Langmuir—Blodgett transfer process

The artificial lipid bilayer is often prepared via the vesicle-fusion method [8]. In the vesicle fusion process, immersing a solid substrate in a vesicle dispersion solution induces adsorption and rupture of the vesicles on the substrate, which yields a planar and continuous lipid bilayer structure (Figure 13.1) [9]. The Langmuir-Blodgett transfer process is also a useful method [10]. These artificial lipid bilayers can support various biomolecules [11-16]. However, we have to take care because some transmembrane proteins incorporated in these artificial lipid bilayers interact directly with the substrate surface due to a lack of sufficient space between the bilayer and the substrate. This alters the native properties of the proteins and prohibits free diffusion in the lipid bilayer [17[. To avoid this undesirable situation, polymer-supported bilayers [7, 18, 19] or tethered bilayers [20, 21] are used. 

We review useful usages of a quartz crystal-microbalnce (QCM) as tool of in situ characterization of Langmuir-Blodgett (LB) films transfer ratio and water incorporation during a transfer process, swelling behavior in water subphase, and detachment at the air-water interface. 

If preparation of thicker films is desirable, this process can be repeated. It should be noted, however, that on the subsequent immersions of the substrate, its surface is hydrophobic therefore, the film is going to be transferred on both inwards and outwards trips. This results in the number of layers in a Langmuir-Blodgett (LB) film typically being odd. If, for some reason, a film with an even number of layers is required, then a hydrophobic substrate should be chosen, which enables transfer of the film during the first immersion as well. 

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)... 

The photochemical processes occurring in thin films deposited on metal surfaces such as Ag and Au has been reveiwed3. In general, the photochemistry is subject to quenching of the photoprocess by the surface or the reverse of this where an electron transfer process becomes important. The films on the metal surface can be either physisorbed as in Langmuir-Blodgett systems or can be chemisorbed as in thin films of thiols or carboxylic acids, for example. 

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