新型隔层材料LB交替多层膜的二次谐波研究

有机光学非线性材料在光计算和光通讯领域中有着非常广泛的应用前景［1，2］．非中心对称结构是二阶非线性光学器件的基本要求之一，对于有机两亲光学活性分子而言，使用能够在分子尺度上实现有序组装的Langmuir－Blodgett（LB）技术，可以制备具有稳定而非中心对称结构的多层膜．一般说来，Y型结构的多层膜比X型或Z型更稳定．然而，由单一材料组成的Y型LB多层膜只能形成中心对称结构，因而对宏观二阶非线性极化率X（2）没有贡献．为了解决稳定性与非中心对称性的矛盾，我们可以将光学非线性活性材料（如半花菁染料）与非活性隔层材料…     

10-烃基吖啶酮的非线性光学活性研究

随着激光技术应用的发展,非线性光学材料的研究不断深人［'j,目前倍频效应和短的截止波长的倍频材料是二阶非线性光学有机材料研究的热点之一L'．现有的非线性光学有机材料,如偶氮苯、共轭烯烃与SChiff碱等类化合物,因分子具有较大的共轭长度使其吸收多处于可见光区,不适合于半导体激光等向蓝紫激光倍频"·"．0'（暖酮含有大。共轭结构,分子两端同时连有吸电子基团。X一0）和推电子基团（＞N-R）而发生分子内的电荷转移,使分子具有非线性光学活性"－·这类化合物结构简单,并有很好的光稳定性,且该类化合物最大紫外吸收在385～40…     

溶致变色法测定BMC和MMONS的分子二阶极化率

1引言分子二阶极化率是对倍频材料进行分子设计和优化筛选的重要参量，因而对它的测量也是十分重要的．用直接测量的“电场诱导二次谐波产生（EFISH）”法需要昂贵的设备，在普通实验室难以普及．近年来人们推出了简便易行的溶致变色法测定分子二阶极化率，可得出与EFISH法相平行的结果．本文采用这种方法测定了BMC（4-溴-4’-甲氧基查耳酮）和MMONS（3-甲基-4-甲氧基-4’-硝基二苯乙烯）的分子二阶极化率，并根据有关晶体二阶非线性光学数据和CNDO／S-CI方法结合微扰理论分别计算了它们的β值，得出了与溶致变色法基本一致的结果…     

聚合物非线性光学材料

最近,有机非线性光学材料已引起了人们极大的兴趣。一些可极化有机分子具有很大的分子超极化率,可惜,受晶体对称性的限制仅有少数晶体具有二阶非线性光学效应。极化聚合物可以产生统计非中心对称的环境,使材料的二阶特性显示出来。本文在简单介绍了有机非线性光学和极化的原理后,综述了聚合物二阶非线性光学材料的研究进展。此外,对聚合物的三阶非线性光学效应的研究也作了介绍。     

“推—拉”型偶氮苯分子的光谱性质和二阶非线性光学性质

研究了具有“推－拉”电子结构的４‘－（Ｎ，Ｎ－二羟乙基）氨基４－硝基偶氮苯（Ｒ－ＨＡＮＢ）衍生物的光谱性质和二阶非线性光学性质，Ｒ－ＨＡＮＢ是一类假芪型偶氮苯分子其激发态具有相似的能级结构，且在不同状态下均具有较高的二阶非线性光学活性，其粉末二次谐波信号多数强于分散红１，一阶超极化率与基太偶极矩动量 合量用溶为色法测得为〉３．４×１０＾８２Ｃ＾２ｍ＾４／Ｖ＾２，其５％掺杂聚甲基丙烯酸甲酯薄膜以电晕     

有机分子膜层间相互作用对聚集体的影响

有机材料在分子设计与合成方面具有高度可塑性、灵活性及多样性,易于制成各种功能器件．带有电子给体和受体以及、电子体系的两亲类有机分子具有极高的超分子极化率“‘．利用Langmuir－Blodgett（LB）技术可实现有机材料在纳米尺寸上的分子组装,形成高度有序、非中心对称的LB膜以实现大的宏观二阶非线性极化系数．有机分子在LB膜中常常形成聚集体,而聚集体的存在将显著改变膜的宏观光学特性．根据有机分子间相互作用能的类型,聚集体可以分为J一型和H一型两种,分别表现为它们的吸收或荧光光谱‘”相对于单体发生红移或蓝移．近年来…     

