It is challenging to prepare monolayer MoS2 with activated basal planes by a simple and efficient way. In this study, an interlayer spacing expanded counterpart, ammonia-intercalated MoS2 was obtained by a simple hydrothermal reaction of ammonium molybdate and elemental sulfur in hydrazine monohydrate solution. Then, the ammonia-intercalated MoS2 could be easily exfoliated by ultrasonication to get monolayer MoS2. Importantly, these monolayer MoS2 possessed rich S vacancies.
