Mechanochromic luminescence of a bionanocomposite hydrogel.

Bionanocomposite hydrogels were prepared from gelatin hydrogel and subsequent ionic crosslinking in the presence of a smectite with adsorbed cyanine dye (pseudoisocyanine). In addition to the improved mechanical properties achieved by the hybridization with the smectite, the composite hydrogel underwent a photoluminescence color change from red to blue upon stretching and recovered from blue to red upon relaxing. The novel luminescence mechanochromism was explained by the aggregation/de-aggregation of the cyanine dye adsorbed on the smectite by stretching/relaxing.