layered double hydroxides abbr., LDH (rus. слоистые двойные гидроксиды abbr., СДГ) — a class of inorganic compounds consisting of positively charged layers formed by metal ions with different oxidation rate and hydroxide ions with mobile anions in the interlayer space.

Description

The composition of the most widespread LDHs is usually expressed by the general formula where or , and ; at and , .

The number of hydroxides is fixed and determined by LDHs' cation composition while anions in the interlayer space can be relatively easily replaced. Varying the cationic layer composition we can change its charge and, accordingly, the distance between the layers and the number of anions in the interlayer space. Introduction in the interlayer space of bipolar anions (e.g., surfactants) ensures that when the medium changes its polarity LDHs' particles can be split into separate fragments, up to individual layers. This process is reversible but the long-range order in such structures cannot be fully recovered. Layered double hydroxides are of considerable interest for nanotechnology applications. They can be used as two-dimensional nanoreactors (see nanoreactor, 2D), as two-dimensional model systems to study energy transfer processes, as systems for controlled drugs release, etc.

Illustrations

Fig. 1. Structural model of layered double hydroxide. Oxide layer — 
[Mg3
Fig. 1. Structural model of layered double hydroxide. Oxide layer —  [Mg3Al(OH)8]+ , interlayer space contains  Eu(C5H4NCOO)3; anions OH , as well as water contained in the interlayer space are not shown in the figure. Authors: U. Kynast, Fachhochschule Muenster, Natalya G. Zhuravleva, A. A. Eliseev, Lomonosov Moscow State University, Department of Materials Science.
Fig. 2. Isomer separation using their selective adsorption by layered double hydroxides. Author: Der
Fig. 2. Isomer separation using their selective adsorption by layered double hydroxides. Author: Dermot O’Hare, Oxford University, UK.

Authors

  • Zhuravleva Natalya G.
  • Shlyakhtin Oleg A.

Sources

  1. Layered double hydroxides // Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Layered_double_hydroxides (reference date: 12.12.2011).
  2. Wiliams G.R. and O'Hare D. Towards understanding, control and application of layered double hydroxide chemistry // J. Mater. Chem., 2006 - vol. 16 - pp. 3065-3074.
  3. Evans D.G. and Duan Xue Preparation of layered double hydroxides and their applications as additives in polymers, as precursors to magnetic materials and in biology and medicine // Chem. Comm., 2006 - pp. 485-496.

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