Mechanical properties of cellulose aerogels and cryogels

Enhanced physicochemical properties and riboflavin delivery ability of soy isolate protein/sugar beet pectin composite freeze-dried gels prepared by double crosslinking strategy

Improving the mechanical strength of protein freeze-dried gels materials has become a research priority in the field of nutrient delivery system development in recent years. In this study, double crosslinking freeze-dried gels were prepared by integrating laccase catalyzed sugar beet pectin (SBP) as a highly active filler molecule into the soybean isolate protein (SPI) thermally induced gel network, followed by freeze-drying. The double crosslinking freeze-dried gels were a porous material and the addition of SBP resulted in the formation of amorphous forms of freeze-dried gels with lower binding energy. The freeze-dried gels with 2.0 % SBP addition had the densest microstructure with the highest density (19.00 mg/cm3) and mechanical strength (180.43 ± 15.27 KPa), and hydrogen bonding, NH, CN, and CO bands were the most important factors to maintain the freeze-dried gels structure. As the concentration of sugar beet pectin increased, the release mechanism of riboflavin underwent a shift from a Fickian to a non-Fickian diffusion mechanism. In addition, the highest bioavailability of riboflavin was found in the freeze-dried gels spiked with 2.0 % SBP. These results will contribute to the development of double crosslinking freeze-dried gels carriers for targeted slow release of hydrophilic bioactive.

Hemp cellulose-based aerogels and cryogels: From waste biomass to sustainable absorbent pads for food preservation

This study presents a circular economy approach utilizing hemp stems and rice straw, typically perceived as low-value agricultural waste, to develop a sustainable alternative to traditional plastic absorbent pads for food packaging. The development of an active material was achieved through the utilization of hemp cellulose and a bioactive extract isolated from rice straw. In addition to reducing plastic pollution, this material demonstrates the potential to enhance food preservation. This research provides evidence of the benefits of repurposing agricultural by-products to create valuable and environmentally-friendly products. Hemp cellulose was extracted, characterized, and processed to develop stable aerogels and cryogels through supercritical CO2 drying and freeze-drying. The water stability and internal structure of the materials were guided via TEMPO-mediated oxidation and high-pressure homogenization. Both materials showed versatile physicochemical and mechanical properties. Nevertheless, with higher water sorption (2.20 mL/g), minimal dimensional changes, and lower shrinkage, cryogels were suitable for meat absorbent pad application. To enhance the cryogels functionality, they were impregnated with a rice straw bioactive extract in two different concentrations. The incorporation of the extract did not affect the structure of the cryogels, improved their mechanical properties and the antioxidant activity remained stable after drying (63.89-78.96 %). Finally, the performance of the developed materials was compared to commercial plastic pads and pristine meat preservation challenge test during 9 days at refrigeration conditions. The incorporation of rice straw extract improved meat color preservation. While moderate extract concentrations (75 mg/g) showed a protective effect against lipid oxidation, higher levels (187.5 mg/g) induced pro-oxidant reactions. This research highlights the potential of hemp cellulose-based cryogels as sustainable and functional packaging materials for meat products.

Enhancement of mechanical properties of nanocellulose xerogels using TEMPO-oxidized fibers

We report xerogels prepared from TEMPO-oxidized cellulose nanofiber (Ox-CNF) that have enhanced yield stresses and Young's Modulus (E) up to 15.4 MPa. The xerogels were highly porous (>95 %) and were measured by density determination, SEM, Brunauer-Emmet-Teller (BET) experiments, and microCT analysis. The xerogels had a density of 0.0182 to 0.0471 g/cm3. We report that the solvent exchange process introduces a distribution of pore sizes and leads to enhanced mechanical properties. Mechanical properties were evaluated by monotonic and cyclical uniaxial compression measurements using a flat punch. These highly porous Ox-CNF xerogels have superior mechanical properties to other CNF xerogels and aerogels.

Effect of Solvents on the Performance and Structure of Polymethylacrylimide Aerogels

Solvent effects play a critical role in solution polymerization, especially in free radical polymerization, where they influence both monomer-solvent interactions and the resulting polymer structure. In this study, polymethacrylimide (PMI) aerogels were synthesized via freeze-drying using dimethylformamide (DMF), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO) as solvents. The effects of monomer reactivity ratios, monomer distribution, and solvent-monomer interactions on the shrinkage, bulk density, pore size, and compressive properties of the aerogels were investigated. Results demonstrated that solvent choice significantly impacted the polymerization process, leading to variations in the structure and properties of the final aerogels. Notably, aerogels synthesized in DMSO, the most polar solvent, exhibited the lowest shrinkage (33.98%), highest density (0.1582 g·cm-3), and highest compressive stress (1695.48 kPa at 70% strain). These findings underscore the importance of solvent selection in controlling the microstructure and enhancing the mechanical performance of PMI aerogels.

An overview of cellulose aerogels and foams for oil sorption: Preparation, modification, and potential of 3D printing

Sorption is one of the most efficient methods to remediate the increasing oil spill incidents, but the currently available absorbents are inadequate to tackle such a global threat. Recently, numerous researchers have attempted to develop sustainable oil sorbents. Cellulose aerogels and foams, a type of lightweight porous material with excellent sorption performance, are one of the most promising candidates. Significant progress has been made in the past decade towards the development of cellulose porous materials as effective oil sorbents, with improvements in their oil sorption capacity, reusability, and enhanced multifunctionality, indicating their potential for oil spill remediation. This article reviews recent reports and provides a comprehensive overview of the preparation and modification strategies for cellulose porous materials, with a specific emphasis on their oil sorption performance and structure control. We also focus on the burgeoning 3D printing technology within this field, summarizing the latest advances with a discussion of the potential for using 3D printing to customize and optimize the structure of cellulose porous materials. Lastly, this review addresses current limitations and outlines future directions for development.

Experimental and Modelling Study of Controlled Release from Dextran-Based Cryogels

In this work, five different dextran-based cryogels for controlled drug release are investigated. Vitamin B12 was used as a model drug for in vitro release tests. Two different drug-loading procedures were adopted, leading to very different drug release curves. Indeed, a fast Fickian release was observed when freeze-dried samples of DEX40PEG360MA and DEX40PEG500MA were infused with the drug after cryogel formation. On the contrary, a slowed highly non-Fickian behavior arises when the drug is loaded before the low-temperature crosslinking step, leading to the cryogel formation. The non-Fickian drug release, observed for all the five different dextran-based cryogels investigated, is actually due to the cryoconcentration phenomenon, modeled with a two-step release process. The proposed transport model accurately predicts experimental release curves characterized by a long lag time, confirming that dextran-based cryogels are suitable for controlled release.

