Boric Acid‐Activated Room‐Temperature Phosphorescence and Thermally Activated Delayed Fluorescence for Efficient Solid‐State Photoluminescence Materials

The construction of highly luminescent solid-state materials with long-lived afterglow through a straightforward method is promising but still a challenging task. Herein, a heat-treatment strategy is proposed to embed levofloxacin (Lev) in the matrix of boric acid (BA) to produce a complex with a photoluminescence quantum yield of 63.8% and an emission lifetime of 0.74 s (afterglow: >5 s). Detailed investigations suggest that the unique photophysical properties of the complex are attributed to the confinement effect of BA matrix to Lev, which reduces the probability of nonradiative relaxation and activates the radiative decays to result in the promoted emission efficiency. In addition, thermally activated delayed fluorescence is also activated due to the alteration of the π transition of Lev by the formation of boron–carbon bonds. The emission color and lifetime are also modulated through controlling the synthetic conditions, which endow their applications both in light-emitting diodes and information encryption. Thus, the present results are significant for the construction of solid-state luminescent materials, including fluorescence and room-temperature phosphorescence, and also provide a solid and universal theory to clarify their detailed emission profiles.