Cellulose-based circularly polarized luminescence nanofilm with superior optical intensity and controllable direction

Synthesizing the circularly polarized luminescent (CPL) assemblies with strong intensity and real-time handedness direction control requires an ingenious structure design, which is difficult in traditional optical materials. This work utilizes the self-assembled cellulose nanocrystals (CNCs) as the chiral template and packages the luminophores into the platform, to design a kind of CPL nanofilm. By optimizing the photonic bandgap structure, it possesses a considerable CPL and superior mechanical flexibility, which makes it a candidate for the next generation of wearable sensing devices. Additionally, it displays the reversible optical response in the humidity- or ammonia gas-stimulus. Next, this work designs two CPL amplification strategies, divided into selective reflection design and optical pathway length optimization. The intensified dissymmetry factor (g_lum) has reached -1.39. Since, by simply tuning the sequence of two films, the handedness direction is successfully switched, with the inverted g_lum of approximately 0.4442. This dual-direction CPL intensity has preceded most cellulose-based chiral luminescent materials. Importantly, this optical design avoids the incorporation of external stimuli and disruption of the inner structure. At last, this photonic film with direction- and intensity-controllable is used in the photo-induced polymerization reaction and optical anti-counterfeiting areas.