dm 03 FeCl 3 was aged at elevated temperature (8). If the A modified method was employed to prepare monodispersed unprecipitated Fe 3/ ions (ca. 80% in molar ratio) are recolloidal particles of ferric (hydrous) oxide. The method contains moved from the nuclei suspension after the nucleation prothree steps: (i) preparation of uniform nuclei of ferric hydrous cess, the size of the particles formed by redissolution-reoxide via a so-called instantaneous nucleation method; (ii) purificrystallization of the nuclei would probably be greatly decation of the nuclei suspension via dialysis; (iii) aging of the puricreased. Particle size would be further lowered down by fied nuclei suspension in a reflux reactor at certain pH. Cubic aging diluted nuclei suspension in the absence of Fe 3/ ions. and pseudocubic a-Fe 2 O 3 monodisperse particles which are much
In spite of the redissolution-recrystallization of the nuclei smaller than the cubic a-Fe 2 O 3 particles obtained from the same reactant through a usual method were produced by aging needle or small primary particles, the aggregation between them is like nuclei at a lower pH. A close-packed three-dimensional QDs also a widely investigated phenomenon, and many kinds of (quantum dots) superlattice structure 40 nm in edge length with monodispersed particles are known to be formed from pricubic geometry was formed by self-aggregation between spherical mary particles via aggregation (9-15), which has been reamorphous ferric hydrous oxide nuclei 3-5 nm in diameter. The viewed in a recently published paper (16). A recently regrowth processes of the two kind particles were also illustrated. ported result contributed by This study showed an approach to prepare smaller particles from suggested that, by controlled aggregation of surface-modiaqueous metal salt solutions in relatively higher concentration, fied CdSe nanoparticles (called ''quantum dots,'' QD) in and ordered QDs superlattice structure by controlled self-aggregaorganosol, a close-packed 3-D superlattice structure could tion of QDs in hydrosol.