2004 Volume 37 Issue 5 Pages 614-621
This paper describes fabrication of well-ordered mono- and multi-layers of submicron-sized silica or polystyrene (PSt) spheres. The mono-layers of spheres were fabricated on glass plates by a dip-coating technique at various concentrations of KCl, HCl and KOH in colloidal suspension. The mono-layer of spheres in a close-packed hexagonal structure showed an extinction peak in the visible wavelength attributed to a secondary Bragg diffraction. Full width at half maximum (FWHM) of the extinction peak was the lowest at low ionic strength and at neutral pH. Different types of multi-layers of spheres were fabricated by repeating the dip-coating processes. Silica spheres with a size of 589 nm could be mono-layered in the close-packed hexagonal structure on the mono-layer of the 404-nm-PSt spheres. PSt spheres with a size of 404 nm could be layered on the mono-layer of 500-nm-PSt spheres in such a way that the 404-nm-PSt spheres occupied void spaces among three 500-nm-PSt spheres. Silica spheres with a size of 233 nm could be assembled in a two-dimensional network structure on mono-layered 589-nm-silica spheres.