In this paper, water colloidal solutions of nanoparticles of magnetite (magnetic nanofluids, (MNFs)) are investigated by synchrotron X-ray diffraction (XRD) and small-angle scattering (SAXS). To prevent aggregation, nanoparticles are coated with polyacrylic acid (PAA) in a single solution and citric (CA) in the other solutions. In both cases, the maxima of the particle size distribution from SAXS (9–10 nm) correspond to the sizes of the magnetite crystallites that were estimated from the broadening of the diffraction lines. In addition, the SAXS data indicate the presence of a significant proportion of aggregates (up to 60 nm in diameter) in both colloidal solutions, although fundamental differences in the structures of aggregates between the MNFs stabilized by PAA and CA were not observed. In this study determination of the structural characteristics of MNFs were carried out in order to obtain stable dispersive non-aggregating nanoparticles of magnetite for use as contrast agents in magnetic resonance tomography, drug carriers, and other biomedical applications.
61.20.-p Structure of liquids
61.46.Df Structure of nanocrystals and nanoparticles
$^1$Faculty of Physics, Moscow State University, Moscow, 119991, Russia
$^2$Frank Laboratory of Neutron Physics, JINR, Dubna, 141980, Russia
$^3$National Research Center “Kurchatov Institute”, Moscow, 123182, Russia
$^4$Semmelweis University, Budapest, Hungary, H-1089
$^5$Szeged University, Szeged, Hungary, H-6720
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