Ultrathin photonic crystal film with supersensitive thermochromism in air

Thermochromic photonic crystals (PC) have been extensively studied owing to their potential applications in displays, smart windows, sensors, and anti-counterfeiting devices. However, the poor water-retention capacity of the traditional hydrogel-based thermoresponsive PCs makes them unstable, and their color change is realized by immersion in water. Although polymer elastomer-based PC can increase stability, their response range as well as sensitivity is dramatically decreased. In this study, an ultrathin polymer-filled ZnS@SiO2 PC film with long-term stability and ultrasensitive thermochromism is presented. The polymer provides the film with excellent stability, and the ultrathin PC structure ensures that the film exhibits distinguished thermochromism in air rather than in water, owing to condensation. The structural color changed from violet to near-infrared, and the change in the reflection wavelength was as high as 300 nm when the temperature decreased from 15 °C to 5 °C. Furthermore, an ultrathin PC layer was applied to fabricate thermochromic smart fabrics. This work demonstrates the design and fabrication of ultrathin PC films, as well as their ultrasensitive response and high stability, presenting a platform for combining different types of functionalized polymer materials and achieving more ingenious responsive effects.