Gram-scale synthesis of carbon dots-based full-color tunable afterglow composites by a one-step and solvent-free method

Multicolor afterglow carbon dots (CDs) have significant application potential in information encryption, anti-counterfeiting, and optoelectronics. However, achieving afterglow CDs with a high quantum yield (QY) across the visible spectrum using a one-step, solvent-free route on a large scale remains a formidable challenge. In this work, a series of CDs-based composites with tunable full-color afterglow (454–602 nm), high QY (30.4–20.6 %), long lifetime (169–416 ms) and high production yield (64–78 %) were successfully synthesized on a gram scale by thermally heating a solid mixture of boric acid (BA), salicylic acid, acrylamide, and rhodamine B (RhB). Comprehensive characterizations revealed that the blue-to-green afterglow originates from room-temperature phosphorescence (RTP) activated by the B 2 O 3 matrix and that emission tunability is attributed to the quantum size effect. Furthermore, the yellow-to-red tunable afterglow, belonging to delayed fluorescence (DF), results from in situ Förster resonance energy transfer (FRET) between the phosphorescent CDs and the increasing content of rhodamine B moieties anchored on the CD surfaces. This work demonstrates an efficient and environmentally friendly synthesis strategy for producing full-color afterglow CDs on the gram scale and highlights their promising applications in anti-counterfeiting, information encryption, and organic optoelectronic devices.