[Objective] This study aimed to provide basis for exploring the antimicrobial activity of capsaicin from different Capsicum cultivars and different locations in the same Capsicum fruit. [Method] Capsaicin was extracte...[Objective] This study aimed to provide basis for exploring the antimicrobial activity of capsaicin from different Capsicum cultivars and different locations in the same Capsicum fruit. [Method] Capsaicin was extracted from pericarp and seeds of three Capsicum cultivars using the alkaline ethanol extraction method. The antimicro- bial activities of capsaicin against Staphylococcus aureus, Saccharomyces cerevisiae and Asergillus niger were also studied. [Result] Capsaicin content in the ethanol ex- tracts of three Capsicum fruit followed： C. annuum L. var. conoides〉C, annuum L.〉C. annuum L. var. Iongum, and the capsaicin content in pericarp was 1.5-3.9 times that in seeds. Within the concentration range designed in this experiment （0.5-1.5 mg/ ml）, antimicrobial activities of the ethanol extracts from fruits of three Capsicum culfi- vars against the three experimental strains were obvious, with the highest antimicro- bial activity in C. annuum L., and similar antimicrobial activity in C. annuum L var. Iongum and C. annuum L, var. conoides. [Conclution] Both pericarp and seeds of three Capsicum cultivars contained capsaicinoids with high broad-spectrum antimicrobial activity.展开更多
Fe_2O_3 nanorods and hexagonal nanoplates were synthesized and used as the promoters for Pt electrocatalysts toward the methanol oxidation reaction（MOR） in an alkaline electrolyte.The catalysts were characterized by...Fe_2O_3 nanorods and hexagonal nanoplates were synthesized and used as the promoters for Pt electrocatalysts toward the methanol oxidation reaction（MOR） in an alkaline electrolyte.The catalysts were characterized by scanning electron microscopy,transmission electron microscopy,X-ray diffraction,X-ray photoelectron spectroscopy,cyclic voltammetry and chronoamperometry.The results show that the presence of Fe_2O_3 in the electrocatalysts can promote the kinetic processes of MOR on Pt,and this promoting effect is related to the morphology of the Fe_2O_3 promoter.The catalyst with Fe_2O_3 nanorods as the promoter（Pt-Fe_2O_3/C-R） exhibits much higher catalytic activity and stability than that with Fe_2O_3 nanoplates as the promoter（Pt-Fe_2O_3/C-P）.The mass activity and specific activity of Pt in a Pt-Fe_2O_3/C-R catalyst are 5.32 A/mgpt and 162.7 A/m^2_（Pt）,respectively,which are approximately 1.67 and 2.04 times those of the Pt-Fe_2O_3/C-P catalyst,and 4.19 and 6.16 times those of a commercial PtRu/C catalyst,respectively.Synergistic effects between Fe_2O_3 and Pt and the high content of Pt oxides in the catalysts are responsible for the improvement.These findings contribute not only to our understanding of the MOR mechanism but also to the development of advanced electrocatalysts with high catalytic properties for direct methanol fuel cells.展开更多
Acetol is a major light oxygenate and readily produced from staged or fast pyrolysis of lignocellulose biomass. Herein we report that acetol can be selectively converted to methyl pyruvate, an important fine chemical,...Acetol is a major light oxygenate and readily produced from staged or fast pyrolysis of lignocellulose biomass. Herein we report that acetol can be selectively converted to methyl pyruvate, an important fine chemical, through oxidative esterification over Au-based catalysts. Detailed experimental studies showed that Au on amphoteric supports with appropriate strength and balanced ratio of acid and base sites can facilitate the desired oxidative-esterification pathway without accelerating undesired aldol-condensation or Cannizzaro reactions. In particular, hydroxyapatite (with a Ca/P ratio of 1.62) supported Au achieved 87% selectivity to methyl pyruvate at an acetol conversion of 62%.展开更多
