Facile Sodium Alginate Assisted Assembly of Ni-Al Layered Double Hydroxide Nanostructures

Self-assembled three-dimensional Ni-Al layered double hydroxide (LDH) nanostructures have been successfully synthesized using a facile biopolymer-assisted approach in the presence of a simple, safe, and inexpensive sodium alginate biopolymer under hydrothermal conditions. The structure and morphology of LDH nanostructures obtained have been investigated by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-M), thermogravimetric and differential thermal analysis (TG-DTA), and UV-visible diffuse spectroscopy (UV-vis). Three types of pompon-like, marigold-like, and coral-like LDH nanostructures could be obtained by adjusting the synthesis parameters including hydrothermal aging time, concentration of metal ions, and reaction temperature. A possible formation mechanism for the controlled organization of primary LDH nanosheet building units into special three-dimensional nanostructures is proposed on the basis of the interaction between sodium alginate molecules and LDH crystals. Furthermore, after calcination of LDHs at 500 and 700 degrees C, the resulting NiO-based mixed metal oxides still maintain the three-dimensional morphology of their LDH precursors to some extent, indicative of the high thermal stability of nanostructures. The findings in this work provide a feasible approach for the morphosynthesis of LDH nanomaterials with special superstructures.