A novel “turn on” fluorescent and colorimetric ICT-based sensor for the detection of fluoride and cyanide ions

Abstract

A novel sensor (Sensor 2) containing a fluorescent core of aromatic naphthalene and a binding site of aminothiourea group has been synthesized and systematically investigated with regard to anions recognition. The results indicate that Sensor 2 shows fast response, high selectivity and sensitivity and reversibility to detect fluoride (F⁻) and cyanide (CN⁻). Adding F⁻/CN⁻ into DMSO solution of Sensor 2 induces a distinct color change from colorless to yellow under ambient light and from blue to greenish-blue under 365 nm UV light. Besides, Sensor 2 can distinguish F⁻ from CN⁻ by fluorescent spectra based on the different sensitivities of Sensor 2 to F⁻ and CN⁻, as well as “turn on” at the different emission wavelengths. The sensing mechanism has been proposed and verified by ESI-MS, ¹H NMR titration, DFT and TD-DFT calculations, which refers to the interaction of Sensor 2 with F⁻ and CN⁻ via forming hydrogen bond and subsequent deprotonation. The reversibility of Sensor 2 was also studied, confirming that it is a reusable sensor. In addition, the preliminary application of Sensor 2 for the detection of fluoride in toothpaste was successful.