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Large-Scale Synthesis of Colloidal Fe3O4 Nanoparticles Exhibiting High Heating Efficiency in Magnetic Hyperthermia
journal contribution
posted on 2015-12-17, 01:50 authored by Yury V. Kolen’ko, Manuel Bañobre-López, Carlos Rodríguez-Abreu, Enrique Carbó-Argibay, Alexandra Sailsman, Yolanda Piñeiro-Redondo, M. Fátima Cerqueira, Dmitri Y. Petrovykh, Kirill Kovnir, Oleg
I. Lebedev, José RivasExceptional
magnetic properties of magnetite, Fe3O4, nanoparticles
make them one of the most intensively studied inorganic nanomaterials
for biomedical applications. We report successful gram-scale syntheses,
via hydrothermal route or controlled coprecipitation in an automated
reactor, of colloidal Fe3O4 nanoparticles with
sizes of 12.9 ± 5.9, 17.9 ± 4.4, and 19.8 ± 3.2 nm.
To investigate structure–property relationships as a function
of the synthetic procedure, we used multiple techniques to characterize
the structure, phase composition, and magnetic behavior of these nanoparticles.
For the iron oxide cores of these nanoparticles, powder X-ray diffraction
and electron microscopy both confirm single-phase Fe3O4 composition. In addition to the core composition, the magnetic
performance of nanoparticles in the 13–20 nm size range can
be strongly influenced by the surface properties, which we analyzed
by three complementary techniques. Raman scattering and X-ray photoelectron
spectroscopy (XPS) measurements indicate overoxidation of nanoparticle
surfaces, while transmission electron microscopy (TEM) shows no distinct
core–shell structure. Considered together, Raman, XPS, and
TEM observations suggest that our nanoparticles have a gradually varying
nonstoichiometric Fe3O4+δ composition,
which could be attributed to the formation of Fe3O4–γ-Fe2O3 solid solutions
at their outermost surface. Detailed analyses by TEM reveal that the
hydrothermally produced samples include single-domain nanocrystals
coexisting with defective twinned and dimer nanoparticles, which form
as a result of oriented-attachment crystal growth. All our nanoparticles
exhibit superparamagnetic-like behavior with a characteristic blocking
temperature above room temperature. We attribute the estimated saturation
magnetization values up to 84.01 ± 0.25 emu/g at 300 K to the
relatively large size of the nanoparticles (13–20 nm) coupled
with the syntheses under elevated temperature; alternative explanations,
such as surface-mediated effects, are not supported by our spectroscopy
or microscopy measurements. For these colloids, the heating efficiency
in magnetic hyperthermia correlates with their saturation magnetization,
making them appealing for therapeutic and other biomedical applications
that rely on high-performance nanoparticle-mediated hyperthermia.
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Keywords
saturation magnetizationXPSelectron microscopynonstoichiometric Fe 3O compositionFe 3O nanoparticlesalternative explanationsoutermost surfaceColloidal Fe 3O Nanoparticles Exhibiting High Heating Efficiencysaturation magnetization valuesTEM observationsiron oxide coresheating efficiencyFe 3O300 Khydrothermal routephase compositionmicroscopy measurementssurface propertieshyperthermia correlatestransmission electron microscopynanoparticle surfacescore compositionMagnetic HyperthermiaExceptionalnanocrystals coexistingdimer nanoparticlesroom temperature