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, 1 H 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.
Xiangdong Ji,Pengji Yan,Wenqin Yang,Yujiao Peng,Cheng Cao
Two new colorimetric receptors 1 and 2 nitrophenyl as signaling units and imine moieties as binding sites were synthesized via a simple condensation reaction and characterized by 1H NMR, 13C NMR, FTIR, and HRMS. The colorimetric sensing properties of the receptors toward various anions were studied using naked eye detection, UV-vis spectroscopy, and 1H NMR titration. The results show that receptors 1 and 2 exhibit good UV-Vis recognition capabilities for F−, Ac−, and CN−, and can recognize CN− with the naked-eye in a H2O/DMSO (3:7, V/V) solution. The detection limit for CN− recognition by receptors 1 and 2 was as low as 1.31 µmol, and we prepared test papers for detecting anions using these receptors. The Job's plot analysis demonstrates a 1:1 stoichiometric binding ratio between F− and the receptors. The recognition mechanism of CN− was inferred using UV-vis and 1H NMR titrations, HRMS, and theoretical calculations. Such stripes can serve as a practicable colorimetric probe for the detection of ions in many fields and avoid more expensive equipment.
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