Recent Progress in High-Strength and Robust Regenerated Cellulose Materials

Porous cationic cellulose beads prepared by homogeneous in-situ quaternization and acid induced regeneration for water/moisture absorption

Chemical modification is a reliable and efficient strategy for designing cellulose-based functional materials. Herein, porous quaternized cellulose beads (QCBs) as cationic superabsorbent were fabricated by homogeneous in-situ chemical grafting cellulose molecular chains with glycidyl trimethylammonium chloride (GTAC) in tetraethylammonium hydroxide (TEAOH)/urea aqueous solution followed by acetic acid induced regeneration. The influence of GTAC dosage on the physicochemical-structural properties of cationic QCBs was deeply investigated. Results revealed that cotton liner could well-dissolved in TEAOH/urea aqueous solution, leading to a homogeneous and efficient quaternization medium for cellulose, thereby giving the high DS and positive charge density for quaternized cellulose. NMR results demonstrated the main substitution of GTAC groups at 2-OH and 6-OH positions of the cellulose chains during quaternization reaction. With increasing GTAC dosage, the network skeleton of QCBs gradually transformed from thick fibrils to thin aggregates, as well as enhanced pore volumes and hydrophilicity. Accordingly, QCBs-1.5 with high pore volume (99.70 cm3/g) exhibited excellent absorption capacity and efficiency, absorbing 122.32 g of water and 0.45 g of moisture per gram of the beads in 20 min. This work not only offers a simple strategy for the homogeneous quaternization modification of cellulose, but also provides a porous cellulose-based cationic superabsorbent material.

Insights into the assembly process and properties of regenerated cellulose beads prepared in alkali/urea aqueous solutions

Taking the perspective of cellulose molecular chain assembly via the "bottom-top" route, we delve into the influence of both the cellulose solution and the coagulation bath on the assembly process and structure of regenerated cellulose beads (RCBs). The results show that cellulose molecular weight, mass fraction, and the presence of surfactant have an impact on RCBs. Contrary to traditional views where the structures of material are determined by solvent-nonsolvent exchange rate, ion-cellulose binding capacity also affects RCBs. Overall, the influence of ions follows the Hofmeister sequence. Kosmotropes promote the assembly of cellulose chains and elementary fibers, leading to "salting out" effects, reduced pore size of RCBs, increased crystallinity, and enhanced mechanical properties. In contrast, chaotropes induce "salting in" effects, resulting in opposite outcomes. The average pore size of RCBs coagulated in NaSCN solution was approximately 15-folds larger than those prepared in sodium citrate solution. Anions have a greater impact than cations, and both "salting out" and "salting in" effects strengthen with concentration. Temperature variations primarily affect solvent and nonsolvent exchange speed during cellulose regeneration. These findings provide new insights into regulating RCBs, enabling tailored performance for different applications.

Structuring restricted amorphous molecular chains in the reinforced cellulose film by uniaxial stretching

The construction of the preferred orientation structure by stretching is an efficient strategy to fabricate high-performance cellulose film and it is still an open issue whether crystalline structure or amorphous molecular chain is the key factor in determining the enhanced mechanical performance. Herein, uniaxial stretching with constant width followed by drying in a stretching state was carried out to cellulose hydrogels with physical and chemical double cross-linking networks, achieving high-performance regenerated cellulose films (RCFs) with an impressive tensile strength of 154.5 MPa and an elastic modulus of 5.4 GPa. The hierarchical structure of RCFs during uniaxial stretching and drying was systematically characterized from micro- to nanoscale, including microscopic morphology, crystalline structure as well as relaxation behavior at a molecular level. The two-dimensional correlation spectra of dynamic mechanical analysis and Havriliak-Negami fitting results verified that the enhanced mechanical properties of RCFs were mainly attributed to the stretch-induced tight packing and restricted relaxation of amorphous molecular chains. The new insight concerning the contribution of molecular chains in the amorphous region to the enhancement of mechanical performance for RCFs is expected to provide valuable guidance for designing and fabricating high-performance eco-friendly cellulose-based films.

"Reservoir-law" synergistic reinforcement of electrostatic spun polylactic acid composites with cellulose nanocrystals and 2-hydroxypropyl-β-cyclodextrin for intelligent bioactive food packaging

Cellulose nanocrystals (CNCs) were obtained from the extraction and bleaching of jute cellulose as the enhancer, 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) as the carrier, the flavonoids-anthocyanidins and cinnamaldehyde as the bioactive agent, and finally a novel kind of polylactic acid (PLA)-based composite membrane was derived by electrostatic spun method. With the increasing concentration, HP-β-CDs cooperated with CNCs to regulate or control the release rate of bioactive compounds, which had a synergistic effect on the performance of the PLA matrix. The mechanical strength of PLA-3.2 composite with tannic acid (TA) surface cross-linking was 29.6 % higher than neat PLA, and could also continuously protect cells from oxidative stress and free radicals. In addition, excellent cell biocompatibility was found, and attributed to the interaction between bioactive compounds and cell membrane. In addition, we also found two excellent properties from our experimental results: obvious intelligent color reaction and good antibacterial ability. Finally, PLA-3.2 composites could be degraded by soil and are conducive to plant root growth. Hence, this work could solve many of the current problems of biodegradability and functionality of biopolymers for potential applications in areas such as intelligent bioactive food packaging.

Preparation and characterization of cellulose-chitosan/β-FeOOH composite hydrogels for adsorption and photocatalytic degradation of methyl orange

Biopolymer-based hydrogels have received great attention in wastewater treatment due to their excellent properties, e.g., high adsorption capacity, fast kinetics, reusability and ease of operation. In the present work, cellulose-chitosan/β-FeOOH composite hydrogels were prepared via co-dissolution and regeneration process as well as hydrothermal in situ synthesis of β-FeOOH. Effect of β-FeOOH loading on the properties of the composite hydrogels and the removal efficiency of methyl orange (MO) was investigated. Results showed that β-FeOOH was uniformly loaded onto the hydrogel framework, and the nanoporous structure of composite hydrogels could increase not only the effective contact area between β-FeOOH and the pollutants but also the active sites. Moreover, the increased β-FeOOH loading led to the enhanced MO removal rate under light conditions. When the loading time was extended from 6 h to 9 h, the MO removal rate increased by 21%, which can be mainly due to the photocatalytic degradation. In addition, MO removal rate reached 97.75% within 40 min under optimal conditions and attained 80.81% after five repetitions. The trapping experiment and EPR results indicated that the main active species were hydrogel radicals and holes. Consequently, this work provides an effective preparation approach for cellulose-chitosan/β-FeOOH composite hydrogel with high adsorption and photocatalytic degradation, which would hold great promise for wastewater treatment applications.

Transparent, plasticized cellulose-glycerol bioplastics for food packaging applications

Free-standing films have been obtained by drop-casting cellulose-glycerol mixtures (up to 50 wt% glycerol) dissolved in trifluoroacetic acid and trifluoroacetic anhydride (TFA:TFAA, 2:1, v:v). A comprehensive examination of the optical, structural, mechanical, thermal, hydrodynamic, barrier, migration, greaseproof, and biodegradation characteristics of the films was conducted. The resulting cellulose-glycerol blends exhibited an amorphous molecular structure and a reinforced H-bond network, as evidenced by X-ray diffraction analysis and infrared spectroscopy, respectively. The inclusion of glycerol exerted a plasticizing influence on the mechanical properties of the films, while keeping their transparency. Hydrodynamic and barrier properties were assessed through water uptake and water vapor/oxygen transmission rates, respectively, and obtained values were consistent with those of other cellulose-based materials. Furthermore, overall migration levels were below European regulation limits, as stated by using Tenax® as a dry food simulant. In addition, these bioplastics demonstrated good greaseproof performance, particularly at high glycerol content, and potential as packaging materials for bakery products. Biodegradability assessments were carried out by measuring the biological oxygen demand in seawater and high biodegradation rates induced by glycerol were observed.