Anisotropic foams derived from textile-based cellulose nanocrystals and xanthan gum

The upcycling of discarded garments can help to mitigate the environmental impact of the textile industry. Here, we fabricated hybrid anisotropic foams having cellulose nanocrystals (CNCs), which were isolated from discarded cotton textiles and had varied surface chemistries as structural components, in combination with xanthan gum (XG) as a physical crosslinker of the dispersion used for foam preparation. All CNCs had crystallinity indices above 85 %, zeta potential values below -40 mV at 1 mM NaCl, and true densities ranging from 1.61 to 1.67 g·cm-3. Quartz crystal microbalance with dissipation (QCM-D) measurements indicated weak interactions between CNC and XG, while rheology measurements showed that highly charged CNCs caused the XG chains to change from an extended to a helicoidal conformation, resulting in changes the in viscoelastic properties of the dispersions. The inclusion of XG significantly enhanced the compression mechanical properties of the freeze-casted foams without compromising their thermal properties, anisotropy, or degree of alignment. CNC-XG foams maintained structural integrity even after exposure to high humidity (91 %) and temperatures (100 °C) and displayed very low radial thermal conductivities. This research provides a viable avenue for upcycling cotton-based clothing waste into high-performance materials.

Recovery of cellulose acetate bioplastic from cigarette butts: realization of a sustainable sorbent for water remediation

Cigarette butts, one of the most common forms of litter in the world, represent a source of chemical and plastic pollution releasing thousands of toxic compounds and microfibers of cellulose acetate (CA). Besides the correct waste management, the recovery of CA from cigarette filters is a way to cushion their negative effects on the environment. Thus far, recycling strategies have been limited to industrial applications, while not many solutions have designed for water remediation. This work describes a strategy to valorize this harmful waste and to reverse its environmental impact, proposing a simple and effective procedure of reclamation of CA and its reuse to prepare a composite sorbent for the treatment of polluted water. The first step entails the washing of filters with hot water (T = 90 °C) and hot ethanol (T = 58-68 °C) to remove the impurities produced during cigarette burning, as verified by means of UV and attenuated total reflection-Fourier-transform infrared (ATR-FTIR) spectroscopy, thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). The second step involves the use of the regenerated CA to prepare porous cylinder-shaped cryogels (15 mm × 10 mm) whose sorption properties are enhanced by the combination with AC (15 % w/w). The synthesis takes advantage of the sol-gel transition of the polymer dispersion (5 % w/V) in a solution acetone/water 5 mM in NH3 (60/40, v/v). After characterization by dynamic mechanical analysis (DMA), TGA, FT-IR, and scanning electron microscopy (SEM), the adsorption capability of the physical cryogel was studied in terms of treated environmental water volume, contact time and concentration of the selected pollutants. The results have shown that the proposed strategy is a low-cost way to recycle CA from cigarette butts and that the designed sorbent is a promising material for water treatment, allowing quick removal times and yields >79.6 %.

Tailoring of Physical Properties in Macroporous Poly(isocyanopeptide) Cryogels

Over the years, synthetic hydrogels have proven remarkably useful as cell culture matrixes to elucidate the role of the extracellular matrix (ECM) on cell behavior. Yet, their lack of interconnected macropores undermines the widespread use of hydrogels in biomedical applications. To overcome this limitation, cryogels, a class of macroporous hydrogels, are rapidly emerging. Here, we introduce a new, highly elastic, and tunable synthetic cryogel, based on poly(isocyanopeptides) (PIC). Introduction of methacrylate groups on PIC facilitated cryopolymerization through free-radical polymerization and afforded cryogels with an interconnected macroporous structure. We investigated which cryogelation parameters can be used to tune the architectural and mechanical properties of the PIC cryogels by systematically altering cryopolymerization temperature, polymer concentration, and polymer molecular weight. We show that for decreasing cryopolymerization temperatures, there is a correlation between cryogel pore size and stiffness. More importantly, we demonstrate that by simply varying the polymer concentration, we can selectively tune the compressive strength of PIC cryogels without affecting their architecture. This unique feature is highly useful for biomedical applications, as it facilitates decoupling of stiffness from other variables such as pore size. As such, PIC cryogels provide an interesting new biomaterial for scientists to unravel the role of the ECM in cellular functions.

Predicting the tensile and compressive modulus of electrospun fiber mat‐reinforced hydrogels using the Halpin–Tsai equations

The reinforcement of mechanically‐weak hydrogels to yield composites with increased stiffness, strength, or toughness is a well‐established approach. In particular, introducing electrospun nanofibers into hydrogels is a common strategy for biomedical applications, as the resulting hierarchical structure mimics biology and allows for control over fiber diameter and alignment and tuning of mechanical properties. However, further study of the link between the constituent materials and the mechanical properties of the composite is uncommon. One potential model to understand the mechanical properties of fiber‐reinforced hydrogels involves the Halpin–Tsai equations, which relate the modulus values of the fibers and hydrogel matrix and the fiber volume fraction, to the modulus of the composite. To assess the application of this model to fiber‐reinforced hydrogels, predicted values were compared with experimental values from mechanical testing of a poly(ethylene glycol) (PEG) matrix reinforced with an electrospun polycaprolactone (PCL) fiber mat. Although the equations described these systems well in tension, providing a facile approach to identify a fiber volume fraction that will achieve a desired modulus, the Halpin–Tsai approach was less successful under compression. This study motivates additional investigation of the role of structural features of hydrogel composites in determining mechanical properties to enable design of materials for specific applications.

Cellulose aerogel beads and monoliths from CO2-based reversible ionic liquid solution

The CO2-based reversible ionic liquid solution of 1,1,3,3-tetramethylguanidine (TMG) and ethylene glycol (EG) in dimethyl sulfoxide (DMSO) after capturing CO2, (2[TMGH]+[O2COCH2CH2OCO2]2-/DMSO (χRILs = 0.1), provides a sustainable and effective platform for cellulose dissolution and homogeneous utilization. Highly porous cellulose aerogel beads and monoliths were successfully prepared via a sol-gel process by extruding cellulose solution into different coagulation baths (NaOH aqueous solution or alcohols) and exposing the cellulose solution in open environment, respectively, and followed by different drying techniques, including supercritical CO2-drying, freeze-drying and air-drying. The effect of the coagulation baths and drying protocols on the multi-scale structure of the as-prepared cellulose aerogel beads and monoliths were studied in detail, and the sol-gel transition mechanism was also studied by the solvatochromic parameters determination. High specific surface area of 252 and 207 m2/g for aerogel beads and monoliths were achieved, respectively. The potential of cellulose aerogels in dye adsorption was demonstrated.

