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High-Performance Ferrite Nanoparticles through Nonaqueous Redox Phase Tuning
journal contribution
posted on 2016-02-04, 16:45 authored by Ritchie Chen, Michael G. Christiansen, Alexandra Sourakov, Alan Mohr, Yuri Matsumoto, Satoshi Okada, Alan Jasanoff, Polina AnikeevaFrom 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.
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Nonaqueous Redox Phase TuningFromhyperthermic efficienciescation disordercancer hyperthermiaintracellular calciumtheranostic agentstransition metal oxidesferrite nanoparticleshallmark featureshydrocarbon solventsloss powerselectrochemical storage devicesdecomposition methodsphase controlrelaxivity timesferrimagnetic phasepostsynthesis oxidationresonance imaging
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