Molecular assembly in synthesised hydrotalcites of formula CuxZn6-xAl2(OH)16(CO3) . 4H2O-a vibrational spectroscopic study

Frost, Ray L. and Ding, Zhe and Martens, Wayde N. and Johnson, Therese E. and Kloprogge, J. Theo (2003) Molecular assembly in synthesised hydrotalcites of formula CuxZn6-xAl2(OH)16(CO3) . 4H2O-a vibrational spectroscopic study. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 59(2). pp. 321-328.

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DOI : 10.1016/S1386-1425(02)00174-9

Abstract

Infrared and Raman spectroscopy have been used to characterize synthetic hydrotalcites of formula CuxZn6-xAl2(OH)16(CO3).4H2O . The spectra have been used to assess the molecular assembly of the cations in the hydrotalcite structure. The spectra may be conveniently subdivided into spectral features based (a) upon the carbonate anion (b) the hydroxyl units (c) water units. The Raman spectra of the hydroxyl-stretching region enable bands to be assigned to the CuOH, ZnOH and AlOH units. It is proposed that in the hydrotalcites with minimal cationic replacement that the cations are arranged in a regular array. For the CuxZn6-xAl2(OH)16(CO3).4H2O hydrotalcites, spectroscopic evidence suggests that 'islands' of cations arte formed in the structure. In a similar fashion the bands assigned to the interlayer water suggest that the water molecules are also in a regular well-structured arrangement. Bands are assigned to the hydroxyl stretching vibrations of water. Three types of water are identified (a) water hydrogen bonded to the interlayer carbonate ion (b) water hydrogen bonded to the hydrotalcite hydroxyl surface and (c) interlamellar water. It is proposed that the water is highly structured in the hydrotalcite as it is hydrogen bonded to both the carbonate anion and the hydroxyl surface.

ID Code:	1020
Item Type:	Journal Article
Keywords :	hydrotalcite, infrared spectroscopy, Raman microscopy, molecular assembly, structured water
ISSN:	1386-1425
Subjects:	Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > INORGANIC CHEMISTRY (030200)
Divisions:	QUT Faculties and Divisions > Faculty of Science
Copyright Owner :	Copyright 2003 Elsevier
Copyright Statement :	Reproduced in accordance with the copyright policy of the publisher.
Deposited On:	13 Apr 2005
Last Modified:	03 Dec 2008 12:19

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