Fig. 3 shows the SEM image of MgO nanoparticles. SEM images of
both sample A and sample B exhibit flakes-like structures formed due
to the aggregation of several thousands of nanoparticles. The flakes
are dense and interconnected with each other such that no clear boundaries
exist between one another. Fig. 4 shows the typical TEM image and
SAED pattern of MgO nanoparticles (sample B). TEM image (Fig. 4(a))
further confirms the formation of MgO nanoflakes, and the transparent
features suggest that the nanoflakes are very thin. SAED pattern
(Fig. 4(b)) taken from an individual nanoflakes showed three discernible
diffraction rings corresponding to (200), (220) and (222) planes, indicating
the formation of polycrystalline MgO with cubic structure.
Fig. 5 shows the EDX spectra of sample A and sample B. The EDX
spectra revealed that the synthesized products are mainly composed
of Mg and O with an atomic ratio of ~1:1, which are well consistent
with the XRD results.