Self Assembly of Low-Emissivity Materials (SALEM)
Final rept. 1 Sep 1997-28 Feb 2000
CALIFORNIA UNIV SANTA BARBARA DEPT OF CHEMICAL AND NUCLEAR ENGINEERING
Pagination or Media Count:
Self-assembly techniques employing liquid emulsions and colloidal suspensions for the fabrication of photonic crystals are described. To make the photonic crystals, monodisperse emulsion droplets or solid colloidal particles are first allowed to self-assemble into close-packed crystals, having predominately face-centered cubic fcc order. Second, the interstices are filled with a high-refractive-index material, usually titania, using either sol-gel chemistry or by compacting nanoparticles. Finally, the templating emulsion droplets or colloidal particles are removed leaving behind a porous solid in which the spherical pores are ordered on a crystalline lattice fcc. The primary advantages of emulsion templating of photonic crystals is that large monoliths up to 10 mm in size can be produced and that they can be made in the high-refractive-index rutile phase of titania. The primary advantage of the colloidal templating technique is that more perfect crystalline structures can be made, though the overall sample size is generally only about a millimeter or smaller in size and the lower-refractive-index anatase phase of titania is usually produced. In addition, highly scattering porous titania spheres, about 5 microns in diameter, can be made using a combination of colloidal and emulsion templating techniques. These may be useful as pigments in paints.