Photonic Properties and Applications of Cellulose Nanocrystal Films with Planar Anchoring

Saha, Partha; Davis, Virginia A.

doi:10.1021/acsanm.8b00233

Cited by 41 publications

(59 citation statements)

References 50 publications

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“…High-magnification images exhibited glossy microscopic surface along the wrinkles, implying the planar anchoring of CNC at the PDMS interface during evaporation ( Figure 3C, inset). 35 Moreover, the orientation of individual CNCs inside the PDMS microgrooves was confined and highly aligned in linear arrangement ( Figure S13), in agreement with a previous report. 36 At fractures perpendicular to the CWF surface, we observed a porous twisted layered structure with the CNC director rotated in a counter-clockwise direction ( Figure 3D, 3E and S14), which gave rise to the cholesteric structure responsible for the selective reflection of light.…”

Section: Resultssupporting

confidence: 91%

Printing Flowers? Custom-Tailored Photonic Cellulose Films with Engineered Surface Topography

Chu

Camposeo

Vilensky

et al. 2019

Matter

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Wrought by nature's wondrous hand, surface topographies are discovered on all length scales in living creatures and serve a variety of functions. Inspired by floral striations, here we developed a scalable means of fabricating custom-tailored photonic cellulose films that contained both cholesteric organization and microscopic wrinkly surface topography. Free-standing films were prepared by molding cellulose nanocrystal ink onto an oriented wrinkled template through evaporation-assisted nanoimprinting lithography, yielding morphology-induced light scattering at a short wavelength as well as optically tunable structural color derived from the helical cellulose matrix. As a result, the interplay between the two photonic structures, grating-like surface and chiral bulk, led to selective scattering of circularly polarized light with specific handedness. Moreover, the wrinkled surface relief on cholesteric cellulose films could be precisely controlled, enabling engineered printing of microscopic patterned images.

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Section: Resultssupporting

confidence: 91%

Printing Flowers? Custom-Tailored Photonic Cellulose Films with Engineered Surface Topography

Chu

Camposeo

Vilensky

et al. 2019

Matter

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“…From these latter images, it is perceptible that this type of texture becomes more noticeable as the content of HPC in the composite films increases. If fingerprints are visible with POM this means that the helical axis of the chiral nematic arrangement was not completely aligned perpendicular to the film surface, hence a complete planar alignment was not achieved [13]. Since, the effect is even more noticeable when the content of HPC in the composite mixture increases, it can be assumed that the presence of HPC somehow lowers the concentration at which the glassy state or kinetic arrest occurs.…”

Section: Resultsmentioning

confidence: 99%

“…Moreover, when 3.3 wt.% of HPC is introduced in the colloidal suspension, a reduction of 4 μm in the pitch value is observed (comparing with the system with 2.2 wt.% of HPC); however, this value is still a higher value than the one observed for the neat CNCs colloidal suspension. The structural colouration observed in the CNCs films has been related to several parameters that influence the colloidal suspension as, for example: CNCs concentration; ionic strength [3]; energy given with ultrasonic treatment [9]; exposure to magnetic field [10] or electric field [11] and the drying rate of the solvent [12] combined with planar anchoring [13]. Although these interesting studies allow us to obtain iridescent CNCs films, due to their crystalline nature, they present low mechanical strength (highly brittle), which can restrict their range of application.…”

Section: Introductionmentioning

confidence: 99%

Flexible and Structural Coloured Composite Films from Cellulose Nanocrystals/Hydroxypropyl Cellulose Lyotropic Suspensions

et al. 2020

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Lyotropic colloidal aqueous suspensions of cellulose nanocrystals (CNCs) can, after solvent evaporation, retain their chiral nematic arrangement. As water is removed the pitch value of the suspension decreases and structural colour-generating films, which are mechanically brittle in nature, can be obtained. Increasing their flexibility while keeping the chiral nematic structure and biocompatible nature is a challenging task. However, if achievable, this will promote their use in new and interesting applications. In this study, we report on the addition of different amounts of hydroxypropyl cellulose (HPC) to CNCs suspension within the coexistence of the isotropic-anisotropic phases and infer the influence of this cellulosic derivative on the properties of the obtained solid films. It was possible to add 50 wt.% of HPC to a CNCs aqueous suspension (to obtain a 50/50 solids ratio) without disrupting the LC phase of CNCs and maintaining a left-handed helical structure in the obtained films. When 30 wt.% of HPC was added to the suspension of CNCs, a strong colouration in the film was still observed. This colour shifts to the near-infrared region as the HPC content in the colloidal suspension increases to 40 wt.% or 50 wt.% The all-cellulosic composite films present an increase in the maximum strain as the concentration of HPC increases, as shown by the bending experiments and an improvement in their thermal properties.

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“…In addition, domains with disclinations and line defects caused by the difference in Ch pitches between adjacent regions were observed in the cross‐sectional SEM image of the M2 film (Figure d). Line defects in CNC films have been previously attributed to varying pitches in adjacent domains . Other possible origins of the broadband CD peak could originate from the presence of domains with different orientation of helical axes, as shown in the cross‐sectional SEM images of the M2 film (Figure S9, Supporting Information).…”

Section: Expanding the Spectral Range Of Polarization Rotationmentioning

confidence: 88%

Hybrid Cholesteric Films with Tailored Polarization Rotation

Rofouie

Galati

Sun

et al. 2019

Adv Funct Materials

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Incorporation of metal nanoparticles in chiral (Ch) films of cellulose nanocrystals (CNCs) enhances nanoparticle plasmon resonances, due to the coupling of the intrinsic properties of the plasmonic guest and the photonic properties of the Ch-CNC host. In contrast with previous reports, the properties of the Ch-CNC host are focused and an effective strategy is developed for tuning the optical polarization rotation of the composite films formed by the CNCs and gold nanoparticles. A twofold enhancement in the polarization rotation power of the composite Ch-CNC films, with an insignificant change in the incurred optical losses, is achieved by varying the density and dimensions of gold nanoparticles embedded in the Ch-CNC films. For such films, a new approach is developed to obtain broadband circular dichroism by fabricating films from mixtures of CNC suspensions ultrasonicated for different time intervals. These new findings enable fine-tuning of the power and spectral range of the polarization rotation and offer a novel strategy for the fabrication of broadband reflectors and polarizers, smart solar windows, and detectors for circularly polarized light.

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Photonic Properties and Applications of Cellulose Nanocrystal Films with Planar Anchoring

Cited by 41 publications

References 50 publications

Printing Flowers? Custom-Tailored Photonic Cellulose Films with Engineered Surface Topography

Printing Flowers? Custom-Tailored Photonic Cellulose Films with Engineered Surface Topography

Flexible and Structural Coloured Composite Films from Cellulose Nanocrystals/Hydroxypropyl Cellulose Lyotropic Suspensions

Hybrid Cholesteric Films with Tailored Polarization Rotation

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