Facile fabrication of crack-free photonic crystals with enhanced color contrast and low angle dependence

The cracking and iridescence properties of photonic crystals (PCs) greatly limit their availability, especially in the realms of color displays and optical devices. Herein, crack-free amorphous PCs with enhanced color contrast and low angle dependence were fabricated by the co-assembly of polydopamine-coated polystyrene core-shell nanoparticles (PS@PDA NPs) and 3-aminopropyltriethoxysilane (APTES) via a thermal-assisted self-assembly method. The covalent bonds, generated from Schiff base reaction or Michael addition between polydopamine (PDA) and APTES, successfully counteract the tensile stress that is initiated from latex shrinkage during drying, thereby enabling the formation of crack-free PCs. Moreover, thanks to the light-absorbing nature of PDA, a mussel-inspired melanin, and the amorphous arrays, these as-prepared crack-free PCs miraculously exhibit high visibility and low angle dependent structural colors. This facile, low-cost and environmentally friendly approach for preparing crack-free amorphous PCs can be employed in diverse colloidal sphere systems and may boost the promising applications of PCs.