Crystalline nanocellulose (CNC), one of the abundant materials
in nature, exhibits a left-handed chiral nematic organization that gives rise
to pronounced circular dichroism. This intrinsic chiroptical property enables
CNC-based structures to generate circularly polarized photoluminescence,
making them promising candidates for diverse photonic and optoelectronic
applications. In this study, we present a facile and scalable vacuum
filtration method for fabricating chiral CNC films with strong circular dichroism.
While pristine CNC exhibits both circular and linear dichroism, the latter
limits its function as an ideal circular polarizer. To address this, we
incorporated silica nanospheres into the CNC matrix, effectively suppressing
the linear diattenuation and enhancing the circular dichroic response. This
optimization led to a significant increase in photoluminescence dissymmetry,
with a maximum dissymmetry factor of 0.57 observed at 611 nm in a chiral
lasing device comprising dye-doped resist enclosed between CNC layers. Our
findings underscore the potential of this simple method in engineering
advanced chiroptical materials.