Preparation and wettability of Zn-Al layered double hydroxide film directly grown on highly porous anodic alumina oxide template

Zinc-aluminum layered double hydroxide (Zn-Al LDH) thin films were prepared by direct precipitation on the surface of porous anodic alumina oxide (AAO) template. The Zn-Al LDH was assigned to Zn6Al12(OH)(16)CO3.nH(2)O according to the XRD and EDX data. The nano-pores provided channels and the nano-sized wall-edges for supplying Al3+ and highly active reaction sites, thereby the Zn-Al LDH films can be grown more efficiently on porous AAO membrane than those on flat bulk alumina oxide surface. The water contact angle (CA) of the as-prepared Zn-Al LDH films was measured to be 122 degrees, indicating a hydrophobic surface, but after calcination at 600 degrees C for 2 h, the water CA became 65 degrees, suggesting a hydrophilic surface. Comparative analyses of the surface morphological characteristics and elements with respect to the as-prepared and calcined films implied a thermal induced reconstruction of the Zn-Al LDH structure, which was ascribed to the changes of surface wettability. (C) 2007 Elsevier B.V. All rights reserved.