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Keywords:

  • hydrotalcite synthesis;
  • layered double hydroxide;
  • Raman spectroscopy;
  • gallium

Abstract

Insight into the unique structure of hydrotalcites (HTs) has been obtained using Raman spectroscopy. Gallium-containing HTs of formula Zn4 Ga2(CO3)(OH)12 · xH2O (2:1 ZnGa-HT), Zn6 Ga2(CO3)(OH)16 · xH2O (3:1 ZnGa-HT) and Zn8 Ga2(CO3)(OH)18 · xH2O (4:1 ZnGa-HT) have been successfully synthesised and characterised by X-ray diffraction (XRD) and Raman spectroscopy. The d(003) spacing varies from 7.62 Å for the 2:1 ZnGa-HT to 7.64 Å for the 3:1 ZnGa-HT. The 4:1 ZnGa-HT showed a decrease in the d(003) spacing, compared to the 2:1 and 3:1 compounds. Raman spectroscopy complemented with selected infrared data has been used to characterise the synthesised gallium-containing HTs. Raman bands observed at around 1050, 1060 and 1067 cm−1 are attributed to the symmetric stretching modes of the (CO32−) units. Multiple ν3 (CO32−) antisymmetric stretching modes are found between 1350 and 1520 cm−1, confirming multiple carbonate species in the HT structure. The splitting of this mode indicates that the carbonate anion is in a perturbed state. Raman bands observed at 710 and 717 cm−1 and assigned to the ν4 (CO32−) modes support the concept of multiple carbonate species in the interlayer. Copyright © 2010 John Wiley & Sons, Ltd.