Ionic Crosslinking Research Articles

Biopolymer Meets Nanoclay: Rational Fabrication of Superb Adsorption Beads from Green Precursors for Efficient Capture of Pb(II) and Dyes.

Renewable, green, and safe natural biopolymer-derived materials are highly desired for the purification of pollutants, but significantly improving their performance without the introduction of additional harmful chemicals remains a huge challenge. Based on the concept of "structure optimization design", environment-friendly composite beads (named SA/PASP/RE) with excellent adsorption performance and recyclability were rationally constructed through a green ionic crosslinking route, using the completely green biopolymer sodium alginate (SA), sodium salt of polyaspartic acid (PASP), and the natural nanoclay rectorite (RE) as starting materials. The nano-layered RE was embedded in the polymer matrix to prevent the polymer chain from becoming over-entangled so that more adsorption sites inside the polymer network were exposed, which effectively improved the mass transfer efficiency of the adsorbent and the removal rate of contaminants. The composite beads embedded with 0.6% RE showed high adsorption capacities of 211.78, 197.13, and 195.69 mg/g for Pb(II) and 643.00, 577.80, and 567.10 mg/g for methylene blue (MB) in Yellow River water, Yangtze River water, and tap water, respectively. And the beads embedded with 43% RE could efficiently adsorb Pb(II) and MB with high capacities of 187.78 mg/g and 586.46 mg/g, respectively. This study provides a new route to design and develop a green, cost-effective, and efficient adsorbent for the decontamination of wastewater.

Pervaporation Membranes Based on Polyelectrolyte Complex of Sodium Alginate/Polyethyleneimine Modified with Graphene Oxide for Ethanol Dehydration.

Pervaporation is considered the most promising technology for dehydration of bioalcohols, attracting increasing attention as a renewable energy source. In this regard, the development of stable and effective membranes is required. In this study, highly efficient membranes for the enhanced pervaporation dehydration of ethanol were developed by modification of sodium alginate (SA) with a polyethylenimine (PEI) forming polyelectrolyte complex (PEC) and graphene oxide (GO). The effect of modifications with GO or/and PEI on the structure, physicochemical, and transport characteristics of dense membranes was studied. The formation of a PEC by ionic cross-linking and its interaction with GO led to changes in membrane structure, confirmed by spectroscopic and microscopic methods. The physicochemical properties of membranes were investigated by a thermogravimetric analysis, a differential scanning calorimetry, and measurements of contact angles. The theoretical consideration using computational methods showed favorable hydrogen bonding interactions between GO, PEI, and water, which caused improved membrane performance. To increase permeability, supported membranes without treatment and cross-linked were developed by the deposition of a thin dense layer from the optimal PEC/GO (2.5%) composite onto a developed porous substrate from polyacrylonitrile. The cross-linked supported membrane demonstrated more than two times increased permeation flux, higher selectivity (above 99.7 wt.% water in the permeate) and stability for separating diluted mixtures compared to the dense pristine SA membrane.

Dual crosslinking silk fibroin/pectin-based bioink development and the application on neural stem/progenitor cells spheroid laden 3D bioprinting

The human nervous system is an incredibly intricate physiological network, and neural cells lack the ability to repair and regenerate after a brain injury. 3-dimensional (3D) bioprinting technology offers a promising strategy for constructing biomimetic organ constructs and in vitro brain/disease models. The bioink serves as a pivotal component that emulates the microenvironment of biomimetic construct and exerts a profound influence on cellular behaviors.In this study, a series of mechanically adjustable and dual crosslinking bioinks were developed using photocrosslinkable methacrylated silk fibroin (SilMA) in combination with the ionic crosslinking material, pectin, or pectin methacryloyl (PecMA) with silk fibroin (SF) supplementation. SilMA/pectin exhibited superior properties, with SilMA providing biocompatibility and adjustable mechanical properties, while the addition of pectin enhanced printability. The porous structure supported neural cell growth, and 15 % SilMA/0.5 % pectin bioinks displayed excellent printability and shape fidelity. Neural stem/progenitor cells (NSPCs)-loaded bioinks were used to construct a 3D brain model, demonstrating sustained vitality and high neuronal differentiation without the need for growth factors. The SilMA/pectin bioinks demonstrated adjustable mechanical properties, favorable biocompatibility, and an environment highly conducive to neural induction, offering an alternative approach for neural tissue engineering applications or in vitro brain models.

