Canhui Lu

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.

Aerogels from crosslinked cellulose nano/micro-fibrils and their fast shape recovery property in water

For the first time, we demonstrated that compressed aerogels made from crosslinked native cellulose nano/micro-fibril cellulose (NFC/MFC) show a fast shape recovery property after being immersed in water. The shape recovery degree in other solvents was also measured by the volume change of compressed aerogels. It was also found that the recovery degree strongly depends on the solvent properties. For water, more than 98% of the original shape was recovered in less than 10 s. However, only about 18% of its original shape was recovered by immersing the compressed aerogel in ethanol, and no shape recovery was observed by immersing in a nonpolar solvent, such as toluene. The crosslinked native NFC/MFC network is strong enough to withstand hot water and mechanical agitation (200 rpm mechanical stirring in water). The possible mechanism of shape and volume recovery of compressed NCF/MCF aerogel is discussed.

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.

A novel reagentless approach for synthesizing cellulose nanocrystal-supported palladium nanoparticles with enhanced catalytic performance

We report a one step and environment-friendly synthesis of cellulose nanocrystal (CN)-supported palladium nanoparticles (Pd NPs) without employing any other reductants, capping or dispersing agents. CNs played a dual role as a supporting matrix and a reductant and they were used to obtain stable dispersions of Pd NPs. The obtained hybrid material exhibited much higher activities than the unsupported and other polymer-supported Pd NPs in the catalyzed reduction of methylene blue and 4-nitrophenol. 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 catalysis, sensors, and other potential applications.

Melt-processed poly(vinyl alcohol) composites filled with microcrystalline cellulose from waste cotton fabrics

Waste cotton fabrics (WCFs), which are generated in a large volume from the textile industry, have caused serious disposal problem. Recycling WCFs into value-added products is one of the vital measures for both environmental and economic benefits. In this study, microcrystalline cellulose (MCC) was prepared by acid hydrolysis of WCFs, and used as reinforcement for melt-processed poly(vinyl alcohol) (PVA) with water and formamide as plasticizer. The microstructure and mechanical properties of the melt-processed PVA/MCC composites were characterized by Fourier transform infrared spectra, Raman spectra, differential scanning calorimetry, thermal gravimetric analysis, X-ray diffraction, tensile tests and dynamic mechanical analysis. The results indicated that MCC could establish strong interfacial interaction with PVA through hydrogen bonding. As a result, the crystallization of PVA was confined and its melting temperature was decreased, which was beneficial for the melt-processing of PVA. Compared with the unfilled PVA, the PVA/MCC composites exhibited remarkable improvement in modulus and tensile strength.

Facile synthesis of tunable silver nanostructures for antibacterial application using cellulose nanocrystals.

In this study, we report a facile and environmentally friendly strategy for synthesis of well dispersed and stable silver nanostructures using cellulose nanocrystals in aqueous solution without employing any other reductants, capping or dispersing agents. Importantly, it is feasible to adjust the morphology of the silver nanostructures by varying the precursor AgNO3 concentration. Silver nanospheres were formed when the AgNO3 concentration was 0.4 mM, while the dendritic nanostructures predominated when the AgNO3 concentration was increased to 250 mM. The antibacterial activity of the two different silver nanostructures against Escherichia coli and Staphylococcus aureus was characterized. Dendritic nanostructure showed a better antibacterial activity than that of silver nanosphere. The approach presented in this paper offers a very promising route to noble metal nanoparticles using renewable reducing agents.

Cellulose nanocrystals as a novel support for CuO nanoparticles catalysts: facile synthesis and their application to 4-nitrophenol reduction

Metal and metal oxide nanoparticles (NPs) have attracted considerable attention due to their excellent catalytic activities in various organic transformation reactions. However, their widespread application is limited because of their self-agglomeration in solution and the resulting reduced catalytic performance. Here we report that cellulose nanocrystals (CNs), which are sustainable and globally available in large quantities from plants, can be used as a novel support for copper oxide (CuO) NPs with enhanced catalytic performance. The high surface area of CNs and the abundant hydroxyl groups-induced immobilization of CuO NPs make the CNs-supported CuO NPs nanohybrids significantly stable, with CuO NPs/CNs suspensions remaining well-distributed even after a month. The obtained nanohybrids exhibited much higher catalytic activities than the unsupported and other materials-supported metal NPs (e.g. graphene oxide-supported CuO) in the catalyzed reduction of 4-nitrophenol. The facile processes used to make the nanohybrids catalysts are readily scalable to industrial levels.

