Taking Advantage of Electrostatic Interactions To Grow Langmuir-Blodgett Films Containing Multilayers of the Phospholipid Dipalmitoylphosphatidylglycerol

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Preparation and gas sensitivity of octa-n-butoxy-2,3-naphthalocyanine copper(II) Langmuir-Blodgett film

The formation process of monolayer of octa-n-butoxy-2,3-naphthalocyanine copper ( I), [CuNc(OBu)(8)], on water subphase was studied. Its multilayers were successifully deposited on the hydrophilic substrates by Z-type deposition mode using LB technique. Stable solid film with a limiting molecular area of 0.74 nm(2) and a collapse pressure of 55 mN/m were formed. The LB film structure was characterized by IR and electronic absorption spectra. Macrocycle of CuNc (OBu)(8) molecules have a face-to-face arrangement in the multilayers. These films have good sensitivities to vapor of alcohols, with the following sequence of sensitivities: i-PrOH>EtOH>MeOH. The response time and recovery time of the LB films to vapor of MeOH, EtOH and i-PrOH[volume fraction (1-5) X 10(-5)] were within 2 and 5 seconds respectively, while those of the LB films to ammonia(1 X 10(-4)) were 30-60 seconds and 4-5 minutes respectively.

Fabrication and characterization of heteropolyanion Langmuir-Blodgett films

The possibility of the formation of Langmuir-Blodgett (LB) films with dimethyldioctadecylammonium (DODA) after the addition of cobalt(II)-substituted Dawson-type tungstodiphosphate anion (briefed as (H2O)(CoP2W17O618-)-P-11) in the subphase has been explored. Marked modifications of the compression isotherms are observed when this anion is dissolved in the subphase, which demonstrates that the polyanions interact with the monolayers. LB films have been readily obtained from this system. The adsorption Fourier transform IR (FT IR) spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD) and cyclic voltammetry (CV) have been used to investigate the morphological and molecular structure of the deposited film. The FT IR results showed the presence of the polyanion within the LB films, and the shift for its characteristic bands may be related to the presence of positively charged DODA. AFM measurement reveals that the LB films of DODA/(H2O)(CoP2W17O618)-P-II are regularly and uniformly deposited on the substrate. XRD experiments prove that the lamellar structure of the LB films of DODA/(H2O)(CoP2W17O618-)-P-II is well-defined. The LB films of DODA/(H2O)(CoP2W17O618-)-P-II immobilized onto an indium-oxide (ITO) glass, in aqueous solutions of pH 2.0-5.0, show quite facile redox reactions even for multilayers. All the experiments carried out in the present study suggest that the new materials of heteropolyanions can be formed by LB techniques and beneficial physicochemical properties of heteropolyanions can be maintained/enhanced through molecular-level design. (C) 1999 Elsevier Science S.A. All rights reserved.

PREPARATION AND CHARACTERIZATION OF LANGMUIR-BLODGETT-FILMS OF PORPHYRINS WITHOUT LONG ALKYL CHAINS

A number of synthetic and natural source porphyrins without long alkyl chains have been examined in the form of monolayers and multilayers on solid substrates. These compounds formed stable solid condensed films with measured molecular areas compatible with a vertical or tilted orientation of these molecules on the substrate. Spectral study and fluorescence lifetime measurement, in particular, revealed the formation of aggregates as the main species in these films.

