Size tailoring of oxide nanoparticles by precipitation in aqueous medium. A semi-quantitative modelling

Chemistry in aqueous solution is an easy and versatile method to form nanosized metal oxide particles. Considering our previous results on magnetite Fe3O4, anatase TiO2, brucite Mg(OH)2, and boehmite gamma-AlOOH, we show that the strict control of the physicochemical conditions of the precipitation, essentially the acidity and ionic strength in the absence of complexing species, enables the tailoring of the particle size in the range 2-15 nm and, in some cases, of their morphology. We show that the variations in size and/or shape are tightly related to the variation of the electrostatic surface charge density of the particles, which induces a variation of the oxide-solution interfacial tension, and, consequently, a decrease of the surface energy. Such an effect enables the control of the surface area of the system. A semi-quantitative model is presented, which accounts for the effects observed for particles isotropic or anisotropic in shape.