Preparation, characterization and optical properties of a novel azo-based chitosan biopolymer

The efficient procedure for preparation of azo-based chitosan biopolymer using chitosan and 2-(4-dimethylaminophenylazo)benzoic acid (methyl red) in isopropyl alcohol under mild condition has been demonstrated. After the reaction, the product was successively washed with an isopropyl alcohol and water mixture (5:1, v/v) and dried in air. Finally, the obtained product was confirmed and characterized by UV–Vis, FTIR, 1H NMR spectroscopy and XRD. The thermal, surface morphology and optical properties were evaluated by TGA, DSC, SEM, AFM, photoluminescence (PL) spectroscopy and second harmonic generation (SHG) studies. The maximum molar absorption coefficient (ɛmax), and correlation coefficient (r) were −0.0112 L mol−1 cm−1 and 0.998. Absorption of the derivative was high (104 cm−1) with optical band gap of 2.37 eV. The azo-based chitosan derivative may be considered as a novel optical material from biomedical application point of views.