6 research outputs found
ColorâChanging Paints Enabled by Photoresponsive Combinations of BioâInspired Colorants and Semiconductors
Abstract Modern paints and coatings are designed for a variety of applications, ranging from fine art to extraterrestrial thermal control. These systems can be engineered to provide lasting color, but there are a limited number of materials that can undergo transient changes in their visual appearance in response to external stimuli without requirements for advanced fabrication strategies. The authors describe colorâchanging paint formulations that leverage the redoxâdependent absorption profile of xanthommatin, a smallâmolecule colorant found throughout biology, and the electronic properties of titanium dioxide, a ubiquitous whitening agent in commercial coatings. This combination yields reversible photoreduction upon exposure to sunlight, shifting from the oxidized (yellow) form of xanthommatin, to the reduced (red) state. The extent of photoreduction is dependent on the loading density and size of titanium dioxide particles, generating changes in hue angle as large as 77% upon irradiation. These coatings can be blended with nonâresponsive supplemental colorants to expand the accessible color palette, and irradiated through masks to create transient, disappearing artwork. These formulations demonstrate energyâefficient photochromism using a simple combination of a redoxâactive dye and metal oxide semiconductor, highlighting the utility of these materials for the development of optically dynamic lightâharvesting materials