Surface Of Cellulose Nanofibers Research Articles

Study on Synthesis and Photocatalytic Activity of Porous Titania Nanotubes

Using the common natural cellulose substance (filter paper) and triblock copolymer (Pluronic P123) micelles as dual templates, porous titania nanotubes with enhanced photocatalytic activity have been successfully synthesized through sol-gel methods. Firstly, P123 micelles were adsorbed onto the surfaces of cellulose nanofibers of filter paper, followed by hydrolysis and condensation of tetrabutyl titanate around these micelles to form titania layer. After calcination to remove the organic templates, hierarchical titania nanotubes with pores in the walls were obtained. The sample was characterized by X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption/desorption, Fourier Transform Infrared Spectroscopy (FT-IR), Ultraviolet-Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS), and X-ray photoelectron spectroscopy (XPS). As compared with commercial P25 catalyst, the porous titania nanotubes prepared by this method displayed significantly enhanced photocatalytic activity for degrading methyl orange under UV irradiation. Within 10 minutes, the porous titania nanotubes are able to degrade over 70% of the original MO, while the value for the commercial Degussa P25 is only about 33%.

Surface imprinted bacterial cellulose nanofibers for cytochrome c purification

Molecularly imprinted polymers possessing synthetic recognition sites present great potential for various application areas, which require specific recognition of molecules. However various molecularly imprinted polymers (MIPs) reported previously have low affinity capacity and low binding kinetics due to weak interactions between template molecule and functional monomer in aqueous media and also high mass transfer resistance. The synthesis of MIPs onto nanomaterial surface via metal ion coordination interactions serves as an effective solution. In this work, we prepared thin molecularly imprinted polymer layer on bacterial cellulose nanofiber surface using Cu2+ chelating monomer, N-Methacryloyl-(L)-histidinemethylester (MAH) as a functional monomer orienting cytochrome c molecules. The conditions of polymerization and adsorption were optimized to obtain best affinity performance. Due to unique properties of bacterial cellulose nanofibers such as high surface-to-volume ratio and macro-porosity, the resultant cytochrome c imprinted nanofibers (Cyt c-MIP NFs) reducing diffusional resistances could achieve high recognition capacity and excellent binding kinetics. Cyt c-MIP NFs were also successfully applied to capture template proteins from real sample. This novel procedure presents simple, cheap and stable fabrication strategy for efficient separation of proteins.

Fabrication of elastic composite hydrogels using surface‐modified cellulose nanofiber as a multifunctional crosslinker

ABSTRACTWe fabricate composite hydrogels using surface‐modified cellulose nanofiber (CNF) and N‐isopropylacrylamide (NIPAm) as a multifunctional crosslinker and monomer, respectively. We expect to produce unique network structures that lead to elastomeric properties rarely reported for CNF‐based materials. The modification of CNF is performed to introduce polymerizable vinyl groups onto the surface of CNF via condensation between the surface hydroxyl groups and 3‐(trimethoxysilyl)propylmethacrylate. The modification and morphology of the surface‐modified CNF (mCNF) are confirmed by FTIR, solid‐state NMR, and FE‐SEM, respectively. We conduct in situ radical polymerization under various conditions using mixtures of the mCNF aqueous suspension, NIPAm monomer, radical initiator, and catalyst. The mechanical properties of the obtained hydrogels (water content = 90 wt %) are evaluated. The gels can be elastically stretched to more than 700 times their original lengths and exhibit an apparent shape recovery with a small permanent deformation (∼1/5 of the applied deformation under the gravity field). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42906.

Nanostructured biocomposites based on unsaturated polyester resin and a cellulose nanofiber network

Biocomposites reinforced by natural plant fibers tend to be brittle, moisture sensitive and have limited strength. Wood cellulose nanofibers (CNF) were therefore used to reinforce an unsaturated polyester matrix (UP) without the need of coupling agents or CNF surface modification. The nanostructured CNF network reinforcement strongly improves modulus and strength of UP but also ductility and toughness. A template-based prepreg processing approach of industrial potential is adopted, which combines high CNF content (up to 45 vol%) with nanoscale CNF dispersion. The CNF/UP composites are subjected to moisture sorption, dynamic thermal analysis, tensile tests at different humidities, fracture toughness tests and fractography. The glass transition temperature (Tg) increases substantially with CNF content. Modulus and strength of UP increase about 3 times at 45 vol% CNF whereas ductility and apparent fracture toughness are doubled. Tensile properties at high humidity are compared with other biocomposites and interpreted based on differences in molecular interactions at the interface.

