Photonic Crystals: Photoresponsive Block Copolymer Photonic Gels with Widely Tunable Photosensitivity by Counter‐Ions (Adv. Mater. 23/2012)

Block copolymer photonic gels exhibiting multiple colors in response to near-UV radiation are demonstrated by Y. Kang and co-workers on page OP 127. The counterions pairing with the polyelectrolyte in the gel layers determine the photosensitivity of photonic gels. The simple replacement of ions can make the photonic gels either highly sensitive or insensitive to near-UV. The illustration shows ionic signaling giving “STOP” and “GO” cues for the photoresponse of these photonic gels.