Abstract
Iron oxide magnetic nanoparticles (IOMNPs) have been successfully synthesized by means of solvothermal reduction method employing polyethylene glycol (PEG200) as a solvent. The as-synthesized IOMNPs are poly-dispersed, highly crystalline, and exhibit a cubic shape. The size of IOMNPs is strongly dependent on the reaction time and the ration between the amount of magnetic precursor and PEG200 used in the synthesis method. At low magnetic precursor/PEG200 ratio, the cubic IOMNPs coexist with polyhedral IOMNPs. The structure and morphology of the IOMNPs were thoroughly investigated by using a wide range of techniques: TEM, XRD, XPS, FTIR, and RAMAN. XPS analysis showed that the IOMNPs comprise a crystalline magnetite core bearing on the outer surface functional groups from PEG200 and acetate. The presence of physisorbed PEG200 on the IOMNP surface is faintly detected through FT-IR spectroscopy. The surface of IOMNPs undergoes oxidation into maghemite as proven by RAMAN spectroscopy and the occurrence of satellite peaks in the Fe2p XP spectra. The magnetic studies performed on powder show that the blocking temperature (TB) of IOMNPs is around 300 K displaying a coercive field in between 160 and 170 Oe. Below the TB, the field-cooled (FC) curves turn concave and describe a plateau indicating that strong magnetic dipole-dipole interactions are manifested in between IOMNPs. The specific absorption rate (SAR) values increase with decreasing nanoparticle concentrations for the IOMNPs dispersed in water. The SAR dependence on the applied magnetic field, studied up to magnetic field amplitude of 60 kA/m, presents a sigmoid shape with saturation values up to 1700 W/g. By dispersing the IOMNPs in PEG600 (liquid) and PEG1000 (solid), it was found that the SAR values decrease by 50 or 75 %, indicating that the Brownian friction within the solvent was the main contributor to the heating power of IOMNPs.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-015-1091-0) contains supplementary material, which is available to authorized users.
Highlights
In the recent decades, extensive research has been focused on the synthesis of magnetic nanoparticles (MNPs) possessing new and attractive properties that could propel them as ideal candidates for multiple biomedical applications such as contrast agents for magnetic resonance imaging [2], targeted drug/gene/RNA delivery [3], heat generators for magnetic hyperthermia [4], and magnetic separation and purification of biomolecular species [5]
We extend the synthesis method developed by Deng et al [33], by replacing the ethylene glycol with polyethylene glycol 200 (PEG200) as solvent in a one-step synthesis method of water-soluble iron oxide magnetic nanoparticles (IOMNPs)
Sixty milliliters of PEG200 induce the formation of cubic Iron oxide magnetic nanoparticles (IOMNPs) and favor oxidative conditions which allow the formation of a small percent of hematite
Summary
Extensive research has been focused on the synthesis of magnetic nanoparticles (MNPs) possessing new and attractive properties (good chemical stability, low toxicity, high magnetic saturation, etc. [1]) that could propel them as ideal candidates for multiple biomedical applications such as contrast agents for magnetic resonance imaging [2], targeted drug/gene/RNA delivery [3], heat generators for magnetic hyperthermia [4], and magnetic separation and purification of biomolecular species [5]. By taking advantage of their heat-releasing capabilities as a result of their interaction with an external magnetic field, these MNPs have been recently used in several clinical trials for prostate and brain cancer treatment by means of magnetic hyperthermia [7, 8], a technique based on the higher heating sensitivity of cancer cells to heating as compared to healthy ones. It is well know that when exposed to an external alternating magnetic field, the amount of heat released in the medium strongly depends on MNP-specific absorption rate (SAR), called specific loss power (SLP) [9]. SAR (which is equal to the rate at which energy is adsorbed per nanoparticles unit mass at a specific frequency) has become one of the important parameter describing MNP heating efficiency capabilities. It is widely accepted that by carefully controlling and tuning these properties, a substantial increase of their hyperthermia performance can be achieved
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