Increasing electromagnetic pollution calls for electromagnetic interference (EMI) shielding materials, especially sustainable, lightweight, and environmentally stable, biomass-based materials. MXene-coated wood (M/wood) is prepared by simply spraying MXene sheets on the wood surface. Varying this spray coating manipulates the shielding performance and its application to different wood species. The M/wood exhibits high electrical conductivity (sheet resistance is only 0.65 Ω/sq) with an excellent EMI shielding effectiveness of 31.1 dB at 8.2?~?12.4 GHz and is also fire retardant. Furthermore, waterborne acrylic resin (WA) is coated on M/wood to enhance environmental stability. The WA coating improves EMI shielding performance stability after water-soaking and drying testing and prevents the peeling of MXene from wood. These satisfactory properties of WA-M/wood and the facile manufacturing approach promote the feasibility of wood-based EMI shielding materials.
Graphical abstractCellulose-based triboelectric nanogenerators (TENGs) can provide power for various monitoring devices and are environmentally friendly and sustainable. Chemical functional modification is a common method to improve the electrical output performance of cellulose-based TENGs. In this work, an environmentally friendly high-performance triboelectric nanogenerator based on a polydopamine/cellulose nanofibril (PDA/CNF) composite membrane and fluorinated ethylene propylene was developed. Dopamine generates polydopamine nanoparticles through oxidative self-polymerization and adheres to the surface of nanofibers. The synergistic effect of amino group introduction and membrane surface microstructure effectively enhanced the output performance of TENGs to a certain extent. The effects of PDA content, CNF composite film thickness and different working conditions on the electrical output were systematically investigated. The optimized PDA/CNF-TENGs exhibited an enhanced electrical output performance with voltage, current, and power density values of ≈205 V, ≈20 µA, and ≈48.75 μW·cm?2, respectively. The PDA/CNF-TENGs exhibited stable and identifiable signals when used as a self-powered sensor for human motion monitoring, showing the potential prospects of cellulose materials for TENGS and other electronic applications.
Graphical abstractCellulose nanofibril (CNF) aerogels have attracted great interests in recent years due to the low cost, sustainability and biocompatibility of raw CNF. However, the poor thermal stability and flammable feature of CNF aerogels have limited their wider applications. In this paper, polydopamine/CNF composite aerogels with good comprehensive properties are fabricated by modification of CNF with polydopamine and metal coordination bonds crosslinking. The microstructure and properties of composite aerogels are thoroughly characterized by a variety of tests. It is found that the microstructure of aerogels are more regular and the compressive strength of aerogels are enhanced by the incorporation of polydopamine and Fe3+ crosslinking. Importantly, the thermal stability and flame resistance of aerogels are significantly improved, which permit the application of composite aerogels in high-temperature thermal insulation. In addition, the reversible characteristic of metal coordination bonds allows the water induced healing of fractured composite aerogels. This study is expected to provide information for future development of green and high-performance aerogels.
Graphic abstractIn this study, the effect of pectin extraction method on the properties of cellulose nanofibers (CNFs) isolated from sugar beet pulp (SBP) was studied. Pectin was extracted by the industrially practiced method by sulfuric acid hydrolysis or by enzymatic hydrolysis using a cellulase/xylanase enzymes mixture. The CNFs were then isolated by high-pressure homogenization and investigated in terms of their chemical composition, crystallinity, size, degree of polymerization, and re-dispersion in water after freeze-drying. The mechanical properties and surface characteristics of CNF films were also studied. The results showed that fibrillation of the de-pectinated SBP was more efficient for the acid hydrolyzed SBP. CNFs from the acid-hydrolyzed SBP had a slightly wider diameter, higher crystallinity, viscosity, and α-cellulose content but a lower degree of polymerization than CNFs from the enzyme-hydrolyzed SBP. Owing to the presence of more residual hemicelluloses in the CNFs from the enzyme-hydrolyzed SBP, the CNFs had higher re-dispersion ability in water. CNF films from enzyme-hydrolyzed SBP displayed slightly better mechanical properties and higher water contact angle than acid-hydrolyzed CNF films.
