Oleate-Based Solvothermal Approach for Size Control of MIIFe₂IIIO₄ (MII ═ MnII, FeII) Colloidal Nanoparticles

The versatility of a promising and repeatable oleate-based solvothermal approach has been explored through the synthesis of MnFe2O4 and gamma-Fe2O3/Fe3O4 nanoparticles in form of colloidal dispersions and the tuning of the particle and crystallite sizes. Spinel ferrite nanoparticles with controlled-size in the range 7-14 nm with dispersity below 15% was reached for both MnFe2O4 and gamma-Fe2O3/Fe3O4. The size-tuning was obtained with three different pathways: (i) direct approach by changing the solvent polarity or the precursor concentration; (ii) post-synthesis solvothermal treatment in the presence of metal oleates; (iii) post-synthesis solvothermal treatment in the absence of metal oleates.