A Glassy Carbon Electrode Modified with Cellulose Nanofibrils from Ammophila arenaria for the Sensitive Detection of L-Trytophan

L-tryptophan is an essential amino acid for human health. Nanofibrillated cellulose (NFC) from marram grass (Ammophila arenaria) extracted from plants harvested in the center of Tunisia was used for the first time for the modification of a glassy carbon electrode (GCE), for the sensitive detection of L-tryptophan (Trp). After spectroscopic and morphological characterization of the extracted NFC, the GC electrode modification was monitored through cyclic voltammetry. The NFC-modified electrode exhibited good analytical performance in detecting Trp with a wide linear range between 7.5 × 10−4 mM and 10−2 mM, a detection limit of 0.2 µM, and a high sensitivity of 140.0 µA∙mM−1. Additionally, the NFC/GCE showed a good reproducibility, good selectivity versus other amino acids, uric acid, ascorbic acid, and good applicability to the detection of Trp in urine samples.

Ultrathin and Flexible CNTs/MXene/Cellulose Nanofibrils Composite Paper for Electromagnetic Interference Shielding

As the rapid development of portable and wearable devices,different electromagnetic interference(EMI)shielding materials with high efficiency have been desired to eliminate the resulting radiation pollution.However,limited EMI shielding materials are successfully used in practical applications,due to the heavy thickness and absence of sufficient strength or flexibility.Herein,an ultrathin and flexible carbon nanotubes/MXene/cellulose nanofibrils composite paper with gradient and sandwich structure is constructed for EMI shielding application via a facile alternating vacuum-assisted filtration process.The composite paper exhibits outstanding mechanical properties with a tensile strength of 97.9±5.0 MPa and a fracture strain of 4.6±0.2%.Particularly,the paper shows a high electrical conductivity of 2506.6 S m?1 and EMI shielding effectiveness(EMI SE)of 38.4 dB due to the sandwich structure in improving EMI SE,and the gradient structure on regulating the contributions from reflection and absorption.This strategy is of great significance in fabricating ultrathin and flexible composite paper for highly efficient EMI shielding performance and in broadening the practical applications of MXene-based composite materials.

Morphological, Mechanical and Thermal Properties of Poly(lactic acid)(PLA)/Cellulose Nanofibrils(CNF) Composites Nanofiber for Tissue Engineering

Composite nanofiber membranes based on biodegradable poly(lactic acid)(PLA) and cellulose nanofibrils(CNF) were produced via electrospinning. The influence of CNF content on the morphology, thermal properties, and mechanical properties of PLA/CNF composite nanofiber membranes were characterized by field scanning electron microscopy(FE-SEM), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), and dynamic mechanical analysis(DMA), respectively. The results show that the PLA/CNF composite nanofibers with smooth, free-bead surface can be successfully fabricated with various CNF contents. The introduction of CNF is an effective approach to improve the crystalline ability, thermal stability and mechanical properties for PLA/CNF composite fibers. The Young's moduli and tensile strength of the PLA/CNF composite nanofiber reach 106.6 MPa and 2.7 MPa when the CNF content is 3%, respectively, which are one times higher and 1.5 times than those of pure PLA nanofiber. Additionally, the water contact angle of PLA/CNF composite nanofiber membranes decreases with the increase of the CNF loading, resulting in the enhancement of their hydrophilicity.

Sol-Gel Template Synthesis and Photocatalytic Activity of TiO_2 Nanofibrils Loaded on Al_2O_3 Template

TiO2 nanofibrils were prepared within the pores of alumina template membrane by use of sol-gel chemistry. The TiO2 nanofibrils have good crystallinity and size. There is agglomeration free among the particulates of TiO2 and the fibrils show high catalytic activity.

