Molecular dual-functionalization unlocks room-temperature phosphorescence of graphitic carbon nitride for environmentally robust encryption

Abstract

Organic room-temperature phosphorescence (RTP) materials often suffer from thermal degradation, thermal quenching, susceptibility to solvent dissolution and oxidation–reduction, which collectively hinder their practical application in encryption under diverse and demanding environments. Here we report a naphthyl–phenyl dual-functionalized graphitic carbon nitride (g-CN) material that exhibits robust RTP properties. The incorporation of phenyl groups enhances the structural rigidity of the g-CN and effectively suppresses non-radiative decay pathways. Concurrently, naphthyl functionalization facilitates efficient intersystem crossing from singlet to triplet states by strengthening spin–orbit coupling. This synergistic molecular design promotes the efficient generation and radiative recombination of triplet excitons, resulting in a bright yellow afterglow lasting up to 4 seconds. The dual-functionalized g-CN material maintains stable RTP performance at elevated temperatures and in the presence of various solvents, demonstrating great potential for advanced information encryption applications under complex and harsh environmental conditions.