A new colorimetric, near-infrared fluorescent probe for rapid detection of palladium with high sensitivity and selectivity

A new type of colorimetric, fluorescent palladium (Pd) probe characterized with beaconing fluorescence signal in the quiet near-infrared (NIR) region (centered similar to 717 nm), recognition response time of approximately 3 min, limit of detection (LOD) down to 5.1 ppb, and excellent recognition specificity over a wide range of interfering metal cations was developed. It is believed that the probe underwent sequential Pd-0-mediated oxidative addition and reduction elimination reactions, yielding typical D-pi-A molecular skeleton of the final reaction product capable of intramolecular charge transfer (ICT). The benzothiazole moiety of the probe molecular skeleton is believed to play a vital trole in shifting the beaconing fluorescence signal to the quiet NIR region and accelerating the Pd recognition process of the probe via the formation of the fluorescent reaction product with largely extended pi-delocalization. With unique advantages, the fluorescent probe we developed will find practical applications for detecting residual Pd with concentration below the safety margin in pharmacy and biomedical engineering.