Water-Based Processing of Fiberboard of Acrylic Resin Composites Reinforced With Cellulose Wood Pulp and Cellulose Nanofibrils

Despite the great potential of cellulose wood pulp and cellulose nanofibrils as reinforcing filler in thermoplastics,its use is limited due to its tendency to form agglomerates and due to its high hydrophilic character.Here we describe fiberboard composites with high contents of wood pulp or cellulose nanofibrils,and a resin of poly(styrene-methyl-methacrylate-acrylic acid)used as water-based emulsion.Cellulose wood pulp and cellulose nanofibrils were used directly in the form of water suspensions.The method is based on the flocculation of the polymer emulsion followed by agglomeration of a mixture of the polymer emulsion and cellulose suspension,leading to the co-precipitation of the composite material,which can be easily separated from the water phase.Composites with acrylic polymer/cellulose fibers in the proportions of 75:25,50:50 and 25:75 wt%were prepared.Composites were characterized by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),thermogravimetric analysis(TGA),dynamic mechanical analysis(DMA)and water absorption tests.SEM analysis revealed a very good dispersion of the fibers without evidence of agglomeration,which led to superior mechanical properties.These results showed the effectiveness of the methodology and the potential of cellulose wood pulp and CNF as reinforcement fillers in fiberboard composites and any other high fiber-content materials.

Simultaneous Extraction of Carboxylated Celulose Nanocrystals and Nanofibrils via Citric Acid Hydrolysis--A Sustainable Route

In this study, cellulose nanocrystals(CNC) with surface carboxylic groups were prepared from bleached softwood pulp by hydrolysis with concentrated citric acid at concentrations of 60 wt%~80 wt%. The solid residues from acid hydrolysis were collected for producing cellulose nanofibrils(CNF) via post high-pressure homogenization. Citric acid could be easily recovered after hydrolysis reactions through crystallization due to its low water solubility or through precipitation as a calcium salt followed by acidification. Several important properties of CNC and CNF, such as dimension, crystallinity, surface chemistry, thermal stability, were evaluated. Results showed that the obtained CNC and CNF surfaces contained carboxylic acid groups that facilitated functionalization and dispersion in aqueous processing. The recyclability of citric acid and the carboxylated CNC/CNF give the renewable cellulose nanomaterial huge potential for a wide range of industrial applications. Furthermore, the resultant CNC and CNF were used as reinforcing agents to make sodium carboxymethyl cellulose(CMC) films. Both CNC and CNF showed reinforcing effects in CMC composite films. The tensile strength of CMC films increased by 54.3% and 85.7% with 10 wt% inclusion of CNC and CNF, respectively. This study provides detailed information on carboxylated nanocellulose prepared by critic acid hydrolysis; a sustainable approach for the preparation of CNC/CNF is of significant importance for their various uses.

An Alternative Strategy to Obtain Cellulose Nanofibrils from Parenchyma Cellulose of Bagasse Pith and the Performance of Its Nanopaper

Cellulose nanofibrils(CNFs)were obtained through one-step mechano-partial dissolution by ball milling in N,N-dimethyl acetamide with a low concentration of LiCl from agricultural waste bagasse pith(BP).Compared with fibrous cellulose,parenchyma cellulose(PC)is less uniform in diameter and less aligned,causing PC to dissociate into CNFs during this process without pretreatment.The results showed that the CNFs prepared from PC of BP had a diameter of 30-200 nm and a length of several micrometers.The as-obtained CNFs,along with dissolved cellulose,formed a wet-stable and highly transparent nanopaper in a sorbitol aqueous solution bath,which exhibited a high strain of 101%and a low Young's modulus of 4.3 MPa owing to the addition of the plasticizer sorbitol.This type of nanopaper with favorable transparency,high tensile property,and low Young's modulus has great potential for use as electronic skin and medical dressing material.

