Chemical doping is an effective method to intrinsically modify the chemical and electronic property of graphene. We propose a novel approach to synthesize the nitrogen-doped graphene via thermal annealing graphene wit...Chemical doping is an effective method to intrinsically modify the chemical and electronic property of graphene. We propose a novel approach to synthesize the nitrogen-doped graphene via thermal annealing graphene with urea, in which the nitrogen source can be controllably released from the urea by varying the annealed temperature and time. The doped N content and the configuration N as well as the thermal stabilities are also evaluated with X-ray photoelectron spectroscopy and Raman spectra. Electrical measurements indi- cate that the conductivity of doped graphene can be well regulated with the N content. The method is expected to produce large scale and controllable N-doped graphene sheets for a variety of potential applications.展开更多
Effect of doping cerium in the support on the catalytic activity and side product of the reaction in the oxidative carbonylation of phenol to diphenyl carbonate (DPC) over the catalyst Pd-Co/Cu-Co-Mn mixed oxides was ...Effect of doping cerium in the support on the catalytic activity and side product of the reaction in the oxidative carbonylation of phenol to diphenyl carbonate (DPC) over the catalyst Pd-Co/Cu-Co-Mn mixed oxides was studied. The specific surface areas, crystal phase, valency, and content of the element on the surface of the catalysts were determined, and the products were detected by gas chromatograph/mass spectrometry (GC-MS). It is found that the catalyst without Ce shows higher activity than that with Ce, and the yields of DPC for the two cata-lysts can reach 30% and 23%, respectively. However, doping cerium can prevent the formation of 2-hydroxyphenyl benzoate and p-bromophenyl phenyl carbonate.展开更多
A novel face recognition method based on fusion of spatial and frequency features was presented to improve recognition accuracy. Dual-Tree Complex Wavelet Transform derives desirable facial features to cope with the v...A novel face recognition method based on fusion of spatial and frequency features was presented to improve recognition accuracy. Dual-Tree Complex Wavelet Transform derives desirable facial features to cope with the variation due to the illumination and facial expression changes. By adopting spectral regression and complex fusion technologies respectively, two improved neighborhood preserving discriminant analysis feature extraction methods were proposed to capture the face manifold structures and locality discriminatory information. Extensive experiments have been made to compare the recognition performance of the proposed method with some popular dimensionality reduction methods on ORL and Yale face databases. The results verify the effectiveness of the proposed method.展开更多
UV-Vis absorption spectra of the molecular complex formed by imidazole （Ira） and chloranil （CA） were measured in chloroform. The stoichiometry of the imidazole-chloranil （hn-CA） complex was determined as 1：1 by...UV-Vis absorption spectra of the molecular complex formed by imidazole （Ira） and chloranil （CA） were measured in chloroform. The stoichiometry of the imidazole-chloranil （hn-CA） complex was determined as 1：1 by applying Benesi-Hildebrand＇s equation and Job＇s continuous variation method. Density function theory （DFT） and MP2 calculations were performed to study the structures and the binding energies of the Im-CA complex. The calculations located four conformations （denoted as S1-S4） for the Ira-CA complex, two edge（Im）-to-face（CA） linked and two edge（Im）-to-edge（CA） linked. It was found that the edge-to-face conformers are more stable than the edge-to-edge ones. The bonding characteristics of these conformers were investigated with natural population analysis （NPA）, topological analysis of electron density, and natural bond orbital （NBO） analysis. It was revealed that the edge-to-face conformers are charge-transfer （CT） complexes whereas the edge-to-edge conformers are the hydrogen bond complexes. For the most stable conformation of the Ira-CA complex （S1）, the charge transfer interaction of the imidazole n（N15） lone pair orbital with the chloranil π＊ （C1=O7） orbital plays a crucial role in the Ira-CA binding, and the binding is further strengthened by the O7… H2O hydrogen bond. The electronic excitation energies of the complex （S1） were calculated with time-dependent DFT （TDDFT）, and the observed UV-Visible spectrum of the complex was analyzed based on the computed results.展开更多
