Designable Multiple Structural Colors Using Alkaline Periodate Oxidated Cellulose Nanocrystals and Gold Nanorods

Structural colors originating from ordered microstructures are popularly applied due to their versatile intrinsic advantages compared to dyes/pigments. Since the emergence of cellulose nanocrystals (CNCs) via alkaline periodate oxidation (PO‐CNCs) in 2019, here, their great potential as one‐dimensional nanomaterials for tunable optical materials combining with gold nanorods (GNRs) for the first time is demonstrated. The hybrid nanocomposite films with embedded and well‐organized PO‐CNCs and/or GNRs were prepared from hydrogel precursors after uniaxial stretching and air drying. In comparison with the solitary films containing pristine PO‐CNCs or GNRs, the birefringence of PO‐CNCs and surface plasmon resonance of GNRs synergistically expands the resulting color space. Based on their contributions, the solitary films containing only PO‐CNCs or GNRs can be stacked for widely spanning structural colors, such as red, green, and blue colors. Moreover, the relative angle between the stacked films can also be varied to manipulate the structural colors, providing a flexible method to construct designable optical materials. In brief, this study provides a general strategy for combining PO‐CNCs and GNRs into a novel series of nanocomposite materials and demonstrates their promising application potential in optics.