A Schiff base probe for competitively sensing Cu2+ and cysteine through hydrolysis, complexation, and cyclization

Starting at HBTA, a summary of ways to detect Cu2+ and cysteine. [Display omitted] •A concept about nested probe was completed for achieving multistage responses.•Three-stage quantitative detection on Cu2+ with different fluorescent signals.•Cu2+-promoted probe decompose and the decomposition products can cyclize cysteine.•Logical fluorescence based on concentration and order of Cu2+ and cysteine. The form of a single response to a single target analyte limits the development of fluorescent probes. Here, a probe (HBTA) based on HBT (2-(2-Hydroxyphenyl)-benzothiazole) was synthesized to achieve a concept about nested probe, completing continuous detections. HBTA through low concentration Cu2+ gives birth to a new probe (HBT-CHO) that can detect Cu2+ by complexation and Cys by cyclization (HBT-Cys). These processes are accompanied by different fluorescent signal changes and can quantitatively detect Cys and Cu2+. Furthermore, HBT-CHO, HBT-Cys, and Cys can bind Cu2+, so competitive fluorescent response of Cu2+ can take place through alternate addition of Cu2+ and Cys. At this stage, the response becomes too complex to accurately quantify, but it is still dependable to predict changes in the content of the mixture system through competitive fluorescent changes. In summary, it is because of the existence of the nested pattern that HBTA completes multiple forms of responses to Cu2+ and Cys.