Probing the chemical reactivity of interfaces: Investigation on the interaction of dehydroindigo with Laponite by UV–vis, Raman and infrared spectroscopy

In this work, the interaction between dehydroindigo (an intermediary oxidized form of indigo) and Laponite clay was investigated. Dehydroindigo (DHI) has been detected when indigo is adsorbed by clay minerals, but it is relatively unstable and in the presence of water it turns back into indigo. It i...

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Bibliographic Details
Published in:Vibrational spectroscopy 2018-01, Vol.94, p.83-88
Main Authors: Bernardino, Nathália D., Constantino, Vera R.L., de Faria, Dalva L.A.
Format: Article
Language:English
Subjects:
Aspect ratio
Behavior
Chemical bonds
Clay
Clay minerals
Dehydroindigo
Hydrogen
Hydrogen bonding
Indigo
Laponite
Nitrogen
Palygorskite
Silanol group
Stability
Studies
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Summary:In this work, the interaction between dehydroindigo (an intermediary oxidized form of indigo) and Laponite clay was investigated. Dehydroindigo (DHI) has been detected when indigo is adsorbed by clay minerals, but it is relatively unstable and in the presence of water it turns back into indigo. It is, therefore, important to understand the factors that extend its stability and Laponite was chosen because the small aspect ratio implies in a large amount of silanol groups (SiOH) which would thus favor the DHI interaction through hydrogen bonding. A significant bathochromic shift (65nm) of the DHI π®π* transition band in the visible region and changes in the relative intensities and position of the Raman bands at 1530, 1378 and 1167cm−1 assigned to ν(NCCN), δ(CN) and ν(CN) respectively, indicate that the interaction is stronger than expected for the van der Waals and polarization forces involved in the external surfaces interactions with the siloxane groups. It was also observed that DHI presents an enhanced photochemical stability when interacting with Laponite. These results indicate that hydrogen bonding between a DHI nitrogen atom and the −SiOH or MOH groups is mainly responsible for the behavior present in the DHI+Lap system.
ISSN:0924-2031
1873-3697
DOI:10.1016/j.vibspec.2016.12.002