Highly sensitive and selective ESIPT-based near-infrared fluorescent probe for detection of Pd2+

Harmful metal ions have received intense attention. In particular, palladium, a rare inner transition metal, is the subject of intense research in light of its catalytic capabilities and the restrictions on the levels of residual harmful metal ions in end products，has attracted wide spread interest from chemists. A near-infrared Pd2+ probe Cy202 has been synthesized that exhibits pronounced fluorescence enhancement in the presence of Pd2+. The Pd2+ recognition properties were examined by using UV–Vis spectroscopy and fluorescence spectroscopy in DMSO/PBS buffer solution (pH 7.40, 8/2, v/v). The solution of the probe exhibits color change turned from yellow to brown upon the addition of Pd2+ while no significant response to other metal ions. The detection limit was calculated as low as 0.52 μM. The probe could be useful for imaging Pd2+ in palladium-containing catalyst and samples.