AsianScientist (Oct. 23, 2019) – A team of scientists in Japan has found that pigments of various colors can be obtained by combining fine silica particles and a complex of iron and tannic acid. Their findings, which are published in the journal ACS Sustainable Chemistry & Engineering, could pave the way for inexpensive and harmless substances used for foods and cosmetics.
In response to worldwide concern over the adverse effects of chemical substances on human health and the environment, most developed countries have legally restricted the use of dyes containing heavy metals or carcinogenic organic compounds. Replacing such color materials with safer substances is therefore an urgent matter for industries that use them.
Responding to this call for safer color pigments are researchers led by Associate Professor Yukikazu Takeoka of Nagoya University, Japan, who developed safe and inexpensive pigments using fine particles based on silica, which is abundant on earth, and tannin iron (Fe-TA), derived from tannic acid (TA) and iron (Fe) obtained from plants.
By changing the size of the fine particles composed of silica and iron tannate, the researchers were able to alter the resulting color of the pigments. Moreover, the presence of TA increases the mechanical stability of the pigment and improves its adhesion to glass substrates, making it suitable for coating applications.
“In our daily lives, pigments and dyes that absorb part of the visible spectrum and scatter or transmit other colors of light are widely used,” said Takeoka.
“However, the natural world contains not only pigments and dyes of this kind, but also structurally colored materials, which display vivid colors because of the interaction of their fine structure with light. Considering that, there is no doubt that the safe and inexpensive structurally colored pigments introduced in this study will be useful for everyday life,” he added.
The article can be found at: Sakai et al. (2019) Colorful Photonic Pigments Prepared by Using Safe Black and White Materials.
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Source: Nagoya University; Photo: Shutterstock.
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