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.