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

Abstract

The specific detection of Cu²⁺ and BF₃ provided the basis for the design of the distinctive dual-sensing chemosensor, 2-(benzo[d]thiazol-2-yl)-6-(1,4,5-triphenyl-1H-imidazol-2-yl) phenol (SP26). SP26 was synthesized successfully using a multi-step process, with its identity confirmed by NMR spectroscopy and HR-MS analysis. The studies were conducted in an 8 : 2 THF/water mixture. The ligand was solubilized in THF/water, whereas the cation salts were dissolved in water. The absorption measurements indicated no detection of cations other than Cu²⁺. The emission experiments revealed that the optical selectivity for the Cu²⁺ ion leads to a reduction in emission intensity. Likewise, with BF₃, the emission intensity diminishes with the 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. FT-IR, HR-MS, Job's plot, DFT, and ¹H NMR titration analyses confirmed that chemosensor SP26 was bound to Cu²⁺ and BF₃. Paper test strips showed the potential of the chemosensor SP26 for the environmental detection of Cu²⁺ and BF₃. The quantitative analysis of Cu²⁺ was examined with environmental water samples.