四苯基卟啉铜分子的扫描隧道显微镜成像

本文首次以ＬＢ技术将四苯基卟啉铜（ＣｕＴＰＰ）分子沉积到高定向热解石墨上，并用ＳＴＭ研究其表面形貌，得到了原子级分辨的ＣｕＴＰＰ分子的表面形貌图，结果表明，ＣｕＴＰＰ分子具有近似圆状平面结构，分子直径为１．０ｎｍ，与理论结果十分吻合，结合ＳＴＭ原理，讨论了有机大分子ＳＴＭ成像的条件。     

荧光探针技术在水溶液两亲分子有序组合体研究中的应用

总结了荧光探针技术在两亲分子有序组合体研究中的应用.在两亲分子有序组合体研究中,荧光技术的应用非常广泛.尤其是荧光探针技术的应用,为两亲分子有序组合体微观信息的获取提供了一个简单便利的渠道.根据荧光探针分子的荧光光谱,如最大发射波长、荧光强度及荧光寿命等参数,可以得到临界聚集浓度、微粘度、微极性等信息;根据探针的荧光猝灭,尤其是时间分辨荧光猝灭技术,可探测有序组合体的聚集数、聚集数变化相应的聚集体转化及表面电荷等信息.近年来发展起来的含荧光基团的两亲分子因其可以对聚集体微环境进行原位检测而引起了了广泛的关注.本文对上述几个方面的相关工作分别作了介绍.     

含Schiff碱基囊泡双分子膜的聚集结构与相变

研究表面活性剂分子在水溶液中的聚集行为对模拟生物膜功能和研究分子间相互作用具有重要意义"'．用于形成囊泡双分子层的表面活性剂主要是类似天然磷脂的双烷基链两亲分子,单烷基链两亲分子在引人刚性基团时亦可形成双分子膜k'．含SChiff碱基两亲分子在水溶液中的聚集性质及间、尾链长度对SChiff碱基构象的影响已有报道"'．本文报道了这类分子的另一种重要成膜性质,即改变制备条件,可选择性地得到不同聚集结构和相变温度的双分子膜·实验中所用成膜分子为：CH。（CH。）。;OPh-N-CH－PhO（CH;）n;N"（CH。）。Br－（m-4;n-…     

盐对刷型两亲聚合物聚集行为的调控作用

两亲聚合物奇异的功能特性源于分子独特的骨架结构和在溶液中的自组装聚集行为. 本文向以2-丙烯酰胺基-十二烷基磺酸(AMC₁₂S)与2-丙烯酰胺基-2-甲基丙磺酸(AMPS)进行无规共聚所制备的AMPS-AMC₁₂S刷型两亲聚合物溶液体系中引入不同用量的NaCl, 采用稳态荧光、动态光散射(DLS)和透射电子显微镜(TEM)系统考察NaCl 对聚合物聚集行为的调控作用. 研究发现, 聚合物结构中疏水侧链含量越低, NaCl 对聚集行为的调控作用越强; NaCl浓度增加会明显降低聚合物的临界聚集浓度; 与此同时, 聚合物分子链自组装由分子间的聚集方式向分子内的聚集方式转变, 形成的聚集形态由大型多分子聚集体变化为尺寸数百分之一的单聚体.     

基于全散射技术局域结构确定与凝聚态物质

原子或分子的堆积方式和元素分布是凝聚态物质的核心问题,而局域结构的精确测定则为揭示原子堆积方式和元素分布提供了重要手段。获得与化学成键直接关联的局域结构信息,是人们认识化学反应,理解功能材料设计结构本质的重要依据。基于全散射技术的原子对分布函数方法(PDF),通过考虑原子对间距的空间分布规律,为具有不同结晶状态和团聚方式的凝聚态体系提供了全尺度的结构信息。本文从介绍全散射和原子对分布函数方法的理论基础出发,根据凝聚态物质的聚集形态差异和结构化学特点,列举了近年来在研究凝聚态物质的原子对分布函数过程中,结合原位温度场、反向蒙特卡洛等方法获得的物质局域结构信息和短程到长程的结构演变。通过分析局域结构与长程结构的对比差异,从局域尺度的视角为研究凝聚态物质的化学反应、功能物性优化和外场响应提供了新的思路。     

