One-step sustainable preparation of superparamagnetic iron oxide nanoparticles supported on mesoporous SiO2

Superparamagnetic iron oxide nanoparticles (SPIONs) supported on high surface area mesoporous SiO2 are advanced materials of great interest in catalysis, adsorption and biomedicine. Here we present a new process to prepare SPION/SiO2 materials by the impregnation and insitu decomposition of Fe(NO3)(3)center dot 9H(2)O on mesoporous SiO2 supports in a 25-50 % mol ethanol + CO2 mixture at 523 K and 25.0 MPa. gamma-Fe2O3 nanoparticles (NPs) of average size between 6-9 nm were homogeneously distributed on the supports. NPs deposited into the SBA-15 mesopores but mostly on the external surface of MCM-41. Materials prepared with the highest ethanol content were very homogeneous. Magnetic measurements confirmed the superparamagnetic nature of the materials at room temperature. The process proposed is sustainable and scalable, avoids tedious preparations and the additional high temperature treatment under a controlled atmosphere, as the metal decomposition is performed insitu in the CO2-expanded liquid mixture. (C) 2020 Elsevier B.V. All rights reserved.