Add time:08/07/2019         Source:sciencedirect.com

A novel fluorescent and colorimetric dual mode molecular probe based on fluorene derivatives, N-(9H-fluoren-2-yl)-5H-cyclopenta [2,1-b:3,4-b']dipyridin-5-imine (FCD), was synthesized and characterized by elemental analysis, FT-IR, 1HNMR, and 13CNMR techniques. The optical properties of the probe in detection of iodide anion was studied both experimentally and computationally. The probe shows excellent selectivity and sensitivity by fluorescence quenching toward iodide over other anions in THF. Since the response is presented via color changing, it is clearly observable by the naked eye. The signal quenching of sensor at λ = 365 nm is based on the intermolecular CT transitions from iodine to FCD with the inhibition of reverse π→π* charge transition at the probe. The limit of detection for I¯ was obtained as 2.7 × 10−8 M and 4.3 × 10-7 M for fluorescence and UV–vis techniques respectively. In addition, DFT and TDDFT calculations were performed to determine the interaction between the probe and the target as well as the quenching and color changing mechanisms. Further tests in the presence of thiosulfate ions, as well as TDDFT calculations were carried out to determine the mechanism. It was found that both color changing and fluorescence quenching are the results of iodine formation.

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