Improved sensing of metal ions via abnormal enhancement of the anti-stokes emission of the near-infrared fluorescent probe

Sensing of toxic and heavy metals is of great importance for protecting environment and health monitoring. Here we demonstrate an improved fluorescent probe operating in the near-infrared (NIR). The probe represents a NIR tricarbocyanine dye with 2,2 & PRIME;-dipicolylamine meso-group which is able to chelate zinc, cobalt and palladium ions. We show that the probe operation via monitoring of the anti-Stokes photoluminescence provides much better sensitivity of the probe compared to its Stokes photoluminescence. Particularly, it is shown that the anti-Stokes photoluminescence increases by more than an order of magnitude and can reveal additional features of the dye metal complex not observed via the Stokes emission.