A turn-off fluorescent chemical sensor based on a thiazole-Schiff base structure for highly selective and accurate detection of Cu ²⁺ in living cells

A Schiff base fluorescent probe, HTT, based on a sulfonylhydrazone structure was designed and synthesized for the sensitive and selective detection of Cu²⁺. The probe HTT exhibits good anti-interference performance toward Cu²⁺ in the presence of a variety of metal ions. After the addition of Cu²⁺, it can quickly respond within 40 seconds, and the fluorescence detection limit is 1.10 nM. The coordination ratio of probe HTT and Cu²⁺ is 2 : 1, and the coordination reaction between CN, SO and Cu²⁺ limits the formation of hydrogen bonds between the hydroxyl group and CN, disrupting the spatial coplanar effect of the probe molecule and thereby inducing fluorescence quenching. The probes can be recovered and reused using EDTA for the detection of Cu²⁺. The probe was also applied to the successful monitoring of Cu²⁺ in living cells and real water samples.