Thermal-induced formation of domain structures in CuO nanomaterials

The growth mechanisms of CuO nanowires (NWs) via thermal oxidation of copper remain controversial in spite of its extensive exploration. Herein, by effectively tuning the growth conditions, we show that the existence of oxygen-concentration-gradient is crucial to maintain the NW growth. Furthermore, based on the proposed growth mechanism, remarkable CuO nanomaterials, including two-dimensional nanosheets are successfully synthesized at higher temperature (>700 degrees C), at which temperature the growth of CuO nanostructures has been suppressed according to the former reports. Detailed structural investigation reveals that the thermal-induced fast ion diffusion may lead to the self-assembly of individual NWs and the nucleation of novel domain structures, such as the (114) twin structures with zigzag twin boundaries. The two-dimensional NSs with high surface area and novel domain structures may exhibit attractive physical properties, such as the high stiffness, which could be employed as building blocks for sophisticated nanodevices.