两亲性杯芳烃的超分子自组装

本文综述了两亲性杯芳烃分子在不同维数下组装研究的进展,主要包括零维组装(囊泡、胶束、树枝状分子和分子箱)、一维组装(纳米管,纳米线及纤维)和二维组装(LB膜、超薄分离膜及界面组装);探讨了不同维数下组装体的形成机理和驱动力,主要包括氢键作用、金属配位作用、静电作用、包结络合作用以及疏水相互作用;控制和调节不同维数下组装体的转变,有助于组装体材料在许多方面的应用。     

胆红素及其两亲衍生物的Langmuir-Blodgett膜研究

研究了亚相酸度和金属离子对胆红素(1)及其两个两亲衍生物胆红素二(十八烷基)酯(2)和胆红素二(十八烷基)酰胺(3)的单分子膜和LB膜性能的影响.通过π-A等温线、X射线光电子能谱、紫外-可见光谱等方法,研究了它们在有序分子膜中的分子伸展及与金属离子的配位方式.胆红素及其两亲衍生物与金属离子在有序分子膜中的配位(生成1:1型配合物)明显不同于其在本体溶液中的配位(1:1,1:2或2:1型配合物).小角X射线衍射表明1,2和3形成双层膜间距分别为2.15,5.55和5.65nm的Y型LB膜.     

小分子盐对盐酸十八胺单层膜影响的研究

利用Langmuir单层膜模拟生物矿化过程或者是利用LB膜技术构筑层状固体模板来制备与组装纳米材料已成为新的研究热点~([1,2]),因为通过变换成膜材料及制备条件,可以调控生成材料的性质.Langmuir单分子膜的成膜性能直接决定着LB膜的沉积质量、结构和性能~([3,4]).     

聚合物的LB膜

简要介绍了聚合物LB(Langmuir -Blodgett)膜的制备装置和制备过程。同时对聚合物LB膜这一门学科最新的进展和应用前景做了较为详尽的介绍和论述。目前 ,随着对LB膜的研究深入 ,在对小分子LB膜、可聚合LB膜、聚合物LB膜的成膜研究中引入了将几种方法优点综合起来的新的成膜方法 ,并已成为研究热点     

2-(1-萘基偶氮)-咪唑的合成及组装Langmuir-Blodgett膜

合成了一个非典型两亲性分子,2-(1-萘基偶氮)-咪唑(2-NDIM),对它在气/液界面上的组装和LB膜性质进行了研究。结果表明:2-NDIM不能在水相表面形成Langmuir膜,在Ag NO3水溶液亚相中能形成稳定、均匀的配位聚合物单分子膜,组装的LB膜为J-聚集体,最大吸收波长为403nm,归属于反式-N=N-双键的π-π*电子跃迁,光激发LB膜中偶氮基团的反-顺异构化作用不明显,具有较低的反-顺光异构化量子产率。     

用“表面离子”法制备组分可控的LB膜超分子体系

综述了LB膜超分子体系中“表面离子”法的概念及其与传统的“亚相离子”法的区别. 分别以钌螯合物(Ru(ph2phen)32＋)和金属β-二酮螯合物为例,详细描述这两类不同的“表面离子”在水面上的成膜作用机理,并举例说明“表面离子”法在铺展膜和LB膜中,功能分子二维密度和凝聚态结构精确可调,并对“表面离子”法在多功能分子体系中的应用作了详细描述.     

一种具有“浮萍”结构的单分子膜与Langmuir—Blodgett多层膜

本文以St-DVB微凝胶/甲基丙烯酸两性接枝共聚物制成了一种新型“浮萍”结构的单分子膜,并转移制备了LB多层膜,对其单分子膜的性质、LB多层膜的二维有序结构及膜的热稳定性进行了较深入的研究。     

新型偶氮苯自组装一LB组合有序膜的构造与表征

偶氮兹及其衍生物具有独特的光致异构化和电化学反应机制,其LB单分子膜作为一种高度有序的分子组装体系,以其诱人的应用前景引起了人们的极大兴趣．然而在这方面的研究中,LB膜通常是沉积在SnO。或镀金的基片上,其结构的相对木稳定性限制了实际应用的可能性．我们利用自组装技术,在金基底表面组装了具有特定末端基团的自组装单分子膜,然后利用LB技术构造偶氮苯衍生物的单分子膜,以期得到稳定而有序的偶氮苯LB膜,且不影响其光化学和电化学活性．本文报道了这种新型偶氮苯自组装一LB组合股的结构表征及其电化学行为．亚实验部分偶…     

