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Abstract: Development of a reliable and rapid process for synthesis of stable silver nanoparticles using nanocellulose is highly desired. In the present study, we report an efficient approach for the synthesis of stable silver nanoparticles (AgNPs) using dialdehyde cellulose nanocrystal (DACNC) as both reducing and stabilizing agent. The periodated cellulose nanocrystals (CNCs) were able to reduce silver ions to obtain cellulose nanocrystal-AgNPs (CNC-AgNPs) composites with high Ag percentage. The resulting composites were characterized by using UV-Vis spectroscopy, fourier infrared spectroscopy (FT-IR), X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). Furthermore, their antimicrobial activities were investigated. The formation of AgNPs was evidenced by the surface plasmon resonance peak at around 400 nm. XRD data showed diffraction peaks at 2θ 38.33º, 44.55º, 64.27º, 77.66º, which can be indexed to (111), (200), (220), (311), and (222) planes of pure silver, indicating the successful synthesis of silver nanoparticles. The TEM images of CNC-AgNPs showed spherical AgNPs with sizes from several nanometers to 30 nm on the cellulose nanocrystal surfaces. The composites showed high antibacterial activities against Escherichia coli and Staphylococcus aureus. When the CNC-AgNPs was added into the pulp fibers, the obtained handsheets also displayed strong antibacterial activities with higher strength properties and a lower air permeability, indicating potential applications in food packaging materials.Graphical abstract: [ABSTRACT FROM AUTHOR]

In this study, the base film (CSL) was prepared by blending tunicate cellulose nanocrystals (TCNCs) extracted from tunicate shells, with sodium alginate (SA) and alkali lignin (AL). Then, the mulching film (CSL-WK) was prepared using water-borne polyurethane (WPU) as binder to install low-energy Kaolin on the surface of CSL film. The influences of composition with different concentrations on mechanical properties were studied. The tensile strength and elongation at break of CSL-WK film could reach 86.58 MPa and 50.49 %, respectively. The mulching films were characterized by degradability test, SEM, FTIR, and TGA. TCNCs had good compatibility with SA and AL, and a rough structure was formed on the surface of the film to improve the hydrophobicity. The barrier properties, including ultraviolet resistance, water contact angle, water vapor permeability, water retention, and flame retardancy, were tested. The results showed that CSL-WK films could block 97 % of ultraviolet light, reduce about 25 % of soil water loss, and self-extinguish within 7 s of open flame ignition. Note that the secondary spraying method significantly improved the barrier property of films. This study lays a foundation for the preparation of ecologically friendly, biodegradable, and high barrier mulching film, and expands the application of marine resources. • The shells of the tunicates were firstly used to prepare mulching films. • Multiple biomass materials were used to prepare high barrier mulching film materials. • The film has excellent UV resistance, water vapor barrier, and flame retardancy. • The mechanical strength and barrier properties were improved by spraying process. • High b biomass mulch supports environmentally friendly agricultural practices. [ABSTRACT FROM AUTHOR]

Cellulose nanocrystal (CNC) hybrid materials with numerous optical states have great potential as anti-counterfeiting labels and information encryption materials. However, it is challenging to construct multicolor emitting materials with tunable behaviors, which can dramatically enhance anti-counterfeiting abilities. Here, free-standing composite films with vivid multi-structural colors and dual-emitting fluorescence are successfully fabricated through a host-guest coassembly strategy. The lanthanide complex and an aggregation-induced emission molecule (tetraphenylethylene derivative, TPEC) are selected as luminescent guests, which are integrated into the chiral nematic structure of CNCs. The obtained photonic films display broadband reflection across the visible spectrum, which may be attributed to the chiral nematic domains with variations in the helical pitches and helical axis orientations. Under 254 nm excitation, the film exhibits bright red emission, while blue–green emission switching occurs under 365 nm excitation. The broad reflection band of the film covers both the green and red fluorescent emission centers, and right circularly polarized luminescence emission with different dissymmetry factors is produced due to the selective reflection of the left chiral nematic structure. A large glum value up to −0.21 at 600 nm was realized. Additionally, CNC-based materials with tailored shapes are further used in anti-counterfeit tags and decorative applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Aerogels with chiral nematic structure are promising candidates for structural coatings and optical devices. Cellulose nanocrystals (CNCs) are excellent photonic building blocks for the fabrication of chiral nematic aerogels. Conventional bottom-up fabrication process usually is complicated, energy and time consumption. Herein, a simple method for fabricating CNCs and polyethylene glycol (PEG) based foams with chiral nematic structure was proposed. After CNCs-PEG based solid films were swollen with N-methylmorpholine N-oxide (NMMO) aqueous solutions, the obtained hydrogels were freeze-dried, resulting in chiral nematic foams. During the process, both macropores and mesopores were created with chiral nematic phase retained inside foam walls. Owning numerous macropores and chiral nematic walls of varying axial directions, the chiral nematic foams exhibited a broad-band reflection phenomenon. Moreover, the representative Titanium diisopropoxide(bis-2,4-pentanedionate) was permeated into foam walls, and transformed into chiral nematic TiO 2 foams after annealing. We envisage that the chiral nematic foams may have a promising application in the fields of chiral separation or chiral catalysis. A simple method is proposed to fabricate CNC-based foams with chiral nematic structure. CNC-based films are first swollen with a good solvent of cellulose. Then swollen CNC films are freeze-dried. The resultant chiral nematic foams exhibit a wide-band reflection phenomenon. Chiral nematic TiO 2 foams can be constructed by using CNC-based foams as a template. [Display omitted] • A simple method is proposed to fabricate cellulose nanocrystals (CNCs)-based foams with chiral nematic structure. • The obtained chiral nematic foams exhibit a wide-band reflection phenomenon. • Chiral nematic TiO 2 foams can be constructed by using CNCs-based foams as a template. [ABSTRACT FROM AUTHOR]

