Unusual Red Shift of the Sensor While Detecting the Presence of Cd2+ in Aqueous Environment

A norbornene derived 8-hydroxyquinoline (N8HQ) is designed and synthesized. A "turn-on" ratiometric fluorescent response is observed for Cd(2+) in aqueous solution upon binding with N8HQ with a characteristic huge red shift of 164 nm. A lowest detection limit of 1.6 nM of Cd(2+) is achieved in the presence of other heavy metals.