Furan-formulated benzothiazole based Schiff bases for highly selective visual and fluorometric detection of Cu2+ ion with density functional theory studies and its application for real-life samples

Abstract

In this work, we describe the synthesis of a Schiff base (R1) derived from furfural and 2-hydrazinobenzothiazole which displayed turn-off selective fluorescent chemo-sensing properties for Cu2+ ions in THF: HEPES buffer (9:1, v/v) solution. The molecular structure of the Schiff base (R1) was characterized by various spectroscopic techniques such as FTIR, 1H NMR, 13C NMR, and HRMS. Interestingly, R1 upon interaction with various metal cations displays highly selective colorimetric and fluorescent turn-off response to Cu2+ ions. The UV–Vis absorption study of the R1 with Cu2+ ions exhibits a noticeable color change from yellow to brown color with a redshift (∼60 nm). Upon the addition of Cu2+ ions emission quenching at 529 nm was observed in R1, and the limit of detection (LOD) and limit of quantification (LOQ) were found to be 3.23 × 10−9 M and 10.79 × 10−9 M. The mechanisms of probe R1 for sensing Cu2+ ions have been well demonstrated by Job's plot, Benesi-Hildebrand studies, and Density functional theory calculations (DFT). Owing to practical application, the Cu2+ ions were efficiently determined using a spike and recovery approach from real water and vegetable extract samples. Further, the developed R1 sensors were used for test strips application to detect the Cu2+ ions and achieved naked-eye detection. Therefore, these investigated results demonstrate that sensor R1 has great potential to detect Cu2+ ions in environmental analysis systems.