In situ Electrical Impedance Tomography for Visualizing Water Transportation in Hygroscopic Aerogels

The global water crisis demands immediate attention, and atmospheric water harvesting (AWH) provides a viable alternative. However, studying the real-time subtle relationship between water absorption, diffusion, and internal structure for hygroscopic materials is challenging. Herein, a dynamic visualization technique is proposed that utilizes an in situ electrical impedance tomography (EIT) system and a precise reconstruction algorithm to achieve real-time monitoring of the water sorption process within aerogels from an internal microstructural perspective. These results can be inferred that composites' pore sizes affecting the kinetics of their moisture absorption. In addition, the diffusion path of moisture absorption and the distribution of stored moisture inside aerogels exhibit intrinsic self-selective behavior, where the fiber skeleton of the aerogel plays a crucial role. In summary, this work proposes a generic EIT-based technique for the in situ and dynamic monitoring of the hygroscopic process, pointing to an entirely new approach regarding research on AWH materials.

Tunable Construction of Chiral Nematic Cellulose Nanocrystals/ZnO Films for Ultra-Sensitive, Recyclable Sensing of Humidity and Ethanol

The investigation of functional materials derived from sustainable and eco-friendly bioresources has generated significant attention. Herein, nanocomposite films based on chiral nematic cellulose crystals (CNCs) were developed by incorporating xylose and biocompatible ZnO nanoparticles (NPs) via evaporation-induced self-assembly (EISA). The nanocomposite films exhibited iridescent color changes that corresponded to the birefringence phenomenon under polarized light, which was attributed to the formation of cholesteric structures. ZnO nanoparticles were proved to successfully adjust the helical pitches of the chiral arrangements of the CNCs, resulting in tunable optical light with shifted wavelength bands. Furthermore, the nanocomposite films showed fast humidity and ethanol stimuli response properties, exhibiting the potential of stimuli sensors of the CNC-based sustainable materials.

Uncovering the Recent Progress of CNC-Derived Chirality Nanomaterials: Structure and Functions

Cellulose nanocrystal (CNC), as a renewable resource, with excellent mechanical performance, low thermal expansion coefficient, and unique optical performance, is becoming a novel candidate for the development of smart material. Herein, the recent progress of CNC-based chirality nanomaterials is uncovered, mainly covering structure regulations and function design. Undergoing a simple evaporation process, the cellulose nanorods can spontaneously assemble into chiral nematic films, accompanied by a vivid structural color. Various film structure-controlling strategies, including assembly means, physical modulation, additive engineering, surface modification, geometric structure regulation, and external field optimization, are summarized in this work. The intrinsic correlation between structure and performance is emphasized. Next, the applications of CNC-based nanomaterials is systematically reviewed. Layer-by-layer stacking structure and unique optical activity endow the nanomaterials with wide applications in the mineralization, bone regeneration, and synthesis of mesoporous materials. Besides, the vivid structural color broadens the functions in anti-counterfeiting engineering, synthesis of the shape-memory and self-healing materials. Finally, the challenges for the CNC-based nanomaterials are proposed.

Processing of Thin Films Based on Cellulose Nanocrystals and Biodegradable Polymers by Space-Confined Solvent Vapor Annealing and Morphological Characteristics

L-poly(lactic acid), poly(3-hydroxybutyrate), and poly-hydroxybutyrate-co-hydroxyvalerate are biodegradable polymers that can be obtained from renewable biomass sources. The aim of this study was to develop three types of environmentally friendly film biocomposites of altered microstructure by combining each of the above-mentioned polymers with cellulose nanocrystal fillers and further processing the resulting materials via space-confined solvent vapor annealing. Cellulose was previously obtained from renewable biomass and further converted to cellulose nanocrystals by hydrolysis with the lactic acid. The solutions of biodegradable polymers were spin-coated onto solid substrates before and after the addition of cellulose nanocrystals. The obtained thin film composites were further processed via space-confined solvent vapor annealing to eventually favor their crystallization and, thus, to alter the final microstructure. Indeed, atomic force microscopy studies have revealed that the presence of cellulose nanocrystals within a biodegradable polymer matrix promoted the formation of large crystalline structures exhibiting fractal-, spherulitic- or needle-like morphologies.

Multifunctional Cellulose Nanocrystals Electrolyte Additive Enable Ultrahigh-Rate and Dendrite-Free Zn Anodes for Rechargeable Aqueous Zinc Batteries

The design of aqueous zinc (Zn) chemistry energy storage with high rate-capability and long serving life is a great challenge due to its inhospitable coordination environment and dismal interfacial chemistry. To bridge this big gap, herein, we build a highly reversible aqueous Zn battery by taking advantages of the biomass-derived cellulose nanocrystals (CNCs) electrolyte additive with unique physical and chemical characteristics simultaneously. The CNCs additive not only serves as fast ion carriers for enhancing Zn2+ transport kinetics but regulates the coordination environment and interface chemistry to form dynamic and self-repairing protective interphase, resulting in building ultra-stable Zn anodes under extreme conditions. As a result, the engineered electrolyte system achieves a superior average coulombic efficiency of 97.27 % under 140 mA cm-2, and steady charge-discharge for 982 h under 50 mA cm-2, 50 mAh cm-2, which proposes a universal pathway to challenge aqueous Zn chemistry in green, sustainable, and large-scale applications.

Chiral Pearlescent Cellulose Nanocrystals Films with Broad-Range Tunable Optical Properties for Anti-Counterfeiting Applications

Pearlescent materials are of technological importance in a diverse array of industries from cosmetics to premium paints; however, chiral pearlescent materials remain unexplored. Here, chiral pearlescent films with on-demand iridescence and metallic appearance are simply organized by leveraging vertical pressure to direct the self-assembly of cellulose nanocrystals. The films are formed with a bilayer planar anchored left-handed chiral nematic architecture, in which the bottom layer is featured with a vertical gradient pitch, and the top layer is featured with a uniform pitch. Simultaneous reflection of the rainbow colors and an on-demand color of left-handed polarized light with angle-dependent wavelength and polarization state accounts for the unique optical phenomenon based on experimental observation and theoretical analysis. Such chiroptical property can be readily tuned with architectural design, enabling reproducible optical appearance with high fidelity. Bringing the pearlescence, iridescence, and specular reflection together endows cellulose nanocrystal films with rich and tunable chiroptical properties that can be used for anti-counterfeiting applications. The current work marks the beginning of chiral pearlescent materials from renewable resources, while the pressure-directed self-assembly provides a step toward scalable production.

Stability and Bioaccessibility of Quercetin-Enriched Pickering Emulsion Gels Stabilized by Cellulose Nanocrystals Extracted from Rice Bran

To investigate the optimal delivery system of quercetin, in this paper, cellulose nanocrystals (CNCs) extracted from rice bran were used to stabilize the Pickering emulsion and Pickering emulsion gels (PEGs) with quercetin. To compare the emulsion properties, stability, antioxidation activity, encapsulation rate, and bioaccessibility of the quercetin, four emulsions of CNC Pickering emulsion (C), CNC Pickering emulsion with quercetin (CQ), CNC Pickering gel emulsion (CG), and CNC Pickering gel emulsions with quercetin (CQG) were prepared. All four emulsions exhibited elastic gel network structure and good stability. The quercetin significantly reduced the particle size, increased the stability, and improved the antioxidant capacity of CQ and CQG. Compared to C and CG, the ABTS+ radical scavenging capacities of CQ and CQG were respectively enhanced by 46.92% and 3.59%. In addition, CQG had a higher encapsulation rate at 94.57% and higher bioaccessibility (16.17) compared to CQ. This study not only indicated that CNC from rice bran could be exploited as an excellent stabilization particle for Pickering emulsions, but also provided a highly stable and bioaccessible delivery system for water-insoluble functional active factors.