Graphic abstractSurface modification of fabrics is a powerful strategy that can endow fabrics with desired effects while keeping the intrinsic properties. Herein, an ordinary strategy, dipping-drying based layer-by-layer self-assembly (LbL) coating, is reported to functionalize fabrics’ surfaces. Firstly, the novel cation waterborne polyurethanes (QAHDPU) and anion waterborne polyurethanes (HDPU) are successfully designed and synthesized. By incorporating targeted molecule, hydantoin diol (HD) and quaternary ammonium salt with long alkyl chain (DOQA), the QAHDPU are antibacterial and hydrophobically functionalized. Taking advantage of strong adhesion, waterborne polyurethanes (WPUs) are physically bonded to surfaces of fabrics to generate durable antibacterial and hydrophobic fabrics. The QAHDPU with long alkyl chain combined with rough and porous fabric surface fabricates hydrophobic fabric surface, which can prevent bacteria from adhering to the fabrics. Furthermore, the coated fabrics present excellent antibacterial properties after chlorination, forming a second barrier against bacteria. The chlorinated coated fabrics, can inactivate 85.0–99.9% of Staphylococcus aureus and 85.0–97.7% of Escherichia coli with contact time of 60 min. The hydrophobic properties of coated fabrics are greatly improved with water contact angles of 122.0°–141.1°. In addition, the proposed method is applicable for a variety of fibers and expected to be used for industrial production.
Graphical abstractMembrane applications for the separation of surfactant-stabilized emulsions are often constrained by a deficiency in permeability and anti-fouling properties. Herein, special wetted cotton fabric with a protective layer (P-MH@CF) for durable anti-fouling performance was synthesized by a two-step method, which was related to interfacial ion migration technology and unilateral spraying treatment. Permeability of water and separation performance of P-MH@CF membrane were investigated systematically. Emulsions stabilized by anionic, cationic, or non-ionic surfactant were successfully separated with high efficiency. In the process of separation, the oil droplets surrounded by surfactants were difficult to demulsify and gathered physically on the membrane surface to form a “cream layer”. The stearic acid acted as a protective layer, like a quilt, protecting the membrane from contamination. The membrane retained robust reusability for separation even after the “cream layer” had been washed off, which was promising for the remediation of oily wastewater containing surfactants.
Graphical abstractTo obtain high performance of nanocomposite films made of cellulose nanofibrils (CNFs) and montmorillonites (MMTs), highly ordered nanostructures and abundant interfacial interactions are of extreme importance, especially for CNF film with high MMT content. Here, we tend to unveil the influence of exfoliation degree of MMTs and their interfacial interactions with CNFs on the properties of ensuing nanocomposite films. Monolayer MMTs (ML-MMTs) prefer to form highly ordered nanostructure during water evaporation induced self-assembly. The obtained nanocomposite film with 30 wt% ML-MMTs exhibits a tensile strength of 132 MPa, a total light transmittance of 90.2% (550 nm), and water vapor transmission rate (WVTR) of 41.5 g mm/m2 day, better than the film made of original MMTs (O-MMTs) and CNFs (30 MPa strength, 60% transparency, and 78.7 g mm/m2 day WVTR). Moreover, the physical properties (153 MPa strength and 20.9 g mm/m2 day WVTR) of nanocomposite film can be further enhanced by constructing ionic interactions between the ML-MMT and CNF using 0.5 wt% cationic polyethylenimine (PEI). However, as the amount of PEI continues to increase, its performance will be deteriorated dramatically because of the disordered orientation of ML-MMTs. This work could provide an insight into the fabrication of high performance MMT/CNF nanocomposite film for advanced applications.
Graphical abstractEucalyptus cellulose is usually pre-treated by oxidation with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), NaBr and NaClO at pH 10.5 and 25 °C before the mechanical process required to obtain cellulose nanofibers (CNFs). In this study, different aspects to improve the effectiveness and sustainability of the TEMPO-mediated oxidation are analyzed. The optimization was carried out at different reaction times by modifying both the concentration of the NaClO and the amount of the catalysts (TEMPO and NaBr). Results show that the carboxyl groups increased up to 1.1 mmol/g with 5 mmol NaClO/g after 50 min, and that the catalyst concentration can be reduced to 0.025 mmol TEMPO/g and 0.5 mmol NaBr/g to minimize costs while maintaining the high fibrillation degree of the CNFs. The kinetic of the reaction can be considered as zero-order with respect to NaClO, and as first order with respect to cellulose. As a result of this work, the catalyst doses are reduced up to 75% compared to the most widely used catalyst doses (0.1 mmol/g TEMPO and 1 mmol/g NaBr), obtaining highly fibrillated CNFs with a lower environmental impact. This reduction of catalyst doses will reduce the costs and facilitate the implementation of CNF production at industrial scale.
