Two-dimensional colloidal crystal heterostructures

We developed a simple method to fabricate colloidal crystal heterostructures (CCHs) with two or three stacked poly(methyl methacrylate) (PMMA) particle two-dimensional (2D) colloidal monolayer arrays of different particle spacings that independently diffract light. The 2D colloidal monolayer arrays of PMMA were prepared by using the air/water interface self-assembly method we recently developed. Two- and three-layer CCHs were fabricated by successive deposition of 2D PMMA colloidal monolayer arrays of different particle sizes. The structure and optical properties of 2D monolayer arrays and 2D CCHs were characterized with SEM, reflectance spectra, their Debye diffraction rings and their diffracted wavelengths. The layers maintain their spacing and ordering as they are transferred from the air/water interface onto the substrate. The 2D CCHs diffraction measurements suggest that the optical properties of the colloidal crystal heterostructures arise mainly from the independent diffraction of the individual 2D colloidal arrays. This enables selective combination of particular light wavelengths through diffraction of the 2D CCHs.