Injectable self-healing nanocellulose hydrogels crosslinked by aluminum:Cellulose nanocrystals vs.cellulose nanofibrils

With excellent biocompatibility and unique physiochemical properties,nanocelluloses including cellulose nanocrystals(CNCs)and cellulose nanofibrils(CNFs)are promising candidates for preparing biomedical hydrogels.CNCs and CNFs are different in morphology and surface charges.Herein,CNCs and two CNFs(CNFs-C,Carboxylated CNFs;CNFs-P,Phosphorylated CNFs)were synthesized and applied to fabricate hydrogels through metal crosslinking.Aluminum crosslinking was found to be the best choice for enhancing the strength.This study systematically compared the morphologies,storage modulus,loss factor,continuous shear ramp,self-healing,swelling,in vitro degradation and injectable properties of the fabricated hydrogels,Further,a radar chart is summarized as guidelines to direct the rational selection to meet the specific requirements of further biomedical applications.At the same nanocellulose concentration and after Al^(3+)crosslinking,CNCs hydrogels had strong water holding capacity twice as much as that of CNFs hydrogels.While CNFs hydrogels showed higher hardness and stronger resistance to degradation than that of CNCs.These results provide detailed insights into nanocellulose hydrogels,making it possible to use these guidelines to select hydrogels for desired performance.

N,P co-doped porous graphene with high electrochemical properties obtained via the laser induction of cellulose nanofibrils

Cellulose and its derivatives are natural materials with high carbon contents, but it is challenging to convert their carbon into high value-added carbonaceous materials(e.g., graphene). Here, an approach to convert the carbon in cellulose into N, P co-doped porous graphene(LIG) materials via laser induction is proposed. Cellulose nanofibrils(CNFs), a cellulose derivative with high dispersion uniformity and abundant surface hydroxyl groups, were easily formed on a bulk substrate(thickness ≥5 mm) containing ammonium polyphosphate(APP). Then, a 10.6 μm CO2 laser was used to scribe for 1–5 passes on the CNFs/APP substrate under an ambient environment to produce N, P co-doped porous LIG. Upon increasing the number of laser scribing passes, the IG/IDof LIG first increased and then decreased, reaching a maximum of 1.68 at 4 passes. The good pore structure and low resistance also showed that 4 laser passes were ideal. Besides, the N, P co-doped LIG also showed excellent electrochemical performance, with a specific capacitance of 221.4 FF·g^(-1) and capacitance retention of 89.9%. This method exploits the advantages of nanocellulose and overcomes the difficulties associated with directly compounding cellulosic materials, providing a method for the further development of biomass nanomaterials.

Dispersive Ability of Carboxylated Cellulose Nanofibrils for Aqueous Monolayer Montmorillonite Dispersion:Influence of Na^(+) and Ca^(2+) Concentrations

Carboxylated cellulose nanofibrils(CNFs)have emerged as effective green dispersants for monolayer montmorillonite(MMT)dispersions.However,their dispersion capability is sensitive to the metal ion concentration in aqueous solutions.Hence,this study investigated the effects of Na^(+) and Ca^(2+) concentrations on the dispersive ability of carboxylated CNFs for monolayer MMTs in water.Quartz crystal microbalance with dissipation monitoring(QCM-D)and atomic force microscopy(AFM)were utilized to explore the interfacial interactions between the carboxylated CNFs and monolayer MMTs under different Na^(+) and Ca^(2+) concentrations.When the concentration of Na^(+) reached 0.1 mmol/L,the adhesion mass of carboxylated CNFs on MMT-coated wafer peaked at 24.47 mg/m^(2),higher than control sample(carboxylated CNF-dispersed monolayer MMT dispersion without metal ions,16.03 mg/m^(2)).Moreover,the electrostatic shielding effect promoted a better dispersion of monolayer MMTs by carboxylated CNF dispersant.With a further increase in the Na^(+) concentration,the surface charge of CNFs and MMTs would be reversed resulting from the improved electrostatic shielding effect,which weaken the dispersive ability of carboxylated CNFs.The addition of Ca^(2+) reduced the dispersive ability of carboxylated CNFs for monolayer MMTs,because Ca^(2+) required a lower concentration for the onset of charge reversal compared to Na^(+).This study provides interfacial scale insights into the influence of metal ion concentration on carboxylated CNF-dispersed monolayer MMT dispersions.It also provides a strategy to enhance the dispersive ability of carboxylated CNFs for monolayer MMTs.