Ionic Cross-Linked MOF-Polymer Mixed-Matrix Membranes for Suppressing Interfacial Defects and Plasticization Behavior.

To address the plasticization phenomenon and MOF-polymer interfacial defects, we report the synthesis of ionic cross-linked MOF MMMs from a dual brominated polymer and MOF components by using N,N'-dimethylpiperazine as the cross-linker. We synthesized brominated MIL-101(Cr) nanoparticles by using mixed linkers and prepared brominated polyimide (6FDA-DAM-Br) to form ionic cross-linked MMMs. The gas permeation properties of the polyimide, ionic cross-linked MOF-polymer MMMs, and non-cross-linked MOF-polymer MMMs with various MOF weight loadings were investigated systematically to effectively understand the effects of MOF weight loading and ionic cross-linking. The ionic cross-linked 40 wt % MOF-polymer MMM exhibited significantly enhanced gas permeability with an H2 permeability of 1640 Barrer and CO2 permeability of 1981 Barrer and slightly decreased H2/CH4, H2/N2, CO2/CH4 and CO2/N2 selectivities of 16.9, 15.4, 20.5, and 18.6, respectively. The H2 and CO2 permeabilities are approximately 2-3 fold higher than those of the pure polyimide (6FDA-DAM) membrane. Moreover, the ionic cross-linked 40 wt % MOF-polymer MMM exhibited significantly increased resistance to plasticization. This is because the brominated MOF incorporation boosted molecular transport and polymer chain rigidity, and ionic cross-linking further reduced the number of interfacial defects and polymer chain mobility.

Metal-organic frameworks-based moisture responsive essential oil hydrogel beads for fresh-cut pineapple preservation

The preservation of fresh-cut fruits and vegetables has attracted attention to the shelf-life reduction caused by high humidity. Herein, alginate/copper ions cross-linking, in-situ growth and self-assembly techniques of metal-organic frameworks (MOFs) were utilized to prepare a moisture responsive hydrogel bead (HKUST-1@ALG). As the multistage porous structure formation, tea tree essential oil (TTO) load capacity in hydrogel bead (TTO-HKUST-1@ALG) was increased from 6.1% to 21.6%. TTO-HKUST-1@ALG had excellent moisture response performance, and the release rates of TTO increased from 33.89% to 70.98% with moisture increasing from 45% to 95%. Besides, TTO-HKUST-1@ALG exhibited excellent antimicrobial, antioxidant capacity, and biocompatibility. During storage, TTO-HKUST-1@ALG effectively improved the cell membrane integrity by maintaining the balance of reactive oxygen species metabolism. The degradation of cell wall structure and tissue softening were delayed by inhibiting the cell wall-degrading enzymes activity. Briefly, TTO-HKUST-1@ALG improved the storage quality and extended shelf-life of fresh-cut pineapple, which was a promising preservative.

Ionic-physical–chemical triple cross-linked all-biomass-based aerogel for thermal insulation applications

Aerogels, as a unique porous material, are expected to be used as insulation materials to solve the global environmental and energy crisis. Using chitosan, citric acid, pectin and phytic acid as raw materials, an all-biomass-based aerogel with high modulus was prepared by the triple strategy of ionic, physical and chemical cross-linking through directional freezing technique. Based on this three-dimensional network, the aerogel exhibited excellent compressive modulus (24.89 ± 1.76 MPa) over a wide temperature range and thermal insulation properties. In the presence of chitosan, citric acid and phytic acid, the aerogel obtained excellent fire safety (LOI value up to 31.2%) and antibacterial properties (antibacterial activity against Staphylococcus aureus and Escherichia coli reached 81.98% and 67.43%). In addition, the modified aerogel exhibited excellent hydrophobicity (hydrophobic angle of 146°) and oil–water separation properties. More importantly, the aerogel exhibited a biodegradation rate of up to 40.31% for 35 days due to its all-biomass nature. This work provides a green and sustainable strategy for the production of highly environmentally friendly thermal insulation materials with high strength, flame retardant, antibacterial and hydrophobic properties.