A new method for the fabrication of carbon aerogels is reported in this paper. Resorcinol and furfural were gelated in isopropanol with basic catalysts and then dried directly under isopropanol supercritical condition...A new method for the fabrication of carbon aerogels is reported in this paper. Resorcinol and furfural were gelated in isopropanol with basic catalysts and then dried directly under isopropanol supercritical condition, followed by carbonization under nitrogen atmosphere. The bulk densities of carbon aerogels obtained are in the range of 0.21g/cm3~0.27g/cm3 and the sizes of the interconnected carbon nano-particles are in the range of 20nm^30nm. All of the aerogel samples exhibit high BET surface areas in the range of 730m2/g^900m2/g. The bulk density, micro-pore volume, meso-pore volume and meso-pore diameter can be controlled by gelation conditions such as R/I ratio and R/C ratio.展开更多
A Michael addition is usually taken as a base-catalysed reaction. However, our synthesized 2-（quinolin-2-ylmethylene） malonic acid （QMA） as a Michael-type thiol fluorescent probe is acid-active in its sensing reac...A Michael addition is usually taken as a base-catalysed reaction. However, our synthesized 2-（quinolin-2-ylmethylene） malonic acid （QMA） as a Michael-type thiol fluorescent probe is acid-active in its sensing reaction. In this work, based on theoretic calculation and experimental study on 7-hydroxy-2-（quinolin-2-ylmethylene） malonic acid, we demonstrated that QMA as a Michael acceptor is acid-activatable, i.e., it works only in solutions at pH〈7, and the lower the pH of solutions is, the higher reactivity QMA has. In alkaline solution, the malonate QMA[-2H＋]2- cannot react with both RSand RSH. In contrast, 2-（quinolin-2- ylmethylene） malonic ester （QME）, the ester of QMA, reveal a contrary pH effect on its sensing reaction, that is, it can sense thiols in alkaline solutions but not in acidic solutions, like a normal base-catalysed Michael addition. The values of activation enthalpies from theoretic calculation support the above sensing behavior of two probes under different pH conditions. In acidic solutions, the protonated QMA is more highly reactive towards electrophilic attack over its other ionized states in neutral and alkaline solutions, and so can react with lowly reactive RSH. In contrast, there is a big energy barrier in the interaction of QME with RSH （acidic solutions）, and the reaction of QME with the highly reactive nucleophile RS- is a low activation energy process （in alkaline solutions）. Theoretic calculation reveals that the sensing reaction of QMA undergoes a 1,4-addition process with neutral thiols （RSH）, and a 1,2-addition pathway for the sensing reaction of QME with RS-. Therefore, the sensing reaction of QMA is an acid-catalysed Michael addition via a 1,4-addition, and a normal base-catalysed Michael addition via a 1,2-addition.展开更多
A series of Ni based catalysts with different supports and basic additives were prepared by sequential impregnation method. The catalysts were characterized by XRD, BET, H2-TPR and CO2-TPD techniques. It was found tha...A series of Ni based catalysts with different supports and basic additives were prepared by sequential impregnation method. The catalysts were characterized by XRD, BET, H2-TPR and CO2-TPD techniques. It was found that the introduction of basic additives enhanced the basicities of catalyats and promoted the dispersities of Ni particles by strong interaction between Ni2＋ and basic additives. Among the Ni based catalysts, 10%Ni/10%La203/ZrO2 showed the superior performance in sorbitol hydrogenolysis. The synergistic effect of Ni and La203 was proven to play an essential role in selective synthesis of EG and 1,2-PG. In the optimal reaction condition, the catalyst presented 100% sorbitol conversion and over 48% glycols （EG and 1,2-PG） yield. The kinetics study of polyols （sorbitol, xylitol and glycerol） hydrogenolysis showed that polyols with more hydroxyl number have higher activity and products distribution was final results of kinetic balance, which could give us some inspiration abeut how to change the products selectivity.展开更多
