A highly sensitive and anti-freezing conductive strain sensor based on polypyrrole/cellulose nanofiber crosslinked polyvinyl alcohol hydrogel for human motion detection.

Electro-conductive hydrogels emerge as a stretchable conductive materials with diverse applications in the synthesis of flexible strain sensors. However, the high-water content and low cross-links density cause them to be mechanically destroyed and freeze at subzero temperatures, limiting their practical applications. Herein, we report a one-pot strategy by co-incorporating cellulose nanofiber (CNF), Poly pyrrole (PPy) and glycerol with polyvinyl alcohol (PVA) to prepare hydrogel. The addition of PPy endowed the hydrogel with good conductivity (∼0.034 S/m) compared to the no PPy@CNF group (∼0.0095 S/m), the conductivity was increased by 257.9 %. The hydrogel exhibits comparable ionic conductivity at -18 °C as it does at room temperature. It's attributed to the glycerol as a cryoprotectant and the formation of hydrated [Zn(H2O)n]2+ ions via strong interaction between Zn2+ and water molecules. Moreover, the cellulose nanofiber intrinsically assembled into unique hierarchical structures allow for strong hydrogen bonds between adjacent cellulose and PPy polymer chains, greatly improve the mechanical strength (stress∼0.65 MPa, strain∼301 %) and excellent viscoelasticity (G'max âˆ¼ 82.7 KPa). This novel PPy@CNF-PVA hydrogel exhibits extremely high Gauge factor (GF) of 2.84 and shows excellent sensitivity, repeatability and stability. Therefore, the hydrogel can serve as reliable and stable strain sensor which shows excellent responsiveness in human activities monitoration.

Synthesis of Superhydrophobic Cellulose Stearoyl Ester for Oil/Water Separation.

Developing fluorine-free superhydrophobic and biodegradable materials for oil/water separation has already become an irresistible trend. In this paper, we designed two biopolymer oil/water separation routes based on cellulose stearoyl ester (CSE), which was obtained via the acylation reaction between dissolving pulp and stearoyl chloride homogeneously. The CSE showed a superhydrophobic property, which could selectively adsorb oil from the oil/water mixture. Additionally, the CSE was emulsified with an oxidized starch (OS) solution, and the resulting latex was used to impregnate commercial, filter base paper, finally obtaining a hydrophobic and oleophilic membrane. The SEM revealed the membrane had hierarchical micro/nanostructures, while the water contact angle indicated the low surface energy of the membrane, all of which were attributed to the CSE. The membrane had high strength and long durability due to the addition of OS/CSE, and the separation efficiency was more than 99% even after ten repeated uses.

Porous Carbon Material Derived from Steam-Exploded Poplar for Supercapacitor: Insights into Synergistic Effect of KOH and Urea on the Structure and Electrochemical Properties.

The electrochemical performance of supercapacitors using porous carbon as electrodes is strongly affected by the fabrication process of carbon material. KOH is commonly used as an activator combined with urea as a nitrogen dopant. However, the roles of KOH and urea in pore structure configuration and the electrochemical behavior of porous carbon electrodes are still ambiguous. Herein, the optimum porous carbon is obtained when KOH and urea are used simultaneously. KOH is used as a pore-forming substance, whereas urea is employed as a nitrogen source for the nitrogen doping of porous carbon, which increases its defect sites while reducing the graphitization degree. More importantly, urea also expands pores as a pore-enlarging agent, inducing interconnected porous structures. As a result, a hierarchical porous structure is formed and ascribed to the synergistic effect of KOH and urea, and the specific surface area reached 3282 m2 g-1 for sample PC800-4. The specific capacitance is 319 F g-1 at 0.5 A g-1 with excellent cycling stability over 2500 cycles. Furthermore, the symmetric supercapacitor reaches an excellent energy density of 11.6 W h kg-1 under 70.0 W kg-1 in a 6 M KOH electrolyte. Our work contributes to the rational designation of the porous carbon structure for supercapacitor applications.

One-pot freezing-thawing preparation of cellulose nanofibrils reinforced polyvinyl alcohol based ionic hydrogel strain sensor for human motion monitoring.

Ionic conductive hydrogels have been widely applied in sensors, energy storage and soft electronics recently. However, most of the polyvinyl alcohol (PVA) based ionic hydrogels are mainly fabricated by soaking the hydrogels in high concentration electrolyte solution which can induce the waste of electrolyte and solvent. Herein, we have designed cellulose nanofibrils (CNF) and ZnSO4 reinforced PVA based hydrogels through a one-pot simple freezing-thawing method at low ZnSO4 concentration without any soaking process. Furthermore, the hydrogel with 0.4% CNF exhibited stress up to 0.79 MPa (242% strain) and high ionic conductivity of 0.32 S m-1 (0.07 M ZnSO4). Moreover, hydrogel sensor displayed high linear gauge factor 1.70 (0-200% strain), excellent stability, durability and reliability. The integrated hydrogel sensor also showed excellent sensor performance for human motion monitoring. This work provides a new prospect for the design of cellulose reinforced conductive hydrogels via a facile method.

