Catalysis Science & Technology
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2014
·Vol. 4
·期 5
·1286-1292
·
IF 4.76
Bing Liu,Ting Huang,Zehui Zhang,Zheng Wang,Yuhua Zhang,Jinlin Li
The present study reported the results on the water–gas shift (WGS) reaction over a series of Ru/C catalysts. It was found that the reduction method showed a remarkable effect on the catalytic activity of Ru/C catalysts over WGS reaction, which increased in an order of the reduction by NaBH4, ethylene glycol, H2. It has been shown that alkali additives with K2CO3 significantly improved the activity of the Ru/C catalysts. XPS results indicated that Ru species were further oxidized by the addition of K2CO3, which indicated an electron transfer from the alkali metal to the substrate, resulting in stronger bonding of the adsorbed gas. FTIR results showed that the absorption peak intensity of H2O and hydroxyl group increased with the increase of K2CO3 content, due to the strong hygroscopic ability of K2CO3. Through the addition of K2CO3 to the Ru/C catalyst, much more water was adsorbed around the catalytic active sites, reducing the strong adsorption of CO on the active sites. Thus the addition of K2CO3 balanced the concentration of water and CO on the active sites, which was considered to be the key step for low temperature WGS reaction over Ru supported on irreducible activated carbon.
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ORGANIC & BIOMOLECULAR CHEMISTRY
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2014
·Vol. 12
·期 18
·2969-2978
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IF 3.487
Jiajun Zhang,Pinhua Li,Lei Wang
A novel KOAc-promoted α-position C–H activation and alkynylation of ethers with alkynyl bromides to 2-alkynyl ethers has been developed under transition-metal-free and simple reaction conditions. In addition, this methodology can also be extended to the vinylation of ethers with vinyl bromides in excellent regio- and stereo-selectivity. A wide range of direct C(sp)–C(sp3) and C(sp2)–C(sp3) bonds has been formed through this protocol, which offers a new and alternative route.
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Chinese Journal of Natural Medicines
·
2015
·
IF 1.114
Chong-Ye FANG,Xuan-Jun WANG,Ye-Wei HUANG,Shu-Mei HAO,Jun SHENG
The present study was designed to determine the effects of Puer tea and green tea on blood glucose level. Male BALB/c mice were administered green tea extract (GTE) or Puer tea extract (PTE), either intragastrically or in their drinking water. The major components of these teas are epigallocatechin gallate (EGCG) and caffeine, respectively. Blood glucose measurement results showed that mice fed intragastrically or mice that drank GTE, PTE or caffeine showed significantly lower blood glucose levels compared to the control group. However, EGCG exhibited no influence on the blood glucose levels. When caffeine was eliminated from the GTE and PTE, the effect on the blood glucose levels was abolished, but the effect was recovered when caffeine was re-introduced into the extracts. Evaluation of hematological and biochemical indices at the time of the greatest caffeine-induced decrease in blood glucose levels showed that the effect of caffeine was specific. Microarray analyses were performed in 3T3-L1 preadipocytes and mature adipocytes treated with 0.1 mg·mL −1 caffeine to identify factors that might be involved in the mechanisms underlying these effects. The results showed that few genes were changed after caffeine treatment in adipocytes, and of them only phospholipid transfer protein (PLTP) may be ralated to blood glucose. In conclusion, this study indicates that caffeine may be the key constituent of tea that decreases blood glucose levels, and it may be used to treat type 2 diabetes.
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JOURNAL OF APPLIED PHYSICS
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2015
·Vol. 117
·期 24
·
IF 2.183
Yang Yimin,Du Deyang,Kong Fan,Fan Jiyang,Qiu Teng
Indium-tin-oxide (ITO) nanoparticles were annealed in vacuum or reducing atmosphere to obtain different surface structures and investigate their influence on the adsorptive character and conformation of cytochrome c (Cyt c ) molecule. Annealing-induced morphometric or structural changes of ITO nanoparticles were characterized by instruments of transmission electron microscopy, x-ray diffraction, and Raman scattering. Semiconductor ITO nanoparticle-enhanced Raman scattering of Cyt c was observed and the enhanced efficiency was found to closely depend on the surface structures which control the adsorbance of buffer anions needed for Cyt c loading. Direct electron transfer between Cyt c and ITO surface at the moment of molecular elastic collision was found and a reverse electron transfer process for O-terminated surface and metal-terminated surface was observed, according to absorption spectroscopic measurement on the residual solution.
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ANALYTICAL CHEMISTRY
·
2015
·
IF 5.636
Wei Zhang,Wei Liu,Ping Li,Fang Huang,Hui Wang,Bo Tang
Hydrogen peroxide (H2O2) as a reactive oxygen species (ROS) plays a crucial role in oxidative stress and signal transduction of organisms. Currently, a fluorescence probe has proven to be a powerful tool for the H2O2 analysis. However, the common problem is the slow response, causing difficulty in tracking H2O2 in situ. Herein, we describe a novel aggregation-induced emission (AIE) fluorescence probe based on increased polarity of C–B bonds that is well suited for monitoring H2O2 rapidly and selectively. Importantly, the probe was successfully applied to visualize H2O2 levels in living cells, which provides a rapid-response and highly selective fluorescence tool for monitoring of the H2O2 levels in biological process.
