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Cao S.,Shaanxi University of Science and Technology | Ning Q.,Shaanxi University of Science and Technology | Yu C.,Shaanxi University of Science and Technology | Qiao C.,Tsinghua Innovation Center in Dongguan | And 2 more authors.
Journal of Alloys and Compounds | Year: 2017

The rod-like NaSr2Nb5O15: 0.03Eu3+ phosphors have been synthesized via the molten salt synthesis (MSS). The as-prepared phosphors were characterized by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), Energy dispersive X-ray analysis (EDAX), Transmission electron microscope (TEM), High-resolution transmission electron microscope (HRTEM), UV–Vis–NIR spectrophotometer and Photoluminescence spectrometer (PL). The results indicated that the symmetry of A1 site is higher than A2 site in NaSr2Nb5O15 lattice. The morphology and dimensions could be adjusted by controlling the reaction conditions, and the morphology evolution process was proposed. With the increasing of the time and temperature, the average sizes of the obtained particles increased from 10.91 μm to 24.03 μm in length, and from 2.82 μm to 13.68 μm in diameter, whereas the aspect ratio reduced from 4.07 to 1.84. Meanwhile, the luminescence intensity and lifetime increased with the decreasing of the aspect ratio. Furthermore, the emission spectra of the phosphors were diverse under the different excitations (NUV and blue light). The present work shows that the NaSr2Nb5O15: Eu3+ could be a potential phosphor for LED. © 2016 Elsevier B.V.

Wang M.,Harbin Institute of Technology | Wang T.,Harbin Institute of Technology | Song S.,Harbin Institute of Technology | Ma Q.,Tsinghua University | And 3 more authors.
Materials | Year: 2017

Based on precursor powders with a size of 200-300 nm prepared by the low-temperature solid reaction method, phase-pure YFeO3 ceramics are fabricated using spark plasma sintering (SPS) at different temperatures. X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveal that the high-purity YFeO3 ceramics can be prepared using SPS, while the results from X-ray photoelectron spectroscopy (XPS) show that the concentration of oxygen vacancies resulting from transformation from Fe3+ to Fe2+ is low. The relative density of the 1000 °C-sintered sample is as high as 97.7%, which is much higher than those of the samples sintered at other temperatures. The present dielectric and magnetic properties are much better than those of the samples fabricated by conventional methods. These findings indicate that the YFeO3 ceramics prepared by the low temperature solid reaction and SPS methods possess excellent dielectric and magnetic properties, making them suitable for potential applications involving magnetic storage. © 2017 by the authors.

Wang J.,Harbin Institute of Technology | Song S.,Harbin Institute of Technology | Muchakayala R.,Harbin Institute of Technology | Hu X.,Harbin Institute of Technology | Liu R.,Tsinghua Innovation Center in Dongguan
Ionics | Year: 2017

Abstract: Ionic liquid-doped biodegradable gel polymer electrolyte membranes are currently new opportunities for rechargeable magnesium-ion batteries. In this work, poly(vinyl alcohol)/magnesium trifluoromethanesulfonate/1-ethyl-3-methylimidazolium trifluoromethanesulfonate (PVA/Mg(Tf)2/EMITf) membranes of different compositions are prepared by solution casting. The crystalline structure, morphology, ionic conductivity, electrochemical stability window, and thermal stability of the membranes are analyzed by various techniques. It is found that the pristine PVA membrane possesses a semi-crystalline structure and its degree of crystallinity declines with augmenting EMITf concentration. The room-temperature ion conductivity of the 85PVA:15Mg(Tf)2:15EMITf gel polymer electrolyte membrane exhibits a high value of 2.10 × 10−4 S cm−1. Meanwhile, this gel polymer electrolyte membrane shows a wide electrochemical stability window (~5 V) and the temperature dependence of ionic conductivity obeys the Arrhenius rule (Ea = 0.25 eV). Additionally, the mechanical properties of the electrolyte membrane are sufficiently high for its applications, being the following values: Young’s modulus = 33 MPa; breaking strain = 452%; yield strength = 4.8 MPa. This inexpensive and environment-friendly gel polymer electrolyte membrane could be a promising potential electrolyte material for Mg-ion battery applications. Highlights: 1.PVA-based biodegradable gel polymer electrolyte membranes are developed.2.The optimal membrane has a high room-temperature conductivity of 2.10 × 10−4 S cm−1.3.The temperature dependence of ionic conductivity obeys the Arrhenius rule.4.The membrane exhibits a wide electrochemical stability window (~5 V).5.The mechanical properties of the membrane are high enough for applications. © 2017 Springer-Verlag Berlin Heidelberg

