Synthesis of ultrasmall magnetic iron oxide nanoparticles and study of their colloid and surface chemistry.

Colloidal nanoparticles of Fe(3)O(4) (4 nm) were synthesized by high-temperature hydrolysis of chelated iron (II) and (III) diethylene glycol alkoxide complexes in a solution of the parent alcohol (H(2)DEG) without using capping ligands or surfactants: [Fe(DEG)Cl(2)](2-) + 2[Fe(DEG)Cl(3)](2-) + 2H(2)O + 2OH(-) → Fe(3)O(4) + 3H(2)DEG + 8Cl(-) The obtained particles were reacted with different small-molecule polydentate ligands, and the resulting adducts were tested for aqueous colloid formation. Both the carboxyl and α-hydroxyl groups of the hydroxyacids are involved in coordination to the nanoparticles' surface. This coordination provides the major contribution to the stability of the ligand-coated nanoparticles against hydrolysis.