Synthesis of Magnetic Nanocrystals by Thermal Decomposition in Glycol Media: Effect of Process Variables and Mechanistic Study

Abstract

The nucleation and growth of water dispersible iron-oxide nanoparticles synthesized by high temperature decomposition of iron(III) acetylacetonate in the presence of different solvents has been studied. A battery of techniques was used to characterize the products obtained under different conditions and to elucidate the synthesis mechanism. Results show that the synthesis of iron-oxide nanoparticles in triethylene glycol (TEG) proceeds through a multistep process whose first stage is likely to be the formation of an intermediate TEG-iron-complex that evolves into a low-crystallinity iron-oxide-organic precursor during aging at 180 °C. Raising the temperature above 240 °C caused the thermal decomposition of the precursor and the sudden nucleation of small iron-oxide nanocrystals. Keeping the reactant mixture at 280 °C led to the growth of iron-oxide nanocrystals, as did increasing the time at reflux temperature, the amount of initial iron precursor or the use high boiling point solvents. The particle size could be reproducibly controlled between 1.5 and 13 nm, with a relatively narrow size distribution. Larger particles could also be obtained using a solvothermal method in an autoclave reactor.

Influence of synthesis experimental parameters on the formation of magnetite nanoparticles prepared by polyol method

“…The higher concentration of metal precursor, independently from its nature, increases the size of the particle. This effect was reported in the literature on the synthesis of magnetite nanoparticles by thermal decomposition method [25,35].…”

“…MiguelSancho et al [24] discussed the stability of nanoparticles in relation with agglomeration process by using either dimercaptosuccinicacid (DMSA) or chemical modification of TEG coating. In a more recent paper, Miguel-Sancho et al [25] showed the influence of some experimental parameters on particle size, as initial precursor concentration, decomposition time and heating rate. A particle formation mechanism of iron oxide nanoparticles was proposed, which could be controlled by the total Fe(acac) 3 concentration and the type of solvent used, although crystallization conditions and magnetic properties were not discussed.…”

Effect of precursor concentration on size evolution of iron oxide nanoparticles

“…By changing the precursor concentration, the ratio between the surfactant and the precursor also varies. Several studies have shown that an increase in concentration may lead to both an increase 25,27,34,35 and a decrease 26,36 of the particle size. A conclusive explanation is still lacking.…”

“…We show that the ratio of the surfactant to the precursor plays a crucial role in tuning the size by changing the concentration, and we explain the observed opposite increasing/decreasing trend reported in the literature. [25][26][27]34,35 Iron oxide nanoparticles are superparamagnetic whose magnetic properties depend on their size. Magnetic measurements show that the nanoparticles possess room-temperature magnetizations close to the theoretically predicted values.…”

Pumping Metallic Nanoparticles with Spatial Precision within Magnetic Mesoporous Platforms: 3D Characterization and Catalytic Application

“…superparamagnetic iron oxide nanoparticles (SPIONs) were synthesized by a polyol-mediated method according to the synthesis procedure described elsewhere. [26][27] DMSA-FexOy nanoparticles were obtained via a ligand-exchange reaction process described in a previous work of our laboratory 28 The synthesis conditions were tailored to obtain SPION nanoparticles larger than the silica pores. Briefly, a DMSA aqueous solution (30 mg mL -1 ) was strongly mixed with a TEGcoated-SPIONs aqueous solution at room temperature.…”