Multicolor room-temperature phosphorescent carbon dots for information encryption prepared by modifying the amino substitution sites of precursors.

Carbon dots (CDs), an emerging class of carbon-based nanophosphors, have been regarded as ideal candidates for realizing long-afterglow room-temperature phosphorescence (RTP) owing to their exceptional optical properties, low cost, low toxicity, and high stability. In this study, three room-temperature phosphorescent carbon-dot composites were prepared through a one-step hydrothermal method using boric acid (BA) and biphenyldiamine isomers as precursors. By modulating the amino-substitution pattern, the electronic structures and triplet-state energy levels of the emissive centers were effectively regulated, thereby promoting the intersystem crossing (ISC) and stabilizing the triplet excitons, thereby enabling color-tunable phosphorescence. This strategy enabled phosphorescence emission within the wavelength range of 460-520 nm, with the longest phosphorescence lifetime reaching 3.04 s and a maximum phosphorescence quantum yield of 50.91%. These CDs exhibited stable phosphorescent performance at room temperature. Therefore, they show considerable potential for applications in advanced information encryption and anti-counterfeiting.