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

A new type of colorimetric, fluorescent palladium (Pd) probe characterized with beaconing fluorescence signal in the quiet near-infrared (NIR) region (centered ~ 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 Pd⁰-mediated oxidative addition and reduction elimination reactions, yielding typical D-π-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 Pd⁰ recognition process of the probe via the formation of the fluorescent reaction product with largely extended π-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.