Microwave-Assisted Solvothermal Synthesis of Nanocrystallite-Derived Magnetite Spheres

Abstract

The synthesis of magnetic particles triggers the interest of many scientists due to their relevant properties and wide range of applications in the catalysis, nanomedicine, biosensing and magnetic separation fields. A fast synthesis of iron oxide magnetic particles using an eco-friendly and facile microwave-assisted solvothermal method is presented in this study. Submicron Fe3O4 spheres were prepared using FeCl3 as an iron source, ethylene glycol as a solvent and reductor and sodium acetate as a precipitating and nucleating agent. The influence of the presence of polyethylene glycol as an additional reductor and heat absorbent was also evaluated. We reduce the synthesis time to 1 min by increasing the reaction temperature using the microwave-assisted solvothermal synthesis method under pressure or by adding PEG at lower temperatures. The obtained magnetite spheres are 200–300 nm in size and are composed of 10–30 nm sized crystallites. The synthesized particles were investigated using the XRD, TGA, pulsed-field magnetometry, Raman and FTIR methods. It was determined that adding PEG results in spheres with mixed magnetite and maghemite compositions, and the synthesis time increases the size of the crystallites. The presented results provide insights into the microwave-assisted solvothermal synthesis method and ensure a fast route to obtaining spherical magnetic particles composed of different sized nanocrystallites.

Multiwavelength SERS of Magneto-Plasmonic Nanoparticles Obtained by Combined Laser Ablation and Solvothermal Methods

“…Figure A shows how the SERS spectra were amplified by the Fe 3 O 4 @Ag NPs obtained by PLAL in a 20 mM KCl aqueous solution and excited at different wavelengths. Most spectral modes were assigned to 4-MBA molecules, whereas the broad spectral feature near 669 cm –1 is evidence of the presence of magnetite . No vibrational bands from maghemite (γ-Fe 2 O 3 ) or hematite (α-Fe 2 O 3 ) were observed in the SERS spectra, indicating that the magnetic part of the hybrid nanoparticles was composed from a pure magnetite structure.…”

“…Most spectral modes were assigned to 4-MBA molecules, whereas the broad spectral feature near 669 cm –1 is evidence of the presence of magnetite. 42 No vibrational bands from maghemite (γ-Fe 2 O 3 ) or hematite (α-Fe 2 O 3 ) were observed in the SERS spectra, indicating that the magnetic part of the hybrid nanoparticles was composed from a pure magnetite structure. Figure 5 B presents the SERS enhancement factors (EFs) calculated at different laser excitation wavelengths for the two most prominent spectral modes of 4-MBA at 1073 and 1581 cm –1 .…”

Magneto-plasmonic nanostructures for SERS: magnetite decorated by silver and gold nanoparticles

“…DLS is suitable for nanoparticle characterization and analysis of colloidal dispersions. Magnetic measurements were performed using a pulsed magnetic field with a duration of about 4 ms and a field strength up to 0.5 T (the measurement setup is presented in our previous work 35 ).…”