Abstract Herein, we report the fluoride anion sensing properties of a commercially available and inexpensive organic compound, isatin, which is found to be a highly selective and sensitive sensor. In naked-eye experiments, by addition of fluoride anions, isatin shows a dramatic color change from pale yellow to violet at room temperature, while the addition of other anions, i.e. C l − , $\mathrm{Cl}^-,$ B r − , I − , C l O 4 − , H 2 P O 4 − a n d P F 6 − , $\mathrm{Br}^-,\mathrm I^-,\mathrm{ClO}_4^-,{\mathrm H}_2\mathrm{PO}_4^-\,\mathrm{and}\,\mathrm{PF}_6^-,$did not induce any colour change. Additionally, recognition and titration studies have also been done through UV/Vis spectroscopy. Isatin displayed a new absorption band at 533 nm after the addition of fluoride anions, which is presumably due to acid-base interaction between isatin and fluoride anions, while other anions did not trigger noticeable spectral changes. The detection limit was observed to be 0.367 ppm. DFT calculations were also performed to further explain the behavior of receptor 1 towards the Fˉ anion. Owing to high sensitivity and selectivity, isatin can be useful in the detection of biologically or environmentally important fluoride anions at very low concentration.

中文翻译：

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靛红作为一种简单、高选择性和灵敏的氟阴离子比色传感器

摘要在此，我们报告了市售且廉价的有机化合物靛红的氟阴离子传感特性，该化合物被发现是一种高度选择性和灵敏的传感器。在肉眼实验中，通过添加氟阴离子，靛红在室温下呈现出由淡黄色到紫色的剧烈颜色变化，而添加其他阴离子，即Cl - , $\mathrm{Cl}^-, $ B r - , I - , C l O 4 - , H 2 PO 4 - 和 PF 6 - , $\mathrm{Br}^-,\mathrm I^-,\mathrm{ClO}_4^-,{\mathrm H }_2\mathrm{PO}_4^-\,\mathrm{and}\,\mathrm{PF}_6^-,$没有引起任何颜色变化。此外，还通过紫外/可见光谱进行了识别和滴定研究。添加氟阴离子后，靛红在 533 nm 处显示出新的吸收带，这可能是由于靛红和氟阴离子之间的酸碱相互作用，而其他阴离子没有引发明显的光谱变化。观察到的检测限为 0.367 ppm。还进行了 DFT 计算以进一步解释受体 1 对 Fˉ 阴离子的行为。由于高灵敏度和选择性，靛红可用于检测非常低浓度的生物或环境重要的氟阴离子。