Synthesis of hydrogel of polyvinylimide modified carboxylated nanocellulose combined with acidified montmorillonite for pH-controlled release of thiamethoxam

Controlled release of pesticides in response to environmental stimuli using hydrogels as carriers is a feasible approach to improve the effective utilization rates of pesticides. In this regard, modified carboxylated cellulose nanocrystal (CCNC)--based hydrogels with appropriate biocompatibilities and high specific surface areas have broad prospects. Accordingly, in this study, a pH-responsive hydrogel loaded with the pesticide thiamethoxam (TXM) (PEI-CCNC@A-MMT/TXM) was constructed by synergistically introducing CCNC modified with polyethyleneimine (PEI) into cost-effective acidified montmorillonite (A-MMT) via electrostatic self-assembly followed by combination with sodium alginate (SA) by emulsion–gel method via ionic crosslinking. PEI-CCNC@A-MMT efficiently improved the mechanical properties of the SA hydrogel and ensured the stability and TXM loading efficiency of this hydrogel; however, the hydrogel stress increased from 9.48 to 41.44 kPa under 20 % compressive strain when the mass ratio of A-MMT to PEI-modified CCNC (PEI-CCNC) was increased from 0 to 0.8. PEI-CCNC@A-MMT/TXM exhibited significant controlled-release characteristics with the change in pH; specifically, with an increase in pH from 5.0 to 9.0, the cumulative release ratio of TXM increased from 53.62 to 94.86 wt % within 48 h of the addition of PEI-CCNC@A-MMT/TXM to the phosphate buffered saline solution. Fitting the six models to the release curves proved that swelling, dissolution, and diffusion acted together during TXM release, and release mechanisms for TXM under different pH conditions were proposed. The release behaviors of PEI-CCNC@A-MMT/TXM in soil indicated that this hydrogel effectively prolonged the release of TXM, and only 91.53 wt % TXM was released within 240 h after the hydrogel entered the soil. The bacterial activity revealed that the hydrogel did not destroy the microbial environment of the soil and demonstrated high biocompatibility. This study provides a promising strategy for regulating the pesticide release behavior, improving pesticide utilization, and reducing environmental pollution of pesticides via introducing low-cost A-MMT and green CCNC into the SA hydrogel and applying this hydrogel as a pesticide carrier.

Effects of Sodium Alginate and Calcium Chloride on Fungal Growth and Viability in Biomass-Fungi Composite Materials Used for 3D Printing.

To combat climate change, one approach is to manufacture products from biomass-fungi composite materials instead of petroleum-based plastics. These products can be used in packaging, furniture, and construction industries. A 3D printing-based manufacturing method was developed for these biomass-fungi composite materials, eliminating the need for molds, and enabling customized product design. However, previous studies on the 3D printing-based method showed significant shrinkage of printed samples. In this paper, an approach is proposed to reduce the shrinkage by incorporating ionic crosslinking into biomass-fungi composite materials. This paper reports two sets of experiments regarding the effects of sodium alginate (SA) and calcium chloride (CaCl2) on fungal growth and fungal viability. The first set of experiments was conducted using Petri dishes with fungi isolated from colonized biomass-fungi material and different concentrations of SA and CaCl2. Fungal growth was measured by the circumference of fungal colonies. The results showed that concentrations of SA and CaCl2 had significant effects on fungal growth and no fungal growth was observed on Petri dishes with 15% CaCl2. Some of these Petri dishes were also observed under confocal microscopy. The results confirmed the differences obtained by measuring the circumference of fungal colonies. The second set of experiments was conducted using Petri dishes with biomass-fungi mixtures that were treated with different concentrations of SA and exposure times in a CaCl2 (crosslinking) solution. Fungal viability was measured by counting colony-forming units. The results showed that the addition of the SA solution and exposure times in the crosslinking solution had statistically significant effects on fungal viability. The 2SA solution was prepared by dissolving 2 g of SA in 100 mL of water, the 5SA solution was prepared by dissolving 5 g of SA in 100 mL of water, and the crosslinking solution was prepared by dissolving 5 g of CaCl2 in 100 mL of water. The results also showed that fungal viability was not too low in biomass-fungi mixtures that included 2SA solution and were exposed to the crosslinking solution for 1 min.

