Pressure/Thermo-Induced Hypsochromic-Shifted and Enhanced Luminescence Based on Carbazole Emitter

Most organic mechanochromic luminogens show bathochromic-shifted and quenched emission with increasing pressure. Design of turn-on mechanochromic material with hypsochromic-shifted luminescence is still a challenge. Herein, a novel emitter (namely DCzPy) was prepared through laboratory-synthesized carbazole to study its stimuli-responsive luminescence. The crystalline powders of DCzPy emitted blue-green fluorescence at 490 nm. Upon gently grinding, the fluorescence intensity of DCzPy was dramatically enhanced with a hypsochromic shift by 33 nm. Further heavily grinding, its emission wavelength returned to 490 nm. Powder X-ray diffraction patterns indicated that such behaviors were attributed to the solid-state morphology transition from crystal to crystal. Interestingly, a large bathochromic-shifted and weakened fluorescence was achieved under isotropic compression. Moreover, thermoresponsive behavior of DCzPy was studied in the film to find that its emission turned from green to blue as the temperature increased. Given the thermo-induced fluorescence switching of DCzPy, a two-dimensional code was fabricated for information anticounterfeiting.