In this study, the heteroatom classes and molecular structures of nitrogen compounds in vacuum residue arecharacterized by the electrospray ionization （ESI） Fourier transform ion cyclotron resonance mass spectromet...In this study, the heteroatom classes and molecular structures of nitrogen compounds in vacuum residue arecharacterized by the electrospray ionization （ESI） Fourier transform ion cyclotron resonance mass spectrometry （FT-ICRMS） combined with the Fourier transform infrared （FT-IR） spectroscopy. The results demonstrate that three basic nitrogencompounds, N1 （in which a molecule contains one nitrogen atom, similarly hereinafter）, N1O1 and N2, are identified bytheir positive-ion mass spectra, and three non-basic nitrogen compounds, N1, N1O1, and N1S1, are characterized by theirnegative-ion mass spectra. Among these nitrogen compounds, the N1 class species are the most predominant. Combinedwith the data of ESI FT-ICR MS and FT-IR, the basic N1 class species are likely alkyl quinolines, naphthenic quinolines,acridines, benzonacridines, while the abundant non-basic N1 class species are derivatives of benzocarbazole. In comparisonwith CGO, the N1 basic nitrogen compounds in VR exhibit a higher average degree of condensation and have much longeralkyl side chains.展开更多
The electrooxidation of ethylene glycol(EG) on the surface of gold nanoparticles(AuNPs) in alkaline medium was investigated.AuNPs were electrodeposited on pencil graphite(PG) by fast scan cyclic voltammetry.Different ...The electrooxidation of ethylene glycol(EG) on the surface of gold nanoparticles(AuNPs) in alkaline medium was investigated.AuNPs were electrodeposited on pencil graphite(PG) by fast scan cyclic voltammetry.Different sizes of AuNPs deposited on the surface of PG(AuNPs/PG) were used for the electrooxidation process.AuNPs were electrodeposited on PG at various deposition times in the same potential range but with different scan rates and scan cycles.Scanning electron microscopy(SEM),transmission electron microscopy(TEM) and X-ray diffraction(XRD) were used to visualize and characterize the prepared AuNPs/PG electrodes.Cyclic voltammograms were also used to investigate the electrooxidation of EG.The effects of EG and supporting electrolyte concentrations,scan rate,particle size of AuNPs and final potential limit on the electrooxidation process have been investigated.Further studies showed that the electrooxidation of EG is affected by temperature of the medium.The prepared AuNPs showed stability after long-term use.展开更多
The synthesis of surface composition-tunable Pt-based octahedral nanoalloys is key to unravel the structureproperty relationship in fuel cells. Herein, we report a facile route to prepare composition-tunable Pt Cu oct...The synthesis of surface composition-tunable Pt-based octahedral nanoalloys is key to unravel the structureproperty relationship in fuel cells. Herein, we report a facile route to prepare composition-tunable Pt Cu octahedral nanoalloys by using halogen ions(Br-or/and I-) as composition modulators. Among these Pt Cu octahedral nanoalloys,Pt59 Cu41 octahedron exhibits the highest catalytic activity and durability in alkaline solution. The specific activity/mass activity of Pt59 Cu41 octahedron is 20.25 m A cm^-2/3.24 A mg^-1 Pt,which is 6.64/5.3 times higher than commercial Pt black in 0.5 mol L^-1 CH3 OH, respectively. In the case of using ethanol(0.5 mol L^-1) as fuel source, Pt59 Cu41 octahedron shows much better catalytic activity, that is 34.84 m A cm^-2/5.58 A mg^-1 Pt for specific activity/mass activity, which is 9.16/7.34 times higher than commercial Pt black, respectively. In situ Fourier transform infrared spectroscopy is employed to detect the intermediate species and products for methanol/ethanol oxidation reaction and a plausible mechanism is proposed to explain the improved activity and durability of Pt59 Cu41 octahedron toward methanol/ethanol oxidation in alkaline medium.展开更多
