Nature-inspired construction of iridescent CNC/Nano-lignin films for UV resistance and ultra-fast humidity response.

Exploration of functional materials based on sustainable and renewable biomolecules has been of much interest. Herein, nature-inspired photonic films were proposed by incorporation of bio-based lignin nanoparticles (LNPs) into chiral nematic cellulose crystals (CNCs). Evaporation induced self-assembly (EISA) formed oriented and layered structure of the nanocomposites iridescent films with enlarged helix pitches by intercalation of higher amounts of LNPs. Decreased crystallite sizes and expanding layer gaps indicated the homogeneous distribution and hydrophobic interactions between CNCs and LNPs. Distinguished UV absorption capabilities with over 90 % shielding capabilities in UVB region and increased hydrophobicity with the contact angle of 75° were achieved for the composite films due to the presence of hydrophobic lignin. The proposed optical films also showed outstanding cytocompatibility owing to all-natural components introduced into the materials, which may display great potentials in many fields such as stimuli sensing, anti-counterfeiting and wearable devices.