由烷基硫醇组成的三元混合膜结构与性质研究

本文采用共吸附法制备了由戊硫醇(PT),癸硫醇(DT)和十六烷基硫醇(HDT)组成的三元混合膜,通过循环伏安,X-射线光电子能谱,扫描隧道显微镜(STM)和导电原子力对其结构及性质进行了表征。研究表明硫醇分子通过Au-S键在金电极上形成了一层致密的单分子膜,组装膜表面组成与其在组装液中的摩尔浓度有关。混合膜中各组分形成独立的相区,具有不同的电子传递能力。该研究为未来纳米器件的开发提供更多样化的表面以及更加详实的理论依据。     

前言:表面分子与超分子化学

<正>表面分子组装与反应是表面科学的重要分支.前者的研究对象是分子间靠非共价作用自发形成的有序结构及过程(即自组装),后者则是研究通过表面辅助的化学反应形成共价连接的分子结构及过程.自1991年Juergen P.Rabe教授研究组报道用扫描隧道显微镜(STM)直接观测直链烷烃在高序热解石墨表面的有序排列以来,随着表征手段和技术的不断发展和完善,表面分子自组装在过去近30年间已发展成为一个重要的研究领域.表面的引入使得分子的运动受限,二维的分子自组装既寓于三维体系组装的共性之中,又具有本身的特殊性.与此相比,表面     

活性胃蛋白酶在阳离子化PET 表面的自组装功能膜研究

利用分子沉积法在表面阳离子化的聚对苯二甲酸乙二酯基材上制备活性胃蛋白酶分子的自组装生物膜,并利用原子力显微镜和X-射线光电子能谱对基材和活性胃蛋白酶/PET-NH3^ 组装膜的表面形貌及组分进行了研究。     

贵金属纳米颗粒在玻碳电极上的层层组装

采用表面活性剂二辛酯琥珀酸磺酸钠(AOT, sodiumbis(2-ethylhexyl)sulfosuccinate)微乳法可以制备得到各种贵金属纳米颗粒(包括银、金、铂以及钯),其性质利用紫外-可见吸收光谱、透射电镜、X-射线衍射、傅立叶变换红外光谱以及Zeta电位分析进行了表征。通过层层自组装方法,将带有负电荷的Pt纳米颗粒和聚阳离子(聚烯丙基氯化铵, PAH)自组装到玻碳电极上,并研究了该修饰电极对甲醇的电催化氧化性质。     

表面功能化聚苯乙烯纳米微球的制备及自组装

用乳液聚合的方法合成了表面富含羧基的聚苯乙烯纳米微球，采用热分析、红外、透射电镜和X射线粉末衍射仪等对其进行了结构和性能表征;并用自组装的方法将其在玻璃表面组装成膜.考察了制备条件，通过对自组装薄膜原子力显微镜形貌图的分析，确立了最佳组装方案.     

液/固界面多肽分子组装精细结构的扫描隧道显微镜研究

介绍了与蛋白构象病相关的淀粉样多肽分子组装结构的研究进展.综述了在固体、溶液以及界面等不同状态下多肽分子组装结构的表征方法,对于扫描隧道显微技术(STM)在解析多肽分子界面组装结构方面的研究进展进行了重点评述,主要包括在液/固界面上的多肽分子组装结构的精细特征,界面诱导的多肽构象转变,调节分子、染料等与多肽组装结构的相互作用模式和位点识别等.     

金属配合物分子纳米结构构筑与调控的STM研究进展

金属配合物分子具有结构多样且可控以及功能丰富等特点,在催化、传感、分子识别、纳米器件等领域得到广泛应用, 对金属配合物分子的研究已是分子科学研究中的热点之一.同时, 利用配合物分子构筑表面分子纳米结构以及对配合物单分子性质的研究也日趋活跃. 近年来, 本研究组发展了配合物分子在固体表面的自组装技术, 并结合扫描隧道显微技术(STM)开展了一系列有关金属配合物分子表面纳米结构的研究工作, 在固体表面成功实现了对配体、配合物分子的高分辨STM成像、原位配合以及分子识别, 设计和构筑了多种功能配合物分子纳米结构,并系统研究了结构形成规律. 本文以本研究组近年来有关金属配合物分子组装的研究结果为主, 结合国内外相关研究小组的研究结果,综述有关金属配合物分子纳米结构的构筑与调控的STM研究进展, 介绍该类分子在固体表面的组装和分散规律, 为表面分子纳米结构的构筑和调控提供理论和实验基础.     