Green isolation of cellulosic materials from recycled pulp and paper sludge: a Box-Behnken design optimization

Cellulose was isolated from recycled pulp and paper sludge and used to synthesize cellulose nanocrystals. Response surface methodology and Box-Behnken design model were used to predict, improve, and optimize the cellulose isolation process. The optimal conditions were a reaction temperature of 87.5 °C, 180 min with 4% sodium hydroxide. SEM and TEM results revealed that the isolated cellulose had long rod-like structures of different dimensions than CNCs with short rod-like structures. The crystallinity index from XRD significantly increased from 41.33%, 63.7%, and 75.6% for Kimberly mill pulp sludge (KMRPPS), chemically purified cellulose and cellulose nanocrystals, respectively. The TGA/DTG analysis showed that the isolated cellulosic materials possessed higher thermal stability. FTIR analysis suggested that the chemical structures of cellulose and CNCs were modified by chemical treatment. The cellulose surface was highly hydrophilic compared to the CNCs based on the high water holding capacity of 65.31 ± 0.98% and 83.14 ± 1.22%, respectively. The synthesized cellulosic materials portrayed excellent properties for high-end industrial applications like biomedical engineering, advanced materials, nanotechnology, sustainable packaging, personal care products, environmental remediation, additive manufacturing, etc.

Chitosan- and gallic acid-based (NPF) displayed antibacterial activity against three Pseudomonas spp. plant pathogens and boosted systemic acquired resistance in kiwifruit and olive plants

BACKGROUD

Pseudomonas syringae pv. actinidiae (Psa), P. syringae pv. tomato (Pst) and P. savastanoi pv. savastanoi (Psav) are bacterial plant pathogens with worldwide impact that are mainly managed by the preventive application of cupric salts. These are dangerous for ecosystems and have favoured the selection of resistant strains, so they are candidates to be replaced in the next few years. Thus, there is an urgent need to find efficient and bio-based solutions to mitigate these bacterial plant diseases. Nanotechnology could represent an innovative way to control plant diseases, providing alternative solutions to the agrochemicals traditionally employed, thanks to the formulation of the so-called third-generation and nanotechnology-based agrochemicals.

RESULTS

In this work, a novel nanostructured formulation (NPF) composed of cellulose nanocrystals (CNC) as carrier, high amylose starch (HAS) as excipient, and chitosan (CH) and gallic acid (GA) as antimicrobials, was tested at 2% in vitro and in vivo with respect to the three different Pseudomonas plant pathogens. In vitro agar assays demonstrated that the NPF inhibited ≤80% Psa, Pst and Psav. Moreover, the NPF did not decrease biofilm synthesis and it did not influence bacterial cells flocculation and adhesion. On plants, the NPF displayed complete biocompatibility and boosted the transcript levels of the major systemic acquired resistance responsive genes in kiwifruit and olive plants.

CONCLUSION

This works provides novel and valuable information regarding the several modes-of-action of the novel NPF, which could potentially be useful to mitigate Psa, Pst and Psav infections even in organic agriculture. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Recent Advances in Flexible CNC-Based Chiral Nematic Film Materials

Cellulose nanocrystal (CNC) is a renewable resource derived from lignocellulosic materials, known for its optical permeability, biocompatibility, and unique self-assembly properties. Recent years have seen great progresses in cellulose nanocrystal-based chiral photonic materials. However, due to its inherent brittleness, cellulose nanocrystal shows limitations in the fields of flexible materials, optical sensors and food freshness testing. In order to solve the above limitations, attempts have been made to improve the flexibility of cellulose nanocrystal materials without destroying their structural color. Despite these progresses, a systematic review on them is lacking. This review aims to fill this gap by providing an overview of the main strategies and the latest research findings on the flexibilization of cellulose nanocrystal-based chiral nematic film materials (FCNM). Specifically, typical substances and methods used for their preparation are summarized. Moreover, different kinds of cellulose nanocrystal-based composites are compared in terms of flexibility. Finally, potential applications and future challenges of flexible cellulose nanocrystal-based chiral nematic materials are discussed, inspiring further research in this field.

Cellulose nanocrystals-reinforced dual crosslinked double network GelMA/hyaluronic acid injectable nanocomposite cryogels with improved mechanical properties for cartilage tissue regeneration

Improvement of mechanical properties of injectable tissue engineering scaffolds is a current challenge. The objective of the current study is to produce a highly porous injectable scaffold with improved mechanical properties. For this aim, cellulose nanocrystals-reinforced dual crosslinked porous nanocomposite cryogels were prepared using chemically crosslinked methacrylated gelatin (GelMA) and ionically crosslinked hyaluronic acid (HA) through the cryogelation process. The resulting nanocomposites showed highly porous structures with interconnected porosity (>90%) and mean pore size in the range of 130-296 μm. The prepared nanocomposite containing 3%w/v of GelMA, 20 w/w% of HA, and 1%w/v of CNC showed the highest Young's modulus (10 kPa) and excellent reversibility after 90% compression and could regain its initial shape after injection by a 16-gauge needle in the aqueous media. The in vitro results demonstrated acceptable viability (>90%) and migration of the human chondrocyte cell line (C28/I2), and chondrogenic differentiation of human adipose stem cells. A two-month in vivo assay on a rabbit's ear model confirmed that the regeneration potential of the prepared cryogel is comparable to the natural autologous cartilage graft, suggesting it is a promising alternative for autografts in the treatment of cartilage defects.

Compatibilization of Cellulose Nanocrystal-Reinforced Natural Rubber Nanocomposite by Modified Natural Rubber

Due to global warming and environmental concerns, developing a fully bio-based nanocomposite is an attractive issue. In this work, the cellulose nanocrystals (CNCs) extracted from Luffa cylindrica, a renewable resource, were explored as a bio-based reinforcing filler in natural rubber (NR) nanocomposites. In addition, modified natural rubber was explored as a potential compatibilizer to assist the filler dispersion in the rubber nanocomposite. The effect of the CNC content (0-15 phr) on cure characteristics and the mechanical, dynamic, and thermal properties of NR/CNC nanocomposites was investigated. The results showed that the scorch time and cure time of the nanocomposites increased with increased CNC contents. The optimum tensile strength of NR nanocomposites having 5 phr of the CNC (NR-CNC5) was 20.60% higher than the corresponding unfilled NR vulcanizate, which was related to the increased crosslink density of the rubber nanocomposite. The incorporation of oxidized-degraded NR (ODNR) as a compatibilizer in the NR-CNC5 nanocomposite exhibited a considerably reduced cure time, which will lead to energy conservation during production. Moreover, the cure rate index of NR-CNC5-ODNR is much higher than using a petroleum-based silane coupling agent (Si69) as a compatibilizer in the NR-CNC5 nanocomposite. The good filler dispersion in the NR-CNC5 nanocomposite compatibilized by ODNR is comparable to the use of Si69, evidenced by scanning electron microscopy. There is, therefore, a good potential for the use of modified NR as a bio-based compatibilizer for rubber nanocomposites.

Synthesis and Characterization of Cellulose Microfibril-Reinforced Polyvinyl Alcohol Biodegradable Composites

The pursuit of an environmentally sustainable manufacturing process requires the substitution of less damaging and recyclable solutions for harmful reagents. This study aims to assess the effectiveness of using cellulose microfibrils synthesized via different hydrolysis reactions as reinforcing agents in polyvinyl alcohol (PVA) at varying concentrations. The investigation explores the morphology, thermal properties, and chemical behavior of the cellulose particles. The cellulose microfibrils (CMFs) produced using citric acid exhibited the highest yield and aspect ratio. Notably, particles from organic acids demonstrated greater thermal stability, with oxalic acid-derived particles displaying the maximum thermal degradation temperature. Subsequently, cast films of PVA reinforced with the cellulose microfibrils underwent comprehensive analyses, including Fourier transfer infrared (FTIR) spectroscopy, thermal degradation temperature (Td), differential scanning calorimetry (DSC), and tensile strength tests. The thermal behavior of cast films experienced notable changes with the addition of cellulose particles, evidenced by increased melting and crystallinity temperatures, along with a rise in the degree of crystallinity. The incorporation of cellulose particles led to a substantial improvement in mechanical properties. Films containing CMF displayed higher Young's modulus, and the sample incorporating 5% CMF derived from citric acid exhibited the most significant increase in modulus.

