A novel smartphone-assisted fluorescence probe based on benzothiazole-derived Schiff base enables accurate detection of Cu2+/Cu+ and H2S and its portable applications.

Copper ions and hydrogen sulfide pollution exert severe adverse effects on plants and other organisms. Consequently, the rapid, real-time, and accurate monitoring of Cu2+/Cu+ and H2S remains challenging. In this study, we designed and synthesized a novel benzothiazole-functionalized salicylaldehyde-based Schiff base (HDBS) for the reversible dual detection of Cu2+/Cu+ and H2S. Probe HDBS enables sequential, fluorescence- and colorimetric-based detection of Cu2+/Cu+ and H₂S in a MeOH-PBS solution system. The high selectivity and water solubility make it suitable for monitoring Cu2+ and H2S in real food samples with sensitivity. The detection limits were as low as 3.73 nM for Cu2+ (4.43 nM for Cu+) and 71.2 nM (65.1 nM) for H2S, enabing for trace-level detection. Furthermore, HDBS-based test paper strips, coupled with smartphone-assisted imaging analysis, provide a promising platform for on-site, real-time, quantitative, and colorimetric visualization of Cu2+/Cu+ and H₂S, enabled by its rapid response and recyclable characteristics. Finally, HDBS demonstrated successful application in fluorescent imaging of Cu2+/Cu+ and H₂S in plant roots, A549 living cells, and zebrafish models, exhibiting robust photostability, good biological permeability, and low cytotoxicity.