Gemini表面活性剂分子结构对其水溶液中聚集行为的影响

Gemini表面活性剂是通过联接基团将两个具有亲水亲油性质的两亲结构单元在其亲水头基上或靠近亲水头基处以共价键方式连接而成的一类表面活性剂。这类表面活性剂由于联接基团的引入具有比传统单链表面活性剂更高的表面活性,同时分子结构中更多的可调控因素使其在水溶液中表现出更为丰富的自聚集行为,而且分子不同部位结构的改变对分子内或分子间相互作用产生不同的影响,可实现通过分子结构的设计有效调控其自聚集能力和聚集体结构。本综述将从联接基团、烷基链、亲水头基、反离子和其它功能性基团这五个方面概述近些年Gemini表面活性剂水溶液中聚集行为方面的研究进展,总结人们对Gemini表面活性剂分子间相互作用规律的认识,期望对于进一步发展这类高效的表面活性剂体系提供有益的帮助。     

荧光探针技术在两亲分子有序组合体研究中的应用

荧光技术具有灵敏度高、可测量参数丰富、扰动小、无破坏性等优点,因而在两亲分子有序组合体的研究方面得到极为广泛的应用。本文介绍了国内外利用各种荧光探针技术测定两亲分子有序组合体的微极性、微粘度、动力学过程、聚集数等微观信息,并对具有表面活性剂结构的荧光探针做了简要介绍,最后对基于荧光探针技术的两亲分子有序组合体的研究进行了展望。     

超临界正己烷—甲醇溶液体系的Monte Carlo模拟：浓度对溶液构型？…

用Ｍｏｎｔｅ Ｃａｒｌｏ分子模拟方法对正己烷－甲醇溶液体系处于临界状态时微观结构随浓度变化的情况进行了研究。模拟采用随机边界条件，得到了不同浓度条件下体系各基团的径向分布函数。结果表明，在溶液临界状态，正己烷分子有较强的聚集行为，随着溶液中甲醇浓度的变大，正己烷分子的聚集程度逐渐下降；甲醇分子周围正己烷分子的分布有一个最佳的浓度范围，在甲醇浓度为２２．５％时，配位数达到最大；超临界正己烷－甲醇溶液     

番红花红T与表面活性剂的作用及其在标记DNA中的应用

对阳离子染料番红花红Ｔ（ＳＴ）在阴离子表面活性剂存在时的溶液状态的吸收光谱和荧光光谱进行了研究。结果表明，低浓度阴离子表面活性剂与ＳＴ形成缔合物，导致ＳＴ的吸收与荧光强度降低；增大表面活性剂的浓度，其分子胶束前预聚集促使染料形成非荧光二聚体，导致荧光急剧猝灭，吸收光谱出现新的特征吸收峰；当表面活性剂浓度大于临界胶束浓度（ＣＭＣ）时，染料二聚体离解，ＳＴ单体增溶于胶团中形成新的高量子产率荧光体。本文     

双分子膜上染料的吸附性质及对膜结构的影响

系统地研究了染料甲基橙和达旦黄在含席夫碱基囊泡双分子膜阳离子表面上的吸附和聚集，以及由此产生的对膜聚集结构的影响，染料的吸附和聚集可经电子吸收光谱的因吸附产生的沉淀证实，并且ＭＯ的聚集结构的Ｈ－聚集，ＴＹ的聚集结构为Ｊ－聚集。改变ｐＨ的研究表明ＭＯ在变色ｐＨ值以及因形成阳离子而解聚，ＴＹ在酸性条件下亦因离子化程度减弱和部分质子化而使聚集被削弱，但在碱性条件下其聚集产生更大的红移。温度变化的结果显示     

萃取过程的量热研究(Ⅳ)——皂化P507萃取有机相中反向胶束和微乳状液的形成

利用量热滴定法研究皂化P507萃取有机相中反向胶束的形成和滴水过程中微乳状液的形成.求得临界胶束浓度、胶束形成常数K、聚集数n以及热力学函数,并用激光动态光散射仪测定胶团和微乳颗粒的流体力学半径。     

Scanning tunneling microscopy of lead selenide monocrystals and epitaxial layers on barium fluoride

Summary The topography and atomic arrangement on the (100) surface of n- and p-PbSe monocrystals have been studied in air by scanning tunneling microscopy (STM). It was shown that the chemically polished surface is more rough than the freshly cleaved one. The regular patterns of the atomic scale STM images correspond well to the crystallographic positions of atoms on (100) plane. Several types of surface defects were observed. The peculiarities of the registrations of atomic scale STM images of PbSe monocrystals are discussed. STM was also applied to structure analysis of molecular beam epitaxial layers of PbSe on BaF₂ substrate. The topography of epitaxial layers and their atomic structure have been visualized. It appeared that with certain substrate temperatures (100) and (111) oriented grains of PbSe are formed.     

