Atomic force microscopy study of clay nanoplatelets and their impurities

Abstract

The results of an in-depth study of 1 nm thick individual clay sheets by atomic force microscopy (AFM) are presented. Several techniques have been employed, including lateral force microscopy (LFM) and force modulation microscopy (FMM). The individual clay sheets, also referred to as clay nanoplatelets in the literature, were found to be extremely compliant and strongly adhered to a variety of substrates. In all cases, these nanoplatelets were accompanied by mobile impurities that could not be separated from the nanoplatelets. A detailed examination of these impurities using AFM suggests that they are comprised of low molecular weight silicates as well as the intercalating salt used to process the clay. An understanding of the nature and chemistry of these impurities will be necessary as models of these clays are developed for various applications, such as reinforcement in composite materials or elements for molecular electronics. Further, these clay nanoplatelets and their impurities present a novel two-dimensional nanoscale system for future surface science studies using AFM and other methods.