JOURNAL OF ALLOYS AND COMPOUNDS
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2019
·
IF 4.175
Yinglin Yan,Mangmang Shi,Yiming Zou,Yiqi Wei,Liping Chen,Chaojiang Fan,Rong Yang,Yunhua Xu
It had been proven that carbon aerogel (CA) can effectively improve the conductivity of sulfur (S) and suppress the shuttle effect of polysulfides in Li-S batteries, due to its outstanding electrical conductivity and micropore-rich structure. However, the microstructure of CA was easy to collapse and shrink during carbonization, resulting in a dramatically drop in specific surface area and porosity. Herein, graphene nanosheets (GNs) were introduced in CA to reinforce the structural stability. As-prepared CA/GNs composites were fabricated from in-situ polymerization of resorcinol (R) and formaldehyde (F) in graphene oxide (GO) solution. It was found that the mass concentration of the GO solution had a significantly positive effect on hierarchical porous structure of the CA/GNs composites, which presented improve the electrochemical performances due to the combination of micro-, meso- and macro-pores. It is worth noting that the CA/GNs0.1 sample, obtained from 10 wt % GO solution, possessed the largest specific surface area of 665.477 m 2 g −1 and the largest pore volume of 0.912 cm 3 g −1 . Especially, after incorporated with moderate amount of S (58.86 wt %), the CA/GNs0.1/S cathode exhibited the best electrochemical performances (initial discharging capacity of 1501 mAh g −1 at 0.1C and reversible capacities of 471 mAh g −1 after 100 cycles and 341 mAh g −1 after 500 cycles at 1C). This was attributed to the tunable hierarchical porous microstructure of the CA/GNs0.1 sample. Unfortunately, when increased the S content to 68.39 wt %, the electrochemical performance deteriorated in all aspects because of their sluggish reaction kinetics. These all results suggested that introducing GNs can feasibly enhance the performance of CA as matrix in Li-S batteries.
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高影响因子
POLYMER
·
2019
·
IF 3.771
Longfei Li,Hong Zhai,Tao Wang,Xibo Qiu,Na Qiang,Peng Dong,Ying Bai,Ai-Yun Peng,Daping Quan
The ring-opening copolymerization of lactide with carbonate is an available strategy to incorporate reactive groups to the pendent sites of copolymer for further functional modification. A series of random and block copolymers were synthesized from l -lactide ( L -LA) and 2-bromomethyl-2-methyltrimethylene carbonate (BMTC) using dodecanol as initiator and stannous octoate as catalyst. The structures of the copolymers were characterized by nuclear magnetic resonance ( 1 H NMR, 13 C NMR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The composition of the copolymers can be controlled through changing the feed ratios of n BMTC / n L -LA . It was found the random P(BMTC- co - L LA) copolymers had the semicrystalline characteristic due to the relative long block-like segments of P L LA ( L L , P L LA = 5.3–7.3) and the polar interactions from bromo groups , but their crystallinity ( X c, P L LA ) and melting temperature ( T m, P L LA ) decreased when the BMTC content increased. The X c, P L LA and T m, P L LA of P(BMTC- b -P L LA) block copolymers were relatively higher than the corresponding random copolymers, and approached gradually to the pure P L LA with the increase of the molecular weight of P L LA block. Finally, the pendent bromo groups of P(BMTC- co - L LA) were easily transformed into azides , which could proceed the azide-alkyne click reaction smoothly and quantitatively at room temperature .