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ELECTROCHIMICA ACTA
·
2015
·
IF 4.504
Xing Xu,Yunlong Xu,Huang Zhang,Mandi Ji,Hui Dong
The NiO doped LiFePO 4 /C composite was synthesized by a simple solid state method. The structure and morphology of synthesized particles were characterized by XRD, Raman spectrum , SEM, TEM and EDS. Electrochemical performance of the pristine and nickel oxide modified samples was evaluated by galvanostatic charge-discharge test, CV , and EIS . The results indicate that NiO doped LiFePO 4 /Li type coin cell exhibits improved specific capacity and cycle stability, especially at high rates. Among all the modified samples, the 5.0%wt NiO doped sample shows the best electrochemical performance, which achieves a specific capacity of 129 mA h g −1 at 1 C current rate due to the modest graphitization of carbon layer on the surface of LiFePO 4 particles. The results indicate that nickel oxide modification is an effective way to improve the electrochemical performance of LiFePO 4 /C cathode materials for lithium ion batteries .
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JOURNAL OF POWER SOURCES
·
2013
·
IF 4.675
Yuan Wang,Haibo Rong,Benzhen Li,Lidan Xing,Xiaoping Li,Weishan Li
Ultrafine Li 4 Ti 5 O 12 /C composite is synthesized by microemulsion with oleic acid as carbon precursor and particle size controller. The as-prepared sample is characterized with X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), thermogravimetry analysis (TGA) and nitrogen absorption–desorption isotherms, and its performance as anode of lithium ion battery is determined with charge–discharge test and electrochemical impedance spectroscopy (EIS). The characterizations show that the as-prepared sample is composed of ultrafine Li 4 Ti 5 O 12 particles with average size of 25 nm, which are uniformly dispersed in carbon matrix with a carbon content as low as 2.69 wt%. Charge–discharge test indicates that the as-prepared sample exhibits excellent rate performance and cycling stability. At 10C, the highest discharge capacity reaches 136.3 mAh g −1 and the capacity retention is 96.4% after 100 cycles. The improved performance of the Li 4 Ti 5 O 12 /C composite is attributed to the ultrafine particle size and the uniform composite of Li 4 Ti 5 O 12 with carbon.
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CHEMICAL ENGINEERING JOURNAL
·
2015
·
IF 4.321
Lei Yue,Guangqian Li,Guijin He,Yongsheng Guo,Li Xu,Wenjun Fang
The precise investigations on modeling properties and performance of practical fuels are usually complicated because of the multi-component nature. On the basis of hydrogen to carbon ratio (H/C), as a simple and overall characterization parameter for hydrocarbon fuels, this work provides a comprehensive insight into the study of kerosene-based hydrocarbon fuels (H/C = 1.6–2.3). The fundamental properties and supercritical cracking performance of hydrocarbon fuels are influenced intrinsically by their H/C values and molecular weights ( M ) due to the compositional and structural effects. Thus, a new combined parameter, (H/C)/ M a , is proposed to model the performance of hydrocarbon fuels. It is found that the hydrocarbon fuel with a higher H/C has a higher net heating value, and that with a higher (H/C)/ M 0.1 has a lower density. The viscosity decreases with the increase of (H/C)/ M 0.5 . The flash point shows a decreasing trend against the increase of (H/C)/ M 2 . The densities, viscosities and net heating values of 23 hydrocarbon fuels are calculated by means of the regression equations with the H/C and M data, and they are in agreement with the corresponding experimental values with the relative errors less than 2.5%, 10% and 1.5%, respectively. As investigated in an electrically heated tube reactor, the hydrocarbon fuel with a higher H/C performs thermal cracking more easily, absorb more heat and form fewer cokes. As a result, the cracking performance of hydrocarbon fuels can be predicted reasonably to a certain extent on the basis of H/C values.
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Nanoscale
·
2013
·Vol. 5
·期 16
·7564-7571
·
IF 6.233
Jie Sun,Haimei Liu,Xu Chen,David G. Evans,Wensheng Yang
Superposed cobalt(II)–cobalt(III) layered double hydroxide (CoII–CoIII-LDH) nanoplates were synthesized by an oil droplet template method, in which the main steps are as follows: LDH nanosheets were first assembled on an oil droplet template to form a multishell sphere, and then the oil droplet was easily removed under centrifugal force due to its very different density from that of the assembled LDH shell. This resulted in the multishell spheres being split open to create superposed LDH nanoplates. The resulting material has a three-stage architecture, namely, the primary building blocks of nanosheets, the secondary architecture of shells derived from the nanosheets, and the long-range architecture of superposed nanoplates assembled from the vertically stacked shells. Most importantly, the as-fabricated LDH-based hierarchical structure can be readily converted to a Co3O4/C composite via calcination, without obvious structural alteration, where the residual surfactant is the source of the carbon. When used as an anode material for Li-ion batteries, the Co3O4/C electrode exhibits an excellent electrochemical performance, which is attributed to the unique hierarchically porous structure.
