Highly Sensitive and Selective Fluorescent Sensor for Distinguishing Cadmium from Zinc Ions in Aqueous Media

A fluorescent sensor, QA, based on acetamidoquinoline with DPA as receptor, was synthesized. In aqueous buffer solution, QA demonstrates high selectivity for sensing Cd2+ with about 40-fold enhancement in fluorescence quantum yield and picomolar sensitivity (K-d = 0.25 +/- 0.03 pM). Moreover, sensor OA can distinguish Cd2+ from Zn2+ via two different sensing mechanisms (PET for Cd2+; ICT for Zn2+), and the discrimination is even possible by naked eyes.