具有纳米孔洞的金属-有机超分子聚合物与功能材料

本文介绍了近几年来一个热门的研究领域－纳米超分子笼和具有纳米孔洞的金属－有机聚合物的研究现状和发展趋势。目前该领域的研究主要集中在：设计合成有机桥联配体并与金属离子自组装成各类具有纳米孔洞的超分子化合物和一维、二维或三维的金属－有机聚合物,应用结构化学研究手段,研究它们的自组装规律、空间结构、电子结构及其物理化学性能,寻找这两类化合物在生物工程与功能材料等领域中的应用。     

具有纳米孔洞的金属-有机超分子聚合物与功能材料

本文介绍了近几年来一个热门的研究领域-纳米超分子笼和具有纳米孔洞的金属-有机聚合物的研究现状和发展趋势。目前该领域的研究主要集中在:设计合成有机桥联配体并与金属离子自组装成各类具有纳米孔洞的超分子化合物和一维、二维或三维的金属-有机聚合物,应用结构化学研究手段,研究它们的自组装规律、空间结构、电子结构及其物理化学性能,寻找这两类化合物在生物工程与功能材料等领域中的应用。     

Two-dimensional arrays of amphiphilic Zn2+-cyclens for guided molecular recognition at interfaces

The sterically guided molecular recognition of nucleobases, phosphates, adenosine, and uridine nucleotides on Langmuir monolayers and Langmuir-Blodgett monolayers of amphiphilic mono- or bis(Zn2+-cyclen)s assembled on thiolated surfaces was investigated. The stepwise selective binding of metal ions, uracil, or phosphate by dicetyl cyclen monolayers with variously tuned structures at the air/water interface was corroborated by the measurements of the corresponding LB films deposited onto quartz crystals. Two types of recognition surfaces were fabricated from Zn2+-dicetyl cyclen. The surface covered with a complex preformed in the Langmuir monolayer was capable both of imide and of phosphate binding. The similar complex formed directly in an LB film on thiolated gold was inactive with respect to imide. The surface plasmon resonance measurements evidenced the stepwise assembly of complementary nucleotides on SAM/LB templates through consecutive phosphate-Zn2+-cyclen coordination. Base pairing between nucleotides resulted in a formation of A-U bilayers comprising two complementary monolayers. Finally, we report on SAM/LB patterns designed for divalent molecular recognition of uridine phosphate by amphiphilic bis(Zn2+-cyclen).     

One-step synthesis of monodisperse silver nanoparticles beneath vitamin E Langmuir monolayers

The monodisperse silver nanoparticles were synthesized by one-step reduction of silver ions in the alkaline subphase beneath vitamin E (VE) Langmuir monolayers. The monolayers and silver nanocomposite LB films were characterized by surface pressure-area (pi-A) isotherms, transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-vis), selected area electron diffraction (SAED), Fourier transform infrared transmission spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), respectively. The results showed that the limiting area/VE molecule on different subphases varied. The phenolic groups in the VE molecules were converted to a quinone structure, and the silver ions were mainly reduced to ellipsoidal and spherical nanoparticles. The arrangement of the nanoparticles changed from sparseness to compactness with reaction time. The electron diffraction pattern indicated that the silver nanoparticles were face-centered cubic (fcc) polycrystalline. Silver nanocomposite LB films with excellent quality could be formed on different substrates, indicating that the transfer ratio of monolayer containing silver nanoparticles is close to unity. The dynamic process of reduction of silver ions by VE LB films was also studied through monitoring the conductivity of an Ag2SO4 alkaline solution.     

Pure and mixed films of a nitrostilbene derivative at the air-water interface, Langmuir-Blodgett multilayer fabrication, and optical characterization

This paper reports the preparation and characterization of pure Langmuir and Langmuir-Blodgett (LB) films of a stilbene derivative containing two alkyl chains, namely 4-dioctadecylamino-4'-nitrostilbene. Mixed films incorporating docosanoic acid and the stilbene derivative are also studied. Brewster angle microscopy (BAM) analysis has revealed the existence of randomly oriented three-dimensional (3D) aggregates, spontaneously formed immediately after the spreading process of the stilbene derivative onto the water surface. These 3D aggregates coexist with a Langmuir film that shows the typical gas, liquid, and solid-like phases in the surface pressure and surface potential vs area per molecule isotherms, indicative of an average preferential orientation of the stilbene compound at the air-water interface, and a gradual molecular arrangement into a defined structure upon compression. A blue shift of 55 nm of the reflection spectrum of the Langmuir film with respect to the spectrum of a chloroform solution of the nitrostilbene indicates that two-dimensional (2D) H-aggregates are formed at the air-water interface. The monolayers are transferred undisturbed onto solid substrates with atomic force microscopy (AFM) revealing that the one layer LB films are constituted by a monolayer of the stilbene derivative together with some 3D aggregates. When the nitrostilbene compound is blended with docosanoic acid, the 3D aggregation is avoided in the Langmuir and Langmuir-Blodgett films, but does not limit the formation of 2D H-aggregates, desirable for second-order nonlinear optical response in the blue domain. The AFM images of the mixed LB films show that they are formed by a docosanoic acid monolayer and, on the top of it, a bilayer of the stilbene derivative.     

