SYNTHESIS OF UNIFORM FERRIC-OXIDE PARTICLES FROM DEIONIZED COLLOIDS

A modified method was employed to prepare monodispersed colloidal part icles of ferric (hydrous) oxide, The method contains three steps: (i) preparation of uniform nuclei of ferric hydrous oxide via a so-called instantaneous nucleation method; (ii) purification of the nuclei suspe nsion via dialysis; (iii) aging of the purified nuclei suspension in a reflux reactor at certain pH. Cubic and pseudocubic alpha-Fe2O3 monod isperse particles which are much smaller than the cubic alpha-Fe2O3 pa rticles obtained from the same reactant through a usual method were pr oduced by aging needle like nuclei at a lower pH, A close-packed three -dimensional QDs (quantum dots) superlattice structure 40 nm in edge l ength with cubic geometry was formed by self-aggregation between spher ical amorphous ferric hydrous oxide nuclei 3-5 nm in diameter, The gro wth processes of the two kind particles were also illustrated, This st udy showed an approach to prepare smaller particles from aqueous metal salt solutions in relatively higher concentration, and ordered QDs su perlattice structure by controled self-aggregation of QDs in hydrosol. (C) 1997 Academic Press.