Oil-in-water Pickering emulsions stabilized by nanofibrillated cellulose (NFC) were used to encapsulate and deliver vitamin D3. NFC was extracted from a waste product of the food industry, mangosteen ...(Garcinia mangostana L.) rind, using dissolution in a hot sodium hydroxide solution, bleaching using hydrogen peroxide, and shearing using a high-pressure homogenizer. This yielded cellulose fibers with a diameter of around 60 nm and a length of several micrometers. Emulsions containing 10% w/w oil (0.01% w/w vitamin D3 and 9.99% w/w soybean oil), 0.10–0.70% w/w NFC as emulsifier, and phosphate buffer (pH 7) were prepared. The effect of NFC on lipid digestion and vitamin bioaccessibility was investigated using a simulated gastrointestinal tract (GIT) model, which included mouth, stomach and small intestine phases. The rate and extent of lipid digestion, as well as the vitamin bioaccessibility, decreased with increasing NFC concentration. Numerous physicochemical phenomena may account for this effect, including the ability of NFC to: act as a physical barrier at the lipid droplet surfaces; to promote droplet flocculation in the gastric phase; and, to increase the viscosity of the aqueous phase. The slight decrease in vitamin D3 bioaccessibility at higher NFC levels, was probably due to the lower level of lipid digestion. Our results indicate that mangosteen fiber can be used to stabilize oil-in-water emulsions, and only has a minor effect on lipid digestion and vitamin bioaccessibility when used at relatively low levels. This information may be useful for the rational design of functional foods from natural waste-products, such as mangosteen rind.
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•The ability of nanofibrillated cellulose to encapsulate and deliver vitamin D3 was studied.•Cellulose concentration affected the lipid digestion rate and extent.•Lipid digestion was inhibited at higher cellulose contents.•Vitamin D bioaccessibility slightly decreased with increasing cellulose content.•Low levels of nanofibrillated cellulose should be used to deliver oil-soluble vitamins.
Fig. 1: From cellulosefibers to high quality CNF.
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The production of nanocellulose has garnered increased attention in the past decades and is now the second-ranked priority of the ...European bioeconomy. The number of papers published on nanocellulose has increased by six fold in the last five years and studies on nanofibrillated cellulose (CNF) represent nearly 65% of that literature. Studies in the most recent years have focused on CNF production at industrial scales, since it is hampered by high energy consumption and cost. Chemical pretreatment of cellulose fibers is essential to improving nanofibrillation and decreasing energy consumption. Moreover, functionalized CNFs and bacterial cellulose (BC) endowed with additional properties are expected to be used for high-value added applications. This nanoscale material is bio-based, biodegradable, and biocompatible with very promising barrier and mechanical properties, although its high hydrophilicity is a limiting factor for some applications. CNF and BC modification is also a key step to improve its compatibility with different macromolecular matrices in the elaboration of composite materials. This review aims at providing a guide to CNF chemical pretreatment possibilities, optimize its production, and exhaustively report the available CNF and BC chemical modification techniques capable of producing high value-added materials.
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•Alternating multilayered NFC/Fe3O4&CNT/PEO films were prepared via an AVF approach.•The NFC/Fe3O4&CNT/PEO film exhibited wonderful EMI SE and thermal conductivity.•The ...NFC/Fe3O4&CNT/PEO film showed superb flexibility and toughness.•In an actual application test, the prepared film could block electromagnetic waves.
Along with the integration and miniaturization of modern electronics, electromagnetic radiation and heat accumulation have become the increasingly serious problem. However, it is still greatly challenging to achieve high electromagnetic interference (EMI) shielding effectiveness (SE) and thermal conductivity (TC) simultaneously in polymeric composite films. Herein, flexible and tough nanofibrillated cellulose/Fe3O4&carbon nanotube/Polyethylene oxide (NFC/Fe3O4&CNT/PEO) films featured with alternating multilayered structures were successfully prepared by a facile alternating vacuum-assisted filtration (AVF) method. The conductive CNT/PEO acted as the EMI shielding layer; the polymeric NFC/Fe3O4 played the role as supporting substrate and synergistically enhanced the EMI shielding performance. Thus, alternating multilayered NFC/Fe3O4&CNT/PEO films exhibited the high electrical conductivity of 3.9 × 103 S/m, excellent EMI SE of 30.3 dB, and thermal conductivity of 9.53 W m−1 K−1. In addition, NFC/Fe3O4&CNT/PEO films showed wonderful mechanical properties with a tensile strength of 36.03 MPa, a toughness of 2.98 MJ/m3, and an elongation at break of 19.1%, due to strong hydrogen bonding between NFC and PEO and hierarchical “zigzag” cracks. Interestingly, alternating multilayered structures could highly improve the toughness and ductility of composite films, in contrast to pure NFC. In the actual EMI shielding application measurement, NFC/Fe3O4&CNT/PEO films were proved to effectively block the electromagnetic wave transmission. This effort opens a creative avenue for designing and constructing flexible and tough composite films with both excellent EMI shielding performance and fascinating heat removal ability.
