Size-Tunable Fe3O4 Spherical Nanoclusters Through a One-Pot Hydrothermal Synthesis.

A new method is presented for the synthesis of monodisperse, size-tunable Fe3O4 spherical nanocluster particles through a simple, one-step hydrothermal reaction, according to a kinetics-controlled self-assembly process of smaller nanocrystals into hierarchical mesoporous aggregates. The mean diameter of the particles can be controlled over a broad range up to similar to 230 nm by simply varying the concentration of the precipitating reagent (urea or ammonia). The particles can be easily dispersed in water with excellent colloidal stability, exhibit a high surface area of similar to 60 m(2) g(-1), and demonstrate size-dependent magnetic separation kinetics, where the larger nanoclusters exhibit rapid magnetophoresis, and the smaller nanoclusters remain inseparable. Thus particle size control is essential for improving magnetic separation processes.