Next-generation all-organic composites: A sustainable successor to organic-inorganic hybrid materials

This Review presents an overview of all-organic nanocomposites, a sustainable alternative to organic-inorganic hybrids. All-organic nanocomposites contain nanocellulose, nanochitin, and aramid nanofibers as highly rigid reinforcing fillers. They offer superior mechanical properties and lightweight characteristics suitable for diverse applications. The Review discusses various methods for preparing the organic nanofillers, including top-down and bottom-up approaches. It highlights in situ polymerization as the preferred method for incorporating these nanomaterials into polymer matrices to achieve homogeneous filler dispersion, a crucial factor for realizing desired performance. Furthermore, the Review explores several applications of all-organic nanocomposites in diverse fields including food packaging, performance-advantaged plastics, and electronic materials. Future research directions-developing sustainable production methods, expanding biomedical applications, and enhancing resistance against heat, chemicals, and radiation of all-organic nanocomposites to permit their use in extreme environments-are explored. This Review offers insights into the potential of all-organic nanocomposites to drive sustainable growth while meeting the demand for high-performance materials across various industries.

Advances in regenerated cellulosic aerogel from waste cotton textile for emerging multidimensional applications

Rapid development of society and the improvement of people's living standards have stimulated people's keen interest in fashion clothing. This trend has led to the acceleration of new product innovation and the shortening of the lifespan for cotton fabrics, which has resulting in the accumulation of waste cotton textiles. Although cotton fibers can be degraded naturally, direct disposal not only causes a serious resource waste, but also brings serious environmental problems. Hence, it is significant to explore a cleaner and greener waste textile treatment method in the context of green and sustainable development. To realize the high-value utilization of cellulose II aerogel derived from waste cotton products, great efforts have been made and considerable progress has been achieved in the past few decades. However, few reviews systematically summarize the research progress and future challenges of preparing high-value-added regenerated cellulose aerogels via dissolving cotton and other cellulose wastes. Therefore, this article reviews the regenerated cellulose aerogels obtained through solvent methods, summarizes their structure, preparation strategies and application, aimed to promote the development of the waste textile industry and contributed to the realization of carbon neutrality.

Novel insights on room temperature-induced cellulose dissolution mechanism via ZnCl2 aqueous solution: Migration, penetration, interaction, and dispersion

The unique molecular structure of cellulose makes it challenging to dissolve at room temperature (R.T.), and the dissolution mechanism remains unclear. In this study, we employed ZnCl2 aqueous solution for cellulose dissolution at R.T., proposing a novel four-stage dissolution mechanism. The efficient dissolution of cellulose in ZnCl2 aqueous solution at R.T. involves four indispensable stages: rapid migration of hydrated Zn2+ ions towards cellulose, sufficient penetration between cellulose sheets, strong interaction with cellulose hydroxyl groups, and effective dispersion of separated cellulose chains. The proposed four-stage dissolution mechanism was validated through theoretical calculations and experimental evidence. The hydrated Zn2+ ions in ZnCl2 + 3.5H2O solvent exhibited ideal migration, penetration, interaction, and dispersion abilities, resulting in efficient cellulose dissolution at R.T. Moreover, only slight degradation of cellulose occurred in ZnCl2 + 3.5H2O at R.T. Consequently, the regenerated cellulose materials obtained from ZnCl2 + 3.5H2O (R.T.) exhibited better mechanical properties. Notably, the solvent recovery rate reached about 95 % based on previous usage during five cycles. The solvent is outstanding for its green, low-cost, efficiency, simplicity, R.T. conditions and recyclability. This work contributes to a better understanding of the cellulose dissolution mechanisms within inorganic salt solvents at R.T., thereby guiding future development efforts towards greener and more efficient cellulosic solvents.

Micromorphology reformation of regenerated cellulose nanofibers from corn (Zea Mays) stalk pith in urea solution with high-speed shear induced

Nanocellulose is a kind of renewable natural polymer material with high specific surface area, high crystallinity, and strong mechanical properties. RC nanofibers (RCNFs) have attracted an increasing attention in various applications due to their high aspect ratio and good flexibility. Herein, a novel and facile strategy for RCNFs preparation with high-speed shear induced in urea solution through "bottom-up" approach was proposed in this work. Results indicated that the average diameter and yield of RCNF was approach to 136.67 nm and 53.3 %, respectively. Meanwhile, due to the regular orientation RC chains and arrangement micro-morphology, RCNFs exhibited high crystallinity, strong mechanical properties, stable thermal degradation performance, and excellent UV resistance. In this study, a novel regeneration process with high-speed shear induced was developed to produce RCNFs with excellent properties. This study paved a strategy for future low-energy production of nanofibers and high value-added conversion applications of agricultural waste.

Mechanically Strengthened Aerogels through Multiscale, Multicompositional, and Multidimensional Approaches: A Review

In recent decades, aerogels have attracted tremendous attention in academia and industry as a class of lightweight and porous multifunctional nanomaterial. Despite their wide application range, the low mechanical durability hinders their processing and handling, particularly in applications requiring complex physical structures. "Mechanically strengthened aerogels" have emerged as a potential solution to address this drawback. Since the first report on aerogels in 1931, various modified synthesis processes have been introduced in the last few decades to enhance the aerogel mechanical strength, further advancing their multifunctional scope. This review summarizes the state-of-the-art developments of mechanically strengthened aerogels through multicompositional and multidimensional approaches. Furthermore, new trends and future directions for as prevailed commercialization of aerogels as plastic materials are discussed.

A review of cellulose-based catechol-containing functional materials for advanced applications

With the increment in global energy consumption and severe environmental pollution, it is urgently needed to explore green and sustainable materials. Inspired by nature, catechol groups in mussel adhesion proteins have been successively understood and utilized as novel biomimetic materials. In parallel, cellulose presents a wide class of functional materials rating from macro-scale to nano-scale components. The cross-over among both research fields alters the introduction of impressive materials with potential engineering properties, where catechol-containing materials supply a general stage for the functionalization of cellulose or cellulose derivatives. In this review, the role of catechol groups in the modification of cellulose and cellulose derivatives is discussed. A broad variety of advanced applications of cellulose-based catechol-containing materials, including adhesives, hydrogels, aerogels, membranes, textiles, pulp and papermaking, composites, are presented. Furthermore, some critical remaining challenges and opportunities are studied to mount the way toward the rational purpose and applications of cellulose-based catechol-containing materials.