STM study of morphology and electron transport features in cytochrome c and nanocluster molecule monolayers.

The morphology and electron tunneling through single cytochrome c and nanocluster Pt(5)(CO)(7)[P(C(6)H(5))](4) molecules organized as monolayer Langmuir-Blodgett (LB) films on graphite substrate have been studied experimentally using scanning tunneling microscopy (STM) and spectroscopy techniques with sub-nanometer spatial resolution in a double barrier tunnel junction configuration STM tip-monomolecular film-conducting substrate at ambient conditions. STM images of the films revealed globular structures with characteristic diameters (approximately 3.5 nm for the protein molecule and approximately 1.2 nm for the nanocluster). The spectroscopic study by recording the tunneling current-bias voltage (I-V) curves revealed tunneling I-V characteristics with features as steps of different width and heights that are dependent on the STM tip position over the molecule in the monolayer, giving evidence for sequential discrete electron-tunneling effects with the combination of the single electron Coulomb-charging energy and the electronic energy level separation (molecular spectrum) in such immobilized metalloprotein and nanocluster structures that can be of interest for the development of bioelectronic and hybrid functional nanosystems.     

SANS from Pluronic P85 in d-water

Small-angle neutron scattering (SANS) has been used to investigate Pluronic P85 (EO₂₆PO₄₀EO₂₆) copolymer in deuterated water. A range of P85 fractions were measured for a wide sample temperature window. A rich phase behavior is reported. Unimers were observed below the critical micelle formation condition. At fixed P85 fraction, a number of micellar phases were observed upon increasing temperature; first spherical micelles, then cylindrical micelles, then lamellar micelles. At the highest temperature, a demixed lamellae phase was observed. Analysis of the SANS data consisted in fits to an empirical Guinier-Porod model that was appropriate for data fitting in the various phases at low P85 fractions. When the P85 fraction increased, an inter-particle structure factor was included to analyze SANS data from concentrated spherical micelles. At high P85 fractions, paracrystalline structures were observed as evidenced by an enhanced inter-particle interaction peak. A phase diagram for P85/d-water was obtained showing the various phases. Focusing on the spherical micelles phase for one sample composition, a core-shell model was used to fit SANS data and obtain sizes and scattering length densities. Using material balance equations, information such as the aggregation number (i.e., number of Pluronic macromolecules per micelle) and the number of hydration water molecules in the shell region are determined.     

Visualizing electron correlation by means of ab initio scanning tunneling spectroscopy images of single molecules

Scanning tunneling microscopy (STM) has been a fundamental tool to characterize many-body effects in condensed matter systems, from extended solids to quantum dots. STM of molecules decoupled from the supporting conductive substrate has the potential to extend STM characterization of many-body effects to the molecular world as well. In this paper, we describe a many-body tunneling theory for molecules decoupled from the STM substrate, and we report on the use of standard quantum chemical methods to calculate the quantities necessary to provide the "correlated" STM molecular image. The developed approach has been applied to 18 different molecules to explore the effects of their chemical nature and of their substituents, as well as to verify the possible contribution by transition metal centers. Whereas the bulk of calculations has been performed with the configuration interaction method with single and double excitations (CISD), because of the computational cost some tests have been also performed with the more accurate coupled cluster with single and double excitations (CCSD) method to quantify the importance of the computational level on many-body STM images. We have found that correlation induces a remarkable squeezing of the images, and that correlated images are not derived from Hartree-Fock HOMO or LUMO alone, but include contributions from other orbitals as well. Although correlation effects are too small to be resolved by present STM experiments for the studied molecules, our results provide hints for seeking out other species with larger, and possibly experimentally detectable, correlation effects.     

