Turn-on Fluorescent Probes Based on Aggregation Enhanced Emission Characteristics for Hydroxyl Radical With Naked-Eye Recognition

Hydroxyl radicals (•OH), possessing extremely strong oxidative capability, play crucial roles in various fields. The detection of •OH is quite important but remains challenging. In this work, a series of quinoline-based fluorescent probes (F-1, F-2, F-3, and F-4) with aggregation enhanced emission (AEE) characteristics were designed and synthesized. All four probes exhibited pronounced turn-on fluorescence responses toward •OH with high selectivity and specificity, accompanied by distinct naked-eye recognition manifested as bright cyan fluorescence. Among them, probe F-4 showed the best sensing performance: upon the addition of 100 µM •OH, its fluorescence intensity increased by 4.77-fold, and the limit of detection was as low as 124 nM within a linear detection range of 10 to 100 µM. The mechanism of fluorescence enhancement may be attributed to the oxidation of the –CH₂OH group in the probes by •OH to form –CH₂CHO. Furthermore, a paper-based sensor was fabricated by simply depositing F-4 onto filter paper, enabling rapid naked-eye detection of •OH. This work provides a promising strategy for the development of novel AEE active fluorescent probes for •OH detection.