A study on the synthesis and anion recognition of a chitosan-urea receptor

A new chitosan based colorimetric anion receptor bearing nitrophenyl as a chromogenic signal group, and urea moiety as recognition site was designed and synthesized. The receptor structure was characterized by FTIR and ¹H NMR. The sensing abilities of the receptor for anions were investigated with UV-vis methods. During the addition of PO₄^3- and F^- anions, the sensor responded with a dramatic color change, and no change was observed in the presence of other anions. The UV-vis absorption titration data showed that the receptor shows selective recognition and sensing in DMSO-H₂O (1%) for PO₄^3- and F^- anions. The Job's curve showed that 3:2 stoichiometry complexes were formed between the receptor and the anion.