The surfactant templated aqueous synthesis of cubic iron oxide nanoparticles with controllable properties for magnetic energy dissipation.

Abstract

Cubic iron oxide nanoparticles (IONPs) are commonly synthesized via thermal decomposition in organic solvents, yielding well-defined particles but requiring complex phase-transfer steps that hinder scalability. In contrast, aqueous co-precipitation offers a simple, cost-effective, and environmentally friendly alternative, although it typically produces spherical nanoparticles with limited control over size and morphology. In this study, sodium dodecyl sulfate (SDS) was introduced as an additive during the aqueous co-precipitation of iron chlorides, enabling the direct synthesis of cubic IONPs. Particle size was precisely tuned from 15 to 38 nm by varying the reaction pH between 11.6 and 13.2, as confirmed by transmission electron microscopy. Electron diffraction revealed that the nanoparticles consisted predominantly of magnetite with minor hematite impurities, while Raman spectroscopy showed enhanced magnetite formation at higher pH values through increased intensity of the characteristic 668 cm^-1 peak. Magnetic hyperthermia measurements performed at 93 kHz and 7.9 kA m^-1 produced specific absorption rate (S_AR) values of 2.0-3.4 W g^-1 [Fe], with S_AR increasing with particle size. Notably, 38 nm cubic IONPs exhibited a 3.8-fold higher S_AR than comparable particles synthesized via organic-solvent routes, demonstrating a scalable aqueous strategy for producing high-performance cubic IONPs for biomedical applications.