Chitosan-based oxygen-doped activated carbon/graphene composite for flexible supercapacitors.

Flexible supercapacitors have attracted widespread attention from many researchers as a type of portable energy storage device. As a unique carbon material, graphene has shown great potential in supercapacitor electrodes, mainly due to its large theoretical specific surface area, high conductivity and chemical stability. Therefore, reasonable design of graphene-based hydrogels with low cost, high specific surface area, and excellent mechanical properties is of great significance for flexible and wearable energy storage device applications. Oxygen-doped activated carbon/graphene composite hydrogels have been fabricated using a one-step hydrothermal method. In the hybrid hydrogel, the activated carbon derived from chitosan with high specific surface area and oxygen-containing groups which were introduced by using a facile room-temperature oxidation strategy with HNO3 are assembled into the framework of reduced graphene oxide (rGO) to effectively prevent the restacking of rGO nanosheets and result in high specific surface area and high conductivity of the composite hydrogels, thereby leading to an excellent energy storage performance. The optimal sample displayed a high specific capacitance of 375.7 F g-1 in 1 M H2SO4 electrolyte at a current density of 1 A g-1. Furthermore, the assembled flexible supercapacitor showed an ideal cycling stability of 83% after 5000 charge/discharge cycles at 10 A g-1. The facile strategy developed in this work is of significance for the performance improvement of supercapacitor electrode materials.

Different biomass production and soil water patterns between natural and artificial vegetation along an environmental gradient on the Loess Plateau.

Loess Plateau (LP) is a vulnerable and climate-sensitive ecoregion. With the implementation of "Grain for Green" project (GGP), the vegetation cover has largely improved, while the contradiction between overconsumption of soil water and sustainability of restored vegetation is increasingly prominent, and further threatening the ecosystem sustainability and socioeconomic development. Understanding the different responses of relations of biomass production and soil water regimes between natural and artificial vegetation along environmental gradient will be crucial for sustainability of restored vegetation on the LP. Here, aboveground biomass (AGB) and soil water content (SWC) of natural and artificial vegetation were measured in steppe, forest-steppe and forest zone from 2008 to 2017 on the Yanhe River catchment. The results showed that artificial vegetation consumed more soil water than natural vegetation in steppe and forest-steppe zone, while it did not over consume soil water in forest zone. The AGB of natural vegetation in forest zone was significantly higher than that in steppe and forest-steppe zone. Steppe zone had serious overload of artificial vegetation (overload ratio: 5.35), while no overload occurred in forest zone. So, we suggest a cessation of artificial vegetation expansion in steppe zone. In steppe zone, planting artificial vegetation increased competition intensity between AGB and SWC, and the relative benefit tended to be AGB, their competition intensity was the highest. In forest zone, the trade-off relationship between AGB and SWC had no significant difference between natural and artificial vegetation, and the competition intensity between the AGB and SWC was the weakest. Optimal vegetation restoration approach would maintain the balance between vegetation restoration and soil water. To obtain social and ecological sustainability on the LP, vegetation suitability and suitable management along different environmental gradients should be considered and identified in the future revegetation project.

Advances in molecular biology of Paeonia L.

Molecular biology can serve as a tool to solve the limitations of traditional breeding and cultivation techniques related to flower patterns, the improvement of flower color, and the regulation of flowering and stress resistance. These characteristics of molecular biology ensured its significant role in improving the efficiency of breeding and germplasm amelioration of Paeonia. This review describes the advances in molecular biology of Paeonia, including: (1) the application of molecular markers; (2) genomics, transcriptomics, proteomics, metabolomics, and microRNA studies; (3) studies of functional genes; and (4) molecular biology techniques. This review also points out select limitations in current molecular biology, analyzes the direction of Paeonia molecular biology research, and provides advice for future research objectives.

Transcriptome and chemical analysis reveal putative genes involved in flower color change in Paeonia 'Coral Sunset'.

