Lysine-mediated surface modification of cellulose nanocrystal films for multi-channel anti-counterfeiting.

Utilizing advanced multiple channels for information encryption offers a powerful strategy to achieve high-capacity and highly secure data protection. Cellulose nanocrystals (CNCs) offer a sustainable resource for developing information protection materials. In this study, we present an approach that is easy to implement and adapt for the covalent attachment of various fluorescence molecules onto the surface of CNCs using the Mannich reaction in aqueous-based medium. Through the use of the Mannich reaction-based surface modification technique, we successfully achieved multi-color fluorescence in the resulting CNCs. The resulting CNC derivatives were thoroughly characterized by two dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D HSQC NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron (XPS) spectroscopy. Notably, the optical properties of CNCs were well maintained after modification, resulting in films exhibiting blue and red structural colors. This enables the engineering of highly programmable and securely encoded anti-counterfeit labels. Moreover, subsequent coating of the modified CNCs with MXene yielded a highly secure encrypted matrix, offering advanced security and encryption capabilities under ultraviolet, visible, and near-infrared wavelengths. This CNC surface-modification enables the development of multimodal security labels with potential applications across various practical scenarios.

Retraction of "Fe3O4 Nanoparticles Grown on Cellulose/GO Hydrogels as Advanced Catalytic Materials for the Heterogeneous Fenton-like Reaction".

[This retracts the article DOI: 10.1021/acsomega.9b00170.].

Scalable Fabrication of Structurally Stable Polymer Film with Excellent UV-Shielding, Fluorescent, and Antibacterial Capabilities.

This research presents a new approach to facilely fabricating a multifunctional film using polyvinyl alcohol (PVA) as the base material. The film is modified chemically to incorporate various desirable properties such as high transparency, UV-shielding, antibacterial activity, and fluorescence. The fabrication process of this film is straightforward and efficient. The modified film showed exceptional UV-blocking capability, effectively blocking 100% of UV radiation. It also exhibits strong antibacterial properties. Additionally, the film emitted bright blue fluorescence, which can be useful in various optical and sensing applications. Despite the chemical modification, the film retained the excellent properties of PVA, including high transparency (90%) at 550 nm and good mechanical strength. Furthermore, it demonstrated remarkable stability even under harsh conditions such as exposure to long-term UV radiation, extreme temperatures (-40 or 120 °C), or immersion in different solvents. Overall, this work showcases a promising strategy to develop versatile, structurally stable, transparent, and flexible polymer films with multiple functionalities. These films have potential applications in various fields that require protection, such as packaging materials, biomedical devices, and optical components.

Saccharide branched cellulose with controllable molecular structure and excellent water retention ability.

In this work, saccharide branched cellulose (saccharide b-Cel) was synthesized by combining reducing saccharides with cellulose molecules using Ugi four-component reaction (Ugi-4CR). First, the carboxyl groups required for Ugi-4CR are obtained by carboxymethylating cellulose molecules. Then, saccharide b-Cel with a controlled molecular structure is formed when the terminal aldehyde group of reducing saccharides combines with the carboxyl group and auxiliary functional group. The types of saccharides, the degree of substitution of carboxymethyl groups, and the degree of branching all affect the molecular structure of saccharide b-Cel. Through molecular structural regulation, the relationship between the branching structure and water retention ability of saccharide b-Cel was examined in detail. This work not only provides new insights into the synthesis of cellulose derivatives, but it also provides a template for the synthesis of other biomass derivatives.

Multifunctioning of carboxylic-cellulose nanocrystals on the reinforcement of compressive strength and conductivity for acrylic-based hydrogel.