A series of Ce, H3PW12O40 co-doped TiO2 hollow fibers photocatalysts have been prepared by sol-gel method using ammonium ceric nitrate, H3PW12O40 and tetrabutyltitanate as precursors and cotton fibers as template, fol...A series of Ce, H3PW12O40 co-doped TiO2 hollow fibers photocatalysts have been prepared by sol-gel method using ammonium ceric nitrate, H3PW12O40 and tetrabutyltitanate as precursors and cotton fibers as template, followed by calcination at 500 ℃ in N2 atmosphere for 2 h. Scanning electron microscopy, X-ray diffraction, nitrogen adsorption-desorption mea- surements, and UV-Vis spectroscopy are employed to characterize the morphology, crystal structure, surface structure, and optical absorption properties of the samples. The photo- catalytic performance of the samples has been studied by photodegradation phenol in water under UV and visible light irradiation. The results show that the TiO2 fiber materials have hollow structures, and the co-doped TiO2 hollow fibers exhibit higher photocatalytic activities for the degradation of phenol than un-doped, single-doped TiO2 hollow fibers under UV and visible light. In addition, the recyclability of co-doped TiO2 fibers is also confirmed that the TiO2 fiber retains ca. 90% of its activity after being used four times. It is shown that the co-doped TiO2 fibers can be activated by visible light and may be potentially applied to the treatment of water contaminated by organic pollutants. The synergistic effect of Ce and H3PW12O40 co-doping plays an important role in improving the photocatalytic activity.展开更多
Aluminum doped hydroxyapatite （HA：AI3 ＋） nanopowders were successfully prepared via a simple and efficient one-pot mechanochemical route. The effects of dopant loading on phase compositions and structural features...Aluminum doped hydroxyapatite （HA：AI3 ＋） nanopowders were successfully prepared via a simple and efficient one-pot mechanochemical route. The effects of dopant loading on phase compositions and structural features were assessed by Rietveld analysis. The XRD-Rietveld refinement revealed the stabilization of HA in hexagonal structure for all the samples. The sharpness and intensity of the apatite-derived XRD peaks decreased as the dopant content increased to 10% due to the increase in lattice imperfections and mechanically induced amorphization. The incorpo- ration of A13 ＋ into the HA lattice decreased the unit cell parameters. From the FfiR measurements, the representing bands of apatite were identified in all cases. The mechanosynthesized nanopowders consisted of nanospheroids with an average size of 44 - 20 nm and therefore are promising for bone tissue regeneration.展开更多
Zea mays L. is one of the biggest cropping systems among the sustainable development agronomy. Pollen from this crop source is unexplored and apiculture can be a good partner adding value to the product and creating n...Zea mays L. is one of the biggest cropping systems among the sustainable development agronomy. Pollen from this crop source is unexplored and apiculture can be a good partner adding value to the product and creating new jobs helping to solve some social issues as unemployment. However, food safety is crucial, thus the aim of this study was to explore the flavonoid/phenolic profiles from Z. mays L. pollen as a fingerprint for this plant identification and also to demonstrate how the method of bee pollen samples （honeybee collected pollen） is applied. For this purpose, several sources ofZ. mays L. pollen were analyzed, including corn hybrids and genetic modified samples collected at the breeding fields. For this work, samples were taken at several years from 2000 to 2012 and collected from different countries and locations, such as Portugal, Mexico and Brazil. Results showed, for the first time, that the fingerprint （flavonoid/phenolic profile） for Z. mays L. pollen does not change over the time of sampling neither with the region of harvesting. The high performance liquid chromatography-diode array detector （HPLC/DAD） fingerprints of phenolic/flavonoid extract from Z. mays remain unchanged for all samples analyzed from different countries, hybrids and/or genetic modified plants. This is also the first study reporting these phenolic compounds not only in pollen collected directly from hybrid plants, but also in Z. mays bee pollen. The described fingerprinting method is easy, fast and accurate for the characterization of Z. mays L. pollen samples and complete microscopic analysis because it is species-specific.展开更多
Heteroatom-doped Pt-based nanocrystals have generated considerable interest and hold great prospects in heterocatalysis. However, engineering the superficial atomic configurations of these nanocrystals via in situ sur...Heteroatom-doped Pt-based nanocrystals have generated considerable interest and hold great prospects in heterocatalysis. However, engineering the superficial atomic configurations of these nanocrystals via in situ surface doping remains exceedingly challenging. Herein, we propose a onepot, in situ surface doping chemical synthesis protocol to prepare quatermetallic Pt Ni Co Rh dendritic nanocrystals as versatile and active catalysts for the electrooxidation of C_(1) fuels. Leveraging the selective coordination effect between ascorbic acid and Rh^(3+)ions, the doping of trace Rh atoms can be guided specifically at the near-surface of Pt Ni Co Rh nanocatalysts. Electrocatalytic tests indicate that Pt_(67)Ni_(16)Co_(16)Rh_(1) nanocrystals with in situ trace Rh-doped surface exhibit substantially enhanced activity, durability, and CO tolerance for the electrooxidation of methanol, formaldehyde, and formic acid. In situ Fourier transform infrared spectroscopy provides molecular-level insight into the exceptional performance of these nanocatalysts. The surface incorporation of anticorrosive Rh atoms enables the transfer of CO intermediates from the atop Pt sites to the bridged Rh–Pt surface sites,thereby facilitating the elimination of these poisoning species from the catalyst surface. This study presents an effective in situ surface doping strategy which can enable the design of more atom-economic heterocatalysts.展开更多
