Benzil‐Dihydrazone Based Bis‐Schiff Base Dual‐Sensor for Expeditious Colorimetric Detection of Ni²⁺ and Fluorometric Detection of Ag⁺: Environmental and Biological Applications

In this research, a novel dual chemosensor L has been reported. It has been characterised by FTIR, ¹H-NMR, ESI-MS, elemental analyses, X-ray single crystal analysis and DFT studies. In a 1:1 methanol-water medium (v/v), the receptor L detected Ni²⁺ with color change from colorless to yellow and Ag⁺ with turn-on fluorescence enhancement. UV-vis spectroscopy, fluorescence titration, FTIR and ESI-MS have been used to analyse the response mechanisms of fluorescent colorimetric sensing. The colorimetric sensitivity for Ni²⁺ is 3.0 × 10^-7 M and fluorometric sensitivity for Ag⁺ is 7.2 × 10^-7 M; both the values are sufficient below the WHO permissible limits in aqueous solution. From the Job's plot measurements and the ESI-MS spectrum, 2: 1 stoichiometric complexation between L and Ni²⁺/Ag⁺ has been established. Receptor L shows remarkable detection ability in a wide pH range of 4-9 and can be successfully applied for the detection and quantification of Ni²⁺ ions in environmental samples, and Ag⁺ ions in BSA protein. At the specified doses and incubation times, L can be used as an anticancer drug and a selective sensor for bio-imaging of Ag⁺ ion without having any cytotoxic effects.