Crucial factors affecting the physicochemical properties of sol-gel produced FeO@SiO-NH core-shell nanomaterials.

Multifunctional nanomaterials with task-specific physicochemical properties, especially core-shell nanostructures with FeO core and NH-functional shells (FeO@SiO-NH), have been extensively investigated as high-performance adsorbents, catalysts and catalyst supports; and in most cases the controllable sol-gel technique is the choice for fabrication of this kind of widely applied materials. Herein, we demonstrated that mono-dispersed and spherical FeO@SiO-NH nanomaterials with magnetic response core, NH-functional shell structure can be facilely prepared by co-condensation of TEOS with APTMS using a versatile sol-gel process. It was shown that the proper usage of APTMS and appropriate pre-hydrolysis time of TEOS were crucial and key steps for formation of highly uniform and desirable amino loading FeO@SiO-NH materials. The TEOS pre-hydrolysis and the critical time (around 90 min) before the addition of APTMS prove to be vital for uniform structure evolution, while the appropriate concentration of APTMS (~2.28 mmol L in our system) leads to well-dispersed materials with relatively high loading of amino functionality. The as-prepared FeO@SiO-NH magnetic nanoparticles prepared under optimum conditions possessing superparamagnetic behavior, uniform core-shell structure (~200 nm in diameter), relatively large BET surface area (~138 m/g) and high incorporation of amino-functionality (~2.90 wt %). [ABSTRACT FROM AUTHOR]