In proteomics, attention has focused on various immobilized enzyme reactors (IMERs) for the realization of high throughput digestion. In this report, a novel organic-inorganic hybrid monolith based IMER was prepared i...In proteomics, attention has focused on various immobilized enzyme reactors (IMERs) for the realization of high throughput digestion. In this report, a novel organic-inorganic hybrid monolith based IMER was prepared in a 100 μm i.d. capillary with 3-glycidoxypropyltrimethoxysilane (GLYMO) as the monomer and tetraethoxysilane (TEOS) as the crosslinker. Trypsin immobilization was achieved via the reaction between vicinal diol groups, which were obtained from hydrolysis of epoxy groups, and the amino groups of trypsin. Bovine serum albumin was digested thoroughly by this IMER in 47 s. After micro-reverse phase liquid chromatography-tandem mass spectrometry (μRPLC-MS/MS) analysis and database searching, beyond 35% sequence coverage was obtained, and the result was comparable to that of 12 h in solution digestion. The present IMER has potential for high throughput digestion.展开更多
Delayed coking is an important petroleum resid conversion process.The processability of coking liquids is known to be dependent on the heteroatom compounds present in the coking liquids.Eight commercial delayed coking...Delayed coking is an important petroleum resid conversion process.The processability of coking liquids is known to be dependent on the heteroatom compounds present in the coking liquids.Eight commercial delayed coking liquids were characterized by electrospray ionization(ESI)Fourier transform ion cyclotron resonance mass spectrometry(ESI FT-ICR MS)and gas chromatographic techniques.High relatively abundant heteroatom compounds in the coking liquids were 1-4 aromatic-ring pyridinic nitrogen compounds,carbazoles,benzocarbazoles,phenols,mercaptans,benzothiophenes,dibenzothiophenes,and naphthobenzothiophenes.Coking liquids derived from various feeds had similar compound class types,molecular weight distribution ranges,and double bond equivalents(DBE).However,the concentration of individual compounds and the distribution of DBE versus carbon number of heteroatom compounds varied.A comparison of heteroatom compounds in coker feeds and products revealed the various reaction mechanism of heteroatom compounds occurred during the coking process.The results suggested that molecular-level process models can be developed for optimization of unit operation to obtain desirable products that meet the environmental specifications and quality requirements.展开更多
High performance liquid chromatography coupled with quadruple-time-of-flight mass spectrometry(HPLC-Q-TOF-MS)method was developed for analyzing the hydrolytic mixtures of ginsenoside R_(g1) in acidic conditions(pH 3)....High performance liquid chromatography coupled with quadruple-time-of-flight mass spectrometry(HPLC-Q-TOF-MS)method was developed for analyzing the hydrolytic mixtures of ginsenoside R_(g1) in acidic conditions(pH 3). Three catalysts, a heteropolyacid(H_4SiW_(12)O_(40), SiW_(12) for short), its complex with γ-CD(SiW_(12)/γ-CD for short) and formic acid, were used for comparison. The chemical transformation products were identified based on the accurate mass measurement and the fragment ions obtained from tandem mass spectrometry. It was concluded that the catalytic efficiency of SiW_(12)(≈SiW_(12)/γ-CD) is ca. 410 times higher than that of formic acid, thus becoming the most efficient catalyst for chemical transformations of ginsenosides.展开更多
文摘Chemical doping is an effective method to intrinsically modify the chemical and electronic property of graphene. We propose a novel approach to synthesize the nitrogen-doped graphene via thermal annealing graphene with urea, in which the nitrogen source can be controllably released from the urea by varying the annealed temperature and time. The doped N content and the configuration N as well as the thermal stabilities are also evaluated with X-ray photoelectron spectroscopy and Raman spectra. Electrical measurements indi- cate that the conductivity of doped graphene can be well regulated with the N content. The method is expected to produce large scale and controllable N-doped graphene sheets for a variety of potential applications.