Preparation of Cellulose Nanofibrils by Multi-Site Regioselective Oxidation

Cellulose nanofibrils(CNFs)are promising sustainable materials that can be applied to nanocomposites,as well as medical and life-sciences devices.However,methods for the preparation of these important materials are energy intensive because heating and mechanical disintegration are required to produce cellulose fibers below 100 nm in size.In this study,CNFs were prepared through the multi-site regioselective oxidation of cellulose with 2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO)and periodate at room temperature(20–25°C),without any mechanical-disintegration treatment.Transmission electron microscopy(TEM)revealed that the CNFs had the average widths of 14.1,55.4,and 81.9 nm for three different treatments.Fourier-transform infrared spectroscopy revealed that carboxyl groups were created on the surfaces of the microfibrils,while X-ray diffraction studies showed that the cellulose I structure was maintained after oxidation,and that the cellulose nanofibril crystallinity index exceeded 70%.These results demonstrate that CNFs can be prepared by multi-site regioselective oxidation at room temperature in the absence of mechanical disintegration.In addition,a model was developed to calculate the total content of carboxylate and aldehyde groups of CNFs prepared by the TEMPO mediate oxidation,the periodate oxidation,and the multi-site regioselective oxidation methods based on the particle width determined by TEM.The calculated values of the model were in good agreement with the total content(experimental value)of carboxylate and aldehyde groups of CNFs prepared by the TEMPO-mediated oxidation and the multi-site regioselective oxidation methods.However,the model was not valid for CNFs prepared by the periodate oxidation method.

Okara Cellulose Nanofibrils Produced by Pretreatment with Sustainable Deep Eutectic Solvent Coupled with Various Mechanical Treatments

In this study,a green,environmentally friendly method for rapid cellulose nanofribril(CNF)preparation with a significant cost advantage was developed.Pretreatment with a deep eutectic solvent(DES)synthesized from oxalic acid dihydrate and choline chloride(ChCl-O)was combined with various mechanical treatment methods to produce okara CNFs from agricultural waste,with different diameter distributions.The results showed that high-speed stirring produced CNFs with an average diameter of 27 nm.This method was advantageous because it consumed about 94%less energy than traditional high-pressure homogenization method.The DES recovery rate was more than 90%,and DES served as a highly effective treatment,indicating that DES pretreatment is an economical,convenient,and effective strategy for okara CNF preparation.

Preparation and characteristics of TEMPO-oxidized cellulose nanofibrils from bamboo pulp and their oxygen-barrier application in PLA films

Bleached bamboo kraft pulp was pretreated by 2,2,6,6-tetramethylpiperidine-l-oxy radical （TEMPO）- mediated oxidation using a TEMPO/NaBr/NaC10 system at pH = 10 in water to facilitate mechanical disintegration into TEMPO-oxidized cellulose nanofibrils （TO-CNs）. A series of TO-CNs with different carboxylate contents were obtained by varying amounts of added NaC10. An increase in carboxylate contents results in aqueous TO-CN dispersions with higher yield, zeta potential values, and optical transparency. When carboxylate groups are introduced, the DPv value of the TO-CNs remarkably decreases and then levels off. And the presence of hemicellulose in the pulp is favorable to TEMPO oxidization. After the oxidization, the native cellulose I crystalline structure and crystal size of bamboo pulp are almost maintained. TEM micrographs revealed that the degree of nanofibrillation is directly proportional to the carboxylate contents. With increasing carboxylate con- tents, the free-standing TO-CN films becomes more transparent and mechanically stronger. The oxygen permeability of PLA films drastically decreases from 355 for neat PLA to 8.4 mL-1 m a. d-1 after coating a thin layer of TO-CN with a carboxylate content of 1.8 mmol.g1. Therefore, inexpensive and abundant bamboo pulp would be a promising starting material to isolate cellulose nanfibrils for oxygen-barrier applications.