Interpretation of high-resolution images of the best-bound wetting layers on Pt(111)

Two interpretations have been proposed of dark triangles observed in scanning tunneling microscopy (STM) images of the best bound, √37×√37-R25.3°, and √39×√39-R16.1° periodic water monolayers on Pt(111). In one, a "Y"-shaped tetramer of water molecules is removed, leaving a vacancy island behind; the other assumes the Y is replaced by a hexagon of H(2)O molecules, amounting to a di-interstitial. Consistent only with the di-interstitial model are thermal desorption and CO coadsorption data, STM line scans, and total energies obtained from density functional theory calculations.     

Graphene功能分子在HOPG上自组装结构的密度泛函研究

Graphene自组装超分子结构,是指FTBC-Cn(n=4,6,8,12)分子有序自组装在高定向裂解石墨(HOPG)上形成的自组装超分子结构,是一种新型二维固体表面材料.其中FTBC-Cn分子是由三角形扶手椅型graphene每边添加2条含有n(n=4,6,8,12)个C原子的烷基链所形成具有曲面结构的一种分子.采用...     

Hourglass‐Shaped Dendrimers on Surfaces: A Comparison of Different Scanning‐Tunneling‐Microscopy Approaches

Large molecules adsorbed on surfaces can be analyzed by scanning tunneling microscopy (STM) under various environmental conditions: on a dry surface in air or vacuum, and at the solid‐liquid interface. However, can measurements under dissimilar conditions be compared, e. g., when sample A was studied at the solid‐liquid interface and sample B in a dry environment? Only rarely can the same substance be examined with more than one approach, since completely different set‐up and preparations are necessary. Furthermore, few substances are suitable for several methods of sample preparation and characterization. We have chosen a large, flexible, nonplanar molecule, namely an alkoxy‐substituted second‐generation dendritic compound with a chiral core unit, which is peculiar for its ‘hourglass' conformation. The assembly properties have been explored by STM both in solution‐cast self‐organized monolayers (SOMs) and multilayer films, as well as at the solid‐liquid interface. The complexity and limits of the three approaches applied to our hourglass‐shaped dendritic compound are discussed. Depending on the approach and environmental conditions, several quality levels of image resolution could be achieved; measurements carried out at low temperatures led to highest resolution on the aromatic parts of the molecule. A comparison of equally sized images obtained under these varying conditions reveals not only different packing arrangements, but also spots of unlike shape. Therefore, when the approach, preparation, and/or environmental conditions are not the same, STM measurements of different compounds have to be compared with greatest care.     

Scanning tunneling microscope imaging of (CH3S)2 on Cu(111)

Scanning tunneling microscope (STM) images of isolated molecules of dimethyl disulfide, (CH(3)S)(2), adsorbed on the Cu(111) surface were successfully obtained at a sample temperature of 4.7 K. A (CH(3)S)(2) molecule appears as an elliptic protrusion in the STM images. From density functional theory calculation, it was suggested that the bright part in the protrusion corresponds to the molecular orbital which is widely spread around H atoms in each CH(3) group in the (CH(3)S)(2) molecule. The STM images revealed that the molecules have a total of six equivalent adsorption orientations on Cu(111), which are given by the combination of three equivalent adsorption sites and two conformational isomers for each adsorption site.     

Ultrathin wagon-wheel-like TiOx phases on Pt(111): a combined low-energy electron diffraction and scanning tunneling microscopy investigation

Ultrathin ordered titanium oxide films on a Pt(111) surface have been prepared by reactive deposition and characterized by low-energy electron diffraction and scanning tunneling microscopy (STM). According to the postdeposition annealing condition, three different phases have been prepared which show a wagon-wheel-like (hereafter ww) morphological pattern. Two of them can be prepared as single phases (w- and w'-TiO(x)) and one (w(int)-TiO(x)) as a mixed phase which always coexists with at least one of the other two phases. All of them are formed by a Ti-O bilayer, where the Ti atoms are located at the interface with the substrate, but they show a rather distinct STM ww pattern. The experimental STM contrast has been discussed on the basis of a Moiré-like model, i.e., as deriving from a modulation of the Ti occupancy of the different substrate sites (i.e., hollow, bridge and on-top sites). The major part of the STM data can be easily interpreted on the basis of this simplified model.