Enhancing Mechanical and Antimicrobial Properties of Dialdehyde Cellulose-Silver Nanoparticle Composites through Ammoniated Nanocellulose Modification

Given the widespread prevalence of viruses, there is an escalating demand for antimicrobial composites. Although the composite of dialdehyde cellulose and silver nanoparticles (DAC@Ag1) exhibits excellent antibacterial properties, its weak mechanical characteristics hinder its practical applicability. To address this limitation, cellulose nanofibers (CNFs) were initially ammoniated to yield N-CNF, which was subsequently incorporated into DAC@Ag1 as an enhancer, forming DAC@Ag1/N-CNF. We systematically investigated the optimal amount of N-CNF and characterized the DAC@Ag1/N-CNF using FT-IR, XPS, and XRD analyses to evaluate its additional properties. Notably, the optimal mass ratio of N-CNF to DAC@Ag1 was found to be 5:5, resulting in a substantial enhancement in mechanical properties, with a 139.8% increase in tensile elongation and a 33.1% increase in strength, reaching 10% and 125.24 MPa, respectively, compared to DAC@Ag1 alone. Furthermore, the inhibition zones against Escherichia coli and Staphylococcus aureus were significantly expanded to 7.9 mm and 15.9 mm, respectively, surpassing those of DAC@Ag1 alone by 154.8% and 467.9%, indicating remarkable improvements in antimicrobial efficacy. Mechanism analysis highlighted synergistic effects from chemical covalent bonding and hydrogen bonding in the DAC@Ag1/N-CNF, enhancing the mechanical and antimicrobial properties significantly. The addition of N-CNF markedly augmented the properties of the composite film, thereby facilitating its broader application in the antimicrobial field.

Biomass Solid-State Electrolyte with Abundant Ion and Water Channels for Flexible Zinc-Air Batteries

Flexible zinc-air batteries are the leading candidates as the next-generation power source for flexible/wearable electronics. However, constructing safe and high-performance solid-state electrolytes (SSEs) with intrinsic hydroxide ion (OH-) conduction remains a fundamental challenge. Herein, by adopting the natural and robust cellulose nanofibers (CNFs) as building blocks, the biomass SSEs with penetrating ion and water channels are constructed by knitting the OH--conductive CNFs and water-retentive CNFs together via an energy-efficient tape casting. Benefiting from the abundant ion and water channels with interconnected hydrated OH- wires for fast OH- conduction under a nanoconfined environment, the biomass SSEs reveal the high water-uptake, impressive OH- conductivity of 175 mS cm-1 and mechanical robustness simultaneously, which overcomes the commonly existed dilemma between ion conductivity and mechanical property. Remarkably, the flexible zinc-air batteries assemble with biomass SSEs deliver an exceptional cycle lifespan of 310 h and power density of 126 mW cm-2. The design methodology for water and ion channels opens a new avenue to design high-performance SSEs for batteries.

Cellulose Nanofiber-Based Triboelectric Nanogenerators for Efficient Air Filtration in Harsh Environments

Advanced portable healthcare devices with high efficiencies, small pressure drops, and high-temperature resistance are urgently desired in harsh environments with high temperatures, high humidities, and high levels of atmospheric pollution. Triboelectric nanogenerators (TENGs), which serve as energy converters in a revolutionary self-powered sensor device, present a sustainable solution for meeting these requirements. In this work, we developed a porous negative triboelectric material by synthesizing ZIF-8 on the surface of a cellulose/graphene oxide aerogel, grafting it with trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane, and adding a negative corona treatment, and it was combined with a positive triboelectric material to create a cellulose nanofiber-based TENG self-powered filter. The devices achieved a balance between a small pressure drop (53 Pa) and high filtration efficiency (98.97%, 99.65%, and 99.93% for PM0.3, PM0.5, and PM1, respectively), demonstrating robust filtration properties at high temperatures and high humidities. Our work provides a new approach for developing self-powered wearable healthcare devices with excellent air filtration properties.

Advanced Functionalized Materials Based on Layer-by-Layer Assembled Natural Cellulose Nanofiber for Electrodes: A Review

The depletion of fossil fuel resources and its impact on the environment provide a compelling motivation for the development of sustainable energy sources to meet the increasing demand for energy. Accordingly, research and development of energy storage devices have emerged as a critical area of focus. The electrode materials are critical in the electrochemical performance of energy storage devices, such as energy storage capacity and cycle life. Cellulose nanofiber (CNF) represents an important substrate with potentials in the applications of green electrode materials due to their environmental sustainability and excellent compatibility. By utilizing the layer-by layer (LbL) process, well-defined nanoscale multilayer structure is prepared on a variety of substrates. In recent years, increasing attention has focused on electrode materials produced from LbL process on CNFs to yield electrodes with exceptional properties, such as high specific surface area, outstanding electrical conductivity, superior electrochemical activity, and exceptional mechanical stability. This review provides a comprehensive overview on the development of functional CNF via the LbL approach as electrode materials.

Nanofibers from soybean hull insoluble polysaccharides as Pickering stabilizers in oil-in-water emulsions formulated under acidic conditions

BACKGROUND

Pickering emulsions are a kind of emulsion stabilized by solid particles. These particles generate a physical or mechanical barrier that provides long-term stability to emulsion. Cellulose nanofibers are effective Pickering emulsifiers given their long length, high flexibility and entanglement capability. In this work, soybean hull insoluble polysaccharides (HIPS) were used as source of cellulose nanofibers by using a combination of chemical and mechanical treatment. The chemical composition, morphology, flow behavior, water holding capacity (WHC) and emulsifying properties of the nanofibers were studied.

RESULTS

Nanofibers with diameters between 35 and 110 nm were obtained. The WHC increased significantly after the mechanical treatment, and the rheological behavior of the nanofibers was typical of cellulosic materials. Nanofibers were effective emulsifiers in oil-in-water (O/W) emulsions formulated under acidic conditions, without the need of using any additional surfactant. Emulsions were not affected by changes in the pH of the medium (3.00-5.00), and were stable to coalescence.

CONCLUSION

It is possible that cellulose nanofibers form an entangled network which acts as a mechanical steric barrier, providing stability to coalescence. These results are important for the development of effective O/W Pickering emulsifiers/stabilizers, with large applications in the food industry. © 2023 Society of Chemical Industry.

Bionanocomposite Based on Cassava Waste Starch, Locust Bean Galactomannan, and Cassava Waste Cellulose Nanofibers

Natural polysaccharides are among the renewable sources with great potential for replacing petroleum-derived chemicals as precursors to produce biodegradable films. This study aimed to prepare biopolymeric films using starch extracted from the periderm and cortex of cassava roots (waste from cassava root processing), locust bean galactomannan, and cellulose nanofibers also obtained from cassava waste. The films were prepared by casting, and their physicochemical, mechanical, and biodegradability properties were evaluated. The content of cellulose nanofibers varied from 0.5 to 2.5%. Although the addition of cellulose nanofibers did not alter the mechanical properties of the films, it significantly enhanced the vapor barrier of the films (0.055 g mm/m2 h kPa-2.5% nanofibers) and their respective stabilities in aqueous acidic and alkaline media. All prepared films were biodegradable, with complete degradation occurring within five days. The prepared films were deemed promising alternatives for minimizing environmental impacts caused by the disposal of petroleum-derived materials.

Green Preparation and Functional Properties of Reinforced All-Cellulose Membranes Made from Corn Straw

In this study, all-cellulose nanocomposite (ACNC) was successfully prepared through a green and sustainable approach by using corn stalk as raw material, water as regeneration solvent, and recyclable two-component ionic liquid/DMSO as the solvent to dissolve cellulose. The morphology and structural properties of ACNC were determined by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis, indicating homogeneity and good crystallinity. In addition, a comprehensive characterization of ACNC showed that CNF not only improved the thermal stability and mechanical characteristics of ACNC, but also significantly improved the oxygen barrier performance. The ACNC prepared in this work has a good appearance, smooth surface, and good optical transparency, which provides a potential application prospect for converting cellulose wastes such as corn straws into biodegradable packaging materials and electronic device encapsulation materials.

