HYDROPHILIC VERSUS HYDROPHOBIC OLEATE COATED MAGNETIC PARTICLES E. PUSCASU 1 , L. SACARESCU 2 , A. DOMOCOS 1 , C. LEOSTEAN 3 , R. TURCU 3 , D. CREANGA 1 , M. BALASOIU 4,5 1 “Alexandru Ioan Cuza” University, Physics Faculty, Iasi, Romania 2 “Petru Poni” Institute of Macromolecular Chemistry, Iasi, Romania 3 National Institute of Research and Development of Isotopic and Molecular Technology, Cluj, Romania 4 Institute of Nuclear Research, Dubna, Russian Federation 5 “Horia Hulubei Institute of Physics and Nuclear Engineering, Bucharest, Romania Corresponding author: dorina.creanga@gmail.com Received August 31, 2015 Oleic acid was used to develop hydrophobic coating shell for magnetic nanoparticles (MNPs) stabilization in hydrophobic medium; sodium oleate was used to yield hydrophilic coating of MNPs in colloidal aqueous suspension. Microstructural and magnetic properties were investigated by standard methods. The interpretation of the observed microstructural and magnetic features was based on the differences in coating shell arrangement, i.e. single oleate layer in hydrophobic colloidal MNPs compared to double oleate layer in hydrophilic MNP sample. In this latter case coated particle interaction seems to be favored resulting in some clusters with character of mass fractals (2.4 fractal dimension) as shown from SAXS data analysis. Key words: iron oxides, oleate ions, magnetic colloids. PACS: 75.50. Mm, 75.75.Cd, 81.07-b 1. INTRODUCTION Previous literature reports on magnetic nanoparticle yielding in the form of uniform and stable suspensions in various liquids, by applying versatile co- precipitation method, suggested that oleate ion is able to develop one of the strongest interactions with iron ions at the surface of iron oxide nanoparticles under controlled conditions of temperature, concentration, pH, stirring duration and washing steps of intermediate ferrophase and/or of magnetic colloid. Rom. Journ. Phys., Vol. 61, Nos. 5–6, P. 946–956, Bucharest, 2016