Formation of MoO₃ and WO₃ nanoscrolls from MoS₂ and WS₂ with atmospheric air plasma

Nanostructured transition metal oxides (TMOs) have intriguing electrochemical and physical properties that make them useful in a variety of electrochemical applications. Here, we report the synthesis of MoO₃ and WO₃ nanoscrolls from atomically thin layers of two-dimensional (2D) MoS₂ and WS₂ with atmospheric air plasma treatment. These structures with rolled layers have an increased surface-to-volume ratio and are promising for electrochemical applications. The morphology of the nanoscrolls is characterized by atomic force microscopy (AFM), while X-ray photoelectron spectroscopy (XPS) measurements confirm the formation of MoO₃ from MoS₂. Control experiments with a plasma generated from a mixture of N₂/O₂/H₂O gases MoS₂ suggest that the rolling mechanism is due to a combination of factors including oxide formation, stresses due to bonding changes, defects in the initial 2D material, and interplanar forces.