A highly selective and sensitive fluorescent sensor for relay recognition of Zn 2+ and HSO 4 - /H 2 PO 4 - with "on-off" fluorescent responses.

A simple and effective fluorescent sensor bearing pyridine units was designed and synthesized. The sensor can detect Zn2+ with high selectivity accompanied by a distinct fluorescence turn-on response, inducing the fluorescent color markedly changed from darkness to bright green. The limit of detection (LOD) was calculated as 8.56 × 10−9 M with a good linearity (R = 0.95943). In addition, the chelate of sensor with Zn2+ can further recognize H2PO4−/HSO4− with notable fluorescence quenching behaviors over other anions and the LODs were as low as 3.44 × 10−6 M (R = 0.99762) and 3.84 × 10−6 M (R = 0.99315), respectively.