Simultaneously having competitive compressive properties, fatigue-resistant stability, excellent conductivity and sensitivity has still remained a challenge for acrylic-based conductive hydrogels, which is critical in their use in the sensor areas where pressure is performed. In this work, an integrated strategy was proposed for preparing a conductive hydrogel based on acrylic acid (AA) and sodium alginate (SA) by addition of carboxylic-cellulose nanocrystals (CNC-COOH) followed by metal ion interaction to reinforce its compressive strength and conductivity simultaneously. The CNC-COOH played a multifunctional role in the hydrogel by well-dispersing SA and AA in the hydrogel precursor solution for forming a uniform semi-interpenetrating network, providing more hydrogen bonds with SA and AA, more -COOH for metal ion interactions to form uniform multi-network, and also offering high modulus to the final hydrogel. Accordingly, the as-prepared hydrogels showed simultaneous excellent compressive strength (up to 3.02 MPa at a strain of 70 %) and electrical conductivity (6.25 S m-1), good compressive fatigue-resistant (93.2 % strength retention after 1000 compressive cycles under 50 % strain) and high sensitivity (gauge factor up to 14.75). The hydrogel strain sensor designed in this work is capable of detecting human body movement of pressing, stretching and bending with highly sensitive conductive signals, which endows it great potential for multi-scenario strain sensing applications.

Significantly improve film formability of acetylated xylans by structure optimization and solvent screening.

Acetylated xylans have great potential in fabricating functional film and coating materials, which need a good solubility/dispersibility and film formability in an easily evaporable solvent. However, the changes of film formability with degree of substitution by acetyls (DSAc) in different solvent systems for xylans have not been extensively studied, which limit the application of acetylated xylans in film materials. In this study, acetylated xylans with DSAc of 0-2 were prepared and the effects of acetyl groups on solubility/dispersibility, crystallinity and film formability of xylans in water and chloroform solvent systems were investigated. Due to the change of polarity, xylans with DSAc of 0-0.62 are only soluble in water solvents, while xylans with DSAc of 1.13-2 are only soluble in chloroform/ethanol (70/30 v/v) organic solvents. We have found that the film formability of acetylated xylans is highly related to their solubility and crystallization. Film formable xylans all had good solubility in the cast solvents. However, although with good solubility, xylans with DSAc of 0-0.3 and DSAc of 1.76-2 cannot form intact films, which is due to the forming of xylan hydrate crystals and xylan diacetate crystals. With the increase of DSAc, the mechanical property of xylan film increases initially at low DSAc and decreases at high DSAc. This study provides theoretical basis for applying xylans and their derivatives in advanced functional film and coating materials with great biocompatibility and biodegradability.

Facile fabrication of cellulose-based hydrophobic paper via Michael addition reaction.

The inherent highly hydrophilic feature of cellulose-based paper hinders its application in many fields. Herein, a cellulose-based hydrophobic paper was fabricated based on surface chemical modification. Firstly, the hydrophobic acrylate components were bonded to the cellulose acetoacetate (CAA) fibers to obtain CAA graft acrylate (CAA-X) fibers through Michael addition reaction. Subsequently, CAA-X fibers were processed into paper via wet papermaking technology. The resulting paper exhibited good hydrophobic performance (water contact angle was up to 135°) with an air permeability of 24.8 µm/Pa·s. The hydrophobicity of paper was very stable and remained even after treating with different solvents. Moreover, the hydrophobic properties of this paper could be adjusted by changing the type of acrylate component. It should be noted that the surface modification strategy has no obvious effects on the whiteness (79.8%), writing, and printing properties of the cellulose fibers. Thus, it is a simple, benign, and efficient strategy for the construction of cellulose-based hydrophobic paper, which has great potential to be used in paper tableware, oil-water separation, watercolor protection, and food packaging fields.

Passerini three-component reaction for the synthesis of saccharide branched cellulose.

In this work, we investigate a multicomponent synthetic method for combining saccharides with cellulose to produce saccharide branched cellulose (b-Cel). First, cellulose is modified conventionally using carboxymethyl to create carboxyl functional groups for multicomponent reactions. The Passerini three-component reaction (Passerini-3CR) is then used to synthesize the saccharide b-Cel, with particular attention paid to the scope of the substrate and reaction process optimization. The structure of saccharide b-Cel is regulated by modifying the carboxyl group of cellulose molecules, the kind of saccharide molecules (including glucose, galactose, lactose, cellobiose, and cellulose), and the degree of branching. The branched structure of saccharide b-Cel greatly influenced its rheological characteristics and solubility. This work presents a practical method for the synthesis of artificial branching polysaccharides and is crucial for the development of innovative materials based on biomass.

