Exfoliation of layered double hydroxides by an electrostatic repulsion in aqueous solution

Ni/Fe layered double hydroxides (Ni/Fe LDHs) with I I -aminoundecanoic acid (AUA) as pillared species (Ni/Fe LDHs-AUA with Ni/Fe = 4) was prepared by a co-precipitation method. The prepared Ni/Fe LDHs-AUA material was successfully delaminated in an aqueous system by a novel host-guest repulsive interaction process. The delaminated LDHs nanosheets were confirmed by XRD, TG-DSC, TEM, AFM, and IR analyses. XRD measurement on the slurry centrifuged from the solution showed an amorphous halo and the crystalline phase of Ni/Fe LDHs-AUA lost its sharp reflections at pH value of 2.0. After freeze-drying the slurry, the broad pattern was converted into a basal diffraction pattern, indicating the restacking of delaminated nanosheets to restore the original stacked form. AFM images showed that a large part of Ni/Fe LDHs-AUA was delaminated into one elementary layer at least, and the delaminated nanosheets had disk-like shapes with a diameter of ca. 100nm. IR results confirmed the AUA molecules released from the interlayer accompanied with the delamination process and they could not be restacked into the interlayer during freeze-drying the delaminated nanosheets. (c) 2007 Elsevier B.V. All rights reserved.