The XIX International Scientific Conference of Young Scientists and Specialists Dubna, Russia February 16-20, 2015 Sonja Jovanović, 1,2 Matjaž Spreitzer, 2 Danilo Suvorov 2 1 Laboratory of Physics, Vinča Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia 2 Advanced Materials Department, Jožef Stefan Institute, Ljubljana, Slovenia SYNTHESIS OF NON-AGGLOMERATED COBALT FERRITE NANOPARTICLES

high coercivity moderate saturation magnetization large magnetic anisotropy large magnetostrictive coefficient Cobalt ferrite – CFO Ferrimagnetic behavior d cr =100 nmd sp =10 nm Superparamagnetic behavior AIM  preparation of superparamagnetic non-agglomerated CFO nanoparticles  optics  ferrofluids  catalysis  biomedicine  sensors  recording madia Introduction

Water/1-pentanol (1:5) solution of NaOH and Co-precipitation Washing samples with n-hexane/ethanol Drying on air at RT Black powder T=180 o C, t=16h Black precipitate Solvothermal synthesis Aq. solution of Co(NO) 2 ∙6H 2 O and Fe(NO) 3 ∙9H 2 O Black precipitate mixing mixing 2h at RT Oleic acid Synthesis of CFO NPs Teflon-lined, stainless-steel autoclave

Scale bar is 10 nm Results – XRD and TEM

Results – TGA and FTIR Weight loss saturates at 25 % - formation of a complete monolayer 3400 cm -1 Stretching of hydroxide groups (moisture) 3007 cm -1 C-H stretching of =C-H group 2961 cm -1 Asymmetric stretching of –CH 3 group 2925 cm -1 and 2855 cm -1 Asymmetric and symmetric stretching of –CH 2 group 1642 cm -1 H-O-H scissoring 1547 cm -1 and 1421 cm -1 Asymmetric and symmetric stretching of –COOH group 1458 cm -1 –CH 2 scissoring 1356 cm -1 In-plane O-H banding 1311 cm -1 C-O stretching 734 cm -1 -CH 2 rocking vibration (at least four methylenes in the row) 590 cm -1 Stretching of metal ion at the tetrahedral A-site, M A ↔O bridging bidentate – covalently bonded -COO - groups to the surface metal atoms Δ = 126 cm -1

C OA = M - superparamagnetic behavior C OA = M - ferrimagnetic behavior Results – VSM

-gradual change of oleic acid concentration -Improved size and shape uniformity of CFO NPs -Preparation of hydrophobic, non-agglomerated NPs -Tuning of magnetic properties -Critical concentration M conclusions  S. Jovanović et al., J. Alloy Compd. 589 (2014)  S. Jovanović et al., J. Phys. Chem. C, 118 (2014) – More information:

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