Horizontal lifting technique

The films were deposited onto solid substrates by a horizontal lift technique. One layer was deposited for the gravimetric and fluorescence measnrements. Twenty layers were deposited for x-ray stndy. 

Several studies have been made of LB films of esters of naturally occurring polysaccharides. Kawaguchi et al. [242] formed long chain esters of cellulose which, however, could only be formed into multilayers by the horizontal lifting technique. Schoondorp et al. [243] studied LB multilayers of esters of amylose and showed that materials with short alkyl side chains have a helical conformation at the air/water interface and that this structure can be transferred into multilayers. As in the case of the isotactic polymethylmethacrylate, the helical structure appears to lead to an oriented structure in the LB film. These two families of materials are illustrated in Figure 5.9. 

Fig. 33. When the monolayers are transferred onto a gold substrate - at a surface pressure pertaining to the situations evidenced in Fig. 32a and b - by a horizontal lifting technique, a the tetracationic [2]catenanes can be seen to form a monolayer insulated from the gold surface by virtue of the aliphatic counterions, b The hexacationic [2]catenanes - less insulated from the gold surface - exhibit a linear current/voltage profile upon an applied potential, indicating their coupling to the gold surface...

Another way to reduce the mobility is by forming two-dimensional monolayers under ambient conditions. Adsorbate-substrate and adsorbate-adsorbate interactions lower the molecular mobility and are responsible for the two-dimensional ordering, Dry monolayers can be formed by drop casting and evaporation or by the horizontal lifting technique.It is also possible to measure... 

There will be some uncertainty as to the well initials, since the exploration and appraisal wells may not have been completed optimally, and their locations may not be representative of the whole of the field. A range of well initials should therefore be used to generate a range of number of wells required. The individual well performance will depend upon the fluid flow near the wellbore, the type of well (vertical, deviated or horizontal), the completion type and any artificial lift techniques used. These factors will be considered in this section. 

The other method of monolayer transfer from the air/water interface onto solid substrates is illustrated in Figure 2. This method is called the Langmuir-Schaefer technique, or horizontal lift. It was developed in 1938 by I. Langmuir and V. Schaefer for deposition of protein layers. Prepared substrate horizontally touches the monolayer, and the layer transfers itself onto the substrate surface. The method is often used for the deposition of rigid monolayers and for protein monolayers, hi both cases the apphcation of the Lang-muir-Blodgett method produces defective films. 

Variations on the vertical dipping technique have been utilized to construct films containing divalent metal ions. For example, the quartz crystal microbalance (QCM) has been used to evaluate the horizontal lifting method of CdSt LB Film construction (26). In this method, the QCM quartz plate was touched to monolayers compressed on a subphase and lifted horizontally. Y-type transfer (transfer ratio of 1) was demonstrated with two centrosymmetric monolayers deposited for each cycle. A combination of the vertical and horizontal dipping techniques has been utilized to prepare multilayer films from an amphiphilic porphyrin compound (27). 

The LB technique has conventionally been used to prepare monomolecular singlelayer and multi-layer films of surface active chemical species, such as phospholipids or fatty acids. Conventionally, the films are first prepared on surfaces of highly purified water, and then transferred therefrom to substrates of interest. Among common transfer techniques used are the vertical-transfer " Y-Type" (vertical up- and down-strokes, commonly used for hydrophobic species), X-type" and Z-type" (vertical up- and down-strokes only), and the horizontal-transfer "lifting technique (where the surface active species simply adheres to the horizontally placed substrate). 

It should be noted that Prasad and coworkers [16] have reported that LB films of poly(3-dodecylthiophene) can be prepared by the direct manipulation of neat surface films of this material. The transfer of these surface confined polymer molecules was accomplished with some difficultly via a horizontal film lifting technique. The current method of choice for fabricating LB films of the poly(3-alkyl thiophenes), however, is based on the manipulation of mixed monolayers. TMs latter method is extremely versatile, can be used to manipulate a wide variety of nonsurface active polythiophene derivatives, and delivers uniform thin films with high optical quality. 

Horizontal transfer (Schaefer s method). Another technique to prepare structures with LB (multi)layers is named after Schaefer [17]. This method is useful for depositing rigid films which can be described as two-dimensional solids. First, a compressed monolayer is established at the water-air interface. Subsequently a flat substrate is brought horizontally into contact with the film (figure C2.4.5). When the substrate is lifted and separated from the water surface a monolayer is transferred to the substrate while (theoretically) maintaining the molecular order. 

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