Integral Valorization of Posidonia oceanica Balls: An Abundant and Potential Biomass

Posidonia oceanica balls (POB), a kind of seagrass, are a significant environmental issue since they are annually discharged onto beaches. Their current usefulness limits interest in their management and enhances the environmental problem. Therefore, in this research, the potential of this lignocellulosic biomass was studied from a holistic biorefinery point of view. To this end, an in-depth study was carried out to select the best pathway for the integral valorization of POBs. First, an autohydrolysis process was studied for the recovery of oligosaccharides. Then, a delignification stage was applied, where, in addition to studying different delignification methods, the influence of the autohydrolysis pre-treatment was also investigated. Finally, cellulose nanofibers (CNFs) were obtained through a chemo-mechanical treatment. The results showed that autohydrolysis not only improved the delignification process and its products, but also allowed the hemicelluloses to be valorized. Acetoformosolv delignification proved to be the most successful in terms of lignin and cellulose properties. However, alkaline delignification was able to extract the highest amount of lignin with low purity. CNFs were also successfully produced from bleached solids. Therefore, the potential of POB as a feedstock for a biorefinery was confirmed, and the pathway should be chosen according to the requirements of the desired end products.

Bioinspired Heterogeneous Construction of Lignocellulose-Reinforced COF Membranes for Efficient Proton Conduction

The exponential interest in covalent organic frameworks (COFs) arises from the direct correlation between their diverse and intriguing properties and the modular design principle. However, the insufficient interlamellar interaction among COF nanosheets greatly hinders the formation of defect-free membranes. Therefore, developing a methodology for the facile fabrication of these materials remains an enticing and highly desirable objective. Herein, ultrahigh proton conductivity and superior stability are achieved by taking advantage of COF composite membranes where 2D TB-COF nanosheets are linked by 1D lignocellulosic nanofibrils (LCNFs) through π-π and electrostatic interactions to form a robust and ordered structure. Notably, the high concentration of -SO3 H groups within the COF pores and the abundant proton transport paths at COFs-LCNFs interfaces impart composite membranes ultrahigh proton conductivity (0.348 S cm-1 at 80 °C and 100% RH). Moreover, the directional migration of protons along the stacked nanochannels of COFs is facilitated by oxygen atoms on the keto groups, as demonstrated by density functional theory (DFT) calculations. The simple design concept and reliable operation of the demonstrated mixed-dimensional composite membrane are expected to provide an ideal platform for next-generation conductive materials.

Evaluation of Functional Spray Coatings for Mitigating the Uptake of Volatile Phenols by Pinot Noir Wine Grapes via Blocking, Absorption, and/or Adsorption

Spray coatings have shown promising potential in preventing the uptake of smoke phenols from wildfires into wine grapes. Three cellulose nanofiber-based coatings with low methoxyl pectin or varying concentrations of chitosan were made into films and their potential for blocking, absorption, or adsorption of phenols (guaiacol, m-cresol, and syringol) was evaluated using a custom-built smoke diffusion box. The coatings were also applied to Pinot noir grapes in a vineyard. GC-MS analysis for smoke phenols from headspace gases of diffusion study and extractions of films indicated that chitosan-based films can block guaiacol and syringol, and all films are able to capture m-cresol. The type of coating and application time in a vineyard did not affect (P < 0.05) physicochemical properties, size, and weight of the berries, whereas chitosan-based coatings resulted in a higher anthocyanin content of berries. This study provided new information about the key mechanisms (i.e., blocking phenols) of coatings to mitigate smoke phenol uptake in wine grapes.

Facile Design of Flexible, Strong, and Highly Conductive MXene-Based Composite Films for Multifunctional Applications

Strong, conductive, and flexible materials with improving ion accessibility have attracted significant attention in electromagnetic interference (EMI) and foldable wearable electronics. However, it still remains a great challenge to realize high performance at the same time for both properties. Herein, a microscale structural design combined with nanostructures strategy to fabricate TOCNF(F)/Ti3 C2 Tx (M)@AgNW(A) composite films via a facile vacuum filtration process followed by hot pressing (TOCNF = TEMPO-oxidized cellulose nanofibrils, NW = nanowires) is described. The comparison reveals that different microscale structures can significantly influence the properties of thin films, especially their electrochemical properties. Impressively, the ultrathin MA/F/MA film with enhanced layer in the middle exhibits an excellent tensile strength of 107.9 MPa, an outstanding electrical conductivity of 8.4 × 106 S m-1 , and a high SSE/t of 26 014.52 dB cm2 g-1 . The assembled asymmetric MA/F/MA//TOCNF@CNT (carbon nanotubes) supercapacitor leads to a significantly high areal energy density of 49.08 µWh cm-2 at a power density of 777.26 µW cm-2 . This study proposes an effective strategy to circumvent the trade-off between EMI performance and electrochemical properties, providing an inspiration for the fabrication of multifunctional films for a wide variety of applications in aerospace, national defense, precision instruments, and next-generation electronics.

High-Performance Graphene Biocomposite Enabled by Fe3+ Coordination for Thermal Management

Emerging biocomposites with excellent heat dissipation capabilities and inherent sustainability are urgently needed to address the cooling issues of modern electronics and growing environmental concerns. However, the moisture stability, mechanical performance, thermal conductivity, and even flame retardancy of biomass-based materials are generally insufficient for practical thermal management applications. Herein, we present a high-performance graphene biocomposite consisting of carboxylated cellulose nanofibers and graphene nanosheets through an evaporation-induced self-assembly and subsequent Fe3+ cross-linking strategy. The Fe3+ coordination plays a critical role in stabilizing the material structure, thereby improving the mechanical strength and water stability of the biocomposite films, and its effect is revealed by density functional theory calculations. The hierarchical structure of the biocomposite films also leads to a high in-plane thermal conductivity of 42.5 W m-1 K-1, enabling a superior heat transfer performance. Furthermore, the resultant biocomposite films exhibit outstanding Joule heating performance with a fast thermal response and long-term stability, improved thermal stability, and flame retardancy. Therefore, such a general strategy and the desired overall properties of the biocomposite films offer wide application prospects for functional and safe thermal management.

A Polyelectrolyte Colloidal Brush Based on Cellulose: Perspectives for Future Applications

This feature article is devoted to the evaluation of different techniques for producing colloidal polyelectrolyte brushes (CPEBs) based on cellulose nanofibers modified with grafted polyacrylates. The paper also reviews the potential applications of these CPEBs in designing electrode materials and as reinforcing additives. Additionally, we discuss our own perspectives on investigating composites with CPEBs. Herein, polyacrylic acid (PAA) was grafted onto the surface of cellulose nanofibers (CNFs) employing a "grafting from" approach. The effect of the PAA shell on the morphological structure of a composite with polypyrrole (PPy) was investigated. The performance of as-obtained CNF-PAA/PPy as organic electrode material for supercapacitors was examined. Furthermore, this research highlights the ability of CNF-PAA filler to act as an additional crosslinker forming a physical sub-network due to the hydrogen bond interaction inside chemically crosslinked polyacrylamide (PAAm) hydrogels. The enhancement of the mechanical properties of the material with a concomitant decrease in its swelling ratio compared to a pristine PAAm hydrogel was observed. The findings were compared with the recent theoretical foundation pertaining to other similar materials.

Plant-Derived Nanocellulose with Antibacterial Activity for Wound Healing Dressing

The medical sector is one of the biggest consumers of single-use materials, and while the insurance of sterile media is non-negotiable, the environmental aspect is a chronic problem. Nanocellulose (NC) is one of the safest and most promising materials that can be used in medical applications due to its valuable properties like biocompatibility and biodegradability, along with its good mechanical properties and high water uptake capacity. However, NC has no bactericidal activity, which is a critical need for the effective prevention of infections in chronic diabetic wound dressing applications. Therefore, in this work, a natural product, propolis extract (PE), was used as an antibacterial agent, in different amounts, together with NC to obtain sponge-like structures (NC/PE). The scanning electron microscope (SEM) images showed well-impregnated cellulose fibers and a more compact structure with the addition of PE. According to the thermogravimetric analysis (TGA), the samples containing PE underwent thermal degradation before the unmodified NC due to the presence of volatile compounds in the extract. However, the peak degradation temperature in the first derivative thermogravimetric curves was higher for all the sponges containing PE when compared to the unmodified NC. The antibacterial efficacy of the samples was tested against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, as well as on two clinically resistant isolates. The samples completely inhibited the development of Staphylococcus aureus, and Pseudomonas aeruginosa was partially inhibited, while Escherichia coli was resistant to the PE action. Considering the physical and biological properties along with the environmental and economic benefits, the development of an NC/PE wound dressing seems promising.