Novel nanocomposites based on fatty acid modified cellulose nanofibers/poly(lactic acid): Morphological and physical properties

Abstract A novel poly(lactic acid) (PLA) based nanocomposite, reinforced by cellulose nanofibers (CNFs) was prepared. CNFs were previously treated by oleic acid for improving the compatibility with PLA matrix. Resulted modified nanofibers (MCNFs) exhibited reduced surface polarity in comparison to non-modified CNFs. MCNFs were subsequently introduced into PLA matrix and the effects of the CNFs surface modification on morphological, mechanical, thermal and barrier properties of the PLA based nanocomposites were studied. The morphology of fracture surfaces was evaluated by field emission scanning electron microscopy (FE-SEM). Differential scanning calorimetry (DSC) showed that the melting temperatures of the PLA–MCNF nanocomposites were considerably higher than that of the pure PLA film. The ultimate tensile strength and Young's modulus of nanocomposites (at 12% MCNFs) were about 2.5 and 2 times as much as those of the pure PLA films, respectively. In addition, adding MCNFs caused a decrease in water vapor permeability.

In situ synthesis of conductive polypyrrole on electrospun cellulose nanofibers: scaffold for neural tissue engineering

This study reports the synthesis of conductive polypyrrole (PPy) on electrospun cellulose nanofibers. The cellulose nanofibers were electrospun via cellulose acetate and surface modified using in situ pyrrole polymerization. PPy adhered to the cellulose nanofiber surface as small particles and caused a 105 fold increase in conductivity compared to unmodified cellulose nanofibers. In addition, tests revealed no cytotoxic potential for the PPy coated cellulose nanofiber materials. In vitro culturing using SH-SY5Y human neuroblastoma cells indicated enhanced cell adhesion on the PPy coated cellulose material. SH-SY5Y cell viability was evident up to 15 days of differentiation and cells adhered to the PPy coated cellulose nanofibers and altered their morphology to a more neuron like phenotype.

Enhanced Synthesis of Metal‐Organic Frameworks on the Surface of Electrospun Cellulose Nanofibers

This study reports the in situ crystal growth of HKUST‐1 on electrospun cellulose nanofibers. Two different methods for introducing carboxyl groups on the nanofiber surface were used; HKUST‐1 was then synthesized on the cellulose nanofiber surface using a layer‐by‐layer approach. The distribution of HKUST‐1 on the nanofiber surface was highly dependent on the type of anionic pretreatment. The loading of HKUST‐1 on the nanofiber surface could be controlled by the layer‐by‐layer synthesis and the BET surface area could be increased by a factor of 44 to 440 m2 g−1.

Humic acid adsorption onto cationic cellulose nanofibers for bioinspired removal of copper(II) and a positively charged dye.

Waste pulp residues are herein exploited for the synthesis of a sorbent for humic acid (HA), which is a major water pollutant. Cellulose pulp was etherified with a quaternary ammonium salt in water thereby introducing positive charges onto the surface of the pulp fibers, and subsequently mechanically disintegrated into high surface area cellulose nanofibers (CNF). CNF with three different charge contents were produced and their adsorption capacity towards HA was investigated with UV-spectrophotometry, quartz crystal microbalance with dissipation, and ζ-potential measurements. Substantial coverage of the CNF surface with HA in a wide pH range led to a reversal of the positive ζ-potentials of CNF suspensions. The HA adsorption capacity and the kinetics of HA uptake were found to be promoted by both acidic pH conditions and the surface charge content of CNF. It is suggested that HA adsorption onto CNF depends on electrostatic interactions between the two components, as well as on the conformation of HA. At pH ∼ 6, up to 310 mg g(-1) of HA were adsorbed by the functionalized CNF, a substantially higher capacity than that of previously reported HA sorbents in the literature. It is further shown that CNF-HA complexes could be freeze-dried into "soil-mimicking" porous foams having good capacity to capture Cu(II) ions and positive dyes from contaminated water. Thus, the most abundant natural polymer, i.e., cellulose could effectively bind the most abundant natural organic matter for environmental remediation purpose.

A review: potential usage of cellulose nanofibers (CNF) for enzyme immobilization via covalent interactions.