Graphical abstractIn this, an efficient flame retardant composite has been prepared using biowaste derived phosphorous groups decorated graphene supported nanomaterial. The eggshell was utilized as a source of calcium carbonate, which was converted to monocalcium phosphate (CP) by phosphoric acid treatment. As-prepared monocalcium phosphate was functionalized with graphene to prepare graphene functionalized monocalcium phosphate (GCP). The GCP-coated fabric didn't ignite during the flame test and sustained more than 600 s on continuous exposure to flame without changing its initial length and shape. Whereas, graphene oxide (GO), and CP coated cotton fabric burnt out very easily within a short time. The efficient flame retardant property of as synthesized GCP coated cotton fabric was confirmed with a high limiting oxygen index (34.1) and char length of 2.5 cm was generated from the VFT test. The synthesized GCP coated cotton fabric also confirmed efficient flame retardant properties. This facile method enables an easy process for mass production of cost-effective, bio-waste derived nanomaterial for a significantly highly efficient candidate for different applications in sustainable chemistry, including flame-retardant applications.
Graphical abstractLife-threatening diseases, especially those caused by pathogens and harmful ultraviolet radiation (UV-R), have triggered increasing demands for comfortable, antimicrobial, and UV-R protective clothing with a long service life. However, developing such textiles with exceptional wash durability is still challenging. Herein, we demonstrate how to fabricate wash durable multifunctional cotton textiles by growing in situ ZnO-TiO2 hybrid nanocrystals (NCs) on the surface of cellulosic fabrics. The ZnO-TiO2 hybrid NCs presented high functional efficiency, owing to their high charge transfer/separation. Ultrafine fiber surface pores, utilized as nucleating sites, endowed the uniform growth of NCs and their physical locking. The resulting fabrics presented excellent UV protection factors up to 54, displayed bactericidal efficiency of 100% against Staphylococcus aureus and Escherichia coli, and optimum self-cleaning efficacy. Moreover, the functionalized textiles exhibited robust washing durability, maintaining antibacterial and anti-UV-R efficiency even after 30 extensive washing cycles.
Graphical abstractExploitation of cotton fabric as electromagnetic interference (EMI) shielding substrates have attracted a growing interest due to their desirable low carbon footprint, economic feasibility, and sustainability. Herein, a facile strategy was proposed for preparing a cellulose-based multifunctional PNIPAAm/PPy hydrogel/cotton (PPHC) EMI shielding composites with simultaneous high-efficient electro-photo-thermal conversion and comfort regulation functions. The PPHC was fabricated via in situ polymerization conductive PPy hydrogel on cotton substrate followed by deposition of PNIPAAm. Benefiting from the unique interconnected three-dimensional networked conductive structure of PPy hydrogel, the obtained PPHC composites exhibited high conductivity (15 mS/cm), and EMI shielding effectiveness (EMI SE?~?40 dB) in the frequency of 8.2–12.3 GHz. Moreover, the PNIPAAm coating endowed the composite fabrics with adjustable wettability performance in response to external temperature, leading to excellent comfort regulation performance. This work provided feasible avenue toward low cost and sustainability cotton-based EMI shielding composites with efficient EMI shielding and comfort regulation performance.
Graphical abstractA cellulosic material has been synthesized that could efficiently and selectively adsorb organic and inorganic contaminants from aqueous solutions without interference from competing adsorption sites. Cellulose-graft-tetraethylenepentamine molecular imprinted polymer (C-TEPA-MIP) was synthesized by using 4-nitrophenol (4-NP) as the template. The C-TEPA-MIP adsorbent could adsorb 4-NP and Cr(VI) simultaneously and selectively, without being affected by the competitive adsorption sites of each of these pollutants. The adsorption of 4-NP was predominantly due to the imprinted sites of 4-NP in C-TEPA-MIP that were located inside of the adsorbent, whereas that of Cr(VI) was primarily due to the amine groups of TEPA found on the surface of the adsorbent. Compared with the non-imprint polymer synthesized without the template, C-TEPA-MIP showed higher selectivity for both 4-NP and Cr(VI) in unitary and binary systems. In addition, C-TEPA-MIP exhibited good stability and recyclability for 4-NP, which makes it a promising candidate material for applications concerning wastewater treatment.