Equilibrium structure and dynamics of (2R, 3R)-(+)-bis(decyloxy)succinic acid at the air-water interface

A twin-tailed, twin-chiral fatty acid, (2R,3R)-(+)-bis(decyloxy)succinic acid was synthesized and its two dimensional behavior at the air-water interface was examined. The pH of the subphase had a profound effect on the monolayer formation. On acidic subphase, stable monolayers with increased area per molecule due to hydrogen bonding and bilayers at collapse pressures were observed. Highly compressible films were formed at 40 degrees C, while stable monolayers with increased area were observed at sub-room temperatures. Langmuir monolayers formed on subphases containing 1 mM ZnCl2 and CaCl2 revealed two dimensional metal complex formation with Zn2+ forming a chelate-type complex, while Ca2+ formed an ionic-type complex. Monolayers transferred from the condensed phase onto hydrophilic Si(100) and quartz substrates revealed the formation of bilayers through transfer-induced monolayer buckling. Compression induced crystallites in 2D from monolayers and vesicle-like supramolecular structures from multilayers were the noted LB film characteristics, adopting optical imaging and electron microscopy. The interfacial monolayer structure studied through molecular dynamics simulation revealed the order and packing at a molecular level; monolayers adsorbed at various simulated specific areas of the molecule corroborated the (pi-A) isotherm and the formation of a hexagonal lattice at the air-water interface.     

Langmuir monolayers based on rigid wedge-shaped dendrons of benzenesulfonic acid

The structure formation of wedge-shaped monodendrons based on symmetric benzenesulfonic acid with different lengths of peripheral alkyl chains was studied in Langmuir monolayers and Langmuir–Blodgett (LB) films. A phase transition from the liquid-expanded state to the liquid-condensed state was observed on compression of the Langmuir monolayers of the dendrons containing dodecyl lateral chains. The transition is accompanied by the formation of star-shaped aggregates visualized by Brewster angle microscopy. The three-layer LB transfer results in the reorganization of the monolayer into regions of bi-, tetra-, and hexalayers on a solid substrate with a low coverage of the surface. Homogeneous liquid-condensed mono layers are formed for the dendrons with hexa- and octadecyl chains, and the film thickness achieved by the LB transfer corresponds to the monolayer alignment of the molecules with the surface coverage up to 90%. It was determined that varying the alkyl length of wedge-shaped dendrones based on symmetric benzenesulfonic acid leads to a change in phase behavior of Langmuir monolayers as well as Langmuir–Blodgett films formed by them.     

Influence of ion transfer kinetics on the composition of langmuir-blodgett films

The effect of ion transfer kinetics on the ionic composition of Langmuir-Blodgett (LB) films formed by charged monolayers is analyzed. The dynamic regimes of the LB deposition are considered by taking into account the competitive adsorption of several counterions having different diffusivities, valences, binding constants, and bulk concentrations. It is shown that the composition of deposited films should change with the deposition rate. At lower deposition rates, the ion with higher binding constant is more represented within the deposited monolayer in comparison to the higher deposition rates. At low deposition rates, the ratio of counterion amounts within the LB films is the same as that within the floating monolayer excluding the ions within the diffuse layer. At high deposition rates, the ratio of the counterion amounts is the same as that within the floating monolayer when the potential-determining counterions within the diffuse layer are taken into account.     

