Structural colorations have been recognized as a significant way to replace conventional organic dyes for paints, inks, packaging, and cosmetics because of brilliant colors, high stability, and eco-friendliness. However, most current structural-color pigments present an iridescent appearance, and it remains difficult to mitigate a trade-off between lowering the iridescence effect and maintaining the color saturation and brightness. Here, we demonstrate a universal yet economical approach to prepare cellulose structural-color pigments with different sizes. A combined ultrasonication and grinding treatment is explored to adjust the pigment colors as well as control the iridescence-to-non-iridescence transition that depends on the pigment size. The cellulose pigments can be applied on irregular and curved surfaces, having high water-, chemical-, and mechanical-resistances. With humidity-sensing behaviors, the pigments can be further integrated into monitoring systems for environmental management. Such a preparation strategy overcomes the limitation of controlling iridescent and non-iridescent structural colors without sacrificing color properties, which may bring more opportunities to develop new eco-friendly pigments for wide applications.
Keywords: Cellulose pigments; Humidity-sensing; Iridescence-to-non-iridescence transition; Size effect.
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