A highly sensitive and selective ratiometric fluorescent sensor for Zn ²⁺ ion based on ICT and FRET

A ratiometric sensor (QA) for detecting Zn²⁺ with high sensitivity and selectivity was reported. The fluorescence changes of sensor upon the addition of Zn²⁺ were attributed to the conjugation of internal charge transfer and fluorescence resonance energy transfer mechanisms. There is a good linear relationship between the fluorescence ratio I _497nm/I_420nm and the concentrations of Zn²⁺ ranging from 0 μM to 40 μM, which makes an effective ratiometric detection of Zn²⁺ ion. The limit of detection (LOD) was evaluated to be 33.6 nM. The imaging experiments indicated that QA is cell-permeable and can be used to detect Zn²⁺ within living cells with good selectivity over Cd²⁺.