5,10,15,20-四-(4-N,N,N-二甲基十六烷基氨基苯基)卟啉LB膜结构的研究

研究了两亲性卟啉5,10,15,20-四-(4-N,N,N-二甲基十六烷基氨基苯基)卟啉(TDMC₁₆PP)在气/液界面上的成膜性能,制备了其多层LB膜。用UV-Vis吸收光谱、荧光光谱、偏振UV-Vis吸收光谱和小角X射线衍射对LB膜进行了测试表征。结果表明:两亲性卟啉TDMC₁₆PP具有良好的成膜性能,其LB膜性质稳定,有较好的结构均匀性和周期性。在LB膜内,脂肪链并不是直立的,卟啉大环平面与基片平面成42.5°排列。     

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.     

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.     

2-烷基-苯并咪唑在硝酸银亚相上的Langmuir膜及LB膜

对不同链长的2-烷基-苯并咪唑衍生物（BzCn,烷基链长从C5到C15）在硝酸银亚相上的成膜行为及形成的LB膜的结构进行了研究.表面压－面积曲线的结果表明，短链(C5～C9)的2-烷基-苯并咪唑可在银离子亚相上形成稳定的单分子膜，而长链(C13和C15)衍生物则形成多层膜.利用LB技术可将上述Langmuir膜转移到固体基板上形成LB膜，其吸收光谱的结果说明了苯并咪唑和银离子配位.利用AFM、XRD及FT-IR等技术研究了烷基链长对LB膜结构的影响.实验结果表明,除了BzC15，其余的衍生物都可形成规整的层状结构.短链衍生物的单层LB膜具有均一、平整的形貌；而对于BzC15，观察到多层结构.     

电荷转移配合物薄膜制备方法和结构表征的研究进展

回顾了与Langmuir-Blodgett(LB)技术有关的电荷转移配合物薄膜的各类制备方法、结构表征结果,并比较了制备方法对薄膜结构的影响.例如,将LB膜C18H37TCNQ(电子受体)插入到电子给体3,3’,5,5’-tetramethylbenzidine(四甲基联苯胺, TMB)的石油醚溶液中进行掺杂,制备了TMB•C18H37TCNQ电荷转移配合物薄膜.在这种薄膜中,给体和受体以面对面的方式堆积,两者的环平面与基片平面接近垂直.而采用硬脂酸和C18H37TCNQ的混合LB膜通过类似的掺杂路线制备的TMB•C18H37TCNQ薄膜的结构发生了一些变化,例如其长的烃链C18H37更加垂直于基片平面.通过比较以前的各种实验结果可以得出以下结论:电荷转移配合物的结构可以通过制备方法得到控制.     

The structures of Langmuir-Blodgett films of fatty acids and their salts

Recent advances in several experimental techniques have enabled detailed structural information to be obtained for floating (Langmuir) monolayers and Langmuir-Blodgett films. These techniques are described briefly and their application to the study of films of fatty acids and their salts is discussed. Floating monolayers on aqueous subphases have been shown to possess a complex polymorphism with phases whose structures may be compared to those of smectic mesophases. However, only those phases that exist at high surface pressures are normally used in Langmuir-Blodgett (LB) deposition. In single LB monolayers of fatty acids and fatty acid salts the acyl chains are in the all-trans conformation with their long axes normal to the substrate. The in-plane molecular packing is hexagonal with long-range bond orientational order and short-range positional order: known as the hexatic-B structure. This structure is found irrespective of the phase of the parent floating monolayer. The structures of multilayer LB films are similar to the structures of their bulk crystals, consisting of stacked bilayer lamellae. Each lamella is formed from two monolayers of fatty acid molecules or ions arranged head to head and held together by hydrogen bonding between pairs of acids or ionic bonding through the divalent cations. With acids the acyl chains are tilted with respect to the substrate normal and have a monoclinic structure, whereas the salts with divalent cations may have the chains normal to the substrate or tilted. The in-plane structures are usually centred rectangular with the chains in the trans conformation and packed in a herringbone pattern. Multilayer films of the acids show only a single-step order-disorder transition at the melting point. This temperature tends to rise as the number of layers increases. Complex changes occur when multilayer films of the salts are heated. Disorder of the chains begins at low temperatures but the arrangement of the head groups does not alter until the melting temperature is reached. Slow heating to a temperature just below the melting temperature gives, with some salts, a radical change in phase. The lamellar structure disappears and a new phase consisting of cylindrical rods lying parallel to the substrate surface and stacked in a hexagonal pattern is formed. In each rod the cations are aligned along the central axis surrounded by the disordered acyl chains.     

