Surface Of Cellulose Nanofibers Research Articles

Zeolitic imidazolate framework-cellulose nanofiber hybrid membrane as Li-Ion battery separator: Basic membrane property and battery performance

Zeolitic imidazolate framework-8 (ZIF8) concept was introduced in the fabrication of li-ion battery (LIB) separator for the first time. The ZIF8 crystals were synthesized on the surface of cellulose nanofibers (CNFs) by mixing 2-methylimidazole (Hmim) with zinc nitrate hexahydrate (Zn) in methanol. ZIF8- or Zn (mim)2-CNF composite membrane was fabricated and the effect of ZIF8 on the pore structure of CNF network was investigated. The pores of the ZIF8-CNF membrane distributed more homogeneously than that of the pure CNF membrane. The porosity increased from 42% (pure CNF membrane) to 55% (composite membrane). The successful synthesis of ZIF8 crystals on CNF surface was confirmed through elemental composition and crystalline structure analysis of the composite. Compared with polymer based separator, the ZIF8-2-CNF membrane exhibited better thermal stability, mechanical property (isotropic vs. anisotropic), thermal expansion behavior (15.53 vs. 178.90 ppm/k), and surface wettability (13.31° vs. 96.18°). The LIB fabricated with ZIF8-CNF membrane had a comparable cycling stability and a better discharge retention stability (88.3% vs 80.2%) in comparison with these of a tri-layer commercial polymer membrane. The environmentally friendly ZIF8-CNF nanocomposite membrane can be considered as a good alternative for manufacturing LIBs.

Thiol-functionalized cellulose nanofiber membranes for the effective adsorption of heavy metal ions in water

This work reports the fabrication of a thiol-functionalized cellulose nanofiber membrane that can effectively adsorb heavy metal ions. Thiol was incorporated onto the surface of cellulose nanofibers, which were fabricated by the deacetylation of electrospun cellulose acetate nanofibers and subsequent esterification of a thiol precursor molecule. Adsorption mechanism was investigated using adsorption isotherms. Adsorption capacity as a function of adsorbate concentration was described well with Langmuir isotherm, suggesting that metal ions form a surface monolayer with a homogenously distributed adsorption energy. Maximum adsorption capacities in the Langmuir isotherm for Cu(II), Cd(II), and Pb(II) ions were 49.0, 45.9, and 22.0 mg·g−1, respectively. The time-dependent adsorption capacities followed a pseudo-second-order kinetic model, suggesting that chemisorption of each doubly charged metal ion occurs with two thiol groups on the surface. These results highlight the significance of surface functionality on biocompatible, nontoxic, and sustainable cellulose materials to expand their potential and applicability towards water remediation applications.

A promising process to modify cellulose nanofibers for carbon dioxide (CO2) adsorption

A novel process of using phthalimide to modify cellulose nanofibers (CNF) for CO2 adsorption was studied. The effectiveness of the modification was confirmed by ATR-IR. Phthalimide incorporation onto CNF was confirmed with the characteristic peaks of NH2, C–N, and ester bonding COO− was observable. The XPS analyses confirmed the presence of N1s peak in Ph-CNF, meaning that the hydroxyl groups reacted with the amino groups (NH2) of phthalimide on the CNF surface. Based on the results, surface modification and addition of phthalimide increased the specific surface area, but also decreased the overall porosity, size of pores and volume of pores. When the temperature, humidity, pressure, and airflow rate increased, the CO2 adsorption significantly increased. The CO2 adsorption of phthalimide-modified CNF was confirmed by ATR-IR spectroscopy as the characteristic peaks of HCO3−,NH3+ and ester bonding NCOO− were visible on the spectra.

