Fig. 2From: Sulfur-Doped Alkylated Graphene Oxide as High-Performance Lubricant AdditiveThe high-resolution sulfur (2p) XPS analysis of the SA-GO which is prepared by the reactions of butylamine (a), octylamine (b), laurylamine (c), octadecylamine (d), and the sulfur-doped graphene oxide (the oxidation time of the graphene oxide is 24 h)Back to article page