Antibacterial Aerogels-Based Membranes by Customized Colloidal Functionalization of TEMPO-Oxidized Cellulose Nanofibers Incorporating CuO

An innovative colloidal approach is proposed here to carry out the customized functionalization of TEMPO-Oxidized Cellulose Nanofibers (CNF) incorporating non-noble inorganic nanoparticles. A heterocoagulation process is applied between the delignified CNF and as-synthetized CuO nanoparticles (CuO NPs) to formulate mixtures which are used in the preparation of aerogels with antibacterial effect, which could be used to manufacture membranes, filters, foams, etc. The involved components of formulated blending, CNF and CuO NPs, were individually obtained by using a biorefinery strategy for agricultural waste valorization, together with an optimized chemical precipitation, assisted by ultrasounds. The optimization of synthesis parameters for CuO NPs has avoided the presence of undesirable species, which usually requires later thermal treatment with associated costs. The aerogels-based structure, obtained by conventional freeze-drying, acted as 3D support for CuO NPs, providing a good dispersion within the cross-linked structure of the nanocellulose and facilitating direct contact of the antibacterial phase against undesirable microorganisms. All samples showed a positive response against Escherichia coli and Staphylococcus aureus. An increase of the antibacterial response of the aerogels, measured by agar disk diffusion test, has been observed with the increase of CuO NPs incorporated, obtaining the width of the antimicrobial "halo" (nwhalo) from 0 to 0.6 and 0.35 for S. aureus and E. coli, respectively. Furthermore, the aerogels have been able to deactivate S. aureus and E. coli in less than 5 h when the antibacterial assays have been analyzed by a broth dilution method. From CNF-50CuO samples, an overlap in the nanoparticle effect produced a decrease of the antimicrobial kinetic.

Cellulose Nanofiber-Alginate Biotemplated Cobalt Composite Multifunctional Aerogels for Energy Storage Electrodes

Tunable porous composite materials to control metal and metal oxide functionalization, conductivity, pore structure, electrolyte mass transport, mechanical strength, specific surface area, and magneto-responsiveness are critical for a broad range of energy storage, catalysis, and sensing applications. Biotemplated transition metal composite aerogels present a materials approach to address this need. To demonstrate a solution-based synthesis method to develop cobalt and cobalt oxide aerogels for high surface area multifunctional energy storage electrodes, carboxymethyl cellulose nanofibers (CNF) and alginate biopolymers were mixed to form hydrogels to serve as biotemplates for cobalt nanoparticle formation via the chemical reduction of cobalt salt solutions. The CNF-alginate mixture forms a physically entangled, interpenetrating hydrogel, combining the properties of both biopolymers for monolith shape and pore size control and abundant carboxyl groups that bind metal ions to facilitate biotemplating. The CNF-alginate hydrogels were equilibrated in CaCl2 and CoCl2 salt solutions for hydrogel ionic crosslinking and the prepositioning of transition metal ions, respectively. The salt equilibrated hydrogels were chemically reduced with NaBH4, rinsed, solvent exchanged in ethanol, and supercritically dried with CO2 to form aerogels with a specific surface area of 228 m2/g. The resulting aerogels were pyrolyzed in N2 gas and thermally annealed in air to form Co and Co3O4 porous composite electrodes, respectively. The multifunctional composite aerogel's mechanical, magnetic, and electrochemical functionality was characterized. The coercivity and specific magnetic saturation of the pyrolyzed aerogels were 312 Oe and 114 emu/gCo, respectively. The elastic moduli of the supercritically dried, pyrolyzed, and thermally oxidized aerogels were 0.58, 1.1, and 14.3 MPa, respectively. The electrochemical testing of the pyrolyzed and thermally oxidized aerogels in 1 M KOH resulted in specific capacitances of 650 F/g and 349 F/g, respectively. The rapidly synthesized, low-cost, hydrogel-based synthesis for tunable transition metal multifunctional composite aerogels is envisioned for a wide range of porous metal electrodes to address energy storage, catalysis, and sensing applications.

Structure-Property Correlation in Natural Rubber Nanocomposite Foams: A Comparison between Nanoclay and Cellulose Nanofiber Used as Nanofillers

Nanocomposite foams of natural rubber (NR) with 5 phr of two kinds of nanofillers, nanoclay (NC) and cellulose nanofiber (CNF), were produced using the latex mixing method and foaming with azodicarbonamide. The effect of the nanofiller on the structure and mechanical properties of NR foams was investigated through SEM, TEM, tensile tests, WAXD, and compression set measurements. Smaller cells with a narrower distribution were attained in the NC/NR foam when compared to the NR and CNF/NR foams, and the expansion ratio was larger due to the suppression of the shrinkage in the NC/NR foam. The foaming of the NR nanocomposites reduced the size of the filler aggregates and improved the dispersion and alignment of nanofillers in the cell walls. The addition of NC and CNF enhanced the tensile strength of the NR foam by 139% and 62%, respectively, without sacrificing the excellent strain of the NR, due to the acceleration of the strain-induced crystallization and small size of the filler aggregates. The compression set of the NR foam could also be reduced in the NC/NR foam compared with the NR and CNF/NR foams.

Low-Voltage Haze Tuning with Cellulose-Network Liquid Crystal Gels

Being key components of the building envelope, glazing products with tunable optical properties are in great demand because of their potential for boosting energy efficiency and privacy features while enabling the main function of allowing natural light indoors. However, windows and skylights with electric switching of haze and transparency are rare and often require high voltages or electric currents, as well as not fully meet the stringent technical requirements for glazing applications. Here, by introducing a predesigned gel material we describe an approach dubbed "Haze-Switch" that involves low-voltage tuning of the haze coefficient in a broad range of 2-90% while maintaining high visible-range optical transmittance. The approach is based on a nanocellulose fiber gel network infiltrated by a nematic liquid crystal, which can be switched between polydomain and monodomain spatial patterns of optical axis via a dielectric coupling between the nematic domains and the applied external electric field. By utilizing a nanocellulose network of nanofibers ∼10 nm in diameter we achieve <10 V dielectric switching and <2% haze in the clear state, as needed for applications in window products. We characterize physical properties relevant to window and smart glass technologies, like the color rendering index, haze coefficient, and switching times, demonstrating that our material and envisaged products can meet the stringent requirements of the glass industry, including applications such as privacy windows, skylights, sunroofs, and daylighting.

Nanocellulose from Cocoa Shell in Pickering Emulsions of Cocoa Butter in Water: Effect of Isolation and Concentration on Its Stability and Rheological Properties

There is a growing interest in developing new strategies to completely or partially replace cocoa butter in food and cosmetic products due to its cost and health effects. One of these alternatives is to develop stable emulsions of cocoa butter in water. However, incorporating cocoa butter is challenging as it solidifies and forms crystals, destabilizing the emulsion through arrested coalescence. Prevention against this destabilization mechanism is significantly lower than against coalescence. In this research, the rheological properties of nanocellulose from cocoa shell, a by-product of the chocolate industry, were controlled through isolation treatments to produce nanocellulose with a higher degree of polymerization (DP) and a stronger three-dimensional network. This nanocellulose was used at concentrations of 0.7 and 1.0 wt %, to develop cocoa butter in-water Pickering emulsion using a high shear mixing technique. The emulsions remained stable for more than 15 days. Nanocellulose was characterized using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), hot water and organic extractives, atomic force microscopy (AFM), degree of polymerization (DP), and rheological analysis. Subsequently, the emulsions were characterized on days 1 and 15 after their preparation through photographs to assess their physical stability. Fluorescent and electronic microscopy, as well as rheological analysis, were used to understand the physical properties of emulsions.

