A ratiometric fluorescent probe with 1,2,4-triazole recognition unit for fluoride ion detection based on synchronous fluorescence spectroscopy

Abstract

As an important inorganic chemical with wide applications and high toxicity, the detection of fluoride-containing products and environmental samples has gained the most interest. In this work, a ratiometric fluorescent probe (NIN2) is constructed with a triazole group as the new recognition site for the detection of F−. The synchronous fluorescence technology was introduced to obtain the well discrimination of two emission bands. The value of wavelength intervals (Δλ = λem. - λex.) is optimized to be set as 70 nm with the minimized overlap of two emission bands centered around 380 nm and 470 nm, respectively. In this way, NIN2 can detect F− in the region of 0–0.2 μM with a good linear relationship (R2 = 0.9989) and low LOD value (36 nM). Only F− can induce obvious ratiometric response (I470nm/I380nm) from 0.2 to 3.4 while the ratios of the samples containing other cations and anions are as low as the blank sample. For investigating the recognition mechanism of triazole, 1H, 13C and 19F NMR spectral technologies were used to verify the interaction between triazole and F−. Furthermore, the DFT calculation was also performed to discuss the electronic transition of NIN2 before and after interaction with F−. We believe this work provides a new recognition moiety for detecting F−.