Structure and thermal stability of Langmuir-Blodgett films of barium arachidate

The structures of multilayer Langmuir-Blodgett films of barium arachidate before and after heat treatment have been investigated using both atomic force microscopy (AFM) and grazing incidence synchrotron X-ray diffraction (GIXD). AFM gave information on surface morphology at molecular resolution while GIXD provided quantitative details of the lattice structures of the films with their crystal symmetries and lattice constants. As-prepared films contained three coexisting structures: two triclinic structures with the molecularchains tilted by about 20degrees from the film normal and with 3 x 1 or 2 x 2 super-lattice features arising from height modulation of the molecules in the films; a rectangular structure with molecules perpendicular to the film surface. Of these, the 3 x 1 structure is dominant with a loose correlation between the bilayers. In the film plane both superstructures are commensurate with the local structures, having different oblique symmetries. The lattice constants for the 3 x 1 structure are a(s) = 3a = 13.86 Angstrom, b(s) = b = 4.31 Angstrom and gamma(s) = gamma = 82.7degrees; for the 2 x 2 structure a(s) = 2a = 16.54 Angstrom, b(s) = 2b = 9.67 Angstrom, gamma(s) = gamma = 88degrees. For the rectangular structure the lattice constants are a = 7.39 Angstrom, b = 4.96 Angstrom and gamma = 90degrees. After annealing, the 2 x 2 and rectangular structures were not observed, while the 3 x 1 structure had developed over the entire film. For the annealed films the correlation length in the film plane is about twice that in the unheated films, and in the out-of-plane direction covers two bilayers. The above lattice parameters, determined by GIXD, differed significantly from the values obtained by AFM, due possibly to distortion of the films by the scanning action of the AFM tip. (C) 2004 Published by Elsevier B.V.

Langmuir-Blodgett 薄膜诱导晶体生长研究

近年来，Langmuir—Blodgett（LB）薄膜诱导晶体生长的方法引起了人们的极大关注。通过优化LB膜的结构和化学性质可以调控晶体的结构、形貌、取向、晶型。本论文在此领域的主要研究内容如下： (1) 制备了硬脂酸和十八胺两种具有不同结构和官能团的LB膜，然后把这两种膜垂直浸入到中性的甘氨酸溶液中。实验结果表明用不同结构和化学性质的LB膜不仅可以调控晶体的结构、形貌和取向，并且可以在相同的溶液中诱导出不同晶型的晶体。 (2) 制备了Y型硬脂酸LB膜，然后把这种模板以不同的方式浸入到氯化钾溶液中。通过改变LB膜模板在溶液中的放置方式，控制溶液中的诱导成核和自发成核的过程，从而生成不同形貌的氯化钾晶体。 (3)我们研究了不同热力学状态的LB膜诱导五水硫酸铜晶体生长过程。结果表明LB膜即使在液态状态下，仍有诱导晶体生长的能力。且LB膜的热力学状态对晶体的形貌和取向有很大的影响。 另外，我们在以上工作之外，还作了两项其他工作。 (4) 研究了各种羧酸类（甲酸、乙酸、丙酸）、丙酮、醇类（甲醇、乙醇、丙醇、丁醇）对谷氨酸溶液结晶晶型的影响。结果表明：当70°C的谷氨酸饱和溶液快速冷却搅拌到0°C时，有羧酸类物质存在时可以得到β型晶体;而当有酮类、醇类、或无添加剂时在相同条件下得到α型晶体。 (5) 利用LB技术制备了聚苯乙烯和硬脂酸的混合薄膜。实验结果证明PS和SA在混合LB膜中是相分离的。其过程是PS在空气/水界面上首先发生聚集,然后这种聚集的程度随着膜压的增加而增大.并且PS在空气-LB膜界面上在空气/LB膜界面上的聚集程度随着时间仍继续发生改变。