Applications of Hydrogels in Osteoarthritis Treatment

This review critically evaluates advancements in multifunctional hydrogels, particularly focusing on their applications in osteoarthritis (OA) therapy. As research evolves from traditional natural materials, there is a significant shift towards synthetic and composite hydrogels, known for their superior mechanical properties and enhanced biodegradability. This review spotlights novel applications such as injectable hydrogels, microneedle technology, and responsive hydrogels, which have revolutionized OA treatment through targeted and efficient therapeutic delivery. Moreover, it discusses innovative hydrogel materials, including protein-based and superlubricating hydrogels, for their potential to reduce joint friction and inflammation. The integration of bioactive compounds within hydrogels to augment therapeutic efficacy is also examined. Furthermore, the review anticipates continued technological advancements and a deeper understanding of hydrogel-based OA therapies. It emphasizes the potential of hydrogels to provide tailored, minimally invasive treatments, thus highlighting their critical role in advancing the dynamic field of biomaterial science for OA management.

Anisotropic materials based on carbohydrate polymers: A review of fabrication strategies, properties, and applications

Anisotropic structures exist in almost all living organisms to endow them with superior properties and physiological functionalities. However, conventional artificial materials possess unordered isotropic structures, resulting in limited functions and applications. The development of anisotropic structures on carbohydrates is reported to have an impact on their properties and applications. In this review, various alignment strategies for carbohydrates (i.e., cellulose, chitin and alginate) from bottom-up to top-down strategies are discussed, including the rapidly developed innovative technologies such as shear-induced orientation through extrusion-based 3D/4D printing, magnetic-assisted alignment, and electric-induced alignment. The unique properties and wide applications of anisotropic carbohydrate materials across different fields, from biomedical, biosensors, smart actuators, soft conductive materials, to thermal management are also summarized. Finally, recommendations on the selection of fabrication strategies are given. The major challenge lies in the construction of long-range hierarchical alignment with high orientation degree and precise control over complicated architectures. With the future development of hierarchical alignment strategies, alignment control techniques, and alignment mechanism elucidation, the potential of anisotropic carbohydrate materials for scalable manufacture and clinical applications will be fully realized.

Advancements in Hybrid Cellulose-Based Films: Innovations and Applications in 2D Nano-Delivery Systems

This review paper delves into the realm of hybrid cellulose-based materials and their applications in 2D nano-delivery systems. Cellulose, recognized for its biocompatibility, versatility, and renewability, serves as the core matrix for these nanomaterials. The paper offers a comprehensive overview of the latest advancements in the creation, analysis, and application of these materials, emphasizing their significance in nanotechnology and biomedical domains. It further illuminates the integration of nanomaterials and advanced synthesis techniques that have significantly improved the mechanical, chemical, and biological properties of hybrid cellulose-based materials.

Catalytic activity of Cu2O nanoparticles supported on cellulose beads prepared by emulsion-gelation using cellulose/LiBr solution and vegetable oil

Nanocatalysts tend to aggregate and are difficult to recycle, limiting their practical applications. In this study, an environmentally friendly method was developed to produce cellulose beads for use as supporting materials for Cu-based nanocatalysts. Cellulose beads were synthesized from a water-in-oil emulsion using cellulose dissolved in an LiBr solution as the water phase and vegetable oil as the oil phase. Upon cooling, the gelation of the cellulose solution produced spherical cellulose beads, which were then oxidized to introduce surface carboxyl groups. These beads (diameter: 95-105 μm; specific surface area: 165-225 m2 g-1) have a three-dimensional network of nanofibers (width: 20-30 nm). Furthermore, the Cu2O nanoparticles were loaded onto oxidized cellulose beads before testing their catalytic activity in the reduction of 4-nitrophenol using NaBH4. The apparent reaction rate constant increased with increasing loading of Cu2O nanoparticles and the conversion efficiency was >90 %. The turnover frequency was 376.2 h-1 for the oxidized cellulose beads with the lowest Cu2O loading, indicating a higher catalytic activity compared to those of other Cu-based nanoparticle-loaded materials. In addition to their high catalytic activity, the cellulose beads are reusable and exhibit excellent stability.

Preparation of sustainable oxidized nanocellulose films with high UV shielding effect, high transparency and high strength

UV protection has become crucial as increasing environmental pollution has led to the destruction of the ozone layer, which has a weakened ability to block UV rays. In this paper, we successfully prepared cellulose-based biomass films with high UV shielding effect, high transparency and high tensile strength by graft-modifying oxidized cellulose nanocellulose (TOCN) with folic acid (FA) and borrowing vacuum-assisted filtration. The films had tunable UV shielding properties depending on the amount of FA added. When the FA addition was 20 % (V/V), the film showed 0 % transmittance in the UV region (200-400 nm) and 90.61 % transmittance in the visible region (600 nm), while the tensile strength was up to 150.04 MPa. This study provides a new integrated process for the value-added utilization of nanocellulose and a new route for the production of functional biomass packaging materials. The film is expected to be applied in the field of food packaging with UV shielding.

Efficient fabrication of anisotropic regenerated cellulose films from bamboo via a facile wet extrusion strategy

Bamboo, featuring fast growth rate and high cellulose content, is considered to be one of the most attractive feedstocks for degradable bio-materials as a substitute for plastics. However, those was limited to the fields of bamboo structural materials mainly by physical processes. Herein, we report a facile continuous wet extrusion strategy for scalable manufacturing of anisotropic regenerated cellulose films in alkali/urea aqueous solution for the first time. The bamboo cellulose solution was regenerated in H2SO4/Na2SO4/ZnSO4 aqueous solution to facilitate the construction of dense fibrils networks. Moreover, under the synergistic effect of shear orientations and stretching processes in wet extrusion molding, the cellulose networks promoted further orientated assembly into aligned fibrils. Therefore, these anisotropic cellulose hydrogels exhibited good mechanical properties, and the tensile strength was increased from 1.67 MPa of anisotropic cellulose hydrogel with 1.0 of stretching ration (ACH-1.0) to 2.13 MPa of ACH-1.4 with increasing stretching ratio from 1.0 to 1.4, which was about 1.34 times higher than that of the isotropic hydrogel fabricated by tape-casting. Moreover, ACH-1.4 exhibited commendable thermal stability and air barrier properties. This work demonstrated a simple and continuous bottom-up approach for fabrication of anisotropic bamboo-based cellulose hydrogels and films with excellent mechanical properties.

A triple-crosslinking strategy for high-performance regenerated cellulose fibers derived from waste cotton textiles

Regenerated cellulose fibers has attracted increasing attention for high-grade textile raw materials and industrial textiles, but the low mechanical property caused by differences in regenerated raw materials and production levels limits its commercial application in the product diversity. Herein, we proposed a novel triple-crosslinking strategy by coupling with hydrogen bonds, chemical crosslinking, and internal mineralization from multiple pulsed vapor phase infiltration (MPI) to improve the mechanical performance of regenerated cellulose fibers. A binary solvent composed of ionic liquid (IL) and dimethyl sulfoxide (DMSO) is used to dissolve waste cotton textile and then wet spinning. Dual-crosslinking is firstly achieved by coupling glutaraldehyde (GA) and cellulose reaction. Subsequently, a metal oxide is intentionally infiltrated into inner cellulosic through MPI technology to form a third form of crosslinking, accompanied by the ultra-thin metal oxide nano-layer onto the surface of regenerated cellulose fibers. Results showed that the triple-crosslinking strategy has increased the tensile stress of the fiber by 43.57 % to 287.03 MPa. In all, triple-crosslinking strategy provides a theoretical basis and technical approach for the reinforcement of weak fibers in waste cotton recycling, which is expected to accelerate the development of the waste textile recycling industry and promote of the added-value of regenerated products.

