title: High-Performance Ferrite Nanoparticles through Nonaqueous Redox Phase Tuning.
abstract: From magnetic resonance imaging to cancer hyperthermia and wireless control of cell signaling, ferrite nanoparticles produced by thermal decomposition methods are ubiquitous across biomedical applications. While well-established synthetic protocols allow for precise control over the size and shape of the magnetic nanoparticles, structural defects within seemingly single-crystalline materials contribute to variability in the reported magnetic properties. We found that stabilization of metastable wüstite in commonly used hydrocarbon solvents contributed to significant cation disorder, leading to nanoparticles with poor hyperthermic efficiencies and transverse relaxivities. By introducing aromatic ethers that undergo radical decomposition upon thermolysis, the electrochemical potential of the solvent environment was tuned to favor the ferrimagnetic phase. Structural and magnetic characterization identified hallmark features of nearly defect-free ferrite nanoparticles that could not be demonstrated through postsynthesis oxidation with nearly 500% increase in the specific loss powers and transverse relaxivity times compared to similarly sized nanoparticles containing defects. The improved crystallinity of the nanoparticles enabled rapid wireless control of intracellular calcium. Our work demonstrates that redox tuning during solvent thermolysis can generate potent theranostic agents through selective phase control in ferrites and can be extended to other transition metal oxides relevant to memory and electrochemical storage devices.
authors.affiliation: Department of Materials Science and Engineering, ‡Research Laboratory of Electronics, §Department of Chemical Engineering, ∥Department of Biological Engineering, ⊥Department of Brain and Cognitive Sciences, and #Department of Nuclear Science & Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Ritchie
authors.initials: R
authors.lastname: Chen
authors.affiliation: Department of Materials Science and Engineering, ‡Research Laboratory of Electronics, §Department of Chemical Engineering, ∥Department of Biological Engineering, ⊥Department of Brain and Cognitive Sciences, and #Department of Nuclear Science & Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Christiansen
authors.affiliation: Department of Materials Science and Engineering, ‡Research Laboratory of Electronics, §Department of Chemical Engineering, ∥Department of Biological Engineering, ⊥Department of Brain and Cognitive Sciences, and #Department of Nuclear Science & Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Sourakov
authors.affiliation: Department of Materials Science and Engineering, ‡Research Laboratory of Electronics, §Department of Chemical Engineering, ∥Department of Biological Engineering, ⊥Department of Brain and Cognitive Sciences, and #Department of Nuclear Science & Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Alan
authors.initials: A
authors.lastname: Mohr
authors.affiliation: Department of Materials Science and Engineering, ‡Research Laboratory of Electronics, §Department of Chemical Engineering, ∥Department of Biological Engineering, ⊥Department of Brain and Cognitive Sciences, and #Department of Nuclear Science & Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Matsumoto
authors.affiliation: Department of Materials Science and Engineering, ‡Research Laboratory of Electronics, §Department of Chemical Engineering, ∥Department of Biological Engineering, ⊥Department of Brain and Cognitive Sciences, and #Department of Nuclear Science & Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Okada
authors.affiliation: Department of Materials Science and Engineering, ‡Research Laboratory of Electronics, §Department of Chemical Engineering, ∥Department of Biological Engineering, ⊥Department of Brain and Cognitive Sciences, and #Department of Nuclear Science & Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Alan
authors.initials: A
authors.lastname: Jasanoff
authors.affiliation: Department of Materials Science and Engineering, ‡Research Laboratory of Electronics, §Department of Chemical Engineering, ∥Department of Biological Engineering, ⊥Department of Brain and Cognitive Sciences, and #Department of Nuclear Science & Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Polina
authors.initials: P
authors.lastname: Anikeeva
keywords: Iron oxide; ferrites; hyperthermia; magnetic nanoparticles; magnetic resonance imaging; superparamagnetic