Wu R.,Guangxi University for Nationalities | Zhao X.,Tsinghua University | Zhao X.,Tsinghua Innovation Center in Dongguan | Liu D.,Tsinghua University | Liu D.,Tsinghua Innovation Center in Dongguan
ACS Sustainable Chemistry and Engineering | Year: 2016

Enzymatic digestibility of sugar cane bagasse could be greatly enhanced by Formiline pretreatment, which comprises a formic acid (FA) delignification followed by an alkaline deformylation. The FA can be easily recovered and recycled for delignification, indicating that this pretreatment is a green process for biomass fractionation. It was found that removing hemicelluloses and lignin during pretreatment contributed to the increase of cellulose accessibility; however, delignification seemed to be more important for exposing cellulose fibers. The compact cell wall structure of raw bagasse was destroyed by removing considerable parts of lignin and hemicelluloses with liberation of cellulose fibers, and the specific surface area of the pretreated substrates increased by more than 2-fold. However, formylation of cellulose took place during FA delignification, which showed significant negative impact on the initial enzymatic hydrolysis rate and enzymatic polysaccharide conversion at 120 h. Removing formyl groups by alkaline post-treatment could well recover the cellulose digestibility but without significant alteration of the substrate structure. © 2016 American Chemical Society.

Xie Y.,Dongguan University of Technology | Cheng Z.,Dongguan University of Technology | Guo B.,Dongguan University of Technology | Qiu Y.,Dongguan University of Technology | And 5 more authors.
Ionics | Year: 2015

In this report, the activated carbon papers were prepared by the modified Hummer's method. After the treatment by the modified Hummer's method, the specific surface areas of carbon papers enlarged and the surfaces became wettability. Further, the electrochemical behaviors for the activated carbon papers were measured. They exhibit higher electrochemical activities for VO2+/VO2 + redox reaction than the unactivated counterparts upon application as vanadium redox battery, which is ascribed to the synergistic effect of surface wettability and catalysis of the docked -OH and -COOH groups. © 2014 Springer-Verlag.

Chen Z.,Tsinghua University | Chen Z.,Tsinghua Innovation Center in Dongguan | Sun H.,Tsinghua University | Huang J.,Tsinghua University | And 3 more authors.
PLoS ONE | Year: 2015

2-Butanone is an important commodity chemical of wide application in different areas. In this study, Klebsiella pneumoniae was engineered to directly produce 2-butanone from glucose by extending its native 2, 3-butanediol synthesis pathway. To identify the potential enzyme for the efficient conversion of 2, 3-butanediol to 2-butanone, we screened different glycerol dehydratases and diol dehydratases. By introducing the diol dehydratase from Lactobacillus brevis and deleting the ldhA gene encoding lactate dehydrogenase, the engineered K. pneumoniae was able to accumulate 246 mg/L of 2-butanone in shake flask. With further optimization of culture condition, the titer of 2-butanone was increased to 450 mg/L. This study lays the basis for developing an efficient biological process for 2-butanone production. © Copyright: 2015 Chen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Chen Z.,Tsinghua University | Chen Z.,Tsinghua Innovation Center in Dongguan | Huang J.,Tsinghua University | Wu Y.,Tsinghua University | And 2 more authors.
Metabolic Engineering | Year: 2016