Utilization of discarded crop straw to produce cellulose nanofibrils and their assemblies

A tremendous amount of wheat straw(WS)has been generated by wheat crops every year,while only a small percentage is being used in applications,and most get burned on the field,causing a large amount of the exhaust gas that pollutes the environment.Herein,we report on the extraction of cellulose nanofibrils(CNF)from the alkali treated WS by a combination of 2,2,6,6-tetramethylpyperidine-1-oxyl(TEMPO)-oxidation and mechanical disintegration method.The crystalline structures,thermal properties,natural charge of the CNF were examined.The re-sultant nano-building blocks of the CNF was assembled into macroscopic cellulose materials,i.e.,film,aerogel,and filament in this work.Furthermore,the morphologies and microstructues as well as other properties of these three kinds of the CNF assemblies were investigated.The ob-tained CNF and its assemblies showed a potential application in new materials areas.This work explored a new way to utilize the discarded WS instead of being burned.

Intrinsically ionic conductive nanofibrils for ultra-thin bio-memristor with low operating voltage

Memristors integrated with low operating voltage,good stability,and environmental benignity play an important role in data storage and logical circuit technology,but their fabrication still faces challenges.This study reports an ultra-thin bio-memristor based on pristine environmentfriendly silk nanofibrils(SNFs).The intrinsic ionic conductivity,combined with high dielectric performance and nanoscale thickness,lowers the operation voltage down to0.1-0.2 V,and enables stable switching and retention time over 180 times and 10^(5)s,respectively.Furthermore,the SNFbased memristor device in a crossbar array achieves stable memristive performance,and thus realizes the functions of memorizing image and logic operation.By carrying out variable-temperature electrical experiments and Kelvin probe force microscopy,the space charge-limited conduction mechanism is revealed.Integrating with low operating voltage,good stability,and ultra-thin thickness makes the SNF-based memristors excellent candidates in bioelectronics.

In-situ growth of porous Cu_(3)(BTC)_(2) on cellulose nanofibrils for ultra-low dielectric films with high flexibility

The design of flexible polymeric films with internal porous structures has received increasing attention in low dielectric applications.The highly porous metal-organic frameworks(MOFs)of[Cu_(3)(BTC)_(2)]_(n)(BTC=benzene-1,3,5-tricarboxylate)were introduced into aramid nanofibers(ANF)matrix by using carboxylated cellulose nanofibrils(CNF)as carriers to obtain strong,flexible,and ultra-low dielectric films.The well-dispersed“flowers-branch”like CNF@CuBTC through in-situ growth of CuBTC on CNF surface endowed the ANF/CNF@Cu BTC films with excellent thermal stability,mechanical integrity and low dielectric properties.Besides,the flexible dielectric films exhibited superior ultraviolet(UV)resistance,lower coefficient of thermal expansion(4.28×10^(-5)℃^(-1))and increased water contact angle(83.81°).More interestingly,the removal of guest molecules from the ANF/CNF@CuBTC films according to the vacuum heat treatment(VHT)process significantly improved their dielectric response.The specific surface areas of the composite films after VHT increased obviously,and the dielectric constant and dielectric loss tangent decreased to the expected 1.8-2.2 and 0.001-0.03 at 100 MHz,respectively.Consequently,such designable ultra-low dielectric films with high flexibility play an incredible significance in applications of microelectronics under large deformation conditions,especially in flexible/wearable devices at the arrival of 5 G era.

Sustainable preparation and characterization of thermally stable and functional cellulose nanocrystals and nanofibrils via formic acid hydrolysis

In this work,a sustainable method to prepare functional cellulose nanocrystals(CNCs)and cellulose nanofibrils(CNFs)using formic acid(FA)(a recoverable organic acid)was established.After FA hydrolysis,the obtained CNCs could be well dispersed in DMAC.Thus,the CNC products and fibrous cellulosic solid residue(FCSR)in DMAC could be easily separated by a conventional centrifugal process,and the collected FCSR could be further fibrillated to CNFs with relatively low-intensity mechanical fibrillation process.The isolated CNC products showed high crystallinity index(about 75%)and excellent thermal stability(with onset thermal degradation temperature of 325℃).Both the resultant CNCs and CNFs showed better dispersibility in DMSO,DMF and DMAC respectively because of the introduction of ester groups on the surface of the products.The presence of surface ester groups could increase the interface compatibility of nanocelluloses with polymeric matrices and enable their applications in reinforcing polymeric matrix materials(e.g.the composite films like PHVB+CNFs).

