Chemistry Reference
In-Depth Information
to glass slides. This was done only on withdrawal across the interface. The slides
emerged wet and needed to be dried thoroughly before being dipped again (after
ca. 20 min). If the wet slide is dipped again without drying, the adsorbed film will
float off the support on the downstroke. This is a general behavior, as also observed
for different proteins (e.g., hemoglobin, BSA, ovalbumin, and lipids [lecithin, cho-
lesterol]) (Birdi, 1999). These LB films were prepared with films up to 160 lay-
ers. The visible spectra of 80 layers of bacteriorhodopsin/soya-PC showed a single
absorption band at λ
max
at 570 nm, and is identical to the spectrum of an aqueous
suspension of the purple membrane. The absorption at 570 nm was found to be lin-
early proportional to the number of LB layers. These analyses also indicated that
all bactriorhodopsin molecules at the interface remain spectroscopically intact.
The LB monolayers of dimethyldioctyadecylammonium ions on molecularly
smooth muscovite mica surfaces were investigated. Direct measurements of the inter-
action between such surfaces were carried out using the surface force apparatus. A
long-range attractive force considerably stronger than the expected van der Waals force
was measured. Studies on the electrolyte dependence of this force indicate that it does
not have an electrostatic origin but that the water molecules were involved in this.
The electrical potential across a LB film of dioleoyl-lecithin deposited onto a fine-
pore membrane, imposed between equimolar aqueous solutions of NaCl and KCl,
was reported to exhibit rhythmic and sustained pulsing or oscillations of electrical
potential between the two solutions. These oscillations were attributed to the change
of permeability of Na
+
and K
+
ions across the membrane, which originated from the
phase transition of lecithin.
The LB monolayers of cyanine dye have been studied by various methods. A new
method was proposed for preparing and removing the J aggregates of some cyanine
dyes that did not have long alkyl chains. The cyanine dye and arachidic acid were
mixed in a solution, and the film was deposited on a quartz plate by the LB method.
The dye molecules were found to be contained in the film, and some films showed a
remarkable J band and resonance fluorescence in the longer wavelength region than
in the corresponding monomer band.
Catalysis and LB
: Catalysis by electrodeposited platinum in an LB film on a
glassy carbon electrode were investigated (Birdi, 1999).
4.6.5 a
p p l I c aT I of n
of f
lb f
I l m S
I n
I
n d u S T r y
The LB film is thus seen to be a sensitive structure in which a layer of lipid can
be arranged on any solid. The applications of such structures in various industries
have been much exploited recently. Since even a single monolayer of lipid on a solid
surface (such as glass, metal, etc.) gives a large change in the contact angle of water,
indicating the potential of such a procedure.
Thin films of phthalocyanine compounds in general, and those prepared by the
LB method in particular, display novel electrical properties (Baker, 1985). The LB
technique for depositing mono- and multilayer coatings with well-controlled thick-
ness and morphology offers excellent compatibility with microelectronic technol-
ogy. Such films have recently been reviewed for their potential applications. The
combination of LB supramolecular films with small dimensionally comparable
Search WWH ::
Custom Search