Morphological evolution of ZnAl-layered double hydroxide nanostructures grown on Al₂O₃/Si substrate

We investigated the morphological evolution of ZnAl-layered double hydroxides (LDHs) during the hydrothermal reaction on an Al₂O₃ seed layer grown Si substrate with variation of source molar concentration. The surface morphology of the ZnAl-LDHs changed from larger granular plates to smaller granular plates, which gradually packed each other with an increasing molar concentration of hydrothermal solution from 10 to 90 mM. The structural and chemical investigations by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed that the Zn/Al ratio in the ZnAl-LDHs increased with increasing the source molar contents. Optical investigations by Raman and photoluminescence (PL) spectra showed that the ZnAl-LDH in our results contained nitrate interlayer and the emission spectra changed because the surface charge density decreased with increasing the Zn/Al ratio and affected on the energy-transfer process.