The Fast and One-Step Growth of ZnO Nanorods on Cellulose Nanofibers for Highly Sensitive Photosensors

Cellulose is the most abundant organic material on our planet which has a key role in our daily life (e.g., paper, packaging). In recent years, the need for replacing fossil-based materials has expanded the application of cellulose and cellulose derivatives including into electronics and sensing. The combination of nanostructures with cellulose nanofibers (CNFs) is expected to create new opportunities for the development of innovative electronic devices. In this paper, we report on a single-step process for the low temperature (<100 °C), environmentally friendly, and fully scalable CNF-templated highly dense growth of zinc oxide (ZnO) nanorods (NRs). More specifically, the effect of the degree of substitution of the CNF (enzymatic CNFs and carboxymethylated CNFs with two different substitution levels) on the ZnO growth and the application of the developed ZnO NRs/CNF nanocomposites in the development of UV sensors is reported herein. The results of this investigation show that the growth and nature of ZnO NRs are strongly dependent on the charge of the CNFs; high charge promotes nanorod growth whereas with low charge, ZnO isotropic microstructures are created that are not attached to the CNFs. Devices manufactured via screen printing/drop-casting of the ZnO NRs/CNF nanocomposites demonstrate a good photo-sensing response with a very stable UV-induced photocurrent of 25.84 µA. This also exhibits excellent long-term stability with fast ON/OFF switching performance under the irradiance of a UV lamp (15 W).

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.

Water-Induced Cellulose Nanofibers/Poly(vinyl alcohol) Hydrogels Regulated by Hydrogen Bonding for In Situ Water Shutoff

Hydrogels have been widely applied to the water shutoff in oilfields due to their excellent three-dimensional network and thermal and physicochemical stability, and it is still a huge challenge to develop new hydrogels with simple preparation, low cost, and high mechanical performance that can meet the requirements of practical applications. Herein, we devised a simple and universal manufacturing method for regulating the hydrogen bonds between poly(vinyl alcohol) (PVA) and cellulose nanofibers (CNF) via the water-diffusion action, thus fabricating a physically tough PVA-CNF hydrogel for the in situ water shutoff. This method allowed the polymer chains to strengthen the molecular interactions between polymers upon replacing with water (a poor solvent) to regulate the cross-linking structure, characterizing by the nano-crystallinity domains and fibrillar segments, which also accounted for the thermal stability, extraordinary elasticity, high stretchability, and toughness of PVA-CNF hydrogel. Further, the obtained PVA-CNF hydrogel exhibited superb plugging performance, that is, the breakthrough pressure gradient could reach 71.56 MPa·m-1, surpassing all currently reported gelling water shutoff agents. This water-induced in situ hydrogelation made it well suited as a water shutoff agent in oilfields and may provide a promising strategy to fabricate mechanically robust smart materials for the water shutoff projects with low cost, simple processing, and high efficiency.

Stabilization of Beeswax-In-Water Dispersions Using Anionic Cellulose Nanofibers and Their Application in Paper Coating

Beeswax is a bio-sourced, renewable, and even edible material that stands as a convincing option to provide paper-based food packaging with moisture resistance. Nonetheless, the difficulty of dispersing it in water limits its applicability. This work uses oxidized, negatively charged cellulose nanofibers along with glycerol to stabilize beeswax-in-water emulsions above the melting point of the wax. The synergistic effects of nanocellulose and glycerol granted the stability of the dispersion even when it cooled down, but only if the concentration of nanofibers was high enough. This required concentration (0.6-0.9 wt%) depended on the degree of oxidation of the cellulose nanofibers. Rheological hindrance was essential to prevent the buoyancy of beeswax particles, while the presence of glycerol prevented excessive aggregation. The mixtures had yield stress and showed pseudoplastic behavior at a high enough shear rate, with their apparent viscosity being positively influenced by the surface charge density of the nanofibers. When applied to packaging paper, the nanocellulose-stabilized beeswax suspensions not only enhanced its barrier properties towards liquid water (reaching a contact angle of 96°) and water vapor (<100 g m-2 d-1), but also to grease (Kit rating: 5) and airflow (>1400 Gurley s). While falling short of polyethylene-coated paper, this overall improvement, attained using only one layer of a biobased coating suspension, should be understood as a step towards replacing synthetic waxes and plastic laminates.

Dispersion of Cellulose Nanofibers in Methacrylate-Based Nanocomposites

Poly(methylmethacrylate-co-methacrylic acid) (PMMA-co-MAA) polymers were prepared via cobalt-mediated free radical copolymerization and were characterized after synthesis. The synthesis led to a 98.5% conversion and a final ratio between the two units, MMA/MAA, was equal to 63:37 mol%. PMMA-co-MAA was then used as a matrix for cellulose-based nanocomposites to tailor filler compatibility, thanks to the presence of carboxylic groups capable of generating strong H-bonds with the cellulose surface. Cellulose nanofibers (CNFs) were dispersed using a solution with a mixture of two solvents to tailor compatibility of both the components. For this purpose, CNFs were successfully re-dispersed in methanol using the solvent exchange method and tetrahydrofuran/methanol mixtures at different ratios were used for the preparation of the films. Fully transparent films of PMMA-co-MAA + CNF were prepared up to 15 wt% of CNF with a good dispersion in the matrix. This dispersion state leads to the reinforcement of the polymethacrylate matrix, increasing its tensile strength whilst preserving optical transparency.

Exploring the Potential of Seaweed Derivatives for the Development of Biodegradable Plastics: A Comparative Study

Biodegradable films made from biopolymer materials have the potential to replace conventional plastics, which can reduce waste disposal problems. This study aims to explore the potential of different seaweed derivate films consisting of 2% (w/w) of kappaphycus alverezi (KA), kappa carrageenan (KC), refined carrageenan (RC) and semi-refined carrageenan (SRC) as bio-based materials with 0.9% (w/w) glycerol (G), and reinforced with different concentrations of cellulose nanofibers (CNFs) derived from palm waste. A characterization of the glycerol-plasticized seaweed derivatives containing 0, 5, 10, and 15% (v/w) cellulose nanofiber is carried out. The CNFs were studied based on their mechanical, physical and thermal properties including mechanical properties, thickness, moisture content, opacity, water solubility, water vapor permeability and thermal stability. The hydrogen bonding was determined using the DFT calculation generated by Gauss view software version 9.6. The KA + G + 10%CNF film exhibited a surface with slight cracks, roughness, and larger lumps and dents, resulting in inferior mechanical properties (18.50 Mpa), making it unsuitable for biofilm production. The KC + G + 10%CNF film exhibited mechanical properties 24.97 Mpa and water vapor permeability of 1.42311 × 10^-11 g s^-1 m^-1 Pa^-1. The RC/G/10%CNF film displayed the highest TS (48.23 MPa) and water vapor permeability (1.4168 × 10^-11 g s^-1 m^-1 Pa^-1), but it also had higher solubility in water (66%). In contrast, the SRC + G + 10%CNF film demonstrated excellent mechanical properties (45.98 MPa), low water solubility (42.59%), low water vapor permeability (1.3719 × 10^-11 g s^-1 m^-1 Pa^-1), and a high decomposition temperature (250.62 °C) compared to KA, KC and RC. These attributes develop films suitable for various applications, including food packaging with enhanced properties and stability.

Synergies between Fibrillated Nanocellulose and Hot-Pressing of Papers Obtained from High-Yield Pulp

To extend the application of cost-effective high-yield pulps in packaging, strength and barrier properties are improved by advanced-strength additives or by hot-pressing. The aim of this study is to assess the synergic effects between the two approaches by using nanocellulose as a bulk additive, and by hot-pressing technology. Due to the synergic effect, dry strength increases by 118% while individual improvements are 31% by nanocellulose and 92% by hot-pressing. This effect is higher for mechanical fibrillated cellulose. After hot-pressing, all papers retain more than 22% of their dry strength. Hot-pressing greatly increases the paper's ability to withstand compressive forces applied in short periods of time by 84%, with a further 30% increase due to the synergic effect of the fibrillated nanocellulose. Hot-pressing and the fibrillated cellulose greatly decrease air permeability (80% and 68%, respectively) for refining pretreated samples, due to the increased fiber flexibility, which increase up to 90% using the combined effect. The tear index increases with the addition of nanocellulose, but this effect is lost after hot-pressing. In general, fibrillation degree has a small effect which means that low- cost nanocellulose could be used in hot-pressed papers, providing products with a good strength and barrier capacity.