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•The Zn foil is coated by carbon black to enlarge the electroactive surface area.•Nanofibrillated cellulose is used as an effective binder to adhere carbon black.•The modified anode ...can eliminate the dendritic growth and side reactions.•Excellent interface stability between the anode and electrolyte is achieved.•The Zn-MnO2 battery with modified anode shows significantly improved cyclability.
Aqueous zinc-ion batteries have received significant attention due to their low cost and high safety. However, the unsatisfactory cycling performances caused by the dendritic growth on the Zn anode limit their practical applications. Herein, we propose to modify the conventional Zn foil anode by using carbon black coating and nanofibrillated cellulose binder. The carbon black can form an electrically conductive network, thus greatly enlarging the electroactive surface area, while the nanofibrillated cellulose can act as an electrolyte reservoir to facilitate charge transports. Thanks to that, the modified anode can significantly eliminate the dendritic growth and side reactions, therefore ensuring excellent interface stability with the electrolyte even at a commercial-level areal capacity of 5 mAh g−1. With the modified anode, the Zn-MnO2 battery gives a high capacity retention of 87.4% after 1000 cycles, much higher than that with the unmodified Zn foil (42.6%). This study discloses a facile, scalable, and cost-effective strategy to achieve dendrite-free metal electrodes towards great cyclability.
•Recent developments in production of cellulose nanofibrils (CNF) were reviewed.•Mechanical disintegration processes and biological/chemical pretreatments were discussed.•Issues of CNF fractionation ...and quantification of the extent of fibrillation were addressed.•An overview of various CNF products, e.g., powders, films, hydrogels and aerogels was proposed.
This review describes the recent advances in production of cellulose nanofibrils (CNF), otherwise known as nanofibrillated cellulose (NFC), microfibrillated cellulose (MFC) or cellulose nanofibers, a material with significant barrier, mechanical and colloidal properties, low density, renewable and biodegradable character. The above properties make CNF promising for applications in such fields as papermaking, composites, packaging, coatings, biomedicine and automotive. In this review, CNF production methods are summarized, covering raw materials selection, structural and chemical aspects necessary for understanding the nanofibril extraction process, conventional and novel mechanical disintegration techniques, as well as biological and chemical pretreatments aimed at facilitating nanofibril isolation. The issues of fractionation, performed with the objective of retrieving the residual microscopic fiber fragments from CNF suspensions, are addressed. Additionally, the preparation of CNF in various forms, such as suspensions, water-redispersible powders, films or nanopapers, hydrogels and aerogels, is discussed.
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•The AgNWs/NFC aerogel was designed by directional freeze-casting followed by thermal welding for multifunctional strain sensor.•The assembled sensor displayed desirable sensitivity ...(3.86 kPa−1) and exceptional stability and durability (over 10,000 cycles).•The sensing mechanism of the sensor was investigated systematically.•The multifunctional aerogel possessed a potential candidate for wearable devices.
Wearable strain sensors have drawn growing interest in the field of intelligent electronic devices because of their inherent advantages including miniaturization and portability. For practical applications, strain sensors with lightness, flexibility, and high sensitivity are urgently desired. Herein, the interconnected silver nanowires (AgNWs) are assembled into the nanofibrillated cellulose (NFC) aerogel through unidirectional freeze-drying yielding an ultralight and conductive AgNWs/NFC aerogel (SNA) with ordered pore orientation. After thermal welding, the SNA possesses unique electron transfer channels, which can efficiently eliminate the interfacial electrical resistance at the AgNWs junctions and bring an impressive conductivity enhancement for the composite aerogel. Benefiting from the synergy of the desired microstructure and superior conductivity of as-prepared aerogel, the derived sensor shows desirable sensitivity (3.86 kPa−1), fast response time (180 ms), ultralow density (less than 13.58 mg/cm3) and detection limit of 0.5% strain, and exceptional stability and durability (over 10,000 cycles). Significantly, the integrated conductive network in SNA simultaneously offers real-time monitoring of subtle deformations and electrophysiological signals, which enables the designs of wearable device, acoustic sensor, and vehicles’ speed and loading detector. The presented strategy opens up a new possibility for designing and manufacturing next-generation multifunctional strain sensor to bring the technology much closer to commercialization.
This work aimed to study the stabilization mechanism induced by different morphologies of cellulosic fiber in O/W emulsion. Three types of cellulosic fibers were named squashed cellulose, ...incompletely nanofibrillated cellulose, and completely nanofibrillated cellulose, respectively. Squashed cellulose acted as barriers between the droplets to stabilize emulsion via depletion flocculation, whereas incompletely nanofibrillated and completely nanofibrillated cellulose formed covering layer via interfacial adsorption and connected adjacent droplets to create the droplet-fiber network structure via bridging flocculation. Differently, completely nanofibrillated cellulose formed the denser covering layer leading to a more stability of droplet. Importantly, it had the higher capacity of bridging flocculation, which can tightly connect the adjacent droplets to form a stronger droplet-fiber 3D network structure. Consequently, in rheological analysis including creep compliance, and dynamic modulus, the corresponding emulsions showed excellent anti-deformation ability and dynamic stability. This study provides practical guidance on the productions of foodstuff and cosmetic.
