In situ growth of layered double hydroxide on disordered platelets of montmorillonite

Layered double hydroxide (LDH) was in situ grown on the disordered platelets of montmorillonite (Mt), and a self-assembled sheet-on-sheet nanohybrid was obtained. To obtain a nanohybrid of cationic/anionic clay with exfoliated Mt platelets, NaMt (sodium-montmorillonite) was fractionated and subsequently treated by ultrasonication in a solution of aluminum nitrate and magnesium nitrate to ensure good dispersion of the NaMt and cation adsorption. Subsequently, the precursors were reacted with ammonia under hydrothermal conditions. The phase compositions of the as-prepared samples were analyzed by X-ray diffraction and Fourier transform infrared spectroscopy. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy investigations revealed the typical sheet-on-sheet and exfoliated Mt structures. The results demonstrated that the LDH grown on the disordered platelets of montmorillonite was successfully synthesized by a simple in situ growth route. A possible formation mechanism for the sheet-on-sheet architecture has been suggested. Using ultrasonically pre-exfoliated disordered Mt platelets as matrixes provided an essential substrate for the nucleation and in situ growth of LDH crystallites. The ammonia solution provided hydroxyl moieties for LDH growth and split the Mt platelets via a breaker effect. It is suggested that the in situ-grown LDH crystals, as spacers, played a crucial role in preventing the reaggregation of the disordered Mt platelets. This study can offer some new insights into developing a nanohybrid of cationic/anionic clay with a unique sheet-on-sheet structure. (C) 2015 Elsevier B.V. All rights reserved.