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COLLOIDS AND SURFACES B-BIOINTERFACES
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2015
·
IF 4.152
Jixiang Zhu,Fanwen Yang,Fupo He,Xiumei Tian,Shuo Tang,Xiaoming Chen
A tubular gelatin scaffold for the time-dependent controlled release of epidermal growth factor (EGF) and mitomycin C (MMC) was fabricated. EGF was incorporated using silk fibroin carriers, and MMC was planted using polylactide (PLA) microspheres. The relationship between scaffold properties and crosslinking degrees was evaluated. As the crosslinking degree was increased from 23.7% to 65.3%, the mechanical properties of the scaffold obviously improved, and the compressive modulus increased to approximately 65 kPa. The mass degradation of the scaffold was also controlled from 9 days to approximately 1 month. In vitro release tests indicated that the scaffold mainly released EGF in the early period and MMC in the later period. Urethral epithelial cells (UECs) and urethral scar derived fibroblast cells (UFCs) were coseeded in the scaffold at a ratio of 1:1. After 9 days of coculture, immunostaining results displayed that the proportion of UECs continuously increased to approximately 71%. These changes in cell proportion were confirmed by the results of Western blot analysis. Therefore, the scaffold promoted the growth but inhibited the regeneration of UFCs. This scaffold for time-dependent controlled release of multiple biofactors may be potentially useful in urethral reconstruction and other tissue engineering studies.
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ELECTROCHIMICA ACTA
·
2014
·
IF 4.086
Mingjia Han,Muwu Li,Xin Wu,Jianhuang Zeng,Shijun Liao
Motivated by addressing the support corrosion or stability issue for electro-catalysts, a carbon composite support has been prepared by wet-impregnation of nano-sized TiO 2 and cobalt (II) acetate tetrahydrate together with XC-72 carbon black, followed by thermal treatment at 900 °C in a reductive atmosphere. Decomposition of cobalt acetate under thermal treatment yields TiO 2 -Co 3 O 4 -C composite support (CS), as is confirmed by X-ray diffraction analysis. The composite support is found to be more corrosion resistant and stable in acidic solution than that of the conventionally used carbon black, as is witnessed by the chronoamperometric response. This composite support is then used to load 40.3 wt.% Pt nanoparticles (Pt/CS) as an electro-catalyst for proton exchange membrane fuel cells. It is found that 27.9% of the electrochemical surface area (ECSA) retained in an accelerated stability test (AST) in 0.5 M H 2 SO 4 for Pt/CS, compared with 8.4% for 39.5 wt.% Pt catalyst supported on XC-72 carbon black. The TEM image after AST for Pt/CS also confirms its improved resistance to agglomeration. The Pt/CS catalyst shows higher mass-normalized activity for methanol oxidation in 0.5 M CH 3 OH + 0.5 M H 2 SO 4 and a slower activity decay relative to that of the benchmarked Pt catalyst on carbon.
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CHINESE JOURNAL OF CATALYSIS
·
2017
·
IF 2.813
Na Huo,Hong Ma,Xinhong Wang,Tianlong Wang,Gang Wang,Ting Wang,Leilei Hou,Jin Gao,Jie Xu
ABSTRACT From both fundamental and practical perspectives, the production of chemicals from biomass resources using high-efficiency non-precious metal catalysts is important. However, many processes require addition of stoichiometric or excess quantities of base, which leads to high energy consumption, leaching problems, and side reactions. In this study, we investigated the high-efficiency oxidative esterification of furfural to methylfuroate by molecular oxygen with a Co-N-C/MgO catalyst. The catalyst was prepared by direct pyrolysis of a cobalt(II) phenanthroline complex on MgO at 800 °C under N 2 atmosphere. From furfural, 93.0% conversion and 98.5% selectivity toward methylfuroate were achieved under 0.5 MPa O 2 with reaction at 100 °C for 12 h without a basic additive. The conversion and selectivity were much higher than those obtained with cobalt catalysts produced by pyrolysis of a cobalt(II) phenanthroline complex on activated carbon or typical basic supports, including NaX, NaY, and CaO. X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and experimental results revealed that the high efficiency of Co-N-C/MgO for production of methylfuroate was closely related to the cobalt-nitrogen-doped carbon species and its catalytic ability in hydrogen abstraction. In contrast, Co-N-C(HCl) that synthesized by removing MgO with HCl from Co-N-C/MgO, as the catalyst produced mainly an acetal as a condensation product, and chloride ions had a negative effect on the oxidative esterification. Although the catalytic performance of the cobalt-nitrogen-doped carbon species was greatly affected by HCl treatment, it could be recovered to a great extent by addition of MgO. Moreover, changes in the oxygen pressure hardly affected the oxidative esterification of furfural with Co-N-C/MgO. This study not only provides an effective approach to prepare methylfuroate, but also for designing high-performance non-precious metal catalysts for the oxidative esterification of biomass-derived compounds.
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