Monolayers anisotropy studies

The angles 6ex and 6em are the transition moment angles for excitation and emission respectively with respect to the center of the motional cone axis, with 9ex = 0° and 0em = S in this instance. The average tilt angles of the chromophores within the monolayers are provided in Table 5.3. Fluorescence anisotropy studies on BDP and QDP monolayers on silica reveal no decay of R(t), implying there is no chromophore motion on the time-scale being investigated. 

The anisotropy in the physicochemical surface properties and differences in the surface topography of S-layer lattices allowed the determination of the orientation of the monolayers with respect to different surfaces and interfaces. Since in S-layers used for crystallization studies the outer surface is more hydrophobic than the inner one, the protein lattices were generally oriented with their outer face against the air-water interface [120,121]. Crystallization studies with the S-layer protein fromB. coagulansE i Nl at different lipid monolayers [122] revealed that the S-layer lattice is attached to lipid monolay-... 

Using optieal microscopie teehniques (fluorescence microscopy, Brewster angle microseopy and microscopic ellipsometry) the formation, size and shape of domains in the LE-LC coexistence region of phospholipid monolayers have been studied extensively. Furthermore, structures within condensed domains and phases have been visualized, the contrast resulting from the optical anisotropy caused by long-range tilt orientational order. 

Monolayers of ethyl palmitate and ethyl stearate are attractive systems in which to study internal domain anisotropy by BAM. Monolayers of these compounds have two-phase coexistence regions between the LE and EC... 

While many studies of monolayers using BAM descriptively report the microstructures observed, a more quantitative analysis of the BAM images can yield information on thickness changes in monolayers and has been referred to as quantitative BAM. Quantitative BAM can be applied using a simple optical model for films at the water-air interface in which there is no or negligible anisotropy within the film. The measurement requires that a calibration be performed to calibrate gray-scale intensities from pixels in the image with calculated values of reflectivity, and the conduct of such a calibration has been reported. " Quantitative... 

The highly anisotropic nature of PDA films allows us to show that in-plane properties of materials can be observed using IC-AFM. This is due to the tilt of the AFM cantilever which produces a small but significant in-plane component to the tip s motion. In the case of PDA monolayers, in-plane Action and shear deformation anisotropy leads to contrast in the IC-AFM phase image. The results can be explained using a sinq)le model that incorporates Hertzian contact mechanics with in-plane dissipation, and may be generalized to the study of other anisotropic materials. 

---