Spectroscopic involvement detection for Al3+ and Fe3+ ions through fluorescent probe in gunshot residue samples

Abstract

A new way of detecting metal ions in gunshot residue (GSR) samples was carried out by using fluorescent chemosensor. The designed and synthesized chemosensor R was successfully characterized by NMR and mass spectroscopic techniques. The sensor R was synthesized by single step condensation method by taking 2-hydroxy-1-naphthaldehyde and naphthyl methyl amine. Sensor R successfully detects Al³⁺ and Fe³⁺ ions in both colorimetric and fluorimetric ways in DMSO-H₂O (1:1 (v/v), 50 mM, HEPES buffer, pH = 7.4) solutions. Although, R was treated with GSR samples which had series of metal ions confirmed through SEM-EDx data, it particularly detects Al³⁺ and Fe³⁺ ions in spectroscopic techniques. Before treating with GSR samples, sensor R emits very weak absorption and fluorescence emission which is due to C-N free rotation and keto-enol tautomerism. Upon treating with GSR samples, in colorimetric method it detects Fe³⁺ ions and Al³⁺ ions in fluorimetric method, C-N free rotation and keto-enol tautomerism is restricted and there occurs the change in absorption and fluorescence emission. At the present stage, sensor R could acts as a fluorescence agent in forensic applications for the detection of metal ions.