Multiple stimuli-responsive circularly polarized luminescent bio-composite films by coassembling cellulose nanocrystals and curcumin

Cellulose nanocrystal (CNC) -based circularly polarized luminescent (CPL) materials, which are responsive to external stimuli, have attracted increasing attention in developing smart chiral photonic materials. In this study, chiral nematic bio-composite CNC films with right-handed (R-) CPL emission and tunable dissymmetry factors (g lum ) were prepared by encapsulating curcumin in chiral nematic CNC films via an evaporation-induced self-assembly strategy. The CPL active bio-composite CNC films exhibit multiple responsiveness to relative humidity (RH) and pH. It is noted that the pH response of the composite films is visualized, which is reflected in the variation of film colors, fluorescence, and CPL emission wavelengths. Additionally, with a hydrophobic treatment, the bio-composite CNC films exhibit enhanced water resistance and pH-responsive CPL in acid/base aqueous solutions. Based on the responsive circular polarization information, the bio-composite CNC films were developed as optical labels for multiple anti-counterfeiting applications. The reported environmentally friendly bio-composite CNC films provide a new reference for utilizing natural polysaccharides to build multi-mode responsive CPL materials.