Magnetic Vortex and Hyperthermia Suppression in Multigrain Iron Oxide Nanorings

Raja Das,Raja Das,Eneko Garaio,Zohreh Nemati,Chiran Witanachchi,Anh-Tuan Le,Irati Rodrigo,Javier Alonso,Javier Alonso,Manh-Huong Phan,Hariharan Srikanth,Vu Dinh Lam,José Ángel García,Eneko Garaio,Vijaysankar Kalappattil

doi:10.3390/app10030787

Abstract

Single-crystal iron oxide nanorings have been proposed as a promising candidate for magnetic hyperthermia application because of their unique shape-induced vortex-domain structure, which supports good colloidal stability and enhanced magnetic properties. However, the synthesis of single crystalline iron oxide has proven to be challenging. In this article, we showed that chemically synthesized multigrain magnetite nanorings disfavor a shape-induced magnetic vortex-domain structure. Our results indicate that the multigrain Fe3O4 nanorings with an average outer diameter of ~110 nm and an inner to outer diameter ratio of ~0.5 do not show a shape-induced vortex-domain structure, which was observed in the single-crystal Fe3O4 nanorings of similar dimensions. At 300 Ks, multigrain magnetite nanorings showed an effective anisotropy field of 440 Oe, which can be attributed to its high surface area and intraparticle interaction. Both calorimetric and AC loop measurements showed a moderate inductive heating efficiency of multigrain magnetite nanorings of ~300 W/g at 800 Oe. Our results shed light on the magnetic ground states of chemically synthesized multigrain Fe3O4 nanorings.

Highlights

Spinel ferrite nanoparticles, MFe2 O4 (M = 3 − d transition metal) have attracted considerable attention in the past few decades due to their potential biomedical applications, for example in targeted drug delivery, diagnostics, and magnetic separation [1,2,3,4,5,6,7,8,9,10,11,12,13]
The of the the nanorings nanorings were were examined by X-ray diffractometer (XRD)
The annealed sample obtained after 5 h of hydrothermal reaction size (Figure 2a,b) yielded nanorings with an average outer diameter of ~110 nm and an inner to outer and an inner canimage be seen from the the in the inset, the diameter ratioto ofouter

Summary

Introduction

Large surface to volume ratio, size- and shape-tunable magnetic properties, and high biocompatibility make iron oxide nanoparticles appropriate nanocarriers for magnetic resonance imaging, magnetic hyperthermia, and targeted drug delivery [22,23,24,25,26,27,28,29,30]. The SAR value of the nanoparticles highly depends on the colloidal stability or inter-particle interaction of the nanoparticles To overcome these limits, different strategies have been proposed, such as tuning the shape and size of these nanoparticles. Different strategies have been proposed, such as tuning the shape and size of these nanoparticles In this regard, single-crystalline iron oxide nanorods [27] and nanotubes [28] have recently been synthesized, which have shown excellent magnetic hyperthermia properties. Our study pinpoints that it is the formation of the multigrain structure that disfavors the formation of a magnetic vortex and causes the reduction of the heating efficiency in magnetite nanorings

Synthesis of Fe3 O4 Nanorings

Characterization

Results

O4 nanorings after 12 h of hydrothermal images of the reduced

Representative

Conclusions