Self-organization of a wedge-shaped surfactant in monolayers and multilayers

The self-organization behavior of a wedge-shaped surfactant, disodium-3,4,5-tris(dodecyloxy)phenylmethylphosphonate, was studied in Langmuir monolayers (at the air-water interface), Langmuir-Blodgett (LB) monolayers and multilayers, and films adsorbed spontaneously from isooctane solution onto a mica substrate (self-assembled films). This compound forms an inverted hexagonal lyotropic liquid crystal phase in the bulk and in thick adsorbed films. Surface pressure isotherm and Brewster angle microscope (BAM) studies of Langmuir monolayers revealed three phases: gas (G), liquid expanded (LE), and liquid condensed (LC). The surface pressure-temperature phase diagram was determined in detail; a triple point was found at approximately 10 degrees C. Atomic force microscope (AFM) images of LB monolayers transferred from various regions of the phase diagram were consistent with the BAM images and indicated that the LE regions are approximately 0.5 nm thinner than the LC regions. AFM images were also obtained of self-assembled films after various adsorption times. For short adsorption times, when monolayer self-assembly was incomplete, the film topography indicated the coexistence of two distinct monolayer phases. The height difference between these two phases was again 0.5 nm, suggesting a correspondence with the LE/LC coexistence observed in the Langmuir monolayers. For longer immersion times, adsorbed multilayers assembled into highly organized periodic arrays of inverse cylindrical micelles. Similar periodic structures, with the same repeat distance of 4.5 nm, were also observed in three-layer LB films. However, the regions of organized periodic structure were much smaller and more poorly correlated in the LB multilayers than in the films adsorbed from solution. Collectively, these observations indicate a high degree of similarity between the molecular organization in Langmuir layers/LB films and adsorbed self-assembled films. In both cases, monolayers progress through an LE phase, into LE/LC coexistence, and finally into LC phase as surface density increases. Following the deposition of an additional bilayer, the film reorganizes to form an array of inverted cylindrical micelles.     

Langmuir-Blodgett films of a Mo-blue nanoring [Mo(142)O(429)H(10)(H(2)O)(49)(CH(3)CO(2))(5)(CH(3)CH(2)CO(2))](30)(-) (Mo(142)) by the semiamphiphilic method

Langmuir monolayers and LB films of the ring-shaped mixed-valence polyoxomolybdate [Mo142O429H10(H2O)49(CH3CO2)5(CH3CH2CO2)](30-) (Mo142) dissolved in the aqueous subphase have been successfully fabricated by using the adsorption properties of a DODA monolayer. Infrared and ultraviolet-visible spectroscopy of the LB films indicates that Mo142 and DODA molecules are incorporated within these LB films. X-ray reflectivity experiments indicate that the LB films exhibit a well-defined lamellar structure formed by bilayers of DODA molecules alternating with monolayers of Mo142. Using behenic acid-modified hydrophobic quartz substrate is critical for the formation of the well-defined lamellar structure. From the values of the periodicity obtained by these experiments it is clear that the Mo142 clusters lie flat along the charged organic layers. AFM images also showed the flat and homogeneous films on the quartz substrates treated with behenic acid. Cyclic voltammograms of Mo142-LB films deposited on ITO substrates showed quasi-reversible oxidation/reduction waves with positive shift of the potential compared to the case of solution.     

Thermodynamic characteristics and Langmuir-Blodgett deposition behavior of mixed DPPA/DPPC monolayers at air/liquid interfaces

The role of dipalmitoylphosphatic acid (DPPA) as a transfer promoter to enhance the Langmuir-Blodgett (LB) deposition of a dipalmitoylphosphatidylcholine (DPPC) monolayer at air/liquid interfaces was investigated, and the effects of Ca2+ ions in the subphase were discussed. The miscibility of the two components at air/liquid interfaces was evaluated by surface pressure-area per molecule isotherms, thermodynamic analysis, and by the direct observation of Brewster angle microscopy (BAM). Multilayer LB deposition behavior of the mixed DPPA/DPPC monolayers was then studied by transferring the monolayers onto hydrophilic glass plates at a surface pressure of 30 mN/m. The results showed that the two components, DPPA and DPPC, were miscible in a monolayer on both subphases of pure water and 0.2 mM CaCl2 solution. However, an exception occurs between X(DPPA)=0.2 and 0.5 at air/CaCl2-solution interface, where a partially miscible monolayer with phase separation may occur. Negative deviations in the excess area analysis were found for the mixed monolayer system, indicating the existence of attractive interactions between DPPA and DPPC molecules in the monolayers. The monolayers were stable at the surface pressure of 30 mN/m for the following LB deposition as evaluated from the area relaxation behavior. It was found that the presence of Ca2+ ions had a stabilization effect for DPPA-rich monolayers, probably due to the association of negatively charged DPPA molecules with Ca2+ ions. Moreover, the Ca2+ ions may enhance the adhesion of DPPA polar groups to a glass surface and the interactions between DPPA polar groups in the multilayer LB film structure. As a result, Y-type multilayer LB films containing DPPC could be fabricated from the mixed DPPA/DPPC monolayers with the presence of Ca2+ ions.