Properties and applications of biodegradable transparent and photoluminescent cellulose films prepared via a green process

Cellulose was dissolved rapidly in 7 wt% NaOH/12 wt% urea aqueous solution pre-cooled to −12 °C within 2 min to obtain its solution, which is a “green” process. A series of regenerated cellulose (RC) films were prepared from the cellulose solution via a simple and low-cost method to evaluate their structure and properties as packaging and functional materials. The cellulose films were treated successfully with fluorescent dyes and photoluminescent (PL) pigments to fabricate, for the first time, novel PL materials, which exhibited strong fluorescence and long after-glow emission. The results from CP/MAS 13C NMR spectra, X-ray diffraction and tensile testing confirmed that the transparent RC films possessed an homogenous structure, excellent optical transmittance (90% at 800 nm), as well as good tensile strength. Moreover, the drawing process could significantly improve their tensile strength, which reached 138 MPa. In addition, the biodegradation tests revealed that the RC films could be biodegraded completely. This work provided a non-toxic solvent system for the preparation of the packaging films and PL materials. This process is promising on a large scale and will maintain clean air in the production environment.