Scientists have figured out why blue and green are the most common structural colors found in nature.
In the natural world, there are two main ways of displaying color: using pigments that selectively absorb color, or using structural color – using microscopic structures to control the reflection of light waves.
Scientists have developed a computer model that explains why the brightest matte structural colors in nature are almost always blue and green. It turned out that the whole secret lies in the fact that these are the limits of structural color in the visible light spectrum.
In addition to a better understanding of how the brightest blues and greens are created in the natural world, research can also be useful in developing vibrant, sustainable paints and coatings that won’t tarnish over time and release toxic chemicals.
“In addition to its intensity and fade resistance, matte paint that uses a structural color would also be much more environmentally friendly as it does not require toxic dyes and pigments,” says physicist Gianni Jacucci of the University of Cambridge in the UK. “However, we first need to understand what the limitations are in recreating these types of colors before any commercial use is possible.”
In the “structural case” the actual color itself (blue, green, red, etc.) determines the nanoscale structure of the surface that has this color. Sometimes – for example, on peacock feathers – this color can be iridescent and change between color shades at different angles and under different lighting conditions. These transitions are carried out by the ordered crystalline structures of feather hairs.
With other structures, you can get a matte color that does not change due to disorder; in nature, this phenomenon is observed only when blue and green shades are obtained. The essence of the new study was to see if this circumstance was a limitation for these structures.
A new computer model, based on artificial materials called photonic glasses, has shown that red really goes beyond scattering methods for matte structural colors.
“Because of the complex relationship between single and multiple scattering and the effect of correlated scattering, we found that in addition to red, yellow and orange also become difficult to achieve colors,” explained chemist Sylvia Vignolini of the University of Cambridge.
This is most likely why, in nature, vibrant matte reds are created using natural pigments rather than structural color. The team believes that evolution has led to different ways of producing red colors due to the limitations of the underlying structures.
