Due to the sensitivity of fluorescent emitters to environmental changes, fluorescence-based probes have emerged as one of the most effective tools for detecting heavy metals, even at extremely low concentrations. Leveraging this advantage, fluorescence-based probes can be engineered to exhibit high sensitivity and selectivity for sensing environmental toxicity. Here, we present a fluorescence-based probe, N-butyl-4-alloxy-1,8-naphthalimide, specifically engineered for real-time palladium detection via a fluorogenic mechanism. This custom-designed molecule incorporates a naphthalimide fluorophore and an allyl ether tail, which undergoes Pd⁰-mediated Tsuji–Trost deallylation. The reaction produces multi-mode optical response: a marked fluorescence enhancement, ratiometric signals, and visible color change under irradiation, enabling detection of Pd ions with improved reliability. In addition, integration with smartphone imaging and color analysis applications facilitates low-cost, equipment-free detection in field settings. The combination of organic probe design, optical signal transduction, and digital readout establishes this system as a promising tool for environmental monitoring, industrial hygiene, and public health diagnostics. Besides, chemo-sensing of metal ions, the fluorogenic probes could also be used for biomedical imaging and single-molecule fluorescence imaging of catalytic reactions, some of which are currently pursued in our lab.
