Langmuir-Blodgett film characterization

Transmission electron microscopy (TEM) can resolve features down to about 1 nm and allows the use of electron diffraction to characterize the structure. Since electrons must pass through the sample however, the technique is limited to thin films. One cryoelectron microscopic study of fatty-acid Langmuir films on vitrified water [13] showed faceted crystals. The application of TEM to Langmuir-Blodgett films is discussed in Chapter XV. 

The area of colloids, surfactants, and fluid interfaces is large in scope. It encompasses all fluid-fluid and fluid-solid systems in which interfacial properties play a dominant role in determining the behavior of the overall system. Such systems are often characterized by large surface-to-volume ratios (e.g., thin films, sols, and foams) and by the formation of macroscopic assembhes of molecules (e.g., colloids, micelles, vesicles, and Langmuir-Blodgett films). The peculiar properties of the interfaces in such media give rise to these otherwise unlikely (and often inherently unstable) structures. 

Y. Hirata, M.-L. Laukkanen, K. Keinanen, H. Shigematsu, M. Aizawa, and F. Mizutani, Microscopic characterization of Langmuir-Blodgett films incorporating biosynthetically lipid-tagged antibody. Sens. Actuators B 76, 181-186 (2001). 

In situ Characterization of Langmuir-Blodgett Films by using a Quartz Crystal Microbalance as a... 

The application of FT-IR to a wide variety of interfacial phenomena is possible using either attenuated total reflectance (ATR) or grazing angle reflection -absorption. The details of these optical techniques are discussed in a subsequent chapter, in the context of characterization of Langmuir - Blodgett films and self-assembled mono and multilayers. However, ATR has been applied in a number of other areas which will be mentioned here. 

K. Ariga, Y. Okahata, In Situ Characterization of Langmuir-Blodgett Films diu-ing a Transfer Process. Evaluation of Transfer Ratio and Water Incorporation by Using a Quartz Crystal Microbalance , Langmuir, 10, 3255 (1994)... 

D.K. Schwairtz, Langmuir-Blodgett Film Structure, Surf. Set Reports 27 (1997) 245-334. (Review on structural and thermod5mamlc properties of LB films brief description of characterization techniques.)... 

Richardson, T., Roberts, G.G., Polywka, M.E.C., Davies, S.G. Preparation and characterization of organotransition metal Langmuir-Blodgett films. Thin Solid Eilms 160, 231-239 (1988)... 

Luk S Y, Mayers F R and Williams J O 1988 Preparation and characterization of Langmuir-Blodgett films of mesoporphyrin-IX dimethylester indium chloride Thin Solid Films 157 69-79... 

Ram M. K., Paddeu S., Carrara S., Maccioni E., and Nicolini C., Poly (ortho-anisidine) Langmuir-Blodgett films Fabrication and characterization, Langmuir, 13(10), 2760-2765, 1997. 

Due to the surface sensitivity surface enhanced fluorescence has become particularly popular in the characterisation of thin molecular films, such as Langmuir-Blodgett films and self-assembled biomembranes. Two surface enhanced spectroscopic techniques (surface enhanced IR absorption, SEIRA, and surface enhanced fluorescence, SEF) were recently applied to the study of biomembrane systems by the group of Reiner Salzer [323]. With SEIRA, specific fingerprints of biomolecules could be obtained with a tenfold IR intensity enhancement With SEF signal enhancement factors greater than 100 were obtained. The enhancement factor was very dependent on the properties and structure of the metal clusters used. With the two techniques biomembranes formed from vesicles with embedded nicotinic acetylchoHne receptors were spectroscopically characterized. 

Mattoso L. H. C., Mello S. V., Riul A Jn, Oliverira 0. N. Jn, and Faria R. M., nthesis and characterization of poly[o-phenetidineJ for the lubrication of Langmuir and Langmuir-Blodgett films. Thin Solid Films, 1994,244,714-717. 

Kim, J.H., et al. 1995. Preparation and characterization of poly(p-phenylene vinylene) Langmuir-Blodgett film formed via precursor method. Synth Met 71 2023. 

One core chiral system that shows dramatic amplification of its chiral structure is the substituted helicenes of Katz and coworkers [83]. In essence, this research cuts the helix into a number of six-helicene subunits that self-assemble (Figure 10). Only when these subunits, which look like lock washers, are prepared in optically pure form the material associates into supramolecular helical columns [84]. The assemblies have been synthesized with different amounts of substitution around the exterior. Depending on the helicenes substitution, the material exhibits hexagonally ordered soft-crystalline [84] or liquid-crystalline phases [85]. The liquid-crystalline versions of these molecules switch when electric fields are applied to neat and solution-phase samples and have been characterized as a dielectric response [85-87]. Upon association, these materials have enormous changes in their CD intensities and optical rotations [74]. In addition, this supramolecular chirality also significantly enhances the second-order nonlinear optical behavior of these materials in Langmuir-Blodgett films [88]. 

Despite their potential importance, there are few spectroscopic studies of polymerizable surfactants. The only well-characterized polymerized surfactants are the polydiacetylenic fatty acids. The polymerization mechanism (1,4 addition) was only recently discovered as a result of studies on crystals of non-surfactant monomers which become brightly colored on polymerization [1], indicating the formation of polymer concurrent with a solid-solid phase transition. Several groups, particularly that of Ringsdorf, have pioneered the study of polydiacetylenic fatty acids [2-5]. A significant amount of spectroscopic work has been done on non-surfactant polydiacetylenes [6-9]. In addition, Lando and co-workers have used electron diffraction from mono- and bilayers of fatty acids to establish the conformation of the diacetylene backbone chains in this ordered surfactant system [10,11], and others have performed Raman spectroscopy on Langmuir-Blodgett films of similar surfactants [12]. This provides one with a powerful "basis set" of information from which to study other polydiacetylenic systems. 

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