Highly Oriented J-Aggregates of Nitroazo Dye and Its Surface-Induced Chromism

Highly oriented J-aggregates of a nitroazo dye were obtained in solid thin films on aligned poly(tetrafluoroethylene) surfaces. During film deposition on a friction-transferred poly(tetrafluoroethylene) layer, a sharp peak grew in the polarized absorption spectra around 613 nm, which was red-shifted 117 nm from the peak in dilute dichloromethane solution. The peak showed remarkable optical anisotropy: dichroic ratios D of up to 22 were observed, and the intrinsic D value should substantially exceed this value. These results indicate that the peak is attributable to highly oriented J-aggregates. On glass, however, H-like aggregates grew, exhibiting an absorption peak at 410 nm. Hence, the substrate surface induced the remarkable chromism observed as a 203 nm red shift.