Cellulose Nanofiber Matrix Research Articles

Cellulose Nanofiber-Based Nanocomposite Films with Efficient Electromagnetic Interference Shielding and Fire-Resistant Performance.

Cellulose nanofiber (CNF) has been widely used as a flexible and lightweight polymer matrix for electromagnetic shielding and thermally conductive composite films because of its excellent mechanical strength, environmental performance, and low cost. However, the lack of flame retardancy seriously hinders its further application. Herein, renewable and biomass-sourced l-arginine (AR) was used to surface-modify ammonium polyphosphate (APP) and an environmentally friendly biobased flame retardant was synthesized by the coordination of zinc sulfate heptahydrate (ZnSO4·7H2O), which was named AAZ. AAZ was deposited on the surface of CNF by electrostatic adsorption and Zn2+ complexation. The biobased compatibilizer Triton X-100 was employed to assist the exfoliation of graphene nanoplatelets (GNPs) and their dispersion in the CNF matrix. Due to the formation of a dense lamellar layer resembling a shell structure, the CNF/GNPs composite films with a tensile strength of 52 MPa were obtained via vacuum-assisted filtration. Because the phosphorus-containing group produces a protective layer of PxOy compound and promotes the formation of a carbon layer by CNF and the combustion releases ammonia gas, the fire-resistant performance of the composite films was greatly improved. Compared with the pure CNF film, the composite film exhibits 33% reduction in PHRR value and 40% reduction in THR. In addition, the CNF/GNPs composite film with 20 wt % GNPs possessed high conductivity (2079.2 S/m) and electromagnetic interference (EMI) shielding effectiveness (37 dB). The ultrathin CNF/GNPs composite films have excellent potential for use as efficient flame retardant and EMI shielding materials.

Enhanced interfacial interaction of graphene nanoplatelets/cellulose nanofiber matrix driven by pyranine-based dispersant for efficient thermal managing materials

With the development of high-density electronics, polymer-based thermal conductive composites with excellent thermal and mechanical performance are receiving great attention. For the development of polymer-based thermal conductive composites with superior properties, it is essential to reduce the agglomeration of fillers and enhance the interfacial interactions between thermal conductive fillers and the polymer matrix. Among the several thermal conductive materials, graphene nanoplatelets (GNPs) and cellulose nanofiber (CNFs) are attracting attention. However, poor interfacial interaction between GNP and CNF leads to interfacial separation, which in turn, deteriorates its properties. Herein, we synthesized a pyranine-functionalized polyether dispersant (PyPE), which can significantly improve the interfacial interactions between GNPs and CNFs. The effect of PyPE on the dispersion behavior of GNPs and the thermomechanical properties of GNP-CNF composite were monitored. Furthermore, we also performed molecular dynamics (MD) simulations to investigate the impact of applying PyPE dispersant on the interfacial interactions between the GNPs and CNF matrix. The application of PyPE significantly enhanced the dispersibility of GNPs within the CNF matrix, resulting in a 15.5 % increase in-plane thermal diffusivity and a 24.5 % enhancement in tensile strength of the composite, demonstrating their potential applications in high power density electrical equipment and electronic devices.

Cellulose nanofiber-based multifunctional films integrated with carbon dots and anthocyanins from Brassica oleracea for active and intelligent food packaging applications

A new generation of carbon dot-based active and intelligent packaging films with UV blocking, antibacterial, and real-time sensing potentials was fabricated using Brassica oleracea (BO) extract. The cellulose nanofiber (CNF) was used to prepare the multifunctional intelligent nanocomposite film integrated with BO anthocyanins (BOA) and BO-biowaste-derived carbon dots (BO-CDs). The incorporation of 1.5 % BO-CD and 6 % BOA in the CNF matrix improved the physicochemical and UV blocking (>189 % increase) properties of the fabricated films. The synthesized BO-CD exhibits high fluorescence, UV absorption, antibacterial and antioxidant functions. It showed strong radical scavenging activity against ABTS (~90 %) and DPPH (~80 %) compared to the neat CNF film. Scanning electron microscopy and X-ray photoelectron spectroscopy (XPS) have shown enhanced compatibility and elemental composition of the BO-CDs/BOA additives in the CNF-polymer matrix. Packaging tests showed that the prepared film worked efficiently and non-destructively and was able to monitor the freshness of minced pork, fish, and shrimp in real-time through a distinct visual change from red to colorless/yellow during storage at 25 °C for 48 h. Active and intelligent films developed based on CNF/BO-CDs/BOA are expected to be applied as multifunctional packaging materials that can indicate quality changes and extend the shelf life of packaged perishable foods.

