Understanding the optical spectroscopy of amphiphilic molecular rectifiers: a density functional approach.

We present results of first principles density functional theory calculations of the electronic and atomic structural properties of model Z-type Langmuir-Blodgett (LB) layers comprising amphiphilic quinolinium tricyanoquinodimethanide (Q3CNQ) chromophores. We find that the chromophore electronic ground state is not as clearly "zwitterionic" as required by models to explain electrical rectification purportedly seen in such systems. The computed visible region transitions are not what have been assumed to be the intervalence charge transfer bands seen in the visible region of molecules in Z-type LB films.

Surface anchoring structure of a liquid crystal monolayer studied via dual polarization interferometry.

The self-organization of liquid crystal molecules of 4- n -pentyl- 4' -cyanobiphenyl (5CB) forming an oriented monolayer by condensation from the vapor phase onto a silicon oxynitride surface has been observed using the evanescent wave dual slab waveguide dual polarization mode interferometry (DPI) technique. Two distinct stages to the layer formation are observed: After the formation of a layer of molecules lying prone on the surface, further condensation begins to densify the layer and produces a gradual mutual alignment of the molecules until the fully condensed, fully aligned monolayer is reached. At this limit the full coverage 5CB monolayer on this surface and at a temperature of 25 degrees C , is found to be anchored with an average molecular axis polar angle of 56+/-1 degrees and with a measured thickness of 16.