Improvement in the Thermomechanical Properties and Adhesion of Wood Fibers to the Polyamide 6 Matrix by Sequential Ball Milling Technique

The engineering thermoplastics industry has largely limited the use of natural fiber reinforcements due to their susceptibility to low-onset thermal degradation and water absorption. Therefore, in order to utilize these economically viable and environmentally friendly materials effectively through common composite fabrication methods such as hot pressing, safeguarding them from thermal degradation becomes essential. This work presents a viable industrially technique called sequential ball milling for processing unbleached softwood kraft pulp fibers (PF) with an engineering thermoplastics polyamide 6 (PA6) with high melting temperatures (>220 °C). An additional eco-friendly modification step that employs ball milling and cellulose nanocrystal (CNC) has been implemented in this study to enhance the mechanical properties of the composites. Special attention is given to fine-tuning key variables, such as milling duration and PF particle size, to produce optimal composites. Leveraging the ability of sequential ball milling to evenly distribute pulp fibers into PA6, a 160% increase in Young's modulus was achieved with the incorporation of 30 wt % PF. Importantly, the introduction of a 5 wt % CNC modifying agent elevated Young's modulus to 4.3 GPa, marking a 187% improvement over unmodified PA6. Diverse techniques, including rheological analyses, thermomechanical evaluations, morphological examinations, and assessments of moisture absorption, were utilized to validate the efficiency of the suggested processing approach and the modification phase.

Cellulose nanocrystals from celery stalk as quercetin scaffolds: A novel perspective of human holo-transferrin adsorption and digestion behaviours

In this study, cellulose nanocrystals (CNCs) were synthesized from celery stalks to be used as the platform for quercetin delivery. Additionally, CNCs and CNCs-quercetin were characterized using the results of scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and zeta potential, while their interactions with human holo-transferrin (HTF) were also investigated. We examined their interaction under physiological conditions through the exertion of fluorescence, resonance light scattering, synchronized fluorescence spectroscopy, circular dichroism, three-dimensional fluorescence spectroscopy, and fluorescence resonance energy transfer techniques. The data from SEM and TEM exhibited the spherical shape of CNCs and CNCs-quercetin and also, a decrease was detected in the size of quercetin-loaded CNCs from 676 to 473 nm that indicated the intensified water solubility of quercetin. The success of cellulose acid hydrolysis was confirmed based on the XRD results. Apparently, the crystalline index of CNCs-quercetin was reduced by the interaction of CNCs with quercetin, which also resulted in the appearance of functional groups, as shown by FTIR. The interaction of CNCs-quercetin with HTF was also demonstrated by the induced quenching in the intensity of HTF fluorescence emission and Stern-Volmer data represent the occurrence of static quenching. Overall, the effectiveness of CNCs as quercetin vehicles suggests its potential suitability for dietary supplements and pharmaceutical products.

Inkjet Printed Photonic Cellulose Nanocrystal Patterns

Naturally-sourced cellulose nanocrystals (CNCs) are elongated, birefringent nanoparticles that can undergo cholesteric self-assembly in water to produce vibrant, structurally colored films. As such, they are an ideal candidate for use as sustainable and cost-effective inks in the printing of scalable photonic coatings and bespoke patterns. However, the small volume and large surface area of a sessile CNC drop typically leads to rapid evaporation, resulting in microfilms with a coffee-stain-like morphology and very weak coloration. Here, it is demonstrated that inkjet printing of CNC drops directly through an immiscible oil layer can immediately inhibit water loss, resulting in reduced internal mass flows and greater time for cholesteric self-assembly. The color of each microfilm is determined by the initial composition of the drop, which can be tuned on-demand by exploiting the overprinting and coalescence of multiple smaller drops of different inks. This enables the production of multicolored patterns with complex optical behaviors, such as angle-dependent color and polarization-selective reflection. Finally, the array can be made responsive to stimuli (e.g., UV light, polar solvent) by the inclusion of a degradable additive. This suite of functional properties promotes inkjet-printed photonic CNC arrays for smart colorimetric labeling or optical anticounterfeiting applications.

Fibrillar Hydrogel Based on Cellulose Nanocrystals Crosslinked via Diels-Alder Reaction: Preparation and pH-Sensitive Release of Benzocaine

A fibrillar hydrogel was obtained by covalent crosslinking via Diels-Alder reaction of two types of cellulose nanocrystals (CNCs) with furan and maleimide groups. Gelation has been studied at various ratios of components and temperatures in the range from 20 to 60 °C. It was shown that the rheological properties of the hydrogel can be optimized by varying the concentration and ratio of components. Due to the rigid structure of the CNCs, the hydrogel could be formed at a concentration of at least 5 wt%; however, it almost does not swell either in water with pH 5 or 7 or in the HBSS buffer. The introduction of aldehyde groups into the CNCs allows for the conjugation of physiologically active molecules containing primary amino groups due to the formation of imine bonds. Here, we used benzocaine as a model drug for conjugation with CNC hydrogel. The resulting drug-conjugated hydrogel demonstrated the stability of formulation at pH 7 and a pH-sensitive release of benzocaine due to the accelerated hydrolytic cleavage of the imine bond at pH < 7. The developed drug-conjugated hydrogel is promising as wound dressings for local anesthesia.

Cellulose Nanocrystal-Based Emulsion of Thyme Essential Oil: Preparation and Characterisation as Sustainable Crop Protection Tool

Essential oil-based pesticides, which contain antimicrobial and antioxidant molecules, have potential for use in sustainable agriculture. However, these compounds have limitations such as volatility, poor water solubility, and phytotoxicity. Nanoencapsulation, through processes like micro- and nanoemulsions, can enhance the stability and bioactivity of essential oils. In this study, thyme essential oil from supercritical carbon dioxide extraction was selected as a sustainable antimicrobial tool and nanoencapsulated in an oil-in-water emulsion system. The investigated protocol provided high-speed homogenisation in the presence of cellulose nanocrystals as stabilisers and calcium chloride as an ionic crosslinking agent. Thyme essential oil was characterised via GC-MS and UV-vis analysis, indicating rich content in phenols. The cellulose nanocrystal/essential oil ratio and calcium chloride concentration were varied to tune the nanoemulsions' physical-chemical stability, which was investigated via UV-vis, direct observation, dynamic light scattering, and Turbiscan analysis. Transmission electron microscopy confirmed the nanosized droplet formation. The nanoemulsion resulting from the addition of crosslinked nanocrystals was very stable over time at room temperature. It was evaluated for the first time on Pseudomonas savastanoi pv. savastanoi, the causal agent of olive knot disease. In vitro tests showed a synergistic effect of the formulation components, and in vivo tests on olive seedlings demonstrated reduced bacterial colonies without any phytotoxic effect. These findings suggest that crosslinked cellulose nanocrystal emulsions can enhance the stability and bioactivity of thyme essential oil, providing a new tool for crop protection.

Characterization of CNC Nanoparticles Prepared via Ultrasonic-Assisted Spray Drying and Their Application in Composite Films

The ultrasonic-assisted spray dryer, also known as a nano spray dryer and predominantly used on a lab scale in the pharmaceutical and food industries, enables the production of nanometer-sized particles. In this study, the nano spray dryer was applied to cellulosic materials, such as cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs). CNC suspensions were successfully dried, while the CNF suspensions could not be dried, attributable to their longer fibril lengths. The nano spray drying process was performed under different drying conditions, including nebulizer hole sizes, solid concentrations, and gas flow rates. It was confirmed that the individual particle size of nano spray-dried CNCs (nano SDCNCs) decreased as the nebulizer hole sizes and solid contents of the suspensions decreased. The production rate of the nano spray dryer increased with higher solid contents and lower gas flow rates. The resulting nano SDCNCs were added to a polyvinyl alcohol (PVA) matrix as a reinforcing material to evaluate their reinforcement behavior in a plastic matrix using solvent casting. After incorporating the 20 wt.% nano SDCNCs into the PVA matrix, the tensile strength and tensile modulus elasticity of the neat PVA nanocomposite film increased by 22% and 32%, respectively, while preserving the transparency of the films.

