A Facile One-Step Self-Assembly Strategy for Novel Carbon Dots Supramolecular Crystals with Ultralong Phosphorescence...

A new methodological design is proposed for carbon dots (CDs)-based crystallization-induced phosphorescence (CIP) materials via one-step self-assembled packaging controlled by NH₄ ⁺. O-phenylenediamine (o-PD) as a nitrogen/carbon source and the ammonium salts as oxidants are used to obtain CDs supramolecular crystals with a well-defined staircase-like morphology, pink fluorescence and ultralong green room-temperature phosphorescence (RTP) (733.56 ms) that is the first highest value for CDs-based CIP materials using pure nitrogen/carbon source by one-step packaging. Wherein, NH₄ ⁺ and o-PD-derived oxidative polymers are prerequisites for self-assembled crystallization so as to receive the ultralong RTP. Density functional theory calculation indicates that NH₄ ⁺ tends to anchor to the dimer on the surface state of CDs and guides CDs to cross-arrange in an X-type stacking mode, leading to the spatially separated frontier orbitals and the through-space charge transfer (TSCT) excited state in turn. Such a self-assembled mode contributes to both the small singlet-triplet energy gap (ΔE_ST) and the fast inter-system crossing (ISC) process that is directly related to ultralong RTP. This work not only proposes a new strategy to prepare CDs-based CIP materials in one step but also reveals the potential for the self-assembled behavior controlled by NH₄ ⁺.