Synthesis and Raman spectroscopy of indium-based hydrotalcites of formula Mg6In2(CO3)(OH)16•4H2O

Insight into the unique structure of layered double hydroxides has been obtained using a combination of X-ray diffraction and Raman spectroscopy. Indium-containing hydrotalcites of formula Mg4In2(CO3)(OH)(12)center dot 4H(2)O [2:1 In-LDH (layered double hydroxides)] through to Mg8In2(CO3)(OH)(18)center dot 4H(2)O (4:1 In-LDH) with variation in the Mg : In ratio have been successfully synthesized. The d(003) spacing varied from 7.83 angstrom for the 2 : 1 LDH to 8.15 angstrom for the 3:1 indium-containing layered double hydroxide. Raman spectroscopy complemented with selected infrared data has been used to characterize the synthesized indium-containing layered double hydroxides of formula Mg6In2(CO3)(OH)(16)center dot 4H(2)O. Raman bands observed at around 1058, 1075 and 1115 cm(-1) are attributed to the symmetric stretching modes of the CO32- units. Multiple v(3) CO32- antisymmetric stretching modes are found at around 1348, 1373, 1429 and 1488 cm(-1) in the infrared spectra. The splitting of this mode indicates that the carbonate anion is in a perturbed state. Raman bands observed at 690 and 700 cm(-1) assigned to the v(4) CO32- modes support the concept of multiple carbonate species in the interlayer. Copyright (C) 2010 John Wiley & Sons, Ltd.