When pursuing sustainable approaches to fabricate photonic structures, nature can be used as a source of inspiration for both the nanoarchitecture and the constituent materials. Although several biomaterials have been promised as suitable candidates for photonic materials and pigments, their fabrication processes have been limited to the small to medium-scale production of films. Here, by employing a substrate-free process, structurally coloured microparticles are produced via the confined self-assembly of a cholesteric cellulose nanocrystal (CNC) suspension within emulsified microdroplets. Upon drying, the droplets undergo multiple buckling events, which allow for greater contraction of the nanostructure than predicted for a spherical geometry. This buckling, combined with a solvent or thermal post-treatment, enables the production of dispersions of vibrant red, green, and blue cellulose photonic pigments. The hierarchical structure of these pigments enables the deposition of coatings with angular independent colour, offering a consistent visual appearance across a wide range of viewing angles.
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http://dx.doi.org/10.1038/s41467-022-31079-9 | DOI Listing |
Adv Sci (Weinh)
December 2024
Department of Industrial and Materials Science, Division of Engineering Materials, Chalmers University of Technology, Gothenburg, SE-412 96, Sweden.
Simultaneous rheological, polarized light imaging, and small-angle X-ray scattering experiments (Rheo-PLI-SAXS) are developed, thereby providing unprecedented level of insight into the multiscale orientation of hierarchical systems in simple shear. Notably, it is observed that mesoscale alignment in the flow direction does not develop simultaneously across nano-micro lengthscales in sheared suspensions of rod-like chiral-nematic (meso) phase forming cellulose nanocrystals. Rather, with increasing shear rate, orientation is observed first at mesoscale and then extends to the nanoscale, with influencing factors being the aggregation state of the hierarchy and concentration.
View Article and Find Full Text PDFSmall
December 2024
Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada.
Cellulose nanocrystals (CNCs) are known to self-assemble into a left-handed chiral nematic lyotropic liquid crystalline phase in water. When captured in the solid state, this structure can impart films with photonic properties that make them promising candidates in photonics, sensing, security, and other areas. Unfortunately, the intrinsic hydrophilicity of CNCs renders these iridescent films susceptible to moisture, thereby limiting their practicality.
View Article and Find Full Text PDFSmall
December 2024
State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
Currently, circularly polarized luminescence (CPL) has drawn wide interest in 3D display, information storage, and optical sensing. However, traditional synthetic paths are often accompanied by low chiral optical intensity and complex processes. Cellulose nanocrystals (CNCs), with the properties of liquid crystals, can spontaneously arrange into the left-handed layered nanofilm, which enables them candidates in the construction of CPL materials.
View Article and Find Full Text PDFMacromol Rapid Commun
December 2024
Department of Fibre and Polymer Technology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm, SE-100 44, Sweden.
Hydroxypropyl cellulose (HPC) is known for its ability to form cholesteric liquid crystalline phases displaying vivid structural colors. However, these vibrant colors tend to fade over time when the material dries. This issue is a major bottleneck to finding practical applications for these materials.
View Article and Find Full Text PDFNanophotonics
August 2024
School of Physical Science and Technology, Ningbo University, Ningbo, Zhejiang 315211, China.
Circularly polarized light emitting active materials are of great interest, and the convenient tuning of the circularly polarized luminescence (CPL) remains a significant challenge. Integrating fluorescent materials into chiral photonic crystals to achieve tunable CPL is a promising approach, allowing efficient manipulation of CPL by adjusting the photonic band gap (PBG). We combined carbon quantum dots (CQDs) with hydroxypropyl cellulose (HPC), which self-assembles into a cholesteric liquid crystal (CLC).
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