(4,5-二氮杂-9-亚芴基)碳60中的分子轨道相互作用及其电子光谱和二阶非线性光学性质

在ZINDO方法基础上,按完全态求和(SOS)公式编制了计算分子二阶非线性光学系数β的程序.研究了(4,5-二氮杂-9-亚芴基)碳60中的分子轨道相互作用,计算了该分子的电子光谱和二阶非线性光学系数,前者与实验结果较好地吻合,后者属于理论预测性质.     

2,4,6-三苯乙烯基均三嗪（TSTA）的结构及其光学性质

制备了2，4，6一三苯乙烯基均三嗪（TSTA）的晶体，用四圆X射线衍射法测得 该晶体属于正交晶（No.36），晶体结构不仅非中心对称，而且具有极性，分子构 型为微弯曲的平面三角形．该化合物独特的分子结构和晶体构导致了其二阶非线性 光学效应，在1064nm ps脉冲基频光下，测得其粉末的倍频光强度为尿素的1.8倍有 很好的透明性（最长波长吸收峰位于322nm）和较好的热稳定性（熔点为225-227℃ ）     

4, 5-二(2', 4'-二硝基苯硫基)-1, 3-二杂环戊烯-2-酮(BNPT-DTO), 4, 5-二(2', 4'-二硝基苯硫基)-1, 3-二杂环戊烯-2-硫酮(BNPT-DTT)分子及晶体激光倍频性质的理论研究

在ZINDO方法的基础上, 按完全态求和公式编制了计算分子的二阶非线性光学系数张量元βijk的程序, 并以此为基础计算了BNPT-DTO, BNPT-DTT分子二次谐波条件下的二阶非线性光学系数, 从分子水平研究了其分子的光学倍频性质及分子倍频与晶体宏观倍频的关系, 计算结果较好地说明了实验现象。     

4, 5-二(2', 4'-二硝基苯硫基)-1, 3-二杂环戊烯-2-酮(BNPT-DTO), 4, 5-二(2', 4'-二硝基苯硫基)-1, 3-二杂环戊烯-2-硫酮(BNPT-DTT)分子及晶体激光倍频性质的理论研究

在ZINDO方法的基础上, 按完全态求和公式编制了计算分子的二阶非线性光学系数张量元βijk的程序, 并以此为基础计算了BNPT-DTO, BNPT-DTT分子二次谐波条件下的二阶非线性光学系数, 从分子水平研究了其分子的光学倍频性质及分子倍频与晶体宏观倍频的关系, 计算结果较好地说明了实验现象。     

Mass transfer limitations at crystallizing interfaces in an atomic force microscopy fluid cell: a finite element analysis

Although atomic force microscopy (AFM) has emerged as the preeminent experimental tool for real-time in situ measurements of crystal growth processes in solution, relatively little is known about the mass transfer limitations that may impact these measurements. We present a continuum analysis of flow and mass transfer in an atomic force microscope fluid cell during crystal growth, using data acquired from calcium oxalate monohydrate (COM) crystal growth measurements as a comparison. Steady-state flows and solute concentration fields are computed using a three-dimensional, finite element method implemented on a parallel supercomputer. Steady-state flow results are compared with flow visualization experiments to validate the model. Computations of the flow field demonstrate how nonlinear momentum transport alters the spatial structure of the flow with increasing flow volume, altering mass transport conditions near the AFM cantilever and tip. The simulations demonstrate that the combination of solute depletion from crystal growth and mass transfer resistance lowers the solute concentration in the region between the tip and the crystal compared with the solute concentration at the inlet of the AFM cell. For example, using experimentally measured growth rates for COM, the solute concentration in this region is 3.1% lower than the inlet value because the solute consumed by crystal growth beneath the AFM tip cannot be replenished fully due to mass transport limitations. The simulations also reveal that increasing the flow rate through the cell does not affect this difference significantly because of the inherent shielding by the AFM tip in proximity with the crystal surface. Models such as the one presented here, used in conjunction with AFM measurements, promise more precise interpretations of measurement data.     

