Abstract
The beautiful structural colors in bird feathers are some of the brightest colors in nature, and some of these colors are created by arrays of melanin granules that act as both structural colors and scattering absorbers. Inspired by the color of bird feathers, high-visibility structural colors have been created by altering four variables: size, blackness, refractive index, and arrangement of the nano-elements. To control these four variables, we developed a facile method for the preparation of biomimetic core-shell particles with melanin-like polydopamine (PDA) shell layers. The size of the core-shell particles was controlled by adjusting the core polystyrene (PSt) particles’ diameter and the PDA shell thicknesses. The blackness and refractive index of the colloidal particles could be adjusted by controlling the thickness of the PDA shell. The arrangement of the particles was controlled by adjusting the surface roughness of the core-shell particles. This method enabled the production of both iridescent and non-iridescent structural colors from only one component. This simple and novel process of using core-shell particles containing PDA shell layers can be used in basic research on structural colors in nature and their practical applications.
Highlights
Coloration is one of the most interesting aspects in nature[1,2]
We demonstrated a facile method for the fabrication of submicrometer-sized monodisperse PDA black particles that mimic melanin granules and used them as components of structural color materials[21]
To produce high-visibility structural colors, it remains a challenge to develop an effective strategy for the preparation of colloidal particles with any blackness
Summary
The core-shell particles with thick shell layers produced non-iridescent structural color pellets (Fig. 5) This result is likely due to the arrangement of the particles. Diffraction will be suppressed and the reflection spectra related to the size of the particles will be selectively enhanced, producing non-iridescent structural colors[14] These results clearly indicated that two type of colors were observed for the different particle arrangements. To create high-visibility structural colors, we designed and synthesized PSt@PDA core-shell particles that met the following four conditions: size, blackness, refractive index, and arrangement. While PSt@PDA particles with smooth surfaces produced colloidal crystal structures, PSt@PDA particles with rough surfaces produced amorphous structures As a result, both iridescent and non-iridescent structural colors were separately prepared from only one component. The results of these investigations will be described in future reports
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