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 SiO2 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 SiO2 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/SiO2 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).