Superhydrophobic modification of nanocellulose based on an octadecylamine/dopamine system.

We prepared super-hydrophobic nanocellulose films using a non-toxic octadecylamine/polydopamine system. Octadecylamine, a low surface energy material, was used to provide hydrophobic alkyl long chains. Polydopamine was produced by dopamine under alkaline conditions, creating an adhesive substance, which reinforced the hydrophobic long chains and increased the surface roughness of nanocellulose. The effects of reagent concentration, reaction temperature, and reaction time on hydrophobicity were then investigated. The results showed that with a 1:1 mass ratio of nanocellulose to octadecylamine, and reacting at 60 °C for 4 h, the contact angle of the obtained composite membrane reached 168.2°. Scanning electron microscope images revealed that the modified nanocellulose had a smaller particle size and more uniform distribution, which effectively improved the hydrophobicity of the nanocellulose. Thus, the green preparation of superhydrophobic films with high-temperature resistance and wear resistance was realized, which contributed to the high-value utilization of nanocellulose.

Solid acid facilitated deep eutectic solvents extraction of high-purity and antioxidative lignin production from poplar wood.

Pure deep eutectic solvents (DESs) system of choline chloride (ChCl)/Lactic acid (Lac) were demonstrated to be an effective strategy for extraction of lignin. In this study, two kinds of different promising solid acid (SA) with DESs were designed to promote the pretreatment of lignocellulose. The SA of phosphotungstic acid (H3O40PW12) and iron bromide (FeBr3) were introduced into DESs to extract poplar wood lignin and evaluate the antioxidant activity. It was found that 82.2% and 80.9% of lignin were obtained from poplar wood under H3O40PW12-ChCl/Lac acid and FeBr3-choline ChCl/Lac system with 4 h and 8 h, respectively. The lignin fractions with a high purity (>89%), low molecular weight (Mw 1800-2000 g/mol). Besides, the antioxidant activities of lignin fractions were better than butyl hydroxyanisole (BHA). Therefore, DES lignin has prominent antioxidant activity and could developed a potential natural cosmetics and food packaging.

Valorization of Miscanthus × giganteus by γ-Valerolactone/H2O/FeCl3 system toward efficient conversion of cellulose and hemicelluloses.

γ-Valerolactone (GVL), a biomass-derived green chemical, offers an environmentally responsible solvent for conversion of lignocellulose to high value-added chemicals. Herein, we report a two-step process for directly producing cellulosic residual, furfural and lignin from Miscanthus × giganteus (M. × giganteus) bypassing the isolation of xylose, which exhibits promising advantage in energy reduction. The optimized pretreatment (100 mM FeCl3 at 160 °C for 60 min) induced significant xylan removal (98.4%), resulting in rugged fibre surface, thus leading to the peak cellulose conversion of 99.3%. Furfural yield in the second step reached to 76.6% after 100 mM FeCl3 catalyzed GVL/H2O treatment at 180 °C for 10 min without addition of any chemical. The extracted lignin showed representative structure (such as ß-O-4', ß-ß' linkages) and medium molecular weight (4275.5 g/mol). 79.6% of furfural can be recovered by distillation. This study proposes a systematic and energy efficient approach for maximizing biomass utilization.

Lab-scale design of two layers wood cellulose filter media to maximize life span for intake air filtration.

The requirement of continuous and stringent growth on filtration performance, including longer life span, higher overall efficiency, lower initial pressure drop and more cost effective, has still drove filter media manufactures to research and develop. One of the possible way to achieve these challenges, was to utilize a dual-channel head-box with two sets of pulp conveying system, which can produce filter media with bulky and gradient properties. In this study, three kinds of commercial cellulose were chosen to make two layers filtration media, analyzed the effect of fiber blend on physical properties and filtration performance. By fine-tune the slurry ratio of top layer, we made one single layer and two layers composition filter media, the thickness and air permeability of composition media were higher than single layer media. According to ISO 5011, filtration performance test has been done to compare single layer media with composition media, this composition gradient profiles that provided the life span 37.0% improvement to the terminal pressure drop during dust injecting, and the dust hold capacity improved 34.7%, the main contributor of dust hold capacity was decided by top layer, however, the overall efficiency was depended on wire side layer.

