Fluorescent cellulose films with pH response and polarized emission

As one of the most abundant renewable and biodegradable materials in nature, cellulose is difficult to dissolve in common organic and inorganic liquids. Here, a series of regenerated cellulose films were prepared by using a specific tetra-butylammonium hydroxide TBAH/H2O/DMSO ternary solvent system. Especially, the fluorescent cellulose film was obtained successfully via a ring-opening grafting reaction between a modified fluorescein molecule with 3-expoxypropoxy and cellulose. The fluorescent cellulose films exhibited excellent fluorescence stability and pH sensitivity to the aqueous solutions with different degree of acid and alkaline. Moreover, the anisotropic fluorescein cellulose film was obtained for the first time by stretching and further drying the initial fluorescence cellulose hydrogel, and displayed a novel polarized emission. This work provided a simple, low-cost and environment-friendly pathway to fabricate fluorescent cellulose films, showing potential applications in packaging, decoration materials and other functional materials such as anti-counterfeiting paper.