Polymer induced fluorescence enhancement effect on luminescent chiral nematic cellulose nanocrystal based materials

Strong and tailored circularly polarized luminescence (CPL) from fluorophores embedded in chiral matrices has gained significant interest in photonic technologies. However, fluorescence quenching due to molecule aggregation occurs in the solid state at high fluorophore loading. Here, we present a simple polymer induced fluorescence enhancement strategy to fabricate robust luminescent films composed of cellulose nanocrystal (CNC) and rhodamine 6G (Rh6G). The type, molecule weight, and concentration of the polymer are found to play critical roles in modulating film fluorescence. The results demonstrate that polymer effectively migrates fluorescence quenching by shielding interactions between Rh6G molecules and CNC-Rh6G, leading to a remarkable enhancement of up to 47 times. The left-handed chiral nematic structure of CNCs can transform the Rh6G emission into controllable left or right-handed CPL. By adjusting the polyethylene glycol concentration and photonic band gap of composite films, CPL with tunable handedness, intensity, and wavelength are achieved, yielding a dissymmetric factor ranging from -0.35 to 0.14. This polymer induced fluorescence enhancement and tunable CPL highlight the potential of CNC-based luminescent films for advanced functional materials.