Constructing gellan gum/konjac glucomannan/wheat fiber composite hydrogel to simulate edible cartilage by ionic cross-link and moisture regulation

The utilization of non-animal-derived materials to imitate cartilage is critical for the advancement of plant-based simulated meat. In this study, gellan gum (GG), konjac glucomannan (KGM), and wheat fiber (WF) were used to construct hydrogel, and the mechanical strength, water properties, and microstructure were regulated by constructing Ca2+ cross-links and moisture control. The hardness, chewiness, resilience, shear force, and shear energy of the Ca2+ cross-linked samples were significantly improved. Extrusion dehydration further changes the related mechanical properties of the hydrogel and results in a tighter microstructure. The findings suggest that the establishment of Ca2+ cross-links and water regulation are efficacious techniques for modifying the texture of the GG/KGM/WF composite hydrogel. Correlation analysis and sensory evaluation showed that the test indexes and sensory scores of the samples with Ca2+ crosslinking and 80 % moisture content were similar to chicken breast cartilage, and the samples with Ca2+ crosslinking and 70 % moisture content were similar to pig crescent bone. This study presents a framework for designing edible cartilage simulators using polysaccharide hydrogels, with implications for enhancing the resemblance of plant-based meat products to real meat and expanding the range of vegetarian offerings available.

Chitosan oligosaccharide-functionalized nano-prodrug for cascade chemotherapy through oxidative stress amplification

Redox nanoparticles have been extensively developed for chemotherapy. However, the intracellular oxidative stress induced by constant aberrant glutathione (GSH), reactive oxygen species (ROS) and gamma-glutamyl transpeptidase (GGT) homeostasis remains the primary cause of evading tumor apoptosis. Herein, an oxidative stress-amplification strategy was designed using a pH-GSH-H2O2-GGT sensitive nano-prodrug for precise synergistic chemotherapy. The disulfide bond- conjugated doxorubicin prodrug (DOX-ss) was constructed as a GSH-scavenger. Then, phenylboronic acid (PBA), DOX-ss and poly (γ-glutamic acid) (γ-PGA) were successively conjugated using chitosan oligosaccharide (COS) to obtain the nano-prodrug PBA-COS-ss-DOX/γ-PGA. The PBA-COS-ss-DOX/γ-PGA prodrug could tightly attach to the polymer chain segment by atom transfer radical polymerization. Simultaneously, the drug interacted relatively weakly with the polymer by encapsulating ionic crosslinkers in DOX@PBA-COS/γ-PGA. The disulfide bond of the DOX-ss prodrug as a GSH-scavenger could be activated using overexpressed GSH to release DOX. Particularly, PBA-COS-ss-DOX/γ-PGA could prevent premature drug leakage and facilitate DOX delivery by GGT-targeting and intracellular H2O2-cleavable linker in human hepatocellular carcinoma (HepG2) cells. Concurrently, the nano-prodrug induced strong oxidative stress and tumor cell apoptosis. Collectively, the pH-GSH-H2O2-GGT responsive nano-prodrug shows potential for synergistic tumor therapy.

On the performance of Sargassum-derived calcium alginate ion exchange resins for Pb2+ adsorption: batch and packed bed applications

Driven by climate change and human activity, Sargassum blooming rates have intensified, producing copious amount of the invasive, pelagic seaweed across the Caribbean and Latin America. Battery recycling and lead-smelter wastes have heavily polluted the environment and resulted in acute lead poisoning in children through widespread heavy metal contamination particular in East Trinidad. Our study details a comprehensive investigation into the use of Sargassum (S. natans), as a potential resource-circular feedstock for the synthesis of calcium alginate beads utilized in heavy metal adsorption, both in batch and column experiments. Here, ionic cross-linking of extracted sodium alginate with calcium chloride was utilized to create functional ion-exchange beads. Given the low quality of alginates extracted from Sargassum which produce poor morphological beads, composite beads in conjunction with graphene oxide and acrylamide were used to improve fabrication. Stand-alone calcium alginate beads exhibited superior Pb2+ adsorption, with a capacity of 213 mg g−1 at 20 °C and pH 3.5, surpassing composite and commercial resins. Additives like acrylamide and graphene oxide in composite alginate resins led to a 21–40% decrease in Pb2+ adsorption due to reduced active sites. Column operations confirmed Alginate systems’ practicality, with 20–24% longer operating times, 15 times lower adsorbent mass on scale-up and 206% smaller column diameters compared to commercial counterparts. Ultimately, this study advocates for Sargassum-based Alginate ion-exchange beads as a bio-based alternative in Trinidad and developing nations for dealing with heavy metal ion waste, offering superior heavy metal adsorption performance and supporting resource circularity.Graphical

Comparative Analysis of Crosslinking Methods and Their Impact on the Physicochemical Properties of SA/PVA Hydrogels.

