Growth mechanism and ultraviolet-light emission of the self-assembled complex of MgO nanostructures

Bulk-quantity net-like nanodendrites and four-fold hierarchical nanostructures were synthesized by direct thermal evaporation and oxidation of metallic Mg powder. Their formation mechanism is explained using the self-catalytic vapor-liquid-solid mechanism together with dendritic-crystal epitaxial growth mechanism. Four-branch and eight-branch nanodendrites were also detected. The photoluminescence spectrum reveals that the peak with the maximum intensity is centered at about 3.16 eV (392 nm). Through Gaussian fitting, a strong and narrow ultraviolet-light emission peak centered at 3.16 eV (392 nm) and a relatively weak but broad blue-light emission band centered at 2.74 eV (453 nm) were observed in the photoluminescence emission spectrum, which are respectively attributed to the recombination luminescence of the F+ and F centers (belonging to oxygen-vacancy related defect levels) in the MgO nanostructures. In addition, another very weak and broad red-infrared emission band can also be detected, which is probably due to the relaxation luminescence of impurity levels in the MgO nanostructures.