Structural Color Materials with Color Mixing Effect Using Noble Metal-Free Plasmonic Particles in SiO2-ZrN System

Structurally colored materials with a color mixing effect are developed using SiO2-ZrN core-shell particles, where ZrN nanoparticles used as shells exhibited localized surface plasmon resonances (LSPRs). ZrN nanoparticles (10-30 nm) are attached to monodispersed SiO2 particles by modifying SiO2 particles with polymers. The attached ZrN nanoparticles exhibited a plasmon resonance absorption band at 700 nm. These SiO2-ZrN core-shell particles have a highly monodisperse particle size and assemble into a particle-stacked film with Bragg diffraction light in the visible spectrum. The particle-stacked film of the SiO2-ZrN core-shell particles exhibited the maximum reflection depending on the particle size of the SiO2 core. The ratio of the reflection intensity in the long-wavelength region corresponding to the ZrN absorption to that in the short-wavelength region of the particle-stacked film containing the ZrN shell is less than that of the ratio in only SiO2 particle-stacked film. The results reveal that these particle-stacked films exhibit a "color mixing effect" that combines specific wavelength absorption through plasmon resonance and specific wavelength diffraction owing to the periodic structure without using precious metals.