Abstract: Carbon dots (CDs) have garnered significant attention from researchers both domestically and internationally as a novel type of persistent luminescent material. One major scientific challenge in this field is how to regulate the emission wavelength of carbon dot-based persistent luminescent materials. This paper presents a simple precursor molecular structure regulation strategy, carbon dot-based composites with phosphorescent emission colors covering the visible light spectrum were prepared through an in-situ calcination method using Al2O3 as a matrix and various small molecules as organic precursors. Transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy confirmed the successful growth of carbon dots within the Al2O3 matrix. Fluorescence spectroscopy tests indicated that the phosphorescent colors of the four CDs@Al2O3 composites were blue (454 nm), green (520 nm), orange (572 nm), and red (632 nm), with average lifetimes of 130.6 ms, 293.6 ms, 498.6 ms, and 539 ms, respectively. The observed redshift in phosphorescent emission wavelength, attributed to the decrease in the energy gap between the excited state and ground state of the carbon dots with increasing π-conjugation and number of oxygen-containing functional groups in the precursor, enables the modulation of multicolor phosphorescent emissions. Based on the multicolor room-temperature phosphorescent characteristics of this material, we preliminarily explored its applications in anti-counterfeiting and information encryption

Key words: Carbon dots, Room temperature phosphorescence, Long afterglow, Al₂O₃