A Facile One‐Step Self‐Assembly Strategy for Novel Carbon Dots Supramolecular Crystals with Ultralong Phosphorescence Controlled by NH4+

Abstract

AbstractA 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 (ΔEST) 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+.