A Nanosensor for Naked-Eye Identification and Adsorption of Cadmium Ion Based on Core–Shell Magnetic Nanospheres

Fe3O4@SiO2 nanospheres with a core-shell structure were synthesized and functionalized with bis(2-pyridylmethyl)amine (BPMA). The photoresponses of the as-obtained Fe3O4@SiO2-BPMA for Cr3+, Cd2+, Hg2+ and Pb2+ ions were evaluated through irradiation with a 352 nm ultraviolet lamp, and Fe3O4@SiO2-BPMA exhibited remarkable fluorescence enhancement toward the Cd2+ ion. The adsorption experiments revealed that Fe3O4@SiO2-BPMA had rapid and effective adsorption toward the Cd2+ ion. The adsorption reaction was mostly complete within 30 min, the adsorption efficiency reached 99.3%, and the saturated adsorption amount was 342.5 mg/g based on Langmuir linear fitting. Moreover, Fe3O4@SiO2-BPMA displayed superparamagnetic properties with the saturated magnetization of 20.1 emu/g, and its strong magnetic sensitivity made separation simple and feasible. Our efforts in this work provide a potential magnetic functionalized nanosensor for naked-eye identification and adsorption toward the Cd2+ ion.