Crystalline <i>o</i>‑Carborane Derivatives\nas a Fluorescence Turning-On Probe for Acid Environments

Fluorescence from <i>o</i>-carborane derivatives\nis usually\nweak in solution due to the robust nonradiative decay via the motion\nof bond rotation, but it is enhanced in the aggregated states, which\nis also known as aggregation-induced emission. To the best of our\nknowledge, there is no other way to significantly enhance the fluorescence\nintensity of <i>o</i>-carborane derivatives in the reported\nliterature. Also, novel strategies and sensing materials for gaseous\nacid detection are in high demand due to the aspects of high sensitivity,\neasy operation, and low cost. Herein, we report the effective fluorescence\nturning-on phenomenon of crystalline <i>o</i>-carborane\nderivatives upon exposure to acidic gas, which shows that crystalline <i>o</i>-carborane derivatives can function as effective sensors\nfor acidic environments.