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Abstract
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Layered double hydroxides (LDHs) are a class of synthetic two dimensional nano-structured
inorganic materials that have positively charged layers of metal hydroxides, between which are
located anions and, in general, some water molecules. The general formula of LDHs can be
represented by
ƒy ƒy ƒy ƒ{ ƒ{
ƒ{
x
2
n
x / n
x
2
3
x
2
1 x [M M (OH) ] [A . mH O] , where M2+ is a divalent cation; M3+ is a
trivalent cation; An- is an interlayer anion; x value is equal to the molar ratio (M3+)/(M2+ + M3+),
and m is the number of water molecules located in the interlayer region together with anions. The
electrostatic interactions and hydrogen bonds between layers and contents of the gallery hold the
layers together, forming a three dimensional structure [1,2]. LDHs are of great interest for nano
materials science and technology due to their special structural and unique applications. Despise
of other applications, LDHs are potentially good adsorbents for a diverse number of anions because
of their permanent layer positive charge, high anion-exchange capacity, large surface area, good
thermal stability and water resistant structure. Moreover, due to create inorganic-organic hostguest
hybrid nanostructures, in recent years the use of LDHs as host materials has become of
increasing interest. LDH matrix provides special structure for intercalated fluorophores such as
immobilization of fluorophore in a stable environment improving fluorescence efficiency and
optical stability of the fluorophore [3, 4]. In this paper, application of layered double hydroxides
in solid-phase extraction of several organic and inorganic anions from environmental, biological
and food samples along with the role of layered double hydroxides on luminescence signal
enchantment have been discussed.
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