Characterization of Cellulose Fiber Derived from Hemp and Polyvinyl Alcohol-Based Composite Hydrogel as a Scaffold Material

Cellulose nanocrystals (CNCs) were successfully extracted and purified from hemp using an alkaline treatment and bleaching process and subsequently used in conjunction with polyvinyl alcohol to form a composite hydrogel. Cellulose nanocrystals (1-10% (w/v)) were integrated into polyvinyl alcohol, and sodium tetraborate (borax) was employed as a crosslinking agent. Due to the small number of cellulose nanocrystals, no significant peak change was observed in the FT-IR spectra compared to pristine polyvinyl alcohol. The porosity was created upon the removal of the water molecules, and the material was thermally stable up to 200 °C. With the presence of cellulose nanocrystals, the melting temperature was slightly shifted to a higher temperature, while the glass transition temperature remained practically unchanged. The swelling behavior was examined for 180 min in deionized water and PBS solution (pH 7.4) at 37 °C. The degree of swelling of the composite with cellulose nanocrystals was found to be higher than that of pristine PVA hydrogel. The cell viability (%) of the prepared hydrogel with different proportions of cellulose nanocrystals was higher than that of pristine PVA hydrogel. Based on the results, the prepared composite hydrogels from cellulose nanocrystals extracted from hemp and polyvinyl alcohol were revealed to be an excellent candidate for scaffold material for medical usage.

Tannic Acid-Induced Gelation of Aqueous Suspensions of Cellulose Nanocrystals

Nanocellulose hydrogels are a crucial category of soft biomaterials with versatile applications in tissue engineering, artificial extracellular matrices, and drug-delivery systems. In the present work, a simple and novel method, involving the self-assembly of cellulose nanocrystals (CNCs) induced by tannic acid (TA), was developed to construct a stable hydrogel (SH-CNC/TA) with oriented porous network structures. The gelation process is driven by the H-bonding interaction between the hydroxyl groups of CNCs and the catechol groups of TA, as substantiated by the atoms in molecules topology analysis and FTIR spectra. Interestingly, the assembled hydrogels exhibited a tunable hierarchical porous structure and mechanical moduli by varying the mass ratio of CNCs to TA. Furthermore, these hydrogels also demonstrate rapid self-healing ability due to the dynamic nature of the H-bond. Additionally, the structural stability of the SH-CNC/TA hydrogel could be further enhanced and adjusted by introducing coordination bonding between metal cations and TA. This H-bonding driven self-assembly method may promote the development of smart cellulose hydrogels with unique microstructures and properties for biomedical and other applications.

In situ capping of silver nanoparticles with cellulosic matrices from wheat straws in enhancing their antimicrobial activity: Synthesis and characterization

Silver nanoparticles have gained worldwide attention in the scientific community due to their high antimicrobial activity. However, they tend to agglomerate and lose their shape and properties, thus capping agents necessary to protect their shapes, sizes, and properties. To enhance their antimicrobial activity, this research aimed to cap silver nanoparticles with cellulosic matrices from wheat straws. The wheat straw was delignified with 6% HNO3, and the residual was treated with 1% NaOH and NaClO: CH3COOH (1:1), then used to synthesize cellulose nanocrystals via acid hydrolysis. AgNPs were incorporated into the CPC and CNCs by in-situ synthesis using NaHB4 as the reducing agent. Fourier Transform Infrared, Scanning Electron Microscopy, and X-ray diffraction were used to investigate their features. The findings exhibited crystallinity increased with subsequent treatments, according to XRD analysis. Ultraviolet-visible, FTIR, TEM, and XRD analysis confirmed the capping of AgNPs onto the cellulosic materials. Antibacterial activity against Staphylococcus aureus and Escherichia coli, with CNCs-AgNPs composite, exhibited higher activity compared to CPC-AgNPs composite due to the increased surface area and excellent binding on the surface of the composite.

Nanocrystalline Cellulose as a Versatile Engineering Material for Extrusion-Based Bioprinting

Naturally derived polysaccharide-based hydrogels, such as alginate, are frequently used in the design of bioinks for 3D bioprinting. Traditionally, the formulation of such bioinks requires the use of pre-reticulated materials with low viscosities, which favour cell viability but can negatively influence the resolution and shape fidelity of the printed constructs. In this work, we propose the use of cellulose nanocrystals (CNCs) as a rheological modifier to improve the printability of alginate-based bioinks whilst ensuring a high viability of encapsulated cells. Through rheological analysis, we demonstrate that the addition of CNCs (1% and 2% (w/v)) to alginate hydrogels (1% (w/v)) improves shear-thinning behaviour and mechanical stability, resulting in the high-fidelity printing of constructs with superior resolution. Importantly, LIVE/DEAD results confirm that the presence of CNCs does not seem to affect the health of immortalised chondrocytes (TC28a2) that remain viable over a period of seven days post-encapsulation. Taken together, our results indicate a favourable effect of the CNCs on the rheological and biocompatibility properties of alginate hydrogels, opening up new perspectives for the application of CNCs in the formulation of bioinks for extrusion-based bioprinting.

Mussel-Inspired Nanocellulose Coating for Selective Neodymium Recovery

Neodymium (Nd) is one of the most in-demand rare earth elements (REEs) for developing the next generation of magnetic medical devices and clean energy. Eco-friendly and sustainable nanotechnology for REE recovery may be highly suitable to address the limited global supply while minimizing the environmental footprints of current practice, such as solvent extraction. Here, we present a novel one-step mussel-inspired nanocellulose coating (MINC) using bifunctional hairy cellulose nanocrystals (BHCNC), bearing dialdehyde and dicarboxylate groups. The dialdehyde groups enable dopamine-mediated orthogonal conjugation of BHCNC to substrates, such as microparticles, while the high content of dicarboxylate groups yields high-capacity and selective Nd removal against ferric, calcium, and sodium ions. To the best of our knowledge, the MINC-treated substrate provides the most rapid selective removal and recovery of Nd ions even at low Nd concentrations with a capacity that is among the highest reported values. We envision that the MINC will provide new opportunities in developing next-generation bio-based materials and interfaces for the sustainable recovery of REEs and other precious elements.

Thermoplastic Starch Biocomposite Films Reinforced with Nanocellulose from Agave tequilana Weber var. Azul Bagasse

In this work, cellulose nanocrystals (CNCs), bleached cellulose nanofibers (bCNFs), and unbleached cellulose nanofibers (ubCNFs) isolated by acid hydrolysis from Agave tequilana Weber var. Azul bagasse, an agro-waste from the tequila industry, were used as reinforcements in a thermoplastic starch matrix to obtain environmentally friendly materials that can substitute contaminant polymers. A robust characterization of starting materials and biocomposites was carried out. Biocomposite mechanical, thermal, and antibacterial properties were evaluated, as well as color, crystallinity, morphology, rugosity, lateral texture, electrical conductivity, chemical identity, solubility, and water vapor permeability. Pulp fibers and nanocelluloses were analyzed via SEM, TEM, and AFM. The water vapor permeability (WVP) decreased by up to 20.69% with the presence of CNCs. The solubility decreases with the presence of CNFs and CNCs. The addition of CNCs and CNFs increased the tensile strength and Young's modulus and decreased the elongation at break. Biocomposites prepared with ubCNF showed the best tensile mechanical properties due to a better adhesion with the matrix. Images of bCNF-based biocomposites demonstrated that bCNFs are good reinforcing agents as the fibers were dispersed within the starch film and embedded within the matrix. Roughness increased with CNF content and decreased with CNC content. Films with CNCs did not show bacterial growth for Staphylococcus aureus and Escherichia coli. This study offers a new theoretical basis since it demonstrates that different proportions of bleached or unbleached nanofibers and nanocrystals can improve the properties of starch films.

