Magnetite nanoparticles coat around activated γ-alumina spheres: A case of novel protection of moisture-sensitive materials against hydration

Abstract

Protection of various materials against hydration is of continuing interest to chemists and material scientists. We report on stabilization of porous surface of activated γ-alumina spheres (AAS) against hydration by an adhesive coat of nano-magnetite particles. The nano-Fe3O4-coated AAS were prepared in the ultrasound-agitated suspension of magnetite nanoparticles in heptane and were characterized by using X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET surface area analysis and X-ray photoelectron spectroscopy (XPS). It is deduced that nanoparticle-alumina bonding interaction in non-polar organic solvent is enhanced by van der Waals attractive forces and that sonication induces changes in alumina morphology only in regions of contact between alumina and magnetite nanoparticles. The coated AAS submerged in still water avoid hydration and remain permeable by small gaseous (N2) molecules, while those soaked in moving water lose part of their coat and undergo hydration. The pristine and the coated AAS were briefly compared for their ability to degrade model antibiotics by using LC-MS analysis. It is confirmed that the degradation of trimethoprim is more efficient on the coated AAS. Our results are challenging for further research of Coulombic interactions between nano-particles and appropriate solid supports.