Synthesis of trifunctional inorganic/organic hybrid nanocomposites and their applications for recognition and elimination of heavy metal ions

The core–shell nanoparticles with magnetic Fe 3 O 4 as core and porous SiO 2 as shell were synthesized by the hydrolysis and condensation of tetraethyl orthosilicate on Fe 3 O 4 seed in an alkaline medium. Subsequently, the inorganic/organic hybrid nanocomposites based on core–shell Fe 3 O 4 @SiO 2 nanoparticles were fabricated using “grafting-from” strategy, in which a macrocyclic dioxotetraamine (1,4,8,11-tetraazacyclotetradecane-5,7-dione, TACTDD) was grafted onto the end of Fe 3 O 4 @SiO 2 surface. The as-synthesized nanocomposites possessed three functionalities: Firstly, the nanocomposites showed a selective fluorescence response toward Fe 3+ ion with a detection limit of 6.0 × 10 −7  mol/L, the eye-perceived fluorescence quenching under ultraviolet light could be used for the qualitative recognition of Fe 3+ ion; Secondly, the nanocomposites were an excellent adsorbent, the adsorption efficiency for Fe 3+ could reach 99.6% when the initial concentration was 200 mg/L without pH preadjustment, and over 85% for Zn 2+ , Hg 2+ and Pd 2+ ions. Moreover, the nanocomposites could be recycled by Na 2 EDTA, the desorption ratio of Fe 3+ , Zn 2+ , Hg 2+ and Pd 2+ ions only reduced slightly with six cycles, and all remained above 91%; Thirdly, the nanocomposites had superparamagnetism with a magnetization of 29.6 emu/g, this strong magnetic sensitivity can facilitate the sustainable removal of heavy metal ions in practical applications.