Nanofibrils in 3D aligned channel arrays with synergistic effect of Ag/NPs for rapid and highly efficient electric field disinfection

The disinfection of waterborne pathogens from drinking water is extremely important for human health.Although countless efforts have been devoted for drinking water inactivation,challenges still exist in terms of relative high energy consumption and complicated to implement and maintain.Here,silver nanoparticles anchoring wood carbon(Ag NPs/WC)membrane is developed as cost-effective,high flux,scalable filter for highly efficient electric field disinfection of water.Under electric field of 4 V voltage,the designed membrane achieved more than 5 log(99.999%)disinfection performance for different model bacteria,including Escherichia coli(E.coli),Enterococcus faecalis(E.faecalis),Salmonella enterica serovar Typhimirium(S.Typhimurium)and Bacillus subtilis(B.subtilis)with a high flux of 3.8 x 103 L m^(-2)h^(-1),extremely low energy consumption of 2 J L^(-1)m^(-2)and fantastic durability(7 days).The high disinfection performance of Ag NPs/WC membrane is attributed to the synergistic disinfection of carbon nanofibrils,Ag nanoparticles as well as the low tortuous structure of the channels in wood carbon.The Ag NPs/WC membrane presents a promising strategy for point-of-use drinking water electric field disinfection treatment.

Well-designed protein amyloid nanofibrils composites as versatile and sustainable materials for aquatic environment remediation:A review

Amyloid nanofibrils(ANFs)are supramolecular polymers originally classified as pathological markers in various human degenerative diseases.However,in recent years,ANFs have garnered greater interest and are regarded as nature-based sustainable biomaterials in environmental science,material engineering,and nanotechnology.On a laboratory scale,ANFs can be produced from food proteins via protein unfolding,misfolding,and hydrolysis.Furthermore,ANFs have specific structural characteristics such as a high aspect ratio,good rigidity,chemical stability,and a controllable sequence.These properties make them a promising functional material in water decontamination research.As a result,the fabrication and application of ANFs and their composites in water purification have recently gained considerable attention.Despite the large amount of literature in this field,there is a lack of systematic review to assess the gap in using ANFs and their composites to remove contaminants from water.This review discusses significant advancements in design techniques as well as the physicochemical properties of ANFs-based composites.We also emphasize the current progress in using ANFs-based composites to remove inorganic,organic,and biological contaminants.The interaction mechanisms between ANFs-based composites and contaminants are also highlighted.Finally,we illustrate the challenges and opportunities associated with the future preparation and application of ANFs-based composites.We anticipate that this review will shed new light on the future design and use of ANFs-based composites.

Injectable Nanorobot-Hydrogel Superstructure for Hemostasis and Anticancer Therapy of Spinal Metastasis

Surgery remains the standard treatment for spinal metastasis.However,uncontrolled intraoperative bleeding poses a significant challenge for adequate surgical resection and compromises surgical outcomes.In this study,we develop a thrombin(Thr)-loaded nanorobothydrogel hybrid superstructure by incorporating nanorobots into regenerated silk fibroin nanofibril hydrogels.This superstructure with superior thixotropic properties is injected percutaneously and dispersed into the spinal metastasis of hepatocellular carcinoma(HCC)with easy bleeding characteristics,before spinal surgery in a mouse model.Under near-infrared irradiation,the self-motile nanorobots penetrate into the deep spinal tumor,releasing Thr in a controlled manner.Thr-induced thrombosis effectively blocks the tumor vasculature and reduces bleeding,inhibiting tumor growth and postoperative recurrence with Au nanorod-mediated photothermal therapy.Our minimally invasive treatment platform provides a novel preoperative therapeutic strategy for HCC spinal metastasis effectively controlling intraoperative bleeding and tumor growth,with potentially reduced surgical complications and enhanced operative outcomes.