Large-Scale Preparation for Multicolor Stimulus-Responsive Room-Temperature Phosphorescence Paper via Cellulose Heterogeneous Reaction.

The large-scale preparation of sustainable room-temperature phosphorescence (RTP) materials, particularly those with stimulus-response properties, is attractive but remains challenging. This study develops a facile heterogeneous B─O covalent bonding strategy to anchor arylboronic acid chromophores to cellulose chains using pure water as a solvent, resulting in multicolor RTP cellulose. The rigid environment provided by the B─O covalent bonds and hydrogen bonds promotes the triplet population and suppresses quenching, leading to an excellent lifetime of 1.42 s for the target RTP cellulose. By increasing the degree of chromophore conjugation, the afterglow colors can be tuned from blue to green and then to red. Motivated by this finding, a papermaking production line is built to convert paper pulp reacted with an arylboronic acid additive into multicolor RTP paper on a large scale. Furthermore, the RTP paper is sensitive to water because of the destruction of hydrogen bonds, and the stimuli-response can be repeated in response to water/heat stimuli. The RTP paper can be folded into 3D afterglow origami handicrafts and anti-counterfeiting packing boxes or used for stimulus-responsive information encryption. This success paves the way for the development of large-scale, eco-friendly, and practical stimuli-responsive RTP materials.

Color-Tunable, Excitation-Dependent, and Water Stimulus-Responsive Room-Temperature Phosphorescence Cellulose for Versatile Applications.

Smart-response materials with ultralong room-temperature phosphorescence (RTP) are highly desirable, but they have rarely been described, especially those originating from sustainable polymers. Herein, a variety of cellulose derivatives with 1,4-dihydropyridine (DHP) rings are synthesized through the Hantzsch reaction, giving impressive RTP with a long lifetime of up to 1251 ms. Specifically, the introduction of acetoacetyl groups and DHP rings promotes the spin-orbit coupling and intersystem crossing process; and multiple interactions between cellulose induce clustering and inhibit the nonradiative transitions, boosting long-live RTP. Furthermore, the resulting transparent and flexible cellulose films also exhibit excitation-dependent and color-tunable afterglows by introducing different extended aromatic groups. More interestingly, the RTP performance of these films is sensitive to water and can be repeated in response to wet/dry stimuli. Inspired by these advantages, the RTP cellulose demonstrates advanced applications in information encryption and anti-counterfeiting. This work not only enriches the photophysical properties of cellulose but also provides a versatile platform for the development of sustainable afterglows.

The thermodynamics of enhanced dope stability of cellulose solution in NaOH solution by urea.

The addition of urea in pre-cooled alkali aqueous solution is known to improve the dope stability of cellulose solution. However, its thermodynamic mechanism at a molecular level is not fully understood yet. By using molecular dynamics simulation of an aqueous NaOH/urea/cellulose system using an empirical force field, we found that urea was concentrated in the first solvation shell of the cellulose chain stabilized mainly by dispersion interaction. When adding a glucan chain into the solution, the total solvent entropy reduction is smaller if urea is present. Each urea molecule expelled an average of 2.3 water molecules away from the cellulose surface, releasing water entropy that over-compensates the entropy loss of urea and thus maximizing the total entropy. Scaling the Lennard-Jones parameter and atomistic partial charge of urea revealed that direct urea/cellulose interaction was also driven by dispersion energy. The mixing of urea solution and cellulose solution in the presence or absence of NaOH are both exothermic even after correcting for the contribution from dilution.

Bio-inspired synthesis of amino acids modified sulfated cellulose nanofibrils into multivalent viral inhibitors via the Mannich reaction.

