Centre for Research in Functional Materials (CRFM), JAIN (Deemed-to-be University), Jain Global Campus, Bengaluru 562112, India.
Centre for Nano and Material Sciences, JAIN (Deemed-to-be University), Jain Global Campus, Bengaluru 562112, India.
Anal Methods. 2023 Jul 6;15(26):3259-3267. doi: 10.1039/d3ay00541k.
A Schiff base receptor with an active -NH group was designed and synthesized for the selective and sensitive colorimetric detection of inorganic fluoride (F) ions in an aqueous medium. The sensitivity of the receptor for F ions was enhanced by the influence of two electron-withdrawing -NO groups at ortho and para positions which result in a vivid color change. The receptor underwent a remarkable color change from light yellow to violet, enabling naked-eye detection of F ions without the need for spectroscopic equipment. To ensure the structural integrity of the synthesized receptors, prominent spectroscopic techniques such as H NMR, FTIR, and GCMS analysis were used for characterization. With a limit of detection (LoD) of 0.0996 ppm, a 1 : 2 stoichiometric binding ratio was observed for receptor and F ions. The binding mechanism confirmed the deprotonation of the -NH group followed by the formation of -HF, resulting in an intramolecular charge transfer (ICT) transition, which correlates with UV-vis and H NMR titration results. In addition, the proposed binding mechanism of F ion interaction with the receptor was theoretically validated using DFT and TDDFT calculations. Furthermore, as a real-life implementation of the receptor, quantification of the F ions present in a commercially available mouthwash was demonstrated. To assess the sensitivity performance, a paper-based dip sensor and a solid substrate sensor by functionalizing the receptor on diatomaceous earth were demonstrated. Finally, sensors were built into smartphones that could recognize the red, green, and blue percentages (RGB%) where each parameter defines the intensity of the color, which could also be used as a supplement to the colorimetric investigations.
设计并合成了一种具有活泼 -NH 基团的席夫碱受体，用于在水相介质中选择性和灵敏地比色检测无机氟离子 (F)。两个吸电子 -NO 基团在邻位和对位的影响增强了受体对 F 离子的灵敏度，导致明显的颜色变化。受体从浅黄色变为紫色，发生显著的颜色变化，无需光谱设备即可进行肉眼检测 F 离子。为了确保合成受体的结构完整性，使用了突出的光谱技术，如 H NMR、FTIR 和 GCMS 分析进行表征。受体与 F 离子的结合比为 1：2，检测限 (LoD) 为 0.0996 ppm。结合机制证实了 -NH 基团的去质子化，随后形成 -HF，导致分子内电荷转移 (ICT) 跃迁，这与紫外可见和 H NMR 滴定结果相关。此外，使用 DFT 和 TDDFT 计算对 F 离子与受体相互作用的结合机制进行了理论验证。此外，作为受体的实际应用，证明了在市售漱口水中存在的 F 离子的定量。为了评估灵敏度性能，展示了通过在硅藻土上功能化受体构建的纸基浸液传感器和固体基质传感器。最后，将传感器集成到智能手机中，可以识别红色、绿色和蓝色百分比 (RGB%)，每个参数定义颜色的强度，也可以作为比色研究的补充。