Injectable pH and Thermo-Responsive Hydrogel Scaffold with Enhanced Osteogenic Differentiation of Preosteoblasts for Bone Regeneration

Bone fractures are common in the geriatric population and pose a great economic burden worldwide. While traditional methods for repairing bone defects have primarily been autografts, there are several drawbacks limiting its use. Bone graft substitutes have been used as alternative strategies to improve bone healing. However, there remain several impediments to achieving the desired healing outcomes. Injectable hydrogels have become attractive scaffold materials for bone regeneration, given their high performance in filling irregularly sized bone defects and their ability to encapsulate cells and bioactive molecules and mimic the native ECM of bone. We investigated the use of an injectable chitosan-based hydrogel scaffold to promote the differentiation of preosteoblasts in vitro. The hydrogels were characterized by evaluating cell homogeneity, cell viability, rheological and mechanical properties, and differentiation ability of preosteoblasts in hydrogel scaffolds. Cell-laden hydrogel scaffolds exhibited shear thinning behavior and the ability to maintain shape fidelity after injection. The CNC-CS hydrogels exhibited higher mechanical strength and significantly upregulated the osteogenic activity and differentiation of preosteoblasts, as shown by ALP activity assays and histological analysis of hydrogel scaffolds. These results suggest that this injectable hydrogel is suitable for cell survival, can promote osteogenic differentiation of preosteoblasts, and structurally support new bone growth.

Cellulose Nanocrystal-Based Gradient Hydrogel Actuators with Controllable Bending Properties

Stimuli-responsive hydrogel actuators are being increasingly used in microtechnology, but typical bilayer hydrogel actuators have significant drawbacks due to weak adhesive interface between the two layers. In this study, thermoresponsive single-layer hydrogel actuators are produced by generating a gradient distribution of cellulose nanocrystals (CNCs) in a poly(N-isopropylacrylamide) (PNIPAAm) hydrogel network by electrophoresis. Tunable bending properties of the composite hydrogels, such as the thermoresponsive bending speed and angle, are realized by varying the electrophoresis time, applied voltage, and CNC concentration. By varying these conditions, the gradient distribution of the CNCs can be optimized, leading to fast bending and large bending angles of the hydrogels. Bending properties are attributed to the gradient distribution of CNCs causing different deswelling rates across the hydrogel network owing to reinforcing effects. Bending ability is also influenced by differences in the CNC dimensions based on the sources of cellulose, which determine the rigidity of the CNC-rich layer of the polymer composite. It is thus shown that thermoresponsive single-layer gradient hydrogels with tunable bending properties can be realized.

Responsive Regulation of Energy Transfer in Lanthanide-Doped Nanomaterials Dispersed in Chiral Nematic Structure

The responsive control of energy transfer (ET) plays a key role in the broad applications of lanthanide-doped nanomaterials. Photonic crystals (PCs) are excellent materials for ET regulation. Among the numerous materials that can be used to fabricate PCs, chiral nematic liquid crystals are highly attractive due to their good photoelectric responsiveness and biocompatibility. Here, the mechanisms of ET and the photonic effect of chiral nematic structures on ET are introduced; the regulation methods of chiral nematic structures and the resulting changes in ET of lanthanide-doped nanomaterials are highlighted; and the challenges and promising opportunities for ET in chiral nematic structures are discussed.

Robust Cellulose Nanocrystal-Based Self-Assembled Composite Membranes Doped with Polyvinyl Alcohol and Graphene Oxide for Osmotic Energy Harvesting

Osmotic energy from the salinity gradients represents a promising energy resource with stable and sustainable characteristics. Nanofluidic membranes can be considered as powerful alternatives to the traditional low-performance ion exchange membrane to achieve high-efficiency osmotic energy harvesting. However, the development of a highly efficient and easily scalable core membrane component from low-cost raw materials remains challenging. Here, a composite membrane based on the self-assembly of cellulose nanocrystals (CNCs) with polyvinyl alcohol (PVA) and graphene oxide (GO) nanoflakes as additives is developed to provide a solution. The introduction of soft PVA polymer significantly improves the mechanical strength and water stability of the composite membrane by forming a nacre-like structure. Benefiting from the abundant negative charges of CNC nanorods and GO nanoflakes and the generated network nanochannels, the composite membrane demonstrates a good cation-selective transport capacity, thus contributing to an optimal osmotic energy conversion of 6.5 W m-2 under a 100-fold salinity gradient and an exemplary stability throughout 25 consecutive days of operation. This work provides an option for the development of nanofluidic membranes that can be easily produced on a large scale from well-resourced and sustainable biomass materials for high-efficiency osmotic energy conversion.

Oil-in-Water Pickering Emulsions Stabilized with Nanostructured Biopolymers: A Venue for Templating Bacterial Cellulose

Pickering emulsions (PEs) differ from conventional emulsions in the use of solid colloidal particles as stabilizing agents instead of traditional amphiphilic molecules. Nanostructured biopolymers (NBs) emerge as a promising alternative for PE stabilization owing to their remarkable biocompatibility, abundant availability, and low cost. To explore this potential, a study is herein presented, in which cellulose nanocrystals (CNCs), both type I and type II allomorphs, and chitin nanocrystals (ChNCs) were used for stabilizing oil-in-water PEs prepared by the use of ultrasound. Sunflower oil was selected as the oil phase as it offers the advantages of being edible, renewable, and inexpensive. By utilizing ζ-potential, static light diffraction, and visual observations, we determined the optimal oil/water ratio for each type of NB to obtain stable emulsions after 14 days. The optimized PEs were used to form bacterial nanocellulose composites through emulsion templating. To our knowledge, this study represents a pioneering work in exploiting oil-in-water PEs for this approach. Additionally, it entails the first utilization of nonmercerized type II CNCs as stabilizers for PEs, while also establishing a direct comparison among the most relevant NBs. The resulting composites exhibited a unique morphology, composed of larger pores compared to standard bacterial nanocellulose aerogels. These findings highlight the notable potential of NBs as stabilizers for PEs and their ability to generate green nanocomposites with tailored properties.

Interfacial Compatibility of Core-Shell Cellulose Nanocrystals for Improving Dynamic Covalent Adaptable Networks' Fracture Resistance in Nanohybrid Vitrimer Composites

The development of polymeric nanocomposites with dynamic covalent adaptable networks and biobased nanomaterials has been a promising approach toward sustainable advanced materials, enabling reprogramming and recycling capabilities. Herein, a core-shell nanohybrid of functionalized cellulose nanocrystals (CNCs) is explored to provide crucial interfacial compatibility for improving the covalent adaptable networks of epoxy-thiol vitrimers in fracture resistance. The poly(ε-caprolactone) (PCL) shells grafted from CNC surfaces can be cross-linked with the covalent adaptable networks via a hot-pressing transesterification process. According to the additive concentration and annealing temperature, the stress relaxation behavior of nanohybrid vitrimer composites can be effectively regulated by the core-shell PCL-grafted CNC (CNC-PCL) nanohybrids from a dispersed to cross-linked interaction. The addition of 15 wt % of the core-shell CNC-PCLs exhibits the reinforced improvement of nanohybrid vitrimer composites in the average Young's modulus of 2.5×, fracture stress of 5.4×, and fracture strain of 2.0×. The research findings might have profound implications for developing synergistic interfacial compatibility between dynamic vitrimer networks and functional nanoparticles for advanced polymeric nanocomposites.

A Comparative Study of the Impact of the Bleaching Method on the Production and Characterization of Cotton-Origin Nanocrystalline Cellulose by Acid and Enzymatic Hydrolysis

Due to environmental concerns, as well as its exceptional physical and mechanical capabilities, biodegradability, and optical and barrier qualities, nanocellulose has drawn a lot of interest as a source of reinforcing materials that are nanometer sized. This article focuses on how to manufacture cellulose nanomaterials from cotton by using different types of acids such as H2SO4 and HCI in different concentrations and in the presence of enzymes such as cellulase and xylanase. Two different types of bleaching methods were used before acid and enzyme hydrolysis. In the first method, cellulose was extracted by bleaching the cotton with H2O2. In the second method, NaOCl was utilized. For both methods, different concentrations of acids and enzymes were used to isolate nanocellulose materials, cellulose nanocrystals (CNC), and cellulose nanofibrils (CNF) at different temperatures. All obtained nanocellulose materials were analyzed through different techniques such as FT-IR, Zeta potentials, DLS, Raman spectroscopy, TGA, DSC, XRD, and SEM. The characteristic signals related to cellulose nanocrystals (CNC) were confirmed with the aid of Raman and FT-IR spectroscopy. According to the XRD results, the samples' crystallinity percentages range from 54.1% to 63.2%. The SEM image showed that long fibers break down into small fibers and needle-like features are seen on the surface of the fibers. Using different types of bleaching has no significant effect on the thermal stability of samples. The results demonstrate a successful method for synthesizing cellulose nanofibrils (CNF) from cotton through enzymatic hydrolysis, but the results also demonstrated that the choice of bleaching method has a significant impact on the hydrodynamic properties and crystallinity of both CNC and CNF samples.

