Epsilon‐Fe₂O₃ Nanocrystals inside Mesoporous Silicas with Tailored Morphologies of Rod, Platelet and Donut

Abstract

The ϵ‐Fe2O3 polymorph of iron oxide, which has outstanding physical properties, is successfully stabilized inside mesoporous silica particles with tailored shapes. Using mesoporous silica particles with three different morphologies of rod, platelet and donut, we obtain ϵ‐Fe2O3/mesoporous silica nanocomposites. Iron oxide is loaded inside the porosity using a two steps impregnation cycle: solvent‐free impregnation followed by oxidation under 1000 °C. The amount of loaded iron oxide can be enhanced using two successive impregnation cycles. We fully characterise these nanocomposite particles with a wide panel of techniques to establish the exact amount of loaded iron inside the porosity, the nature of the iron oxide phase and the size of the nanocrystals. As a result, we conclude that ϵ‐Fe2O3 nanocrystals can be confined and stabilized in all types of morphologies, even inside the donut morphology which possesses closed mesopores.

Simple Fabrication of ϵ‐Fe2O3 Nanoparticles Containing Silica Monoliths with Enhanced Coercivity

“…The second step is the impregnation of the ordered mesoporous silica monolith by a Fe(NO 3 ) 3 salt solution in order to introduce the precursor of the Fe 2 O 3 phase in the porosity. [38][39][40] The third and last step is the thermal treatment, which transforms the precursors loaded in the porosity into the Fe 2 O 3 phase and densifies the silica matrix. Upon the thermal treatments, the monolith breaks into few pieces, as shown on the photographs of Scheme 1.…”

“…Monoliths with very few cracks are obtained. The use of ordered mesoporous silica for the formation of the ϵ‐Fe 2 O 3 phase has already been reported, [37,38] but the compounds were obtained in the powder form, never in the form of a monolith, which is crucial to obtain a large‐size magnet at the end of step 3. The second step is the impregnation of the ordered mesoporous silica monolith by a Fe(NO 3 ) 3 salt solution in order to introduce the precursor of the Fe 2 O 3 phase in the porosity [38–40] .…”

“…The use of ordered mesoporous silica for the formation of the ϵ‐Fe 2 O 3 phase has already been reported, [37,38] but the compounds were obtained in the powder form, never in the form of a monolith, which is crucial to obtain a large‐size magnet at the end of step 3. The second step is the impregnation of the ordered mesoporous silica monolith by a Fe(NO 3 ) 3 salt solution in order to introduce the precursor of the Fe 2 O 3 phase in the porosity [38–40] . The third and last step is the thermal treatment, which transforms the precursors loaded in the porosity into the Fe 2 O 3 phase and densifies the silica matrix.…”

Magnetic Mesoporous Silica Nanorods Loaded with Ceria and Functionalized with Fluorophores for Multimodal Imaging

“…In the first step of the study, mesoporous silica rods of two aspect ratios were synthesized. In a typical synthesis, adapted from the literature, ,, 2 g of Pluronic P123 was dissolved in 95 mL of 1.7 M hydrochloric acid solution contained in a reaction bottle of 250 mL capacity (Simax). After obtaining a homogeneous solution, the temperature was increased to 40 °C and the solution was stirred at 700 rpm with a magnetic stirring bar (dimensions: 25 mm × 6 mm).…”

“…Nanocomposites with unique properties and synergistic actions from different components have a great potential to be used in fields such as biomedicine, , catalysis, , and energy. , Mesoporous silica nanocomposites are mechanically and thermally stable, present large surface areas and pore volumes with narrow pore size distributions, and their particle and pore sizes can be controlled. − These characteristics endorse mesoporous silica as an attractive platform to design nanocomposites by loading the pores with different chemical species. Such materials can encapsulate large amounts of nanoscopic cargo while maintaining their robustness and pore ordering.…”