Orientation measurements of clay minerals by polarized attenuated total reflection infrared spectroscopy

• Published in: Journal of colloid and interface science Vol. 567; pp. 274 - 284
• Main Authors: Grégoire, Brian, Dazas, Baptiste, Hubert, Fabien, Tertre, Emmanuel, Ferrage, Eric, Grasset, Laurent, Petit, Sabine
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.2020; Elsevier
• Subjects: Attenuated total reflection spectroscopy; Chemical Sciences; Clay minerals; Environmental Sciences; Linear dichroism; Orientation; Sciences of the Universe; Thin layer; Clay minerals; Linear dichroism; Thin layer; Orientation; Attenuated total reflection spectroscopy; clay minerals; orientation; thin layer; linear dichroism
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2020.02.021

[Display omitted] •Orientation of clay particles was examined by polarized ATR-FTIR spectroscopy.•The appropriate optical constants and equations were determined.•Structural hydroxyls and water molecules orientations was experimentally achieved.•Experimental results were validated by molecular dynamic simulations. The orientation and organization of molecular guests within the interlayer of clay minerals control the reactivity and performance of tailored organo-clay materials. Such a detailed investigation of hybrid structure on the molecular scale is usually provided by computational methods with limited experimental validation. In this study, polarized attenuated total reflection infrared spectroscopy was used to extract quantitative orientation measurements of montmorillonite particles. The validity of the evanescent electric field amplitude calculations necessary to derive the order parameter was critically evaluated to propose a methodology for determining the orientation of the normal to the clay layer relative to a reference axis, enabling comparison with the results obtained from X-ray scattering experiments and molecular dynamic simulations. Subsequently, the orientation of the interlayer water dipole and surface hydroxyls with respect to the normal of the clay layer was experimentally determined, showing good agreement with molecular simulations. This methodology may provide quantitative insights into the molecular-level description of interfacial processes between organic molecules and clay minerals.