Fig. 4. Characterization of the structure of LNPs photonic crystal at different color layers.

a Digital microscope image of a cross-section of a photonic crystal. b Size distributions of LNPs in different color layers of the photonic crystal. More than 100 particles were measured in SEM images from c, d and Supplementary Fig. 8. The peaks are at 150, 160, 170, 180, 200, and 240 nm, respectively. SEM images of the fracture cross-section of the photonic crystal in violet (c) and red (d) layers.