Preparation of α-Co(OH)2 monolayer nanosheets by an intercalation agent-free exfoliation process

In this work, α-Co(OH)2 monolayer nanosheets were prepared by an intercalation agent-free route utilizing a precipitation reaction between epoxide and aqueous complexes of cobalt ions ([Co(H2O)6]2+). The protonation and the following ring-opening reaction of epoxide promoted the hydrolysis of [Co(H2O)6]2+, leading to the formation of α-Co(OH)2 nanosheets. The obtained nanosheets were then exfoliated to monolayer nanosheets in formamide under ultrasonic vibration. A possible exfoliation mechanism is proposed for the exfoliating process of α-Co(OH)2 nanosheets. The water molecules incorporated in the layered structure of α-Co(OH)2 are considered to be the key medium for the layer exfoliation. It seems that the water molecules coordinated with the cobalt ions weakened the interlayer interaction. Therefore, the extraction of water molecules by formamide readily broke the interlayer connection in α-Co(OH)2, resulting in the exfoliation of nanosheets. α-Co(OH)2 monolayer nanosheets were prepared by an intercalation agent-free route utilizing a precipitation reaction between epoxide and aqueous complexes of cobalt ions ([Co(H2O)6]2+).