Yaru Wang

Nanofibrillated cellulose as the support and reductant for the facile synthesis of Fe3O4/Ag nanocomposites with catalytic and antibacterial activity

In this paper, we have demonstrated a facile and environmentally friendly approach to prepare Fe3O4/Ag@nanofibrillated cellulose (NFC) nanocomposites which enables tunability from highly porous, flexible aerogels to solid and stiff films. In the procedure, NFC acts as (i) a biocompatible support for the magnetic silver nanoparticles and (ii) a reducing agent for the silver ions. Neither additional reducing agents nor toxic organic solvents were used during the preparation process. The Fe3O4/Ag@NFC nanocomposite aerogel exhibited excellent catalytic properties (both in efficiency and recyclability) for the reduction of 4-nitrophenol. Moreover, both the Fe3O4/Ag@NFC nanocomposite aerogel and film can be actuated by a small household magnet, and both possess high antibacterial activity against the model microbe S. aureus.

Uniaxially Aligned Electrospun All-Cellulose Nanocomposite Nanofibers Reinforced with Cellulose Nanocrystals: Scaffold for Tissue Engineering

Uniaxially aligned cellulose nanofibers with well oriented cellulose nanocrystals (CNCs) embedded were fabricated via electrospinning using a rotating drum as the collector. Scanning electron microscope (SEM) images indicated that most cellulose nanofibers were uniaxially aligned. The incorporation of CNCs into the spinning dope resulted in more uniform morphology of the electrospun cellulose/CNCs nanocomposite nanofibers (ECCNN). Polarized light microscope (PLM) and transmission electron microscope (TEM) showed that CNCs dispersed well in ECCNN nonwovens and achieved considerable orientation along the long axis direction. This unique hierarchical microstructure of ECCNN nonwovens gave rise to remarkable enhancement of their physical properties. By incorporating 20% loading (in weight) of CNCs, the tensile strength and elastic modulus of ECCNN along the fiber alignment direction were increased by 101.7 and 171.6%, respectively. Their thermal stability was significantly improved as well. In addition, the ECCNN nonwovens were assessed as potential scaffold materials for tissue engineering. It was elucidated from MTT tests that the ECCNN were essentially nontoxic to human cells. Cell culture experiments demonstrated that cells could proliferate rapidly not only on the surface but also deep inside the ECCNN. More importantly, the aligned nanofibers of ECCNN exhibited a strong effect on directing cellular organization. This feature made the scaffold particularly useful for various artificial tissues or organs, such as blood vessel, tendon, nerve, and so on, in which cell orientation was crucial for their performance.

In situ synthesis of MnO2 coated cellulose nanofibers hybrid for effective removal of methylene blue

A one-step and energy-efficient synthetic method was developed to fabricate manganese dioxide (MnO2)/cellulose nanofibers (CNFs) hybrid. In this process, bamboo CNFs acted as both a reducing reagent for the Mn (VII) and an ultralight support for the generated MnO2 nanosheets. Neither additional reducing reagents nor heating were adopted during the synthesis process. The phase constitutions, crystal structure and morphology of the hybrid were systematically investigated. Both oxidative and adsorptive decolorization of methylene blue (MB) were investigated to evaluate its efficiency on dye wastewater treatment. The results showed that the few-layer MnO2 nanosheets deposited on CNFs exhibited high decolorization efficiency for the oxidation and adsorption of MB. When slurry containing 25 mg MnO2/CNFs hybrid was dispersed in 25 mL 80 mg L(-1) MB solution, the removal of MB was more than 99.8% within 2 min.

Reinforcement of all-cellulose nanocomposite films using native cellulose nanofibrils

All-cellulose nanocomposite films were prepared using native cellulose nanofibrils (CNFs) as fillers and lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) dissolved regenerated cellulose as the matrix. The CNFs, with diameters in the range of 15-40 nm were obtained by combined physical methods of ultrasonic treatment and high shear homogenization. The morphology, structure, and properties of the nanocomposite films were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), optical transmittance, thermal gravimetric analysis (TGA), and mechanical testing. The nanocomposite films exhibited good optical transparency, thermal stability, and remarkably enhanced mechanical properties compared to the regenerated cellulose matrix. By varying the CNFs content, the tensile strength of the nanocomposite films increased from 61.56 MPa to 99.92 MPa and the Youngs modulus increased from 0.76 GPa to 4.16 GPa. This work provided a promising pathway for manufacturing high performance and environmental-friendly all-cellulose nanocomposites.

Aerogels from quaternary ammonium-functionalized cellulose nanofibers for rapid removal of Cr(VI) from water.

An efficient heavy metal adsorbent from quaternary ammonium-functionalized cellulose nanofiber aerogels was successfully developed. The highly porous aerogel could well retain its large specific surface area, which allowed rapid and effective removal of Cr(VI) from contaminated water. The aerogel adsorbent became mechanically robust after chemical crosslinking. It could be easily separated from water after adsorption without complicated centrifugation or filtration process. With only 1g of aerogel, more than 99% of Cr(VI) in 1L of 1mg/L solution could be removed in 50 min. Besides, the aerogel also exhibited excellent reusability.

Flexible, highly transparent and iridescent all-cellulose hybrid nanopaper with enhanced mechanical strength and writable surface.

