SEMICONDUCTOR PARTICLES FORMED AT MONOLAYER SURFACES

Monolayers have been prepared from negatively charged arachidic acid (AA), bovine-brain phosphatidylserine (PS), n-hexadecyl-11-(vinylbenzamide)undecyl hydrogen phosphate (1), and positively charged dioctadecyldimethylammonium bromide (DODAB) and bis(2-(n-hexadecanoyloxy)ethyl)methyl(p-vinyl-benzyl)ammonium chloride (2) over aqueous 1.0 x 10(-3) M CdCl2, or ZnCl2, or CuSO4. Controlled and slow infusion of hydrogen sulfide onto compressed monolayers prepared from AA, PS, 1, and polymerized 1 resulted in the formation of semiconductor particles. In contrast, semiconductor formation could not be observed at the surfaces of monolayers prepared from positively charged DODAB and 2. Reflectivity and observed at the surfaces of monolayers prepared from positively charged DODAB and 2. Reflectivity and refractive index measurements provided information on the time-dependent growth of semiconductor particles. Sulfide nuclei, forming at the monolayer interface, rapidly grew to aligned microclusters that coalesced, predominantly two dimensionally, at the monolayer interface to an interconnected, porous, semiconductor particulate film. The optical thickness of the monolayer-supported particulate semiconductor film increased to a plateau value beyond which no additional semiconductor particle formation could be observed. Subsequent to exposure to the atmosphere, the optical thickness of the monolayer-supported semiconductor particulate film decreased, at a rate of ca. 10 angstrom/h, by spontaneous dissolution of the semiconductor particulates. Introduction of 10(-4) M CuSO4 into the subphase coated by a 225 angstrom thick CdS particulate film on a 1 monolayer resulted in the incorporation of copper ions into the semiconductor layer.