Monolayers multilayer stacks

D layered material. This would open up the rather attractive possibility of systematically exploring the dependence of a material s properties on its thickness, and of comparing the results obtained with multilayered stacks created from noncovalently bound monolayers with results obtained using the layer-by-layer (LBL) technique, whereby oppositely charged polyelectrolytes are deposited one on another in such a way that alternating layers with fuz2y boundaries are obtained [9,10]. The question is, are the properties affected in linear fashion with each added layer ... 

Another example of alcohol adsorption will be given from the data obtained for adsorption of benzyl alcohol on to alumina and well-crystallized kaolin (KGa-1) from carbon tetrachloride solutions. A SEM image of the alumina can be seen in Fig. 7. The mineral is a high-area form of aluminum oxide. Elemental analysis by X-ray fluorescence spectroscopy shows that the alumina surface contains more than 99.9% aluminum oxide. X-ray diffraction measurement indicates an amorphous surface structure. The adsorption isotherms for benzyl alcohol on to the alumina and the kaolin can be seen in Fig. 8. The isotherms are plotted on a log-log form in order to elucidate the region at low alcohol concentration. One can see that the shape of the isotherms represents typical multilayer adsorption with well-defined monolayer plateau sections. The plateaus represent the adsorption capacity of the minerals for monolayer adsorption. The data for the adsorption density at the plateaus correspond to an available area for each alcohol molecule of 0.54 nm. At higher alcohol concentrations, the increase in the adsorption densities represents a multilayered stacking of alcohol. 

As discussed in section 2.2, a mixture of AMP and AA showed two solid condensed phases above and below about 30 mN m- [5,10]. A loosely stacked structure of two porphyrins was proposed for LB films prepared at higher surface pressures than 30 mNmr1, which was caused by squeezing-out of a monomolecular structure formed at lower surface pressure [5,10]. In this section, photoelectric characteristics of LB films containing AMP and AA deposited at two solid condensed phases will be discussed in relation to multilayer structure and the anisotropic intermolecular tunneling rates [87]. Seven monolayers of 1 5 or 1 10 mixture of AMP and AA were deposited at 20 and 50 mN m-1 on an ITO plate at 18 °C to form stable Y-type LB films. Aluminum was vacuum evaporated onto LB films as sandwich-type electrodes at 10-6 Torr. Steady photocurrents were measured in a similar manner as mentioned above. 

The CgQ surface coverage was determined to be 2.0 10 mol cm . The monolayer can be further modified with monomeric amine reagents, which demonstrates the potential of the self-assembly process for growing three-dimensional fullerene structures. Different surfaces such as quartz. Si-oxide [105] or ITO [102] were coated with multilayers of fullerene up to stacks of 9 layers. An imidirectional electron transfer is possible across the fullerene mulhlayers [102]. Not only can multiple layers of fullerenes be connected to a certain surface but amino-functionalized can also serve as a linker between two different surfaces. 3-Aminopropyl-tethered glass plates could be linked via a Cgg layer to 3-aminopropyl covered zeolite crystals [106]. 

Exfoliation of the perovskite related layer structures is more difficult than for the clays and acid phosphates discussed earlier but can be achieved by intercalation of large bulky amines. Treacy etal. reported that the layered perovskite HCa2Nb30io could be made to form unilamellar sheets by first intercalation of an amine polyether. Spontaneous exfoliation of the layers occurs on subsequent exposure of the intercalated phase to a suitable solvent. Exfoliation techniques have been extended to other systems using tetra(n-butyl)-ammonium hydroxide (TBAOH) by Mallouk and others. A number of examples of the protonated layered perovskite phases that intercalate bases have been exfoliated. The Dion-Jacobson phases typically exfoliate to form plates but others including Ruddlesden-Popper tantalates curl to form tubular scrolls . Part of the interest in these single layer dispersions arises from their use as building blocks in the layer-by-layer self-assembly of thin films. Single layers derived from exfoliated perovskites can be attached to or alternately stacked with polycationic layers to produce thin films. Tiled monolayer structures and multilayer perovskite heterostructures result from the self-assembly. 

ID ordered lamellar phases are known as gel states, and occur when phospholipids are arranged into bilayers that then stack into a multilayer with each bilayer separated by water. The fatty acid alkyl side-chains are stiff and extended, as in the 3D and 2D lamellar crystal phases, but may undergo hindered rotations about their chain axes. There are a number of types of ID ordered lamellar phases depending upon the tilt angle 0 these are (0 = 0), (0 > 0) and an interdigitated phase L i (0 = 0) where fatty acid alkyl side-chains from different monolayers overlap with each other (Figure 1.91). One other ID ordered lamellar phase, Lg, is known, in which the fatty acid alkyl side-chains cease to be linear but adopt a helical conformation. 

Electronic microscopy investigation of gels revealed that the gel fibers have a multilayered structiu e. The STM study of monolayers of 156 physisorbed at the graphite/1-octanol interface showed at submolecular resolution the presence of sUghtly bent ribbons of 5-nm thickness formed by hydrogen bonded all-trans molecules. Subsequently, such ribbons stack to form mul-... 

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