Synthesis, characterization, and properties of antibacterial dye based on chitosan

A new low-molecular-weight antibacterial dye was obtained by reaction of Reactive Blue 19 and chitosan previously hydrolyzed with H₂O₂. The compounds were characterized by Fourier-transform infrared spectroscopy, ¹³C solid-state nuclear magnetic resonance, X-ray photoelectron spectroscopy, X-ray diffraction analysis, and antibacterial, solubility, and dyeing performance tests including color difference and fastness. The results show that chitosan dyes were generated with covalent bonds between carbon and nitrogen atoms via reaction of alkene group of dye and primary amine group of chitosan. According to solubility tests, the solubility of the chitosan dye was controlled by the molecular weight of chitosan. In addition, compared with Reactive Blue 19, the antibacterial property of the chitosan dye was increased against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Besides, chitosan dye demonstrated better lightfastness and waterfastness than the original dye. Therefore, chitosan dye provides a new perspective for improving decorative and antimicrobial properties of wood products.