With the development of flexible electronic devices, there is increasing requirement for the inexpensive and environmental-friendly substrates. Cellulose paper has gained great attention because of its abundance, biodegradability and renewability. In this paper, we designed a hybrid nanopaper by introducing native cellulose nanofibrils (CNFs) into cellulose nanowhiskers (CNWs) matrix, which achieved a high optical transmittance while retaining iridescence under polarizing film. This nanopaper is less expensive than neat CNFs-based nanopaper and more feasible for large-scale production. Besides, our transparent hybrid nanopaper possesses the writable surface like regular paper. Compared with commercial paper, however, hybrid nanopaper shows superior optical properties and low surface roughness. The combination of these characteristics makes this nanopaper an excellent candidate for substrates of flexible electronic devices.

In situ growth of gold nanoparticles on magnetic γ-Fe2O3@cellulose nanocomposites: a highly active and recyclable catalyst for reduction of 4-nitrophenol

In this study, a facile synthetic method has been developed for in situ growth of Au nanoparticles (NPs) on magnetic γ-Fe2O3@carboxylated cellulose nanospheres using 2,2,6,6-tetramethylpiperidinyl-1-oxyl radical (TEMPO) oxide cellulose as linkage and reducing agent. The size of the as-prepared Au NPs can be tuned from 14 to 38 nm by the initial concentration of the gold salt used in the reaction mixture. Only one step was needed to synthesize the magnetic γ-Fe2O3@cellulose nanospheres. The formed γ-Fe2O3@carboxylated cellulose@Au is highly dispersible in aqueous solution and its potential as a magnetic catalyst is proved by the reduction reaction of 4-nitrophenol to 4-aminophenol. In particular, there was no visible decrease in the catalytic activity of the reused catalysts even after being recycled five times, which is preferred in terms of cost and environmental protection. Due to the absence of any other reducing agent during the proposed process, both the synthesis steps and the reaction cost were remarkably decreased, which makes it very suitable for industrial-scale production of recyclable catalysts.

Facile synthesis of magnetic nanocomposites of cellulose@ultrasmall iron oxide nanoparticles for water treatment

We report a facile in situ approach to synthesize magnetic nanocomposites of cellulose@ultrasmall iron oxide nanoparticles by co-precipitation using ionic liquid as co-solvent for cellulose and iron salt. The as-prepared γ-Fe2O3 nanoparticles showed ultrasmall particle size (∼4.6 nm) and uniform distribution (the standard deviation is less than 10%). The magnetic nanocomposites displayed excellent adsorption efficiency for Pb(II) and methylene blue compared with other reported magnetic materials. The adsorption capacities of the magnetic nanospheres for the removal of Pb(II) and methylene blue were 21.5 and 40.5 mg g−1, respectively. Furthermore, the prepared magnetic nanoadsorbent could be efficiently recycled and reused by applying an external magnetic field. The approach presented in this paper promotes the use of renewable natural resources to prepare a variety of hybrid inorganic–organic materials for the purpose of adsorbents, biomedical and other potential applications.

Acrylic acid grafted and acrylic acid/sodium humate grafted bamboo cellulose nanofibers for Cu2+ adsorption

Bamboo cellulose nanofibers-graft-poly (acrylic acid) (BCN-g-PAA) and bamboo cellulose nanofibers-graft-poly (acrylic acid)/sodium humate (BCN-g-PAA/SH) were synthesized for the first time and sequentially utilized as biosorbents for removal of Cu2+ from aqueous solutions. The chemical structure and morphology of both modified nanofibers were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. Batch adsorption experiments were conducted to elucidate their adsorption behaviors on Cu2+. The influencing factors, such as pH, contact time and initial Cu2+ concentration, on Cu2+ adsorption were investigated in detail. It was discovered that pH strongly influenced the Cu2+ adsorption. When pH increased from 2.0 to 4.5, the adsorption capacities of both modified nanofibers were improved significantly. Adsorption isotherm studies indicated that the Cu2+ adsorption could be described well by the Freundlich equation. Meanwhile, their adsorption kinetics was more likely to follow the pseudo-second-order model. These nanocellulose-based adsorbents exhibited very fast adsorption rates. The calculated adsorption capacities at equilibrium (qcale) for BCN-g-PAA and BCN-g-PAA/SH were 0.727 and 0.709 mmol g−1, significantly higher than that of BCN (0.286 mmol g−1). Adsorption/desorption cycling tests suggested that the introduced SH segments allowed for improved reusability of BCN-g-PAA/SH.

Cellulose hydrogels prepared from micron-sized bamboo cellulose fibers

We demonstrated for the first time that dimensionally stable hydrogels could be obtained from bamboo pulp fibers through dialysis against distilled water followed by a short time of ultrasonic treatment. Micron-sized short fibers rather than cellulose nanofibrils constituted the majority of fibers in the hydrogels. During the pulping process with HNO3 and KClO3, carboxylic groups could be introduced to cellulose due to the mild oxidation of hydroxyl groups. When presented in aqueous NaOH, the carboxylic groups could be converted into their sodium salt form. The subsequent dialysis treatment against water made the negatively charged COO(-) groups extensively exposed. The negatively charged cellulose fibers could induce considerable electrostatic repulsion between them, which was discovered to govern the formation of hydrogels. In addition, it was revealed that homogeneous hydrogels could be formed when the pH was at 7, 9 and 11. However, when salt was added, no dimensionally stable hydrogel was obtained.