The Zno meso crystals were prepared by low-temperature hydrothermal precipitation of zinc nitrate with in situ de composition of hexamethylenetetramine (HMT) to control the pH." The morphology of Zno was controlled by addi tion of gum arabic as structure-directing agent. Gum arabic consists of about 10 wt glycoprotein complex and highly branched polysaccharide, which consists of a B-galactose backbone linked to branched arabinose and rhamn ter minated in glucuronic acid. Because of the glucuronic acid group, gum arabic is usually highly negatively charged under most synthetic conditions