Cellulose Diacetate Aerogels with Low Drying Shrinkage, High-Efficient Thermal Insulation, and Superior Mechanical Strength

The inherent characteristics of cellulose-derived aerogels, such as their natural abundance and environmental friendliness, make them highly interesting. However, its significant shrinkage before and after the supercritical drying procedure and low mechanical strength limit its potential application. Here, we propose a strategy to prepare cellulose diacetate aerogels (CDAAs) with low drying shrinkage, exceptional thermal insulation, and superior mechanical strength. The low drying shrinkage (radial drying shrinkage of 1.4%) of CDAAs is attributed to their relative strong networking skeletons, which are greatly formed by tert-butanol solvent exchange in exerting the interaction of reducing the surface tension force. In this case, CDAAs are eventually endowed with the low bulk density of 0.069 g cm-3 as well. Additionally, as-prepared CDAAs possess an abundant three-dimensional networking structure whose pore size is concentrated in the diameter range of ~50 nm, and the result above is beneficial for improving the thermal insulation performance (thermal conductivity of 0.021 W m-1 K-1 at ambient environmental and pressure conditions). On the other hand, the optimal compressive stresses of CDAAs at 3% and 5% strain are 0.22 and 0.27 MPa respectively, indicating a mechanically well robustness. The above evidence demonstrates indeed the exceptional thermal insulation and superior compressive properties of CDAAs. This work may provide a new solution for developing a kind of high-performance cellulose-derived aerogel in the future.

Glycosidic bond protection of cellulose during solvent dissolution by coordination interaction competition strategy

Exploiting new solvents on efficiently dissolving cellulose is imperative to promote the utilization of cellulosic resources. The process of cellulose dissolution typically necessitates extreme conditions, such as high-temperature treatment, utilization of potent acidic or basic solvents, or the catalytic action of Lewis acids. As a result, the structure of the cellulose is invariably compromised, subsequently obstructing the creation of high-performance materials. In this study, we address this challenge through a simple process, introducing polyethylene glycol (PEG) as glycosidic bond protecting agent, to preserve the polymerization degree of cellulose during its room-temperature dissolution in ZnCl2-phosporic acid eutectic solvent. The PEG units preferentially coordinate with Zn2+ to weaken the hydrolysis of glycosidic bond of cellulose through ether bond competition. The polymerization degree of regenerated cellulose is thus greatly improved, reaching up to seven times that of unprotected cellulose. Overall, this study offers an easy and cost-effective approach to develop cellulose solvents and provides a significant drive towards the fabrication of practical materials through cellulose dissolution.

Aesthetic Cellulose Filaments with Water-Triggered Switchable Internal Stress and Customizable Polarized Iridescence Toward Green Fashion Innovation

Healthy, convenient, and aesthetic hair dyeing and styling are essential to fashion trends and personal-social interactions. Herein, we fabricate green, scalable, and aesthetic regenerated cellulose filaments (ACFs) with customizable iridescent colors, outstanding mechanical properties, and water-triggered moldability for convenient and fashionable artificial hairdressing. The fabrication of ACFs involves cellulose dissolution, cross-linking, wet-spinning, and nanostructured orientation. Notably, the cross-linking strategy endows the ACFs with significantly weakened internal stress, confirmed by monitoring the offset of the C-O-C group in the cellulose molecular chain with Raman imaging, which ensures a tailorable orientation of the nanostructure during wet stretching and tunable iridescent polarization colors. Interestingly, ACFs can be tailored for three-dimensional shaping through a facile water-triggered adjustable internal stress: temporary shaping with low-level internal stress in the wet state and permanent shaping with high-level internal stress in the dry state. The health, convenience, and green aesthetic filaments show great potential in personal wearables.

Adjustable strength and toughness of dual cross-linked nanocellulose films via spherical cellulose as soft-phase

Nanocellulose films possess numerous merits ascribing to their inherent biocompatibility, non-toxic and biodegradability properties. The potential for practical applications would be improved if their mechanical strength and toughness requirements could be met simultaneously. Herein, dual cross-linked nanocellulose (DC) film was fabricated by the treatments of chemical and physical cross-linking, which was mechanically superior to pure nanocellulose (CNF) films. To further increase the toughness of DC films, spherical cellulose (Sph) was incorporated into DC film (DC-Sph film), and analyzed under different humidity conditions (RH) (from 10 % to 90 %). The changes of functional groups of CNF, DC and DC-Sph films were detected by FTIR and XPS spectrum. The epichlorohydrin and Sph content were optimized, followed by the investigation of RH on the toughness of films. The highest tensile strength (146.6 ± 4.6 MPa) was obtained in DC film at 50 % RH, while the DC-Sph film showed the largest toughness (40.3 ± 3.7 kJ/m2) at 70 % RH. Furthermore, the possible toughening mechanism of DC-Sph film was also discussed.

Bottom-Up Magnesium Deposition Induced by Paper-Based Triple-Gradient Scaffolds toward Flexible Magnesium Metal Batteries

The development of advanced magnesium metal batteries (MMBs) has been hindered by longstanding challenges, such as the inability to induce uniform magnesium (Mg) nucleation and the inefficient utilization of Mg foil. This study introduces a novel solution in the form of a flexible, lightweight, paper-based scaffold that incorporates gradient conductivity, magnesiophilicity, and pore size. This design is achieved through an industrially adaptable papermaking process in which the ratio of carboxylated multi-walled carbon nanotubes to softwood cellulose fibers is meticulously adjusted. The triple-gradient structure of the scaffold enables the regulation of Mg ion flux, promoting bottom-up Mg deposition. Owing to its high flexibility, low thickness, and reduced density, the scaffold has potential applications in flexible and wearable electronics. Accordingly, the triple-gradient electrodes exhibit stable operation for over 1200 h at 3 mA cm-2 /3 mAh cm-2 in symmetrical cells, markedly outperforming the non-gradient and metallic Mg alternatives. Notably, this study marks the first successful fabrication of a flexible MMB pouch full cell, achieving an impressive volumetric energy density of 244 Wh L-1 . The simplicity and scalability of the triple-gradient design, which uses readily available materials through an industrially compatible papermaking process, open new doors for the production of flexible, high-energy-density metal batteries.

Dissolution behavior of ionic liquids for different ratios of lignin and cellulose in the preparation of nanocellulose/lignin blends

Lignin is regarded as a potential solution for boosting the strength of cellulose-based products. However, the mechanism of co-solubilization for lignin and cellulose has not been investigated. In this study, the effect of lignin content on the interaction between lignin and nanocellulose during lignin/cellulose co-dissolution was examined. The results revealed that lignin binds to nanocellulose throughout the dissolution process to limit the degradation of cellulose and to prepare nanocellulose/lignin composites. Moreover, the S units in lignin were more likely to interact with cellulose during the dissolution process, whereas the G units were more likely to condense. However, when the lignin content exceeded 30 wt%, the excess lignin created a severe condensation reaction, which led to a decrease in the lignin content bound to cellulose, resulting in an unequal dissolution of cellulose. Thus, a small amount of lignin attached to cellulose during the co-dissolution of lignin and cellulose inhibits cellulose degradation and can be utilized to create nanocellulose/lignin to extend the potential applications of nanocellulosic materials.