Interfacial Super-Assembly of Intertwined Nanofibers toward Hybrid Nanochannels for Synergistic Salinity Gradient Power Conversion

Capturing the abundant salinity gradient power into electric power by nanofluidic systems has attracted increasing attention and has shown huge potential to alleviate the energy crisis and environmental pollution problems. However, not only the imbalance between permeability and selectivity but also the poor stability and high cost of traditional membranes limit their scale-up realistic applications. Here, intertwined "soft-hard" nanofibers/tubes are densely super-assembled on the surface of anodic aluminum oxide (AAO) to construct a heterogeneous nanochannel membrane, which exhibits smart ion transport and improved salinity gradient power conversion. In this process, one-dimensional (1D) "soft" TEMPO-oxidized cellulose nanofibers (CNFs) are wrapped around "hard" carbon nanotubes (CNTs) to form three-dimensional (3D) dense nanochannel networks, subsequently forming a CNF-CNT/AAO hybrid membrane. The 3D nanochannel networks constructed by this intertwined "soft-hard" nanofiber/tube method can significantly enhance the membrane stability while maintaining the ion selectivity and permeability. Furthermore, benefiting from the asymmetric structure and charge polarity, the hybrid nanofluidic membrane displays a low membrane inner resistance, directional ionic rectification characteristics, outstanding cation selectivity, and excellent salinity gradient power conversion performance with an output power density of 3.3 W/m². Besides, a pH sensitive property of the hybrid membrane is exhibited, and a higher power density of 4.2 W/m² can be achieved at a pH of 11, which is approximately 2 times more compared to that of pure 1D nanomaterial based homogeneous membranes. These results indicate that this interfacial super-assembly strategy can provide a way for large-scale production of nanofluidic devices for various fields including salinity gradient energy harvesting.

Covalent Crosslinking Cellulose/Graphene Aerogels with High Elasticity and Adsorbability for Heavy Metal Ions Adsorption

With the fast development of modern industry, heavy metal contaminant became more severe. How to remove heavy metal ions in water in a green and efficient way is a prominent problem in current environmental protection. The adsorption of cellulose aerogel as a novel heavy metal removal technology has many advantages, including abundant resources, environmental friendly, high specific surface, high porosities and without second pollution, which means it has a wide application prospect. Here, we reported a self-assembly and covalent crosslinking strategy to prepare elastic and porous cellulose aerogels using PVA and graphene and cellulose as precursor. The resulting cellulose aerogel had a low density of 12.31 mg cm^-3 and excellent mechanical properties, which can recover to its initial form at 80% compressive strain. Meanwhile, the cellulose aerogel had strong adsorption capacity of Cu²⁺ (80.12 mg g^-1), C_d²⁺ (102.23 mg g^-1), Cr³⁺ (123.02 mg g^-1), Co²⁺ (62.38 mg g^-1), Zn²⁺ (69.55 mg g^-1), and Pb²⁺ (57.16 mg g^-1). In addition, the adsorption mechanism of the cellulose aerogel was investigated using adsorption kinetics and adsorption isotherm, and the conclusion was that the adsorption process was mainly controlled by chemisorption mechanism. Therefore, cellulose aerogel, as a kind of green adsorption material, has a very high application potential in future water treatment applications.

Nanotechnology Applied to Cellulosic Materials

In recent years, nanocellulosic materials have attracted special attention because of their performance in different advanced applications, biodegradability, availability, and biocompatibility. Nanocellulosic materials can assume three distinct morphologies, including cellulose nanocrystals (CNC), cellulose nanofibers (CNF), and bacterial cellulose (BC). This review consists of two main parts related to obtaining and applying nanocelluloses in advanced materials. In the first part, the mechanical, chemical, and enzymatic treatments necessary for the production of nanocelluloses are discussed. Among chemical pretreatments, the most common approaches are described, such as acid- and alkali-catalyzed organosolvation, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, ammonium persulfate (APS) and sodium persulfate (SPS) oxidative treatments, ozone, extraction with ionic liquids, and acid hydrolysis. As for mechanical/physical treatments, methods reviewed include refining, high-pressure homogenization, microfluidization, grinding, cryogenic crushing, steam blasting, ultrasound, extrusion, aqueous counter collision, and electrospinning. The application of nanocellulose focused, in particular, on triboelectric nanogenerators (TENGs) with CNC, CNF, and BC. With the development of TENGs, an unparalleled revolution is expected; there will be self-powered sensors, wearable and implantable electronic components, and a series of other innovative applications. In the future new era of TENGs, nanocellulose will certainly be a promising material in their constitution.

A Single Electronic Tattoo for Multisensory Integration

Wearable electronics are garnering growing interest in various emerging fields including intelligent sensors, artificial limbs, and human-machine interfaces. A remaining challenge is to develop multisensory devices that can conformally adhere to the skin even during dynamic-moving environments. Here, a single electronic tattoo (E-tattoo) based on a mixed-dimensional matrix network, which integrates two-dimensional  MXene nanosheets and one-dimensional cellulose nanofibers/Ag nanowires, is presented for multisensory integration. The multidimensional configurations endow the E-tattoo with excellent multifunctional sensing capabilities including temperature, humidity, in-plane strain, proximity, and material identification. In addition, benefiting from the satisfactory rheology of hybrid inks, the E-tattoos are able to be fabricated through multiple facile strategies including direct writing, stamping, screen printing, and three-dimensional printing on various hard/soft substrates. Especially, the E-tattoo with excellent triboelectric properties also can serve as a power source for activating small electronic devices. It is believed that these skin-conformal E-tattoo systems can provide a promising platform for next-generation wearable and epidermal electronics.

Polysaccharide Nanofiber-Stabilized Pickering Emulsion Microparticles Induce Pyroptotic Cell Death in Hepatocytes and Kupffer Cells

The intracellular uptake and interaction behavior of emulsion microparticles in liver cells critical to host defense and inflammation is significant to understanding their potential cytotoxicity and biomedical applications. In this study, the cell death responses of fibroblastic, hepatocyte, and Kupffer cells (KCs) induced by four types of emulsion particles that are stabilized by polysaccharide nanofibers (cellulose or chitin), an inorganic nanoparticle (β-tricalcium phosphate), or surfactants are compared. Pickering emulsion (PE) microparticles stabilized by polysaccharide nanofibers or inorganic nanoparticles have a droplet size of 1-3 µm, while the surfactant-stabilized emulsion has a diameter of ≈190 nm. Polysaccharide nanofiber-stabilized PEs (PPEs) markedly induce lactate dehydrogenase release in all cell types. Additionally, characteristic pyroptotic cell death, which is accompanied by cell swelling, membrane blebbing, and caspase-1 activation, occurs in hepatocytes and KCs. These PE microparticles are co-cultured with lipopolysaccharide-primed KCs associated with cytokine interleukin-1β release, and the PPEs demonstrate biological activity as a mediator of the inflammation response. Well-designed PPE microparticles induce pyroptosis of liver cells, which may provide new insight into regulating inflammation-related diseases for designing potent anticancer drugs and vaccine adjuvants.

Fabrication and Characterization of Functional Biobased Membranes from Postconsumer Cotton Fabrics and Palm Waste for the Removal of Dyes

Textile industries currently face vast challenges for the active removal of colored wastewater. Indeed, sustainable, recyclable, and green approaches are still lacking to achieve this aim. Thus, the present study explored the utilization of highly functional, green, recyclable, fully bio-based, and cost-effective composite membranes from post-consumer cotton fabrics and palm waste for wastewater treatment purposes. Highly functional cellulose nanofibers (CNF) were produced from waste cotton fabrics and filter paper using an acid hydrolysis technique. The yield of nanofibers extracted from waste cotton fabrics and filter paper was 76.74 and 54.50%, respectively. The physical, chemical, and structural properties of nanofibers were studied using various advanced analytical techniques. The properties of isolated nanofibers were almost similar and comparable to those of commercial nanofibers. The surface charge densities were -94.0, -80.7, and -90.6 mV for the nanofibers of palm waste, cotton fibers, and filter paper, respectively. After membrane fabrication using vacuum and hot-pressing techniques, the characteristics of the membrane were analyzed. The results showed that the average pore size of the palm-waste membrane was 1.185 nm, while it was 1.875 nm for membrane from waste cotton fibers and filter paper. Congo red and methylene blue dyes were used as model solutions to understand the behavior of available functional groups and the surface ζ-potential of the membrane frameworks' interaction. The membrane made from palm waste had the highest dye removal efficiency, and it was 23% for Congo red and 44% for methylene blue. This study provides insights into the challenges associated with the use of postconsumer textile and agricultural waste, which can be potentially used in high-performance liquid filtration devices for a more sustainable society.

