Phase transfer studies of iron oxide nanoparticles: characterization based insights for applications

This study systematically explores the synthesis and functionalization of iron oxide nanoparticles (IONPs) synthesized via thermal decomposition methods using three common precursors: iron(iii) oleate (FeOl), iron pentacarbonyl [Fe(CO)₅], and iron acetylacetonate [Fe(acac)₃]. Comprehensive characterization was employed to evaluate the morphology, crystal structure, and magnetic properties of the synthesized IONPs, alongside four phase transfer strategies. Among the investigated methods, Fe(acac)₃-based synthesis predominantly yielded Fe₃O₄ nanoparticles with superior crystallinity and magnetic properties (112 A m² per kg of Fe). However, the synthesis was limited by solvent instability during thermal decomposition. FeOl-based synthesis offered better control over particle size and morphology but resulted in mixed-phase nanoparticles (Fe₃O₄ and γ-Fe₂O₃) with suboptimal magnetization. In contrast, Fe(CO)₅ produced nanoparticles with significantly reduced magnetic performance. While none of the four evaluated phase transfer methods (oxidative cleavage, base bath, ligand exchange using sodium citrate, and tetramethylammonium hydroxide) significantly altered the magnetization of the IONPs, oxidative cleavage and base bath methods were preferred. Their operational simplicity, reproducibility, and suitability for processing larger batches (up to 200 mg IONPs) make them particularly attractive from a scalability perspective compared to ligand-exchange-based methods. Selected phase-transferred nanoparticles demonstrate potential applications as MRI contrast agents. By systematically comparing synthesis approaches and phase transfer techniques, this work identifies critical factors that influence IONP properties and provides valuable insights for designing nanoparticles optimized for biomedical applications.