Mechanical properties of poly(ε‐caprolactone) composites with electrospun cellulose nanofibers surface modified by 3‐aminopropyltriethoxysilane

ABSTRACTTo enhance the reinforcement effects of regenerated cellulose nanofibers (RC‐NF) in poly(ε‐caprolactone) (PCL), we synthesized RC‐NF‐3‐aminopropyltriethoxysilane (APS), the surface‐modified RC‐NF by APS. The RC‐NF were fabricated by the saponification of electrospun cellulose–acetate nanofibers. The surface modification by APS was confirmed by the X‐ray photoelectron spectroscopy (XPS). To enhance the mechanical property of PCL, the RC‐NF and the RC‐NF‐APS were separately compounded into PCL by compression molding. It was found that, when the fiber concentration of RC‐NF‐APS was 17 wt %, the Young's modulus at room temperature increased from 698.0 to 744.7 MPa, whereas the storage modulus at 55 °C almost increased from 180 to 220 MPa. The micrographs of the fracture surface of the composites revealed that the surface modification prevented the pull‐out of RC‐NF from PCL. It was concluded that the mechanical properties of the composites were enhanced due to the improvement of the compatibility between RC‐NF and PCL by the surface modification with APS. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48599.

Cellulose-Nanofiber-Mediated Sorption-Benefitting Holed Silicalite-1 Crystals.

Silicalite-1-type zeolites with unique intracrystal holes or cracks were successfully prepared using a cellulose nanofiber (CNF) as an additional mediating material, and their vapor phase adsorption properties toward methyl tert-butyl ether (MTBE) and n-nitrosodimethylamine (NDMA) were examined. It was found that the mixing protocol of CNF and structure-directing agents (SDAs), the addition amount of CNF, and the CNF/SDAs amount ratio play important roles in forming the holed silicalite-1. The synthesis route that preliminarily mixes CNF with SDAs in a series of controlled conditions is particularly beneficial for the formation of the holed silicalite-1 with mesoporosity and larger pores because the CNF-SDAs composite structure benefits the zeolite growth closely encompassing CNF inside the crystal structure. It also promotes the preferential formation of the orthorhombic phase vicinal to the CNF surface, namely, the surface of the formed internal holes or cracks, with the twin-type crystal size reduced as compared to the non-CNF-templated sample. On the contrary, the synthesis route that mixes CNF with SDAs–silicate composite ions tends to modify the twin-type crystal shape at the same time to form small but uniform well-crystallized particles with less holes or cracks and a dominative monoclinic phase. It was considered that both the inter-subunit structural defect and silanol defect whose content is increased with CNF addition influence the adsorptivity of MTBE and NDMA. Owing to the small twin-type crystal size, the smaller crystal subunits, and the favored short path from the surface of internal holes or cracks, the holed silicalite-1 derived from the CNF and SDA premixture assures the easiest access of adsorbate molecules to the most energetically favored sites and is most appropriate for the adsorption of both MTBE and NDMA among the examined zeolites.

Antibacterial properties of silver nanoparticles depositions on cellulose nanofibers surfaces using reducing agents

Antibacterial properties of silver nanoparticles depositions on cellulose nanofibers surfaces using reducing agents

Structure retention of proteins interacting electrostatically with TEMPO-oxidized cellulose nanofiber surface

In this study, we evaluated the adsorption of proteins to 2,2,6,6-tetramethylpiperidine-1-oxyl oxidized cellulose nanofibers (TOCNs) and their structures on the TOCN surface. TOCNs derived from bleached pulp are as thin as 4 nm and have a very high specific surface area and a high density of surface carboxyl groups. The adsorption of two model proteins (lysozyme (Lyz) and bovine serum albumin (BSA)), which is driven by electrostatic attraction between the positively charged proteins and the negatively charged TOCN surface bearing ionized carboxyl groups, is demonstrated to occur only at pH values below their isoelectric points. Notably, pristine BSA and Lyz retain their native structures after adsorption onto TOCN, which is ascribed to the very low width of TOCN, and consequently the low area of contact between the protein and cellulose fiber. Thus, this work paves the way to the fabrication of TOCN-based biomaterials with the retention of the structure of the adsorbed proteins.