An investigation of the environmental implications of bioplastics: Recent advancements on the development of environmentally friendly bioplastics solutions

The production and utilization of plastics may prove beneficial, but the environmental impact suggests the opposite. The single-use plastics (SUP) and conventional plastics are harmful to the environment and need prompt disposal. Bioplastics are increasingly being considered as a viable alternative to conventional plastics due to their potential to alleviate environmental concerns such as greenhouse gas emissions and pollution. However, the previous reviews revealed a lack of consistency in the methodologies used in the Life Cycle Assessments (LCAs), making it difficult to compare the results across studies. The current study provides a systematic review of LCAs that assess the environmental impact of bioplastics. The different mechanical characteristics of bio plastics, like tensile strength, Young's modulus, flexural modulus, and elongation at break are reviewed which suggest that bio plastics are comparatively much better than synthetic plastics. Bioplastics have more efficient mechanical properties compared to synthetic plastics which signifies that bioplastics are more sustainable and reliable than synthetic plastics. The key challenges in bioplastic adoption and production include competition with food production for feedstock, high production costs, uncertainty in end-of-life management, limited biodegradability, lack of standardization, and technical performance limitations. Addressing these challenges requires collaboration among stakeholders to drive innovation, reduce costs, improve end-of-life management, and promote awareness and education. Overall, the study suggests that while bioplastics have the potential to reduce environmental impact, further research is needed to better understand their life cycle and optimize their end-of-life (EoL) management and production to maximize their environmental benefits.

Ionic Conductive Cellulose-Based Hydrogels with Superior Long-Lasting Moisture and Antifreezing Features for Flexible Strain Sensor Applications

Nowadays, wearable devices derived from flexible conductive hydrogels have attracted enormous attention. Nevertheless, the utilization of conductive hydrogels in practical applications under extreme conditions remains a significant challenge. Herein, a series of inorganic salt-ion-enhanced conductive hydrogels (HPE-LiCl) consisting of hydroxyethyl cellulose, hydroxyethyl acrylate, lithium chloride, and ethylene glycol/water binary solvent were fabricated via a facile one-pot method. Apart from outstanding self-adhesion, high stretchability, and remarkable fatigue resistance, the HPE-LiCl hydrogels possessed especially excellent antifreezing and long-lasting moisture performances, which could maintain satisfactory flexibility and electric conductivity over extended periods of time, even in challenging conditions such as extremely low temperatures (as low as -40 °C) and high temperatures (as high as 80 °C). Consequently, the HPE-LiCl-based sensor could timely and accurately monitor various human motion signals even in adverse environments and after long-term storage. Hence, this work presents a facile strategy for the design of long-term reliable hydrogels as smart strain sensors, especially used in extreme environments.

A Sustainable Dual Cross-Linked Cellulose Hydrogel Electrolyte for High-Performance Zinc-Metal Batteries

Aqueous rechargeable Zn-metal batteries (ARZBs) are considered one of the most promising candidates for grid-scale energy storage. However, their widespread commercial application is largely plagued by three major challenges: The uncontrollable Zn dendrites, notorious parasitic side reactions, and sluggish Zn2+ ion transfer. To address these issues, we design a sustainable dual cross-linked cellulose hydrogel electrolyte, which has excellent mechanical strength to inhibit dendrite formation, high Zn2+ ions binding capacity to suppress side reaction, and abundant porous structure to facilitate Zn2+ ions migration. Consequently, the Zn||Zn cell with the hydrogel electrolyte can cycle stably for more than 400 h under a high current density of 10 mA cm-2. Moreover, the hydrogel electrolyte also enables the Zn||polyaniline cell to achieve high-rate and long-term cycling performance (> 2000 cycles at 2000 mA g-1). Remarkably, the hydrogel electrolyte is easily accessible and biodegradable, making the ARZBs attractive in terms of scalability and sustainability.

Green, recyclable, mechanically robust, wet-adhesive and ionically conductive cellulose-based bioplastics enabled by supramolecular covalent hydrophobic eutectic networks

The development of novel cellulose-based bioplastics (CBPs) is highly desirable because CBPs are green, rationally use resources, and lead to a reduction in environmental pollution compared to alternative materials. However, incorporating high transparency, water resistance, mechanical robustness, wet-adhesion, ionic conductivity and recyclability into CBP remains a challenge. In this paper, novel CBPs with supramolecular covalent networks are fabricated by introducing polymerizable hydrophobic deep eutectic solvents (HDES) into ethylcellulose (EC) networks through in situ plasticization followed by a rapid photopolymerization process. The excellent molecular interfacial compatibility enables EC to be loaded with a high content of poly(HDES), while allowing high transparency (more than 90 %) of the prepared CBPs. Multiple intermolecular interactions provide CBPs with mechanical robustness, water resistance, and underwater adhesion, and CBPs can be readily recovered by the solvent in a closed loop. Moreover, CBPs possess inherent ionic conductivities, and using them as green substrates, personalized electroluminescent devices can be successfully constructed. The method proposed in this paper provides a new strategy for the preparation of multifunctional CBPs, which will greatly enrich their applications in self-adhesive materials, green flexible electronics and other package materials.

Water-Driven Sol-Gel Transition in Native Cellulose/1-Ethyl-3-methylimidazolium Acetate Solutions

The addition of water to native cellulose/1-ethyl-3-methylimidazolium acetate solutions catalyzes the formation of gels, where polymer chain-chain intermolecular associations act as cross-links. However, the relationship between water content (Wc), polymer concentration (Cp), and gel strength is still missing. This study provides the fundamentals to design water-induced gels. First, the sol-gel transition occurs exclusively in entangled solutions, while in unentangled ones, intramolecular associations hamper interchain cross-linking, preventing the gel formation. In entangled systems, the addition of water has a dual impact: at low water concentrations, the gel modulus is water-independent and controlled by entanglements. As water increases, more cross-links per chain than entanglements emerge, causing the modulus of the gel to scale as Gp ∼ Cp2Wc3.0±0.2. Immersing the solutions in water yields hydrogels with noncrystalline, aggregate-rich structures. Such water-ionic liquid exchange is examined via Raman, FTIR, and WAXS. Our findings provide avenues for designing biogels with desired rheological properties.

Fiber-Based Noncontact Sensor with Stretchability for Underwater Wearable Sensing and VR Applications

The rapid development of artificial intelligent wearable devices has led to an increasing need for seamless information exchange between humans, machines, and virtual spaces, often relying on touch sensors as the primary interaction medium. Additionally, the demand for underwater detection technologies is on the rise owing to the prevalent wet and submerged environment. Here, a fiber-based capacitive sensor with superior stretchability and hydrophobicity is proposed, designed to cater to noncontact and underwater applications. The sensor is constructed using bacterial cellulose (BC)@BC/carbon nanotubes (CNTs) (BBT) helical fiber as the matrix and methyltrimethoxysilane (MTMS) as the hydrophobic modified agent, forming a hydrophobic silylated BC@BC/CNT (SBBT) helical fiber by the chemical vapor deposition (CVD) technique. These fibers exhibit an impressive contact angle of 132.8°. The SBBT helicalfiber-based capacitive sensor presents capabilities for both noncontact and underwater sensing, which exhibits a significant capacitance change of -0.27 (at a distance of 0.5 cm). We have achieved interactive control between real space and virtual space through intelligent data analysis technology with minimal interference from the presence of water. This work has laid a solid foundation of noncontact sensing with attributes such as degradability, stretchability, and hydrophobicity. Moreover, it offers promising solutions for barrier-free communication in virtual reality (VR) and underwater applications, providing avenues for smart human-machine interfaces for submerged use.

