A facile synthetic route to realize RGB full-color ultralong afterglow and triple-mode emissions in carbon-dot-based anti-counterfeiting inks was developed herein.

The first carbon dot (CD)-based organic long persistent luminescence (OLPL) system exhibiting more than 1 h of duration was developed. In contrast to the established OLPL systems, herein, the reported CDs-based system (named m-CDs@CA) can be facilely and effectively fabricated using a household microwave oven, and more impressively, its LPL can be observed under ambient conditions and even in aqueous media. XRD and TEM characterizations, afterglow decay, time-resolved spectroscopy, and ESR analysis were performed, showing the successful composition of CDs and CA, the formation of exciplexes and long-lived charged-separated states. Further studies suggest that the production of covalent bonds between CA and CDs plays pivotal roles in activating LPL and preventing its quenching from oxygen and water. To the best of our knowledge, this is a very rare example of an OLPL system that exhibits hour-level afterglow under ambient conditions. Finally, applications of m-CDs@CA in glow-in-the-dark paints for emergency signs and multicolored luminous pearls were preliminarily demonstrated. This work may provide new insights for the development of rare-earth-free and robust OLPL materials.

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Quantum dot color conversion films (QD-CCFs) are proposed for use in full-color micron-sized light-emitting diode (micro-LED) displays, but quickly and precisely evaluating their optical quality and identifying the bad pixels among them remain challenging. In this work, microscale fluorescence spectroscopy (MFS) is demonstrated to investigate the photoluminescence uniformity and stability of red-emitting CdSe/CdS/ZnS QD-CCF pixels prepared by high-resolution inkjet printing. The photoluminescence (PL) intensity imaging, together with the PL spectrum, lifetime imaging, and time-dependent PL intensity curve, enables accurate analysis of the luminescence uniformity and thermal and light stability of QD-CCFs. The coffee rings in QD-CCF pixels can be clearly identified by MFS, which are missed by a conventional fluorescence microscope. It thus provides feedback for tailoring the composition and properties of ink to eliminate coffee rings or other defects. The combination of MFS with machine learning will likely realize the "massive detection" of QD-CCFs for micro-LEDs.

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