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

The core–shell nanoparticles with magnetic Fe3O4 as core and porous SiO2 as shell were synthesized by the hydrolysis and condensation of tetraethyl orthosilicate on Fe3O4 seed in an alkaline medium. Subsequently, the inorganic/organic hybrid nanocomposites based on core–shell Fe3O4@SiO2 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 Fe3O4@SiO2 surface. The as-synthesized nanocomposites possessed three functionalities: Firstly, the nanocomposites showed a selective fluorescence response toward Fe3+ 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 Fe3+ ion; Secondly, the nanocomposites were an excellent adsorbent, the adsorption efficiency for Fe3+ could reach 99.6% when the initial concentration was 200 mg/L without pH preadjustment, and over 85% for Zn2+, Hg2+ and Pd2+ ions. Moreover, the nanocomposites could be recycled by Na2EDTA, the desorption ratio of Fe3+, Zn2+, Hg2+ and Pd2+ 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.