Oriented bacterial cellulose microfibers with tunable mechanical performance fabricated via green reassembly avenue

Bacterial cellulose has garnered remarkable interest from researchers, particularly those working in the biomedical field. In this work, BC microfibers were fabricated via green dissolution (ZnCl2) and regeneration (ethanol). The orientation of cellulose chains was investigated during extrusion and simple post-processing via polarized optical microscopy and small-angle X-ray scattering. The results implied that the mechanical properties of BC microfibers can be tuned by rational pre-stretching. The BC microfibers can be programmable, and be used to suture hard or soft tissues. The as-designed paralleled BC microfibers have good biocompatibility and can regulate the directional growth of cells on their surface. The as-obtained BC microfiber with a high tensile strength of up to ∼115 MPa is suitable for surgical sutures. The tunable BC microfibers may be utilized as an adequate fiber-derived biomedical material product.

Synthesis of organic-solvent-soluble cellulose and preparation of fluorescent polyurethanes for the detection and removal of Hg+ ions

Modifying cellulose to obtain materials with favorable processing properties and functions is highly significant, especially, for the detection and removal of heavy metal ions. In this study, fluorescent cellulose-based polyurethane (PU) films containing naphthalimide fluorophore were synthesized and could use for the convenient detection and removal of Hg+ ions. Firstly, the microcrystalline cellulose was treated with SOCl2 to convert some -OH groups into -Cl. Simultaneously, a naphthalimide derivative (NAN) with -NH- groups was synthesized. Subsequently, a fluorescent cellulose-based probe (Cel-NAN) was prepared by utilizing the substitution reaction between -Cl on cellulose and -NH- on NAN. Finally, two cellulose-based fluorescent PU films (Cel-NAN-PU1 and Cel-NAN-PU2) were successfully synthesized by reacting the unreacted -OH groups on Cel-NAN with PEG-1000 and HDI/IPDI. These as-prepared PU films could serve as portable fluorescence test papers to Hg+ ions in aqueous solutions. Upon contact with Hg+ ions, the fluorescence was quenched, acting as a "turn-off" probe. Simultaneously, these films could serve as adsorbents for the removal of Hg+ ions from aqueous systems. Cel-NAN-PU1 film exhibited a removal efficiency over 80 % and an adsorption capacity of 8.4 mg·cm-2 for Hg+. These cellulose-based fluorescent PU films possess promising potential in the field of mercury pollution control.

An all-natural, bioinspired, biodegradable electrical insulating composite based on lignocellulose and mica tailings

The rapid development of modern electrical engineering puts forward urgent demand for high-performance electrical insulating materials. In this study, inspired by the layered structure of natural nacre, we present a novel biomimetic composite insulating film (referred to as M/C film) that is derived from agricultural waste corncobs and industrial waste mica tailings through a sol-gel-film transformation process. The novel insulating film has excellent tensile strength (94 MPa), high dielectric strength (68 kV mm-1), low dielectric loss, good heat resistance (T0 = 235 °C), and excellent UV shielding properties. Meanwhile, the M/C film presents environmental impacts much lower than those petrochemical-based plastic film as it can be 100 % recycled in a closed-loop recycling process and easily biodegraded in the environment (lignocellulose goes back to the carbon cycle and the mica return to the geological cycle). It is a potential alternative for petrochemical plastics and provides a possible way to utilize agricultural waste and mica tailings.

Zinc Oxide-Loaded Cellulose-Based Carbon Gas Sensor for Selective Detection of Ammonia

Cellulose-based carbon (CBC) is widely known for its porous structure and high specific surface area and is liable to adsorb gas molecules and macromolecular pollutants. However, the application of CBC in gas sensing has been little studied. In this paper, a ZnO/CBC heterojunction was formed by means of simple co-precipitation and high-temperature carbonization. As a new ammonia sensor, the prepared ZnO/CBC sensor can detect ammonia that the previous pure ZnO ammonia sensor cannot at room temperature. It has a great gas sensing response, stability, and selectivity to an ammonia concentration of 200 ppm. This study provides a new idea for the design and synthesis of biomass carbon-metal oxide composites.

The synthesis of multifunctional cellulose graft alternating copolymers of 3,4-dihydrocoumarin and epoxides in DBU/DMSO/CO2 solvent system

Cellulose graft copolymers having well-defined structures could incorporate the characteristics of both the cellulose skeleton and side chains, providing a new method for the preparation functionalised cellulose derivatives. Herein, a series of multifunctional cellulose grafted, alternating 3,4-dihydrocoumarin (DHC) and epoxide (EPO) copolymers (cell-g-P(DHC-alt-EPO)) were prepared in a metal-free DBU/DMSO/CO2 solvent system without adding additional catalyst. Four examples of cell-g-P(DHC-alt-EPO) with tunable thermal and optical properties were synthesized by copolymerization of DHC with styrene oxide (SO), propylene oxide (PO), cyclohexene oxide (CHO) or furfuryl glycidyl ether (FGE) onto cellulose. The nonconjugated cell-g-P(DHC-alt-EPO) showed UV absorption properties with the maximum absorption peak at 282 nm and 295 nm and photoluminescence performance. A clustering-triggered emission mechanism was confirmed and consistent with DFT theoretical calculations. In DMSO solution, the copolymer (DHCSO5) with DP of 11.64 showed ACQ behaviour as the concentration increased. In addition, DHCSO5 had good antioxidant capacity with an instantaneous radical scavenging activity of 2,2-diphenyl-1-picrylhydrazine (DPPH) up to 65 % at a concentration of 40 mg/ ml and increased to 100 % after 30 min. Thus, the multifunctional cell-g-P(DHC-alt-EPO) materials had a variety of potential applications in the fields of fluorescent printing, bio-imaging, UV- shielding and antioxidants.

Recent advances in green technology and Industrial Revolution 4.0 for a sustainable future

This review gives concise information on green technology (GT) and Industrial Revolution 4.0 (IR 4.0). Climate change has begun showing its impacts on the environment, and the change is real. The devastating COVID-19 pandemic has negatively affected lives and the world from the deadly consequences at a social, economic, and environmental level. In order to balance this crisis, there is a need to transition toward green, sustainable forms of living and practices. We need green innovative technologies (GTI) and Internet of Things (IoT) technologies to develop green, durable, biodegradable, and eco-friendly products for a sustainable future. GTI encompasses all innovations that contribute to developing significant products, services, or processes that lower environmental harm, impact, and worsening while augmenting natural resource utilization. Sensors are typically used in IoT environmental monitoring applications to aid ecological safety by nursing air or water quality, atmospheric or soil conditions, and even monitoring species' movements and habitats. The industries and the governments are working together, have come up with solutions-the Green New Deal, carbon pricing, use of bio-based products as biopesticides, in biopharmaceuticals, green building materials, bio-based membrane filters for removing pollutants, bioenergy, biofuels and are essential for the green recovery of world economies. Environmental biotechnology, Green Chemical Engineering, more bio-based materials to separate pollutants, and product engineering of advanced materials and environmental economies are discussed here to pave the way toward the Sustainable Development Goals (SDGs) set by the UN and achieve the much-needed IR 4.0 for a greener-balanced environment and a sustainable future.

