Superparamagnetic CoFe 2 O 4 @Au with High Specific Absorption Rate and Intrinsic Loss Power for Magnetic Fluid Hyperthermia Applications Sandip Sabale 1,2 • Vidhya Jadhav 2 • Shubhangi Mane-Gavade 2 • Xiao-Ying Yu 1 Received: 15 May 2018 / Revised: 27 July 2018 / Published online: 10 October 2018 Ó The Chinese Society for Metals and Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract CoFe 2 O 4 nanoparticles (NPs) and surface modified with gold (Au) have been synthesized by a thermal decomposition method. The obtained NPs and formation of CoFe 2 O 4 @Au core–shell (CS) were confirmed by characterizing their structural and optical properties using X-ray powder diffraction (XRD) patterns, Fourier transform infrared spectroscopy, Raman spectroscopy, UV–Visible and photoluminescence studies. Morphological and compositional studies were carried out using high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy, while the magnetic properties were determined using alternating gradient magnetometer and Mossbauer to define the magneto-structural effects of shell formation on the core NPs. Induction heating properties of CoFe 2 O 4 and CoFe 2 O 4 @Au CS magnetic nanoparticles (MNPs) have been investigated and correlated with magneto-structural properties. Specific absorption rate and intrinsic loss power were calculated for these MNPs within the human tolerable range of frequency and amplitude, suggesting their potential in magnetic fluid hyperthermia therapy for possible cancer treatment. Keywords CoFe 2 O 4 @Au  Superparamagnetic  Specific absorption rate (SAR)  Intrinsic loss power (ILP)  Magnetic fluid hyperthermia 1 Introduction Magnetic nanoparticles (MNPs), especially superparam- agnetic iron oxide nanoparticles (SPIONs), have shown to have potential for use in biomedical applications such as in targeted drug delivery, imaging, magnetic fluid hyperther- mia (MFH) and biosensors [1–3]. The ability of SPIONs to convert the electromagnetic energy into heat is the main reason for SPION-based biomedical applications. This heat generation technique by SPION mediators plays an important role in cancer treatment with hyperthermia and multimodal imaging [4, 5]. Recently, MNP-based MFH proved more therapeutically efficient than the common chemotherapeutic drugs (i.e., doxorubicin and Feridex) [6]. Different types of SPIONs have been studied for their effectiveness as hyperthermia agents [3]. These SPIONs are either magnetite (Fe 3 O 4 ) or maghemite (c-Fe 2 O 3 ), stabilized by coating with a variety of ligands such as dextran, cationic liposomes, polyvinyl alcohol, lauric acid and oleic acid [3]. Another category of these SPIONs is the metal-doped ferrites, MFe 2 O 4 ,(M = Co 2? , Mn 2? , Ni 2? , Zn 2? , Mg 2 )[7–9]. Biomedical applications for such MNPs have been limited so far due to their instability under physiological conditions, harmful free radical formation and inappropriate surface binding of the ligand. In partic- ular, SPIONs are cytotoxic to different types of cells because of Fe-induced intracellular formation of reactive oxygen species as Fe seeps into the cellular milieu [3]. Cytotoxicity arises due to the absence of biocompatible or protective coating which prevents the seepage of Fe from SPIONS surfaces. Hence, coating with biocompatible Available online at http://link.springer.com/journal/40195 Electronic supplementary material The online version of this article (https://doi.org/10.1007/s40195-018-0830-5) contains supplementary material, which is available to authorized users. & Sandip Sabale srsabale@gmail.com & Xiao-Ying Yu xiaoying.yu@pnnl.gov 1 Earth and Biological Sciences Directorate, PNNL, Richland, WA 99352, USA 2 Department of Chemistry, Jaysingpur College Jaysingpur, Shivaji University, Kolhapur, MS 416101, India 123 Acta Metallurgica Sinica (English Letters) (2019) 32:719–725 https://doi.org/10.1007/s40195-018-0830-5