Development of a Rhodamine-Based Chemosensor for Cd²⁺ Ions: A Combined Approach of Colorimetric, Fluorescent...

This paper presents the design and synthesis of a new rhodamine-based Schiff base chemosensor (L) with exceptional selectivity and sensitivity for Cd²⁺. An analysis of L was conducted using various spectroscopic techniques, thereby validating its structure and activity. The chemosensor exhibited a clear turn-on fluorescence response and significant colour change with Cd²⁺ ions in acetonitrile. Binding investigations confirmed that L interacts with Cd²⁺ ions in a 1:1 ratio, as shown by Job's plot and Benesi-Hildebrand (B-H) analysis. The binding constant (K_a = 0.107 × 10⁴) highlights the strong and specific interactions between L and Cd²⁺ ions.The limit of detection was found to be (LOD = 2.01 nM) for Cd²⁺ ions. DFT studies confirmed the stability of the L-Cd²⁺ complex, indicating the coordination of Cd²⁺ to the four atoms in L. The reversible properties of L in the presence of EDTA illustrate its potential as a reusable chemosensor and emphasise its INHIBIT molecular logic gate functionality. Molecular docking analyses of L with the human DNA-binding protein 5VBN were performed to assess its binding affinity and interaction characteristics. The practical application was demonstrated by the effective detection of Cd²⁺ in actual water, vegetable and fruit juice samples, solid-state sensing tests and filter paper-based assays, highlighting its potential for environmental monitoring.