Cover Picture: UV‐Light‐Induced Swelling and Visible‐Light‐Induced Shrinking of a TiO₂‐Containing Redox Gel (Adv. Mater. 9/2007)

Abstract Polyacrylate gels containing Ag⁺ and TiO₂ nanoparticles are shown to swell under UV light and shrink under visible light in water. In work reported by Tetsu Tatsuma and co‐workers on p. 1249, the TiO₂ absorbs UV light and reduces the Ag⁺, whereas the deposited Ag absorbs visible light and dissolves itself. These redox reactions change the interactions between the polymer chains and eventually the volume of the gel, as shown on the cover.