Schiff碱N-aete-N在Au(111)上自组装单分子膜的电化学及STM研究

利用电化学技术及扫描隧道显微镜 ( STM) ,于 0 .1 mol/L HCl O4溶液中研究了 Schiff碱 N-aete-N在单晶 Au( 1 1 1 )面上所形成的自组装单分子膜 ( SAMs)的电化学性质及结构 .N-aete-N在 Au( 1 1 1 )电极表面的吸附抑制了金的阳极氧化 ,同时使固 /液界面双层电容明显降低 .观察到 N-aete-N SAMs的高分辨 STM图像 .N-aete-N分子在 Au( 1 1 1 )表面上以 ( 6× 7)结构单胞呈二维有序排列 ,其表面浓度为5 .5× 1 0 -11mol/cm2 .     

四氮杂杯芳烃三嗪衍生物在Au(111)表面的自组装结构的电化学STM研究

利用电化学扫描隧道显微镜和循环伏安法研究了一种新型的杂杯杂芳烃四氮杂杯芳烃三嗪衍生物在Au(111)表面的自组装结构. 高分辨的STM图像表明, 该杂杯杂芳烃可以在Au(111)表面形成长程有序的单层膜. 此外, 分子以1,3-交替构象吸附, 两个三嗪环平躺在表面, 而苯环倾斜吸附在基底上, 这是分子间与分子-基底间相互作用平衡的结果.     

二氧化钛负载单原子催化剂用于光催化反应的研究（英文）

二氧化钛是目前被广泛研究和运用的金属氧化物。该文章总结当前二氧化钛负载单原子金属,包括铂、钯、铱、铑、铜、钌等催化剂的制备方法、表征手段和光催化反应的运用。二氧化钛表面负载单原子金属的主要制备方法包括表面缺陷法、表面修饰、高温脉冲及表面金属配体组装等。该文章探讨这些制备方法的控制条件和实用范围,并讨论负载型单原子催化剂的表征手段,包括电镜表征(球差校正扫描透射显微镜和扫描隧道显微镜)和谱学分析(扩展的X-光吸收精细结构分析、分子探针红外吸收谱等)。最后文章针对二氧化钛负载单原子催化剂在光催化水裂解产氢的作用机理和在光催化二氧化碳还原反应的运用做出讨论。     

Supramolecular self-assembled polynuclear complexes from tritopic, tetratopic, and pentatopic ligands: structural, magnetic and surface studies

Polymetallic, highly organized molecular architectures can be created by "bottom-up" self-assembly methods using ligands with appropriately programmed coordination information. Ligands based on 2,6-picolyldihydrazone (tritopic and pentatopic) and 3,6-pyridazinedihydrazone (tetratopic) cores, with tridentate coordination pockets, are highly specific and lead to the efficient self-assembly of square [3 x 3] Mn9, [4 x 4] Mn16, and [5 x 5] Mn25 nanoscale grids. Subtle changes in the tritopic ligand composition to include bulky end groups can lead to a rectangular 3 x [1 x 3] Mn9 grid, while changing the central pyridazine to a more sterically demanding pyrazole leads to simple dinuclear copper complexes, despite the potential for binding four metal ions. The creation of all bidentate sites in a tetratopic pyridazine ligand leads to a dramatically different spiral Mn4 strand. Single-crystal X-ray structural data show metallic connectivity through both mu-O and mu-NN bridges, which leads to dominant intramolecular antiferromagnetic spin exchange in all cases. Surface depositions of the Mn9, Mn16, and Mn25 square grid molecules on graphite (HOPG) have been examined using STM/CITS imagery (scanning tunneling microscopy/current imaging tunneling spectroscopy), where tunneling through the metal d-orbital-based HOMO levels reveals the metal ion positions. CITS imagery of the grids clearly shows the presence of 9, 16, and 25 manganese ions in the expected square grid arrangements, highlighting the importance and power of this technique in establishing the molecular nature of the surface adsorbed species. Nanoscale, electronically functional, polymetallic assemblies of this sort, created by such a bottom-up synthetic approach, constitute important components for advanced molecule-based materials.     

Structural Transformation of Surface-Confined Porphyrin Networks by Addition of Co Atoms

The self-assembly of a nickel-porphyrin derivative (Ni-DPPyP) containing two pyridyl coordinating sites and two pentyl chains at trans meso positions was studied with scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) on Au(111). Deposition of Ni-DPPyP onto Au(111) gave rise to a close-packed network for coverages smaller or equal to one monolayer as revealed by STM and LEED. The molecular arrangement of this two-dimensional network is stabilized via hydrogen bonds formed between the pyridyl's nitrogen and hydrogen atoms from the pyrrole groups of neighboring molecules. Subsequent deposition of cobalt atoms onto the close-packed network and post-deposition annealing at 423 K led to the formation of a Co-coordinated hexagonal porous network. As confirmed by XPS measurements, the porous network is stabilized by metal-ligand interactions between one cobalt atom and three pyridyl ligands, each pyridyl ligand coming from a different Ni-DPPyP molecule.     

