A process for the preparation of a self assembled superlattice thin film
of organic nanocrystal particles is described comprising: (i) combining
one or more functional organic material to be precipitated as nanocrystal
particles and one or more surface active material in a compressed
CO.sub.2 phase with a density of at least 0.1 g/cc, where the functional
material is substantially insoluble in the compressed CO.sub.2 in the
absence of the surfactant, the surfactant comprises a compressed
CO.sub.2-philic portion and a functional material-philic portion, and the
compressed CO.sub.2 phase, functional material and surfactant interact to
form an aggregated system having a continuous compressed CO.sub.2 phase
and a plurality of aggregates comprising surfactant and functional
material molecules of average diameter less than 50 nanometers dispersed
therein; (ii) rapidly depressurizing the compressed CO.sub.2 phase
thereby precipitating the dispersed functional and surfactant materials
in the form of composite organic nanocrystals of average diameter less
than 50 nanometers, and (iii) depositing the organic nanocrystals on a
substrate surface, wherein the organic nanocrystals form a thin film
having an ionic content of less than 0.001 M in equivalent sodium
chloride concentration on the substrate surface, and the thin film
exhibits a long range periodicity in the arrangement of the organic
nanocrystals in a self assembled superlattice structure, as evidenced by
x-ray diffraction.