(Invited) Design of the Separators for Li-Ion and Lithium Metal Batteries

Functionalization of separators is one path to increase the performance of Li-ion (LIB) and lithium metal batteries (LMB). This is a research area within LIBs not very extensively explored. A separator should prevent direct contact between the positive and negative electrodes and provide good ionic transport pathways. Commercial separators are usually made of polyolefin with low thermal stability and low electrolyte wettability. In this study, cellulose of a green algae has been used to make new separator materials via a simple paper making method. The resulting separator material has several advantages compared to commercial separator materials in ionic conductivity, thermal stability, electrolyte wettability and type of pore distribution. With this material as the basis two types of advanced separator functionalities was designed and will be described in the presentation. 1) Redox-active separators based on the use of a redox-active conducting polymer, polypyrrole (PPy) and a natural polymer, polydopamine (PDA) where the PPy-based redox-active separator is designed to contribute capacity to the cathode of a LIB, while the PDA-based redox-active separator is proposed to be used on the anode side. 2) It is known that a homogeneous current distribution is beneficial for the battery performance. Therefore, separators with homogenous pore distributions have been manufactured to study the influence of the pore distribution on the Li deposition/stripping behavior and composite cathode utilization in LMBs. One example is a sandwich-structured separator composed of two cellulose nanofiber (CNF) surface layers and an intermediate glass microfiber (GMF) and then a CNF composite layer on the other side. The CNF surface layers, of the sandwich-separator, have homogeneous distribution of nano-sized pores, which favours a homogeneous current distribution at both electrodes. The intermediate GMF/CNF layer, however, has excellent ionic transport due to a macro porous structure of the material. This separator exhibits a good electrolyte wettability and better thermal stability compared to a classical Celgard separator. The reason for this is the use of the hydrophilic and thermally stable CNFs and GMFs. The combination of nano-sized and micro-sized fibers used in this separator yields a higher ionic conductivity than that for the commercial separator (1.14 vs. 0.49 mS cm−1). The performance is studied for both Li anodes and LiFePO4 composite cathodes and the results show that use of separators with high porosities and homogeneous surface pore distributions can improve the performances (e.g. capacities and stabilities) of LMBs considerably. The presentation will highlight the importance of proper separator/electrode interactions. The present approach constitutes a practical engineering strategy for the production of separators with nano/micro fibers and a promising route for the development of LMBs with improved safety and enhanced electrochemical performances.

Enhancement of the bending strength of I-shaped cross-sectional beam of CFRP by dispersing cellulose nanofibers without hydrophobic treatment on the surface

Many researches on strengthening the matrix of Carbon Fiber Reinforced Plastic (CFRP) using cellulose nanofibers (CNFs) have been reported. However, hydrophobic treatment to modify the surface of CNFs is indispensable. Authors previously showed that the bending properties of CFRP were enhanced by CNF without hydrophobic treatment after the electro-activated deposition resin molding (ERM) method. CNF can be dispersed on the surface of CFRP since the electro-activated deposition solution is water based. In this study, first, it was confirmed that the tensile properties of CFRP could be enhanced by CNF dispersed on the surface after the ERM method. Also, the weight fraction of CNF was optimized to maximize the tensile properties. Second, the I-shaped cross-sectional beam (I-beam) was molded by laminating the CFRP with CNF dispersed on the surface. It was confirmed that the bending properties of the CFRP I-beam was enhanced by CNF, and the effect of CNF on the interlaminar strength was evaluated.

Facile functionalization of cellulose from discarded cigarette butts for the removal of diclofenac from water

In this study, cellulose nanocrystals (CNCs), and cellulose nanofibers (CNFs) were extracted from discarded cigarette butts (DCBs), and investigated for their efficiency for diclofenac (Dfc) removal from water. CNFs extraction process involved cleaving of acetyl group by alkali treatment and etched with phosphate ions (HPO) from phosphoric acid to obtain the variably charged HPO-CNFs. To obtain CNCs, sulfuric acid was used to cleave phenol moieties from CNFs under high temperature and agitation. SEM, FT-IR, SEM-EDS, Raman spectroscopy were used to analyze the physico-chemical properties of synthesized cellulose materials. The SEM images revealed the exfoliated fiber strands of CNFs after extraction procedure, and the difference in the crystal structure of CNCs30 and CNCs60. The EDS analyses revealed the presence of higher amount of carbon in DCBs compared to other forms of synthesized celluloses. The FT-IR analyses revealed functional group shifts and bond reductions after various treatment steps, while the HPO attachment on the CNFs surfaces was confirmed by the presence of PO bonds. Raman analyses revealed clear crystals in the CNCs60 compared to the other celluloses. The adsorption capacity of HPO-CNFs for diclofenac removal was found to be 107.90 mg g−1 and Langmuir model fitted well to the adsorption data.

