Stimuli-responsive circularly polarized luminescence with chiroptical amplification and inversion enabled by cholesterically assembled bio-materials

Dynamic control of circularly polarized luminescence (CPL), including modulation of intensity, wavelength, and chirality, is critical for the development of smart materials capable of responding to environmental changes. The responsive chiroptical materials with high dissymmetry factors (glum-factors) are particularly crucial for advancements in 3D optical devices, chiral sensors, and anti-counterfeiting technologies. In this work, we successfully fabricated a CPL active bio-material through incorporating cholesterically assembled cellulose nanocrystals (CNCs) with organic dye, fluorescein isothiocyanate (FITC), achieving a tunable glum-factor ranging from -0.30 to 0.04. Dynamic modulation of CPL properties, including CPL signal enhancement and inversion, is achieved, regulated by the interplay of the relative position between the photonic band gap of CNC films and the fluorescence emission spectra under varied pH conditions. Moreover, such switchable CPL properties were reversible under alternating pH treatments. Potential applications in security materials have been demonstrated by fabricating such bio-materials with adaptive CPL response. CPL active materials with a tunable glum-factor, from -0.30 to 0.04, were fabricated by incorporating responsive organic dye into cellulose nanocrystals. Such films showed dynamic switchable CPL signal in intensity and handedness at different pH.