硬脂酸镉和山嵛酸镉混合LB膜的微结构

X-ray diffraction (XRD) was used to investigate the microstructure and phase separation of mixed multilayers of cadmium stearate (SA) and behenate (BA) deposited onto hydrophilic glass by the Langmuir-Blodgett technique. No unitary fatty acid diffraction peaks in the XRD spectra of the mixed LB films, which reveals that domains in these samples are small and uniform. The interplanar spacing of the mixed LB films changes with the ratio of BA to SA in a step-shaped curve, which suggests that with the changing of the ratio between BA and SA, only three kinds of ordered structure form in the mixed system, and each microstructure, in particular, the short chains against long chains meshed microstructure can be maintained in a certain ratio range . In addition, for the meshed microstructure, the alkyl chains of both SA and BA stand straight or may have exactly the same small tilted angle from the substrate normal, as is indicated by the symmetric and asymmetric stretching vibration of methylene (CH2) peaks which are at 2847.80 and 2914.37 cm-1respectively in the Fourier transform infrared (FT-IR) transmission spectra. The mixed system always goes through a longitudinal regularity decreasing process when BA/SA is out of the intermediate ratio range (BA/SA: 1/5-1/1), which is illustrated by the relative XRD intensity changing with the ratio of BA/ SA in a \W" shape. These results for the mixed LB films of BA/SA provide meaningful data for choosing the mixture ratio when fabricating composite films with special structure.     

具有不同取代链长的卟啉衍生物LB膜的结构研究

本文研究了三种羧酸取代的四苯基卟啉衍生物在空气/Cd^2^+水溶液界面上所形成的单层膜及LB膜。这三种卟啉衍生物中, 一种没有脂链, 另外两种具有不同长度的脂链。由π-A等温线得到的平均表观分子面积相差很大。紫外-可见光谱表明, LB膜中卟啉的Soret吸收带相对于溶液的吸收均红移, 但红移程度不同。LB膜的偏振紫外-可见光谱表明, LB膜中三种卟啉衍生物的卟啉环具有基本一致的取向。运用亚相降低法得到了三种卟啉衍生物单层LB膜, 其紫外-可见光谱与用垂直提拉法得到的LB膜的紫外-可见光谱具有一致的特征。这些结果表明: 卟啉衍生物有无取代链及取代链长的不同对平均表观分子面积的大小和膜中环间的距离有影响, 但对环的取向没有影响。环的取向由环本身及环上的亲水取代基来确定。气/液界面上三种卟啉衍生物的单层膜中环也具有一致的取向, 且与LB膜中环的取向相差不大。提拉不会对膜中环的取向及膜的结构造成大的改变。     

Macroscopic alignment of graphene stacks by Langmuir-Blodgett deposition of amphiphilic hexabenzocoronenes

We present structural studies of Langmuir (L) and Langmuir-Blodgett (LB) films of new amphiphilic hexa-peri-hexabenzocoronene (HBC) discotics, carrying five branched alkyl side chains and one polar group. The polar group is either a carboxylic acid moiety or an electron acceptor moiety (anthraquinone). Grazing-incidence X-ray diffraction (GIXD) and X-ray reflectivity, both utilizing synchrotron radiation, show that these amphiphilic HBCs form well-defined Langmuir monolayers at the air-water interface, with a pi-stacked columnar structure where the HBC cores are rotated around the surface normal and tilted relative to the water surface. The intercolumnar distance is 20 A. The HBCs are confined to a layer lying on top of the layer of polar groups that are in contact with the water subphase. Efficient transfer of the monolayer of the anthraquinone-substituted HBC derivative to hydrophobic quartz substrates by vertical dipping gave well-defined multilayer Y-type LB films. Polarized optical spectroscopy, GIXD, and X-ray reflectivity measurements show that the LB films consist of at least two phases. Heating the films results in an irreversible rearrangement to a single macroscopically aligned phase of hexagonally packed columns oriented along the dipping direction with disk planes perpendicular to the columnar axes and stacked in a cofacial manner. This phase transition is analogous to the reversible transition observed in the bulk material.     