Electrochemical Oxidation of Pb II Using Carbon Electrodes Doped with Nanocellulose-FeOx

With TEMPO oxidation, it was possible to incorporate iron nanostructures into a cellulose nanofiber matrix. FTIR spectra showed the functional groups present in the films. The combination of both iron and CNF confers to the films good electrochemical activity; the electrochemical characterization (CV) showed that they present stability in the reduction process at a potential of 0–1 V, with the materials with 5% and 10% being the most active. The Pb reduction process shows that the 5% film is the material with the highest oxidizing capacity.

Understanding the role of TEMPO-oxidized cellulose nanofiber on natural rubber latex nanocomposites

Cellulose nanofibers (CNF) were isolated from raw cotton fibers via 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation process. The isolated CNF were morphologically characterized using Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). Entangled fibrous morphology with diameter in nano regime (15–20 nm) has been observed for the isolated nanofibers. X-ray diffraction (XRD) analysis confirms the high crystallinity of the isolated CNF. Further, the isolated CNF was used to reinforce natural rubber (NR) latex films. The crystallographic, morphological, and spectroscopic analysis of the NR/CNF nanocomposites was carried out. A strong interaction between the CNF and NR matrix has been identified and which reflects in the thermal stability and swelling behavior of NR/CNF nanocomposite films in toluene. The uniform dispersion and tangling effect of CNF along with strong NR-CNF interaction restrict the uptake of solvent through NR matrix.

Thermal Diffusion Films with In-Plane Anisotropy by Aligning Carbon Fibers in a Cellulose Nanofiber Matrix.

For highly efficient heat dissipation of thin electronic devices, development of film materials that exhibit high thermal conductivity in the in-plane direction is desired. In particular, it is important to develop thermally conductive films with large in-plane anisotropy to prevent thermal interference between heat sources in close proximity and to cool in other directions by diffusion. In this study, we developed flexible composite films composed of a uniaxially aligned carbon-fiber filler within a cellulose nanofiber matrix through liquid-phase three-dimensional patterning. The film exhibited a high in-plane thermal conductivity anisotropy of 433%, with combined properties of a thermal conductivity of 7.8 W/mK in the aligned direction and a thermal conductivity of 1.8 W/mK in the in-plane orthogonal direction. This remarkable thermal conductivity and in-plane anisotropy showed the ability to significantly cool powder electroluminescent devices formed on the composite film and also to cool two heat sources in close proximity without thermal interference. In addition, the carbon-fiber filler could be extracted from the composite films by heat treatment at 450 °C and reused as a thermally conductive material.

Nanofiltration performance of glutaraldehyde crosslinked graphene oxide-cellulose nanofiber membrane

Cellulose nanofibers have been widely used in membrane fabrication due to their unique structure, hydrophilicity, sustainability, facile surface modification, and low cost. In this study, the efficient combination of the precise molecular sieving characteristics of graphene oxide (GO) and the high permeability of the cellulose nanofibers (CNFs) network is demonstrated. GO nanosheets were incorporated into the CNF matrix using a facile vacuum filtration technique followed by chemical cross-linking. Cross-linking with glutaraldehyde not only resisted membrane swelling but also improved molecular selectivity. The nanofiltration performance of prepared membranes was evaluated in both aqueous and organic solutions. The optimized crosslinked membranes exhibited a pure solvent flux of 13.9 ± 1.9 Lm−2h−1bar−1 and 4.1 ± 0.35 Lm−2h−1bar−1 for water and ethanol respectively, while maintaining a rejection above 90% for Rose Bengal and Brilliant Blue dyes.

