性等.总结V2C MXene的应用,重点探讨V2C MXene在电化学领域的应用,并且展望其在更多领域的重要应用.     

多孔石墨烯的制备及应用

多孔石墨稀是石墨稀的一种新型衍生物,是指在石墨烯的二维基面上具有纳米级孔道的碳材料.由于多孔石墨烯具有优异的电化学性能,其在多个领域得到广泛的关注.文中主要对多孔石墨烯的一些物理化学特性、制备方法和技术、以及所涉及应用领域等方面的研究进展进行了总结和展望.     

电化学法制备石墨烯基复合材料及其在超级电容器中的研究进展

石墨烯及其复合材料作为一种新型功能材料在能量存储领域受到广泛的关注.电化学制备技术相比于其他的制备手段具有安全、高效、绿色的优点.本文综述了电化学法制备石墨烯/纳米金属复合材料、石墨烯/金属氧化物(氢氧化物)复合材料、石墨烯/聚合物复合材料等的研究进展及其在超级电容器上的应用,以期为电化学制备石墨烯及其复合材料在超电领域的研究提供参考.     

Chiral symmetry breaking in unstirred crystallization

Statistics of nucleation of chiral forms of sodium bromate from unstirred aqueous solutions was studied. It was established that bimodal, trimodal and unimodal distributions of enantiomers are obtained in unstirred crystallization. It was also found out that probabilities of the creation of L or D crystals and racemates R, as well as the presence of D, L, and R peaks in distributions depend on crystallizer size, supersaturation and temperature. Nucleation at low supersaturations in small, closed crystallizers leads to the formation of pure enantiomers, and to bimodal distributions with D and L peaks at any temperature. At high supersaturations in large, open crystallizers the formation of racemates and unimodal distributions with racemate R peaks results. In open crystallizers at the lowest temperatures and at the highest temperatures used in crystallization from aqueous solution racemates of sodium bromate are preferentially formed, but in a wide range of intermediate‐temperatures apart from racemates, pure enantiomers are efficiently formed which leads to trimodal distributions. The spontaneous formation of pure enantiomers in crystallization from unstirred, unseeded solutions is caused by the chiral symmetry breaking phenomenon, the same as that discovered in stirred crystallization. The conservation of chiral symmetry is, in unstirred crystallization, one of the two possibilities, and the other one is the breakage of symmetry. Both of them occur in nature. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Chiral resolution in bent-core nematic liquid crystals

This paper presents the currently available experimental evidence for the occurrence of chiral resolution in bent-core nematic liquid crystals. The observation of chiral domains in these systems is discussed in context with other indications for the unique character of the nematic phase in bent-core materials, which challenge our understanding of nematic phase behaviour. Two possible mechanisms for the emergence of macroscopically chiral domains are exposed; the spontaneous resolution of chiral bent-core conformers and the occurrence of helical twist bend deformations due to a unique propensity for spontaneous bending of the nematic director in bent-core materials. The latter proposition is put into context with the recently developed cluster model, as overall it appears more appropriate to consider bent-core nematic systems as self-assembling-self-organising fluids with a hierarchical domain structure.     

Chiral phases in a system of biaxial molecules

Chiral phases in a system of biaxial molecules are investigated based on a theory of biaxial liquid crystals, which we have presented in past work. Four chiral phases are identified, corresponding to a uniaxial nematic phase, two biaxial nematic phases, and a discotic phase, respectively. We find that in the chiral uniaxial nematic phase, the pitch of the chiral structures does not depend on temperature. In contrast, in the two chiral biaxial nematic phases, as well as in the chiral discotic phase, the pitch is temperature-dependent.     

手性大孔磷酸镓Hit-5的水热合成与晶体结构

本文采用水热合成法制备了一个三维手性大孔开放骨架磷酸镓Ga16P16O75·4[1,6-C6H18N2]·[C2H10N2]·2H2O(简称Hit-5).反应起始原料摩尔配比为:1 GaOOH:15 H3PO4:7.5 H2N(CH2)6NH2:0.5 C2H8N2:555 H2O.Hit-5属正交晶系,P21212空间群,晶胞参数:a=0.8671(1)nm,b=1.7945(1)nm,c=0.9101(1)nm,β=108.33(1)°,V=1.3443(2)nm3,Z=4.Hit-5的骨架是由Ga3P3六聚体和Ga4P4八聚体两个不同的二级结构单元通过共顶点联接构成三维纳米孔结构,在[001]方向呈现16-元环孔道.     

A de Vries (SmC*) Phase in a Novel Series of Chiral Fluorinated Organosiloxane Liquid Crystals

The synthesis and characterization of a series of five chiral fluorinated low molar mass (bifurcated tail) organosiloxane materials is presented. The mesogenic moiety is similar to that in the TSiKN65F mesogen reported by Naciri et al., which displays a de Vries-type SmA* phase. The one parameter varied across the series reported herein is the length of the alkyl chain linking the mesogen's core to the bifurcated siloxane tail. One of the five materials displays a de Vries SmC* phase upon cooling from SmA*.     

New Chiral Esters,Diastereomeric 2-(4-Carboxybenzylidene)-p-Menthane-3-One Derivatives,as Components of LC Systems with Induced Helical Structure

Abstract

Diastereomeric 1R, 4S- and 1R, 4R-2-carbomethoxybenzylidene-p-menthane-3-ones have been synthesized. The helical twisting power and the induced helical pitch temperature dependence have been measured for the liquid crystal mixtures based on the nematic 4-methoxybenzylidene-4′-butylaniline and 4-pentyl-4′-cyanobiphenyl containing the obtained diastereomeric chiral dopants. The distinction in the characteristics of the diastereomeric chiral dopants is discussed.     

Electro-Optical Properties of Electric Field-Induced-Polymer Stabilization at Blue Phase of Chiral Nematic Liquid Crystal

Polymer stabilization of the blue phase induced a wide temperature range of more than 60 K, but the high driving voltage and the large switching hysteresis compared to the low molecular weight blue phase of the chiral nematic liquid crystal. In this study, we newly proposed electric field-induced-polymer stabilization of blue phase (EFIPSBP) which the electric field was applied to the blue phase during polymer stabilization and investigated the driving voltage and the switching hysteresis using various voltage-applied EFIPSBP cells. We confirmed that the driving voltage and the switching hysteresis of the EFIPSBP cell were decreased compared to those of conventional polymer stabilized BP at 8OCB chiral nematic liquid crystal mixture. This could be suggested as a potential method for improving the driving voltage and the switching hysteresis of conventional polymer stabilized BP.     

Crystal Structures of D-N-(2-Adamantyl)phenylglycinol and L-N-(2-Adamantyl)diphenylphenylalinol: Chiral Amino Alcohols Utilized as Ligands for Catalytic Asymmetric Hydroamination

Amino alcohols are important ligands for the asymmetric catalytic hydroamination of aminoallenes to form chiral pyrrolidines. Herein, we report the crystal structures of two chiral amino alcohols, D-N-(2-Adamantyl)phenylglycinol and L-N-(2-Adamantyl)diphenylphenylalinol, that function as ligands within transition metal complexes that catalyze the hydroamination of aminoallenes. Both molecules crystallize in the noncentrosymmetric orthorhombic space group P2₁2₁2₁. Inter- and intramolecular hydrogen bonding plays an important role in stabilizing each alcohol in the solid state in the absence of a transition metal. The presence of these hydrogen bonds has been verified by single crystal X-ray diffraction and their overall strength determined by computational methods.