Stiffened Nanocomposite Hydrogels by Using Modified Cellulose Nanofibers via Plug Flow Reactor Method

Cellulose nanofibers (CNFs), hydrophilic natural nanomaterials, are widely used to reinforce the stiffness of hydrogels, which have wet properties similar to those of human tissues. Interactions between the nanofibers and polymer matrix play an important role in reinforcing hydrogels. Here, we used a CNF cake as a reactor to modify the surface of CNFs, which was based on the principle of a plug flow reactor (PFR), excepting to enhance interfacial interactions. As a result, the degree of substitution of maleic acid monoester-modified CNFs reached 0.14 at room temperature within 25 min. The crystallinity and morphology of modified CNFs were well maintained. The modified CNFs were used to form composites with poly(acrylamide-co-acrylic acid) networks, followed by ionic cross-linking. The elastic modulus of the nanocomposite hydrogels increased considerably from 10.27 ± 0.48 MPa to 24.67 ± 0.53 MPa after the CNF modification process. This PFR method shows great potential for preparing a range of CNF-based fun...

Bio-inspired cellulose nanofiber-reinforced soy protein resin adhesives with dopamine-induced codeposition of “water-resistant” interphases

Poor interface strength and water resistance are significant challenges in taking full advantage of the excellent performances of natural fiber-reinforced biopolymer composites. Herein, a mussel-inspired co-deposition process was developed to synthesize a nanostructured layer on the surface of cellulose nanofiber (CNF) with target water-resistant property and high adhesion strength of soy protein isolate (SPI)/CNF composite adhesives. Renewable resource cardanol was selected as an environmentally sustainable interphase constituent. First, hydrolyzable alkoxy silane cardanol (ASC) was synthesized via an epoxide ring opening reaction of the cardanol-based glycidyl ether with aminopropyltriethoxysilane. When assembled on the CNFs, the ASC/dopamine system conformally coated every fiber, yielding a nanostructured polydopamine (pDA)/ASC hybrid coating that subsequently acted as the resin/fiber interphases during the adhesive preparation. The nanohybrid coatings contained versatile catechol functional groups as “bonding sites” and long aliphatic chains as a “flexible barrier”. The integrated advantages of the CNF network and the “bonding site and flexible barrier” structures on the outside surface contributed to the strong cohesive interaction between the soy protein and nanofibers, and hence the reactive water-resistant barrier was formed between the two substrates. Thanks to the tailored interphase, the resins achieved impressive adhesion properties with a wet shear strength up to 1.27 MPa, which was 189% and 95% higher than that of the neat resin and the adhesive prepared with pristine fibers, respectively. The findings demonstrate that the sustainable cardanol holds potential for the development of water-resistant biobased composites.

UV grafting: surface modification of cellulose nanofibers without the use of organic solvents

Polymers were grafted from the surfaces of cellulose nanofibers by UV irradiation with an organic solvent-free process.

