Molecular-Scale Imaging of Clay Mineral Surfaces with the Atomic Force Microscope

H. Hartman, Garrison Sposito, Andrew Yang, S. Manne, S. A. C. Gould and P. K. Hansma
Department of Electrical Engineering and Computer Science, University of California Berkeley, California 94720
Department of Soil Science, University of California, Berkeley, California 94720
Department of Physics, University of California, Santa Barbara, California 93106

Abstract: Specimen samples of Crook County montmorillonite and Silver Hill illite, purified and prepared in the Na-form, were imaged under 80% relative humidity using an atomic force microscope. The direct images showed clearly the hexagonal array of hexagonal rings of oxygen ions expected for the basal planes of 2:1 phyllosilicates. Fourier transformation of the digital information obtained by the microscope scanning tip led to an estimate of 5.1 ± 0.3 Å for the nearest-neighbor separation, in agreement with the ideal nearest-neighbor spacing of 5.4 Å for hexagonal rings as derived from X-ray powder diffraction data. The atomic force microscope should prove to be a useful tool for the molecular-scale resolution of clay mineral surfaces that contain adsorbed macromolecules.

Key Words: Atomic force microscopy • Illite • Montmorillonite • Oxygen distances • Surface

Clays and Clay Minerals; August 1990 v. 38; no. 4; p. 337-342; DOI: 10.1346/CCMN.1990.0380401
© 1990, The Clay Minerals Society
Clay Minerals Society (www.clays.org)