Metallodielectric photonic glass paints enable hyperchromatic, angle-independent structural color across the full visible spectrum

Abstract

Colloidal photonic glasses are attractive as dye-free, solution-processable pigments that show weak angle dependence, but their red hues are notoriously washed out, because single-particle Rayleigh/Mie scattering produces a strong blue background (form factor). Here, we report metallodielectric photonic glass paints that deliver hyperchromatic structural colors, including vivid angle-independent red. We disperse monodisperse Au@SiO 2 core–shell colloids at 34 vol% in a photocurable, refractive-index-matched ethoxylated trimethylolpropane triacrylate resin. The Au core introduces selective absorption below ~500 nm wavelength, suppressing form factor scattering that would otherwise leak blue light, while index matching sharpens the structure factor-driven reflection by reducing diffuse multiple scattering. A modified Monte Carlo multiple-scattering model predicts spectral narrowing only when both effects are combined. Derjaguin, Landau, Verwey, and Overbeek calculations and Langevin molecular-dynamics simulations reveal that Au-enhanced van der Waals attraction favors reaction-limited crystallization; adding NaCl reduces the Debye length and switches assembly to diffusion-limited aggregation, yielding amorphous short-range order. After ultraviolet (UV) curing into ~100 µm-thick films, the resulting photonic glasses exhibit bright, angle-independent structural colors across the visible range through particle-size tuning. In particular, 230 nm Au@SiO 2 colloidal glasses show a reflectance band confined to 600 to 800 nm wavelengths, producing a saturated red with minimal blue leakage. Because the precursor is a stable liquid resin, the photonic glasses can be freehand-painted to create large-area coatings and fine graphics with high brightness even under sunlight. This work establishes design rules for completing the structural color palette in photonic glasses and provides a practical route to structural color paints.