Creating and exploring carboxymethyl cellulose aerogels as drug delivery devices

Carboxymethyl cellulose (CMC) is a well-known cellulose derivative used in biomedical applications due to its biocompatibility and biodegradability. In this work, novel porous CMC materials, aerogels, were prepared and tested as a drug delivery device. CMC aerogels were made from CMC solutions, followed by non-solvent induced phase separation and drying with supercritical CO2. The influence of CMC characteristics and of processing conditions on aerogels' density, specific surface area, morphology and drug release properties were investigated. Freeze-drying of CMC solutions was also used as an alternative process to compare the properties of the as-obtained "cryogels" with those of aerogels. Aerogels were nanostructured materials with bulk density below 0.25 g/cm3 and high specific surface area up to 143 m2/g. Freeze drying yields highly macroporous materials with low specific surface areas (around 5-18 m2/g) and very low density, 0.01 - 0.07g/cm3. Swelling and dissolution of aerogels and cryogels in water and in a simulated wound exudate (SWE) were evaluated. The drug was loaded in aerogels and cryogels, and release kinetics in SWE was investigated. Drug diffusion coefficients were correlated with material solubility, morphology, density, degree of substitution and drying methods, demonstrating tuneability of new materials' properties in view of their use as delivery matrices.

Enzymatic crosslinking of lignin nanoparticles and nanocellulose in cryogels improves adsorption of pharmaceutical pollutants

Pharmaceuticals, designed for treating diseases, ironically endanger humans and aquatic ecosystems as pollutants. Adsorption-based wastewater treatment could address this problem, however, creating efficient adsorbents remains a challenge. Recent efforts have shifted towards sustainable bio-based adsorbents. Here, cryogels from lignin-containing cellulose nanofibrils (LCNF) and lignin nanoparticles (LNPs) were explored as pharmaceuticals adsorbents. An enzyme-based approach using laccase was used for crosslinking instead of fossil-based chemical modification. The impact of laccase treatment on LNPs alone produced surface-crosslinked water-insoluble LNPs with preserved morphology and a hemicellulose-rich, water-soluble LNP fraction. The water-insoluble LNPs displayed a significant increase in adsorption capacity, up to 140 % and 400 % for neutral and cationic drugs, respectively. The crosslinked cryogel prepared by one-pot incubation of LNPs, LCNF and laccase showed significantly higher adsorption capacities for various pharmaceuticals in a multi-component system than pure LCNF or unmodified cryogels. The crosslinking minimized the leaching of LNPs in water, signifying enhanced binding between LNPs and LCNF. In real wastewater, the laccase-modified cryogel displayed 8-44 % removal for cationic pharmaceuticals. Overall, laccase treatment facilitated the production of bio-based adsorbents by improving the deposition of LNPs to LCNF. Finally, this work introduces a sustainable approach for engineering adsorbents, while aligning with global sustainability goals.

Nitric oxide-releasing photocrosslinked chitosan cryogels

The highly porous morphology of chitosan cryogels, with submicrometric-sized pore cell walls, provides a large surface area which leads to fast water absorption and elevated swelling degrees. These characteristics are crucial for the applications of nitric oxide (NO) releasing biomaterials, in which the release of NO is triggered by the hydration of the material. In the present study, we report the development of chitosan cryogels (CS) with a porous structure of interconnected cells, with wall thicknesses in the range of 340-881 nm, capable of releasing NO triggered by the rapid hydration process. This property was obtained using an innovative strategy based on the functionalization of CS with two previously synthesized S-nitrosothiols: S-nitrosothioglycolic acid (TGA(SNO)) and S-nitrosomercaptosuccinic acid (MSA(SNO)). For this purpose, CS was previously methacrylated with glycidyl methacrylate and subsequently submitted to photocrosslinking and freeze-drying processes. The photocrosslinked hydrogels thus obtained were then functionalized with TGA(SNO) and MSA(SNO) in reactions mediated by carbodiimide. After functionalization, the hydrogels were frozen and freeze-dried to obtain porous S-nitrosated chitosan cryogels with high swelling capacities. Through chemiluminescence measurements, we demonstrated that CS-TGA(SNO) and CS-MSA(SNO) cryogels spontaneously release NO upon water absorption at rates of 3.34 × 10-2 nmol mg-1 min-1 and 1.27 × 10-1 nmol mg-1 min-1, respectively, opening new perspectives for the use of CS as a platform for localized NO delivery in biomedical applications.

Multiscale Design for Robust, Thermal Insulating, and Flame Self-Extinguishing Cellulose Foam

Cellulose foams are in high demand in an era of prioritizing environmental consciousness. Yet, transferring the exceptional mechanical properties of cellulose fibers into a cellulose network remains a significant challenge. To address this challenge, an innovative multiscale design is developed for producing cellulose foam with exceptional network integrity. Specifically, this design relies on a combination of physical cross-linking of the microfibrillated cellulose (MFC) networks by cellulose nanofibril (CNF) and aluminum ion (Al3+), as well as self-densification of the cellulose induced by ice-crystal templating, physical cross-linking, solvent exchange, and evaporation. The resultant cellulose foam demonstrates a low density of 40.7 mg cm-3, a high porosity of 97.3%, and a robust network with high compressive modulus of 1211.5 ± 60.6 kPa and energy absorption of 77.8 ± 1.9 kJ m-3. The introduction of CNF network and Al3+ cross-linking into foam also confers excellent wet stability and flame self-extinguish ability. Furthermore, the foam can be easily biodegraded in natural environments , re-entering the ecosystem's carbon cycle. This strategy yields a cellulose foam with a robust network and outstanding environmental durability, opening new possibilities for the advancement of high-performance foam materials.

Retention of Ciprofloxacin and Carbamazepine from Aqueous Solutions Using Chitosan-Based Cryostructured Composites

Water pollution is becoming a great concern at the global level due to highly polluted effluents, which are charged year by year with increasing amounts of organic residues, dyes, pharmaceuticals and heavy metals. For some of these pollutants, the industrial treatment of wastewater is still relevant. Yet, in some cases, such as pharmaceuticals, specific treatment schemes are urgently required. Therefore, the present study describes the synthesis and evaluation of promising cryostructured composite adsorbents based on chitosan containing native minerals and two types of reinforcement materials (functionalized kaolin and synthetic silicate microparticles). The targeted pharmaceuticals refer to the ciprofloxacin (CIP) antibiotic and the carbamazepine (CBZ) drug, for which the current water treatment process seem to be less efficient, making them appear in exceedingly high concentrations, even in tap water. The study reveals first the progress made for improving the mechanical stability and resilience to water disintegration, as a function of pH, of chitosan-based cryostructures. Further on, a retention study shows that both pharmaceuticals are retained with high efficiency (up to 85.94% CIP and 86.38% CBZ) from diluted aqueous solutions.

