Studies of magnetite nanoparticles synthesized by thermal decomposition of iron (III) acetylacetonate in tri(ethylene glycol)
Introduction
Superparamagnetic (SPM) iron oxide (particularly Fe2O3 and Fe3O4) nanoparticles have been attracted a great attention in the bio-medical field such as magnetic separation, drug delivery, cancer hyperthermia and magnetic resonance imaging (MRI) contrast enhancement [1], [2], [3], [4], [5], [6]. The single-step synthesis of highly water-soluble, superparamagnetic and biocompatible magnetite nanoparticles with controlled size and distribution is extremely important to realize the full potential of these materials in biomedicine. To date, the thermal decomposition method is very promising technique to fabricate high-quality superparamagnetic and monodisperse magnetite nanoparticles [7], [8], [9]. Typically, this method involves decomposition of Fe(acac)3 in a high-boiling temperature solvent in presence of stabilizing surfactants such as oleic acid and oleylamine. However, the obtained magnetite nanoparticles are organic soluble which makes them inappropriate for bio-medical applications. Therefore, many groups have further developed the thermal decomposition method to directly synthesize water-soluble magnetic nanoparticles [10], [11]. Recently, Cai et al. [12] have synthesized water-soluble magnetite nanoparticles by high-temperature decomposition of Fe(acac)3 in triethylene glycol (TREG). An obvious advantage of this approach is that no further reducing agent and surfactants are required, which made this process easy to scale-up for mass. The TREG has been used for a triple role as high-boiling solvent, reducing agent and stabilizer to efficiently control the particle growth and prevent interparticle aggregation. Here, we have extended this work and proposed a mechanism for solubility of the as-prepared magnetite nanoparticles in aqueous suspension by exploring surface charge and surface coating of the nanoparticles. Cytotoxicity and hyperthermia studies of the nanoparticles have also been performed to evaluate their potentiality in biomedicine.
Section snippets
Experimental section
Absolute ethanol and ethyl acetate were used without purification. Tri(ethylene glycol) (TREG, 99%) and Iron(III) acetylacetonate (Fe(acac)3, 97%) were purchased from Sigma-Aldrich.
Water-soluble Fe3O4 nanoparticles were prepared by the thermal decomposition of Fe(acac)3 in TREG at elevated temperature with out using any surfactants [12]. Typically, 2 mmol of Fe(acac)3 was dissolved in a 20 ml of hydrophilic TREG media and then magnetically stirred under a flow of argon. The solution was
Crystal structure
Fig. 1 shows the XRD patterns which match well with the standard XRD patterns for bulk magnetite (JCPDS File no. 19-0629) indicating that the particles are consisting of Fe3O4 phase. The average crystallite size is measured using Scherrer's equation [15] as 10.7 nm.
Size and morphology
The TEM image in Fig. 2 indicates that the magnetite nanoparticles are well dispersed in water. The average size of the particle is about 11 nm which is very close to the crystallite size obtained from XRD. Inset of Fig. 7 is showing
Conclusions
As-prepared magnetite nanoparticles are relatively monodisperse, single crystalline and superparamagnetic in nature. The nanoparticles are highly soluble in water because of the steric and electrostatic interactions between the particles arise from the surface adsorbed tri(ethyleneglycol) molecules and the associated positive charges, respectively. Cytotoxicity studies show that as-prepared magnetite nanoparticles are biocompatible up to the iron concentration of 80 μg/ml. The significant
Acknowledgments
The authors gratefully acknowledge the help of Dr. S.D. Dhole, Department of Physics, University of Pune, for the hyperthermia heating measurement.
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