Langmuir-Blodgett films surface pressure

Keywords Interface Langmuir monolayer Adsorption process Spreading solvent Surface tension Surface isotherm Langmuir-Blodgett film Collapse pressure Amphiphilic polymer... 

Langmuir-Blodgett films were prepared by spreading a 2 x 1(T4 M solution of the enantiomerically pure helicenebisquinone in chloroform onto a water surface. After evaporation of the solvent, the monolayer was compressed to a surface pressure of 20 mN/m. After stabilization for 30 min, the monolayers were transferred by the horizontal dipping method onto glass substrates, treated with octadecyltrichlorosilane to make them hydrophobic. 

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... 

Figure. 8.8 Comparison of high resolution AFM images of Langmuir-Blodgett films obtained from the air-water interface for three protein + Tween 20 systems (A) p-casein, 0.6 x 0.6 pm, surface pressure % = 20.6 mN/m (B) p-lactoglobulin, 0.8 x 0.8 pm, % = 26.1 mN/m (C) a-lact-albumin, 0.7 x 0.7 pm, % = 28.4 mN/m. Reproduced from Mackie et al (1999b) with permission.

Chi Jb was purchased from Sigma (St. Louis, MO) and was used without further purification. The photovoltaic cells were prepared by interposing the Langmuir-Blodgett films of Chi b between two dissimilar metal electrodes, i.e. aluminium and silver, with work functions ((()), such that A1 pigment Ag Both metal electrodes were evaporated under vacuum according to the method previously described. The active area of the cell is 0. 5 cm. Before the deposition of Chi b monolayer, the top aluminium electrode was covered with one monolayer of cadmium arachidate transferred at a surface pressure of 30 mN m l. The sandwich cells contained monolayers of Chi transferred on top of the arachidate layer at a surface pressure of 20 mN m l. 

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