A single carbazole based chemosensor for multiple targets : Sensing of Fe³⁺ and arginine by fluorimetry and its applications

A simple carbazole derived Schiff base fluorescent chemosensor (C1) has been synthesized and characterized successfully to recognize sequentially Fe³⁺ ion and an amino acid, arginine (Arg). The chemosensor (C1) shows specific response “on–off-on” towards Fe³⁺ and Arg among different competing cations and amino acids. Interestingly, the fluorescence emission got turned-off for C1-Fe³⁺ complex and turned-on for the detection of arginine. The binding ability of sensor C1 with Fe³⁺ and arginine was advocated using fluorometric titrations, Job's plot, B-H plot and density functional theory studies (DFT). The significant color changes of sensor C1 from aqua blue to transparent blue to aqua blue were monitored under UV-lamp of 365 nm during the sensing process, which additionally supported the complex formation. The sensor C1 accomplishes the lowest detection limit of 12.22 × 10⁻⁹ M and binding constant of 2.09 × 10⁴ M⁻¹ for Fe³⁺ detection. This efficient fluorescent candidate was utilized for the detection of Fe³⁺ in applications such as molecular logic gate, smart-phone based on-site detection, live cell bio-imaging and real sample analysis.