The Synthesis of Maghemite Nanoparticles by Thermal Decomposition of Cryochemically Modified Iron(III) Acetylacetonate
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Synthesis of Maghemite Nanoparticles by Thermal Decomposition of Cryochemically Modified Iron(III) Acetylacetonate O. I. Vernayaa, *, A. S. Shumilkina, V. P. Shabatina, T. I. Shabatinaa, and M. Ya. Melnikova a
Department of Chemistry, Moscow State University, Moscow, 119991 Russia *e-mail: [email protected] Received January 10, 2020; revised January 12, 2020; accepted March 20, 2020
Abstract—Maghemite nanoparticles of 40 to 150 nm are obtained by the thermal decomposition of preliminarily cryochemically modified iron acetylacetonate. The composition and structure of the obtained particles and cryomodified precursor salt are determined by the X-ray diffraction (XRD) analysis, thermoanalytical methods (thermogravimetry, differential scanning calorimetry), infrared spectroscopy, and transmission electron microscopy. Keywords: nanoparticles, iron oxide, maghemite, iron acetylacetonate, cryochemical modification, thermal decomposition DOI: 10.3103/S0027131420050089
Like other nanomaterials, magnetite and maghemite (the oxidized form of magnetite) nanoparticles have a large specific surface and a high fraction of surface atoms with uncompensated bonds. In addition, they possess superparamagnetic properties that manifest themselves at the particle size below the threshold value (~128 nm). In this case, the particles are transformed to the superparamagnetic single-domain state and become evenly magnetized throughout the volume. In the case of the absence of an external magnetic field, the average magnetization of superparamagnetic particles is zero but they behave as paramagnetics in the external magnetic field. The unique properties of magnetic iron oxides make it possible to find an application for them in various sectors. They are used in the data recording and storage systems, analytical chemistry, and for water treatment. Chemical and biological sensors are being developed based on them [1–3]. The methods of magnetic solid-phase extraction and concentration, as well as the method of magnetic separation which is used for the separation of cells, proteins, enzymes, and DNA, are based on the use of superparamagnetic particles [3, 4]. Magnetite nanoparticles have a huge potential in medicine; thus, agents for magnetic resonance imaging (MRI) and magnetic hyperthermia are being developed based on them, they may serve as the magnetic vectors in the targeted drug delivery systems, and they are also used in tissue engineering [3, 5–8]. In addition, magnetite and maghemite nanoparticles can serve as the catalysts
for a series of processes such as Friedel–Crafts alkylation [9–10] and Fischer–Tropsch synthesis [11]. Superparamagnetic nanoparticles of iron oxides are obtained by coprecipitation of tri- and bivalent iron salts at a molar ratio of 2 : 1 by a solution of ammonia or an alkali. To control the size and shape of the particles being obtained, this process is carried out at a high pressure and temperature (by hydrothermal and solvothermal methods) in reverse micelles or by the polyol method when polyatomic alcohols a
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