A multiple fluorescein-based turn-on fluorophore (FHCS) identified for simultaneous determination and living imaging of toxic Al and Zn by improved Stokes shift.

A multiple turn-on fluorophore (FHCS), combining fluorescein, hydrazone, cyanuric chloride and salicylaldehyde chromone into a molecule, was identified and developed based on density functional theoretical calculation. It was expected that FHCS could express exclusive fluorescent signals and improved Stokes shifts when chelating Al or Zn. After it was synthesized and characterized in detail, it was noted that FHCS could turn-on fluorescently discriminate trace Al and Zn under the optimized conditions, i.e., from no-fluorescence to strong blue fluorescence for Al and to green fluorescence for Zn with low detection limits of 5.37 × 10 M and 7.90 × 10 M respectively. Owing to its low toxicity, FHCS was successfully applied for quantitative determination of Al and Zn in natural aqueous samples and toxicity evaluation of Al and Zn in living cells and bio-tissues with excellent linear relationships. The action mechanisms for FHCS with Al and Zn were confirmed to form stable 5-member-co-6-member condensed rings between Al/Zn and N/O atoms in FHCS by both theoretic and experimental methods, which resulted in turn-on fluorescence with different dipolar moments and improved Stokes shifts.