Unprecedented and Readily Tunable Photoluminescence from Aliphatic Quaternary Ammonium Salts

Compounds bearing aliphatic amines could be emissive under proper conditions. Their ionized counterparts, quaternary ammonium salts (QASs), which are widely used as phase-transfer catalysts, ionic liquids, disinfectants and surfactants, however, are known as luminescence quenchers and thought to be nonemissive. Here we report the unprecedented intrinsic fluorescence-phosphorescence dual emission from a diversity of QASs, which can also be finely regulated by excitation wavelength, alkyl chain length, counter ions, mechanical stimuli, etc. The bright photoluminescence along with distinct afterglow and tunable multicolor emissions enables advanced multimode anticounterfeiting for QAS solids. This finding refreshes the cognition of QASs and would inspire emerging applications by utilizing their intrinsic luminescence. Furthermore, it opens opportunities for the investigation of QAS related processes and functions in a photophysical approach and affords strong implications for the fabrication of novel nonconventional luminophores.