Mechanical Properties of Cellulose Aerogel Composites with and without Crude Oil Filling

Aerogels are an excellent alternative to traditional oil absorbents and are designed to remove oil or organic solvents from water. Cellulose-based aerogels can be distinguished as polymers that are non-toxic, environmentally friendly, and biodegradable. The compression measurement properties of aerogels are often evaluated using dry samples. Here, oil-soaked, hydrophobized cellulose aerogel samples were examined in comparison to dry samples with and without additional hemp fibers and various levels of starch for crosslinking. The samples were characterized by compression measurement properties and filmed to evaluate the regeneration of the sorbent with repeated use. Overall, the measurements of the mechanical properties for the dry samples showed good reproducibility. The Young's modulus of samples with additional hemp fibers is significantly increased and also shows higher strength than samples without hemp fibers. However, samples without hemp fibers showed slightly better relaxation after compression. Oil acts as a weak plasticizer for all aerogel samples. However, it is important to note that the oil does not cause the samples to decompose in the way unmodified cellulose aerogels do in water. Therefore, using hydrophobized cellulose aerogels as sorbents for oil in a sea or harbor with swell means that they can be collected in their entirety even after use.

Devisable pore structures and tunable thermal management properties of aerogels composed of carbon nanotubes and cellulose nanofibers with various aspect ratios

The anisotropic cellulose nanofiber (CNF)/carbon nanotube (CNT) aerogels hold a great promise in directional applications due to their distinct xylem-like aligned penetrating pore structures. The aspect ratio of CNF plays a crucial role in the pore structures of aerogels, directly dominating the final macroscopic properties of materials. Herein, three types of CNF with different aspect ratios were extracted through the 2,2,6,6-tetrmethylpiperidine-1-oxyl radical (TEMPO) oxidation process by changing the doses of oxidant. The corresponding anisotropic CNF/CNT aerogels were prepared by the unidirectional freeze-drying method and then their pore morphologies and properties were investigated in detail. The resulting aerogel with the shortest aspect ratio of CNF exhibited the densest porous structure, thereby obtaining the highest compressive strength of 110 kPa and elastic modulus of 383 kPa, while that containing the longest CNF possessed the highest thermal conductivity coefficient of 0.17 W m-1 K-1 and the worst thermal insulation. This research explored the relationship between the properties of the CNF/CNT aerogels and devisable pore structures caused by various aspect ratios of CNF, thus providing a new insight into the development of CNF/CNT aerogels with tunable performances.

Hybrid Materials of Bio-Based Aerogels for Sustainable Packaging Solutions

This review explores the field of hybrid materials in the context of bio-based aerogels for the development of sustainable packaging solutions. Increasing global concern over environmental degradation and the growing demand for environmentally friendly alternatives to conventional packaging materials have led to a growing interest in the synthesis and application of bio-based aerogels. These aerogels, which are derived from renewable resources such as biopolymers and biomass, have unique properties such as a lightweight structure, excellent thermal insulation, and biodegradability. The manuscript addresses the innovative integration of bio-based aerogels with various other materials such as nanoparticles, polymers, and additives to improve their mechanical, barrier, and functional properties for packaging applications. It critically analyzes recent advances in hybridization strategies and highlights their impact on the overall performance and sustainability of packaging materials. In addition, the article identifies the key challenges and future prospects associated with the development and commercialization of hybrid bio-based aerogel packaging materials. The synthesis of this knowledge is intended to contribute to ongoing efforts to create environmentally friendly alternatives that address the current problems associated with conventional packaging while promoting a deeper understanding of the potential of hybrid materials for sustainable packaging solutions.

Hybrid and Single-Component Flexible Aerogels for Biomedical Applications: A Review

The inherent disadvantages of traditional non-flexible aerogels, such as high fragility and moisture sensitivity, severely restrict their applications. To address these issues and make the aerogels efficient, especially for advanced medical applications, different techniques have been used to incorporate flexibility in aerogel materials. In recent years, a great boom in flexible aerogels has been observed, which has enabled them to be used in high-tech biomedical applications. The current study comprises a comprehensive review of the preparation techniques of pure polymeric-based hybrid and single-component aerogels and their use in biomedical applications. The biomedical applications of these hybrid aerogels will also be reviewed and discussed, where the flexible polymeric components in the aerogels provide the main contribution. The combination of highly controlled porosity, large internal surfaces, flexibility, and the ability to conform into 3D interconnected structures support versatile properties, which are required for numerous potential medical applications such as tissue engineering; drug delivery reservoir systems; biomedical implants like heart stents, pacemakers, and artificial heart valves; disease diagnosis; and the development of antibacterial materials. The present review also explores the different mechanical, chemical, and physical properties in numerical values, which are most wanted for the fabrication of different materials used in the biomedical fields.

Incorporation of Cellulose-Based Aerogels into Textile Structures

Given their exceptional attributes, aerogels are viewed as a material with immense potential. Being a natural polymer, cellulose offers the advantage of being both replenishable and capable of breaking down naturally. Cellulose-derived aerogels encompass the replenish ability, biocompatible nature, and ability to degrade naturally inherent in cellulose, along with additional benefits like minimal weight, extensive porosity, and expansive specific surface area. Even with increasing appreciation and acceptance, the undiscovered possibilities of aerogels within the textiles sphere continue to be predominantly uninvestigated. In this context, we outline the latest advancements in the study of cellulose aerogels' formulation and their diverse impacts on textile formations. Drawing from the latest studies, we reviewed the materials used for the creation of various kinds of cellulose-focused aerogels and their properties, analytical techniques, and multiple functionalities in relation to textiles. This comprehensive analysis extensively covers the diverse strategies employed to enhance the multifunctionality of cellulose-based aerogels in the textiles industry. Additionally, we focused on the global market size of bio-derivative aerogels, companies in the industry producing goods, and prospects moving forward.