Assessment on temperature-pressure severally controlled explosion pretreatment of poplar.

In this work, temperature-pressure severally controlled explosion pretreatment (TPE) was proposed to pretreat poplar chips to improve the cellulase hydrolysis yield. In TPE process, native poplar chips (NP) were mixed with steam and N2 under pressure of 2.6, 2.8 and 3.0 MPa at 209 °C for 7 min. Meanwhile, steam explosion (SE) was also used to pretreat poplar chips for comparison at 209 °C (1.9 MPa) for 7 min. Results showed that the contents of hemicellulose and lignin were decreased from 19.4 % to 4.6 % and from 27.8 %-19.5 % with increasing pressure, respectively. For cellulase hydrolysis process, TPE was more advantageous than SE due to lower contents of hemicellulose and lignin, resulting in a higher cellulose conversion (40.7 %) in relation to SE sample (34.9 %). The Langmuir isothermal- type equation expressed the factors related to the hydrolysis capacity, and the results showed that this model can well describe the kinetics of the enzymatic hydrolysis.

Nanofiltration filter paper based on multi-walled carbon nanotubes and cellulose filter papers.

Air filter paper with a high filtration efficiency that can remove small-size pollutant particles and toxic gases is vital for human health and the environment. We report a nanofiltration paper that is based on wood fiber filter paper with good mechanical properties and a three-dimensional network structure. The filter paper was prepared by impregnation with multi-walled carbon nanotubes (MWCNTs) and phenol-formaldehyde (PF). The results showed that MWCNTs were present on the surfaces of the fibers and between the pores, which increased the specific surface area of the fibers and enhanced the effective interception of the particles. The optimum impregnation concentration of the MWCNT was 0.1%. Compared with the cellulose fibers (CFs), the average pore diameter of the 0.1% MWCNT-CF filter paper was reduced by 8.05%, the filtration efficiency was increased by 0.64%, and the physical properties were slightly enhanced. After impregnation with PF, the mechanical properties of the air filter paper were significantly enhanced. The PF on the fiber surfaces and at the junction of the fibers covered the MWCNTs. Based on the change in the filter paper properties after impregnation, the optimal filter paper strength index and filtration performance were observed at a solid PF content of 8.4%.

A Facile Preparation of Super Long-Term Stable Lignin Nanoparticles from Black Liquor.

Invited for this month's cover is the group of Lin Dai and Zhong Liu at TUST and Yonghao Ni at UNB. The image shows how the hemicellulose can play a role in prolonging the stability of lignin nanoparticles The Full Paper itself is available at 10.1002/cssc.201902287.

A Facile Preparation of Super Long-Term Stable Lignin Nanoparticles from Black Liquor.

With the increase in lignin availability, materials derived from micro- and nano-scale lignin developed rapidly. However, the tedious processes of raw-lignin pretreatment and poor stability seriously restrict the large-scale applications of lignin nanoparticles. To overcome these problems, in this work, a novel green and simple approach was developed to produce super long-term stable lignin nanoparticles (LTSL NPs). The LTSL NPs were prepared directly from black liquor via an acid precipitation method. The obtained LTSL NPs exhibited well uniformity, excellent dispersibility, controllable size, and super long-term stability in aqueous media (no apparent size increase or any particle precipitation for 90 days in neutral water medium). Analyses of nuclear magnetic resonance and ion chromatography revealed that LTSL NPs exhibited higher S/G ratio and higher content of hemicellulose comparing with the lignin nanoparticles which obtained from traditional solvent exchange (ethanol/H2 O) method. In addition, the size of the LTSL NPs can be well controlled by tuning the degree of acid precipitation (the final pH value). This work not only can promote the development of lignin-based nanomaterials, but also provides a promising utilization pathway for black liquor that simultaneously achieves the fabrication of lignin materials and hemicellulose application.

Lignin-containing cellulose nanocrystals/sodium alginate beads as highly effective adsorbents for cationic organic dyes.

Cellulose nanocrystals (CNCs) is an exciting class of sustainable and carbohydrate material, which has great potential applications in molecular adsorption. However, the complex preparation process and limited adsorption capacity of CNCs hinder its commercial application. In this study, we design a novel functional cellulose nanocrystals-based adsorbent by an ingenious mixing of lignin-containing cellulose nanocrystals (LCNCs), sodium alginate (SA), and calcium chloride solution. Benefiting from the sulfonate groups of lignin, carboxyl groups of SA, the maximum adsorptive capability of LCNCs/SA beads for methylene blue was found to be 1181 mg g-1, which was significantly higher than previously reported biomass-based adsorbents. More importantly, LCNCs/SA beads can be reused several times. This strategy can not only improve the adsorption performance of CNCs-based materials, but also simplify the production technology of CNCs, which greatly promote the commercial application of CNCs materials.