Preparation and characterization of 5,10,15,20‐tetraphenylporphyrin Langmuir films for gas chemsensor applications

In this work is reported the preparation and characterization of 5,10,15,20‐tetraphenylporphyrin (H₂TPP) films at the water‐air interfaces. The surface pressure‐area isotherms (π‐A) and UV‐Vis spectroscopy were used to investigate the effect of the spreading methods and parameters on the porphyrin monolayer formation. Also, Langmuir‐Blodgett (LB) and Langmuir‐Schaefer (LS) films were deposited onto glass substrates in order to study the conformation changes in porphyrin molecular packing. Quartz crystal microbalance (QCM) was utilized as the active solid substrate for the development of the NO₂ gas sensor based on the H₂TPP molecular films. The results of π‐A curves have clearly shown the significant contribution of the preparation methods and processing parameters on the conformation of porphyrin molecular films. The UV‐Vis spectroscopy results using polarized absorption dichroism have indicated different molecular packing for porphyrin films deposited by LB and LS methods, with relative tilted angles of 50° ± 5° and 35° ± 5°, respectively. Moreover, the QCM response has given strong evidence that H₂TPP porphyrin molecular films have performed as NO₂ chemsensor. Copyright © 2011 John Wiley & Sons, Ltd.     

Interaction of small amounts of bovine serum albumin with phospholipid monolayers investigated by surface pressure and atomic force microscopy

The influence of small amounts of bovine serum albumin (BSA) (nM concentration) on the lateral organization of phospholipid monolayers at the air-water interface and transferred onto solid substrates as one-layer Langmuir-Blodgett (LB) films was investigated. The kinetics of adsorption of BSA onto the phospholipid monolayers was monitored with surface pressure isotherms in a Langmuir trough, for the zwitterionic dipalmitoylphosphatidyl ethanolamine (N,N-dimethyl-PE) and the anionic dimyristoylphosphatidic acid (DMPA). A monolayer of N,N-dimethyl-PE or DMPA incorporating BSA was transferred onto a solid substrate using the Langmuir-Blodgett technique. Atomic force microscopy (AFM) images of one-layer LB films displayed protein-phospholipid domains, whose morphology was characterized using dynamic scaling theories to calculate roughness exponents. For DMPA-BSA films the surface is characteristic of self-affine fractals, which may be described with the Kardar-Parisi-Zhang (KPZ) equation. On the other hand, for N,N-dimethyl-PE-BSA films, the results indicate a relatively flat surface within the globule. The height profile and the number and size of globules varied with the type of phospholipid. The overall results, from kinetics of adsorption on Langmuir monolayers and surface morphology in LB films, could be interpreted in terms of the higher affinity of BSA to the anionic DMPA than to the zwitterionic N,N-dimethyl-PE. Furthermore, the effects from such small amounts of BSA in the monolayer point to a cooperative response of DMPA and N,N-dimethyl-PE monolayers to the protein.     

Langmuir-Blodgett films of polymethacrylates with side chains containing functionalized aromatic schiff's bases

Langmuir-Blodgett (LB) film formation has been investigated for polymers in which non-linear optical (NLO) moieties are attached to the side chain of a polymethacrylate (PMA) backbone. Polymer monolayers were successfully transferred onto hydrophilic glass substrates using a moving-wall type LB trough. The LB films were characterized by pressure-area isotherms, polarized ultraviolet visible spectra, ellipsometry, and second harmonic generation measurements. The characterization shows that NLO moieties in the side chain are inclined at a shallow angle to the plane of the substrate. The second-order nonlinear optical coefficient and molecular hyperpolarizability were also calculated. © 1993 John Wiley & Sons, Inc.     

Molecular organization in binary mixtures of derivatives of naphthalenebicarboxylic acid and naphthoylenebenzimidazole with a liquid crystal in two-dimensional layers II. Langmuir-Blodgett films

Langmuir-Blodgett (LB) films of some dichroic dyes, namely derivatives of naphthalenebicarboxylic acid and derivatives of naphthoylenebenzimidazole, and of their mixtures with mesogens: 4-octyl-4'-cyanobiphenyl or 4-pentyl-4'-cyano-p-terphenyl were prepared. Absorption and fluorescence studies using unpolarized and linearly polarized light were carried out. Both absorption and fluorescence spectra indicated the formation of aggregates of dye molecules in monomolecular layers. Moreover, it was found that dye molecules are more tilted to the quartz surface in LB films than to the plane of the air-water interface in Langmuir films.     