The flower color of Paeonia 'Coral Sunset' and 'Pink Hawaiian Coral' changes from coral to pink to pale yellow during flowering, which confers high ornamental value to these two cultivars. However, the molecular mechanism underlying flower color change is still unclear. In this study, flavonoids in petals of Paeonia 'Coral Sunset' and 'Pink Hawaiian Coral' at seven flowering stages were analyzed to explore the effects of the flavonoid component on changes in flower color. In addition, four cDNA libraries of 'Coral Sunset' during the critical blooming stages were constructed and the transcriptome was sequenced to investigate the molecular mechanism underlying changes to flower color. Two anthocyanins (cyanidin-3,5-di-O-glucoside and peonidin-3,5-di-O-glucoside) were detected in both cultivars. Total anthocyanin content in both cultivars accumulated continuously from stages 1-3 and then decreased sharply. Correlation analysis showed that the change in flower color from coral to pink to pale yellow is due to a significant decrease in anthocyanin content. A total of 91,583 Unigenes were obtained in 'Coral Sunset', 33,962 (37.08%) of which were annotated to major databases. Based on the enrichment analysis of differentially expressed genes, eight structural genes (CHS, F3H, F3'H, FLS, DRF, ANS, ANR and UFGT) and 13 transcription factors (five MYB, three bHLH, one WD40, one HY5, one PIF3, one COP1 and two PHY) related to flavonoid biosynthesis were screened. The qRT-PCR results were generally consistent with the high-throughput sequencing results. This research will provide a foundation to clarify the mechanisms underlying changes in flower color of herbaceous peony.

Molecular structure and spectral characteristics of hyperoside and analysis of its molecular imprinting adsorption properties based on density functional theory.

The structure of hyperoside was optimized according to the skeletal types of different galactopyranosides in hyperoside at the DFT/B3LYP/6-31++G(d,p) level, and the frequencies were calculated. The accuracy of the theoretical calculations of the 1H and 13C NMR signals was evaluated by linear correlation. The excited state was calculated via time-dependent density functional theory (TD-DFT). The stable conformation, NMR, UV-vis, natural bond orbital (NBO), molecular electrostatic potential (MEP) and thermodynamic information were obtained. In the most stable conformation of hyperoside, seven intramolecular hydrogen bonds are formed, which affect the imprinting efficiency. The theoretical 1H and 13C NMR results are in good agreement with the experimental results. The B3PW91 function is more suitable than B3LYP for TD-DFT calculations. Combining the UV-vis and NBO analyses, the HOMO→LUMO transition mainly results from the n→π∗ transition of the phenolic hydroxyl groups and the π→π∗ transition of the benzene ring on the B ring in ethanol. The HOMO-1→LUMO+1 transition mainly results from the n→π∗ and π→π∗ transition on the A ring. The MEP and NBO calculations indicate that the imprinted active sites are mainly located on the carbonyl oxygen atom and the hydroxyl hydrogen atoms. As the temperature increases, the molecular heat capacity, entropy, enthalpy, and activity of the imprinting sites increase. The obtained results provide strong theoretical guidance for hyperoside in the synthesis of molecularly imprinted polymers and separation techniques.

Heat-Induced Discoloration of Chromophore Structures in Eucalyptus Lignin.

The color changes corresponding to chromophore structures in lignin caused by exposure of Eucalyptus (Eucalyptus grandis and E. urophylla) to heat were investigated. Eucalyptus wood powders were heat treated under saturated steam atmospheres for 10 h at 110 °C, 130 °C and 150 °C. The lignin was isolated before and after heat treatment. The physicochemical properties of the lignin and changes in chromophore structures during heat treatment was evaluated through wet chemical analysis, Fourier transform infrared spectroscopy (FTIR), diffuse reflectance ultraviolet-visible spectroscopy (DRUV-Vis), gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS) and 13C Cross polarization magic angle spinning nuclear magnetic resonance (13C CPMAS NMR). Wood color darkened and reddened with the increase in pressure and temperature. Depolymerization and dehydration reactions occurred via demethoxylation with heat treatment in saturated steam at 110 °C or 130 °C. Lignin condensed to form insoluble compounds after heat treatment in saturated steam at 150 °C. G units increased and S units decreased through demethylation during heat treatment, as revealed by FTIR and 13C-NMR analysis.

Facile synthesis of urchin-like RuCu and hollow RuCuMo nanoparticles and preliminary insight to their formation process by cyclic voltammetry.

Urchin-like RuCu nanoparticles and hollow RuCuMo nanoparticles were prepared by a one-pot chemical reduction method. The nanoparticles were characterized by EDX, HRTEM, XPS and ICP-AES. By combining cyclic voltammetry and TEM, the formation process of nanoparticles was obtained. The urchin-like RuCu nanoparticles are proved to be formed via underpotential deposition mechanism and the formation of ternary nanoparticles RuCuMo was due to the replacement of Cu with Ru and the interception of Mo gradually. It was found that the formation of different morphology is depended on the precursors in the reaction system and their reduction sequences. Compared to previously reported multi-step synthetic routes, the developed method here is much simpler.

Valorization of bamboo by γ-valerolactone/acid/water to produce digestible cellulose, degraded sugars and lignin.

