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Spectroscopic analysis of a dye–mineral composite–a Raman and FT‐IR study
Author(s) -
Manciu F. S.,
Ramirez A.,
Durrer W.,
Govani J.,
Chianelli R. R.
Publication year - 2008
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1979
Subject(s) - palygorskite , silanol , raman spectroscopy , pigment , chemistry , fourier transform infrared spectroscopy , analytical chemistry (journal) , infrared , hydrogen bond , nuclear chemistry , photochemistry , clay minerals , molecule , mineralogy , organic chemistry , chemical engineering , catalysis , optics , physics , engineering
In this investigation, we address the question of how organic thioindigo binds to inorganic palygorskite to form a pigment similar to Maya Blue. We also address how such binding, if it occurs, might be affected by varying the proportion of dye relative to that of the mineral, and by varying the length of heating time used in preparation of the pigment. In addition to samples of palygorskite and thioindigo both alone, four synthetic pigment samples were prepared; two samples of 8 wt.% dye, one heated at 170 °C for 3 h and one at 170 °C for 9 h, and two samples of 16 wt.% dye, one heated at 170 °C for 3 h and one at 170 °C for 9 h. All samples were examined using Fourier transform‐infrared (FT‐IR) and FT‐Raman spectroscopy. For the pigment samples, FT‐IR peaks at 1627 cm −1 are attributed to a downshifted CO stretching mode of thioindigo due to dye–clay interaction. This interpretation is corroborated by FT‐Raman CO peaks with 14 cm −1 shifts to lower wavenumber for the pigment relative to thioindigo alone. Additional Raman scattering between 550 cm −1 and 650 cm −1 also suggests dye–clay interaction through metal–oxygen bonding. We are thus led to the possibility of mostly hydrogen bonding between silanol and carbonyl at lower dye concentration, with a predominance of metal–oxygen bonding at higher dye concentration. Copyright © 2008 John Wiley & Sons, Ltd.