Hydrogels, versatile materials used in various applications such as medicine, possess properties crucial for their specific applications, significantly influenced by their preparation methods. This study synthesized 18 different types of hydrogels using sodium alginate (SA) and two molecular weights of polyvinyl alcohol (PVA). Crosslinking agents such as aqueous solutions of calcium (Ca2+) and copper (Cu2+) ions and solutions of these ions in boric acid were utilized. The hydrogels were subjected to compression strength tests and drying kinetics analysis. Additionally, six hydrogel variants containing larger PVA particles underwent Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) post-drying. Some samples were lyophilized, and their surface morphology was examined using scanning electron microscopy (SEM). The results indicate that the choice of crosslinking method significantly impacts the physicochemical properties of the hydrogels. Crosslinking in solutions with higher concentrations of crosslinking ions enhanced mechanical properties and thermal stability. Conversely, using copper ions instead of calcium resulted in slower drying kinetics and reduced thermal stability. Notably, employing boric acid as a crosslinking agent for hydrogels containing heavier PVA molecules led to considerable improvements in mechanical properties and thermal stability.

Radiation synthesis of covalently/non-covalently coupled all ionic liquid-based Ionogels with rapid self-healing, environmental tolerance for multifunctional ionic skin

As novel artificial ion-conducting materials with skin-like functionalities, Ionic skins (I-Skins) have attracted wide attention in the field of smart wearables. Nonetheless, the crucial hurdle of maintaining their properties in extreme conditions, such as cold, hot or long-term storage, persists. Herein, ionic liquid monomers, ionic liquid solvents, and ionic liquid cross-linkers are employed to facilitate covalently/non-covalently coupled all ionic liquid-based Ionogel for multimodal artificial I-skin through electron beam irradiation under mild conditions at the first time. Profiting from the covalently/non-covalently interactions in the Ionogel, the Ionogel has tunable mechanical properties, excellent environmental adaptability (−60 to 150 °C), long-term stability (90 days), fast response time (0.1 s), rapid self-healing ability (120 s recovery to 90 % of original), and favorable adhesion properties. Moreover, Ionogel sensors possess the remarkable capability to accurately perceive external stimuli, including strain, temperature, and humidity, similar to human skin, which can effectively monitor human movement behavior, as well as fluctuations in ambient temperature and humidity. It is expected that this all ionic liquid-based Ionogel sensor can fill the gap of I-Skin in extreme conditions and realize multifunctional flexible sensing, thus expanding more application scenarios.

Preparation of pH-sensitive carboxymethyl chitosan nanoparticles loaded with ginsenoside Rb1 and evaluation of drug release in vitro

Oral absorption of ginsenoside Rb1 (Rb1) is often hindered by the gastrointestinal tract. Carboxymethyl chitosan deoxycholic acid loaded with ginsenoside Rb1 nanoparticles (CMDA@Rb1-NPs), were prepared as a delivery system using a self-assembly technique with amphipathic deoxycholic acid grafted carboxymethyl chitosan as the carrier, which improved the stability and embedding rate of Rb1. In addition, the CMDA@Rb1-NPs was encapsulated with sodium alginate by ion crosslinking method with additional layer (CMDAlg@Rb1-NPs). Scanning electron microscopy showed that the nanoparticles were spherical, evenly distributed, smooth and without obvious adhesion. By evaluating drug loading, entrapment efficiency, the encapsulation efficiency of Rb1 increased from 60.07 % to 72.14 % after grafting deoxycholic acid improvement and optimization. In vitro release results showed that the cumulative release of Rb1 by CMDAlg-NPs showed a pH dependent effect, which was <10 % in simulated gastric juice with pH 1.2, completely released with pH 7.4 for about 48 h. In addition, Rb1 and CMDAlg@Rb1-NPs had inhibitory effects on A549 cells, and the inhibitory effect of CMDAlg@Rb1-NPs was better. Therefore, all results indicated that CMDA/Alg@Rb1 nanoparticles might be a novel drug delivery system to improve the stability and embedding rate of Rb1, and has the potential to be applied in oral pharmaceutical preparations.

