A phenanthro[9,10-d]imidazole-based AIE active fluorescence probe for sequential detection of Ag+/AgNPs and SCN− in water and saliva samples and its application in living cells

Ag + and SCN − play extremely important roles in the fields of the physiology and environment. In this work, on the basis of phenanthro[9,10- d ]imidazole derivative ( DIPIP ) which can exhibit the aggregation-induced emission (AIE) properties in aqueous solution, we achieved a sequential on-off-on switch for Ag + and SCN − with high selectivity and sensitivity. A remarkable fluorescence quenching effect of Ag + on the probe DIPIP was observed with 1:2 stoichiometry , Subsequently, the fluorescence intensity of in situ generated DIPIP -Ag + ensemble was easily switched on after the interaction between Ag + and SCN − , which was attributed to the stronger affinity of SCN − to capture Ag + . In particular, the extreme limits of detection (LOD) for Ag + and SCN − in standard solutions were as low as to be 74.5 nM and 7.8 nM, respectively. Furthermore, the probe DIPIP and the DIPIP -Ag + ensemble could be used to detect Ag + in the real water and SCN − in smoker saliva samples, respectively. In addition, the sequential “on-off-on” fluorescence mode of DIPIP to Ag + and SCN − were also successfully applied in living HeLa cells.