Nanobiocatalysis is a new frontier of emerging nanosized material support in enzyme immobilization application. This paper is about a comprehensive review on cellulose nanofibers (CNF), including their structure, surface modification, chemical coupling for enzyme immobilization, and potential applications. The CNF surface consists of mainly -OH functional group that can be directly interacted weakly with enzyme, and its binding can be improved by surface modification and interaction of chemical coupling that forms a strong and stable covalent immobilization of enzyme. The knowledge of covalent interaction for enzyme immobilization is important to provide more efficient interaction between CNF support and enzyme molecule. Enzyme immobilization onto CNF is having potential for improving enzymatic performance and production yield, as well as contributing toward green technology and sustainable sources.

Nanographite sheets derived from polyaniline nanocoating of cellulose nanofibers

A simple chemical approach for the fabrication of nanographite sheets has been developed by denitrogenation of polyaniline thin layers deposited as a coating on natural cellulose nanofibers as in ordinary filter paper. The crystalline domains on the cellulose nanofiber surface directed the adsorption and further polymerization of aniline monomers to form well-aligned polyaniline layers. Treatment of the filter paper with the deposited polyaniline with a sodium hydroxide/urea aqueous solution at −20°C resulted in both the removal of the cellulose and the formation of well-structured nanographite sheets.

Immobilization of gelatin on bacterial cellulose nanofibers surface via crosslinking technique

Bacterial cellulose is considered to be a potential material for tissue engineering. However, the absence of enough activity restricts its practical application as tissue engineering scaffold. This paper describes the synthesis of a novel bacterial cellulose/gelatin composite via crosslinking by procyanidin (PA). The morphology of the bacterial cellulose/gelatin composite was observed by field emission scanning electron microscopy (FE-SEM) and transmission electronic microscope (TEM). The composites were further characterized by fourier transformed infrared spectroscopy (FTIR) and X-ray diffraction (XRD). It was found that the 0.25wt.% Gel solution was the appropriate concentration for the BC/Gel composite. Furthermore, the proliferation, infiltration and adhesion of NIH3T3 cells on the BC/Gel-025 composite were evaluated. The results showed that the composite had better bioactivity than pure bacterial cellulose, and the composite supported cell growth.

Ultrafine Polysaccharide Nanofibrous Membranes for Water Purification

Ultrafine polysaccharide nanofibers (i.e., cellulose and chitin) with 5-10 nm diameters were employed as barrier layers in a new class of thin-film nanofibrous composite (TFNC) membranes for water purification. In addition to concentration, the viscosity of the polysaccharide nanofiber coating suspension was also found to be affected by the pH value and ionic strength. When compared with two commercial UF membranes (PAN10 and PAN400), 10-fold higher permeation flux with above 99.5% rejection ratio were achieved by using ultrafine cellulose nanofibers-based TFNC membranes for ultrafiltration of oil/water emulsions. The very high surface-to-volume ratio and negatively charged surface of cellulose nanofibers, which lead to a high virus adsorption capacity as verified by MS2 bacteriophage testing, offer further opportunities in drinking water applications. The low cost of raw cellulose/chitin materials, the environmentally friendly fabrication process, and the impressive high-flux performance indicate that such ultrafine polysaccharide nanofibers-based TFNC membranes can surpass conventional membrane systems in many different water applications.

Nanofibrillation of Wood Pulp Using a High-Speed Blender

We report the successful use of a high-speed blender in nanofibrillating never-dried pulp to cellulose nanofibers (CNFs) with a uniform diameter of 15-20 nm. Pulp treated for 30 min in a blender showed the same degree of fibrillation with less damage to the CNF compared with that treated in a grinder. Observing the process of nanofibrillation clarified that the straw-like pulp was fibrillated in a very characteristic way, by forming many "balloon-like structures". As the balloons extended to the edges, the fibrils were rapidly individualized. However, the pulp fragments with ripped cell walls were split into finer fragments and gradually disintegrated into nanofibers. Changing the agitation speed and pulp concentration during the treatment revealed that the pulp concentration of 0.7 wt % at 37,000 rpm was the optimum fibrillation condition in this blender method. Through treatments in various NaCl solutions, the effect of the surface charge of CNF on the fibrillation was studied from the viewpoint of colloidal surface physics. It was found that repulsion due to the electric double layer of the CNF surface may play a critical role in the occurrence of fibrillation.