Selective and sensitive fluorescence detection of Pd (II) in 100% water and imaging application in living cells

A novel quinoline-based fluorescent chemosensor ( QB-3) for Pd2+ was designed and achieved a good sensing performance in 100% pure water. The QB-3 showed a selective and fast fluorescence quenching response in the presence of Pd2+ without significant competition interferences from others metal ions. The fluorescence intensity at 411 nm showed a linear decrease with the addition of the Pd2+ concentration in the range of 0-5 mu M. It was found that the detection of limit was 0.089 mu M (S/ N = 3), lower than the threshold limit WHO recommended. Job's plot investigation revealed a 2:1 stoichiometry between the QB-3 and Pd2+, and the complex was confirmed by mass spectral analysis. The DFT calculation predicted that an electron transfer process toward Pd2+ in the complex may be responsible for the fluorescence quenching of QB-3. The practical application in real water samples and fluorescence imaging in living cells was also achieved.