A novel ratiometric fluorescent probe based on dual-emission CDs and magnetic ion-imprinted polymers for cadmium (Cd) adsorption and detection in edible fungi

Abstract

A novel ratiometric fluorescence “adsorption + detection” sensing system based on dual-emission ion-imprinted polymers (IIPs) formed from OR-CDs on functionalized magnetic carriers (Fe₃O₄@SiO₂–CC) was developed, enabling the highly specific adsorption and detection of Cd²⁺ in edible fungi. First, OR-CDs were synthesized via a simple calcination method using salicylic acid and 5-amino-1,10-phenanthroline as carbon sources. Second, Fe₃O₄@SiO₂–CC magnetic nanoparticles were obtained by coating Fe₃O₄ with vinyl-functionalized silica spheres (SiO₂–CC). Finally, a surface ion-imprinted microsphere layer was synthesized on the surface of Fe₃O₄@SiO₂–CC, using Cd²⁺ as the template ion and OR-CDs as the fluorescent monomer, to construct a ratiometric fluorescence (I₄₁₀/I₅₈₀) “adsorption + detection” system (OR-CDs@SIIPs). The results showed that the as-prepared OR-CDs@SIIPs exhibits uniform particle size, good dispersion, and strong fluorescence emission. Under optimal conditions, adsorption equilibrium was reached within 15 min, and the maximum adsorption capacity for Cd²⁺ reached 38.021 μg mg⁻¹. The constructed OR-CDs@SIIPs system showed desirable detection performance, including a wide linear range (0.01–5.0 μg mL⁻¹), low limit of detection (LOD) (0.001 μg mL⁻¹), low relative standard deviation (1.06%), and acceptable spiked recoveries (96.5–104.3%). Therefore, this study provides a new strategy for the efficient adsorption and detection of metal ions (e.g., Cd²⁺) in actual samples.