基金Supported by the Research Project for the Teaching Reform and Quality Construction of State Ethnic Affairs Commission(11005)Reform Project for Professional Training Mode in Basic Subjects of Beijing(2011)Undergraduate Research Training Program of Minzu University of China(URTP2011110085)~~
文摘[Objective] This study aimed to provide basis for exploring the antimicrobial activity of capsaicin from different Capsicum cultivars and different locations in the same Capsicum fruit. [Method] Capsaicin was extracted from pericarp and seeds of three Capsicum cultivars using the alkaline ethanol extraction method. The antimicro- bial activities of capsaicin against Staphylococcus aureus, Saccharomyces cerevisiae and Asergillus niger were also studied. [Result] Capsaicin content in the ethanol ex- tracts of three Capsicum fruit followed： C. annuum L. var. conoides〉C, annuum L.〉C. annuum L. var. Iongum, and the capsaicin content in pericarp was 1.5-3.9 times that in seeds. Within the concentration range designed in this experiment （0.5-1.5 mg/ ml）, antimicrobial activities of the ethanol extracts from fruits of three Capsicum culfi- vars against the three experimental strains were obvious, with the highest antimicro- bial activity in C. annuum L., and similar antimicrobial activity in C. annuum L var. Iongum and C. annuum L, var. conoides. [Conclution] Both pericarp and seeds of three Capsicum cultivars contained capsaicinoids with high broad-spectrum antimicrobial activity.
基金supported by the National Natural Science Foundation of China(21403125,21403124)the Scientific Research Foundation for the Outstanding Young Scientist of Shandong Province(BS2011NJ009)~~
文摘Fe_2O_3 nanorods and hexagonal nanoplates were synthesized and used as the promoters for Pt electrocatalysts toward the methanol oxidation reaction（MOR） in an alkaline electrolyte.The catalysts were characterized by scanning electron microscopy,transmission electron microscopy,X-ray diffraction,X-ray photoelectron spectroscopy,cyclic voltammetry and chronoamperometry.The results show that the presence of Fe_2O_3 in the electrocatalysts can promote the kinetic processes of MOR on Pt,and this promoting effect is related to the morphology of the Fe_2O_3 promoter.The catalyst with Fe_2O_3 nanorods as the promoter（Pt-Fe_2O_3/C-R） exhibits much higher catalytic activity and stability than that with Fe_2O_3 nanoplates as the promoter（Pt-Fe_2O_3/C-P）.The mass activity and specific activity of Pt in a Pt-Fe_2O_3/C-R catalyst are 5.32 A/mgpt and 162.7 A/m^2_（Pt）,respectively,which are approximately 1.67 and 2.04 times those of the Pt-Fe_2O_3/C-P catalyst,and 4.19 and 6.16 times those of a commercial PtRu/C catalyst,respectively.Synergistic effects between Fe_2O_3 and Pt and the high content of Pt oxides in the catalysts are responsible for the improvement.These findings contribute not only to our understanding of the MOR mechanism but also to the development of advanced electrocatalysts with high catalytic properties for direct methanol fuel cells.
基金supported by the National Natural Science Foundation of China(91545114,91545203,and 21576227)the 985 Program of the Chemistry and Chemical Engineering disciplines of Xiamen University~~
文摘Acetol is a major light oxygenate and readily produced from staged or fast pyrolysis of lignocellulose biomass. Herein we report that acetol can be selectively converted to methyl pyruvate, an important fine chemical, through oxidative esterification over Au-based catalysts. Detailed experimental studies showed that Au on amphoteric supports with appropriate strength and balanced ratio of acid and base sites can facilitate the desired oxidative-esterification pathway without accelerating undesired aldol-condensation or Cannizzaro reactions. In particular, hydroxyapatite (with a Ca/P ratio of 1.62) supported Au achieved 87% selectivity to methyl pyruvate at an acetol conversion of 62%.
