Gradient inverse opal photonic crystals via spatially controlled template replication of self-assembled opals

A method of spatially controlled template filling and replication is reported herein using Knudsen diffusion-limited atomic layer deposition (ALD). Experimental and theoretical investigations based on the porous framework of self-assembled polystyrene opals further confirm the well controlled z-directional TiO2 spatial gradients paving the way for the fabrication of gradient index inverse opal photonic crystals for the first time.