Size dependant heating rates of superparamagnetic iron oxide nanoparticles for magnetic fluid hyperthermia
M. Gonzales-Weyhmiller, M. Zeisberger and K.M. Krishnan
University of Washington, US
superparamagnetic nanoparticles, relaxation, calorimetry, magnetic fluid hyperthermia, iron oxide, magnetite, polydispersity, heating rates, size-dependence
For magnetic fluid hyperthermia treatments with superparamagnetic nanoparticles it is desirable to maximize particle heating rates in order to minimize clinical dosages. For monodisperse samples it has been predicted that there would be an optimum particle size which would yield the highest heating rate for a given set of measurement conditions. At this optimum size, very high heating rates are achievable. However, all real ferrofluid samples are polydisperse to some degree, therefore polydispersity of size, shape, crystallinity, and surface coating needs to be taken into account for accurate modeling of the heating properties of the particles. We have synthesized iron oxide particles with extreme uniformity of size, crystallinity and shape with control of particle size up to ~ 20 nm by the thermal decomposition of organometallics. Subsequently, the nanoparticles have been transferred to the water phase. The monodispersity of these particles makes them good candidates for studying the role of size in determining the MFH heating behavior of nanoparticles. Calorimetric measurements as well as careful characterization of particle size and size distribution have been performed. We have demonstrated for a given frequency, heating rates of superparamagnetic particles are dependent on particle size, in agreement with earlier theoretical predictions.
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Nanotech 2007 Conference Program Abstract