pH response of inverse opal photonic crystal gel

In this paper, we focus in the pH response of inverse opal photonic crystal gel. First, a series of monodispersed submicrometer silicon particles was prepared by Stöber method. Then, these particles were self-assembled into three dimensional (3D) ordered colloidal crystal film in vivid color using vertical deposition method. Sequentially, methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) were copolymerized in the interspace of the silica 3D photonic crystal template. After the silica particles were etched by HF, 3D inverse opal photonic crystal hydrogels with highly ordered interconnected pores were obtained. The resultant inverse opal hydrogel shifted the reflection from 514 nm to 590 nm as pH value increased from 5 to 8. The structural color changed from blue-green to red within an equilibrium time of less than 2 min.