Influential Factors of Low-energy C36 Cluster Deposition on Diamond (100) Crystal Plane

"Brenner-LJ potential is adopted to describe the interactivity between diamond and C36 cluster, and the deposition mechanism of multi-C36 on the diamond surface is researched by molecular dynamics simulation. Through simulative experiments the incident energy, incident point, incident posture, incident angle and other factors are analyzed. Studies discover that the minimal deposition threshold is 20 eV and the maximum is 60 eV with the different incident point locations and incident postures of C36 clusters. When the incident angle is not over 60ffi, C36 may roll or slip to the region of smaller bonding energy and then bond. So the bonding probability is raised. Research results show that when incident angle is between 0ffi and 20ffi and incident energy range is from 30 eV to 60 eV, it is the optimal condition of single C36 cluster deposition on diamond (100) crystal plane."     

Self-organization of a sulfonamido-porphyrin in Langmuir monolayers and Langmuir-Blodgett films

Langmuir monolayers (LM) and Langmuir-Blodgett (LB) films of pure lipophilic meso-tetra(4-dodecylaminosulfophenyl)porphyrin (PC12) and mixed with the anionic surfactant sodium hexadecylsulfate (SHS) were studied. The molecular packing and structure of PC12 and PC12-4SHS with variable surface pressure were investigated by surface pressure-area measurements, steady-state absorption, fluorescence emission and anisotropy, as well as by fluorescence lifetime imaging microscopy (FLIM). At low surface pressure, the porphyrin molecules are organized with the rings tilted on the water surface whereas at high surface pressure the porphyrin rings achieve a more perpendicular arrangement. Using the FLIM images a gradual change of aggregates into large "islands" is observed. Different patterns are observed in the pure PC12 multilayer films (n = 3 and 5) with ordered patches superimposed which are not observed in the PC12-4SHS multilayer LB films.     

Investigation of solid surfaces modified by Langmuir-Blodgett monolayers using sum-frequency vibrational spectroscopy and X-ray photoelectron spectroscopy

Langmuir-Blodgett (LB) monomolecular layers of alkylhydroxamic acids and alkylphosphonic acids on copper and iron substrates have been studied by X-ray photoelectron spectroscopy (XPS) and sum-frequency vibrational spectroscopy. According to the XPS results, the structures of the hydroxamic acid and phosphonic acid Langmuir-Blodgett films are very similar: the thickness of the layer of the hydrocarbon tails is typically 1.9-2.1 nm, while the layer of headgroups is about 0.3-0.35 nm thick. The tilt angle of the carbon chains is estimated to be 20-30 degrees with respect to the sample surface normal, and the molecules are connected to the substrate via their headgroups. Analysis of the P 2p and N 1s lines indicates the presence of deprotonated headgroups. The substrate Cu 2p line includes a component which can be assigned to Cu(2+) ions in a thin Cu(OH)(2) layer. The deposition of LB layers led to significant decrease of the hydroxide-related signal, which indicates that binding of the headgroups to the surface is accompanied by the elimination of water molecules. The sum-frequency spectra also clearly indicate that well-ordered monolayers can be formed by the Langmuir-Blodgett technique. Since the non-resonant background from the metal substrates renders the analysis of the spectra more difficult, model system samples on glass were prepared. It was found that the alkyl chains of the adsorbed acids predominantly adopt the all-trans conformation and form an ordered structure. Upper limits for the mean tilt angle of the terminal methyl groups are approximately 10-20 degrees.     

Columnar self-assembly and alignment of planar carbenium ions in Langmuir-Blodgett films

Structural and optical properties of multilayer Langmuir-Blodgett (LB) films of two amphiphilic carbenium salts 2-didecylamino-6,10-bis(dimethylamino)-4,8,12-trioxatriangulenium hexafluorophosphate (ATOTA-1) and 2,6-bis(decylmethylamino)-10-dimethylamino-4,8,12-trioxatriangulenium hexafluorophosphate (ATOTA-2) are described. The LB films were prepared on lipophilic glass by standard vertical dipping. Grazing incidence X-ray diffraction (GIXD) measurements show that the planar organic cores, in spite of their positive charge, form closely packed columns with a repeating distance of ～3.45 ?. Specular X-ray reflectivity (SXR) reveals the LB multilayers to consist of Y-type bilayers with thickness 31 ? for ATOTA-1 and 41 ? for ATOTA-2. This significant difference is ascribed to the different packing motifs of the alkyl chains in the two LB films. GIXD and polarized UV-vis absorption and emission spectroscopy show that the columnar aggregates in the LB films are oriented along the dipping direction. This alignment is attributed to shear effects during LB transfer. The main absorption band of the LB films is blue-shifted compared to that in solution, while the fluorescence is red-shifted by more than 100 nm. These findings suggest the presence of H-aggregates in agreement with the cofacial packing derived from the X-ray measurements. Polarized absorption spectroscopy with variable angle of incidence was used to resolve two perpendicular optical transitions in the visible range, one at 460 nm polarized perpendicular to the columnar direction, in the plane of the film, and one at 420 nm polarized along the film normal.     

