Real-Time Probe for the Efficient Sensing of Inorganic Fluoride and Copper Ions in Aqueous Media

A highly sensitive and efficient rhodamine 6G based probe (P3) was synthesized for the real-time sensing of F- and Cu2+ ions. The probe P3 was able to show significant color change from brown to pink in the presence of F- and yellow to orange in presence of Cu2+ ions. The UV-vis studies confirm that the probe P3 was able to detect F- and Cu2+ ions over other ions. Further, UV-vis titration studies were carried out to understand the detection mechanism and stoichiometry between P3: F- and P3: Cu2+ ions. H-1-NMR titration was performed to confirm the F- ion binding to probe P3, where, deprotonation of hydrazone proton (-C=N-NH-) was observed. In addition, the limit of detection for P3:F- and P3:Cu2+ ions were found to be 4.02 mu M and 1.64 mu M respectively which is useful for practical applications. Lastly, probe P3 was used to detect and quantify the F- ions present in a commercially available mouthwash product. Furthermore, P3 was adsorbed on the surface of silica microsphere to detect Cu2+ ions. Interestingly, the material could visually detect 1 ppm of Cu2+ ions which is lower than the permissible limit.