Identification of functional butanol-tolerant genes from Escherichia coli mutants derived from error-prone PCR-based whole-genome shuffling.

BACKGROUND: Butanol is an important biofuel and chemical. The development of butanol-tolerant strains and the identification of functional butanol-tolerant genes is essential for high-yield bio-butanol production due to the toxicity of butanol. RESULTS: Escherichia coli BW25113 was subjected for the first time to error-prone PCR-based whole-genome shuffling. The resulting mutants BW1847 and BW1857 were found to tolerate 2% (v/v) butanol and short-chain alcohols, including ethanol, isobutanol, and 1-pentanol. The mutants exhibited good stability under butanol stress, indicating that they are potential host strains for the construction of butanol pathways. BW1847 had better butanol tolerance than BW1857 under 0-0.75% (v/v) butanol stress, but showed a lower tolerance than BW1857 under 1.25-2% (v/v) butanol stress. Genome resequencing and PCR confirmation revealed that BW1847 and BW1857 had nine and seven single nucleotide polymorphisms, respectively, and a common 14-kb deletion. Functional complementation experiments of the SNPs and deleted genes demonstrated that the mutations of acrB and rob gene and the deletion of TqsA increased the tolerance of the two mutants to butanol. Genome-wide site-specific mutated strains DT385 (acrB C1198T) and DT900 (rob AT686-7) also showed significant tolerance to butanol and had higher butanol efflux ability than the control, further demonstrating that their mutations yield an inactive protein that enhances butanol resistance characteristics. CONCLUSIONS: Stable E. coli mutants with enhanced short alcohols and high concentrations of butanol tolerance were obtained through a rapid and effective method. The key genes of butanol tolerance in the two mutants were identified by comparative functional genomic analysis.

Characterization of liquefied products from corn stalk and its biomass components by polyhydric alcohols with phosphoric acid.

The hemicellulose, cellulose and lignin were directly separated from corn stalk, and their liquefaction processes were investigated via acid-catalyzed solvolysis treatment with 1,2-propylene glycol (PG) and diethylene glycol (DEG) to produce bio-oil and residues. The main components, functional groups and organics structure of bio-oil were analyzed by the FTIR, 1H-NMR, 13C-NMR, GCMS, and TGA. It was found that there had a similar tendency in the liquefaction processes of cellulose, hemicellulose and lignin. Corn stalk and its biomass components were degraded and formed plentiful low-molecular polymers by acid catalysis, prior to polymers were converted into corresponding PG/DEG-derivatives. Finally, low-molecular weight soluble substances and insoluble residues were generated by decomposition and polymerization. Additionally, more than 80% compounds' carbon number in four bio-oils was below 25. The residues were mostly stemmed from macromolecules produced by degradation products and PG/DEG or re-polymerization between degraded small molecules.

Cationic cellulose nanofibers as sustainable flocculant and retention aid for reconstituted tobacco sheet with high performance.

The study that cationic cellulose nanofibers (CCNF) acts as sustainable flocculant and retention aid of precipitated calcium carbonate (PCC) for the preparation of reconstituted tobacco sheet (RTS) was carried out, thanks to the properties of CCNF. In this work, the enhanced flocculation, reflocculation and size properties of PCC flocs induced by CCNF were investigated via a focused beam reflectance measurement (FBRM) system. The physical properties of RTS such as bulk and air permeability etc. were also studied. The results indicated that CCNF could distinctly improve the flocculation and reflocculation properties of PCC with a desirable chord length in the tobacco slurry, and that the PCC retention was also increased with CCNF addition along with a slight decrease of tensile strength of RTS. The mechanisms of flocculation and reflocculation, as well as the reasons of enhanced bulk and air permeability properties ascribed to CCNF were also demonstrated.

Characterization of high-yield pulp (HYP) by the solute exclusion technique.

By following the solute exclusion technique, we determined the pore characteristics of 3 hardwood high-yield pulps (aspen, birch, maple). The fiber saturation point (FSP) was 1.40, 1.36 and 1.19 g water/g pulp, for aspen, birch, maple, respectively, which is lower than that of chemical pulps. Different fractions obtained from the Bauer-McNett classifier showed that the HYP fines have much more pore volume than their long fiber counterparts. The effects of beating, drying and re-wetting on the pore characteristics of HYP were also studied. Beating led to increased total pore volumes. Upon drying and re-wetting, much of the small pores from the HYP underwent permanent closure while the big pores were only slightly affected. Finally, the relationship between the water retention value (WRV) and FSP for HYP was examined.