双长链烷基稀土杂多酸化合物LB膜的制备、结构及性质研究

制备了三种新型双窗长链烷基稀土杂多酸化合物langmuir和langmuir-blodgett膜：DODA/Ln(PW~1~1)~2(Ln=La,Sm,Eu)。用π-A等温线,IR,UV,小角X射线衍射,荧光光谱,光电压谱对其进行了表征。结果表明：它们在空气-水界面有良好的成膜性能,这些单层在表面压为零时,表观单分子占有面积为0.45～0.50nm^2。LB膜有良好的层间有序性,稀土杂多酸阴离子是作为一无机层夹在两个双长链烷基层之间。DODA/Ln(PW)~1~1)~2LB膜具有Sm,Eu的特征荧光,其光电压谱亦有较强的光电响应。     

Effects of a central metal on the organization of 5,10,15,20-tetra-(p-chlorophenyl)-rare earth porphyrin hydroxyl compound at the air/water interface and in Langmuir-Blodgett films

Langmuir monolayers and Langmuir-Blodgett (LB) films of 5,10,15,20-tetra-(p-chlorophenyl) terbium/gadolinium porphyrin hydroxyl compound (TbOH and GdOH) and their mixtures with stearic acid (SA) in a molar ratio of 1:1 were investigated by Brewster angle microscopy (BAM), ultraviolet-visible (UV-vis), and infrared (IR) spectroscopy and atomic force microscopy (AFM). pi-A isotherms showed that well-defined Langmuir monolayers were formed at an air/water interface for the porphyrins and their mixture with SA. The BAM observations suggest that the pi-pi interaction between the GdOH molecules is stronger than that between the TbOH molecules. This result can be further confirmed by the AFM measurements. After the introduction of SA, the pi-pi interaction between the TbOH molecules is broken and thus two phases formed in the mixed LB film. However, it cannot break the stronger pi-pi interaction between the GdOH molecules. Therefore, no phase separation is observed in the GdOH/SA LB film. IR reflection-absorption (RA) spectra showed that the COOH groups of SA are partly converted to COO(-) groups, suggesting that there is an interaction between MOH and SA in the films. This interaction leads the benzene rings of TbOH to rotate toward parallel to the substrate and those of GdOH to rotate toward perpendicular to the substrate. All these results have demonstrated that the central metal ions have great effects on the organization and formation of the films.     

An infrared study on Langmuir–Blodgett films of 14,15-bis(hydroxyimino)-13-thiaoctacosane

The Langmuir–Blodgett (LB) films of 14,15-bis(hydroxyimino)-13-thiaoctacosane (TOC) on aluminium plated substrates were investigated using Fourier transform infrared (FTIR), grazing angle (GAIR) and horizontal attenuated total reflectance (HATR) techniques. The LB films of TOC can be transferred onto the solid substrate successfully. The molecular structure of LB films was analysis by comparing the GAIR and HTAR spectra. The intense bands at 2848 and 2918 cm⁻¹ are assigned to symmetric ν_s(CH₂) and asymmetric ν_a(CH₂) stretching vibrations of methylene groups. These peaks suggest that the alkyl chains in TOC are nearly in all-trans conformational state. The presence in the infrared spectra of several bands due to the methylene wagging and twisting modes and of the splitting of the bands due to the methylene scissoring mode at 1467 and 1459 cm⁻¹ and the CH₂ rocking mode at 720 and 731 cm⁻¹ also indicates that in films of TOC alkyl chains are in the all-trans conformation and packed in either an orthorhombic or a monoclinic structure with an orthorhombic subcell containing two mutually orthogonal molecules. Another conclusion presented in this paper that the alkyl chain tilt, which is the angle between the axis, which bisects the C–C bonds and the surface normal, was quite large by comparing the GAIR and HATR spectra.