| Abstract
| - The intercalation by the co-organized assembly method of natural anionic polysaccharides, including alginic acid, pectin, κ-carrageenan, and ι-carrageenan, in layered double hydroxides, provides nanocomposites in which the anionic exchange behavior of the pristine LDH is reversed to a cationic exchange capacity. Potentiometric sensors based on such biopolymer−[Zn2Al] nanocomposites exhibit good responses in calcium ion determination.
- A new family of functional hybrid nanocomposites based on the intercalation of naturally occurringanionic biopolymers including alginic acid, pectin, κ-carrageenan, ι-carrageenan, and xanthan gum in[Zn2Al(OH)6]Cl·nH2O layered double hydroxide (LDH), have been synthesized. The “coprecipitation”or “co-organized assembly” method has been successfully employed for the intercalation of suchpolysaccharides within the [Zn2Al] LDH. However, the “reconstruction” procedure from the calcinedLDH in the presence of the anionic polysaccharides only resulted in a partial intercalation of the organicguest. Particular effort was devoted to the study of ι-carrageenan−[Zn2Al] systems. An essential featureof the prepared biopolymer−[Zn2Al] nanocomposites is that the anionic exchange capacity of the pristineLDH is turned into a cationic exchange capacity due to negatively charged groups in the polysaccharidestructure that do not interact with the positively charged LDH layers. In agreement with the fact thatmost of the studied biopolymers interact strongly with calcium ions producing homogeneous gels, theprepared biopolymer−[Zn2Al] nanocomposites were operative as active phases of sensors for therecognition of calcium ions. Hence, the biopolymer−[Zn2Al] nanocomposites have been incorporated incarbon paste or PVC matrixes for the development of potentiometric sensors. These devices were appliedto calcium determination by direct potentiometry and the best responses were obtained for the sensorsbased on alginate−LDH and ι-carrageenan−LDH nanocomposites.
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