Changes in Fluorescence, Color, and Morphology of Fluorescent Nanostructures under Successive Light Irradiation

Fluorescence, color, and morphological changes of fluorescent nanostructures consisting of azobenzene-containing chromophores were investigated under successive visible light irradiation. Compared with spheres composed of a chromophore showing sufficient photoisomerization, fluorescent nanofibers assembled from a molecule showing a very small amount of photoisomerization had a slow response to light. Successive visible light irradiation of the nanofibers led to changes in fluorescence intensity and color, whereas the one-dimensional morphology was hardly affected. UV-visible absorption spectroscopy, optical microscopy (OM), scanning electron microscopy (SEM), and fluorescence optical microscopy (FOM) were employed to confirm the light-responsive properties. Our observations suggest that sufficient photoisomerization plays a key role in realizing fast and efficient light response of self-assembled structures.