Room-temperature phosphorescent materials derived from natural resources

Room-temperature phosphorescent (RTP) materials have enormous potential in many different areas. Additionally, the conversion of natural resources to RTP materials has attracted considerable attention. Owing to their inherent luminescent properties, natural materials can be efficiently converted into sustainable RTP materials. However, to date, only a few reviews have focused on this area of endeavour. Motivated by this lack of coverage, in this Review, we address this shortcoming and introduce the types of natural resource available for the preparation of RTP materials. We mainly focus on the inherent advantages of natural resources for RTP materials, strategies for activating and enhancing the RTP properties of the natural resources as well as the potential applications of these RTP materials. In addition, we discuss future challenges and opportunities in this area of research.

Nanocellulose-based porous materials: Regulation and pathway to commercialization in regenerative medicine

We review the recent progress that have led to the development of porous materials based on cellulose nanostructures found in plants and other resources. In light of the properties that emerge from the chemistry, shape and structural control, we discuss some of the most promising uses of a plant-based material, nanocellulose, in regenerative medicine. Following a brief discussion about the fundamental aspects of self-assembly of nanocellulose precursors, we review the key strategies needed for material synthesis and to adjust the architecture of the materials (using three-dimensional printing, freeze-casted porous materials, and electrospinning) according to their uses in tissue engineering, artificial organs, controlled drug delivery and wound healing systems, among others. For this purpose, we map the structure-property-function relationships of nanocellulose-based porous materials and examine the course of actions that are required to translate innovation from the laboratory to industry. Such efforts require attention to regulatory aspects and market pull. Finally, the key challenges and opportunities in this nascent field are critically reviewed.

MXene-Mediated Cellulose Conductive Hydrogel with Ultrastretchability and Self-Healing Ability

Constructing natural polymers such as cellulose, chitin, and chitosan into hydrogels with excellent stretchability and self-healing properties can greatly expand their applications but remains very challenging. Generally, the polysaccharide-based hydrogels have suffered from the trade-off between stiffness of the polysaccharide and stretchability due to the inherent nature. Thus, polysaccharide-based hydrogels (polysaccharides act as the matrix) with self-healing properties and excellent stretchability are scarcely reported. Here, a solvent-assisted strategy was developed to construct MXene-mediated cellulose conductive hydrogels with excellent stretchability (∼5300%) and self-healability. MXene (an emerging two-dimensional nanomaterial) was introduced as emerging noncovalent cross-linking sites between the solvated cellulose chains in a benzyltrimethylammonium hydroxide aqueous solution. The electrostatic interaction between the cellulose chains and terminal functional groups (O, OH, F) of MXene led to cross-linking of the cellulose chains by MXene to form a hydrogel. Due to the excellent properties of the cellulose-MXene conductive hydrogel, the work not only enabled their strong potential in both fields of electronic skins and energy storage but provided fresh ideas for some other stubborn polymers such as chitin to prepare hydrogels with excellent properties.

Cellulose-Based Conductive Materials for Energy and Sensing Applications

Cellulose-based conductive materials (CCMs) have emerged as a promising class of materials with various applications in energy and sensing. This review provides a comprehensive overview of the synthesis methods and properties of CCMs and their applications in batteries, supercapacitors, chemical sensors, biosensors, and mechanical sensors. Derived from renewable resources, cellulose serves as a scaffold for integrating conductive additives such as carbon nanotubes (CNTs), graphene, metal particles, metal-organic frameworks (MOFs), carbides and nitrides of transition metals (MXene), and conductive polymers. This combination results in materials with excellent electrical conductivity while retaining the eco-friendliness and biocompatibility of cellulose. In the field of energy storage, CCMs show great potential for batteries and supercapacitors due to their high surface area, excellent mechanical strength, tunable chemistry, and high porosity. Their flexibility makes them ideal for wearable and flexible electronics, contributing to advances in portable energy storage and electronic integration into various substrates. In addition, CCMs play a key role in sensing applications. Their biocompatibility allows for the development of implantable biosensors and biodegradable environmental sensors to meet the growing demand for health and environmental monitoring. Looking to the future, this review emphasizes the need for scalable synthetic methods, improved mechanical and thermal properties, and exploration of novel cellulose sources and modifications. Continued innovation in CCMs promises to revolutionize sustainable energy storage and sensing technologies, providing environmentally friendly solutions to pressing global challenges.

Bioinspired Thermochromic Textile Based on Robust Cellulose Aerogel Fiber for Self-Adaptive Thermal Management and Dynamic Labels

Aerogel fiber has emerged recently for incorporation in personal thermal management textiles due to its flexibility, scalability, and ultrahigh porosity, which allows the body to keep warm via thermal isolation without energy consumption. However, the functionalization and intellectualization of cellulose-based aerogel fibers have not yet been fully developed. Herein, we propose a biomimicking design inspired by polar bear and Siamese cat hair that combines porous cellulose aerogel fiber (CAF) with reversible thermochromic microcapsules to mimic biological sensory and adaptive thermoregulation functions. The produced CAF has a controllable pore structure, a large specific surface area (230 m2/g), and excellent mechanical strength (∼15 MPa). Low-temperature darkening microcapsules have been incorporated into the robust CAF to spontaneously adjust color by perceiving the ambient temperature. The functional aerogel fiber fabric achieves high thermal insulation and photothermal modulation simultaneously at temperatures below 18 °C. The temperature of the thermochromic fabric was higher by 6 °C than that of the sample without the microcapsules at a light intensity of 0.2 W/cm2. In addition, the aerogel fibers mixed with two types of thermochromic microcapsules exhibit three color switches with fast response, a color-control precision of 0.2 °C, and good cycling performance. This smart aerogel fibers hold great promise for self-adaptive thermal management, temperature indication, information transfer, and anticounterfeiting in textiles.

Decorated bacteria-cellulose ultrasonic metasurface

Cellulose, as a component of green plants, becomes attractive for fabricating biocompatible flexible functional devices but is plagued by hydrophilic properties, which make it easily break down in water by poor mechanical stability. Here we report a class of SiO2-nanoparticle-decorated bacteria-cellulose meta-skin with superior stability in water, excellent machining property, ultrathin thickness, and active bacteria-repairing capacity. We further develop functional ultrasonic metasurfaces based on meta-skin paper-cutting that can generate intricate patterns of ~10 μm precision. Benefited from the perfect ultrasound insulation of surface Cassie-Baxter states, we utilize meta-skin paper-cutting to design and fabricate ultrathin (~20 μm) and super-light (<20 mg) chip-scale devices, such as nonlocal holographic meta-lens and the 3D imaging meta-lens, realizing complicated acoustic holograms and high-resolution 3D ultrasound imaging in far fields. The decorated bacteria-cellulose ultrasonic metasurface opens the way for exploiting flexible and biologically degradable metamaterial devices with functionality customization and key applications in advanced biomedical engineering technologies.

One-step quaternization and macromolecular reconstruction to prepare micro-/nano-porous cellulose beads from homogeneous solution for low-concentration amoxicillin removal

Designing advanced functional cellulose-based materials by one-step homogeneous preparation technology is a great challenge since cellulose is insoluble in common solvents or difficult to regenerate and shape. Quaternized cellulose beads (QCB) were prepared from a homogeneous solution by one-step cellulose quaternization homogeneous modification and macromolecules' reconstruction technology. Morphological and structural characterizations of QCB were conducted by SEM, FTIR and XPS, etc. The adsorption behavior of QCB was studied using amoxicillin (AMX) as a model molecule. The adsorption of QCB for AMX was multilayer adsorption controlled by both physical adsorption and chemical adsorption. The removal efficiency for 60 mg L^-1 AMX reached 98.60 % through electrostatic interaction, and the adsorption capacity reached 30.23 mg g^-1. AMX adsorption was almost reversible without loss of binding efficiency after three cycles. This facile and green method may offer a promising strategy for the development of functional cellulose materials.

