Nanohybrids of edible dyes intercalated in ZnAl layered double hydroxides

Abstract

Edible dyes such as Allura (R) Red AC (C18H14N2O8S22-), Sunset Yellow FCF (C16H10N2O7S22-), and Brilliant Blue FCF (C37H34N2O9S32-) were successfully intercalated into the gallery spaces of ZnAl layered double hydroxides (LDHs). Those organic-inorganic nanohybrids were synthesized by co-precipitating the aqueous solution of zinc nitrate and aluminum nitrate simultaneously in the presence of anionic dyes. From the X-ray diffraction and infrared spectroscopic analyses, we found that the dye molecules could be intercalated into hydroxide layers without any changes in their chemical and structural properties. The basal spacings were determined to be 24.0, 20.3, and 24.7 A for Allura (R) Red AC, Sunset Yellow FCF, and Brilliant Blue FCF intercalated LDHs, respectively. According to the solid UV-vis spectroscopic analyses, the absorbance intensity of dye-intercalated LDHs was clearly enhanced with the band narrowing compared to those of the corresponding dye salts due to the charge transfer between the host lattice and spatially confined dye molecules. (c) 2007 Elsevier Ltd. All rights reserved.