Anisotropic silica colloids for light scattering

Abstract

Scattering enhancers are a class of nanomaterials used in every colored or white material surrounding us: from paints and inks to food and cosmetics to packaging and paper. Such hiding pigments usually consist of non-absorbing, high refractive index nanoparticles, for example spherically shaped titanium dioxide nanopowders. However use of TiO₂ carries a high environmental burden. To offset the carbon footprint and health concerns inherent with the use of titanium dioxide, one could approach the challenge of scattering optimization by modifying the morphology of the scattering elements rather than their refractive index. Here, inspired by the bright anisotropic scattering system found in nature, we demonstrate that anisotropic sphero-cylindrical particles can outperform the scattering efficiency of their isotropic counterparts – obtaining an excellent scattering performances across the visible electromagnetic spectrum. We developed a class of micron-sized scattering enhancers composed only of silica. We show that these cylindrical colloids are easily assembled into scattering supracolloidal balls, a new class of pigment microspheres which can be used in formulations for ultrabright coatings.