Nano ceramic coating with photonic crystal structure: a new method for dynamic color display in ceramic art

Structural colors generated by light-matter interaction within photonic crystal architectures that are produced in the nanoscale can be added into several benefits that cannot be obtained by using traditional approaches based on pigments such as: environmental safety, fade resistance and long storage term of optical stability. In this study, a practical assessment done of the thermally stable, pigment-free structural colour coatings for ceramic applications with TiO 2 based Inverse Opal (IO) photonic crystal nano-ceramic coatings. The research is based on one coating system that integrates all three: photonic bandgap tuning, dopant-induced optical modulation and thermal stabilization. Structural color behaviour was regulated by periodicity of the lattices, modulation of the lattice refractive index, and by evolving the lattice structure during calcination. TiO 2 nanoparticles were synthesized via a sol–gel route and self-assembled on ceramic substrates using PMMA microsphere templates (200–250 nm). Controlled calcination at 450–650 °C enabled template removal, structural stabilization, and transition from open-cell to closed-cell architectures. Rare-earth dopants (Er 3+ , Dy 3+ , Tb 3+ ) were incorporated to achieve tunable RGB structural coloration. Multiscale characterization using SEM, XRD, UV–Vis spectroscopy, and optical microscopy confirmed ordered porous structures, uniform coating coverage, and high thermal stability. SEM revealed periodic inverse opal architectures consistent with template dimensions, while XRD confirmed anatase TiO 2 formation with partial anatase–rutile transition at higher temperatures. UV–Vis spectra showed photonic bandgap peaks in the range of ~460–620 nm corresponding to tunable structural colors. Optical microscopy demonstrated uniform structural coloration across ceramic surfaces. The coatings had clear structure–processing–property relationships without compromising the thermal durability, while maintaining good photonic properties. Color intensity decayed with calcination temperature because the loss of the refractive-index contrast occurs, while the structural stability is altered with higher temperatures. These coatings are inverse opals with TiO 2 that are compatible with ceramics for long-lasting structural coloring applications.