Enhanced Mechanical Stability and Hydrophobicity of Cellulose Aerogels via Quantitative Doping of Nano-Lignin

As a porous biomass sustainable material, cellulose aerogel has attracted significant attention due to its unique properties in various applications. However, its mechanical stability and hydrophobicity are huge obstacles hindering practical applications. In this work, nano-lignin quantitative doping cellulose nanofiber aerogel was successfully fabricated via liquid nitrogen freeze drying combing vacuum oven drying. The impact of various parameters (lignin content, temperature, and matrix concentration) on the property of the as-prepared materials was systematically explored, revealing the optimum conditions. The morphology, mechanical properties, internal structure, and thermal degradation of the as-prepared aerogels were characterized by various methods (compression test, contact angle, SEM, BET, DSC, and TGA). Compared with pure cellulose aerogel, the addition of nano-lignin did not significantly change the pore size and specific surface area of the material but could improve its thermal stability. In particular, the enhanced mechanical stable and hydrophobic properties of cellulose aerogel via the quantitative doping of nano-lignin was confirmed. The mechanical compressive strength of 160-13.5 C/L-aerogel is as high as 0.913 MPa, while the contact angle was nearly reaching 90°. Significantly, this study provides a new strategy for constructing a novel cellulose nanofiber aerogel with mechanical stability and hydrophobicity.

Reinforcement Behavior of Chemically Unmodified Cellulose Nanofiber in Natural Rubber Nanocomposites

We investigated the reinforcement behavior of small amounts of chemically unmodified cellulose nanofiber (CNF) in eco-friendly natural rubber (NR) nanocomposites. For this purpose, NR nanocomposites filled with 1, 3, and 5 parts per hundred rubber (phr) of cellulose nanofiber (CNF) were prepared by a latex mixing method. By using TEM, a tensile test, DMA, WAXD, a bound rubber test, and gel content measurements, the effect of CNF concentration on the structure-property relationship and reinforcing mechanism of the CNF/NR nanocomposite was revealed. Increasing the content of CNF resulted in decreased dispersibility of the nanofiber in the NR matrix. It was found that the stress upturn in the stress-strain curves was remarkably enhanced when the NR was combined with 1-3 phr CNF, and a noticeable increase in tensile strength (an approximately 122% increase in tensile strength over that of NR) was observed without sacrificing the flexibility of the NR in the NR filled with 1 phr CNF, though no acceleration in their strain-induced crystallization was observed. Since the NR chains were not inserted in the uniformly dispersed CNF bundles, the reinforcement behavior by the small content of CNF might be attributed to the shear stress transfer at the CNF/NR interface through the interfacial interaction (i.e., physical entanglement) between the nano-dispersed CNFs and the NR chains. However, at a higher CNF filling content (5 phr), the CNFs formed micron-sized aggregates in the NR matrix, which significantly induced the local stress concentration and promoted strain-induced crystallization, causing a substantially increased modulus but reduced the strain at the rupture of the NR.

Versatile Assembly of Metal-Phenolic Network Foams Enabled by Tannin-Cellulose Nanofibers

Metal-phenolic network (MPN) foams are prepared using colloidal suspensions of tannin-containing cellulose nanofibers (CNFs) that are ice-templated and thawed in ethanolic media in the presence of metal nitrates. The MPN facilitates the formation of solid foams by air drying, given the strength and self-supporting nature of the obtained tannin-cellulose nanohybrid structures. The porous characteristics and (dry and wet) compression strength of the foams are rationalized by the development of secondary, cohesive metal-phenolic layers combined with a hydrogen bonding network involving the CNF. The shrinkage of the MPN foams is as low as 6% for samples prepared with 2.5-10% tannic acid (or condensed tannin at 2.5%) with respect to CNF content. The strength of the MPN foams reaches a maximum at 10% tannic acid (using Fe^(III) ions), equivalent to a compressive strength 70% higher than that produced with tannin-free CNF foams. Overall, a straightforward framework is introduced to synthesize MPN foams whose physical and mechanical properties are tailored by the presence of tannins as well as the metal ion species that enable the metal-phenolic networking. Depending on the metal ion, the foams are amenable to modification according to the desired application.

Borophene Embedded Cellulose Paper for Enhanced Photothermal Water Evaporation and Prompt Bacterial Killing

Solar-driven photothermal water evaporation is considered an elegant and sustainable technology for freshwater production. The existing systems, however, often suffer from poor stability and biofouling issues, which severely hamper their prospects in practical applications. Conventionally, photothermal materials are deposited on the membrane supports via vacuum-assisted filtration or dip-coating methods. Nevertheless, the weak inherent material-membrane interactions frequently lead to poor durability, and the photothermal material layer can be easily peeled off from the hosting substrates or partially dissolved when immersed in water. In the present article, the discovery of the incorporation of borophene into cellulose nanofibers (CNF), enabling excellent environmental stability with a high light-to-heat conversion efficiency of 91.5% and water evaporation rate of 1.45 kg m^-2 h^-1 under simulated sunlight is reported. It is also demonstrated that borophene papers can be employed as an excellent active photothermal material for eliminating almost 100% of both gram-positive and gram-negative bacteria within 20 min under three sun irradiations. The result opens a new direction for the design of borophene-based papers with unique photothermal properties which can be used for the effective treatment of a wide range of wastewaters.

Ice-Crystal-Templated "Accordion-Like" Cellulose Nanofiber/MXene Composite Aerogels for Sensitive Wearable Pressure Sensors

Exfoliated MXene nanosheets are integrated with cellulose nanofibers (CNFs) to form composite aerogels with high electric conductivity. The combination of CNFs and MXene nanosheets forms a unique "accordion-like" hierarchical architecture with MXene-CNF pillared layers through ice-crystal templating. Benefiting from the special "layer-strut" structure, the MXene/CNF composite aerogels have low density (50 mg/cm³), excellent compressibility and recoverability, as well as superior fatigue resistance (up to 1000 cycles). When being used as a piezoresistive sensor, the composite aerogel exhibits high sensitivity upon different strains, stable sensing performance with various compressive frequencies, broad detection range, and quick responsiveness (0.48 s). Moreover, the piezoresistive sensors are shown to have an excellent real-time sensing ability for human motions such as swallowing, arm bending, walking, and running. The composite aerogels also have a low environmental impact with the natural biodegradability of CNFs. The designed composite aerogels can serve as a promising sensing material for developing next-generation sustainable and wearable electronic devices.

Amino-Functionalized Cellulose Nanofiber/Lignosulfonate New Aerogel Adsorbent for the Removal of Dyes and Heavy Metals from Wastewater

Due to the increasingly widespread water pollutants and the high cost of treatment methods, there is a demand for new, inexpensive, renewable, and biodegradable adsorbent materials for the purification of wastewater contaminants. In this study, a new biocomposite aerogel (Amf-CNF/LS) was prepared using a chemically cross-linking method between the amino-functionalized cellulose nanofibers (Amf-CNF) and lignosulfonates (LS). The physical and chemical properties of the prepared aerogel were investigated using several techniques including elemental analysis, scanning electron microscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and N₂ adsorption-desorption analysis. The Amf-CNF/LS aerogel was then applied for the removal of methylene blue (MB), rhodamine B dye (RhB), and the heavy metal cadmium ion (Cd²⁺) from synthetic wastewater solutions. The adsorption parameters controlling the adsorption process including the pH, contact time, adsorbent dosage, and adsorbate concen-tration were optimized. High adsorption kinetics and isotherms were observed, with the adsorption isotherms of the Amf-CNF/LS aerogel fitting the Langmuir model with maximum adsorption capacities of 170.94, 147.28, and 129.87 mg/g for MB, RhB, and Cd²⁺, respectively. These results show that Amf-CNF/LS aerogel is a promising green and inexpensive adsorbent for MB, RhB, and Cd²⁺ removal from wastewater.

