Photonic crystals with thermally switchable stop bands fabricated from Se@Ag₂Se spherical colloids

(Figure Presented) Amorphous Se (a-Se) as monodispersed spherical colloids are used as templates to synthesize core-shell particles comprising a-Se cores and Ag₂Se shells (see picture). As the temperature is increased, the particles undergo two phase transitions, the second of which is reversible. By exploiting the reversibility between the semiconductive and superionic phases of the Ag₂Se shell, photonic crystals with thermally switchable stop bands are made.