The Seperation Of LDH Colloidal Nanocrystal And The Study On Its Properties

Nanostructured materials have generated of all forms applications, and as one type of layered material, Layered double hydroxides (LDHs), with their high chemical versatility and a tunable anionic exchange capacity, lead to many potential areas of applications. However, as there is no suitable technical conditions, the progress of the mechanism of LDHs nanosheets lags a lot. Herein, we successfully applied a simple method based on the density gradient ultracentriugation technique on the separation of colloidal LDHs NSs and sorted them by their size difference for the first time. And this detailed study give us some deep insight in understanding the procedure mechanism of the LDHs NSs. In addition, EDS analysis provided direct information to reveal the certain relationship between particle size and composition of LDH materials:the particle size increased with Mg element content increasing. By this structure-composition relationship, we could achieve a fine control of LDHs’particle size by adjusting the initial Mg/Al molar ratio. When the room temperature was5℃, we sampled the resulting slurry sub-timely. During the instantaneous nucleation process of the colloid mill, according to the ICP analysis, the Mg/Al molar ratio of the precipitation at30s was close to the feed of Mg/Al ratio. As time went by, the Mg/Al molar ratio of the precipation reduced to about2. Finally the formation procedure of LDH NSs with slightly structural difference is proposed, which was roghly divided into4stages involving coprecipitation of all metallic hydroxides and salts, dissolution of magnesium salts, nucleation of LDHs, and crystallization of LDHs NSs. This research provided some theoretical and experimental basis on how to prepare controlable stalble LDHs colloidal nanoparticles.Due to having a high chemical adjustable chemical changes in the coposition, the change of LDH layer will lead to different M2+/M3+ratio of different atomic arrangement of the laminates of the metal cation. From the theoretical model of the LDH, we knew that LDH with different M2+/M3+mole ratio owns different chemical environment as M2+was oxidized in the chemical reaction. As the experiment showed that, we could obtain different LDH as we changed the mole ratio of the raw material, and we successfully got an amazing result that there exist a linear relationship between the redox peak and their compotion. And they follows a law that as the ratio of Ni2+/Al3+increases, the Ni2+/Ni3+redox potential decreases from0.53V to0.50V. This is because for NiAl-LDH, the number of Al3+around Ni2+in the metal cation laminates decreases as the mole ratio increases, and the chemical barrier is lowered as Ni2+was oxidized into Ni3+.