Application of layered double hydroxides in sample pretreatment and enchantment of luminescence signal

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 , 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 host-guest 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.