Highly Sensitive, Stretchable, and Wash-Durable Strain Sensor Based on Ultrathin Conductive Layer@Polyurethane Yarn for Tiny Motion Monitoring

Strain sensors play an important role in the next generation of artificially intelligent products. However, it is difficult to achieve a good balance between the desirable performance and the easy-to-produce requirement of strain sensors. In this work, we proposed a simple, cost-efficient, and large-area compliant strategy for fabricating highly sensitive strain sensor by coating a polyurethane (PU) yarn with an ultrathin, elastic, and robust conductive polymer composite (CPC) layer consisting of carbon black and natural rubber. This CPC@PU yarn strain sensor exhibited high sensitivity with a gauge factor of 39 and detection limit of 0.1% strain. The elasticity and robustness of the CPC layer endowed the sensor with good reproducibility over 10,000 cycles and excellent wash- and corrosion-resistance. We confirmed the applicability of our strain sensor in monitoring tiny human motions. The results indicated that tiny normal physiological activities (including pronunciation, pulse, expression, swallowing, coughing, etc.) could be monitored using this CPC@PU sensor in real time. In particular, the pronunciation could be well parsed from the recorded delicate speech patterns, and the emotions of laughing and crying could be detected and distinguished using this sensor. Moreover, this CPC@PU strain-sensitive yarn could be woven into textiles to produce functional electronic fabrics. The high sensitivity and washing durability of this CPC@PU yarn strain sensor, together with its low-cost, simplicity, and environmental friendliness in fabrication, open up new opportunities for cost-efficient fabrication of high performance strain sensing devices.

Polyethylenimine-Grafted Cellulose Nanofibril Aerogels as Versatile Vehicles for Drug Delivery

Aerogels from polyethylenimine-grafted cellulose nanofibrils (CNFs-PEI) were developed for the first time as a novel drug delivery system. The morphology and structure of the CNFs before and after chemical modification were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Water-soluble sodium salicylate (NaSA) was used as a model drug for the investigation of drug loading and release performance. The CNFs-PEI aerogels exhibited a high drug loading capability (287.39 mg/g), and the drug adsorption process could be well described by Langmuir isotherm and pseudo-second-order kinetics models. Drug release experiments demonstrated a sustained and controlled release behavior of the aerogels highly dependent on pH and temperature. This process followed quite well the pseudo-second-order release kinetics. Owing to the unique pH- and temperature-responsiveness together with their excellent biodegradability and biocompatibility, the CNFs-PEI aerogels were very promising as a new generation of controlled drug delivery carriers, offering simple and safe alternatives to the conventional systems from synthetic polymers.

Green synthesis and formation mechanism of cellulose nanocrystal-supported gold nanoparticles with enhanced catalytic performance

Deposition of precious metal catalysts onto the surface of various supporting materials to enhance the stability and catalytic activity is highly desired. Although extensive studies have been focused on the supported metal catalysts, their preparations are mainly based on the use of reducing agents which are not environmentally benign. Herein, we report a one-pot and green synthesis of gold nanoparticles (Au NPs) deposited on cellulose nanocrystals (CNs) under hydrothermal conditions using CNs as a reducing agent and stabilizing template. Our experimental results showed that the abundant electron-rich hydroxyl groups on the surface of CNs played a key role in the reduction and immobilization of Au NPs. The obtained nanohybrid catalyst exhibited much better catalytic activity and stability than the unsupported Au NPs and other Au-containing catalysts for the reduction of 4-nitrophenol. These findings pave the way for the green synthesis of bio-supported nanohybrid catalysts and can spur advancements in nanocellulose-based nanohybrids for their application in sensors, antibacterial materials and electronic devices.