ISSN 0012-5008, Doklady Chemistry, 2010, Vol. 433, Part 2, pp. 199–201. © Pleiades Publishing, Ltd., 2010. Original Russian Text © A.S. Shaporev, V.K. Ivanov, D.O. Gil’, A.S. Vanetsev, Yu.D. Tret’yakov, 2010, published in Doklady Akademii Nauk, 2010, Vol. 433, No. 6, pp. 770–772. 199 Transition of functional materials into nanodis- persed state can be accompanied by the change in their properties and the appearance of absolutely new prop- erties [1, 2]. Considerable attention of researchers is paid to the development of new synthesis procedures for inorganic nanomaterials [3]. In this work, we propose for the first time a new method for obtaining nanoparticles of transition metal oxides (Fe, Co, Mn) in the form of colloidal solutions, which is based on solvolysis of metal nitrates in high- boiling solvents [4]. Here, oleylamine (20 mL) was used as a high-boiling solvent; the concentration of iron, manganese, or cobalt nitrate in the reaction mix- tures was 0.05 mol/L. To vary the particle shape and size, oleic acid (0–2 mL) and diphenyl ether (0– 2 mL) were added. The synthesis was carried out in an inert atmosphere. The synthesis temperature and time varied in the ranges of 150–300°C and 1–6 h, respec- tively. Metal oxide nanoparticles obtained were iso- lated by the solvent substitution method [5] (acetone was used as a polar solvent) and redispersed in hep- tane. In case when large crystalline particles were syn- thesized, the particles were isolated by centrifugation and washed twice with acetone. The samples obtained were studied by physico- chemical methods. The micromorphology of the sam- ples was studied by transmission electron microscopy (TEM) using a Leo912 AB Omega electron micro- scope. The particle size was determined from several TEM images of different parts of a sample at the same magnification. The phase compositions of the samples were determined by electron diffraction. The interpla- nar distances corresponding to the diffraction maxima were calculated by the Bragg equation. IR spectra in the range of 650–4000 cm –1 were obtained by frustrated total internal reflection on a Perkin-Elmer Spectrum One spectrophotometer. Mössbauer spectra were recorded on an Ms-1104 EM (Russia) constant-acceleration spectrometer. A 57 Co(Rh) source was used. Isomer shifts were mea- sured using an α-Fe reference. According to the electron diffraction data, the phase compositions of all metal oxide nanoparticles synthesized did not depend on the synthesis condi- tions (temperature, duration, presence/absence of a surfactant). So, the product synthesized from cobalt(II) nitrate was found to be CoO, and the prod- uct obtained from manganese(II) nitrate was mainly Mn 2 O 3 with small impurities of other phases, whose exact compositions were not determined. At the same time, iron oxide samples synthesized from iron(III) nitrate consist of particles with a spinel structure and can be either γ-Fe 2 O 3 or Fe 3 O 4 . To determine the crys- tal structure of the iron oxide samples in more detail, we used Mössbauer spectroscopy. The measurements at room temperature have shown that the paramag- netic component present in the spectra of the samples is likely due to small clusters of iron(III) oxide γ-Fe 2 O 3 . The low-temperature measurements have revealed that the paramagnetic signal from iron(III) obtained at room temperature is not split into a set of lines of magnetic hyperfine structures with decreasing temperature to 77 K, which indicates that maghemite can be a superparamagnet at the temperatures higher than the blocking temperature [6, 7]. The superpara- magnetic behavior of γ-Fe 2 O 3 particles is explained by their size (1–10 nm from the TEM data), which is smaller than the superparamagnetic limit. To determine the composition of the ligand shells of nanoparticles of metal oxides, the samples were studied by IR spectroscopy. There were no fundamen- tal distinctions between the spectra of the samples syn- CHEMISTRY Solvothermal Synthesis of Colloidal Solutions of Transition Metal (Fe, Co, Mn) Oxides A. S. Shaporev a , V. K. Ivanov a , D. O. Gil’ b , A. S. Vanetsev a , and Academician Yu. D. Tret’yakov b Received April 29, 2010 DOI: 10.1134/S0012500810080033 a Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119991 Russia b Moscow State University, Moscow, 119992 Russia