聚甲基丙烯酸甲酯单分子膜的原子力学显微镜研究

报道了利用原子力显微镜（ＡＦＭ）技术对聚甲基丙烯酸甲酯（ＰＭＭＡ）单分子膜进行分子结构水平的观察研究．由ＡＰＭ图像中得到的ＰＭＭＡ单体所占面积与用π－Ａ曲线中换算出液面上ＰＭＭＡＬａｕｇｍｕｉｒ膜中单体的面积符合得很好．从ＡＦＭ图像中可见ＰＭＭＡＬＢ膜中ＰＭＭＡ的线型碳链是与档板（ｂａｒｒｉｅｒ）平行的紧密排列，与ＬＢ提膜方向相垂直．并由此对ＰＭＭＡＬＢ膜的形成过程进行分析．此外，还观察到了在Ｓｉ基底上ＰＭＭＡ直链的卷绕伸直排列形态，初步分析了其形成原因．     

Buildup mechanism of carboxymethyl cellulose and chitosan self-assembled films

Films with different numbers of layers have been built by alternating the adsorption of carboxymethyl cellulose (CMC) and chitosan (CHI) at different pH levels. The adsorption process was recorded by quartz crystal microbalance (QCM). The results showed that under all pH conditions considered, the growth of the films is nonlinear. The film construction performed at pH 4.0 (preferred assembly pH) with different numbers of bilayers (CMC/CHI as one bilayer) was also observed step by step by atomic force microscopy (AFM). Comparing the growth process from QCM with the surface morphological changes from AFM shows the existence of an inhomogeneous structure for the first nine bilayers, and, after a coalescence of islands, an increase in the number of bilayers was demonstrated. The possible growth mechanism was also evaluated.     

Preparation of a novel self-assembling nonlinear optical (NLO) polymer film

A novel self-assembling crosslinking second harmonic generation nonlinear optical (SHG/NLO) film with high SHG coefficient (2×10-7 e.s,u.by IR dichroism) was prepared by morecular design and "in-situ poling and sol-gel process".The content of the NLO chromophore (S)-(-)-1-(4)-mtrophenyl-2-pyrrolidinemethanol (NPP) is as high as 50 mol% since NPP molecules probably disperse in the film at a molecular level The film is rigid,uni form and transparent.This designed clathrate supermolecular structure was poved by IR,atomic force microseopv (AFM) and differential scanning calorimetry (DSC) detection.The title film exhibits a long-term temporal stability with 95% of the initial value of SHG coefficient maintained even after 20 d at 65℃(by UV spectroscopy)     

Influence of Substrate-Target Distance on Structural and Optical Properties of Ga and (Al + Ga)-doped ZnO Thin Films Deposited by Radio Frequency Sputtering

Ga-doped ZnO and (Ga?+?Al) co-doped ZnO thin films were deposited on glass substrates by radio frequency magnetron sputtering for three distances d between a substrate–target. The influence of the distance between substrate–target upon structure, microstructure, vibrational properties, and optical band gap of the thin films was analyzed by X-ray diffraction, atomic force microscopy (AFM), Raman spectroscopy, and optical transmission measurements. The diffraction patterns revealed that the ZnO film crystallites are preferentially oriented with the (002) planes parallel to the substrate surface. AFM images show a smooth and uniform surface as well as a high compact structure. The Raman results reveal that the co-doping with Al?+?Ga introduces 2B₁(low) band and leads to the increase of intensity for longitudinal-optic’s band. In the visible region, the average value of the transmittance was above 80%.     