Flexible, mechanically robust, multifunctional and sustainable cellulose/graphene nanocomposite films for wearable human-motion monitoring

The recent sensing technology development for flexible electronics has led to applications in intelligent robots, human-machine interfaces and health monitoring. However, it is challenging to combine ultra-light weight, high durability and flexibility, rapid response and simple fabrication within a single sensor. We herein report a cost-effective, sustainable preparation route for such a sensor, through (i) self-assembling cellulose nanofibers (CNFs) and graphene nanoplatelets modified by Triton X-100 (X-100-GNPs) and (ii) simply filtrating the mixture. X-100-GNPs were found to relatively uniformly disperse in the CNF matrix due to strong interfacial interactions. A nanocomposite film containing 23.76 vol% of GNPs displayed an electrical conductivity of 9.67 S/cm with mechanical robustness – Young's modulus of 6.18 GPa and tensile strength of 173 MPa. The efficient conductive GNP network provided the nanocomposite film sensors with integration of rapid response (61 ms under 1.5 KPa) and high flexibility, sensitivity and durability over 10,000 loading and unloading cycles at 1 Hz with 0–0.5% tensile strain. Used as a wearable strain sensor, the film demonstrated remarkable sensing capabilities in physiological signals, voice recognition, repression changes, muscle contraction and joint bending.

Novel CNFs-based organic UV-adsorber intercalated ZnAl-LDHs composited films with superior photothermal stability and mechanical properties

The improvement of the photothermal stability and mechanical properties for cellulose nanofibers (CNFs) is a highly desirable yet challenging research topic due to its wide applications. Featuring the 2D-organized structure and various characteristics, layered double hydroxides (LDHs) shows tremendous potential in improving the photothermal stability and mechanical properties of CNFs matrix. Herein, a series of ZnAl-LDHs nanosheets intercalated with different organic molecules were synthesized and subsequently doped into CNFs matrix for preparing CNFs/LDHs composited films. It was showed that doping UV-adsorber intercalated ZnAl-LDHs into the CNFs matrix can significantly enhance UV-shielding ability of CNFs/LDHs composited films due to the synergistic effect between organic anions and the interaction between organic anions and metal cations in LDHs laminates. And the CNFs/HUL (HUL = HALS/UV-P-LDHs) composited film exhibited outstanding UV-shielding ability (UV-shielding rate > 60%) among the considered films, which is comparable to that of the reported materials. Compared with the pristine CNFs film, compositing with HUL rendered the increasing of tensile strength from 80 to 110 MPa. The superior photothermal stability and mechanical properties of CNFs/HUL composited film highlight its great application potential in the fields of coating and packaging.

Cellulose Nanofibers/Polycarbonate Nanocomposite

In this study, cellulose nanofiber (CNF) was prepared from carrot residues and further surface modification was carried out using suspension polymerization. Subsequently, these CNFs were added to polycarbonate (PC) to prepare a series CNF reinforced nanocomposites. TEM results show that the average diameter of the fiber after 2,2,6,6-Tetramethylpiperidinyloxy (TEMPO) radical oxidation is 4.46 nm, and the average diameter of the TEMPO oxidized nanofiber modified by suspension polymerization is 7.65 nm, which confirms that the carrot fiber has been successfully prepared into nanoscale. The results of FT-IR analysis show that the lignin and impurities on carrot fibers can be removed effectively after alkali treatment. In addition, the absorption peak of the functional group analyzed by FT-IR also confirmed that the TEMPO radical oxidation and suspension polymerization method were successfully carried out. Contact angle analysis results show that the contact angle of the CNF modified by suspension polymerization method was increased, indicating that the hydrophobicity of the fiber has been significantly improved. Moreover, this will lead to the better compatibility between CNF and PC matrix. Mechanical property analysis also shows that the surface modified CNF has a stronger reinforcing effect on PC than the unmodified one. Furthermore, the results show that the dispersion of CNF in the matrix of nanocomposite prepared by dilution of masterbatch was better than that of the one prepared by directly adding of CNFs. The better dispersion of CNFs in the PC matrix led to the better mechanical properties. The increment of tensile strength of the nanocomposite prepared by dilution of masterbatch can reach to 21.75%. In the analysis of transparency, the transmittance of modified CNF containing nanocomposite was larger than that of unmodified CNF containing one. The transmittance of the nanocomposites containing modified CNFs was larger than 70%, which was close to that of pure PC.

