Multicolored melanin
Ultra-resistant paints based on skin pigment were obtained
Sergey Vasiliev, Naked Science
To achieve the desired color of the surface, you can use dyes containing a pigment that reflects radiation of a certain wavelength, giving the subject an appropriate shade. However, over time, the pigment molecules degrade, and such paints inevitably fade. Another approach is to form certain structures on the surface that create color. This is how, for example, the optical coloring of the wings of butterflies appears. Light is reflected from the inner layers of the scales, the reflected rays interfere and form a color pattern. It is incomparably more difficult to get such a color, but it will practically not degrade.
A new technology for obtaining such a dye was proposed by scientists from China, the USA and Belgium, whose article is published by the journal Science Advances. The authors used melanin, a natural pigment that gives color to bird feathers, fish scales, and our skin, hair and iris. Melanin nanoparticles have a black color, but scientists forced them to form even larger supramolecular aggregates in transparent silicon oxide. Such structures had one color or another depending on the density of the nanoparticles inside and the interference of rays reflected by different nanoparticles.
Dye structures at different magnifications: the size and location of melanin particles in silica allow to achieve different shades / ©Xiao et al., 2017
Varying the sizes of the melanin nanoparticles themselves, as well as the volume of space occupied by silica, the authors demonstrated dyes of different shades, from olive green to deep blue. According to them, the new method is much simpler than other approaches to obtaining structures for optical coloring. The dye is obtained at room temperature and pressure, in a simple aqueous solution of octanol, and the resulting particles are easily extracted in powder form. In the future, they hope to learn how to include melanin nanoparticles of different diameters in one structure – theoretically, this will allow achieving any conceivable shade.
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18.09.2017