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).