Hybrid Cryogels with Superabsorbent Properties as Promising Materials for Penicillin G Retention

This present study describes the investigation of new promising hybrid cryogels able to retain high amounts of antibiotics, specifically penicillin G, using chitosan or chitosan-biocellulose blends along with a naturally occurring clay, i.e., kaolin. In order to evaluate and optimize the stability of cryogels, three types of chitosan were used in this study, as follows: (i) commercial chitosan; (ii) chitosan prepared in the laboratory from commercial chitin; and (iii) chitosan prepared in the laboratory from shrimp shells. Biocellulose and kaolin, previously functionalized with an organosilane, were also investigated in terms of their potential to improve the stability of cryogels during prolonged submergence under water. The organophilization and incorporation of the clay into the polymer matrix were confirmed by different characterization techniques (such as FTIR, TGA, SEM), while their stability in time underwater was investigated by swelling measurements. As final proof of their superabsorbent behavior, the cryogels were tested for antibiotic adsorption in batch experiments, in which case cryogels based on chitosan extracted from shrimp shells seem to exhibit excellent adsorption properties for penicillin G.

Application of Nanocellulose-Based Aerogels in Bone Tissue Engineering: Current Trends and Outlooks

The complex or compromised bone defects caused by osteomyelitis, malignant tumors, metastatic tumors, skeletal abnormalities, and systemic diseases are difficult to be self-repaired, leading to a non-union fracture. With the increasing demands of bone transplantation, more and more attention has been paid to artificial bone substitutes. As biopolymer-based aerogel materials, nanocellulose aerogels have been widely utilized in bone tissue engineering. More importantly, nanocellulose aerogels not only mimic the structure of the extracellular matrix but could also deliver drugs and bioactive molecules to promote tissue healing and growth. Here, we reviewed the most recent literature about nanocellulose-based aerogels, summarized the preparation, modification, composite fabrication, and applications of nanocellulose-based aerogels in bone tissue engineering, as well as giving special focus to the current limitations and future opportunities of nanocellulose aerogels for bone tissue engineering.

Mechanobiology of cancer cell responsiveness to chemotherapy and immunotherapy: Mechanistic insights and biomaterial platforms

Mechanical forces are central to how cancer treatments such as chemotherapeutics and immunotherapies interact with cells and tissues. At the simplest level, electrostatic forces underlie the binding events that are critical to therapeutic function. However, a growing body of literature points to mechanical factors that also affect whether a drug or an immune cell can reach a target, and to interactions between a cell and its environment affecting therapeutic efficacy. These factors affect cell processes ranging from cytoskeletal and extracellular matrix remodeling to transduction of signals by the nucleus to metastasis of cells. This review presents and critiques the state of the art of our understanding of how mechanobiology impacts drug and immunotherapy resistance and responsiveness, and of the in vitro systems that have been of value in the discovery of these effects.

Lignin nanoparticle-decorated nanocellulose cryogels as adsorbents for pharmaceutical pollutants

Adsorption is a relatively simple wastewater treatment method that has the potential to mitigate the impacts of pharmaceutical pollution. This requires the development of reusable adsorbents that can simultaneously remove pharmaceuticals of varying chemical structure and properties. Here, the adsorption potential of nanostructured wood-based adsorbents towards different pharmaceuticals in a multi-component system was investigated. The adsorbents in the form of macroporous cryogels were prepared by anchoring lignin nanoparticles (LNPs) to the nanocellulose network via electrostatic attraction. The naturally anionic LNPs were anchored to cationic cellulose nanofibrils (cCNF) and the cationic LNPs (cLNPs) were combined with anionic TEMPO-oxidized CNF (TCNF), producing two sets of nanocellulose-based cryogels that also differed in their overall surface charge density. The cryogels, prepared by freeze-drying, showed layered cellulosic sheets randomly decorated with spherical lignin on the surface. They exhibited varying selectivity and efficiency in removing pharmaceuticals with differing aromaticity, polarity and ionic characters. Their adsorption potential was also affected by the type (unmodified or cationic), amount and morphology of the lignin nanomaterials, as well as the pH of the pharmaceutical solution. Overall, the findings revealed that LNPs or cLNPs can act as functionalizing and crosslinking agents to nanocellulose-based cryogels. Despite the decrease in the overall positive surface charge, the addition of LNPs to the cCNF-based cryogels showed enhanced adsorption, not only towards the anionic aromatic pharmaceutical diclofenac but also towards the aromatic cationic metoprolol (MPL) and tramadol (TRA) and neutral aromatic carbamazepine. The addition of cLNPs to TCNF-based cryogels improved the adsorption of MPL and TRA despite the decrease in the net negative surface charge. The improved adsorption was attributed to modes of removal other than electrostatic attraction, and they could be π-π aromatic ring or hydrophobic interactions brought by the addition of LNPs or cLNPs. However, significant improvement was only found if the ratio of LNPs or cLNPs to nanocellulose was 0.6:1 or higher and with spherical lignin nanomaterials. As crosslinking agents, the LNPs or cLNPs affected the rheological behavior of the gels, and increased the firmness and decreased the water holding capacity of the corresponding cryogels. The resistance of the cryogels towards disintegration with exposure to water also improved with crosslinking, which eventually enabled the cryogels, especially the TCNF-based one, to be regenerated and reused for five cycles of adsorption-desorption experiment for the model pharmaceutical MPL. Thus, this study opened new opportunities to utilize LNPs in providing nanocellulose-based adsorbents with additional functional groups, which were otherwise often achieved by rigorous chemical modifications, at the same time, crosslinking the nanocellulose network.

Recent Advances in Biomass-Based Materials for Oil Spill Cleanup

Oil spill on sea surfaces, which mainly produced by the oil leakage accident happened on tankers, offshore platforms, drilling rigs and wells, has bring irreversible damage to marine environments and ecosystems. Among various spill oil handling methods, using sorbents to absorb and recover spill oils is a perspective method because they are cost-effective and enable a high recovery and without secondary pollution to the ecosystem. Currently, sorbents based on biomass materials have aroused extensively attention thanks to their features of inexpensive, abundant, biodegradable, and sustainable. Herein, we comprehensively review the state-of-the-art development of biomass-based sorbents for spill oil cleanup in the recent five years. After briefly introducing the background, the basic theory and material characteristics for the separation of oil from water and the adsorption of oils is also presented. Various modification methods for biomass materials are summarized in section three. Section four discusses the recent progress of biomass as oil sorbents for oil spill cleanup, in which the emphasis is placed on the oil sorption capacity and the separation efficiency. Finally, the challenge and future development directions is outlined.

