Probing the Morphology of Laponite Clay Colloids by Atomic Force Microscopy

This paper describes a direct and quantitative study of the size and shape of Laponite clay colloids by atomic force microscopy. Atomic force microscopy (AFM) images of Laponite particles deposited on mica, obtained under ambient conditions, reveal that the particles are mainly present as individual entities. Morphological quantitative analysis of the AFM images indicates that the individual particles have an anisotropic shape with a height of 1.2 nm and mean lateral dimensions of 24.0 ± 6.9 nm and 16.8 ± 4.9 nm. Furthermore, the height histogram indicates that 20% of the particles on the mica are dimers conferring to the system a height polydispersity index of 1.18. Thereafter, AFM results were used to simulate a small-angle neutron scattering (SANS) curve and good agreement was obtained with an experimental SANS curve. This work demonstrates the efficiency of the AFM technique for the characterization of Laponite colloids and nanoparticles in general and its complementarity with neutron scattering techniques.