基金The National Natural Science Foundation of China (No. 59973028), The Team Project of the Natural Science Foundation of Guangdong (No.[( )(20003038)]), and The Talent Training Program Foundation of the Higher Education Departmen
文摘A new method for the fabrication of carbon aerogels is reported in this paper. Resorcinol and furfural were gelated in isopropanol with basic catalysts and then dried directly under isopropanol supercritical condition, followed by carbonization under nitrogen atmosphere. The bulk densities of carbon aerogels obtained are in the range of 0.21g/cm3~0.27g/cm3 and the sizes of the interconnected carbon nano-particles are in the range of 20nm^30nm. All of the aerogel samples exhibit high BET surface areas in the range of 730m2/g^900m2/g. The bulk density, micro-pore volume, meso-pore volume and meso-pore diameter can be controlled by gelation conditions such as R/I ratio and R/C ratio.
基金This work is supported by the National Natural Science Foundation of China （No.21272224）, the Open Research Fund of State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University （No.201410）, and the Open Research Fund of Key Laboratory of Advanced Scientific Computation, Xihua University （No.szjj2013-024）.
文摘A Michael addition is usually taken as a base-catalysed reaction. However, our synthesized 2-（quinolin-2-ylmethylene） malonic acid （QMA） as a Michael-type thiol fluorescent probe is acid-active in its sensing reaction. In this work, based on theoretic calculation and experimental study on 7-hydroxy-2-（quinolin-2-ylmethylene） malonic acid, we demonstrated that QMA as a Michael acceptor is acid-activatable, i.e., it works only in solutions at pH〈7, and the lower the pH of solutions is, the higher reactivity QMA has. In alkaline solution, the malonate QMA[-2H＋]2- cannot react with both RSand RSH. In contrast, 2-（quinolin-2- ylmethylene） malonic ester （QME）, the ester of QMA, reveal a contrary pH effect on its sensing reaction, that is, it can sense thiols in alkaline solutions but not in acidic solutions, like a normal base-catalysed Michael addition. The values of activation enthalpies from theoretic calculation support the above sensing behavior of two probes under different pH conditions. In acidic solutions, the protonated QMA is more highly reactive towards electrophilic attack over its other ionized states in neutral and alkaline solutions, and so can react with lowly reactive RSH. In contrast, there is a big energy barrier in the interaction of QME with RSH （acidic solutions）, and the reaction of QME with the highly reactive nucleophile RS- is a low activation energy process （in alkaline solutions）. Theoretic calculation reveals that the sensing reaction of QMA undergoes a 1,4-addition process with neutral thiols （RSH）, and a 1,2-addition pathway for the sensing reaction of QME with RS-. Therefore, the sensing reaction of QMA is an acid-catalysed Michael addition via a 1,4-addition, and a normal base-catalysed Michael addition via a 1,2-addition.
基金This work was supported by the National Natural Science Foundation of China （No.51376185 and No.51106108）, the National Basic Research Program of China （No.2012CB215304）, the National High Technology Research and Development Program of China （No.2012AA101806）, and the Natural Science Foundation of Guangdong Province （No.$2013010011612）.
文摘A series of Ni based catalysts with different supports and basic additives were prepared by sequential impregnation method. The catalysts were characterized by XRD, BET, H2-TPR and CO2-TPD techniques. It was found that the introduction of basic additives enhanced the basicities of catalyats and promoted the dispersities of Ni particles by strong interaction between Ni2＋ and basic additives. Among the Ni based catalysts, 10%Ni/10%La203/ZrO2 showed the superior performance in sorbitol hydrogenolysis. The synergistic effect of Ni and La203 was proven to play an essential role in selective synthesis of EG and 1,2-PG. In the optimal reaction condition, the catalyst presented 100% sorbitol conversion and over 48% glycols （EG and 1,2-PG） yield. The kinetics study of polyols （sorbitol, xylitol and glycerol） hydrogenolysis showed that polyols with more hydroxyl number have higher activity and products distribution was final results of kinetic balance, which could give us some inspiration abeut how to change the products selectivity.