Chiral nematic papers (CNPs) with mesopores structure based on cellulose nanocrystals (CNCs) were fabricated successfully via a swelling and freeze-drying method. The order of the original chiral nematic cellulose nanocrystals film was preserved in CNPs, which was proved by scanning electron microscopy (SEM), polarized optical microscopy (POM) measurements and circular dichroism (CD) spectra. The CNPs exhibited excellent optical responsive properties to different solvents. Inspired by this feature, a colorable ink containing amounts of gel particles was prepared by pulverizing CNPs/water mixture into a suspension. Patterns written in suspension ink with various colors can be formed when soaked with different solvents. Moreover, CNPs displayed an irreversible color response to compression. Additionally, the hydrophilicity of CNPs was tuned by polyethyleneimine. Modified CNPs exhibited different colors under the identical solvent environment when compared to the original one. Aqueous PEI can be used as an ink to depict responsive photonic patterns on CNPs. Iridescent chiral nematic papers (CNPs) with mesopores structure exhibit excellent optical responsive properties to mixed solvents. Modified CNPs with polyethylene imine (PEI) display different colors under the identical solvent environment when compared to the original one. Aqueous PEI can be used as an ink to depict responsive photonic patterns on CNPs. [Display omitted] [ABSTRACT FROM AUTHOR]

A convenient strategy is proposed to fabricate chiral nematic composite films by intercalating cationic poly(ethylene imine) into the swollen matrix of self-assembled cellulose nanocrystal films. The composite films exhibit an extremely high folding endurance. Moreover, the composition also leads to a fluorescence enhancement effect, endowing the films with circularly polarized luminescence and optical responsiveness. [Display omitted] • Circularly polarized luminescence (CPL) CNC composite films are fabricated by matrix swelling and in-situ insertion method. • The composite CNC films exhibit extremely high folding endurance and solvent resistance. • The CPL handedness and dissymmetry factors of the composite films can be controlled. • Application in anti-counterfeiting patterns is demonstrated. Cellulose nanocrystal (CNC)-based materials have gained increasing attention because of their great potential applications in optical devices, anticounterfeiting and structural coatings. However, due to the inherent brittleness of CNC, fabricating highly strong and solvent-resistant CNC derived materials is still an important and challenging task. Here, a straightforward, matrix swelling and in-situ insertion method is developed to fabricate chiral nematic composite films by intercalating poly(ethylene imine) (PEI) into the as-prepared swollen matrix of CNC films. The resulting composite CNC films exhibit a great increase in ultimate strain and toughness and especially have an extremely high folding endurance. Notably, the intercalation of PEI into CNC films also leads to a fluorescence enhancement effect, which endows the films circularly polarized luminescence (CPL) properties. The CPL handedness and dissymmetry factors (glum) of the composite films can be controlled. Furthermore, the CNC composite films display optical responsiveness (structure color, fluorescence intensity) to various stimuli, including ethanol and formaldehyde environments. We expect the current in-situ intercalation technique to be promising in manufacturing foldable encryption materials. [ABSTRACT FROM AUTHOR]

• Aqueous NMMO is used to modify cellulose nanocrystal photonic films. • CNC photonic films can be swollen by NMMO and show red-shifted color. • NMMO-treated CNC films display reversible responsive colors to humidity changes. • Aqueous NMMO is used as an ink to depict responsive photonic patterns on CNC films. A type of cellulose solvent, i.e., aqueous N -methylmorpholine- N -O xide (NMMO) solutions, was used to modify cellulose nanocrystal (CNC) photonic films. CNC films can be swollen by NMMO, resulting in red-shifted reflected colors. The swelling effect is supposed to come from NMMO permeation into the crystalline regions of individual CNCs and intercalating in between CNC particles. When NMMO was removed, the reflected colors of CNC films blue shifted because of the reduced helical pitches. NMMO-treated CNC films display reversible responsive colors to humidity changes in several minutes. Increasing NMMO content allows CNC films to enlarge the responsive color range. Aqueous NMMO can be used as an ink to depict responsive photonic patterns on CNC films. This post-treatment approach to producing responsive colors and photonic patterns in CNC films may be applied to the areas of sensor, anti-counterfeiting, and decoration. [ABSTRACT FROM AUTHOR]