Graphical abstractThe surgical masks have been essential consumables for public in the COVID-19 pandemic. However, long-time wearing masks will make wearers feel uncomfortable and massive discarded non-biodegradable masks lead to a heavy burden on our environment. In this paper, we adopt degradable chitosan@silver (CS@Ag) core–shell fibers and plant fibers to prepare an eco-friendly mask with excellent thermal comfort, self-sterilization, and antiviral effects. The thermal network of CS@Ag core–shell fibers highly improves the in-plane thermal conductivity of masks, which is 4.45 times higher than that of commercial masks. Because of the electrical conductivity of Ag, the fabricated mask can be electrically heated to warm the wearer in a cold environment and disinfect COVID-19 facilely at room temperature. Meanwhile, the in-situ reduced silver nanoparticles (AgNPs) endow the mask with superior antibacterial properties. Therefore, this mask shows a great potential to address the urgent need for a thermally comfortable, antibacterial, antiviral, and eco-friendly mask.
Graphical abstractIonic cellulose nanocrystals (CNCs) are interesting surface-active particles for encapsulating a lipophilic liquid in water. A CNC is modified chemically to a negative charge (an S-CNC) by surface treatment with sulfuric acid. Despite the amphiphilic nature of S-CNCs, it is difficult to determine the degree of substitution for emulsification of lipophilic liquids, especially when the surface energy is low and polarity is high. Here, we control the substitution of S-CNCs by desulfation of S-CNCs (dS-CNCs) using a low-concentration hydrochloric acid solution. Decreased surface charge of S-CNCs was expected, and the lipophilic affinity of dS-CNCs increased compared with those of S-CNCs. Six oils with differing surface tensions were selected for determination of the effect of charged CNCs on emulsification. The stability of the emulsion was evaluated by emulsion fraction, emulsion particle size, and surface tension of emulsified solutions from dS-CNCs and oils.
Graphical abstractThe development of a simple surface barrier discharge plasma device is presented to enable more widespread access to and utilization of plasma technology. The application of the plasma device was demonstrated for pretreatment of wood prior to application of protective coatings for outdoor usage. The coatings' overall performance was increased, showing a reduction or absence of cracking due to weathering on plasma-pretreated specimens. Moreover, after ten months of outdoor weathering, the plasma-pretreated specimens showed fewer infections with biotic factors and improved adhesion performance in cross-cut tests, while the surface gloss performed independently from plasma pretreatment. In contrast to that, plasma-pretreated specimens were slightly more prone to discoloration due to outdoor weathering, whereas the plasma pretreatment did not impact the initial color after coating application.
Graphic abstractMultifunctional materials for water purification have attracted significant attention due to the increased water pollution problems. However, fabricating the low-cost, effective, and recyclable separation material for wastewater containing various hazardous substances is still a challenge. Herein, we developed an Ag/TiO2@PDMS coated cotton fabric with self-cleaning ability, high flux, superior visible-light photocatalytic ability, and recyclability via the “powder?+?glue” strategy. The composites are superhydrophobic (water contact angle 157°) and show high separation efficiency. After 20 times of repeated use, the separation efficiency remains 16,322 Lm?2 h?1, and methylene blue (MB) 's degradation rate remains almost unchanged. The high oil purification, catalytic property, excellent stability in harsh conditions, and recyclability enable the material as a satisfactory candidate for water purification.
