A Ratiometric Fluorescent Detection Platform Using G-CDs@[Ru(bpy)3]2+ for the Specific Detection of Hypochlorite and Live Cell Imaging

Hypochlorite (ClO⁻), an essential reactive oxygen species (ROS) in physiological processes, is identified to be closely connected with oxidative stress and related diseases. Meanwhile, ClO⁻ is a commonly-used disinfector for water treatment, and in public places, under acidic conditions, it's easily decomposed into hypertoxic chlorine gas. Since the strong oxidizing property of ClO⁻, many oxidizing agents may disturb the ClO⁻ detection. Specific and accurate detection of ClO⁻ with superior sensitivity is a challenge. In this work, a sensing platform for rapid, sensitive, and specific ClO⁻ detection is constructed using green fluorescent carbon dots (G-CDs), with a linear detection range of 0.5–11 µm and a detection limit of 0.233 µm. Moreover, introducing a red fluorescent tripyridinium ruthenium ([Ru(bpy)₃]²⁺) as a reference, a ratiometric fluorescence nanoprobe G-CDs@[Ru(bpy)₃]²⁺ is prepared and shows favorable intracellular imaging of exogenous and endogenous ClO⁻. With G-CDs@[Ru(bpy)₃]²⁺-based test paper microarrays and a color recognition APP, a smartphone-based sensing system for point-of-care testing of ClO⁻ is also fabricated. In summary, this work proposed a versatile and economical smartphone-based sensing system that featured reliability and simplicity, and suggested its potential applications in environmental water quality monitoring and live cell imaging.