Preparation of Cellulose Nanofibers from Corn Stalks by Fenton Reaction: A New Insight into the Mechanism by an Experimental and Theoretical Study

Agricultural biomass wastes are an abundant feedstock for biorefineries. However, most of these wastes are not treated in the right way. Here, corn stalks (CSs) were assigned as the raw material to produce cellulose nanofibers (CNFs) via in situ Fenton oxidation treatment. In order to probe the formation mechanism of an in situ Fenton reactor, the bonding interaction of hydrated Fe²⁺ ions and fiber has been systemically studied based on adsorption experiments, IR spectroscopy, density functional theory (DFT) calculations, and Raman spectroscopy. The results indicate that the coordination of the hydrated Fe²⁺ ion to the fiber generates a quasi-octahedral-coordinated sphere around the Fe center. The Jahn-Teller distortion effect of the Fe center promotes the Fe-O₂H₂ bonding interaction via reduction of the energy gap of the d_z² orbital of the Fe center and π_2py/π_2pz orbitals of the H₂O₂ molecule. The oxidation treatment of the pretreated CS by the in situ Fenton process shows the formation of a new carboxyl group on the fiber surface. The scanning electron microscopy image shows that the Fenton-treated fiber was scattered into the nanosized CNFs with a diameter of up to 50 nm. Both experimental and theoretical studies show that the pseudo-first-order kinetic reaction could describe the in situ Fenton kinetics well. Moreover, the proposed catalytic cycle shows that the large thermodynamic barrier is the cleavage of the O-O bond of H₂O₂ to generate the ^•OH radical, and the whole catalytic cycle is found to be spontaneous at room temperature.

Covalently Functionalized Cellulose Nanoparticles for Simultaneous Enrichment of Pb(II), Cd(II) and Cu(II) Ions

Cellulose nanoparticles are sustainable natural polymers with excellent application in environmental remediation technology. In this work, we synthesized cellulose nanoparticles and covalently functionalized them with a multi-functional group possessing ligands. The hybrid material shows excellent adsorption properties for the simultaneous extraction of multiple metal ions in the sample preparation technique. The sorbent shows excellent sorption capacity in the range of 1.8-2.2 mmol/g of material. The developed method was successfully employed for the simultaneous extraction of Pb(II), Cd(II) and Cu(II) from real-world samples (industrial effluent, river water, tap and groundwater) and subsequently determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). The method shows a preconcentration limit of 0.7 ppb attributes to analyze the trace concentration of studied metal ions. The detection limit obtained for Pb(II), Cd(II) and Cu(II) is found to be 0.4 ppb.

Cellulose Nanofiber-Coated Perfluoropentane Droplets: Fabrication and Biocompatibility Study

Purpose

To study the effect of cellulose nanofiber (CNF)-shelled perfluoropentane (PFP) droplets on the cell viability of 4T1 breast cancer cells with or without the addition of non-encapsulated paclitaxel.

Methods

The CNF-shelled PFP droplets were produced by mixing a CNF suspension and PFP using a homogenizer. The volume size distribution and concentration of CNF-shelled PFP droplets were estimated from images taken with an optical microscope and analyzed using Fiji software and an in-house Matlab script. The thermal stability was qualitatively assessed by comparing the size distribution and concentration of CNF-shelled PFP droplets at room temperature (~22°) and 37°C. The cell viability of 4T1 cells was measured using a 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Additionally, a hemolysis assay was performed to assess blood compatibility of CNF-shelled PFP droplets.

Results

The droplet diameter and concentration of CNF-shelled PFP droplets decreased after 48 hours at both room temperature and 37°C. In addition, the decrease in concentration was more significant at 37°C, from 3.50 ± 0.64×10⁶ droplets/mL to 1.94 ± 0.10×10⁶ droplets/mL, than at room temperature, from 3.65 ± 0.29×10⁶ droplets/mL to 2.56 ± 0.22×10⁶ droplets/mL. The 4T1 cell viability decreased with increased exposure time and concentration of paclitaxel, but it was not affected by the presence of CNF-shelled PFP droplets. No hemolysis was observed at any concentration of CNF-shelled PFP droplets.

Conclusion

CNF-shelled PFP droplets have the potential to be applied as drug carriers in ultrasound-mediated therapy.

Impact of functional spray coatings on smoke volatile phenol compounds and Pinot noir grape growth

The frequency and intensity of wildfires have been increasing over the last 50 years and negatively impacted the wine industry. Previous methods of smoke mitigation during grape processing have shown little impact in reducing smoke taint in wines. Therefore, a novel method of using edible spray coatings for vineyard application was developed to help prevent volatile smoke phenol uptake in wine grapes. Four cellulose nanofiber-based coating suspensions incorporated with chitosan and/or β-cyclodextrin were evaluated. Films derived from the coating suspensions were exposed to volatile phenols found in wildfire smoke (guaiacol, 4-methyl guaiacol, m-cresol, o-cresol, p-cresol, syringol, and 4-methyl syringol) and evaluated with ultraviolet-visible spectroscopy where the results indicated that the coatings could uptake smoke phenols in varying degrees. The coatings were also applied in a vineyard at three different application times during grape growth: pea-sized, pre-bunch closure, and both at pea-sized and pre-bunch closure. The results showed that the application time did not have a significant (p < 0.05) effect on berry size, weight, °Brix, pH, or titratable acidity. The type of coating, time of application and washing were found to impact the number of volatile phenols in the grapes after a smoke event. Results from this study indicated that edible coatings could help mitigate smoke uptake in wine grapes without sacrificing the growth and key composition parameters of wine grapes. PRACTICAL APPLICATION: This research provides a novel spray coating that can be applied to wine grapes in the vineyard to potentially mitigate volatile smoke compounds in wine grapes without impacting fruit growth and key compositional parameters of wine grapes, thus maintaining high quality of wines for consumers. Results from this study can also be potentially applied to other agricultural commodities to solve the issues caused by the wildfire smoke.

Can TEMPO-Oxidized Cellulose Nanofibers Be Used as Additives in Bio-Based Building Materials? A Preliminary Study on Earth Plasters

Interest towards cellulose nanofibers obtained from virgin and waste sources has seen a significant growth, mainly thanks to the increasing sensitivity towards the concept of circular economy and the high levels of paper recycling achieved in recent years. Inspired by the guidelines of the green building industry, this study proposes the production and characterization of TEMPO-oxidized and homogenized cellulose nanofibers (TOHO CNF) from different sources and their use as additives for earth plasters on two different raw earth samples, characterized by geotechnical laboratory tests and mineralogical analysis: a high-plasticity clay (T2) and a medium-compressibility silt (ABS). Original sources, including those derived from waste (recycled cardboard and paper mill sludge), were characterized by determining chemical content (cellulose versus ashes and lignin) and fiber morphology. TOHO CNF derived from the different sources were compared in terms of nanofibers medium diameter, crystallinity degree, thermal decomposition and oxidation degree, that is the content of carboxylic groups per gram of sample. Then, a preliminary analysis of the influence of CNF on earth plasters is examined. Adhesion and capillary absorption tests highlighted the effect of such nanofibers on blends in function of two factors, namely the cellulose original source and the oxidation degree of the fibers. In particular, for both earth samples, T2 and ABS, a significant increase in adhesion strength was observed in the presence of some TOHO CNF additives. As far as capillary sorption tests, while an undesired increase in water adsorption was detected for T2 compared to the control, in the case of ABS, a significant reduction in water content was measured by adding TOHO CNF derived from recycled sources. These results pave the way for further in-depth investigation on the role of TOHO CNF as additives for earth plasters.

