Achieving high-stability aqueous room-temperature phosphorescent materials via in situ host–guest strategy

Abstract

Room temperature phosphorescence (RTP) materials hold great promise for applications in optoelectronic devices, bioimaging, and information security due to their unique luminescent properties. However, the presence of dissolved oxygen and molecular motion in aqueous environments often leads to phosphorescence quenching, which limits their practical development. Herein, we present a facile one-step in situ host–guest hydrothermal synthesis strategy, using cyanuric acid (CA), ethylenediamine, and cysteine as precursors to synthesize nitrogen–sulfur co-doped carbon dots and CA host–guest composite materials (NS-CDs₂₀@CA). The material exhibits phosphorescent emission characteristics in aqueous environments, with a phosphorescence quantum yield reaching 9.7%. Notably, it maintains high stability under extreme conditions such as strong acid/alkali, high-humidity environments, and elevated temperatures. Systematic analysis reveals the influence mechanisms of CA matrix and doping elements on RTP emission. The nitrogen–sulfur co-doped carbon dots and CA form a rigid hydrogen-bond network, effectively suppressing molecular motion and oxygen quenching, thereby stabilizing the triplet excited state. Meanwhile, nitrogen–sulfur doping promotes the intersystem crossing process, enhancing the singlet-to-triplet state transition and improving phosphorescence efficiency. Furthermore, we also demonstrate the potential application of NS-CDs₂₀@CA in multi-information encryption, providing new insights for the development of efficient and stable aqueous-phase RTP materials.