A Novel Ion Species‐ and Ion Concentration‐Dependent Anti‐Counterfeiting Based on Ratiometric Fluorescence Sensing of CDs@MOF‐Nanofibrous Films

Abstract Traditional fluorescent anti‐counterfeiting labels based on “on‐off” fluorescence can be easily cloned. It is important to explore advanced anti‐counterfeiting fluorescent labels with high‐level security. Here, a pioneering ion species‐ and ion concentration‐dependent anti‐counterfeiting technique is developed. By successive loading Cu 2+ ‐sensitive yellow emitted carbon dots (Y‐CDs) and Cu 2+ non‐sensitive blue emitted carbon dots (B‐CDs) into metal‐organic frameworks (MOFs) and followed by electrospinning, the B&Y‐CDs@MOF‐nanofibrous films are prepared. The results show that the use of MOF not only avoids the fluorescence quenching of CDs but also improves the fluorescence stability. The fluorescence Cu 2+ ‐sensitivity of the CDs@MOF‐nanofibrous films can be regulated by polymer coating or lamination. The fluorescent label consisting of different Cu 2+ ‐sensitivity films will show Cu 2+ concentration‐dependent decryption information. Only at a specific ion species and concentration (Cu 2+ solution of 40–90 µ m ), the true information can be read out. Less or more concentration (<40 or >90 µ m ) will lead to false information. The identification of the real information depends on both the species and the concentration. After Cu 2+ treatment, the fluorescence of the label can be recovered by ethylenediaminetetraacetic acid disodium (EDTA‐2Na) for further recycling. This work will open up a new door for designing high‐level fluorescent anti‐counterfeiting labels.