Morphological patterns of controlled particle dispersion by photoisomerization of spiropyrans

Abstract

This work describes an interesting morphological control of the microstructures of photoactive spiropyrans. These microstructures exhibit reversible photoisomerization in solid state under different light irradiation. To observe morphological changes intuitively caused by volume expansion of spiropyrans, a special film is synthesized with inverse conical-hole structures by biomimetic method. When a drop of spiropyran-silica mixture ethanol suspension is placed on the film and dried naturally, almost all spiropyran-silica mixture particles gather into inverse conical holes of the film. Then mixture particles in holes start distributing on edge areas of holes on the film under illumination of 365nm UV light, spread evenly on the whole surface of the film, and finally convert into self-assembled structures. In addition, particle state can recover to its original state, when irradiate with visible light.