Structurally Colored Thin Films Based on Acetylated Lignin Nanoparticles

In nature, colors can originate from pigments or structural effects, with the latter producing brilliant hues through the interference of light with nanoscale structures. This study describes a feasible strategy to achieve structurally colored films based on acetylated lignin nanoparticles. Lignin nanoparticles were prepared by using membrane emulsification and subsequently self-assembled into multilayered films on silicon substrates through an evaporative process. These films exhibit vivid structural colors resulting from thin-film interference, with hues that vary with film thickness. Spectroscopic reflectance measurements and structural analysis reveal a wide range of colors spanning across the visible spectrum. The observed colors are ascribed to interference effects and could be modeled using the transfer matrix method. Furthermore, we demonstrate that increasing relative humidity causes clear color shifts associated with reflectance peak position changes.