Smartphone-integrated ratiometric fluorescent sensor based on Al-doped carbon dots for specific detection of chlortetracycline.

The widespread use of chlortetracycline (CTC) in agriculture and aquaculture has raised significant concerns regarding environmental contamination and human health risks. There is a critical demand for developing rapid, sensitive, and selective detection techniques for CTC identification. In this study, we introduced a smartphone-integrated ratiometric fluorescent sensor utilizing Al-doped carbon dots (Al-CDs), which were synthesized through a straightforward one-pot hydrothermal method. CTC quenches Al-CDs' fluorescence at 400 nm via the inner filter effect. Concurrently, a distinct fluorescence signal at 500 nm emerged, resulting from the enhanced intrinsic fluorescence of CTC upon its chelation with Al3+ on the surface of Al-CDs. This ratiometric fluorescence spectral response enables a visible color shift from blue to green upon UV irradiation. The constructed sensor achieves a remarkable detection limit of 0.17 μM and displays exceptional specificity toward CTC among other antibiotics, metal ions and amino acids. Successful application in real water samples yielded satisfactory recovery rates (98.5-110.6%), highlighting the potential of this smartphone-integrated platform for on-site and quantitative CTC detection.