The intercalation and exfoliation of tungsten disulfide

Abstract

The exfoliation of WS₂, the separation of this layer compound into single molecular layers suspended in solution, was found more difficult than the exfoliation of MoS₂ reported earlier. The difficulty was found to be the resistance of the WS₂ to intercalation. By ultrasonic treatments while exposed to hexane plus n‐butylithium, the lithium was found to intercalate, and exfoliation by immersion in water became possible. Restacking the WS₂ by drying in a basic solution led to much larger crystallites than the as‐received material, while flocculating by decreasing the pH led to small crystallites with a high density of edge planes. Nickel and aluminum inclusions lead to poor restacking, with no regular c spacing between WS₂ basal planes. The more vigorous exfoliation procedure applied to MoS₂ also leads to loss of regular c spacing (the x‐ray diffraction pattern is essentially that of single molecular layers).