An imidazole-based fluorescent sensor for selective detection of Cu2+ and BF3 with environmental applications

Abstract

The selective and sensitive detection of Cu2+ and BF3 served as the foundation for the development of the unique dual sensing chemosensor, 2-(benzo[d]thiazol-2-yl)-6-(1,4,5-triphenyl-1H-imidazol-2-yl) phenol (SP26). SP26 was successfully synthesized in a multi-step synthesis reaction; NMR spectroscopy and HR-MS validated the identity of this compound. The experiments were carried out in 8:2 THF/water medium. The ligand was dissolved in THF/water and the salts of cations were dissolved in water. The absorption studies did not show sensing of any cations other than Cu2+. However, the emission experiments demonstrated that the optical selectivity towards the Cu2+ ion results in the quenching of emission intensity. Similarly, for BF3 the emission intensity decreases with bathochromic shift. The limit of detection (LoD) for Cu2+ is 381 pM, and for BF3 it is 307 pM. After adding BF3 and Cu2+ to SP26, the complex formation was so quick that it happened within a fraction of a second. Triethylamine (TEA) was used for BF3 and ethylenediamine tetraacetic acid (EDTA) for Cu2+ to determine the reversibility. The FT-IR, HR-MS, Job's plot, DFT, and 1H NMR titration analyses confirmed that chemosensor SP26 bound to Cu2+ and BF3. Paper test strips showed the potential of the chemosensor SP26 for environmental detection of Cu2+ and BF3. The quantitative analysis of Cu2+ was examined with the environmental water samples.