The effect of oleic acid on the synthesis of Fe_3−xO₄ nanoparticles over a wide size range

Abstract

This work reports on the effect of the oleic acid concentration on the magnetic and structural properties of Fe3-xO4 nanoparticles synthesized by thermal decomposition of Fe(acac)3 in benzyl-ether. This method allows the synthesis of highly monodisperse particles ranging from 7 to 100 nm in size by only varying the concentration of oleic acid in the reaction mixture. The structural and magnetic characterization reveal homogeneous particles in composition, with narrow particle size distribution, which are single-phase magnetite with almost bulk-like values of the saturation magnetization of about 90-99 emu g(-1) at low temperatures and show the characteristic anomaly in the zero field-cooling magnetization curves associated with the Verwey transition for nanoparticles bigger than about 7 nm. In addition, the analyses of aliquots of the reaction mixtures by Fourier transform infrared spectroscopy at various stages shed light on the nucleation and growth processes of the particles.

Effect of precursor concentration on size evolution of iron oxide nanoparticles

“…The graphs show three weight loss plateaus. 46,47 The first plateau below 200°C is attributed to the evaporation of adsorbed water and/or solvent molecules from the powder. The second and the third plateaus between 200-400°C and 500-750°C correspond to desorption from the surface and the decomposition of the surfactant molecules, respectively.…”

A one-pot method for building colloidal nanoparticles into bulk dry powders with nanoscale magnetic, plasmonic and catalytic functionalities

“…The solution was allowed to react for 30 min before being cooled down to room temperature. Oleic acid capped magnetic particles were prepared by the thermal decomposition method described in literature and dispersed in 10 mL of DCM [38]. Pt colloid was prepared following literature methods [39].…”

Probing the variability in oxidation states of magnetite nanoparticles by single-particle spectroscopy

“…30 In these highly crystalline samples, above the Verwey temperature, well defined magneto-crystalline axes are expected to favor spins pointing along the [111] directions, 21,35 as shown in (Table 1) were in agreement with those published elsewhere for NP of similar sizes. 12,20 Hysteresis loops were also recorded at 5 K after cooling the sample under 10 kOe (FC) from room temperature (Fig. S5, ESI †) in order to elucidate the existence of any changes in the internal magnetic configuration of the particles due to the presence of distinct coexisting magnetic phases.…”

“…Two samples of nominal Fe 3 O 4 NP with mean diameters of 15 and 24 nm, -in the following referred as S1 and S2, respectivelywere synthesized by slightly modifying a previously reported procedure 20 by using iron(III) acetylacetonate (Sigma-Aldrich, 99%)…”

“…13 However, even for highly monodisperse particles, a strong correlation has been found between their macroscopic magnetic behavior and the structural and compositional features of the individual NP. [20][21][22] This calls for the use of single-particle characterization techniques with elemental selectivity and high sensitivity to magnetic and electronic properties. [23][24][25][26] For example, a 3D visualization of the iron oxidation state in FeO/Fe 3 O 4 core-shell nanocubes has recently been achieved using electron energy loss tomography.…”