Eco-friendly fluorescent detection method for Cu2+2+ions combined with smartphone-integrated paper strip sensors based on highly fluorescent 2-aminoterephthalic acid in milk samples

The creation of smart, real-time sensing devices is crucial in food monitoring, though it continues to be a major challenge. Here, we report an eco-friendly fluorescent detection method for Cu2+ ions using 2-aminoterephthalic acid (NH2-H2BDC). Fluorescence (FL) quenching occurs at 425 nm under excitation at 330 nm, with detection limits (LOD) as low as 16.25 nM for Cu2+ ions. Additionally, a smartphone can visually and quantitatively detect Cu2+ ions by analyzing the RGB values on test paper. The results show high sensitivity, with a LOD of 11.07 mu M. This work not only reveals fluorescent detection methods but also develops a convenient, low-cost, and portable smartphone-integrated paper strip for Cu2+ ion sensing. Two metrics, AGREEprep and BAGI, were employed to assess the method's environmental friendliness. The evaluation confirmed its exceptional eco-friendliness. This method marks a significant advancement for Cu2+ ion monitoring in diverse fields, especially food monitoring.