Polymer surface science

Molecular level studies of the structure and mechanical properties of polymer surfaces have been carried out by sum frequency generation (SFG) surface vibrational spectroscopy and atomic force microscopy (AFM). The surfaces of different grades of polyethylene and polypropylene have been characterized-including during the glass transition and when mechanically stretched. Copolymers that have hard and soft segments with different glass transition temperatures show phase separation, an effect of hydrogen bonding between the hard and soft segments, that influences their adhesive and friction properties. AFM and SFG show that low surface energy additives migrate to the surface and alter the surface mechanical properties. Polymers, where the chemical nature of the end groups is different from the backbone, show surface segregation of the hydrophobic part of the chain in air and the hydrophilic part in water. Likewise, in miscible polymer blends, surface segregation of the more hydrophobic component in air and the more hydrophilic component in water is observed. This area of surface science requires increased attention because of the predominance of polymers as structural materials and as biomaterials.     

Single—Molecular Imaging of Anticoagulation Factor I From Snake Venom by Atomic Force Microscopy

ＡｎｔｉｃｏａｇｕｌａｔｉｏｎｆａｃｔｏｒＩ (ＡＣＦＩ)ｆｒｏｍｔｈｅｖｅｎｏｍｏｆＡｇｋｉ ｓｔｒｏｄｏｎａｃｕｔｕｓｉｓａｂｉｎｄｉｎｇｐｒｏｔｅｉｎｔｏａｃｔｉｖａｔｅｄｃｏａｇｕｌａｔｉｏｎｆａｃ ｔｏｒＸ (ＦＸａ)ａｎｄｐｏｓｓｅｓｓｅｓｍａｒｋｅｄａｎｔｉｃｏａｇｕｌａｎｔａｃｔｉｖｉｔｙ .Ｓｉｎ ｇｌｅＡＣＦＩｍｏｌｅｃｕｌｅｈａｓｂｅｅｎｓｕｃｃｅｓｓｆｕｌｌｙｉｍａｇｅｄｉｎａｉｒｂｙｔａｐ ｐｉｎｇｍｏｄｅａｔｏｍｉｃｆｏｒｃｅｍｉｃｒｏｓｃｏｐｙ (ＡＦＭ )ｗｉｔｈｈｉｇｈ ｒｅｓ…     

聚乙烯醇(PVA)结晶的溶剂化效应

本文采用原子力显微镜和X射线粉末衍射仪研究了PVA溶液旋转涂膜的溶剂化效应。研究发现,随着DMSO（二甲基亚砜）／H2O的比例增加,膜表面形貌呈现规律性的变化。对薄膜的X射线衍射谱图分析表明,由于溶剂极性和溶剂中质子数的变化,导致薄膜内晶粒大小、结晶度不同,晶体结构的变化使得薄膜表面形貌也发生变化。     

芳基膦(胂)酸及其盐的合成、结构与倍频效应研究

本文基于将无机非线性光学材料的有效基团(畸变阴离子基团)及有机共轭体系结合为一体的设想,用改进的Doak-Freedman法合成了一系列芳基膦(胂)酸及其盐共25个化合物,讨论了分子的电子性质及其在晶体中的排列方式.实验结果表明,在这类化合物的分子内存在着一定的电荷转移;对甲苯膦酸的晶体结构分析表明,分子间存在着氢键作用,使分子呈二聚的排列方式.在所合成的化合物中,有6种表现出宏观倍频效应.     

用AFM研究DL-缬氨酸晶体的结构及其表面分子的排列

利用原子力显微镜(AFM)成像技术来观察DL-缬氨酸晶体表面分子的规则排列, 研究表明对映体分子在DL-缬氨酸晶体中相互配对排列, 每个晶胞单元中包含两个对映体分子, 属于具有中心对称结构 群, 整个晶体是消旋的. 通过原子力显微镜对DL-缬氨酸晶体表面重复单元的测量结果与X衍射数据对比, 发现用AFM观察到的DL-缬氨酸晶体中分子表面形貌的规整排列的距离, 同X衍射得出的三斜晶系晶胞参数数据基本一致, 由此判定该晶体属于三斜晶系而不是单斜晶系. 探讨了利用纳米技术的研究手段在分子水平研究生命起源中的手性问题, 在确定的晶面上通过分子周期性结构排列规律, 对DL-缬氨酸晶体表面分子进行手性识别.