Fluorescent/Room Temperature Phosphorescent Carbon Dots Preparation And Its Information Encryption And Cellular Imaging

Activating long-lived room temperature phosphorescence（RTP）in the aqueous environment and thus realizing matrix-free,anti-oxygen,and time-resolved information encryption and cellular imaging remain a great challenge.Here,we fabricated three types of carbon dots（C-dots）,i.e.,fluorescent C-dots（F-C-dots）and two types of phosphorescent C-dots denoted as Pw-C-dots and Py-C-dots by a one-pot strategy.Their formation was attributed to the difference in the decarboxylation degree at high temperatures using trimesic acid（TMA）as a sole precursor.Unexpectedly,the yield reached as high as～92%,and the proportions were～27%for F-C-dots,～17%for Pw-C-dots,and～56%for Py-C-dots.These nanomaterials could help implement carbon peaking and carbon neutrality.Both green RTP of the two C-dots resulted from the small energy gap(ΔE_ST).These two RTP C-dots had a long lifetime of over 270 ms with a relatively high quantum yield（4.5%and 6.2%）.They exhibited excellent photostability and antiphotobleaching performances.The dry and wet powders of the RTP C-dots were applied to high-level information encryption.The lifelike patterns were greatly different from those of the original ones and could last for several seconds to the naked eye,demonstrating that the RTP C-dots could be potentially employed as anti-oxygen and time-resolved contrast reagents.Most significantly,the cellular imaging experiments showed that the biofriendly PVP-coated Py-C-dots could localize at lysosomes and sustain hundreds of milliseconds.This approach not only pioneers a time-resolved lysosome localization model but also opens up a promising door for anti-oxygen and time-resolved RTP cytoimaging.Due to the lacks of lysosome localization group and reaction/interaction site for hypochlorite（ClO^-）on the surface of the carbon dots（C-dots）,no C-dots-based lysosome-targeted fluorescence probes have,so far,been reported for real-time monitoring intracellular ClO^-.In this work,1,3,6-trinitropyrene（TNP）was used as a precursor to prepare C-dots with maximum excitation and emission wavelengths at 485and 532 nm,respectively,and quantum yield～27%by a hydrothermal approach at196°C for 6 h under a reductive atmosphere.The brightly green C-dots can sensitively and quickly respond to ClO^-in aqueous solution through surface chemical reaction,showing a linear relationship in the range of 0.5–120μМClO^-with 0.27μМof limit of detection（LOD）.Most significantly,the C-dots can localize at intracellular lysosome to image ClO^-in lysosomes.Also,the magnetic nanocomposites（C-dots@Fe₃O₄MNCs）were fabricated via a simple electrostatic self-assembly between Fe₃O₄magnetic nanoparticles（Fe₃O₄MNPs）and C-dots for highly efficient removal of ClO^-in real samples.Therefore,lysosome-targetable C-dots-based probes for real-time monitoring ClO^-were successful constructed,opening up a promising door to investigate the biological functions and pathological roles of ClO^-at organelle levels.