Sensitive chemoselectivity of cellulose nanocrystal films

Cellulose nanocrystals (CNCs) self-assembled into a chiral nematic structure film is an advanced platform for the fabrication of fascinating sensing, photonic and chiral nematic materials. Despite extensive progress in the functions of CNCs, their chemoselectivity has rarely been reported. Here, we exploit a brand-new perspective of CNCs in chemoselectivity, which shows sensitive selectivity even between isomers of monosaccharides and disaccharide by generating discernible crystal patterns. This sensitive selectivity of glucose homologs is attributed to the selective interaction of carbohydrate–carbohydrate, which enables the tune of the photonic properties and chiral mesoporous structures. Moreover, based on the chemoselectivity, chiral mesoporous structures with tunable specific surface areas are assembled from CNC suspensions and glucose homologs. We envision that the sensitive chemoselectivity of CNC films could provide insights into the recognition of carbohydrates and the preparation of mesoporous carbon in numerous practical applications.

Concentric chiral nematic polymeric fibers from cellulose nanocrystals

A cellulose nanocrystal liquid crystalline suspension was mixed with monomers and confined to a capillary tube. After photopolymerization, a fiber with a single-domain concentric chiral nematic structure throughout the length of the fiber was obtained.

Checkered Films of Multiaxis Oriented Nanocelluloses by Liquid-Phase Three-Dimensional Patterning

It is essential to build multiaxis oriented nanocellulose films in the plane for developing thermal or optical management films. However, using conventional orientation techniques, it is difficult to align nanocelluloses in multiple directions within the plane of single films rather than in the thickness direction like the chiral nematic structure. In this study, we developed the liquid-phase three-dimensional (3D) patterning technique by combining wet spinning and 3D printing. Using this technique, we produced a checkered film with multiaxis oriented nanocelluloses. This film showed similar retardation levels, but with orthogonal molecular axis orientations in each checkered domain as programmed. The thermal transport was enhanced in the domain with the oriented pattern parallel to the heat flow. This liquid-phase 3D patterning technique could pave the way for bottom-up design of differently aligned nanocellulose films to develop sophisticated optical and thermal materials.

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

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.

Sol-Gel Biotemplating Route with Cellulose Nanocrystals to Design Photocatalyst Boosting the Hydrogen Generation

<br> <div> <p>Light harvesting capability and charge carriers lifetime play critical roles in determining the photoefficency of photocatalyst. Herein, a one-pot method is proposed to design mesostructured TiO₂ materials by taking advantage of the ability of cellulose nanocrystals (CNC) to self-assemble into chiral nematic structures during solvent evaporation. After the xerogel formation, the as-obtained CNC/TiO₂ hybrid films exhibit a chiral nematic structure and tunable Bragg peak reflection, generating lamellar TiO₂ mesostructure after the biotemplate removal by calcination. More prominently, this straightforward method can be extended to couple TiO₂ with other metal oxides, improving the light-harvesting and charge carriers separation of these photocatalysts, in particular for boosting hydrogen generation. This foolproof approach opens new doors for the development of nanostructured materials for solar energy conversion and catalysis.<br></p></div>

Sol-Gel Biotemplating Route with Cellulose Nanocrystals to Design Photocatalyst Boosting the Hydrogen Generation

<br> <div> <p>Light harvesting capability and charge carriers lifetime play critical roles in determining the photoefficency of photocatalyst. Herein, a one-pot method is proposed to design mesostructured TiO₂ materials by taking advantage of the ability of cellulose nanocrystals (CNC) to self-assemble into chiral nematic structures during solvent evaporation. After the xerogel formation, the as-obtained CNC/TiO₂ hybrid films exhibit a chiral nematic structure and tunable Bragg peak reflection, generating lamellar TiO₂ mesostructure after the biotemplate removal by calcination. More prominently, this straightforward method can be extended to couple TiO₂ with other metal oxides, improving the light-harvesting and charge carriers separation of these photocatalysts, in particular for boosting hydrogen generation. This foolproof approach opens new doors for the development of nanostructured materials for solar energy conversion and catalysis.<br></p></div>