FORMATION OF NANOPARTICULATE FE2O3-STEARATE MULTILAYER THROUGH THE LANGMUIR-BLODGETT METHOD

Stable nanoparticulate alpha-Fe2O3-stearate (Fe2O3-St) monolayers can be obtained by using nanoparticulate alpha-Fe2O3 (diameter 70 angstrom) as the subphase. The area extrapolated to pi = 0 is 27 angstrom 2 per hydrocarbon chain of the monolayer. The "collapse" pressure is about 28 dyn/cm. The transfer ratio is 1.0 +/- 0.1 (this is a constant within the limit of experiment). The long spacing of the multilayer determined by X-ray diffraction is 160 angstrom. The tilt angle of the hydrocarbon chains revealed by IR is 31-degrees +/- 5-degrees. The long CH2 sequence of the hydrocarbon chains of the multilayer is in a trans planar structure. The surface coverage by Fe2O3 nanoparticles is very large (more than 90%). Stearic acid is converted to stearate ion almost completely and chemical bonds were formed between Fe2O3 and stearate ions. The particles in the polar plane of the multilayer are close packed in a hexagonal close packed (hcp) bilayer structure. The total thickness of the multilayer can be several thousand angstroms or more. The absorption and transmission properties of isolated nanoparticulate Fe2O3 hydrosol were maintained. Thus the multilayer can be regarded as a three-dimensional superlattice of quantum size particles.