A novel pretreatment process was developed to achieve valorization of bamboo components into digestible cellulose, degraded sugars and lignin. In this case, bamboo was pretreated with 60% γ-valerolactone (GVL)/40% water containing 0.05mol/L H2SO4, yielding solid fraction rich in cellulose. The resulting liquor was further treated with the addition of NaCl and ultrasound, resulting in water phase rich in degraded sugars and GVL phase containing lignin, which was easy to recover. Results showed that the enzymatic hydrolysis was enhanced by 6.7-fold after treatment as compared to the control. The degraded sugars released in water phase contained monosaccharides (70.72-160.47g/kg) together with oligo- and polysaccharides (46.4-181.85g/kg). The lignin obtained had high purity, low molecular weight (1820-2970gmol-1) and low polydispersity (1.93-1.98). The present study creates a novel pretreatment process for the conversion of Gramineae biomass into useful feedstocks with potential applications in the fields of fuels, chemicals and polymers.

Epoxidation and etherification of alkaline lignin to prepare water-soluble derivatives and its performance in improvement of enzymatic hydrolysis efficiency.

BACKGROUND: Due to the depletion of fossil resources and their environmental impact, woody biomass has received much attention as an alternative resource. Lignin, as the third most abundant biopolymer from biomass, is now considered as an excellent alternative feedstock for chemicals and materials. The conversion of lignin to the value-added products is a key process to achieve an integrated biorefinery of woody biomass. Among these value-added products, lignin-based derivatives with good surface activity can be applied to enhance the conversion of cellulose into fermentable sugars, which not only decrease the cost of bioethanol production, but also reduce the environmental pollution and green house effect resulting from the burning of fossil resources. RESULTS: Water-soluble alkaline lignin was synthesized by the reaction between polyethylene glycols (PEG600 and PEG1000) and epoxy lignin. FT-IR and NMR analyses indicated that PEGs were successively introduced into epoxy alkaline lignin using potassium persulfate as a catalyst. Emulsification and surface activity tests indicated that the surface tension of the prepared lignin derivative solution was 43.30 mN/m at the critical micelle concentration (1.03 %). A stable emulsions layer was formed with hexanes and the emulsion particle diameter in the emulsion phase for all products was observed at 10-50 µm. The results of enzymatic hydrolysis indicated that the products derived from PEG1000-grafted lignin resulted in the highest increasing rate of 18.6 % of glucose yield during the enzymatic hydrolysis of hardwood bleached pulp. The results of fermentation experiments suggested that the product had no toxicity for fermentation micro-organisms. CONCLUSION: Water-soluble alkaline lignin derivatives were prepared through epoxidation and etherification, which are promising feedstocks for detergents, emulsifier, and additive to enhance enzymatic hydrolysis efficiency and ethanol fermentation.

Weathering Characteristics of Wood Plastic Composites Reinforced with Extracted or Delignified Wood Flour.

This study investigated weathering performance of an HDPE wood plastic composite reinforced with extracted or delignified wood flour (WF). The wood flour was pre-extracted with three different solvents, toluene/ethanol (TE), acetone/water (AW), and hot water (HW), or sodium chlorite/acetic acid. The spectral properties of the composites before and after artificial weathering under accelerated conditions were characterized by Fourier transform infrared (FTIR) spectroscopy, the surface color parameters were analyzed using colorimetry, and the mechanical properties were determined by a flexural test. Weathering of WPC resulted in a surface lightening and a decrease in wood index (wood/HDPE) and flexural strength. WPCs that were reinforced with delignified wood flour showed higher ΔL* and ΔE* values, together with lower MOE and MOR retention ratios upon weathering when compared to those with non-extracted control and extracted WF.

Multivariate modular metabolic engineering of Escherichia coli to produce resveratrol from L-tyrosine.

Microbial fermentations and bioconversion promise to revolutionize the conventional extraction of resveratrol from natural plant sources. However, the development of efficient and feasible microbial processes remains challenging. Current fermentation strategies often require supplementation of expensive phenylpropanoic precursors and two separate fermentation protocols, which are significantly more difficult and expensive to undertake when migrating to large-scale fermentation processes. In this study, an Escherichia coli fermentation system, consisting of tyrosine ammonia lyase (TAL), 4-coumarate:CoA ligase (4CL), stilbene synthase (STS), malonate synthetase, and malonate carrier protein, was developed to produce resveratrol from L-tyrosine. Multivariate modular metabolic engineering, which redefined the overall pathway as a collection of distinct modules, was employed to assess and alleviate pathway bottlenecks. Using this strategy, the optimum strain was capable of producing 35.02 mg/L of resveratrol from L-tyrosine in a single medium. The strategy described here paves the way to the development of a simple and economical process for microbial production of resveratrol and other similar stilbene chemicals.