十八胺及其相关物质Langmuir-Blodgett膜的制备和性质研究

Langmuir-Blodgett（LB）膜技术由于在电子学、非线性光学以及化学传感器等领域具有潜在的应用前景而引起了人们的研究兴趣，其中它的热稳定性对LB膜的应用领域和范围具有一定的影响。本论文在此领域的主要研究内容如下： 利用LB膜技术分别制备了十八胺及硬脂酸、氘代硬脂酸的多层LB膜，采用变温傅立叶变换红外光谱研究了三种LB膜的相变行为。实验发现：十八胺LB膜在55-75 oC温度区间内发生相变，其CH2对称和反对称伸缩振动频率向高能量区发生明显移动；硬脂酸LB膜在70-80 oC的温度区间内发生了明显的相转变，CH2对称和反对称伸缩振动的强度比在升温过程中也有显著改变；氘代硬脂酸LB膜的相行为发生在65-70 oC的温度区间内。 利用LB膜技术制备了十八铵硬脂酸盐(C18H37NH3+C17H35COO-, ODASA)与十八铵氘代硬脂酸盐(C18H37NH3+C17D35COO-, ODASA-d35) Langmuir-Blodgett (LB)膜，使用变温傅立叶变换红外透射光谱研究了它们的热行为。发现LB膜中十八铵硬脂酸盐分子的两个碳氢链高度有序，然而在十八铵氘代硬脂酸盐LB分子中的来自于十八胺的碳氢链部分无序，即在常温下有一些扭曲构象存在于碳氢链中。而十八铵硬脂酸盐的热稳定性也与十八铵氘代硬脂酸盐的热稳定性有些不同。在十八铵硬脂酸盐LB膜中，碳氢链在85 oC到90 oC的温度区间内发生非常明显的有序-无序变化。而在十八铵氘代硬脂酸盐LB膜中，碳氢链和来自于硬脂酸的氘代的烃链各自呈现出不同的热行为，即：碳氢链在80-90 oC的温度区间发生有序-无序变化，尤其是在80-85 oC的温度范围内这个变化非常显著；而氘代的烃链则在70 oC到85 oC这个较长的温度区间发生缓慢的相变。 分别制备了十八铵十二酸盐 （C18H37NH3+C11H23COO-，ODALA）和十八铵二十四酸盐（C18H37NH3+C23H45COO-,ODATA）LB膜，并用变温傅立叶变换红外透射光谱法研究了十八铵十二酸盐和十八铵二十四酸盐LB膜的热行为，比较了十八铵十二酸盐、十八铵硬脂酸盐和十八铵二十四酸盐这三种双链化合物LB膜的热行为。温度相关的红外光谱显示，这三种物质LB膜的热稳定性取决于碳链的长度。其中，十八铵十二酸盐LB膜在50-65 oC的温度区间内发生相变。对应的，十八铵二十四酸盐LB膜在80-90 oC的温度范围内发生有序-无序变化。令人感兴趣的是，十八铵二十四酸盐LB膜的相变温度与十八铵硬脂酸盐LB膜的相变温度基本一样，都是80-90 oC，也即在十八铵二十四酸盐和十八铵硬脂酸盐两种LB膜中，即使二十四酸取代了硬脂酸对前者的热稳定性的影响非常小。以上结果说明，在双长链化合物中，有效链长度取决于双链中的较短的那个烃链，从而来决定膜的热稳定性。在十八铵二十四酸盐LB膜中，十八胺的全部碳链对膜的热稳定性有贡献，而二十四酸的碳链则只有部分（有效部分）烃链有贡献。 制备了十八胺单层和多层LB膜和粒径为几个纳米的金纳米粒子。由于十八胺在pH值小于10.3的溶液中氨基带正电荷，使其置于金纳米溶胶中，利用带正电荷的十八胺和附着负电荷的金纳米粒子之间的静电作用，使得金纳米颗粒成功地吸附组装到十八胺的有序分子膜中，形成有规律的纳米颗粒层。通过紫外-可见光谱、红外光谱以及扫描电镜观察到，金纳米颗粒通过这种方法能够很好的组装在有机分子膜上，而且由于十八胺LB膜的高度有序性使得金纳米颗粒的组装层有序。而且，不同层数的十八胺LB膜对金纳米粒子呈现出不同的吸附行为。 测量了含微量甲醇（体积分数为0.04%~0.24%）的系列乙醇水溶液的近红外光谱，利用近红外光谱分析建立了预测甲醇含量的定量分析模型。比较了用外部检验法（Test Set-Validation）和交叉检验法(Cross-Validaton)建立的数学模型以及研究了使用外部检验法时校正集和检验集样品数的改变对模型预测结果的影响。结果发现，当校正集样品数为15检验集样品数为6（总样品数为21）时，使用外部检验法建立的数学模型预测结果较好，外部检验与交叉检验的预测均方根误差（分别为RMSEE和RMSEP）都较小（分别为0.0105和0.0115）而且很接近。结果表明，近红外光谱方法简单，准确而且实用。

Nucleation and growth of CUSO4 center dot 5H(2)O crystals on the liquid state stearic acid Langmuir-Blodgett film

Oriented crystallization of CUSO4 center dot 5H(2)O on a Langmuir-Blodgett (LB) film of stearic acid has been studied in the temperature ranges of 73-68 degrees C and 53-20 degrees C, respectively. This is the first time that the LB film at temperature above its melting point has been served as a template to induce nucleation and growth of crystals. The experimental results demonstrated that the LB film in the liquid state has the ability of directing the nucleation and growth of crystals. Moreover, X-ray diffraction patterns of the as prepared crystals revealed that the orientation of the attached crystals on the LB film is affected by temperature greatly.

