Preparation of nanosized hollow silica spheres from Na2SiO3 using Fe3O4 nanoparticles as templates

Nanosized hollow silica spheres with average diameters from 43 to 70 nm were prepared. The pH and Na2SiO3 to Fe3O4 ratio for preparing silica-coated Fe3O4 core-shell composites affect sphere diameter, shell thickness and porous structure of hollow silica spheres. The release rate of ammonium glyphosate could be tuned by using hollow silica spheres with different shell thicknesses.