Tuning the size stability of MnFe2O4 nanoparticles: Controlling the morphology and tailoring of surface properties under the hydrothermal synthesis for functionalization with myricetin

In this work, manganese iron oxide nanoparticles (MnFe 2 O 4 NPs) were synthesized by hydrothermal method using sodium dodecyl sulfate, sodium hydroxide, iron chloride, and manganese chloride. Four morphologies (observed by electron microscopy) were selected to be studied: flakes, rough-octahedrons, regular-octahedrons, and icosahedrons. The four samples were functionalized with the myricetin flavonoid (Myr). Hence, tetraethyl orthosilicate was employed to coat a SiO 2 layer on the nanoparticles, and then, Myr was added for obtaining the so-call MnFe 2 O 4 NPs/Myr. The fast Fourier transform infrared spectroscopy (FTIR) confirmed the SiO 2 coating formation and the Myr-functionalization. In addition, both Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), demonstrated the high density of oxygen vacancies in the flakes and rough-octahedrons MnFe 2 O 4 NPs. This amount was higher than that observed in the regular-octahedrons and icosahedrons MnFe 2 O 4 NPs. Among the synthesized samples, the icosahedrons MnFe 2 O 4 NPs exhibited the maximum efficiency for Myr-functionalization due to 0.53 MnFe 2 O 4 NPs/SiO 2 mass rate for coupling 1 mg of Myr. This efficiency was attributed to the low oxygen vacancies concentration on the surface of the nanoparticles. The Myr-functionalization promoted a size stability enhancement (about twice) in all the samples, with no significant changes in size across 112 days (stored at RT).