•Different morphologies of cellulosic fiber obtained by mechanical fibrillation.•Squashed cellulose stabilized Pickering emulsions by depletion flocculation.•Interfacial adsorption and bridging flocculation formed droplet-fiber 3D structure.•Rheological properties revealed the interaction between droplets and cellulose.
Low density and high strength nanofibrillated cellulose aerogel based on pinewood were prepared by the freeze-drying method. The study was focused to reduce the thermal conductivity of the prepared ...aerogel along with the improvement in mechanical strength. Synthesized nanofibrillated cellulose aerogel had demonstrated high porosity (99.4%) and ultra low density (8.1 kg/m3). Morphological analysis of aerogel by FESEM (Field emission scanning electron microscope) confirmed nano-dimensional diameter of cellulosic fibres and pore size distribution of aerogel in the range of 2–50 nm. X-ray microtomography confirmed the three-dimensional, monolithic and porous structure. The mechanical and thermal transport properties of aerogel have been tailored via controlling the concentration of nanofibrillated cellulose in the hydrogel. The synthesized aerogel act as a thermal insulator with the thermal conductivity of 25.5 mW/m K at 1.00 wt% of aerogel, which is near to the thermal conductivity of air in ambient condition. Cyclic compression strength of aerogel was investigated at 25%, 50% and 75% strain for 50 cycles. 1.00 wt% aerogel was 70% recoverable at 25% strain but reflecting strain-hardening behaviour at 75% strain. 1.00–1.50 wt% aerogels have shown ductile, flexible and compressible behaviour. Nanofibrillated cellulose aerogel would be a candidate in practical applications such as heat insulator, kinetic energy absorber and energy efficiency building.
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•Low density (8.1 kg/m3) and high porosity aerogel based on nanofibrillated cellulose have prepared by freeze drying method.•Morphological analysis by FESEM concludes nano-dimensional diameter of cellulose fibers and consistency of aerogels.•X-ray microtomography analysis confirms three dimensional porous and homogeneous structure of aerogel.•Aerogel shows high cyclic compressibility and comparable thermal conductivity with air.
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Hydrophobic oleic acid/water interfaces are negatively charged. Hence, the use of cationic nanocelluloses as stabilizers of Pickering emulsions could improve the colloidal stability ...due to the electrostatic complexation at the oil-water interface.
Two cationic nanofibrillated cellulose (cNFCs) with two degrees of substitution were prepared and used as stabilizers of Pickering emulsions. The adsorption of cNFCs at the oil: water interface was evaluated by interfacial tension, atomic force microscopy, and centrifugation measurements. LUMiSizer and optical microscopy techniques were used to analyze the colloidal stability and oil droplets morphology, respectively. Besides, the rheological behavior of the continuous aqueous phase was determined through flow and stress sweep curves. Finally, the dispersion of cNFCs in a diluted emulsion was visualized by cryogenic transmission electron microscopy (cryo-TEM).
Cationic NFCs were more efficient in partitioning to the oil:water interface compared to their anionic analogous, oCNF. The electrostatic attraction between the positively charged trimethylammonium groups and the negatively charged deprotonated oleic acid reduced the interfacial tension and improved the colloidal stability of O/W Pickering emulsions. cNFCs dispersed in the aqueous phase were found to increase the viscosity, decelerating the oil drops coalescence. Therefore, the stabilization of cNFCs Pickering emulsions had a synergistic effect from the electrostatic complexation at the liquid-liquid interface and network formation in the aqueous phase, as visualized by cryo-TEM.
Nanocellulose is a well-known stabilizer for several colloidal dispersions, including emulsions and solid nanoparticles, replacing surfactants, polymers, and other additives, and therefore providing ...more minimalistic and eco-friendly formulations. However, could this ability be extended to stabilize oil droplets and inorganic nanoparticles simultaneously in the same colloidal system? This work aimed to answer this question. We evaluated both cationic and anionic nanofibrillated celluloses to stabilize both titanium dioxide nanoparticles and oil droplets. The resulting suspensions held their macroscopic stability for up to 2 months, regardless of pH or surface charge. Cryo-TEM images revealed a complex network formation involving nanofibers and TiO2 nanoparticles, which agrees with the high viscosity values and gel-like behavior found in rheology measurements. We propose that the formation of this network is responsible for the simultaneous stabilization of oil droplets and TiO2 nanoparticles, and that this may be used as a formulation tool for other complex systems.
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