Divalent metal ion removal from simulated water using sustainable starch aerogels: Effect of crosslinking agent concentration and sorption conditions

This paper evaluates corn starch aerogels, studying different crosslinking agent (trisodium citrate) concentrations (1:1, 1:1.5, and 1:2) and sorption conditions (contact time, adsorbent weight, and initial concentration) regarding the potentially toxic elements (PTEs) [Cd(II) or Zn(II)] adsorption of the aqueous systems. Besides, other properties of aerogels, such as structural properties, specific surface area, and mechanical performance, were evaluated. For adsorption results, better values were observed in adsorption capacity and efficiency for the initial concentration of 100 ppm. In addition, an adsorption time of 12 h and an adsorbent weight of 3.0 g obtained better results due to the possible balance in this time and the high specific surface area available for Cd(II) adsorption. As for the type of adsorbent, the Aero 1:1.5 sample (intermediate crosslinking agent concentration) obtained better results, possibly due to the high porosity, smaller pore sizes, high pore density, and high specific surface area (198 m²·g^-1). In addition, hydroxyl groups in the starch aerogel removed Cd(II) ions with 30 % adsorption efficiency. Lastly, Aero 1:1.5 obtained a high mechanical strength at compression and a satisfactory compressive modulus. In contrast, starch aerogels did not absorb the Zn(II) ion.

Developing dual nano/macroporous starch bioaerogels via emulsion templating and supercritical carbon dioxide drying

In this study, emulsified oil droplets were employed as a temporary porogen to obtain dual nano/macroporous starch aerogels by supercritical carbon dioxide (SC-CO₂) drying. This method took advantage of the solubility of the oil droplet porogens in acetone, and the insolubility of corn starch in this solvent, so this process could be integrated into the typical aerogel processing method. The effect of porogen content and starch concentration on physical and mechanical properties and the internal morphology of the obtained aerogels were studied. While the neat starch aerogel showed a compact structure in macroscale size with interconnected nanopores, the sacrificing oil droplet porogens induced macropores in the emulsion-templated aerogels. Furthermore, the nanoporous structures of starch aerogels were also well-preserved in which the macropores were surrounded by fine and interconnected nanofibrous networks. It resulted in aerogels that exhibited internal morphology in two scales (macropores and nanopores) with a high surface area (156-190 m²/g).

Superinsulating nanocellulose aerogels: Effect of density and nanofiber alignment

Cellulose aerogels are potential alternatives to silica aerogels with advantages in cost, sustainability and mechanical properties. However, the density dependence of thermal conductivity (λ) for cellulose aerogels remains controversial. Cellulose aerogels were produced by gas-phase pH induced gelation of TEMPO-oxidized cellulose nanofibers (CNF) and supercritical drying. Their properties are evaluated by varying the CNF concentration (5-33 mg·cm^-3) and by uniaxial compression (9-115 mg·cm^-3). The aerogels are transparent with specific surface areas of ~400 m²·g^-1, mesopore volumes of ~2 cm³·g^-1 and a power-law dependence of the E-modulus (α ~ 1.53, and the highest reported E of ~1 MPa). The dataset confirms that λ displays a traditional U-shaped density dependence with a minimum of 18 mW·m^-1·K^-1 at 0.065 g·cm^-3. For a given density, λ is ~5 mW·m^-1·K^-1 lower for compressed aerogels due to the alignment of nanofibers, confirmed by small angle X-ray scattering (SAXS).

Shaping 90 wt% NanoMOFs into Robust Multifunctional Aerogels Using Tailored Bio-Based Nanofibrils

Metal-organic frameworks (MOFs) are hybrid porous crystalline networks with tunable chemical and structural properties. However, their excellent potential is limited in practical applications by their hard-to-shape powder form, making it challenging to assemble MOFs into macroscopic composites with mechanical integrity. While a binder matrix enables hybrid materials, such materials have a limited MOF content and thus limited functionality. To overcome this challenge, nanoMOFs are combined with tailored same-charge high-aspect-ratio cellulose nanofibrils (CNFs) to manufacture robust, wet-stable, and multifunctional MOF-based aerogels with 90 wt% nanoMOF loading. The porous aerogel architectures show excellent potential for practical applications such as efficient water purification, CO₂ and CH₄ gas adsorption and separation, and fire-safe insulation. Moreover, a one-step carbonization process enables these aerogels as effective structural energy-storage electrodes. This work exhibits the unique ability of high-aspect-ratio CNFs to bind large amounts of nanoMOFs in structured materials with outstanding mechanical integrity-a quality that is preserved even after carbonization. The demonstrated process is simple and fully discloses the intrinsic potential of the nanoMOFs, resulting in synergetic properties not found in the components alone, thus paving the way for MOFs in macroscopic multifunctional composites.

Biophysical Characterization and Cytocompatibility of Cellulose Cryogels Reinforced with Chitin Nanowhiskers

Polysaccharide-based cryogels are promising materials for producing scaffolds in tissue engineering. In this work, we obtained ultralight (0.046–0.162 g/cm3) and highly porous (88.2–96.7%) cryogels with a complex hierarchical morphology by dissolving cellulose in phosphoric acid, with subsequent regeneration and freeze-drying. The effect of the cellulose dissolution temperature on phosphoric acid and the effect of the freezing time of cellulose hydrogels on the structure and properties of the obtained cryogels were studied. It has been shown that prolonged freezing leads to the formation of denser and stronger cryogels with a network structure. The incorporation of chitin nanowhiskers led to a threefold increase in the strength of the cellulose cryogels. The X-ray diffraction method showed that the regenerated cellulose was mostly amorphous, with a crystallinity of 26.8–28.4% in the structure of cellulose II. Cellulose cryogels with chitin nanowhiskers demonstrated better biocompatibility with mesenchymal stem cells compared to the normal cellulose cryogels.

Crosslinker-Free Hyaluronic Acid Aerogels

Aerogels based on hyaluronic acid (HA) were prepared without any chemical crosslinking by polymer dissolution, network formation via nonsolvent-induced phase separation, and supercritical CO₂ drying. The influence of solution pH, concentration of HA, and type of nonsolvent on network volume shrinkage, aerogel density, morphology, and specific surface area was investigated. A marked dependence of aerogel properties on solution pH was observed: aerogels with the highest specific surface area, 510 m²/g, and the lowest density, 0.057 g/cm³, were obtained when the HA solution was at its isoelectric point (pH 2.5). This work reports the first results ever on neat HA aerogels and constitutes the background for their use as advanced materials for biomedical applications.

Tuning the properties of porous chitosan: Aerogels and cryogels

Highly porous chitosan-based materials were prepared via dissolution, non-solvent induced phase separation and drying using different methods. The goal was to tune the morphology and properties of chitosan porous materials by varying process parameters. Chitosan concentration, concentration of sodium hydroxide in the coagulation bath and aging time were varied. Drying was performed via freeze-drying leading to "cryogels" or via drying with supercritical CO₂ leading to "aerogels". Cryogels were of lower density than aerogels (0.03-0.12 g/cm³vs 0.07-0.26 g/cm³, respectively) and had a lower specific surface area (50-70 vs 200-270 m²/g, respectively). The absorption of simulated wound exudate by chitosan aerogels and cryogels was studied in view of their potential applications as wound dressing. Higher absorption was obtained for cryogels (530-1500%) as compared to aerogels (200-610%).