Development of sustainable biological process for the production of bulk chemicals from renewable feedstock is an important goal of white biotechnology. Ethylene glycol (EG) is a large-volume commodity chemical with an annual production of over 20. million. tons, and it is currently produced exclusively by petrochemical route. Herein, we report a novel biosynthetic route to produce EG from glucose by the extension of serine synthesis pathway of Corynebacterium glutamicum. The EG synthesis is achieved by the reduction of glycoaldehyde derived from serine. The transformation of serine to glycoaldehyde is catalyzed either by the sequential enzymatic deamination and decarboxylation or by the enzymatic decarboxylation and oxidation. We screened the corresponding enzymes and optimized the production strain by combinatorial optimization and metabolic engineering. The best engineered C. glutamicum strain is able to accumulate 3.5. g/L of EG with the yield of 0.25. mol/mol glucose in batch cultivation. This study lays the basis for developing an efficient biological process for EG production. © 2015 International Metabolic Engineering Society.

Akimkulova A.,Tsinghua University | Zhou Y.,Tsinghua University | Zhao X.,Tsinghua University | Zhao X.,Tsinghua Innovation Center in Dongguan | And 2 more authors.
Bioresource Technology | Year: 2016

Eleven salts were selected to screen the possible metal ions for blocking the non-productive adsorption of cellulase onto the lignin of dilute acid pretreated wheat straw. Mg2+ was screened finally as the promising candidate. The optimal concentration of MgCl2 was 1 mM, but the beneficial action was also dependent on pH, hydrolysis time and cellulase loading. Significant improvement of glucan conversion (19.3%) was observed at low cellulase loading (5 FPU/g solid). Addition of isolated lignins, tannic acid and lignin model compounds to pure cellulose hydrolysis demonstrated that phenolic hydroxyl group (Ph-OH) was the main active site blocked by Mg2+. The interaction between Mg2+ and Ph-OH of lignin monomeric moieties followed an order of p-hydroxyphenyl (H) > guaiacyl (G) > syringyl (S). Mg2+ blocking made the lignin surface less negatively charged, which might weaken the hydrogen bonding and electrostatically attractive interaction between lignin and cellulase enzymes. © 2016 Elsevier Ltd.

Chen Z.,Tsinghua University | Chen Z.,Tsinghua Innovation Center in Dongguan | Wu Y.,Tsinghua University | Huang J.,Tsinghua University | And 2 more authors.
Bioresource Technology | Year: 2015

Butanol isomers are important bulk chemicals and promising fuel substitutes. The inevitable toxicity of n-butanol and isobutanol to microbial cells hinders their final titers. In this study, we attempt to engineer Klebsiella pneumoniae for the de novo production of 2-butanol, another butanol isomer which shows lower toxicity than n-butanol and isobutanol. 2-Butanol synthesis was realized by the extension of the native meso-2,3-butanediol synthesis pathway with the introduction of diol dehydratase and secondary alcohol dehydrogenase. By the screening of different secondary alcohol dehydrogenases and diol dehydratases, 320. mg/L of 2-butanol was produced by the best engineered K. pneumoniae. The production was increased to 720. mg/L by knocking out the ldhA gene and appropriate addition of coenzyme B12. Further improvement of 2-butanol to 1030. mg/L was achieved by protein engineering of diol dehydratase. This work lays the basis for the metabolic engineering of microorganism for the production of 2-butanol as potential biofuel. © 2015 Published by Elsevier Ltd.

Chen Z.,Tsinghua University | Chen Z.,Tsinghua Innovation Center in Dongguan | Liu D.,Tsinghua University | Liu D.,Tsinghua Innovation Center in Dongguan
Biotechnology for Biofuels | Year: 2016

As an inevitable by-product of the biofuel industry, glycerol is becoming an attractive feedstock for biorefinery due to its abundance, low price and high degree of reduction. Converting crude glycerol into value-added products is important to increase the economic viability of the biofuel industry. Metabolic engineering of industrial strains to improve its performance and to enlarge the product spectrum of glycerol biotransformation process is highly important toward glycerol biorefinery. This review focuses on recent metabolic engineering efforts as well as challenges involved in the utilization of glycerol as feedstock for the production of fuels and chemicals, especially for the production of diols, organic acids and biofuels. © 2016 The Author(s).

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