Abstract
Magnetic iron oxides have been used in biomedical applications, such as contrast agents for magnetic resonance imaging, carriers for controlled drug delivery and immunoassays, or magnetic hyperthermia for the past 40 years. Our aim is to investigate the effect of pressure and temperature on the structural, thermal, and magnetic properties of iron oxides prepared by hydrothermal synthesis at temperatures of 100–200 °C and pressures of 20–1000 bar. It has been found that pressure influences the type of iron oxide crystalline phase. Thus, the results obtained by Mössbauer characterization are in excellent agreement with X-ray diffraction and optical microscopy characterization, showing that, for lower pressure values (<100 bar), hematite is formed, while, at pressures >100 bar, the major crystalline phase is goethite. In addition, thermal analysis results are consistent with particle size analysis by X-ray diffraction, confirming the crystallization of the synthesized iron oxides. One order of magnitude higher magnetization has been obtained for sample synthesized at 1000 bar. The same sample provides after annealing treatment, the highest amount of good quality magnetite leading to a magnetization at saturation of 30 emu/g and a coercive field of 1000 Oe at 10 K and 450 Oe at 300 K, convenient for various applications.
Highlights
Magnetic iron oxide particles have been used for in vitro diagnostics for the past 40 years
Due to the unique physical, chemical, thermal and mechanical properties of iron oxide nanoparticles, as well as their biocompatibility and low toxicity in the human body, they have been used in many biomedical applications [1,2,3,4,5,6], such as contrast agents [7] for magnetic resonance imaging (MRI), carriers for controlled drug delivery and immunoassays [8,9,10,11,12,13], and in magnetic hyperthermia [14,15,16,17,18,19,20,21,22,23]
Evidenced through the specific Verwey and Morin transitions evidenced by the ZFC-FC measurements on sample NV7-TT (Figure 10(c))
Summary
Magnetic iron oxide particles have been used for in vitro diagnostics for the past 40 years. Due to the unique physical, chemical, thermal and mechanical properties of iron oxide nanoparticles, as well as their biocompatibility and low toxicity in the human body, they have been used in many biomedical applications [1,2,3,4,5,6], such as contrast agents [7] for magnetic resonance imaging (MRI), carriers for controlled drug delivery and immunoassays [8,9,10,11,12,13], and in magnetic hyperthermia [14,15,16,17,18,19,20,21,22,23] All these applications require the particles to be superparamagnetic at room temperature. The stability of hematite (α-Fe2O3) of various morphologies has been studied
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