Electrodes based on cellulose nanofibers/carbon nanotubes networks, polyaniline nanowires and carbon cloth for supercapacitors

Supercapacitors (SCs) are promising devices for meeting the future demand of sustainable energy conversion and storage. Here, cellulose nanofibers (CNFs), carbon nanotubes (CNTs), polyaniline (PANI) and carbon cloth (CC) were used to fabricate SCs electrodes. CNFs and CNTs were constructed into networks and served as the skeleton for depositing polyaniline nanowires (PANI-NWs). The vacuum filtration method contributed to the construction of a three-dimensional network structure for CNFs and CNTs. CC was used as a flexible current collector in the electrode. In-situ polymerization was performed to polymerize PANI on the surface of CNFs, CNTs and CC to form a three-dimensional porous film-current collector structure (CCPC electrodes). Electrochemical measurements showed that the CCPC electrode exhibited a low charge transfer resistance of 1.50 Ω, as well as excellent specific capacitance of 318 F g−1 at a scan rate of 10 mA s−1. In addition, it exhibited 72.09% retention of the initial value after 1000 cycles of testing. Overall, this work provides a strategy for the fabrication of a porous network film-soft current collector electrode for supercapacitors.

Silver-Incorporated Nanocellulose Fibers for Antibacterial Hydrogels.

A free-standing, antibacterial hydrogel was fabricated using silver-nanoparticle-immobilized cellulose nanofibers (CNFs) and alginate. Surface hydroxyl groups of CNFs were oxidized to carboxylate groups using (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl (TCNF), followed by the treatment with silver nitrate solution for surface adsorption of silver ions. In situ reduction of silver ions to produce silver nanoparticles was performed for the silver-adsorbed CNFs. Electron microscopy, X-ray diffraction, and spectroscopic analysis revealed that higher amounts of silver nanoparticles were immobilized on the surface of TCNF than on the surface of native CNF. Silver-nanoparticle-immobilized TCNF was embedded in alginate gels and silver ions from the matrix were slowly released for 7 days. Silver-nanoparticle-loaded alginate gels showed comparable antibacterial activity to silver-ions-loaded alginate gels, although the former showed a significantly lower cytotoxicity against animal cells. Thus, the antibacterial gels can potentially be applied to various skin surfaces to prevent bacterial infection while minimizing skin damage.

Tree-like cellulose nanofiber membranes modified by citric acid for heavy metal ion (Cu2+) removal

Eco-friendly tree-like porous carboxyl modified cellulose nanofiber membranes as highly efficient adsorbents for heavy metal ions were fabricated by the electrospinning of cellulose acetate (CA)/tetrabutylammonium chloride (TBAC)/manganese dioxide (MnO2) solution, and subsequent deacetylation treatment to turn CA into cellulose and citric acid modification to graft carboxyl group on the surface of cellulose nanofibers. The addition of TBAC led to the formation of tree-like structure and MnO2 particles were used as pore-forming agents. The effects of pH, initial ion concentrations and contact time on the removal capacity of heavy metal ions were investigated. During the removal process, the abundant carboxyl groups (–COOH) transferred to carboxylate ions (–COO−) which had stronger ion exchange ability to the metal ion adsorption. In addition, the tree-like porous structure supplied large specific surface area and effectively increased the removal capacity. The removal process could reach a plateau in 90 min with the maximum removal amount of 399.14 mg/g. The removal process was also depicted by Langmuir and Freundlich isotherm model. Generally, the tree-like porous structure will have extensive prospects in the fields of filtration, electrochemistry, tissue engineering and so on.

Sandwich-structured nano/micro fiber-based separators for lithium metal batteries

Although the increased need for high-energy/power-density energy storage systems has revived the research on lithium metal batteries (LMBs), the influence of the separator on the performance of LMBs is still generally neglected. In the present study, a sandwich-structured separator (referred to as the CGC separator below) composed of two 2.5 µm thick cellulose nanofiber (CNF) surface layers and an intermediate 15 µm thick glass microfiber (GMF) and CNF composite layer is described. While the CNF surface layers of the CGC separator feature a homogeneous distribution of nano-sized pores favoring the attainment of a homogeneous current distribution at both electrodes, the intermediate GMF/CNF layer contains macropores facilitating the ionic transport through the separator. The CGC separator exhibited a much better electrolyte wettability and thermal stability compared to a Celgard separator, due to the use of the hydrophilic and thermally stable CNFs and GMFs. It is also shown that the combination of nano-sized and micro-sized fibers used in the CGC separator yields a higher ionic conductivity than that for the commercial separator (1.14 vs. 0.49 mS cm−1). Moreover, the influence of the separator pore structure (e.g. the porosity and pore distribution) on the performance of LMBs is studied for both Li anodes and LiFePO4 composite cathodes. The results demonstrate that the use of separators with high porosities and homogeneous surface pore distributions can improve the performances (e.g. capacities and stabilities) of LMBs considerably, and also highlights the importance of proper separator/electrode interactions. The present approach constitutes a practical engineering strategy for the production of separators with nano/micro fibers and a promising route for the development of LMBs with improved safety and enhanced electrochemical performances.

