Unusual phosphorescence of boric acid:From impurity or clusterization-triggered emission?

The unusual room-temperature phosphorescence(RTP)from the n electron-rich systems(without regular conjugated structure)has aroused great attention for structural designing and application development of RTP materials.Such emission has been ascribed to clusterization-triggered emission(CTE)via weak through-space conjugation of n electrons in the heteroatoms.However,there was suspicion on such RTP as impurity-induced result.Therefore,in-depth photophysical investigation and effective proof methods are needed to trace the origin of such RTP.Here,using the recently reported CTE phosphor boric acid as the example,a Jablonski diagram-based verification protocol was proposed to confirm the intrinsic luminescence of the n electrons-rich systems.Meanwhile,some other types of luminophores,that is,traditional phosphors,already reported impurity-induced and host-guest doping luminophores,were included for comparison.Overall,this work provides a basic paradigm for differentiating between the impurity-involved and the n electron-rich phosphors and will further deepen the understanding of nonconventional luminescence.