Valorization of Vegetable Waste from Leek, Lettuce, and Artichoke to Produce Highly Concentrated Lignocellulose Micro- and Nanofibril Suspensions

Vegetable supply in the world is more than double than vegetable intake, which supposes a significant waste of vegetables, in addition to the agricultural residues produced. As sensitive food products, the reasons for this waste vary from the use of only a part of the vegetable due to its different properties to the product appearance and market image. An alternative high-added-value application for these wastes rich in cellulose could be the reduction in size to produce lignocellulose micro- and nanofibrils (LCMNF). In this sense, a direct treatment of greengrocery waste (leek, lettuce, and artichoke) to produce LCMNFs without the extraction of cellulose has been studied, obtaining highly concentrated suspensions, without using chemicals. After drying the wastes, these suspensions were produced by milling and blending at high shear followed by several passes in the high-pressure homogenizer (up to six passes). The presence of more extractives and shorter fiber lengths allowed the obtention of 5-5.5% leek LCMNF suspensions and 3.5-4% lettuce LCMNF suspensions, whereas for artichoke, only suspensions of under 1% were obtained. The main novelty of the work was the obtention of a high concentration of micro- and nanofiber suspension from the total waste without any pretreatment. These high concentrations are not obtained from other raw materials (wood or annual plants) due to the clogging of the homogenizer, requiring the dilution of the sample up to 1% or the use of chemical pretreatments.

Nanocellulose from Spanish Harvesting Residues to Improve the Sustainability and Functionality of Linerboard Recycling Processes

The hornification processes undergone by the fibers in the paper industry recycling processes lead to the loss of properties of the final products, which exhibit poor mechanical properties. Among the most promising solutions is the reinforcement of secondary fibers with cellulose nanofibers. The present work addresses two important issues: the efficient production of cellulose nanofibers from scarcely exploited agricultural wastes such as horticultural residues and vine shoots, and their application as a reinforcement agent in recycled linerboard recycling processes. The effect of the chemical composition and the pretreatment used on the nanofibrillation efficiency of the fibers was analyzed. Chemical pretreatment allowed a significantly higher nanofibrillated fraction (45−63%) than that produced by mechanical (18−38%), as well as higher specific surface areas (>430 m2/g). The application of the nanofibers as a reinforcing agent in the recycled linerboard considerably improved the mechanical properties (improvements of 15% for breaking length, 220−240% for Young’s modulus and 27% for tear index), counteracting the loss of mechanical properties suffered during recycling when using chemically pretreated cellulose nanofibers from horticultural residues and vine shoots. It was concluded that this technology surpasses the mechanical reinforcement produced by conventional mechanical refining used in the industry and extends the number of recycling cycles of the products due to the non-physical modification of the fibers.

Dynamic Light Scattering Plus Scanning Electron Microscopy: Usefulness and Limitations of a Simplified Estimation of Nanocellulose Dimensions

Measurements of nanocellulose size usually demand very high-resolution techniques and tedious image processing, mainly in what pertains to the length of nanofibers. Aiming to ease the process, this work assesses a relatively simple method to estimate the dimensions of nanocellulose particles with an aspect ratio greater than 1. Nanocellulose suspensions, both as nanofibers and as nanocrystals, are subjected to dynamic light scattering (DLS) and to field-emission scanning electron microscopy (FE-SEM). The former provides the hydrodynamic diameter, as long as the scatter angle and the consistency are adequate. Assays with different angles and concentrations compel us to recommend forward scattering (12.8°) and concentrations around 0.05-0.10 wt %. Then, FE-SEM with magnifications of ×5000-×20,000 generally suffices to obtain an acceptable approximation for the actual diameter, at least for bundles. Finally, length can be estimated by a simple geometric relationship. Regardless of whether they are collected from FE-SEM or DLS, size distributions are generally skewed to lower diameters. Width distributions from FE-SEM, in particular, are well fitted to log-normal functions. Overall, while this method is not valid for the thinnest fibrils or for single, small nanocrystals, it can be useful in lieu of very high-resolution techniques.

Effective Thallium(I) Removal by Nanocellulose Bioadsorbent Prepared by Nitro-Oxidation of Sorghum Stalks

Thallium(I) (Tl(I)) pollution has become a pressing environmental issue due to its harmful effect on human health and aquatic life. Effective technology to remove Tl(I) ions from drinking water can offer immediate societal benefits especially in the developing countries. In this study, a bio-adsorbent system based on nitro-oxidized nanocellulose (NOCNF) extracted from sorghum stalks was shown to be a highly effective Tl(I) removal medium. The nitro-oxidation process (NOP) is an energy-efficient, zero-waste approach that can extract nanocellulose from any lignocellulosic feedstock, where the effluent can be neutralized directly into a fertilizer without the need for post-treatment. The demonstrated NOCNF adsorbent exhibited high Tl(I) removal efficiency (>90% at concentration < 500 ppm) and high maximum removal capacity (Qm = 1898 mg/g using the Langmuir model). The Tl(I) adsorption mechanism by NOCNF was investigated by thorough characterization of NOCNF-Tl floc samples using spectroscopic (FTIR), diffraction (WAXD), microscopic (SEM, TEM, and AFM) and zeta-potential techniques. The results indicate that adsorption occurs mainly due to electrostatic attraction between cationic Tl(I) ions and anionic carboxylate groups on NOCNF, where the adsorbed Tl(I) sites become nuclei for the growth of thallium oxide nanocrystals at high Tl(I) concentrations. The mineralization process enhances the Tl(I) removal efficiency, and the mechanism is consistent with the isotherm data analysis using the Freundlich model.

Microscopy and Startup Flow Test

The dispersibility of flexible polymer chains present at the emulsion's interface between the dispersed and continuous phase has obvious effects on rheology and dielectric properties of the whole emulsion. Cellulose nanofiber (CNF)-based Pickering emulsions are good systems to research these properties with respect to their microscopic phase structure, dielectric, and rheological properties by using CNF as a water-dispersible Pickering emulsifier, liquid paraffin as an oil phase, and didodecyldimethylammonium bromide (DDAB) as a cationic auxiliary surfactant. The CNF and DDAB contents were systematically varied while the water-to-paraffin oil ratio was kept constant to discern the influence of the Pickering emulsifiers. Polarized optical microscopic images reveal that the droplets tend to shrink at higher CNF content but grow bigger when increasing the DDAB content, which is proved by fluorescence analysis of the CNF dispersibility with varying DDAB content. The dielectric damping exhibits a minimum, whose value decreases with increasing DDAB and CNF content. Increasing the DDAB content promotes the solubilization of CNF in the aqueous phase, which will increase the overall viscosity and yield points. Similarly, a higher CNF content leads to a higher viscosity and yield point, but at high DDAB contents, the viscosity function exhibits an S-shape at intermediate CNF contents. To evaluate the results further, they were compared with CNF dispersions (without oil phase), which showed a surfactant effect slightly on maximum stress but strongly on yield stress τy, indicating that DDAB can promote the formation of a CNF network rather than the viscosity of the whole system. This paper provides information on how a systematical variation of the composition influences morphology and physico-chemical interactions as detected by broadband dielectric spectroscopy and rheological behavior.

Light-Driven Flying Balloons Based on Hybrids of Carbon Nanotubes and Cellulose Nanofibers

We have fabricated nanocarbon-based palm-sized cubic paper balloons that can be levitated by light irradiation. These paper balloons are composed of carbon nanotube (CNT) freestanding films and cellulose nanofiber (CNF) freestanding films. The number of CNT freestanding films (N_CNT) and the number of CNF freestanding films (6-N_CNT) among the six walls of the cube were varied. We investigated the effect of N_CNT on the levitation behaviors under light irradiation. We found that the balloons were levitated when N_CNT was greater than or equal to two. The levitation height was found to be increased by increasing N_CNT.

Citric Acid-Crosslinked Highly Porous Cellulose Nanofiber Foam Prepared by an Environment-Friendly and Simple Process

In this study, cellulose nanofiber (CNF) foams are prepared by an environment-friendly, time-saving, and simple process using bio-based citric acid (CA) as a green crosslinking agent. Scanning electron microscope and Fourier transform infrared spectroscopy examine the foam morphology and confirm the crosslinking. The prepared foam shows a very high porosity (>98%) with a low density (24.02 mg cm-3) with more than 200% improvement in mechanical strength and modulus compared to the neat CNF foam. In addition, the inclusion of CA into CNF improves thermal stability, antioxidant activity, and hydrophobicity. Furthermore, the prepared foam demonstrates a good sound absorption behavior, suitable for environment-friendly and lightweight sound-absorbing foam.