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Science 2 December 1994:
Vol. 266. no. 5190, pp. 1551 - 1555
DOI: 10.1126/science.266.5190.1551
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Articles

Nanoscale Imaging of Molecular Adsorption

Heng Cai 1, Andrew C. Hillier 2, Kevin R. Franklin 3, C. Craig Nunn 1, and Michael D. Ward 2

1 Unilever Research U.S.-Edgewater Laboratory, 45 River Road, Edgewater, NJ 07020, USA.
2 Department of Chemical Engineering and Materials Science, University of Minnesota, Amundson Hall, Minneapolis, MN 55455, USA.
3 Unilever Research-Port Sunlight Laboratory, Quarry Road East, Bebington, Wirral L63 3JW, UK.

In situ atomic force microscope observations were made of the adsorption of anions (1– or 2–) of the organic diacid 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid from aqueous solution onto the (0001) surface of hydrotalcite (HT), a layered clay. This adsorption process is believed to mimic the ion-exchange reactions that occur within the layers of HT and other layered clays. Atomic force microscope images of the (0001) surfaces of HT, acquired in aqueous solutions, reveal an ordered structure with respect to magnesium and aluminum atoms. In the presence of the anions, atomic force microscopy indicates pH-dependent adsorption onto the formally cationic HT surface. The anion coverage is governed by electroneutrality and steric interactions between the bulky anions within the adsorbed layer, whereas the orientation of the anions with respect to the HT surface is dictated by coulombic interactions and hydrogen bonding between the anion's sulfonate moiety and clay hydroxyl triads. These observations reveal that the reversible adsorption of molecular species can be examined directly by in situ atomic force microscopy, providing details of surface stoichiometry and adlayer symmetry on the local, molecular level.

Submitted on June 30, 1994
Accepted on September 28, 1994


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
PREPARATION OF LARGE PLATY PARTICLES OF Co-Al LAYERED DOUBLE HYDROXIDES.
M. Kayano and M. Ogawa (2006)
Clays and Clay Minerals 54, 382-389
   Abstract »    Full Text »    PDF »
Interlayer structure and dynamics of Cl-bearing hydrotalcite: far infrared spectroscopy and molecular dynamics modeling.
J. Wang, J. Wang, A. G. Kalinichev, J. E. Amonette, and R. J. Kirkpatrick (2003)
American Mineralogist 88, 398-409
   Abstract »    Full Text »    PDF »


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