Effect of surface modification on the dispersion, rheological behavior, crystallization kinetics, and foaming ability of polypropylene/cellulose nanofiber nanocomposites

Herein, the issue of dispersing cellulose nanofiber (CNF) in hydrophobic polymer has been solved through the modification of the CNF surface using alkenyl succinic anhydride (ASA). Polypropylene (PP) nanocomposites containing CNF with various degrees of substitution (DS)−ranging from 0 to 0.4−were prepared by melting and blending in an extruder. Fourier transform infrared spectroscopy (FTIR) results illustrated that the ASA chains were successfully incorporated into the CNF, and the FTIR spectroscopic imaging and X-ray computed tomography demonstrated the well-dispersed hydrophobic-modified CNF with the highest DS (=0.4) in the PP matrix. Rheological results revealed that a network-like structure of CNF was generated in the PP/CNF nanocomposites. Compared with isotactic PP, the PP/CNF composites exhibited improved crystallization kinetics, which could be elucidated via fast scanning chip calorimetry (FSC) analysis. Finally, the foaming performance of the prepared composites was examined using an easily scaled foam injection molding technique. The incorporation of CNF remarkably ameliorated the cellular morphologies of PP foams, resulting in a sharp decrease in cell size and a notable enhancement in cell density.

Cell interactions and cytotoxic studies of cellulose nanofibers from Curauá natural fibers

Cellulose nanofibers (CNF) were isolated from Curauá fibers (Ananas erectifolius L. B. Smith) through a mechanical grinder preceded by mild chemical treatment. Morphology and surface characteristics of the fibers were followed until it reaches the nanoscale as long and flexible nanofibers. In aqueous suspensions, SAXS techniques revealed that such nanofibers present a twisted ribbon structure while rheological measurements demonstrate its high viscosity and a thixotropic behavior. These characteristics suggests the potential application of CNF in biomedical field, which, in turn, stimulates the toxicological studies of such materials. The obtained materials do not show any sign of cytotoxicity by direct or indirect assays for cell viability and cell morphology using Vero cells. Moreover, during the adhesion test, the cells demonstrated higher affinity to the CNF surface. It can be related to its surface properties and its obtaining conditions, which did not use any hazardous chemicals.

Rapid Photocatalytic Degradation of Pollutant from Water under UV and Sunlight via Cellulose Nanofiber Aerogel Wrapped by TiO2

Semiconductor photocatalysis can be used to decompose various organic compounds in open air under aqueous conditions with solar energy. A cellulose nanofiber/TiO2 aerogel (CNFT) for rapid photocatalytic degradation of methylene blue (MB) solution was successfully fabricated through a facile hydrothermal method. TiO2 nanoparticles adhered to the surface of cellulose nanofibers as scaffold through a hydrogen bond and were well-distributed. The particle size distribution data showed that the mean diameter of TiO2 nanoparticles was around 6.8 nm. In the system of the as-prepared CNFT, CNF played important roles in adsorption of pollutant and in stopping the electron hole derived from TiO2 from recombining. The composite aerogel exhibited efficient photocatalytic activity in the degradation of pollutant (MB) under ultraviolet light (UV) and sunlight irradiation. The composite aerogel could be regarded as a green and portable photocatalyst, because it was promising for wastewater treatment application as a result of its good high photocatalytic activity and stability under ultraviolet light and sunlight irradiation.