Virus cross-infection via surfaces poses a serious threat to public health. Inspired by natural sulfated polysaccharides and antiviral peptides, we prepared multivalent virus blocking nanomaterials by introducing amino acids to sulfated cellulose nanofibrils (SCNFs) via the Mannich reaction. The antiviral activity of the resulting amino acid-modified sulfated nanocellulose was significantly improved. Specifically, 1 h treatment with arginine modified SCNFs at a concentration of 0.1 g/mL led to a complete inactivation of the phage-X174 (reduction by more than three orders of magnitude). Atomic force microscope showed that amino acid-modified sulfated nanofibrils can bind phage-X174 to form linear clusters, thus preventing the virus from infecting the host. When we coated wrapping paper and the inside of a face-mask with our amino acid-modified SCNFs, phage-X174 was completely deactivated on the coated surfaces, demonstrating the potential of our approach for use in the packaging and personal protective equipment industries. This work provides an environmentally friendly and cost-efficient approach to fabricating multivalent nanomaterials for antiviral applications.

High efficiency electro- and photo-thermal conversion cellulose nanofiber-based phase change materials for thermal management.

Novel phase change materials composed of polyethylene glycol (PEG), cellulose nanofibers (CNFs) and carbon nanotubes (CNTs) were developed by an efficient and environment friendly strategy. The CNFs were modified and cross-linked by chitosan to form three-dimensional network structure, which provides strong support for the resulting CNF/CNT/PEG composites. The structure and properties of CNF/CNT/PEG composites were characterized using scanning electron microscopy, spectrums, and differential scanning calorimeter. They exhibit high latent heat (158.3 J/g), low heat loss (0.75%) and excellent photo-thermal conversion (energy storage efficiency 85.6%), electro-thermal conversion (energy storage efficiency 92.3%) properties. Due to their excellent performances, CNF/CNT/PEG composites have great potential to be used as thermal management materials.

Nanolignin-based high internal phase emulsions for efficient protection of curcumin against UV degradation.

As an emulsifier, lignin exhibits excellent UV resistance on drug-loaded emulsion systems for drug delivery. However, due to the structural variation and complexity of lignins from various origins, their UV shielding performance varies with the techniques for lignin extraction, which impacts properties and the protection efficiency of lignin-based HIPEs (high internal phase emulsions). In this work, lignin nanoparticles, prepared from three lignin preparations of Eucalyptus, were used in HIPEs delivery systems to protect curcumin from degradation by UV radiation. Structures of the lignin preparations were characterized using 2D HSQC (heteronuclear single-quantum coherence) NMR (nuclear magnetic resonance), 31P NMR, and GPC (gel permeation chromatography). The residual curcumin level after 36 h UV exposure in the nanolignin-based HIPEs was over 72 %, much higher than that (< 10 % after 24 h UV exposure) in the oil phase without lignin, indicating that the nanolignin-based HIPEs with enhanced UV shielding ability protect curcumin better. Of the three lignin preparations, AL (alkali lignin), with the lowest molecular weight, highest contents of phenolic hydroxyl and carboxyl groups, and highest S/G ratio, displayed the best anti-UV radiation ability and the most uniform nanoparticle size.

Liquid metal and Mxene enable self-healing soft electronics based on double networks of bacterial cellulose hydrogels.

Liquid metal (LM) nanodroplets and MXene nanosheets are integrated with sulfonated bacterial nanocellulose (BNC) and acrylic acid (AA). Upon fast sonication, AA polymerization leads to a crosslinked composite hydrogel in which BNC exfoliates Mxene, forming organized conductive pathways. Soft conducting properties are achieved in the presence of colloidally stable core-shell LM nanodroplets. Due to the unique gelation mechanism and the effect of Mxene, the hydrogels spontaneously undergo surface wrinkling, which improves their electrical sensitivity (GF = 8.09). The hydrogels are further shown to display interfacial adhesion to a variety of surfaces, ultra-elasticity (tailorable elongation, from 1000 % to 3200 %), indentation resistance and self-healing capabilities. Such properties are demonstrated in wearable, force mapping, multi-sensing and patternable electroluminescence devices.