Wound Dressing Double-Crosslinked Quick Self-Healing Hydrogel Based on Carboxymethyl Chitosan and Modified Nanocellulose

The use of hydrogels in wound dressings, which is pivotal for effective wound treatment, has been widely applied to diverse medical wound conditions. However, formulating natural hydrogels that combine robust strength and self-healing capabilities is a significant challenge. To overcome this, we successfully designed a natural nanocellulose self-healing hydrogel that can quickly self-heal and restore the complete hydrogel structure after injury to fill the injured area and protect the wound from external damage. Our study utilized modified natural polymer carboxymethyl chitosan (CMC), hydrazide-modified carboxymethyl cellulose nanofibers (HCNF), and cellulose nanocrystals modified by dialdehyde (DACNC) to fabricate the hydrogel. The amides containing more amino groups and HCNF in CMC can be used as cross-linking nodes, and the high aspect ratio and specific surface area of DACNC are favorable for the connection of many active hydrogels. The hydrogel is crosslinked by the dynamic imide bond and hydrazone bond between the amino group of CMC, the amide of HCNF, and the aldehyde of DACNC and has a double network structure. These connections can be readily reassembled when disrupted, enabling fast self-healing of hydrogels within five minutes. Moreover, HCNF and DACNC were incorporated as nano-reinforced fillers to bolster the hydrogel's strength while preserving its high liquid absorption capacity (381% equilibrium swelling rate).

Facile Hydrothermal Synthesis of Ag/Fe3O4/Cellulose Nanocomposite as Highly Active Catalyst for 4-Nitrophenol and Organic Dye Reduction

Novel effluent treatment solutions for dangerous organic pollutants are crucial worldwide. In recent years, chemical reduction using noble metal-based nanocatalysts and NaBH4, a reducing agent, has become common practice for eliminating organic contaminants from aquatic environments. We suggest a straightforward approach to synthesizing magnetic cellulose nanocrystals (CNCs) modified with magnetite (Fe3O4) and silver nanoparticles (Ag NPs) as a catalyst for organic contamination removal. Significantly, the CNC surface was decorated with Ag NPs without using any reducing agents or stabilizers. PXRD, FE-SEM, TEM, EDX, VSM, BET, and zeta potential tests characterized the Ag/Fe3O4/CNC nanocomposite. The nanocomposite's catalytic activity was tested by eliminating 4-nitrophenol (4-NP) and the organic dyes methylene blue (MB) and methyl orange (MO) in an aqueous solution at 25 °C. The Ag/Fe3O4/CNC nanocomposite reduced 4-NP and decolored these hazardous organic dyes in a short time (2 to 5 min) using a tiny amount of catalyst (2.5 mg for 4-NP and 15 mg for MO and MB). The magnetic catalyst was removed and reused three times without losing catalytic activity. This work shows that the Ag/Fe3O4/CNC nanocomposite can chemically reduce harmful pollutants in effluent for environmental applications.

Multi-Responsive Supercapacitors from Chiral Nematic Cellulose Nanocrystal-Based Activated Carbon Aerogels

The development of long-lived electrochemical energy storage systems based on renewable materials is integral for the transition toward a more sustainable society. Supercapacitors have garnered considerable interest given their impressive cycling performance, low cost, and safety. Here, the first example of a chiral nematic activated carbon aerogel is shown. Specifically, supercapacitor materials are developed based on cellulose, a non-toxic and biodegradable material. The chiral nematic structure of cellulose nanocrystals (CNCs) is harnessed to obtain free-standing hierarchically ordered activated carbon aerogels. To impart multifunctionality, iron- and cobalt-oxide nanoparticles are incorporated within the CNC matrix. The hierarchical structure remains intact even at nanoparticle concentrations of ≈70 wt%. The aerogels are highly porous, with specific surface areas up to 820 m2 g-1 . A maximum magnetization of 17.8 ± 0.1 emu g-1 with superparamagnetic behavior is obtained, providing a base for actuator applications. These materials are employed as symmetric supercapacitors; owing to the concomitant effect of the hierarchically arranged carbon skeleton and KOH activation, a maximum Cp of 294 F g-1 with a capacitance retention of 93% after 2500 cycles at 50 mV s-1 is achieved. The multifunctionality of the composite aerogels opens new possibilities for the use of biomass-derived materials in energy storage and sensing applications.

Multifunctionality through Embedding Patterned Nanostructures in High-Performance Composites

Despite being a pillar of high-performance materials in industry, manufacturing carbon fiber composites with simultaneously enhanced multifunctionality and structural properties has remained elusive due to the lack of practical bottom-up approaches with control over nanoscale interactions. Guided by the droplet's internal currents and amphiphilicity of nanomaterials, herein, a programmable spray coating is introduced for the deposition of multiple nanomaterials with tailorable patterns in composite.  It is shown that such patterns regulate the formation of interfaces, damage containment, and electrical-thermal conductivity of the composites, which is absent in conventional manufacturing that primarily rely on incorporating nanomaterials to achieve specific functionalities. Molecular dynamics simulations show that increasing the hydrophilicity of the hybrid nanomaterials, which is synchronous with shifting patterns from disk to ring, improves the interactions between the carbon surfaces and epoxy at the interfaces,manifested in enhanced interlaminar and flexural performance. Transitioning from ring to disk creates a larger interconnected network  leading to improved thermal and electrical properties without penalty in mechanical properties. This novel approach introduces a new design , where the mechanical and multifunctional performance is controlled by the shape of the deposited patterns, thus eliminating the trade-off between properties that are considered paradoxical in today's manufacturing of hierarchical composites.

Chiroptical Nanocellulose Bio-Labels for Independent Multi-Channel Optical Encryption

Advanced multiplexing optical labels with multiple information channels provide a powerful strategy for large-capacity and high-security information encryption. However, current optical labels face challenges of difficulty to realize independent multi-channel encryption, cumbersome design, and environmental pollution. Herein, multiplexing chiroptical bio-labels integrating with multiple optical elements, including structural color, photoluminescence (PL), circular polarized light activity, humidity-responsible color, and micro/nano physical patterns, are constructed in complex design based on host-guest self-assembly of cellulose nanocrystals and bio-gold nanoclusters. The thin nanocellulose labels exhibit tunable circular polarized structural color crossover the entire visible wavelength and circularly polarized PL with the highest-recorded dissymmetry factor up to 1.05 due to the well-ordered chiral organization of templated gold nanoclusters. Most importantly, these elements can independently encode customized anti-counterfeiting information to achieve five independent channels of high-level anti-counterfeiting, which are rarely achieved in traditional materials and design counterparts. Considering the exceptional seamless integration of five independent encryption channels and the recyclable features of labels, the bio-labels have great potential for the next generation anti-counterfeiting materials technology.