A Gelatin/Alginate Double Network Hydrogel Nerve Guidance Conduit Fabricated by a Chemical-Free Gamma Radiation for Peripheral Nerve Regeneration.

Nerve guidance conduits (NGCs) are widely developed using various materials for the functional repair of injured or diseased peripheral nerves. Especially, hydrogels are considered highly suitable for the fabrication of NGCs due to their beneficial tissue-mimicking characteristics (e.g., high water content, softness, and porosity). However, the practical applications of hydrogel-based NGCs are hindered due to their poor mechanical properties and complicated fabrication processes. To bridge this gap, a novel double-network (DN) hydrogel using alginate and gelatin by a two-step crosslinking process involving chemical-free gamma irradiation and ionic crosslinking, is developed. DN hydrogels (1% alginate and 15% gelatin), crosslinked with 30 kGy gamma irradiation and barium ions, exhibit substantially improved mechanical properties, including tensile strength, elastic modulus, and fracture stain, compared to single network (SN) gelatin hydrogels. Additionally, the DN hydrogel NGC exhibits excellent kink resistance, mechanical stability to successive compression, suture retention, and enzymatic degradability. In vivo studies with a sciatic defect rat model indicate substantially improved nerve function recovery with the DN hydrogel NGC compared to SN gelatin and commercial silicone NGCs, as confirm footprint analysis, electromyography, and muscle weight measurement. Histological examination reveals that, in the DN NGC group, the expression of Schwann cell and neuronal markers, myelin sheath, and exon diameter are superior to the other controls. Furthermore, the DN NGC group demonstrates increased muscle fiber formation and reduced fibrotic scarring. These findings suggest that the mechanically robust, degradable, and biocompatible DN hydrogel NGC can serve as a novel platform for peripheral nerve regeneration and other biomedical applications, such as implantable tissue constructs.

Formulation and evaluation of hydrocortisone micro beads

The current study aimed to develop hydrocortisone mucoadhesive microbeads to prolong the drug's action in the gastrointestinal system, targeting Crohn's disease treatment. Hydrocortisone, known for its anti-inflammatory and anti-rheumatic effects, was utilized in bead form to enhance therapeutic efficacy, extend residence time, and reduce dosage frequency. Using sodium alginate, HPMC, and Eudragit L-100 as adhesive polymers, and calcium chloride and aluminium chloride as cross-linking agents, the study crafted microbeads with an entrapment efficiency between 57.23% and 91.69%. Evaluations focused on in vitro drug release, particle size, surface characteristics, entrapment efficiency, and the role of cross-linking ions. Of the formulations, HCS-8 (with sodium alginate and Eudragit L-100 using aluminium chloride as the gelling solution) and HCS-2 showed optimal drug release profiles. Notably, HCS-8 achieved a 12-hour drug release delay, attributed to aluminium chloride's cross-linking action. Drug release kinetics revealed a zero-order linearity (R2=0.99), suggesting super case 2 transport as the primary release mechanism.

Ambient-condition curable high internal phase emulsion as a 3D-printable and scalable porous template

High internal phase emulsion (HIPE) presents an attractive approach for fabricating porous materials, however, most of which require external energy input (e.g., heat, UV) to solidify soft colloid templates into robust polymeric skeleton structures. Herein, a ketone-group-containing ambient-condition curable (ACC) copolymer was prepared in order to create a polyHIPE system based on the keto-hydrazide chemistry. Tailored design is made possible by the adaptable construction feature of ACC copolymer, and its amphiphilic properties significantly expand the selection of water-in-oil (W/O) HIPE stabilizers. By utilizing the unmodified ZnO nanoparticles as stabilizers and anti-shrinkage agents based on ionic crosslinking, and employing the ACC copolymer solution as the continuous phase, we streamlined the stabilization modification step, removed the need for purifying polyHIPE, and established a rapid, straightforward, and cost-effective polyHIPE preparation protocol. Results demonstrated that the obtained polyHIPEs exhibit ideal pore structures, with densities as low as 0.046 g/cm³ and porosities exceeding 90%, exhibiting remarkable stability, 3D printing feasibility, and the capacity for crosslinking under ambient circumstances. By using Soxhlet extraction, the gel content of polyHIPEs was found to be 65.5%, and mechanical characteristics were assessed up to 1.9 MPa. The technique’s successful 20-fold scaled-up HIPE production further confirms it as a promising and straightforward approach for large-scale, energy-saving, and environmentally friendly manufacture of self-curable HIPEs.

