Strategy to synthesize dual-emission carbon dots and their application for pH variation and hydrogen sulfide sensing...

In this work, dual emission nitrogen and sulfur co-doped fluorescent carbon dots (DE-CDs) were designed for pH variation and hydrogen sulfide (H₂S) sensing and bioimaging through fluorescence enhancement. The DE-CDs with green-orange emission were facilely prepared by one-pot hydrothermal strategy using neutral red and sodium 1,4-dinitrobenzene sulfonate as precursors, manifesting intriguing dual-emission behavior at 502 and 562 nm. As the pH increases from 2.0 to 10.2, the fluorescence of DE-CDs gradually increases. The linear ranges are 2.0-3.0 and 5.4-9.6, respectively, which are attributed to the abundant amino groups on the surface of the DE-CDs. Meanwhile, H₂S can be employed as an enhancer to increase the fluorescence of DE-CDs. The linear range is 25-500 μM, and the LOD is calculated to be 9.7 μM. Besides, the DE-CDs can be used as imaging agents for pH variation and H₂S sensing in living cells and zebrafish due to their low toxicity and good biocompatibility. All of the results demonstrated that the DE-CDs can monitor pH fluctuations and H₂S in aqueous and biological environments, and have promising applications in the fields of fluorescence sensing, disease detection, and bioimaging.