Reinforcement of Acrylamide Hydrogels with Cellulose Nanocrystals Using Gamma Radiation for Antibiotic Drug Delivery

In this paper, we report the synthesis of acrylamide hydrogels (net-AAm) reinforced with cellulose nanocrystals (CNCs) using gamma radiation, a powerful tool to obtain crosslinked polymers without the use of chemical initiators and crosslinking agents. Some slight changes in the chemical structure and crystallinity of CNCs took place during gamma irradiation without affecting the nanofiller function. In fact, cellulose nanocrystals had a notable influence over the swelling and mechanical properties on the reinforced hydrogels (net-AAm/CNC), obtaining more rigid material since the Young compression modulus increased from 11 kPa for unreinforced net-AAm to 30 kPa for net-AAm/CNC (4% w/w). Moreover, the studies of retention and release of ciprofloxacin (Cx), a quinolone antibiotic drug, showed that reinforced hydrogels were able to load large amounts of ciprofloxacin (1.2-2.8 mg g-1) but they distributed 100% of the drug very quickly (<100 min). Despite this, they exhibited better mechanical properties than the control sample, allowing their handling, and could be used as wound dressings of first response because they can absorb the exudate and at the same time deliver an antibiotic drug directly over the injury.

Assessing the Effect of Cellulose Nanocrystal Content on the Biodegradation Kinetics of Multiscale Polylactic Acid Composites under Controlled Thermophilic Composting Conditions

This work studied the effect of cellulose nanocrystal (NCC) content on the biodegradation kinetics of PLA-based multiscale cellulosic biocomposites (PLAMCBs). To facilitate biodegradation, the materials were subjected to thermo-oxidation before composting. Biodegradation was carried out for 180 days under controlled thermophilic composting conditions according to the ASTM D 5338 standard. A first-order model based on Monod's kinetics under limiting substrate conditions was used to study the effect of cellulose nanocrystal (NCC) content on the biodegradation kinetics of multiscale composite materials. It was found that thermo-oxidation at 70 °C for 160 h increased the biodegradability of PLA. Also, it was found that the incorporation of cellulosic fibrous reinforcements increased the biodegradability of PLA by promoting hydrolysis during the first stage of composting. Likewise, it was found that partial substitution of micro cellulose (MFC) by cellulose nanocrystals (NCCs) increased the biodegradability of the biocomposite. This increase was more evident as the NCC content increased, which was attributed to the fact that the incorporation of cellulose nanocrystals facilitated the entry of water into the material and therefore promoted the hydrolytic degradation of the most recalcitrant fraction of PLA from the bulk and not only by surface erosion.

Extraction and Surface Functionalization of Cellulose Nanocrystals from Sugarcane Bagasse

The present study aimed to optimize the process for extracting cellulose nanocrystals (CNCs) from sugarcane bagasse through ultrasonic-assisted sulfuric acid hydrolysis and its subsequent modification with L-malic acid and silane coupling agent KH-550. The effects of the different modification methods and the order of modification on the structures and properties of bagasse CNCs were explored. The results indicated that the optimal process conditions were achieved at an acid-digestion temperature of 50 °C, a reaction time of 70 min, an ultrasonic power of 250 W, and a volume fraction of 55%. The modified CNCs were analyzed using infrared spectral, X-ray diffraction, and thermogravimetric techniques, which revealed that L-malic acid was attached to the hydroxyl group on the CNCs via ester bond formations, and the silane coupling agent KH-550 was adsorbed effectively on the CNCs' surfaces. Moreover, it was observed that the modification of the CNCs by L-malic acid and the KH-550 silane coupling agent occurred only on the surface, and the esterification-crosslinking modification method provided the best thermal stability. The performance of self-made CNC was found to be superior to that of purchased CNC based on the transmission electron microscopy analysis. Furthermore, the modified esterified-crosslinked CNCs exhibited the best structure and performance, thereby offering a potential avenue for the high-value utilization of sugarcane bagasse, a byproduct of sugarcane sugar production, and the expansion of the comprehensive utilization of sugarcane bagasse.

Cellulose Nanocrystal (CNC) Gels: A Review

The aim of this article is to review the research conducted in the field of aqueous and polymer composites cellulose nanocrystal (CNC) gels. The experimental techniques employed to characterize the rheological behavior of these materials will be summarized, and the main advantages of using CNC gels will also be addressed in this review. In addition, research devoted to the use of numerical simulation methodologies to describe the production of CNC-based materials, e.g., in 3D printing, is also discussed. Finally, this paper also discusses the application of CNC gels along with additives such as cross-linking agents, which can represent an enormous opportunity to develop improved materials for manufacturing processes.

Harnessing Nature's Ingenuity: A Comprehensive Exploration of Nanocellulose from Production to Cutting-Edge Applications in Engineering and Sciences

Primary material supply is the heart of engineering and sciences. The depletion of natural resources and an increase in the human population by a billion in 13 to 15 years pose a critical concern regarding the sustainability of these materials; therefore, functionalizing renewable materials, such as nanocellulose, by possibly exploiting their properties for various practical applications, has been undertaken worldwide. Nanocellulose has emerged as a dominant green natural material with attractive and tailorable physicochemical properties, is renewable and sustainable, and shows biocompatibility and tunable surface properties. Nanocellulose is derived from cellulose, the most abundant polymer in nature with the remarkable properties of nanomaterials. This article provides a comprehensive overview of the methods used for nanocellulose preparation, structure-property and structure-property correlations, and the application of nanocellulose and its nanocomposite materials. This article differentiates the classification of nanocellulose, provides a brief account of the production methods that have been developed for isolating nanocellulose, highlights a range of unique properties of nanocellulose that have been extracted from different kinds of experiments and studies, and elaborates on nanocellulose potential applications in various areas. The present review is anticipated to provide the readers with the progress and knowledge related to nanocellulose. Pushing the boundaries of nanocellulose further into cutting-edge applications will be of particular interest in the future, especially as cost-effective commercial sources of nanocellulose continue to emerge.

Aqueous-Cellulose-Solvent-Derived Changes in Cellulose Nanocrystal Structure and Reinforcing Effects

Cellulose nanocrystals as reinforcing agents have received considerable interest, and their dimension mainly depends on the original sources of cellulose. We intend to manually modulate the morphology of cellulose nanocrystals by treating them with cellulose solvents so that we can explore their reinforcing capacity. In this work, waste cotton fabric was processed in two aqueous solvents (a sulfuric acid aqueous solution and a NaOH/urea aqueous solution), and the regenerated cellulose was used to produce cellulose nanocrystals using acid hydrolysis. The results revealed that the nanocrystals (RCNC-H) obtained after the treatment in sulfuric acid had a hybrid crystalline structure and a needle-like shape with an aspect ratio of about 15.2, while cotton fabric was completely dissolved in the NaOH/urea aqueous solution, and the regenerated nanocrystals (RCNC-N) displayed a typical crystalline form of cellulose II with a higher crystallinity and a shorter rod-like shape with an aspect ratio of about 6.3. The reinforcing effects of RCNC-H and RCNC-N were evaluated using polyvinyl alcohol (PVA) films as a model, where the addition of RCNC-H resulted in a relatively better tensile strength and oxygen barrier property, and the PVA/RCNC-N films had a slightly lower water vapor permeability. Therefore, this work suggests a new possibility for altering the naturally formed nanostructure of cellulose for different applications.

Production and Characterization of Cellulose Nanocrystals from Eucalyptus Dissolving Pulp Using Endoglucanases from Myceliophthora thermophila

Endoglucanase (EG) is a key enzyme during enzymatic preparation of cellulose nanocrystals (CNCs). Myceliophthora thermophila is a thermophilic fungus that has thermal properties and a high secretion of endoglucanases (EGs), and could serve as potential sources of EGs for the preparation of CNCs. In this work, four different GH families (GH5, GH7, GH12, and GH45) of EGs from M. thermophila were expressed and purified, and their enzymatic characteristics and feasibility of application in CNC preparation were investigated. It was shown that the MtEG5A from M. thermophila has good potential in the enzymatic preparation of CNCs using eucalyptus dissolving pulp as feedstock. It was also observed that there was a synergistic effect between the MtEG5A and other MtEGs in the preparation of CNCs, which improved the yield and properties of CNCs obtained by enzymatic hydrolysis. This study provides a reference for understanding the enzymatic characteristics of different families of EGs from M. thermophile and their potential application in nanocellulose production.