Rheological properties of cellulose nanofiber hydrogel for high-fidelity 3D printing

Optimization of the rheological properties of the matrix is ​​critical for high-fidelity matrix-assisted 3D printing (MAP), which enables the free-form fabrication of fluidic soft materials. This report describes the generic criteria observable in the printing process of cellulose nanofiber (CNF) hydrogels: the sharpness of an angled line, the cross-sectional ratio of a feature, the surface roughness of features, and the completeness of multi-line writing. The concentration and physical properties of the CNF affects the printing fidelity by changing the values of the four criteria, which are closely related to the rheological properties of the matrix. The printing fidelity can be enhanced by the optimal combination of the inks and the CNF matrix. Hydrophilic and hydrophobic inks are printed in the CNF matrix demonstrating as a universal matrix for free-form fabrication with liquid inks.

Fabrication of cellulose nanofiber-based functional color indicator film incorporated with shikonin extracted from Lithospermum erythrorhizon root

Cellulose nanofiber (CNF)-based functional films were prepared by adding shikonin extracted from dried roots of gromwell (Lithospermum erythrorhizon) using a solution casting method. The shikonin added CNF film showed distinctive color changes depending on the pH in the range of 2–12. The shikonin was evenly dispersed in the CNF matrix to form a compatible red colored film. The addition of shikonin (10%) improved the mechanical properties of the CNF film without significantly affecting the crystal structure, water vapor barrier, and thermal stability properties of the film. The CNF/shikonin composite film showed remarkable ultraviolet blocking properties without much-sacrificing transparency. Besides, the composite film showed potent antimicrobial and antioxidant activities. The CNF-based color indicator films with improved physical and functional properties have a high potential for active and intelligent food packaging applications.

New liquid-free proton conductive nanocomposite based on imidazole-functionalized cellulose nanofibers

The first successful attempt to synthesize a new proton conducting polymeric nanocomposite film based on pure cellulose nanofibers (CNF) as a polymer matrix functionalized on their surface with imidazole molecules (Im) as a dopant, was made. The 2CNF-Im nanomaterial contains on average one molecule of imidazole per 2 glucose units from cellulose chains. Water evaporation and thermal stability of 2CNF-Im were studied by thermogravimetric analysis (TGA and DTG) and differential scanning calorimetry (DSC). The temperature dependence of electrical conductivity was studied by the impedance spectroscopy. At 140 °C, the 2CNF-Im nanocomposite has a maximum conductivity of 7.0 × 10−3 S/m, i.e. four orders of magnitude higher than that of non-functionalized CNF matrix. The newly synthesized cellulose nanocomposite exhibits high electrical and thermal stability. In 2CNF-Im, the activation energy of the proton transport process is the lowest compared to the previously synthesized imidazole-functionalized composites based on other pure cellulose materials and equals 0.62 eV. The synthesized nanomaterial is liquid-free solid polymer electrolyte showing proton conductivity above the boiling point of water.

