Regulation of Conjugation Degree and Nitrogen Doping in Dual‐Confined Carbon Dots Enables Full‐Color‐Tunable Long‐Persistence Room Temperature Phosphorescence

Abstract Long‐persistence room temperature phosphorescent (RTP) materials have extensive applications in advanced information encryption, anti‐counterfeiting, and optoelectronic devices. Carbon dots (CDs), as an emerging nano‐luminescent material, are promising candidates for long‐persistence RTP due to their superior optical properties, low cost, minimal toxicity, and high stability. In this study, full‐color, long‐persistence phosphorescent materials are developed via a simple one‐step hydrothermal method using p‐hydroxybenzoic acid (p‐HBA) as a precursor, by reacting with aromatic amines with different degrees of conjugation (o‐phenylenediamine, 9,10‐diaminophenanthrene, 1,8‐diaminonaphthalene, and 1‐aminopyrene). This approach achieves phosphorescence spanning a wavelength range from 432 to 601 nm, in which the longest RTP lifetime is 2.8 s and up to 23 s in the naked eye, without the need for organic materials using fluorescence resonance energy transfer. This is accomplished by modulating the graphite‐N content and degree of conjugation of the CDs, as well as leveraging the dual‐confinement of the B₂O₃ matrix. These materials exhibit robust long‐persistence phosphorescence stability at room temperature in both organic solvents and cyclic excitation. Based on the excellent constant RTP performance and cyclic stability of the four composites, they can be widely used in advanced information encryption, anti‐counterfeiting, and ASCII code information storage practical applications.