title: Characterizing Physical Properties of Superparamagnetic Nanoparticles in Liquid Phase Using Brownian Relaxation.
abstract: Superparamagnetic iron oxide nanoparticles (SPIONs) have been extensively used as bioimaging contrast agents, heating sources for tumor therapy, and carriers for controlled drug delivery and release to target organs and tissues. These applications require elaborate tuning of the physical and magnetic properties of the SPIONs. The authors present here a search-coil-based method to characterize these properties. The nonlinear magnetic response of SPIONs to alternating current magnetic fields induces harmonic signals that contain information of these nanoparticles. By analyzing the phase lag and harmonic ratios in the SPIONs, the authors can predict the saturation magnetization, the average hydrodynamic size, the dominating relaxation processes of SPIONs, and the distinction between single- and multicore particles. The numerical simulations reveal that the harmonic ratios are inversely proportional to saturation magnetizations and core diameters of SPIONs, and that the phase lag is dependent on the hydrodynamic volumes of SPIONs, which corroborate the experimental results. Herein, the authors stress the feasibility of using search coils as a method to characterize physical and magnetic properties of SPIONs, which may be applied as building blocks in nanoparticle characterization devices.
authors.affiliation: The Center for Micromagnetics and Information Technologies (MINT), Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, 55455, USA.
authors.forename: Kai
authors.identifier: 0000-0002-9444-6112
authors.initials: K
authors.lastname: Wu
authors.affiliation: Department of Chemical Engineering and Material Science, University of Minnesota, Minneapolis, MN, 55455, USA.
authors.forename: Karl
authors.initials: K
authors.lastname: Schliep
authors.affiliation: School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, 55455, USA.
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Zhang
authors.affiliation: The Center for Micromagnetics and Information Technologies (MINT), Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, 55455, USA.
authors.forename: Jinming
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Optical Science and Engineering, Fudan University, Shanghai, 200433, P. R. China.
authors.forename: Bin
authors.initials: B
authors.lastname: Ma
authors.affiliation: The Center for Micromagnetics and Information Technologies (MINT), Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, 55455, USA.
authors.forename: Jian-Ping
authors.initials: JP
authors.lastname: Wang
keywords: harmonic ratio; phase lag; saturation magnetization; superparamagnetic iron oxide nanoparticles