Recyclable nanocellulose-confined palladium nanoparticles with enhanced room-temperature catalytic activity and chemoselectivity

We describe the synthesis of even-dispersed palladium nanoparticles (Pd NPs) confined within a cellulose nanofiber (CNF) matrix for developing a high-performance and recyclable catalyst. The CNF matrix was composed of CNF-assembled mesoporous nanosheets and appeared as soft and hydrophilic foam. Ultrafine Pd NPs (∼6 nm) with high-loading (9.6 wt%) were in situ grown on these mesoporous nanosheets, and their dense spatial distributions were likely to generate nano-confinement catalytic effects on the reactants. Consequently, the CNF-confined Pd NPs (CNF-Pd) exhibited an enhanced room-temperature catalytic activity on the model reaction of 4-nitrophenol hydrogenation with a highest rate constant of 8.8×10−3 s−1 and turnover frequency of 2640 h The CNF Pd catalyst possessed good chemical stability and recyclability in aqueous media which could be reused for at least six cycles without losing activity. Moreover, chemoselective reduction of 3 nitrostyrene was achieved with high yield (80%–98%) of 3-aminostyrene in alcohol/water cosolvent. Overall, this work demonstrates a positive nanoconfinement effect of CNFs for developing stable and recyclable metal NP catalysts.

One-step scalable preparation of graphene nanosheets and high-thermal-conductivity flexible graphene films

It is well known that graphene nanosheets (GNSs) have many excellent properties. However, it has been a difficult thing to exfoliate graphite into GNSs in a controllable and scalable manner. In this research, a new strategy named xylitol-assisted ball milling exfoliation (XABME) was developed for the scalable preparation of GNSs. The experimental results characterized by a series of measurements showed that GNSs were successfully exfoliated by the XABME strategy. The structure of the prepared nanosheets was featured by large lateral size and ultra-small thickness. Furthermore, the prepared GNSs easily achieved high production yield (≈54%). Lastly, the as-obtained GNSs and cellulose nanofibers (CNF) were compounded to form some nanomaterial films. The prepared films exhibited excellent flexibility and higher thermal conductivity, with the in-plane thermal conductivity of 90 wt% GNS film (8.0 W/(m·K)) being 11.4 times higher than that of the film without GNSs. This shows that GNSs could effectively enhance the thermal conductivity of the CNF matrix and indicate that these prepared films have great potentials in the thermal management of portable mobile devices.

Unravelling the Swelling Behaviour and Antibacterial Activity of Palm Cellulose Nanofiber-based Metallic Nanocomposites

The development of functional antimicrobial metal oxide nanocomposite systems based on nanocellulose has been the subject of extensive research in recent years. In addition to its sustainability, biodegradability and non-toxic properties, nanocelullose present an extremely high surface area favoring the selective growth and immobilization of ultrafine metal oxide nanoparticles on the cellulosic surface. In this study, oil palm biomass-derived cellulose nanofiber (CNF) decorated with zinc oxide (ZnO) nanocomposites were produced via ultrasound-assisted in situ co-precipitation approach. The morphology and chemical composition of the as-synthesized ZnO/CNF composites were characterized using field emission scanning electron microscopy (FE-SEM) and Fourier-transform infrared (FT-IR). FE-SEM images revealed the fibrous morphology of nanocomposites with a good distribution of ZnO NPs. The FT-IR analysis confirmed a strong interaction between surface functional groups of CNF and ZnO nanoparticles. The swelling behavior of composites was found to be improved with addition of ZnO nanoparticles in the CNF matrix. The hybrid ZnO-CNF exhibited pronounced antibacterial properties against methicillin-resistant Staphylococcus aureus (MRSA). The findings of present study support the possibility of using this palm CNF-based metallic nanocomposites as nanofillers for wound care application.

Modulating sustained drug release from nanocellulose hydrogel by adjusting the inner geometry of implantable capsules

Nanocellulose hydrogel has been shown to be an excellent platform for drug delivery and it has been lately studied as an injectable drug carrier. 3D printing is an effective method for fast prototyping of pharmaceutical devices with unique shape and cavities enabling new types of controlled release. In this study, we combined the versatility of 3D printing capsules with controlled geometry and the drug release properties of nanocellulose hydrogel to accurately modulate its drug release properties. We first manufactured non-active capsules via 3D printing from biocompatible poly(lactic acid) (PLA) that limit the direction of drug diffusion. As a novel method, the capsules were filled with a drug dispersion composed of model compounds and anionic cellulose nanofiber (CNF) hydrogel. The main benefit of this device is that the release of any CNF-compatible drug can be modulated simply by modulating the inner geometry of the PLA capsule. In the study we optimized the size and shape of the capsules inner cavity and performed drug release tests with common beta blockers metoprolol and nadolol as the model compounds. The results demonstrate that the sustained release profiles provided by the CNF matrix can be accurately modulated via adjusting the geometry of the 3D printed PLA capsule, resulting in adjustable sustained release for the model compounds.

