Building planar defects into colloidal crystals using particles of different chemical nature

We have fabricated three-dimensional (3D) colloidal crystals containing a two-dimensional (2D) defect made of particles of different nature and of different size. The presence of the extrinsic defect led to an impurity mode within the photonic stop band, which was observed as a pass band in the near-infrared (NIR) spectra. We also built a heterostructure containing a planar defect made of particles of different nature but of the same size than those forming the host opal. A pass band was also observed, due to the difference between the refractive indexes of the guest and host colloids.