Facile synthesis of orange fluorescence multifunctional carbon dots for label-free detection of vitamin B12 and endogenous/exogenous peroxynitrite

In this work, orange emission fluorescent multifunctional carbon dots (O-CDs) were designed for the label-free detection of vitamin B12 (VB12)，endogenous/exogenous peroxynitrite (ONOO−) sensing, cell imaging, and fluorescent flexible film preparation. The O-CDs with excitation-independent were prepared using safranine T and ethanol as precursors via one-step hydrothermal process. VB12 was utilized as a quencher to quench the fluorescence of O-CDs due to the internal filtration effect (IFE). Two-segment linear ranges are 1–65 μM and 70–140 μM, and the detection limit was calculated as 0.62 μM. Besides, ONOO− can reduce the fluorescence intensity of O-CDs based on static quenching (SQ). The linear ranges are 0.3–9 μM and 9–48 μM, and the detection limit was 0.06 μM. Moreover, the O-CDs were exploited as a cellular imaging reagent for intracellular VB12 and endogenous/exogenous ONOO− imaging owing to its great biocompatibility, low toxicity and strong photostability. These results indicate that O-CDs have the potential to be used as a sensitive fluorescence probe to rapidly monitor VB12 and endogenous/exogenous ONOO− with high selectivity in living cells. Also, the as-proposed O-CDs can be employed to fabricate O-CDs/PVA composites as fluorescent flexible films. All of the above prove that the O-CDs present great prospect in multiple applications such as biosensing, cellular labeling, biomedical optical imaging, and fluorescent films.