Incorporation of melanin nanoparticles improves UV-shielding, mechanical and antioxidant properties of cellulose nanofiber based nanocomposite films

The featured work reports the preparation, characterization and various properties of melanin nanoparticle (MNP) reinforced cellulose nanofiber (CNF) based nanocomposite films. The CNF was extracted using a combination of chemical and physical methods. The MNP was isolated from a natural source sepia ink by following a simple centrifugation technique and used as a functional nanofiller to fabricate the CNF/MNP nanocomposite films. The prepared nanocomposite films were characterized in terms of morphology, structure, chemical interactions, optical properties, surface hydrophobicity, mechanical properties, thermal stability and antioxidant activity. The MNP was shown to be evenly dispersed in the CNF matrix and biocompatible with cellulose matrix to form the nanocomposite films. Incorporation of MNP enhanced the ultraviolet blocking, mechanical properties, hydrophobicity and water vapor barrier properties of the nanocomposite films. The developed nanocomposite films also showed strong antioxidant activity. The crystalline structure, crystallinity and thermal stability of the nanocomposite films were not affected meaningfully. The sepia ink isolated MNP has a very good prospective to be used as a nanofiller for the preparation of CNF based nanocomposite films.

Nanoporous cellulose paper-based SERS platform for multiplex detection of hazardous pesticides

In this study, a nanoporous cellulose paper-based SERS platform was developed to analyze multiplex hazardous pesticides including thiram (T1), tricyclazole (T2), and carbaryl (C) by surface enhanced Raman scattering (SERS). Gold nanorods (AuNRs) with different aspect ratios were synthesized and compared to achieve the highest SERS signals on paper-based SERS substrates. The advantage of the nanoporous cellulose nanofiber (CNF) matrix with nanoscale surface roughness is that it allows actual nanofiltration, resulting in a uniform and well-controlled AuNR distribution on the top portion of the CNF matrix. The as-prepared CNF–AuNR-based SERS platform exhibited an enhancement factor of 1.4 × 107 as well as the ability to simultaneously detect T1, T2, and C at concentrations as low as 1 nM, 100 nM, and 1 μM, respectively. In addition to analyzing triplex pesticide mixtures in solution, the SERS platform allows for a paper-based SERS swab for rapid trace detection on real-world surfaces. The detection limits for T1, T2, and C residues in apple peels were 6, 60, and 600 ng cm−2, respectively, which are much lower than the maximum residue level requirement for apple peels (2000 ng cm−2). These results demonstrate that the low-cost, flexible, lightweight, paper-based SERS platform shows powerful potential for high SERS performance and on-site SERS analysis.

Preparation and characterization of starch composites with cellulose nanofibers obtained by plasma treatment and ultrasonication

AbstractThe cellulose nanofibers (CNF) are novelly extracted via air plasma treatment combined with the ultrasonication procedure. This study prepares and characterizes the starch‐based biocomposites reinforced by CNF within the glycerol plasticized matrix. The application of starch‐based polymers is improved with fabricating a biocomposite of thermoplastic starch (TPS) as matrix and the CNF as reinforcement. After modifying the surface of the cellulose fibers (CF) by air plasma treatment, CNFs are extracted by using an ultrasonic bath. The CNF are studied using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. The TPS/CNF composites are prepared using the high‐friction and hot‐compression procedure. Tensile test results and SEM images of the fracture surfaces show significant improvement of adhesion between CNF and TPS matrix compared to composites reinforced by neat CF. The thermogravimetric analysis shows a considerable decompositionat approximately 270–340°C.