Synthesis and self-assembly of a rigid exotopic bisphenanthroline macrocycle: surface patterning and a supramolecular nanobasket

The synthesis and characterisation of a rigid nanoscale macrocycle with two exotopic phenanthroline binding sites is reported. Scanning tunnelling microscopy (STM) at the solid-liquid interface reveals the formation of highly ordered monolayers of macrocycles with dimensions that are in good agreement with the calculated structure. Using the HETPHEN concept several bisheteroleptic coordination complexes with other phenanthrolines and a nanoscale basket assembly were prepared in presence of copper(I) ions. NMR spectroscopy, mass spectrometric data and elemental analysis point to three distinct isomers of the basket assembly in solution. A silver basket was prepared and readily converted to its copper analogue. Electrospray ionisation (ESI)-MS and spectrophotometric investigations provided additional mechanistic insight into the assembly process. Hence, the exotopic bisphenanthroline macrocycle in combination with HETPHEN concept proves to be very effective in controlling the compositional aspects of multicomponent self-assembly.     

Preparation of well-aligned carbon nanotubes/silicon nanowires core-sheath composite structure arrays in porous anodic aluminum oxide templates

The well-aligned carbon nanotubes (CNTs) arrays with opened ends were prepared in ordered pores of anodic aluminum oxide (AAO) template by the chemical vapor deposition (CVD) method. After then, silicon nanowires (SiNWs) were deposited in the hollow cavities of CNTs. By using this method, CNTs/SiNWs core-sheath composite structure arrays were synthesized successfully. Growing structures and physical properties of the CNTs/SiNWs composite structure arrays were analyzed and researched by the scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction spectrum (XRD), respectively. The field emission (FE) behavior of the CNTs/SiNWs composite structure arrays was studied based on Fowler-Nordheim tunneling mechanism and current-voltage (/-V) curve. And the photoluminescence (PL) was also characterized. Significantly, the CNTs/SiNWs core-sheath composite structure nanowire fabricated by AAO template method is characteristic of a metal/semiconductor (M/S) behavior and can be     

Self-assembly of monodispersed, chiral nanoclusters of cysteine on the Au(110)-(1 x 2) surface

The self-assembly of monodispersed supramolecular nanoclusters was observed by scanning tunneling microscopy (STM). The clusters form from the naturally occurring amino acid cysteine by vapor deposition onto the Au(110)-(1 x 2) surface under ultrahigh vacuum conditions. Enantiomerically pure l- and d-cysteine yields clusters with mirror-image STM signatures. Racemic ld-cysteine segregates into homochiral clusters, evidencing specific intermolecular interactions during the self-assembly process.     

Ionic hydrogen bonds controlling two-dimensional supramolecular systems at a metal surface

Hydrogen-bond formation between ionic adsorbates on an Ag(111) surface under ultrahigh vacuum was studied by scanning tunneling microscopy/spectroscopy (STM/STS), X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and molecular dynamics calculations. The adsorbate, 1,3,5-benzenetricarboxylic acid (trimesic acid, TMA), self-assembles at low temperatures (250-300 K) into the known open honeycomb motif through neutral hydrogen bonds formed between carboxyl groups, whereas annealing at 420 K leads to a densely packed quartet structure consisting of flat-lying molecules with one deprotonated carboxyl group per molecule. The resulting charged carboxylate groups form intermolecular ionic hydrogen bonds with enhanced strength compared to the neutral hydrogen bonds; this represents an alternative supramolecular bonding motif in 2D supramolecular organization.     

C-H...F hydrogen bonding: the origin of the self-assemblies of bis(2,2'-difluoro-1,3,2-dioxaborine)

The effect of the molecular structure on the self-assembly of specially designed two-core 1,3,2-dioxaborines has been studied with various techniques. It was found that the molecules spontaneously adsorbed on HOPG surfaces and self-organized into well-ordered two-dimensional (2D) monolayers. The structural details of the 2D assemblies were investigated by scanning tunneling microscopy (STM). From X-ray analysis of the corresponding three-dimensional (3D) crystal and from theoretical calculation, we were able to reveal the driving force behind the specific self-assembly. The C-H...F hydrogen bonding between the ortho carbon of the phenyl ring and the fluorine of the BF2 group plays an important role in the formation of the adlayers. The different electron affinities and geometries of the molecules affect the intermolecular interactions which further lead to different properties in the bulk materials.     

