Triggering triplet excitons of carbon nanodots through nanospace domain confinement for multicolor phosphorescence in aqueous solution

Easy non-radiative decay property of long-lived triplet excitons in aqueous solution obstructs their applications in aquatic surroundings. Recently reported phosphorescence phenomena in aqueous solution have excited researchers enormously but achieving full-color water-soluble phosphorescent carbon nanodots (CNDs) is still a challenging issue. Herein, full-color phosphorescence of water-soluble CNDs has been demonstrated by triggering their triplet excitons through nanospace domain confinement, and Förster energy resonance transfer is used for further tuning phosphorescence range. The phosphorescence spans across most of the visible spectrum, ranging from 400 to 700 nm. In an aqueous solution, the CNDs exhibits blue, green, and red phosphorescence, lasting for approximately 6, 10, and 7 s, respectively. Correspondingly, the phosphorescence quantum yields are 11.85%, 8.6% and 3.56%, making them readily discernible to the naked eyes and laying a solid foundation for practical application. Furthermore, phosphorescence flexible optical display and bioimaging have been demonstrated by using the multicolor CNDs-based nanomaterials, showing distinct superiority for accuracy and complete display and imaging in complex emission background.