Enhanced emission and two-photon absorption cross-section by nanoaggregation of a cyano-substituted stilbene...

This study reports the synthesis and the investigation of optical behaviors of a stilbene derivative, (Z)-2,3-bis[4-(N-4-(diphenylamino)styryl)phenyl]acrylonitrile (StCN). The nanoaggregates of StCN in 50% water/DMF have exhibit an increased fluorescence intensity and a blue shift with emission maximum wavelength with respect to StCN in 100% N, N-dimethylformamide (DMF) solution. This fluorescence enhancement can be attributed to the formation of J-aggregates. The cyano group prevents coplanarization of both arms and intermolecular face-to-face orientation leading to the formation of J-aggregates preventing the solvent relaxation. A strong fluorescence bathochromic solvatochromism is indicative of a large dipole moment in solution. Also, the two-photon absorption cross-section of nanoaggregates has been increased 1.5 times compared to that in DMF solution at the maximum wavelength.