7,7,8,8-Tetracyanoquinodimethane (TCNQ) emits visible photoluminescence in solution

7,7,8,8-Tetracyanoquinodimethane (TCNQ) has been used as a versatile building block for designing organic conductors and assemblies. It is believed that the fluorescence quantum yield of TCNQ is extremely low and it does not show observable fluorescence. Here we report, contrary to the conventional beliefs, that TCNQ emits blue photoluminescence in nonpolar solution. The photoluminescence intensity acutely decreases with increasing solvent polarity. Our findings will facilitate the design of TCNQ-based materials for applications in optoelectronics and polarity sensors.