Abstract
Magnetically hard–soft core-shell ferrite nanoparticles are synthesized using an organometallic decomposition method through seed-mediated growth. Two sets of core-shell nanoparticles (S1 and S2) with different shell (Fe3O4) thicknesses and similar core (CoFe2O4) sizes are obtained by varying the initial quantities of seed nanoparticles of size 6.0 ± 1.0 nm. The nanoparticles synthesized have average sizes of 9.5 ± 1.1 (S1) and 12.2 ± 1.7 (S2) nm with corresponding shell thicknesses of 3.5 and 6.1 nm. Magnetic properties are investigated under field-cooled and zero-field-cooled conditions at several temperatures and field cooling values. Magnetic heating efficiency for magnetic hyperthermia applications is investigated by measuring the specific absorption rate (SAR) in alternating magnetic fields at several field strengths and frequencies. The exchange bias is found to have a nonmonotonic and oscillatory relationship with temperature at all fields. SAR values of both core-shell samples are found to be considerably larger than that of the single-phase bare core particles. The effective anisotropy and SAR values are found to be larger in S2 than those in S1. However, the saturation magnetization displays the opposite behavior. These results are attributed to the occurrence of spin-glass regions at the core-shell interface of different amounts in the two samples. The novel outcome is that the interfacial exchange anisotropy of core-shell nanoparticles can be tailored to produce large effective magnetic anisotropy and thus large SAR values.
Highlights
Tuning the magnetic properties of nanoparticles for enhanced biomedical applications such as magnetic resonance imaging (MRI) contrast agents, magnetic particle imaging, drug delivery, biosensing, magnetic marker-based bioassay, and magnetic hyperthermia has been studied intensively [1,2,3]
The XRD profile of the CoFe2 O4 nanoparticles is shown in Figure 1a; the average particle size obtained from the highest intensity peak (311) was 6.9 nm
XRD and SAED patterns indicate that the nanoparticles synthesized contained only the ferrite phase, and the lattice parameters are in agreement with the reported values of CoFe2 O4 nanoparticles [30,31]
Summary
Tuning the magnetic properties of nanoparticles for enhanced biomedical applications such as magnetic resonance imaging (MRI) contrast agents, magnetic particle imaging, drug delivery, biosensing, magnetic marker-based bioassay, and magnetic hyperthermia has been studied intensively [1,2,3]. Parameters of the nanoparticles such as the size, shape, composition, and interface in core-shell nanoparticles were employed to enhance the efficiency in both diagnosis and treatment of cancer [4,5]. Manipulating the magnetic properties through the interface coupling of different magnetic phases provides a new variable for rational material design and controlling the properties for fundamental science and technological applications [6,7]. The usual strategies used to tune the magnetic properties of nanoparticles are varying the size, shape, and composition, whereas having bi-magnetic phases in the nanoparticles provides the combined effect of multiphase properties [8,9]. The ability to combine novel properties of different materials and to fabricate nanostructures with improved efficiency increased interest in core-shell architecture [10].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