Cellulose Cryogels as Promising Materials for Biomedical Applications

The availability, biocompatibility, non-toxicity, and ease of chemical modification make cellulose a promising natural polymer for the production of biomedical materials. Cryogelation is a relatively new and straightforward technique for producing porous light and super-macroporous cellulose materials. The production stages include dissolution of cellulose in an appropriate solvent, regeneration (coagulation) from the solution, removal of the excessive solvent, and then freezing. Subsequent freeze-drying preserves the micro- and nanostructures of the material formed during the regeneration and freezing steps. Various factors can affect the structure and properties of cellulose cryogels, including the cellulose origin, the dissolution parameters, the solvent type, and the temperature and rate of freezing, as well as the inclusion of different fillers. Adjustment of these parameters can change the morphology and properties of cellulose cryogels to impart the desired characteristics. This review discusses the structure of cellulose and its properties as a biomaterial, the strategies for cellulose dissolution, and the factors affecting the structure and properties of the formed cryogels. We focus on the advantages of the freeze-drying process, highlighting recent studies on the production and application of cellulose cryogels in biomedicine and the main cryogel quality characteristics. Finally, conclusions and prospects are presented regarding the application of cellulose cryogels in wound healing, in the regeneration of various tissues (e.g., damaged cartilage, bone tissue, and nerves), and in controlled-release drug delivery.

Versatile Route for Multifunctional Aerogels Including Flaxseed Mucilage and Nanocrystals

Preparation of low density monolithic and free-standing organic-inorganic hybrid aerogels of various properties is demonstrated using green chemistry from a biosafe natural source (flaxseed mucilage) and freeze-casting and subsequent freeze drying. Bio-aerogels, luminescent aerogels and magneto-responsive aerogels were obtained by combination of the flaxseed mucilage with different types of nanoparticles. Moreover, the aerogels are investigated as possible drug release system using curcumin as a model. Various characterization techniques like thermogravimetric analysis, nitrogen physisorption, electron microscopy, UV/Vis absorption and emission spectroscopy, bulk density and mechanical measurements as well as in vitro release profile measurements are employed to investigate the obtained materials. The flaxseed-inspired organic-inorganic hybrid aerogels exhibit ultra-low densities of as low as 5.6 mg/cm³ for 0.5% (w/v) mucilage polymer, a specific surface area of 4 to 20 m² /g, high oil absorption capacity (23 g/g) and prominent compressibility. The natural biopolymer technique leads to low cost and biocompatible functional lightweight materials with tunable properties (physicochemical and mechanical) and significant potential for applications as supporting or stimuli responsive materials, carriers, reactors, microwave, and electromagnetic radiation protective (absorbing) material as well as in drug delivery and oil absorption. This article is protected by copyright. All rights reserved.

TEMPO-oxidized nanochitin based hydrogels and inter-structure tunable cryogels prepared by sequential chemical and physical crosslinking

Well dispersibility of 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO)-oxidized nanochitins under alkaline conditions supports the effective chemical crosslinking between nanochitin and epichlorohydrin. The storage modulus of nanochitin hydrogels can be promoted by approximately 10 times as the nanochitin-to-epichlorohydrin mass ratio changes from 4:1 (120 Pa) to 1:4 (1200 Pa). Besides the enhanced mechanical property of hydrogels, the inter-structure of resulting cryogels is found controllable. With increasing epichlorohydrin dosage, the inter-structure of cryogels transforms from a typical fiber-like to honeycomb-like texture. The balance between chemical crosslinking effect and electrostatic repulsion between nanochitins is believed to result this controllable inter-structure. Further immersing into acetic acid solution can greatly enhance the mechanical strength of nanochitin hydrogels due to the introduction of physical crosslinking domains by shielding the electrostatic repulsion, the storage modulus becomes two times higher after immersing in 50% (w/w) acetic acid solution, while the surface area of nanochitin cryogels decreases due to the denser structure.

Synthesis, Characteristics, Oil Adsorption, and Thermal Insulation Performance of Cellulosic Aerogel Derived from Water Hyacinth

Cellulosic aerogel from water hyacinth (WH) was synthesized to address the dual environmental issues of water hyacinth pollution and the production of a green material. Raw WH was treated with sodium hydroxide (NaOH) with microwave assistance and in combination with hydrogen peroxide (H2O2). The results from X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM) showed that lignin and hemicellulose were markedly decreased after treatment, reducing from 24.02% hemicellulose and 5.67% lignin in raw WH to 8.32 and 1.92%, respectively. Cellulose aerogel from the pretreated WH had a high porosity of 98.8% with a density of 0.0162 g·cm-3 and a low thermal conductivity of 0.030 W·m-1·K-1. After modification with methyl trimethoxysilane (MTMS) to produce a highly hydrophobic material, WH aerogel exhibited high stability for oil absorption at a capacity of 43.3, 43.15, 40.40, and 41.88 (g·g-1) with diesel oil (DO), motor oil (MO), and their mixture with water (DO + W and MO + W), respectively. The adsorption remained stable after 10 cycles.

Multifunctional cellulosic aerogels from Posidonia oceanica waste biomass with antioxidant properties for meat preservation

Posidonia oceanica waste biomass has been valorized to develop bioactive multifunctional cellulosic aerogels (HCAG) by simpler and greener protocols. Hydrophobization of cellulosic aerogels was achieved through PLA coating, while bioactivity was imparted by the incorporation of hydrophilic (E2) and hydrophobic extracts (E3) produced from the same biomass. The incorporation of extracts led to denser aerogels, with less porous structures. These aerogels showed outstanding water and oil sorption capacities (1500-1900%), being able to release the adsorbed liquid almost completely after 7 days. Interestingly, all the aerogels showed a positive inhibition effect (23-91%) on the β-carotene bleaching assay. Moreover, the aerogels loaded with extracts, especially when combining E2 and E3, were able to reduce the oxidation of lipids and oxymyoglobin in red meat after 10 days of storage. This evidences the potential of these multifunctional aerogels as bioactive adsorbing pads to preserve the quality of fresh packaged foods.

