LAUSR

Incorporation of metal nanoparticles in chiral (Ch) films of cellulose nanocrystals (CNCs) enhances nanoparticle plasmon resonances, due to the coupling of the intrinsic properties of the plasmonic guest and the photonic properties of the Ch‐CNC host. In contrast with previous reports, the properties of the Ch‐CNC host are focused and an effective strategy is developed for tuning the optical polarization rotation of the composite films formed by the CNCs and gold nanoparticles. A twofold enhancement in the polarization rotation power of the composite Ch‐CNC films, with an insignificant change in the incurred optical losses, is achieved by varying the density and dimensions of gold nanoparticles embedded in the Ch‐CNC films. For such films, a new approach is developed to obtain broadband circular dichroism by fabricating films from mixtures of CNC suspensions ultrasonicated for different time intervals. These new findings enable fine‐tuning of the power and spectral range of the polarization rotation and offer a novel strategy for the fabrication of broadband reflectors and polarizers, smart solar windows, and detectors for circularly polarized light.