Optimization of microwave-solvothermal synthesis of Fe3O4 nanoparticles. Coating, modification, and characterization

Abstract

In this research, magnetite nanoparticles were synthetized by the microwave-solvothermal method. The parameters related to this method were evaluated with: 1) the Plackett-Burman design, in order to evaluate the influence of the holding time [th] and the gradient time [tg] (reaction times) in the synthesis percent yield; and 2) the Box-Behnken design (BBD), selected in order to reduce the number of experimental experiences. In this last, the ammonium acetate amount (mmol) [th], and the microwave system temperature were optimized in order to achieve the smallest magnetite nanoparticles. Microwave assisted coating and modification with TMSPT/AMT were performed to the synthetized nanoparticles, in order to avoid degradation. The response variable considered for optimization of the synthesis was the nanoparticle's size, which was estimated by X-ray diffraction. Temperature and th resulted to be the most important parameters affecting the nanoparticle's size. The BBD allowed to obtain nanoparticle sizes between 10 and 32 nm. Polynomial validation was performed with confirmatory experiments considering the following conditions: T = 255 °C, th = 10 min, tg=7 min, ammonium acetate amount = 4.55 mmol, Fe(III) = 2 mmol, sodium citrate amount = 1.55 mmol and ethylene glycol = 6 mL. The obtained nanoparticles, with a size of 14 nm, were characterized by FT-IR, X-RD, SEM, and STEM.