Eco-friendly chitosan Schiff base as an efficient sensor for trace anion detection

Herein, a chitosan Schiff base sample (CSAN) was strategically designed and prepared via a two-step process. In the first step, an azo derivative of 1- naphthylamine namely, [2-hydroxy-5-(naphthalene-1-yldiazenyl) benzaldehyde] (HNDB) was synthesized as an aldehyde moiety. Then the condensation reaction of HNDB with chitosan afforded CSAN as the target product. Structural analyses of synthesized material were accomplished through FT-IR, ¹H NMR, UV-Vis, XRD, TGA, and SEM spectral methods. Meanwhile, the heterogeneous CSAN was able to detect the presence of hydrogen carbonate (HCO₃^-), acetate (AcO^-), and cyanide (CN^-) anions in semi-aqueous media (H₂O/DMSO; 10:90%, v/v). Moreover, the selectivity of CSAN towards CN^- anion was increased through variation in solvent mixture ratios. Thereupon, CSAN was explored as a promising sensor towards CN^- anion in an aqueous media through considerable color variation from colorless to pale yellow as well as quantitative chemical analysis. Overall, reliable CSAN chemosensor with high sensitivity for mentioned anions has a pivotal role in practical applications owing to it's reversibility ability.