Preparation and characterization of magnetic nanoparticles and their silica egg-yolk-like nanostructures: A prospective multifunctional nanostructure platform

A facile solvothermal method was successfully utilized to synthesize well-crystallized magnetite (Fe3O4) nanoparticles through high-temperature decomposition of intermediate complexing compound using diethylene glycol (DEG) and diethanolamine (DEA) as solvent and complexing agent. Then a novel egg-yolk-like magnetic silica nanostructure, composed of a. silica core and another silica shell with magnetic nanoparticles embedded in the boundary, was successfully prepared by a facile one-step sol-gel technique. The experimental parameters were carefully investigated to optimize the preparation process. The diameters of final products could be effectively tuned in a wide range by use of easily obtained silica colloidal cores with different diameters. Shell thickness could be controlled by changing the addition amount of tetraethyl orthosilicate (TEOS). On the basis of the characterization, We propose a formation mechanism of the nanostructure. The pre-addition of acid solution played a key role in the procedure, enhancing the electrostatic attraction between magnetic nanoparticles and silica spherical cores. Because of the offered magnetic properties to silica beads, some aggregations were found resulting from the magnetic attraction, which shall be further improved. This strategy provides a facile method to integrate magnetic nanoparticles into a silica matrix. Additionally, this novel magnetic silica narrostructure presents a good platform to construct multifunctional nanostructures by the well-developed composite strategy based on silica chemistry.