Selective colorimetric and fluorescence 'turn-on' sensor for Ag+ and in-situ sensing of CN- (off-on-off) via displacement approach.

In this contemporary work we designed and synthesized a simple tetra dentate Schiff base, which displays colorimetric and fluorescence "turn on" sensing behavior towards Ag+ in aqueous DMF (50%) solution. Benesi Hildebrand-plot reveals 1:2 binding mode between probe and Ag+ with limit of detection down to 1.12μM. Cyclic voltammograms exhibits high anodic shift with Ag+ due to the charge transfer from ligand to metal ion. The binding mode was proved by NMR titrations, FE-SEM elemental analysis & advance DFT calculation. Additionally, the subsequent Ag+-complex also shows an extremely selective response to CN- among other anions due to the displacement of Ag+ via CN-, forming [Ag(CN)x]- species into the medium. Probe was used as coated paper test strip which served as mini colorimetric device for detection of Ag+ and CN-.