Photonic Whitener Pigments: A Sustainable Alternative to Titanium Dioxide Nanoparticles

Titanium dioxide is the world's most widely used pigment; however, increased cost and potential environmental concerns have driven a need for a sustainable replacement. The study has developed a scalable method to produce more sustainable photonic whiteners with application in paint and other dispersion formulations. Bio-resourced zein protein nanoparticles are synthesized and used as sacrificial templates within a silica matrix. These micron-sized photonic whiteners exhibit morphologically dependent whitening capabilities when incorporated into paint films. When the silica content is insufficient, an open structure forms, while an excess of silica content results in fewer interfaces and reduced scattering efficiency, leading to suboptimal whitening performance. An ideal ratio of silica to zein nanoparticles ensures optimal whitening properties comparable to commercially available whitener alternatives to titanium dioxide. Further analysis reveals a non-uniform internal morphology of the photonic whiteners, with a silica-void network dispersed within a solid silica matrix. This morphology provides an innovative criterion for optimizing the whitening performance of photonic structures beyond composition.