Chemical Functionalization of Cellulose Fabric for the Incorporation of Photosensitive Dyes: Optimization of Functionalization for the Grafting of Rose Bengal

This study presents an optimized method for grafting the photosensitive dye Rose Bengal onto cellulosic fabric to develop functional textile materials with photoactive properties. The two-step approach involved tosylation of hydroxyl groups followed by nucleophilic azidation under varying conditions of temperature (40-80°C), reaction time (20-60h), sodium azide concentration (5-30 equivalents), and solvent volume (1.5-4mL of DMF). Optimal azidation conditions-20 equivalents of NaN<sub>3</sub> in 3mL DMF at 60°C for 40h-yielded an azide-functionalized cellulose (Cell-AZo) with 8.75% nitrogen content and a degree of substitution (DS) of 0.4, indicating functionalization at approximately four C6-OH groups per ten glucose units. The Cell-AZo substrate was subsequently grafted with a propargyl-esterified derivative of Rose Bengal through copper-catalyzed azide-alkyne cycloaddition (CuAAC), producing a photoreactive cellulose fabric (Cell-RBe). Spectroscopic characterization using FT-IR showed the appearance of ester (1738cm<sup>-1</sup>) and aromatic (1546cm<sup>-1</sup>) bands, confirming the presence of the dye, while the disappearance of the azide signal (~2100cm<sup>-1</sup>) validated reaction completion. XPS analyses revealed the presence of Cl and I from Rose Bengal and triazole N1s binding energy peaks (400.3 and 402.0eV), confirming covalent attachment. The functionalized fabric preserved structural integrity while introducing chromophoric groups, demonstrating the viability of this chemical strategy for producing smart textiles. The method's scalability and compatibility with aqueous processing open perspectives for sustainable applications in antimicrobial textiles, photocatalytic supports, and optoelectronic devices.