Raman spectroscopy of urea and urea-intercalated kaolinites at 77K
(2000) Raman spectroscopy of urea and urea-intercalated kaolinites at 77K. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 56A(9):1681 -1691.
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Abstract
The Raman spectra of urea and urea-intercalated kaolinites have been recorded at 77K using a Renishaw Raman microprobe equipped with liquid nitrogen cooled microscope stage. The NH2 stretching modes of urea were observed as four bands at 3250, 3321, 3355 and 3425 cm-1 at 77K. These four bands are attributed to a change in conformation upon cooling to liquid nitrogen temperature. Upon intercalation of urea into both low and high defect kaolinites, only two bands were observed near 3390 and 3410 cm-1. This is explained by hydrogen bonding between the amine groups of urea and oxygen atoms of the siloxane layer of kaolinite with only one urea conformation. When the intercalated low defect kaolinite was cooled to 77K, the bands near 3700 cm-1 attributed to the stretching modes of the inner surface hydroxyls disappeared and a new band was observed at 3615 cm-1. This is explained by the breaking of hydrogen bonds involving OH groups of the gibbsite-like layer and formation of new bonds to the C=O group of the intercalated urea. Thus it is suggested that at low temperatures two kinds of hydrogen bonds are formed by urea molecules in urea-intercalated kaolinite.
| Item Type: | Journal Article |
|---|---|
| Status: | Published |
| Keywords: | Intercalation, Kaolinite, Urea, Liquid Nitrogen Temperature, Raman Microscopy |
| Subjects: | 250000 Chemical Sciences > 250100 Physical Chemistry (incl. Structural) > 250105 Structural Chemistry 250000 Chemical Sciences > 250100 Physical Chemistry (incl. Structural) > 250104 Chemical Spectroscopy 250000 Chemical Sciences > 250100 Physical Chemistry (incl. Structural) > 250103 Colloid and Surface Chemistry |
| ID Code: | 12267 |
| Deposited By: | Frost, Ray |
| Deposited On: | 29 January 2008 |
| Alternative Locations: | http://dx.doi.org/10.1016/S1386-1425(00)00223-7 |
| Copyright Owner: | Copyright 2000 Elsevier |
| Copyright Statement: | Reproduced in accordance with the copyright policy of the publisher. |