A Pd0-responsive turn-on fluorescent probe integrated with a gel-based smartphone platform for portable detection of zero-valent palladium

CZID-Pd is a turn-on fluorescent probe for selectively detecting zero-valent palladium species. • The probe successfully quantified Pd 0 in real water samples with satisfactory recoveries. • Agarose gel enabled portable visual Pd 0 detection through rapid smartphone-assisted RGB analysis. Zero-valent palladium (Pd 0 ), a catalytically important species widely involved in industrial, energy, and pharmaceutical processes, has attracted increasing attention owing to its potential environmental release and associated health risks. However, the high reactivity and transient nature of Pd 0 make its selective recognition and reliable detection particularly challenging. In this work, a novel turn-on fluorescent probe, CZID-Pd, was designed and synthesized based on a Pd 0 -triggered Tsuji-Trost deallylation mechanism. Spectroscopic studies demonstrated that CZID-Pd enables sensitive and selective detection of Pd 0 in the presence of competing species, while maintaining good photostability and reproducibility. The probe exhibited a large Stokes shift of 127 nm and a low detection limit of 0.22 μM. For visual detection, CZID-Pd was further incorporated into an agarose hydrogel to construct a portable smartphone-assisted sensing platform, enabling semiquantitative analysis of Pd 0 through RGB image analysis. The gel sensor showed satisfactory accuracy and reproducibility in real water samples. In addition, CZID-Pd displayed low cytotoxicity and was successfully used for fluorescence imaging of exogenous Pd 0 in living cells. By integrating molecular probe design, gel encapsulation, and smartphone-assisted quantification, this work provides a practical sensing platform for Pd 0 with potential applications in environmental monitoring and bioimaging. Download: Download high-res image (164KB) Download: Download full-size image