Cobalt/Iron Bimetallic Biochar Composites for Lead(II) Adsorption: Mechanism and Remediation Performance.

The performance of nano-zero-valent iron for heavy metal remediation can be enhanced via incorporation into bimetallic carbon composites. However, few economical and green approaches are available for preparing bimetallic composite materials. In this study, novel Co/Fe bimetallic biochar composites (BC@Co/Fe-X, where X = 5 or 10 represents the CoCl2 concentration of 0.05 or 0.1 mol L-1) were prepared for the adsorption of Pb2+. The effect of the concentration of cross-linked metal ions on Pb2+ adsorption was investigated, with the composite prepared using 0.05 mol L-1 Co2+ (BC@Co/Fe-5) exhibiting the highest adsorption performance. Various factors, including the adsorption period, Pb2+ concentration, and pH, affected the adsorption of Pb2+ by BC@Co/Fe-5. Further characterisation of BC@Co/Fe-5 before and after Pb2+ adsorption using methods such as X-ray diffraction and X-ray photoelectron spectroscopy suggested that the Pb2+ adsorption mechanism involved (i) Pb2+ reduction to Pb0 by Co/Fe, (ii) Co/Fe corrosion to generate Fe2+ and fix Pb2+ in the form of PbO, and (iii) Pb2+ adsorption by Co/Fe biochar. Notably, BC@Co/Fe-5 exhibited excellent remediation performance in simulated Pb2+-contaminated water and soil with good recyclability.

Superelastic carbon aerogels with anisotropic and hierarchically-enhanced cellular structure for wearable piezoresistive sensors

Elastic carbon aerogels have promising applications in the field of wearable sensors. Herein, a new strategy for preparing carbon aerogels with excellent compressive strength and strain, shape recovery, and fatigue resistance was proposed based on the structure design and carbonization optimization of nanocellulose-based precursor aerogels. By the combination of directional freezing and zinc ion cross-linking, bacterial cellulose (BC)/alginate (SA) composite aerogels with high elasticity and compressive strength were first achieved. The existance of zinc ions also significantly improved the carbon retention rate and inhibited structural shrinkage, thus making the carbon aerogels retain ultra-high elasticity and fatigue resistance after compression. Moreover, the carbon aerogel possessed excellent piezoresistive pressure sensing performance with a wide detection range of 0–7.8 kPa, high sensitivity of 11.04 kpa-1, low detection limit (2 % strain), fast response (112 ms), and good durability (over 1,000 cycles). Based on these excellent properties, the carbon aerogel pressure sensors were further successfully used for human motion monitoring, from joint motion to and speech recognition.

Comprehensive enhancement of flame retardant starch/cellulose/diatomite composite foams via metal-organic coordination

In recent years, considerable attention has been given to the utilization of biomass for producing bio-based foams, such as starch-based foams. Despite their renewability and widespread availability, these foams still present certain drawbacks regarding their poor mechanical properties and flammability. To tackle these concerns, a metal ion cross-linking strategy was employed by incorporating calcium ions (Ca2+) solution into foamed starch/cellulose slurry. Followed by ambient drying, starch/cellulose composite foam was successfully fabricated with a remarkable enhancement in various properties. Specifically, compared to the control sample, the compressive strength and modulus increased by 26.2 % and 123.0 %, respectively. Additionally, the Ca2+ cross-linked starch/cellulose composite foam exhibited excellent heat resistance, water stability, and flame retardancy. The limiting oxygen index (LOI) reached 52 %, with a vertical combustion rating of V-0. Along with the addition of 2 phr diatomite, it demonstrated a significant enhancement on flame retardancy with a LOI of 65 %, although the apparent density of the composite foam was not low enough. This study indicated a green and simple method to obtain starch-based composite foams with enhanced comprehensive properties including thermal, water stability, mechanical, and flame retardancy, expanding their potential applications in areas such as building materials and rigid packaging.