The influence of residual pectin composition and content on nanocellulose films from ramie fibers: Micro-nano structure and physical properties

In this study, cellulose nanofibril (CNF) films from ramie fibers were prepared with different pectin compositions and contents, and the influence of residual pectin on the overall performances of CNF films was evaluated. There was no significant effect of the residual pectin composition on the properties of obtained CNF films. However, when the content of residual pectin was increased from 0.45 % to 9.16 %, the surface area and water absorption of CNF films were increased from 0.2223 to 0.3300 m2/g, and from 93.51 % to 122.42 %, respectively. Pectin covers the CNF surface and act as a physical barrier between the cellulose fibrils; thus the nanocellulose films with high pectin content will have a loose and porous structure, resulting in a high surface area and a high water absorption. Besides, with the residual pectin content decreasing from 9.16 % to 0.45 %, the UVA light transmittance and tensile strength of CNF films were increased from 30.6 % to 59.9 %, and from 37.67 to 100.26 MPa, respectively. After removal of amorphous pectins in CNFs, the low pectin containing CNFs are able to pack more compactly to form a strong and thin film. This paper provides guidance for the preparation of CNF films with different performance requirements.

Cellulose-Based Ionic Conductor: An Emerging Material toward Sustainable Devices

Ionic conductors (ICs) find widespread applications across different fields, such as smart electronic, ionotronic, sensor, biomedical, and energy harvesting/storage devices, and largely determine the function and performance of these devices. In the pursuit of developing ICs required for better performing and sustainable devices, cellulose appears as an attractive and promising building block due to its high abundance, renewability, striking mechanical strength, and other functional features. In this review, we provide a comprehensive summary regarding ICs fabricated from cellulose and cellulose-derived materials in terms of fundamental structural features of cellulose, the materials design and fabrication techniques for engineering, main properties and characterization, and diverse applications. Next, the potential of cellulose-based ICs to relieve the increasing concern about electronic waste within the frame of circularity and environmental sustainability and the future directions to be explored for advancing this field are discussed. Overall, we hope this review can provide a comprehensive summary and unique perspectives on the design and application of advanced cellulose-based ICs and thereby encourage the utilization of cellulosic materials toward sustainable devices.

Personal Microenvironment Management by Smart Textiles with Negative Oxygen Ions Releasing and Radiative Cooling Performance

In recent years, significant strides have been made in the development of smart clothing, which combines traditional apparel with advanced technology. As our climate and environment undergo continuous changes, it has become critically important to invent and refine sophisticated textiles that enhance thermal comfort and human health. In this study, we present a "wearable forest-like textile". This textile is based on helical lignocellulose-tourmaline composite fibers, boasting mechanical strength that outperforms that of cellulose-based and natural macrofibers. This wearable microenvironment does more than generate approximately 18625 ions/cm³ of negative oxygen ions; it also effectively purifies particulate matter. Furthermore, our experiments demonstrate that the negative oxygen ion environment can slow fruit decay by neutralizing free radicals, suggesting promising implications for aging retardation. In addition, this wearable microenvironment reflects solar irradiation and selectively transmits human body thermal radiation, enabling effective radiative cooling of approximately 8.2 °C compared with conventional textiles. This sustainable and efficient wearable microenvironment provides a compelling textile choice that can enhance personal heat management and human health.

A computational study of cellulose regeneration: All-atom molecular dynamics simulations

Processing natural cellulose requires its dissolution and regeneration. It is known that the crystallinity of regenerated cellulose does not match that of native cellulose, and the physical and mechanical properties of regenerated cellulose can vary dependent on the technique applied. In this paper, we performed all-atom molecular dynamics simulations attempting to simulate the regeneration of order in cellulose. Cellulose chains display an affinity to align with one another on the nanosecond scale; single chains quickly form clusters, and clusters then interact to form a larger unit, but the end results still lack that abundance of order. Where aggregation of cellulose chains occurs, there is some resemblance of the 1-10 surfaces found in Cellulose II, with certain indication of 110 surface formation. Concentration and simulation temperature show an increase of aggregation, yet it appears that time is the major factor in reclaiming the order of "crystalline" cellulose.

High-performance dielectric film capacitors based on cellulose/Al2O3 nanosheets/PVDF composites

The design and preparation of novel renewable biomass-based dielectric composites have drawn great attention recently. Here, cellulose was dissolved in NaOH/urea aqueous solution, and Al₂O₃ nanosheets (AONS) synthesized by hydrothermal method were used as fillers. Then the regenerated cellulose (RC)-AONS dielectric composite films were prepared by regeneration, washing and drying. The two-dimensional AONS had a better effect on improving the dielectric constant and breakdown strength of the composites, so that the RC-AONS composite film with 5 wt% AONS content reached an energy density of 6.2 J/cm³ at 420 MV/m. Furthermore, in order to improve the dielectric energy storage properties of cellulose films in high humidity environment, the hydrophobic polyvinylidene fluoride (PVDF) was innovatively introduced to construct RC-AONS-PVDF composite films. The energy storage density of the prepared ternary composite films could reach 8.32 J/cm³ at 400 MV/m, which was 416 % improvement against that of the commercially biaxially oriented polypropylene (2 J/cm³), and could be cycled for >10,000 times under 200 MV/m. Concurrently, the water absorption of the composite film in humidity was effectively reduced. This work broadens the application prospect of biomass-based materials in the field of film dielectric capacitor.

Melt Processible Biodegradable Blends of Polyethylene Glycol Plasticized Cellulose Diacetate with Polylactic Acid and Polybutylene Adipate-Co-Terephthalate

Enhancing the melt processability of cellulose is key to broadening its applications. This is done via derivatization of cellulose, and subsequent plasticization and/or blending with other biopolymers, such as polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT). However, derivatization of cellulose tends to reduce its biodegradability. Moreover, traditional plasticizers are non-biodegradable. In this study, we report the influence of polyethylene glycol (PEG) plasticizer on the melt processibility and biodegradability of cellulose diacetate (CD) and its blends with PLA and PBAT. CD was first plasticized with PEG (PEG-200) at 35 wt%, and then blended with PLA and PBAT using a twin-screw extruder. Blends of the PEG plasticized CD with PLA at 40 wt% and with PBAT at 60 wt% were studied in detail. Dynamic mechanical analysis (DMA) showed that PEG reduced the glass transition of the CD from ca. 220 °C to less than 100 °C, indicating effective plasticization. Scanning electron microscopy revealed that the CD/PEG-PBAT blend had a smoother morphology implying some miscibility. The CD/PEG-PBAT blend at 60 wt% PBAT had an elongation-to-break of 734%, whereas the CD/PEG-PLA blend had a tensile strength of 20.6 MPa, comparable to that of the PEG plasticized CD. After a 108-day incubation period under simulated aerobic composting, the CD/PEG-PBAT blend at 60 wt% PBAT exhibited a biodegradation of 41%, whereas that of the CD/PEG-PLA at 40 wt% PLA was 107%. This study showed that melt processible, biodegradable CD blends can be synthesized through plasticization with PEG and blending with PBAT or PLA.