Abstract
Greigite (Fe3S4) particles, with strong ferrimagnetic behavior, have been found to have desirable uses in the areas of biomedical and environmental applications. Size-dependent magnetic properties of greigite can play a crucial role in efficiency of its applications. This study reviews two synthetic approaches to producing such particles. The methods tested within this study include a coprecipitation synthesis and a hydrothermal process. While the coprecipitation method proved to be ineffective at producing greigite, the hydrothermal process showed promise after consistently producing greigite. For the hydrothermal process, the effects of synthesis time, autoclave atmosphere, and polyvinylpyrrolidone (PVP) addition as a capping agent to control particle growth were investigated using X-ray diffractometry (XRD) with Rietveld refinement, vibrating sample magnetometry (VSM), and scanning electron microscopy (SEM). The results show that, while pyrite (FeS2) forms as an impurity phase, increasing the synthesis time up to 18 hours increases the greigite fraction up to 70 wt% and saturation magnetization up to ∼ 35 emu/g for the powder synthesized in argon. The SEM micrographs of this sample reveal a mean greigite particle size of ∼ 700 nm. It was found that adding PVP brings about a much more uniform microstructure of agglomerated plate-shape particles with nano-sized features.
Highlights
Greigite (Fe3S4), first reported by Skinner et al.,[1] is an iron sulfide mineral, analogous to magnetite, with an inverse spinel crystal structure that generally occurs naturally due to the actions of sulfate-reducing bacteria
Greigite is a viable candidate for this hyperthermia cancer treatment due to its magnetic properties and ability to be synthesized as a nanoparticle.[7]
A coprecipitation synthesis and a hydrothermal process with and without PVP as a capping agent were tested within this study to determine their relative ability in producing greigite particles
Summary
Greigite (Fe3S4), first reported by Skinner et al.,[1] is an iron sulfide mineral, analogous to magnetite, with an inverse spinel crystal structure that generally occurs naturally due to the actions of sulfate-reducing bacteria. Greigite is a strong ferrimagnet, and pure greigite can have a saturation magnetization of 59 emu/g.2. As a nanoparticle, this iron sulfide has been shown to have properties favorable for various applications, including gas sensing,[3] battery anodes,[4,5,6] cancer hypothermia,[7] and radionuclide sorbants.[8] to our knowledge, greigite is not readily available commercially as nanoparticles. An effective method of synthesizing greigite nanoparticles with controlled properties is desirable. Greigite is a viable candidate for this hyperthermia cancer treatment due to its magnetic properties and ability to be synthesized as a nanoparticle.[7]
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