Langmuir-Blodgett films layers

NANOSCALE LANGMUIR-BLODGETT FILMS AS SENSITIVE LAYERS OF CHEMICAL SENSORS... 

Langmuir-Blodgett films (LB) and self assembled monolayers (SAM) deposited on metal surfaces have been studied by SERS spectroscopy in several investigations. For example, mono- and bilayers of phospholipids and cholesterol deposited on a rutile prism with a silver coating have been analyzed in contact with water. The study showed that in these models of biological membranes the second layer modified the fluidity of the first monolayer, and revealed the conformation of the polar head close to the silver [4.300]. 

FIG. 13 Langmuir-Blodgett films of dioctadecyldimethylammonium bromide incorporating 6.0-nm-diameter CdS nanoparticles stabilized by 0.2 mM sodium hexametaphosphate. (a) Absorbance spectra for 2, 3, 4, 5, 6, 7, 8, and 13 layers (bottom to top) the inset shows the linearity of the absorbance at 450 nm versus the number of layers, (b) Fluorescence spectra (excitation wavelength = 400 nm) for 2, 3, 4, 6, 8, 13, and 18 layers (bottom to top) the inset shows the emission intensity at 480 nm versus the number of layers. (Reproduced with permission from Ref. 152. Copyright 1994 American Chemical Society.)... 

Langmuir-Blodgett films of iron(III) arachidate have been used as precmsors for the production of ultrathin layers of iron oxide for potential use as magnetic storage media... 

FIG. 1 Geometries of electrolyte interfaces, (a) A planar electrode immersed in a solution with ions, and with the ion distrihution in the double layer, (b) Particles with permanent charges or adsorbed surface charges, (c) A porous electrode or membrane with internal structures, (d) A polyelectrolyte with flexible and dynamic structure in solution, (e) Organized amphophilic molecules, e.g., Langmuir-Blodgett film and microemulsion, (f) Organized polyelectrolytes with internal structures, e.g., membranes and vesicles. 

Multilayer Langmuir-Blodgett films doped with a cyanine dye have been deposited on the surface of a quartz multimode optical fiber and the fluorescence properties investigated. 49 The fluorescence intensity of the films was found to be a periodic function of the number of layers due to the waveguide properties of the films. 

This cross-sectional mismatch between the small anchor and the large dendritic component modified the intermolecular packing in the Langmuir-Blodgett mono-layer and film so that sufficient mobUity was present near the azobenzene group. This mobility greatly facihtated efficient molecular reorganization in response to E Z photoisomerization. 

When some NC particles are surface treated to make them hydrophobic by, e.g., silylation and floated on the surface of water, a nanoparticle layer can be made on a solid substrate by a method similar to Langmuir-Blodgett film formation. Interparticle separation is well controlled by choosing an appropriate surface pressure prior to making LB film, as discussed next. 

Thin films of materials play an important role in modern electronics. Langmuir-Blodgett films (Mort, 1980) are prepared from surface-active molecules that adsorb at the surface of an aqueous solution. The surface is gently compressed to produce a close-packed monolayer, which can be coated on appropriate substrates by dipping at constant surface pressure. The layers so produced are of a precise thickness, and repeated dipping gives multilayers. For example, diacetylenes and other polymerizable... 

What are Langmuir and Gibbs layers What is a Langmuir-Blodgett film How do they differ from each other ... 

Chapter 7 now includes an introduction to structural transitions in Langmuir layers and examples of applications of Langmuir and Langmuir-Blodgett films. 

Extremely low interaction forces in monomolecular adsorption layers on liquids, Langmuir Blodgett films or in solid interfaces are the precondition for low energy surfaces. Perfluorocarbons or terminal fluorinated parts in amphiphilic molecules and fluoropolymers meet these demands. 

Figure 4.1. Schematic diagram of the formation of a Langmuir-Blodgett film. Each amphiphilic molecule is represented by a circle with a tail, where the circle denotes the hydrophilic end of the molecule. The left hand diagram represents the deposition of a monolayer on a hydrophilic substrate moving upwards. The right hand diagram represents the deposition of a second layer during the downward movement of the substrate.

---