STM studies of single molecules: molecular orbital aspects

As a fundamental and frequently referred concept in modern chemistry, the molecular orbital plays a vital role in the science of single molecules, which has become an active field in recent years. For the study of single molecules, scanning tunneling microscopy (STM) has been proven to be a powerful scientific technique. Utilizing specific distribution of the molecular orbitals at spatial, energy, and spin scales, STM can explore many properties of single molecule systems, such as geometrical configuration, electronic structure, magnetic polarization, and so on. Various interactions between the substrate and adsorbed molecules are also understood in terms of the molecular orbitals. Molecular engineering methods, such as mode-selective chemistry based on the molecular orbitals, and resonance tunneling between the molecular orbitals of the molecular sample and STM tip, have stimulated new advances of single molecule science.     

Modular engineering of H-bonded supramolecular polymers for reversible functionalization of carbon nanotubes

A H-bond-driven, noncovalent, reversible solubilization/functionalization of multiwalled carbon nanotubes (MWCNTs) in apolar organic solvents (CHCl(3), CH(2)Cl(2), and toluene) has been accomplished through a dynamic combination of self-assembly and self-organization processes leading to the formation of supramolecular polymers, which enfold around the outer wall of the MWCNTs. To this end, a library of phenylacetylene molecular scaffolds with complementary recognition sites at their extremities has been synthesized. They exhibit triple parallel H-bonds between the NH-N-NH (DAD) functions of 2,6-di(acetylamino)pyridine and the CO-NH-CO (ADA) imidic groups of uracil derivatives. These residues are placed at 180° relative to each other (linear systems) or at 60°/120° (angular modules), in order to tune their ability of wrapping around MWCNTs. Molecular Dynamics (MD) simulations showed that the formation of the hybrid assembly MWCNT?[X?Y](n) (where X = 1a or 1b -DAD- and Y = 2, 3, or 4 -ADA-) is attributed to π-π and CH-π interactions between the graphitic walls of the carbon materials and the oligophenyleneethynylene polymer backbones along with its alkyl groups, respectively. Addition of polar or protic solvents, such as DMSO or MeOH, causes the disruption of the H-bonds with partial detachment of the polymer from the CNTs, followed by precipitation. Taking advantage of the chromophoric and luminescence properties of the molecular subunits, the solubilization/precipitation processes have been monitored by UV-vis absorption and luminescence spectroscopies. All hybrid MWCNTs-polymer materials have been also structurally characterized via thermogravimetric analysis (TGA), transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning tunneling microscopy (STM), and X-ray photoelectron spectroscopy (XPS).     

Investigation of negative differential resistance properties of self-assembled dipyridinium using STM

Recently, research on conducting molecules containing thiol functional groups such as benzenethiol has been progressing [X. Xiao, B. Xu, N.J. Tao, Nano Lett. 4 (2004) 267]. This conducting molecule is applicable to the study of the negative differential resistance (NDR) and switching properties of logic device. The 4-{4[4-(4-{1-[4-(4-acetylsulfanyl-phenylethynyl)-phenyl]-2,6-diphenyl-pyridinium-4-yl}-phenyl)-2,6-diphenyl-pyridinium-1-yl]-phenylethynyl}-phenylthioacetate (dipyridinium) molecule contains thiol functional groups such as benzenethiol. Thus, we have studied an NDR property of a dipyridinium molecule using the self-assembly method in scanning tunneling microscopy (STM). The Au substrate was exposed to a 1 mM solution of 1-dodecanethiol in ethanol for 24 h to form a monolayer. After thorough rinsing of the sample, it was exposed to a 0.1 μM solution of dipyridinium in dimethylformamide (DMF) for 30 min. After the assembly, we measured the electrical properties of the self-assembly monolayers (SAMs) using ultra high vacuum scanning tunneling microscopy (UHV-STM) and scanning tunneling spectroscopy (STS). As a result, we confirmed the properties of NDR in a negative region at −1.67 V and a positive region at 1.78 V. The energy gap (E_g) was found to be 3.12 eV [C. Arena, B. Kleinsorge, J. Robertson, W.I. Milne, M.E. Welland, J. Appl. Phys. 85 (1999) 1609]. This molecule is applicable to the fabrication of molecular junctions.