Abstract A new colorimetric sensor ‘R-IND’ based on isatin hydrazones have been designed and synthesized by simple Schiff base reaction. The anion sensing properties of R-IND were examined, characterized by common spectroscopic techniques such as Fourier Transform-Infrared (FT-IR), Ultraviolet–Visible (UV–Visible), Proton and Carbon Nuclear Magnetic Resonance (1H & 13C NMR), Electrospray Ionization Mass Spectroscopy (ESI-MS) and electrochemical studies. The sensor R-IND bearing ortho hydroxy group and amine group acting as binding sites. The sensor R-IND exhibited sensitive and selective sensing towards F− ion over the other competitive anions like Cl−, I−, Br−, H2PO4−, AcO−, CN–, NO3–, ClO4− and HSO4− in 100% Aetonitrile and 20% aqua Acetonitrile media. The bathochromic shift of 222 nm and 228 nm was observed in UV–Vis spectra with a color change from pale yellow to purple which is due to the complex formation between R-IND and F− ion through hydrogen bond formation. This was further accounted by 1H NMR titration. The Job’s plot reveals 1:2 stoichiometry between the host-guest complex. Binding and association constants were found to be 1.72 × 109 M−1, 2.82 × 109 M−1 and 6.0 × 105 M−1, 2.0 × 106 M−1 in 100% ACN and 20% aqua ACN respectively. The detection limit of sensor R-IND was turned out to be 0.45 and 0.41 ppm for F− ion in organic and aqua organic medium which is lesser than World Health Organization (WHO) permission level (1 ppm). The characteristic potential difference of 1.069 V has been observed for R-IND+F− complex in the electrochemical study. Finally, economically viable paper-based colorimetric test strips of R-IND were developed to detect the F− ions in 100% aqueous solution.

中文翻译：

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通过氢键形成基于靛红腙的氟离子比色“裸眼”传感器：通过核磁共振、紫外可见、计算和电化学研究确定的设计、合成和表征

摘要 通过简单的席夫碱反应设计并合成了一种基于靛红腙的新型比色传感器“R-IND”。通过傅里叶变换红外 (FT-IR)、紫外-可见 (UV-Visible)、质子和碳核磁共振 (1H & 13C NMR) 等常用光谱技术，研究了 R-IND 的阴离子传感特性，电喷雾电离质谱 (ESI-MS) 和电化学研究。带有作为结合位点的邻羟基和胺基的传感器 R-IND。传感器 R-IND 在 100% 乙腈中表现出对 F- 离子的敏感和选择性感应，而不是其他竞争性阴离子，如 Cl-、I-、Br-、H2PO4-、AcO-、CN-、NO3-、ClO4- 和 HSO4-和 20% 水性乙腈培养基。在 UV-Vis 光谱中观察到 222 nm 和 228 nm 的红移，颜色从淡黄色变为紫色，这是由于 R-IND 和 F− 离子之间通过氢键形成复合物形成的。1H NMR滴定进一步说明了这一点。乔布斯的情节揭示了主客体之间的 1:2 化学计量比。发现结合和缔合常数在 100% ACN 和 20% ACN 水中分别为 1.72 × 109 M-1、2.82 × 109 M-1 和 6.0 × 105 M-1、2.0 × 106 M-1。结果表明，传感器 R-IND 的检测限为 0.45 和 0.41 ppm，有机和水有机介质中的 F-离子低于世界卫生组织 (WHO) 的许可水平 (1 ppm)。在电化学研究中观察到 R-IND+F-复合物的特征电位差为 1.069 V。最后，