Spontaneous and artificial structures of thin, Keggin-like polyoxometallate arrays on graphite

Scanning tunnelling microscopic studies have been performed to study the 2D structuring of the inorganic salt, the Keggin-type [AlO4Al12(OH)24(H2O)12]7+ in its sulfate form. This compound forms patches of well ordered monolayer separated by defects seen on large scan images on the top of highly oriented pyrolitic graphite surface. A negative differential resistance peak has been found by scanning tunnelling spectroscopy. Surfactant molecules self-assemble horizontally in the first layer on the graphite plane. Higher uptake resulted in the formation of hemicylinders. In this study sodium dodecyl sulfate has been used to modify the 2D Keggin arrangements. By this combination of organic and inorganic materials the large counter ions were expected to re-arrange on the surface. In this surfactant assisted artificial ordering the distance between the Keggin-type units has been increased