Selective Determination of HOCl in Environmental Water Samples and Real-Time Detection of HOCl Levels in Live Cells via Ratio Fluorescence Imaging Based on Eu3+-Modified and Carbon Dot-Encapsulated Metal Organic Frameworks.

Hypochlorous acid (HOCl) is one kind of significant ROS and a typical environmental pollution, which is closely linked to our food chain and threatens human health. Hence, a dual-emission ratiometric fluorescent nanoprobe (N-CDs@Eu-UiO-66-(COOH)₂) for sensitive and specific determination of HOCl was fabricated based on Eu³⁺-modified and carbon dot-encapsulated MOFs. The N-CDs were encapsulated into MOFs, which can greatly improve their photostability and resistance to photobleaching in aqueous solution. The N-CDs@UiO-66-(COOH)₂ was modified by Eu³⁺ ions, which can emit the red characteristic fluorescence of Eu³⁺ ions via the antenna effect. HOCl can quench the fluorescence of N-CDs through oxidizing hydroxyl groups on its surface, while the characteristic fluorescence of Eu³⁺ remains unchanged. The ratiometric fluorescence nanoprobe of N-CDs@Eu-UiO-66-(COOH)₂ was thus fabricated for detecting HOCl. The nanoprobe has high sensitivity and selectivity, and its LOD (3σ/K) can attain 15.0 nM. Moreover, the N-CDs@Eu-UiO-66-(COOH)₂ nanoprobe can also be applied for real-time detection of HOCl levels in the live cells via ratio fluorescence imaging, which can serve as a noninvasive tool for sensitively detecting fluctuations of HOCl levels in the living cells. This work can provide a promising application in environmental monitoring and real-time monitoring HOCl levels in vivo. [ABSTRACT FROM AUTHOR]