Novel multifunctional papers based on chemical modified cellulose fibers derived from waste bagasse.

Most technologies to produce multifunctional paper involved the defect of poor uniformity and stability. Herein, a high stability multi-functional cellulose-based paper was developed via a multiple chemical modification derived from waste bagasse. Firstly, the acetoacetyl groups was anchored on the surface of bagasse cellulose fibers by a heterogeneous transesterification. Then, paper was made based on these modified fibers. The fluorophore and gentamicin sulfate (Gen) were bonded in-situ to the paper through Hantzsch reaction and the form of enamine bond, respectively. The resulting paper exhibited excellent multifunctional properties, such as fluorescence property, antibacterial property and hydrophobic property. These properties are very stable to external environments. In addition, relatively mild surface modification has no obvious effect on fibers and shows similar whiteness and stiffness properties as that of the CAA paper. Thus, these novel functional papers held great potential for many fields such as food packaging, anti-counterfeiting, and other specialty papers.

Emulsifying properties of naturally acetylated xylans and their application in lutein delivery emulsion.

Xylans play an important role in dispersing and lubricating cellulose fibrils in lignocellulosic plant cell walls. However, the effect of acetylation on the dispersing and emulsifying properties of xylan is still unclear. In this study, we show that the natural degree of acetylation is vital to ensure xylan an excellent water solubility and emulsifying ability. Alkali extracted xylans were artificially acetylated to degree of substitution (DSAc) between 0.12 and 2.00, while the DMSO extracted originally acetylated xylan (OAX) shows a DSAc of 0.18. Artificially acetylated xylans (AX) with DSAc value similar to OAX shows water solubility and emulsifying ability similar to those of OAX and the best among all the AX samples with different DSAc. They demonstrate excellent emulsifying properties with an emulsifying activity of ~1.3 and an emulsion cream index of ~5 %. AX with the natural DSAc value also demonstrates strong barrier effects in preparing lutein delivery emulsions.

Holocellulosic fibers and nanofibrils using peracetic acid pulping and sulfamic acid esterification.

Cellulose provides promising alternatives to synthetic plastics to achieve a low carbon footprint and biodegradable materials, which have significant positive impacts on environmental protection and on human health. In this work, sulfated holocellulose fibers and sulfated holocellulose nanofibrils (SHCNFs) are prepared using a combination of delignification with derivatization to achieve high fiber yield, superior recycling performance, and less energy consumption of the final products by means of preserving hemicellulose. Derivatization of the surface with sulfate groups provides a further means to avoid excessive aggregation between adjacent cellulose surfaces. Interestingly, hemicellulose increases the accessibility of holocellulose fibers and reduces the embodied energy during sulfate esterification. The presence of hemicellulose imparts high optical transmittance, mechanical performance (ultimate strength, 390 MPa; Young's modulus, 33 GPa), and recyclability for SHCNFs. This combination of two treatments can unlock the greater potential of cellulose as a sustainable material over its entire life cycle.

Recyclable cellulose nanofibers reinforced poly (vinyl alcohol) films with high mechanical strength and water resistance.

Sargasso cellulose nanofibers (CNFs) and polyvinyl alcohol (PVA) components were composed to generate novel KCNF/PVA films by a simple and benign crosslinking strategy. Sargasso CNFs are a potential reinforcement material due to its extremely long length (15-20 µm) and natural nanostructure. The low water resistance of PVA limits their use in humid and watery environments. However, the chemical cross-linking between sargasso CNFs and PVA consumes a large number of hydrophilic hydroxyl groups, the resulting KCNF/PVA films exhibited outstanding water resistance (water contact angle 119°). Especially, the wet strength of KCNF/PVA films (50 MPa) was raised by 92 times when compared to that of pristine PVA films (0.54 MPa). Furthermore, these KCNF/PVA films could be dissolved and recycled easily. The regenerated films also show outstanding mechanical performance.