Effect of Acetylation of Two Cellulose Nanocrystal Polymorphs on Processibility and Physical Properties of Polylactide/Cellulose Nanocrystal Composite Film

Polylactide (PLA) has become a popular alternative for petroleum-based plastics to reduce environmental pollution. The broader application of PLA is hampered by its brittle nature and incompatibility with the reinforcement phase. The aim of our work was to improve the ductility and compatibility of PLA composite film and investigate the mechanism by which nanocellulose enhances PLA polymer. Here, we present a robust PLA/nanocellulose hybrid film. Two different allomorphic cellulose nanocrystals (CNC-I and CNC-III) and their acetylated products (ACNC-I and ACNC-III) were used to realize better compatibility and mechanical performance in a hydrophobic PLA matrix. The tensile stress of the composite films with 3% ACNC-I and ACNC-III increased by 41.55% and 27.22% compared to pure PLA film, respectively. Compared to the CNC-I or CNC-III enhanced PLA composite films, the tensile stress of the films increased by 45.05% with 1% ACNC-I and 56.15% with 1% ACNC-III. In addition, PLA composite films with ACNCs showed better ductility and compatibility because the composite fracture gradually transitioned to a ductile fracture during the stretching process. As a result, ACNC-I and ACNC-III were found to be excellent reinforcing agents for the enhancement of the properties of polylactide composite film, and the replacement some petrochemical plastics with PLA composites would be very promising in actual life.

Preparation and Characterization of Cellulose Nanocrystals from Bamboos and Their Application in Cassava Starch-Based Film

Cellulose from different species of bamboo (Thyrsostachys siamesi Gamble, Dendrocalamus sericeus Munro (DSM), Bambusa logispatha, and Bambusa sp.) was converted to cellulose nanocrystals (CNCs) by a chemical-mechanical method. First, bamboo fibers were pre-treated (removal of lignin and hemicellulose) to obtain cellulose. Next, the cellulose was hydrolyzed with sulfuric acid using ultrasonication to obtain CNCs. The diameters of CNCs are in the range of 11-375 nm. The CNCs from DSM showed the highest yield and crystallinity, which was chosen in the film fabrication. The plasticized cassava starch-based films with various amounts (0-0.6 g) of CNCs (from DSM) were prepared and characterized. As the number of CNCs in cassava starch-based films increased, water solubility and the water vapor permeability of CNCs decreased. In addition, the atomic force microscope of the nanocomposite films showed that CNC particles were dispersed uniformly on the surface of cassava starch-based film at 0.2 and 0.4 g content. However, the number of CNCs at 0.6 g resulted in more CNC agglomeration in cassava starch-based films. The 0.4 g CNC in cassava starch-based film was found to have the highest tensile strength (4.2 MPa). Cassava starch-incorporated CNCs from bamboo film can be applied as a biodegradable packaging material.

Thiol-Surface-Engineered Cellulose Nanocrystals in Favor of Copper Ion Uptake

Cellulose, the most abundant natural polymer on earth, has recently gained attention for a large spectrum of applications. At a nanoscale, nanocelluloses (mainly involving cellulose nanocrystals or cellulose nanofibrils) possess many predominant features, such as highly thermal and mechanical stability, renewability, biodegradability and non-toxicity. More importantly, the surface modification of such nanocelluloses can be efficiently obtained based on the native surface hydroxyl groups, acting as metal ions chelators. Taking into account this fact, in the present work, the sequential process involving chemical hydrolysis of cellulose and autocatalytic esterification using thioglycolic acid was performed to obtain thiol-functionalized cellulose nanocrystals. The change in chemical compositions was attributed to thiol-functionalized groups and explored via the degree of substitution using a back titration method, X-ray powder diffraction, Fourier-transform infrared spectroscopy and thermogravimetric analysis. Cellulose nanocrystals were spherical in shape and ca. 50 nm in diameter as observed via transmission electron microscopy. The adsorption behavior of such a nanomaterial toward divalent copper ions from an aqueous solution was also assessed via isotherm and kinetic studies, elucidating a chemisorption mechanism (ion exchange, metal chelation and electrostatic force) and processing its operational parameters. In contrast to an inactive configure of unmodified cellulose, the maximum adsorption capacity of thiol-functionalized cellulose nanocrystals toward divalent copper ions from an aqueous solution was 4.244 mg g^-1 at a pH of 5 and at room temperature.

Perovskite-Nanocrystal-Doped Cellulose Nanocrystal Ligands for Electrospun Nanofibers with Excellent Stability

Because of their exceptional physical and thermal properties, cellulose nanocrystals (CNCs) are a highly promising bio-based material for reinforcing fillers. Studies have revealed that some functional groups from CNCs can be used as a capping ligand to coordinate with metal nanoparticles or semiconductor quantum dots during the fabrication of novel complex materials. Therefore, through CNCs ligand encapsulation and electrospinning, perovskite-NC-embedded nanofibers with exceptional optical and thermal stability are demonstrated. The results indicate that, after continuous irradiation or heat cycling, the relative photoluminescence (PL) emission intensity of the CNCs-capped perovskite-NC-embedded nanofibers is maintained at ≈90%. However, the relative PL emission intensity of both ligand-free and long-alkyl-ligand-doped perovskite-NC-embedded nanofibers decrease to almost 0%. These results are attributable to the formation of specific clusters of perovskite NCs along with the CNCs structure and thermal property improvement of polymers. CNCs-doped luminous complex materials offer a promising avenue for stability-demanding optoelectronic devices and other novel optical applications.

All-oil Constructs Stabilized by Cellulose Nanocrystal Surfactants

Constructing all-oil systems with desired geometries and responsiveness would produce a new class of reconfigurable materials that can be used for applications that are not compatible with water or aqueous systems, a fascinating goal to achieve but severely limited by the lack of surfactants. Here, we demonstrate an efficient strategy to stabilize oil-oil interfaces by using the co-assembly between the cellulose nanocrystal and amine-functionalized polyhedral oligomeric silsesquioxane (POSS-NH₂). Cellulose nanocrystal surfactants (CNCSs) form and assemble in situ at the interface, showing significantly enhanced binding energy and acid-dependent interfacial activity. When CNCSs jam at the interface, a robust assembly with exceptional mechanical properties can be achieved, allowing the 3D printing of all-oil devices on demand. Using CNCSs as emulsifiers, oil-in-oil high internal phase emulsions can be prepared by one-step homogenization and, when used as templates, porous materials that require water-sensitive monomers can be synthesized. These results open a new platform for stabilizing and structuring all-oil systems, providing numerous applications for microreactors, encapsulation, delivery, and tissue engineering scaffolds.

Cellulose Nanocrystals Induced Loose and Porous Graphite Phase Carbon Nitride/Porous Carbon Composites for Capturing and Determining of Organochlorine Pesticides from Water and Fruit Juice by Solid-Phase Microextraction

Herein, novel, loose, and porous graphite phase carbon nitride/porous carbon (g-C₃N₄@PC) composites were prepared by decorating cellulose nanocrystals (CNCs). The characterization results demonstrate that the as-prepared composites presented high specific surface areas, porous structures, and abundant chemical groups, with the modification of CNCs. In view of the unique advantages, g-C₃N₄@PC was used as the coating material for the solid-phase microextraction (SPME) of organochlorine pesticides (OCPs) in water and juice samples. The g-C₃N₄@PC-coated fibers showed better extraction efficiencies than commercial fibers (100/7 μm PDMS and PA) toward the OCPs, with the enrichment factors of the g-C₃N₄@PC-coated fibers 5-30 times higher than the latter. Using a gas chromatography-mass spectrometry (GC-MS) instrument, the g-C₃N₄@PC-coated fibers exhibited a gratifying analytical performance for determining low concentrations of OCPs, with a wide linear range (0.1-1600 ng L^-1 for water; 0.1-1000 ng L^-1 for juice), low limits of detection (0.0141-0.0942 ng L^-1 for water; 0.0245-0.0777 ng L^-1 for juice), and good reproducibility and repeatability in optimal conditions. The established method showed good sensitivity and recovery in the determination of OCPs in the water and fruit juice samples, which displayed broad prospects for analyzing organic pollutants from environmental samples.