Preparation and chemical sense character of two-dimensional colloidal crystal heterostructures

Polystyrene (PS) and poly(methyl methacrylate) (PMMA) suspensions with different particle sizes and refractive index were prepared. A successive air/water interface self-assembly method was developed to fabricate two-dimensional colloidal crystal heterostructures (2D-CCHs) array. Furthermore, 2-hydroxyethyl methacrylate-acrylic acid (HEMA-AA) 2D-CCHs inverse opals with high mass transfer efficiencies were obtained after removing the opal templates. The prepared heterostructures are highly ordered two-dimensional structures proved by scanning electron microscopy images (SEM). Debye diffraction rings, reflectance spectra and structural colors suggested that the optical properties of 2D-CCHs are attributed to overlay of the individual diffraction of single 2D colloidal crystal. With the pH value decreased from 7 to 3, Debye diffraction rings' diameters of double-layers 2D-CCHs inverse opals both shrank nearly 80 nm. The response of 2D-CCHs to pH indicates their preliminary application in chemical sensors.