Hierarchical nanostructures found in nature, such as plants or insects are the organization of bio-derived photonic building blocks. Structural colors, which result from the scattering, interference, and diffraction of light with periodic dielectric materials with feature sizes comparable to the visible-light wavelength, are prevalent in the biological world. Some of them are spatially assembled to form a chiral organization with interesting circular dichroism (CD). These suggest that self-assembled biological structures are worth exploring to optimize a design of synthetic chiral optical materials for novel artificial photonic materials with a wide range of applications, including CPL-photodetectors , CP-LEDs , bioresponsive imaging, 3D displays, as well as applications in quantum computing, quantum communication , non- volatile- memory devices and spintronics.

Cellulose nanocrystals (CNCs) are well-known biosourced materials that form a cholesteric liquid crystal.  These renewable natural nanocrystals can be easily obtained from wood and typically have a diameter of ~3 - 5nm and length ~100 - 200nm.  It can provide photonic building blocks with a chiral nematic phase above a critical concentration via evaporation-induced self-assembly process without complicated design and additional technique. These chiral nematic phase of CNCs are still maintained in solid state. In each layer parallel to the surface plane, CNCs are aligned in the same direction, while the alignment direction of the adjacent layer is rotated clockwise by a small angle. The continuous rotation of the alignment direction creates photonic properties in periodical helical organization with specific pitch distance comparable to the wavelength of visible light, leading to the formation of vertical one-dimensional photonic crystals with strong Bragg reflection.  Manipulating the helical pitch in cholesteric liquid phase can control the reflected wavelength, caused by Bragg’s light reflection over broad visible range with appearance of bright structural colors by adjusting many parameters, such as pH, ionic strength, temperature, other dopants, and particle size.

Integrating optically active synthetic components into chiral nematic CNC films has been recently reported to generate intriguing optical functionalities via host-guest co-assembly for realizing various applications including soft actuator, sensors, chiral luminescence, and etc.

In this presentation, the design for chiral nematic CNC composite films with synthetic optical components will be introduced for constructing artificial biophotonic structure with various functionalities, such as stimuli-responsive films, CPL emission, and CPL photodetectors.