Surface templated inverse photonic glass for saturated blue structural color

To substitute conventional pigments, which often are toxic or suffer from fading in ultraviolet light, non-iridescent structural colors should demonstrate high spectral selectivity, while being also mechanically stable. However, conventional photonic glass (PhG) shows low color saturation due to the gradual transition in the reflection spectrum and low mechanical stability due to weak interparticle attachment. Here, a PhG with sharp spectral transition in comparison with the conventional full sphere PhG is designed by a conformal coating via atomic layer deposition (ALD) onto an organic PhG template. The ALD deposition allows to control the film thickness precisely for the highly saturated color. This structure can be described by hollow particle motifs with the effective size larger than the interparticle distance. Such unusual PhG is motivated by the achievable features in the spatial Fourier transform of a disordered assembly of such motifs. The surface-templated inverse PhG shows much higher color saturation than the direct PhG from full spheres. Moreover, the dense and solid connected shell will be beneficial for mechanical stability. These results pave the way for highly saturated structural colors. The demonstrated sharp spectral selection feature can be also considered for many related applications such as sunscreens, photovoltaics and radiative cooling by adjusting the reflection transition to the required wavelength. This can be achieved by proportionally scaling the motif and lattice dimensions as well as the film thickness.