| Abstract
| - The objective of this work is the intercalation of the cationic biopolymer chitosan in Na+−montmorillonite, providing compact and robust three-dimensional nanocomposites withinteresting functional properties. CHN chemical analysis, X-ray diffraction, Fourier transforminfrared spectroscopy, scanning transmission electron microscopy, energy-dispersion X-rayanalysis, and thermal analysis have been employed in the characterization of the nanocomposites, confirming the adsorption in mono- or bilayers of chitosan chains depending on therelative amount of chitosan with respect to the cationic exchange capacity of the clay. Thefirst chitosan layer is adsorbed through a cationic exchange procedure, while the secondlayer is adsorbed in the acetate salt form. Because the deintercalation of the biopolymer isvery difficult, the −NH3+Ac- species belonging to the chitosan second layer act as anionicexchange sites and, in this way, such nanocomposites become suitable systems for thedetection of anions. These materials have been successfully used in the development of bulk-modified electrodes exhibiting numerous advantages as easy surface renewal, ruggedness,and long-time stability. The resulting sensors are applied in the potentiometric determinationof several anions, showing a higher selectivity toward monovalent anions. This selectivitybehavior could be explained by the special arrangement of the polymer as a nanostructuredbidimensional system.
- The intercalation of a chitosan bilayer in Na+−montmorillonite through cationic exchange and hydrogen-bonding processes turns the resulting nanocomposite into an anionic exchanger, applied in the development of potentiometric sensors that show a remarkable selectivity toward monovalent anions due to the special arrangement of the biopolymer as a nanostructured bidimensional system.
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