Recent Progress in High-Strength and Robust Regenerated Cellulose Materials

High-strength petroleum-based materials like plastics have been widely used in various fields, but their nonbiodegradability has caused serious pollution problems. Cellulose, as the most abundant sustainable polymer, has a great chance to act as the ideal substitute for plastics due to its low cost, wide availability, biodegradability, etc. Herein, the recent achievements for developing cellulose "green" solvents and regenerated cellulose materials with high strength via the "bottom-up" route are presented. Cellulose can be regenerated to produce films/membranes, hydrogels/aerogels, filaments/fibers, microspheres/beads, bioplastics, etc., which show potential applications in textiles, biomedicine, energy storage, packaging, etc. Importantly, these cellulose-based materials can be biodegraded in soil and oceans, reducing environmental pollution. The cellulose solvents, dissolving mechanism, and strategies for constructing the regenerated cellulose functional materials with high strength and performances, together with the current achievements and urgent challenges are summarized, and some perspectives are also proposed. The near future will be an exciting era for high-strength biodegradable and renewable materials. The hope is that many environmentally friendly materials with good properties and low cost will be produced for commercial use, which will be beneficial for sustainable development in the world.

Injectable Cryogels Associate with Adipose-Derived Stem Cells for Cardiac Healing After Acute Myocardial Infarctions

Treatment of adipose-derived stem cells (ADSCs) provides support for novel methods of conveying baseline cell protein endothelial cells to promote acute myocardial infarction in gelatin sericin (GS) lamin-coated antioxidant systems (GS@L). The ratio of fixity modules, pores, absorption, and inflammation in the range of ka (65 ka), 149 ±39.8 μm, 92.2%, 42 ± 1.38, and 29 ± 1.9 were observed in the synthesized frames for GS. Herein, ADSC-GS@L was prepared, and the relevant substance for the development of cardiac regenerative applications was stable and physically chemical. In vitro assessments of ADSC-GS@L injectable cryogels established the enhanced survival rates of the cell and improved pro- angiogenic factors as well as pro-inflammatory expression, confirming the favorable outcomes of fractional ejections, fibro-areas, and vessel densities with reduced infraction dimensions. The novel ADSC-injecting cryogel method could be useful for successful heart injury therapies during acute myocardial infarction. Additionally, the method could be useful for successful heart injury therapies during coronary heart disease.

Polysaccharide-based aerogels for thermal insulation and superinsulation: An overview

To reduce energy losses due to the insufficient thermal insulation is one of the current "hot" topics. Various commercial porous materials are used with the best conductivity around 0.03-0.04 W/(m·K). Aerogels are the only known materials with "intrinsic" thermal superinsulating properties, i.e. with thermal conductivity below that of air in ambient conditions (0.025 W/(m·K)). The classical thermal superinsulating aerogels are based on silica and some synthetic polymers, with conductivity 0.014-0.018 W/(m·K). Aerogels based on natural polymers are new materials created at the beginning of the 21st century. Can bio-aerogels possess thermal superinsulating properties? What are the bottlenecks in the development of bio-aerogels as new high-performance thermal insulationing materials? We try to answer these questions by analyzing thermal conductivity of bio-aerogels reported in literature.

Freeze-Thawing-Induced Macroporous Catechol Hydrogels with Shape Recovery and Sponge-like Properties

Catechol-containing hydrogels have been exploited in biomedical fields due to their adhesive and cohesive properties, hemostatic abilities, and biocompatibility. Catechol moieties can be oxidized to o-catecholquinone, a chemically active intermediate, in the presence of oxygen to act as an electrophile to form catechol-catechol or catechol-amine/thiol adducts. To date, catechol cross-linking chemistry to fabricate hydrogels has been mostly performed at room temperature. Herein, we report large increases in catechol cross-linking reaction kinetics by the freeze-thawing process. The formation of ice crystals during freezing steps spatially condenses catechol-containing polymers into nearly frozen (yet unfrozen) regions, resulting in decreases in the polymeric chain distances. This environment allows great increases in catechol cross-linking kinetics, a phenomenon that can also occur during thawing steps. The increased cross-linking rate and spatial condensation in the cryogels provide unique wall and pore structures, which result in elastic, spongelike hydrogels. The moduli of the cryogels prepared by glycol-chitosan-catechol (g-chitosan-c) were improved by 3-6-fold compared to room temperature-cured conventional hydrogels, and the degree of improvement increased depending on the freezing time and the number of freeze-thawing cycles. Unlike typical cell encapsulations before cross-linking, which have often been a source of cytotoxicity, the macroporosity of cryogels allows nontoxic cell seeding with ease. This research offers a new way to utilize catechol cross-linking chemistry by freeze-thawing processes to simultaneously regulate mechanical strength and porous structures in catechol-containing hydrogels.

Shape recoverable, Au nanoparticles loaded nanocellulose foams as a recyclable catalyst for the dynamic and batch discoloration of dyes

An environmental benign in-situ formation and growth of gold nanoparticles (AuNPs) on TEMPO-oxidized cellulose nanofibrils (TOCNF) is reported here. With the active functional groups (aldehyde and carboxyl), TOCNF served as a synchronized reducing and supporting agent for the formation of AuNPs. The entire synthesis process was completed within 30 s under microwave irradiation and regarded as ultra-fast. As obtained AuNPs@TOCNF nanohybrid suspension was freeze-dried to form strong water-activated shape recovery 3D foam. Internal morphology and porosity of the foam were studied by SEM and BET. AuNPs@TOCNF foams exhibited excellent catalytic activity for the discoloration of cationic and anionic dyes in batch and dynamic column processes. The spent foams can be easily recovered and reused up to five cycles with more than 98 % efficiency. During the catalytic processes, no obvious deterioration of the foam structure was observed. Practical applicability of the nanocatalyst was evaluated by treating spiked sea water sample.

Superelastic, Hygroscopic, and Ionic Conducting Cellulose Nanofibril Monoliths by 3D Printing

Compressible and superelastic 3D printed monoliths have shown great promise in various applications including energy storage, soft electronics, and sensors. Although such elastic monoliths have been constructed using some limited materials, most notably graphene, it has not yet been achieved in nature's most abundant material, cellulose, partly due to the strong hydrogen-bonding network within cellulose. Here, we report a 3D-printed cellulose nanofibril monolith that demonstrates superb elasticity (over 91% strain recovery after 500 cycles of compressive test), compressibility (up to 90% compressive strain), and pressure sensitivity (0.337 kPa^-1) at 43% relative humidity. Such a high-performance CNF monolith is achieved through both hierarchical architecture design by 3D printing and freeze-drying and incorporation of hygroscopic salt for water absorption. The facile and efficient design strategy for a highly flexible CNF monolith is expected to expand to materials beyond cellulose and can realize much broader applications in flexible sensors, thermal insulation, and many other fields.