A Reversible Fluorescent Chemosensor for the Selective Detection of Cu²⁺ and CN^- ions by Displacement Approach

A novel fluorescence chemosensor BDP (2-(1-(benzothiazol-2-yl)-5-(4-(diphenylamino)phenyl)-4,5-dihydro-1H-pyrazol-3-yl)phenol) has been synthesized and its sensing behavior has been screened towards various cations by absorption, emission and mass spectroscopic techniques. The probe BDP detects Cu²⁺ ions preferentially over other metal ions, and the resulting BDP-Cu²⁺ ensemble acts as a secondary sensor for cyanide anion detection over other anions. The fluorescence intensity of the probe BDP is quenched when it comes into contact with Cu²⁺ ions, but it is increased reversibly when it comes into contact with cyanide anion, according to spectroscopic measurements. Along with this, optical studies indicate that the sensor BDP has capability to sense Cu²⁺ and CN^- ions selectively over other examined competitive ions with the LOD of 2.57×10^-8 M and 2.98×10^-8 M respectively. The detection limit of Cu²⁺ ions is lower than the WHO recommended Cu²⁺ ions concentration (31.5 µM) in drinking water. On the basis of "on-off-on" fluorescence change of the probe BDP upon interaction with Cu²⁺ and CN^- ions, a possible mechanism for this selective sensing behavior was presented and IMPLICATION logic gate was successfully designed. Furthermore, cell imaging investigations were used to investigate the probe BDP's biological applicability.