Synthesis mechanism study of layered double hydroxides based on nanoseparation.

ABSTRACT

Colloidal layered double hydroxides (LDH) nanosheets were sorted by their lateral sizes using a density gradient ultracentrifuge separation technique. Composition investigations on these size-sorted nanosheets indicated that larger sheets had higher MgAl ratio than the smaller ones. Experiments using different MgAl feed ratios confirmed that high MgAl ratio induced fast sheet growth speed. Tracking the source of the MgAl spatial distribution difference in one batch of synthesis at the nucleation process revealed the coprecipitation-redissolution of Mg(2+). Thus the discriminative separation of these nanosheets led to a new insight into the structure-composition relationship of LDH nanomaterials and more understanding on their formation mechanism.