Xerogel Films with Ordered Silica Nanorods Enable Fine‐Tuned Polarized Structural Colors in Modular Nanocomposite Films

Abstract The demand for polarized structural color materials with specific optical properties drives the advancement of nanostructure‐based color generation composites. Here, a facile stretched and air‐dried hydrogel strategy is employed to synthesize xerogel films with uni‐directionally aligned silica nanorods (SNs) for constructing polarization‐dependent structural colors. These silica xerogel films exhibit delicate color changes under a polarized microscope, which is attributed to the inherent birefringence of SN ≈700 nm in length. In the previous works, a modular stacking strategy is employed by combining films containing gold nanorods (GNRs), which exhibit surface plasmon resonance (SPR) effects, with films incorporating cellulose nanocrystals (CNCs) that produce optical retardation and interference colors due to birefringent properties. SN films exhibit a relatively low birefringence value, allowing precise tuning of the overall birefringence in the stacking strategy. The multilayer configurations can exhibit a wide range of linearly polarized color variations, including green and purple hues, by stacking and adjusting stacking angles of GNR and SN films, or GNR, CNC, and SN films. This work offers a film containing directionally aligned SN that can be utilized in the film's stacked configuration strategy to achieve refined structural color tuning, thereby expanding the potential of hybrid nano‐structural films in specific optical applications.