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高影响因子
GREEN CHEMISTRY
·
2019
·Vol. 22
·期 3
·742-752
·
IF 9.405
Xiwei Hu,Xun Sun,Qiang Song,Yangyang Zhu,Yu Long,Zhengping Dong
Metal-free carbon catalysts with excellent catalytic performance have drawn much research attention recently. Herein, polymer-derived N,S co-doped carbon catalysts (PDNSC-X) with a hierarchically porous structure were facilely prepared by a cost-effective and convenient strategy via carbonization of a N- and S atom-containing polymer precursor and were subsequently used as efficient metal-free catalysts. The catalytic activity of the as-fabricated PDNSC-800 was greater than those of other reported heteroatom-doped carbon catalysts in catalytic reduction of various nitroarenes. The high catalytic activity of PDNSC-800 was related to the synergistic effects of a high surface area, a hierarchically porous structure, abundant N- and S-containing active sites, and defect formation. In addition, the close relationship between the N species (especially pyrrolic N) and high selectivity in metal-free catalytic synthesis was investigated in the reduction of nitroarenes and selective oxidation of ethylbenzene. This study may provide a new strategy to fabricate specific heteroatom-doped metal-free carbon catalysts for environmentally friendly efficient organic transformation.
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高影响因子
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
·
2019
·Vol. 21
·期 44
·24308-24315
·
IF 3.567
Leipeng Li,Xudong Qi,Feng Qin,Lu Li,Hong Gao,Yangdong Zheng,Zhiguo Zhang
A guideline for designing sensitive thermometry is proposed. It reveals that using two emission bands that possess the opposite change tendencies against temperature makes it easier to achieve a larger relative sensitivity. Based on the guidelines, a highly sensitive strategy for optical thermal detection that depends on the Tb3+-to-Eu3+ emission ratio is designed by exciting Eu3+/Tb3+'s unusual absorption lines. This can be easily driven by a commonly used and cheap 405 nm laser diode. Moreover, its maximum relative sensitivity reaches up to 2.02% K−1 at 610 K, one of the largest sensitivities reported so far.
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PubMed
高影响因子
ACS Applied Energy Materials
·
2018
·
IF 0
Xiaorong Gan,Lawrence Yoon Suk Lee,Kwok-yin Wong,Tsz Wing Lo,Kwun Hei Ho,Dang Yuan Lei,Huimin Zhao
The phase transition of multilayer MoS2 nanosheets from semiconducting 2H to metallic 1T (2H/1T) has been realized mainly by chemical methods (e.g., Li intercalation). Here, we develop a simple yet effective method, cyclic voltammetry, to successfully tune the 2H/1T phase transition of multilayer MoS2 nanosheets without using intercalation species. The phase transition is triggered by the electrochemical incorporation of S vacancies (obtained by electrochemical etching), which on the one hand injects electrons into the framework of S–Mo–S and on the other hand facilitates the sliding of S planes. Density functional theory calculations show that O doping in the framework of S–Mo–S decreases the energy barrier for forming S vacancies and stabilizes the 1T-phase by occupying the 4d orbital of Mo. Our calculations further show that the presence of S vacancies and O incorporation not only reduces the bandgap of MoS2, indicating an increased conductivity, but also decreases the hydrogen adsorption free energy, implying significant improvement of hydrogen evolution reaction (HER) activity. Indeed, the overpotential and Tafel plot of the electrochemically treated MoS2 nanosheets are decreased respectively by 174 mV and 25 mV/dec at a cathodic current density of 10 mA cm–2 compared with pristine 2H-MoS2 nanosheets. The HER experiment also reveals the order of catalytical activity for the studied phases and structural defects: 1T-MoS2 > S vacancies > O doping >2H-MoS2. Our study has provided a new route to control the phase transition of multilayer MoS2 nanosheets with promising applications potentially in catalysis and optoelectronics.