Graphical abstractThis study introduces an effective route to fabricate chitosan (CS)-based film. The films were prepared through cross-linking reaction between CS and hydroxyethyl cellulose (HEC) using epichlorohydrin (ECH) as the cross-linker and simultaneously in-situ loading with CuO nanoparticles. FT-IR and loading efficiency results indicated the occurrence of inter- and intra-molecular cross-linking reaction between CS and HEC. XRD and EDS analyses showed that the CuO nanoparticles were evenly deposited onto CS film matrixes. SEM characterization showed that the films were of compact, dense and uniform cross morphologies, as well as obvious voids. The films also exhibited desired swelling ratio and water vapor permeability. The enhanced tensile strength was obtained with a maximum value of 77.02?±?3.26 MPa, while the stretch-ability slightly decreased. The thermal stability of the films decreased after cross-linking with HEC. The antibacterial ability of the films was generally improved with the increase of HEC and ECH contents.
Graphical abstractPreparation and properties of epichlorohydrin-cross-linked chitosan/hydroxyethyl cellulose based CuO nanocomposite films
Herein, cellulose nanofibrils (CNF), alkali lignin (AL), and montmorillonite (MMT) were used to produce reinforced polyvinyl alcohol (PVA) hydrogels. The effects of MMT and AL contents on the rheological properties of reinforced hydrogel were studied. Compared with PVA/CNF hydrogel, the storage modulus of 40 wt% MMT-reinforced PVA hydrogel was increased by 41.4%. The rheological properties of MMT-enhanced PVA hydrogel could be adjusted by the variation of MMT loading. Also, as the PVA matrix had a synergistic effect with the embedded MMT and AL, the composite hydrogel demonstrated high efficiency in the removal of methylene blue dye (MB) from wastewater. Adsorption tests conducted at various time intervals (60–360 min) show that the hydrogels containing same content of MMT had higher removal efficiency. The MB adsorption of PVA/2CNF-0Li-40MMT was over 98.0%, whereas its adsorption equilibrium time and maximum adsorption capacity (qm) were 360 min and 67.2 mg/g, respectively. However, an extremely high content of MMT reduced the MB adsorption rate.
Graphic abstractThe dry pulp direct kneading method is an industrially viable, low-energy process for manufacturing cellulose nanofiber (CNF)-reinforced polymer composites, where the chemically modified pulps are nanofibrillated and uniformly dispersed in the polymer matrix during melt compounding. In the present study, cellulose fibers of various sizes ranging from surface-fibrillated pulps (20 μm in width) to fine CNFs (20 nm in width) were prepared from softwood bleached kraft pulps using a refiner and a high-pressure homogenizer. These cellulose fibers were modified with alkenyl succinic anhydride and dried. The dried fibers were used as a feed material for melt compounding in the dry pulp direct kneading method to fabricate CNF-reinforced high-density polyethylene (HDPE). When surface-fibrillated pulps were employed as a feed material, the pulps were nanofibrillated and dispersed uniformly in the HDPE matrix during melt compounding. The resulting composites had much better properties—i.e., much higher tensile modulus and strength values, and much lower coefficient of thermal expansion values—than the composites produced using pulps without pre-fibrillation. However, when CNFs were used as a feed material, they were shortened and agglomerated during melt compounding, and the properties of the composites consequently deteriorated. The study concludes that surface-fibrillated pulp, which can be produced cost-effectively using a refiner on an industrial scale, is more suitable as a feed material than CNFs for melt compounding in the dry pulp direct kneading method. This finding enables the elimination of a preliminary step in the preparation of CNFs from pulps, which is a time-consuming and energy-intensive process.
Graphical abstractA variety of liquid energy exists in papermaking engineering and has not yet been developed and utilized. In addition, for the papermaking industry, the presence of slime can seriously affect the quality of the finished paper and can lead to paper breaking. The current slime control strategies cannot completely solve the problem and also have some low toxicity. In this study, a method of self-powered sterilization of cellulose fibers by using triboelectric pulsed direct current is reported. A liquid–solid triboelectric nanogenerator (L–S TENG) was used to convert the liquid energy of nanocellulose suspension into electrical energy and convert this electrical energy into pulsed direct current for self-powered sterilization of cellulose fiber. A hydrophobic coating material is used as solid triboelectric material and electrode for sterilization. Driven by L–S TENG, the electrodes exhibited an excellent sterilization rate against four microorganisms including Escherichia coli, Aspergillus niger, Candida albicans, and Klebsiella pneumoniae, which from slime in the papermaking industry. This study could provide a basic research theory for liquid energy harvesting in the papermaking industry, and also provide a new strategy for pulp sterilization.
Graphical abstract