Precise Electron-Withdrawing Strength Modulation of ESIPT Probes for Ultrasensitive and Specific Fluorescence Sensing
Yanwen Guo, Zhenzhen Cai, Fei Yan, Da Lei, Yanan Guo, Shuhai Zhang, Xincun Dou
Abstract
The precise regulation of the electron-withdrawing/electron-donating strength in a probe is of great significance for the design of reaction-based fluorescent probes with specific functionalities. Here, a family of excited-state intramolecular proton transfer (ESIPT)-based probes with fluorescence turn-on sensing properties toward KMnO 4 was designed by precisely modulating the electron-withdrawing strength of the substituents located at the para -position of the recognition group. It is found that −F, −CHO, and −H as the electron-withdrawing groups bound at the probe can specifically recognize KMnO 4, which ensures a blue emission displayed by the reaction products. Especially with −CHO as the electron-withdrawing group, the reaction product shows the most stable fluorescence. The probe 2-(benzo[ d ]oxazol-2-yl)-4-formylphenyl acrylate (BOPA-CHO) demonstrated a more superior sensing performance toward KMnO 4, including a low limit of detection (LOD, 0.96 nM), a rapid response (<3 s), and a rather good selectivity even in the presence of 21 interferents. Moreover, the practicality of the probe was further verified by a test pen comprising a BOPA-CHO-embedded sponge, which is capable of detecting KMnO 4 solid with a naked-eye LOD of 11.62 ng. The present probe design and modulation strategy would open up a new path for the design of high-performance fluorescent probes.