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Materials
·
2018
·Vol. 11
·期 9
·1720
·
IF 2.467
Qiuyan Hao,Guoliang Cui,Yuan Tian,Taizhe Tan,Yongguang Zhang
In this paper, the synthesis of the three-dimensional (3D) composite of spherical reduced graphene oxide (RGO) with uniformly distributed CeO2particles is reported. This synthesis is done via a facile and large-scalable spray-drying process, and the CeO2/RGO materials are hydrothermally compounded with sulfur. The morphology, composition, structure, and electrochemical properties of the 3D S/CeO2/RGO composite are studied using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), Raman spectra and X-ray photoelectron spectroscopy (XPS), etc. The electrochemical performance of the composites as electrodes for lithium–sulfur batteries is evaluated. The S/CeO2/RGO composites deliver a high initial capacity of 1054 mAh g−1, and retain a reversible capacity of 792 mAh g−1after 200 cycles at 0.1 C. Profiting from the combined effect of CeO2and RGO, the CeO2/RGO materials effectively inhibit the dissolution of polysulfides, and the coating of spherical RGO improves the structural stability as well as conductivity.Keywords:Lithium–sulfur battery;CeO2/RGO composite;electrochemical performance
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高影响因子
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
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2014
·
IF 3.107
Yan-Qing Wang,Hong-Mei Zhang
The effects of bisphenol S on the structures and activities of trypsin and pepsin were investigated by various methods like UV–visible absorbance, fluorescence, circular dichroism, and molecular docking. The secondary and tertiary structures of trypsin and pepsin were altered by bisphenol S binding, which resulted in the loosening of the skeletons of trypsin and pepsin. In addition, bisphenol S induced microenvironmental changes around tyrosine and tryptophan residues of trypsin and pepsin. The activity experimental results showed that the activity of pepsin decreases obviously with the increasing concentration of BPS, while the activity of trypsin does not change remarkably. The binding and thermodynamic parameters obtained by molecular docking and fluorescence spectroscopy showed that the bindings of bisphenol S to trypsin and pepsin were spontaneous processes and hydrogen bonding and hydrophobic interactions played a vital role in stabilizing the bisphenol S–trypsin and bisphenol S–pepsin complexes. The binding constants (KA) of bisphenol S with trypsin were 7.42 × 104 (298 K) and 5.91 × 104 L/mol (310 K), and those of pepsin were 5.78 × 104 (298 K) and 4.44 × 104 L/mol (310 K). Moreover, there was one main kind of binding site for bisphenol S on trypsin or pepsin.
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PubMed
高影响因子
JOURNAL OF POLYMER RESEARCH
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2014
·Vol. 21
·期 11
·1-8
·
IF 1.897
Ran Xiaoqi,Yi Shixiong,Liang Liefeng,Yang Xiao
The effect of oxygen on photodegradation of π-conjugated aromatic poly(1,3,4-oxadiazole)s (POD) was studied in detail. The results obtained by tensile test, UV-spectra and ATR-FTIR revealed that the oxygen was indispensable during photodegradation of POD. The occurrence of photodegradation of POD must be combination of UV exposure and oxygen simultaneously. The state of oxygen during photodegradation of POD was investigated by nitrotetrazolium blue chloride (NBT) method. The result illustrated that the oxygen was transformed into superoxide anion radical through accepting one electron during UV exposure. Results of tensile tests and UV-spectra further proved that the superoxide anion radical could combine with excited POD to form an unstable product that lead to occurrence of photodegradation. Singlet oxygen was also investigated and the result showed that POD appeared to be stable to singlet oxygen.
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高影响因子
Materials Research Express
·
2014
·Vol. 1
·期 1
·015033
·
IF 0
Yanyan Chen,Shenjie Li,Lijian Huang,Daocheng Pan
Au+ ions have been successfully incorporated into the lattice of ZnxCd1−xS quantum dots as luminescent centers via an aqueous method. The dopant emission can be tuned in the range of 445 to 570 nm, and the highest quantum yield can reach as high as 30%. Our results showed that Au+ ions can be used as an excellent luminescent dopant in doped quantum dots. Finally, these water-soluble quantum dots can be used directly in PL imaging of HepG2 cells without conjugating any biological targets, indicating a high potential application in bio-labeling.