Control for oriented growth of large size KCl crystals by the competition between spontaneous and induced nucleation/growth on a Langmuir-Blodgett film

Langmuir-Blodgett (LB) film of stearic acid was used as template to induce the nucleation and growth of KCl crystals when the KCl solution was cooled from 50 to 25 degrees C. When the LB film template was vertically dipped into the solution, only induced crystals with (1 1 0) orientation were formed. However, if the template was horizontally placed into solutions, both the induced nuclei at the solution/film interface and spontaneous nuclei formed in solution were simultaneously absorbed onto the LB film, and then grew further to form crystals. X-ray diffraction (XRD) patterns and optical microscopy images showed that the orientation and morphology of the crystals were controlled properly by changing the orientation and position of the LB films in the solutions.

Infrared spectroscopic study on thermal behavior of Langmuir-Blodgett films of octadecyl ammonium octadecanoate and octadecylammonium octadecanoate-d(35)

Langmuir-Blodgett (LB) films of octadecylammonium octadecanoate (C(18)H(37)j7NH(3)(+)C(17)H(35)COO(-),ODASA) and octadecylammonium octadecanoate-d(35) (C18H37+NH3+C17D35COO-, ODASA-d(53)) were prepared and their thermal behaviors were investigated by variable-temperature Fourier transform infrared transmission spectroscopy. It was found that the two hydrocarbon chains of ODASA molecule in LB films are highly ordered while that protonated (H) chain in ODASA-d(35) is partially disordered with some gauche conformers introduced at room temperature.

Nucleation and growth of glycine crystals with controllable sizes and polymorphs on Langmuir-Blodgett films

Control of crystal polymorph and size is very important in many application fields. Herein we demonstrate that Langmuir-Blodgett (LB) films of stearic acid (SA) and octadecylamine (ODA) can serve as templates and generate different polymorphs of glycine crystals. In the neutral aqueous solutions, gamma-glycine crystallizes on LB films of ODA while the polymorphic outcome becomes the (x-form on LB films of SA. These observed results could be explained by the electrostatic interactions and geometric lattice matching at the LB film/crystal interfaces, respectively. By keeping the appropriate supersaturation, we have successfully controlled the number of crystals grown on LB films; for example, in some certain cases, only one piece of crystal was grown on LB films in solution. Therefore, large crystals of centimeter size could be prepared. These experimental results suggest a new approach to produce an organic crystal with bulk scale.

An infrared study on Langmuir-Blodgett films of octadecylammonium octadecanoate: FWHM and the vibrational coupling

The monolayer of the mixture of octadecanoic acid and octadecylamine with molar ratio 1: 1 has been investigated at the air-water interface. It was found that the monolayer shows a rather stable state at the surface pressure of 30 mN/m and this monolayer can be transferred onto a CaF2 plate by Langmuir-Blodgett (LB) technique. The infrared spectra of LB films indicated that octadecyl ammonium octadecanoate is formed by an intermolecular proton exchange between adjacent carboxylic and aminic groups (COO- and NH3+). In three-layer LB film, the CH2 scissoring mode of the long hydrocarbon chains of octadecyl ammonium octadecanoate shows a broad band feature at about 1468 cm(-1) while this vibrational mode of three-layer LB film of the mixture (1: 1) of deuterated stearic acid and octadecylamine (octadecylammonium octadecanoate-d35, C18H37NH3+C17D35COO-) only shows a narrow band. The broad feature of the CH2 scissoring mode in octadecylammonium octadecanoate probably originates from the coupling between the chain of stearic acid and that of octadecylamine while this kind of coupling could be completely removed in octadecylammonium octadecanoate-d35.

2-十八烷基-7,7,8,8-四氰基对苯二醌二甲烷和3,3',5,5'-四甲基连苯胺电荷转移配合物Langmuir-Blodgett膜的制备及光谱研究

本文利用Langmuir-Blodgett技术制备2-十八烷基-7,7,8,8-四氰基对苯二醌二甲烷和3,3',5,5'-四甲基连苯胺电荷转移配合物超薄膜.并利用红外光谱和紫外-可见-近红外光谱研究其分子取向及结构.