文摘In this study, the heteroatom classes and molecular structures of nitrogen compounds in vacuum residue arecharacterized by the electrospray ionization （ESI） Fourier transform ion cyclotron resonance mass spectrometry （FT-ICRMS） combined with the Fourier transform infrared （FT-IR） spectroscopy. The results demonstrate that three basic nitrogencompounds, N1 （in which a molecule contains one nitrogen atom, similarly hereinafter）, N1O1 and N2, are identified bytheir positive-ion mass spectra, and three non-basic nitrogen compounds, N1, N1O1, and N1S1, are characterized by theirnegative-ion mass spectra. Among these nitrogen compounds, the N1 class species are the most predominant. Combinedwith the data of ESI FT-ICR MS and FT-IR, the basic N1 class species are likely alkyl quinolines, naphthenic quinolines,acridines, benzonacridines, while the abundant non-basic N1 class species are derivatives of benzocarbazole. In comparisonwith CGO, the N1 basic nitrogen compounds in VR exhibit a higher average degree of condensation and have much longeralkyl side chains.
基金support of RU-Grant (1001/PKIMIA/811056) from Universiti Sains Malaysia (USM)
文摘The electrooxidation of ethylene glycol(EG) on the surface of gold nanoparticles(AuNPs) in alkaline medium was investigated.AuNPs were electrodeposited on pencil graphite(PG) by fast scan cyclic voltammetry.Different sizes of AuNPs deposited on the surface of PG(AuNPs/PG) were used for the electrooxidation process.AuNPs were electrodeposited on PG at various deposition times in the same potential range but with different scan rates and scan cycles.Scanning electron microscopy(SEM),transmission electron microscopy(TEM) and X-ray diffraction(XRD) were used to visualize and characterize the prepared AuNPs/PG electrodes.Cyclic voltammograms were also used to investigate the electrooxidation of EG.The effects of EG and supporting electrolyte concentrations,scan rate,particle size of AuNPs and final potential limit on the electrooxidation process have been investigated.Further studies showed that the electrooxidation of EG is affected by temperature of the medium.The prepared AuNPs showed stability after long-term use.
基金supported by the National Natural Science Foundation of China (21571038 and 21361005)the Open Fund of the Key Lab of Organic Optoelectronics & Molecular Engineering (Tsinghua University)+1 种基金the Foundation for Excellent Young Scientific and Technological Talents of Guizhou Province (2019-5666)the Special Fund for Natural Science of Guizhou University (201801)
文摘The synthesis of surface composition-tunable Pt-based octahedral nanoalloys is key to unravel the structureproperty relationship in fuel cells. Herein, we report a facile route to prepare composition-tunable Pt Cu octahedral nanoalloys by using halogen ions(Br-or/and I-) as composition modulators. Among these Pt Cu octahedral nanoalloys,Pt59 Cu41 octahedron exhibits the highest catalytic activity and durability in alkaline solution. The specific activity/mass activity of Pt59 Cu41 octahedron is 20.25 m A cm^-2/3.24 A mg^-1 Pt,which is 6.64/5.3 times higher than commercial Pt black in 0.5 mol L^-1 CH3 OH, respectively. In the case of using ethanol(0.5 mol L^-1) as fuel source, Pt59 Cu41 octahedron shows much better catalytic activity, that is 34.84 m A cm^-2/5.58 A mg^-1 Pt for specific activity/mass activity, which is 9.16/7.34 times higher than commercial Pt black, respectively. In situ Fourier transform infrared spectroscopy is employed to detect the intermediate species and products for methanol/ethanol oxidation reaction and a plausible mechanism is proposed to explain the improved activity and durability of Pt59 Cu41 octahedron toward methanol/ethanol oxidation in alkaline medium.