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PROCESS BIOCHEMISTRY
·
2013
·
IF 2.414
Yuxiang Tang,Wei Liu,Jiangling Wan,Yuanxin Wang,Xiangliang Yang
We report the selective recovery of S-adenosylmethionine (SAM) from fermentation broths using a two-stage supported liquid membrane system with strip dispersion (SLM-SD). The system utilized two MiniModule ® hollow-fiber membrane modules as microporous supports and an organic membrane solution consisting of the extractants of sodium di-2-ethylhexyl sulfosuccinate (AOT), di-(2-ethylhexyl)phosphoric acid (DEHPA), and trioctylphosphine oxide (TOPO) in the solvent n-octanol. SAM was extracted in the first membrane module. Methionine (Met) was captured by the first stripping solution and further purified in the second membrane module. pH values in the feed phase and the first and second stripping solutions, extractant concentrations, NaCl concentration, and the SAM acceptor in the first stripping solution were optimized. Strip dispersion mixing speed, pressure differences across the membranes, and flow rates of the feed and strip dispersion phases were investigated experimentally. The optimal extractant concentrations were: AOT 2.78 wt%, DEHPA 27.0 wt%, and TOPO 1.61 wt%. The optimal pH values in the feed phase and the first and second stripping solution were 3.0, 2.5, and 1.0, respectively. SAM extraction efficiency of 98.7%, SAM recovery efficiency of 91.8% and Met removal efficiency of 85.4% were achieved within 5 h. Finally, the mass transfer analysis indicated that the mass transfer resistances from the extraction reaction and the membrane phase were predominant.
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高影响因子
APPLIED SURFACE SCIENCE
·
2014
·
IF 2.538
Yanlin Zhang,Peihong Liu,Honghai Wu
One-dimensional (1D) nanowire material (especially nonmetal doped 1D nanowires) synthesized by a facile way is of great significance and greatly desired as it has higher charge carrier mobility and lower carrier recombination rate. N, S-codoped TiO 2 nanowires were synthesized using titanium sulfate as a precursor and isopropanol as a protective capping agent by a hydrothermal route. The obtained doped nanowires were characterized by XRD, SEM, HRTEM, SAED, XPS, BET and UV–vis absorption spectrum. The incorporation of N and S into TiO 2 NWs can lead to the expansion of its lattice and remarkably lower its electron-transfer resistance. Photocatalytic activity measurement showed that the N, S-codoped TiO 2 nanowires with high quantum efficiency revealed the best photocatalytic performance for atrazine degradation under visible light irradiation compared to N, S-codoped TiO 2 nanoparticles and S-doped TiO 2 nanowires, which was attributed to (i) the synergistic effect of N and S doping in narrowing the band gap, separating electron–hole pairs and increasing the photoinduced electrons, and (ii) extending the anatase-to-rutile transformation temperature above 600 °C.
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高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
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2014
·
IF 2.235
Qiheng Tang,Rongjie Yang,Yun Song,Jiyu He
A series of flame-retarded thermoplastic poly(imide–urethane)s (TPIUs) with either ammonium polyphosphate (APP) alone or APP and dipentaerythritol (DPER) have been prepared. The fracture strength and strain of TPIU composites decrease with increasing amount of intumescent flame retardant (IFR), as shown by tensile tests. Thermogravimetric analysis shows that the initial decomposition temperature (T5%) of TPIU composites decreases with increasing IFR loading. The flame retardancies of these TPIU composites have also been tested according to the limiting oxygen index (LOI) and UL-94 standards. The results have indicated that the LOI value of TPIU/APP is a little higher than that of TPIU/(APP + DPER) with the same loading. Furthermore, 50% APP alone or APP + DPER incorporation into TPIU allowed attainment of the UL-94 V-0 standard. Details of fire behavior, such as time to ignition, heat release rate, peak of the heat release rate, total smoke release, and total heat release, have been tested by means of a cone calorimeter. Moreover, the char residues of TPIU composites after cone calorimetry have been investigated in detail by scanning electron microscopy, Fourier transform infrared, and energy-dispersive X-ray reflectometry.
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高影响因子
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