Unusual Spectral Change Due to a Cyanine Dye Adsorbed on an Inorganic Layered Material upon Photoirradiation

Photoinduced spectral change can be utilized for various optical devices. The photoinduced spectral change due to an organic dye was demonstrated for the organic-inorganic hybrid film without the aid of photochromism with a simple preparation method for the first time. By the hybridization of a cyanine dye of 2-[5-(1,3-dihydro-3,3-dimethyl-1-octadecyl-2H-indol-2-ylidene)-1,3-pentadienyl]-3,3-dimethyl-1-octadecyl-3H-indolium perchlorate (NK3175) with an inorganic layered material of cation-exchangeable clay, smectite (SWN), a spectral change attributed to NK3175 was generated upon the irradiation of UV light. This result might serve as useful information on the methodology to produce optically controlled function for photoresponsive systems. Furthermore, the hybrid film of SWN and NK3175 was characterized by the use of XRD and FT-IR measurements. NK3175 molecules adsorbed onto external surfaces of SWN were confined by oriented SWN. It was suggested that the enhanced intermolecular interaction between NK3175 molecules caused by the hybridization with SWN resulted in the change of the aggregation state of NK3175 upon the UV light irradiation, which accounts for the spectral change of NK3175.