A novel puCDs@ZIF-8 composite for sensitive ratiometric fluorescence detection and efficient removal of tetracycline

Excessive tetracycline (TC) residues pose risks to human health and harm ecosystems, threatening ecological sustainability. To achieve trace detection and highly efficient removal of TC, this study designed and synthesized a composite material (puCDs@ZIF-8) by embedding waterborne polyurethane (WPU)-derived carbon dots (puCDs) in zeolitic imidazolate framework-8 (ZIF-8). Consequently, a novel ratiometric fluorescent probe was constructed. The dual-emission fluorescence signal originates from two mechanisms: (i) TC quenches the blue fluorescence of puCDs at 450 nm via the inner filter effect (IFE); (ii) coordination between Zn 2+ and TC triggers an aggregation-induced emission (AIE) effect, which gives rise to a new fluorescence emission at 530 nm. Both signals' intensities vary proportionally with TC concentration, enabling highly sensitive detection based on the fluorescence intensity ratio (F 450 /F 530 ). A wide linear concentration range of 0–60 μg mL −1 and a low detection limit (LOD) of 0.0089 μg mL −1 were achieved by the probe under optimized conditions. Notably, this sensitivity is significantly higher than that of pure puCDs (LOD = 0.343 μg mL −1 ). Application of the prepared probe to milk yielded favorable recoveries between 95.6 % and 106.3 %, confirming its practical utility for TC detection. In addition, the equilibrium adsorption capacity of puCDs@ZIF-8 for TC in aqueous solution reaches 409.45 mg g −1 , enabling efficient TC removal. This study provides novel insights into the construction of ratiometric fluorescent probes with removal capabilities.