文摘Effect of doping cerium in the support on the catalytic activity and side product of the reaction in the oxidative carbonylation of phenol to diphenyl carbonate (DPC) over the catalyst Pd-Co/Cu-Co-Mn mixed oxides was studied. The specific surface areas, crystal phase, valency, and content of the element on the surface of the catalysts were determined, and the products were detected by gas chromatograph/mass spectrometry (GC-MS). It is found that the catalyst without Ce shows higher activity than that with Ce, and the yields of DPC for the two cata-lysts can reach 30% and 23%, respectively. However, doping cerium can prevent the formation of 2-hydroxyphenyl benzoate and p-bromophenyl phenyl carbonate.
基金National Natural Science Foundation of China(No.61004088)Key Basic Research Foundation of Shanghai Municipal Science and Technology Commission,China(No.09JC1408000)
文摘A novel face recognition method based on fusion of spatial and frequency features was presented to improve recognition accuracy. Dual-Tree Complex Wavelet Transform derives desirable facial features to cope with the variation due to the illumination and facial expression changes. By adopting spectral regression and complex fusion technologies respectively, two improved neighborhood preserving discriminant analysis feature extraction methods were proposed to capture the face manifold structures and locality discriminatory information. Extensive experiments have been made to compare the recognition performance of the proposed method with some popular dimensionality reduction methods on ORL and Yale face databases. The results verify the effectiveness of the proposed method.
基金ACKNOWLEDGMENT This work was supported Science Foundation of China by the National Natural （No.20473078）.
文摘UV-Vis absorption spectra of the molecular complex formed by imidazole （Ira） and chloranil （CA） were measured in chloroform. The stoichiometry of the imidazole-chloranil （hn-CA） complex was determined as 1：1 by applying Benesi-Hildebrand＇s equation and Job＇s continuous variation method. Density function theory （DFT） and MP2 calculations were performed to study the structures and the binding energies of the Im-CA complex. The calculations located four conformations （denoted as S1-S4） for the Ira-CA complex, two edge（Im）-to-face（CA） linked and two edge（Im）-to-edge（CA） linked. It was found that the edge-to-face conformers are more stable than the edge-to-edge ones. The bonding characteristics of these conformers were investigated with natural population analysis （NPA）, topological analysis of electron density, and natural bond orbital （NBO） analysis. It was revealed that the edge-to-face conformers are charge-transfer （CT） complexes whereas the edge-to-edge conformers are the hydrogen bond complexes. For the most stable conformation of the Ira-CA complex （S1）, the charge transfer interaction of the imidazole n（N15） lone pair orbital with the chloranil π＊ （C1=O7） orbital plays a crucial role in the Ira-CA binding, and the binding is further strengthened by the O7… H2O hydrogen bond. The electronic excitation energies of the complex （S1） were calculated with time-dependent DFT （TDDFT）, and the observed UV-Visible spectrum of the complex was analyzed based on the computed results.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.41373127） and Liaon- ing Provincial Natural Science Foundation of China （No.2013020121）.
文摘A series of Ce, H3PW12O40 co-doped TiO2 hollow fibers photocatalysts have been prepared by sol-gel method using ammonium ceric nitrate, H3PW12O40 and tetrabutyltitanate as precursors and cotton fibers as template, followed by calcination at 500 ℃ in N2 atmosphere for 2 h. Scanning electron microscopy, X-ray diffraction, nitrogen adsorption-desorption mea- surements, and UV-Vis spectroscopy are employed to characterize the morphology, crystal structure, surface structure, and optical absorption properties of the samples. The photo- catalytic performance of the samples has been studied by photodegradation phenol in water under UV and visible light irradiation. The results show that the TiO2 fiber materials have hollow structures, and the co-doped TiO2 hollow fibers exhibit higher photocatalytic activities for the degradation of phenol than un-doped, single-doped TiO2 hollow fibers under UV and visible light. In addition, the recyclability of co-doped TiO2 fibers is also confirmed that the TiO2 fiber retains ca. 90% of its activity after being used four times. It is shown that the co-doped TiO2 fibers can be activated by visible light and may be potentially applied to the treatment of water contaminated by organic pollutants. The synergistic effect of Ce and H3PW12O40 co-doping plays an important role in improving the photocatalytic activity.
基金Supported by the National Science Foundation(PREM center for interfaces,DMR-1205670)the Robert A.Welch Foundation(Al-0045)
文摘Aluminum doped hydroxyapatite （HA：AI3 ＋） nanopowders were successfully prepared via a simple and efficient one-pot mechanochemical route. The effects of dopant loading on phase compositions and structural features were assessed by Rietveld analysis. The XRD-Rietveld refinement revealed the stabilization of HA in hexagonal structure for all the samples. The sharpness and intensity of the apatite-derived XRD peaks decreased as the dopant content increased to 10% due to the increase in lattice imperfections and mechanically induced amorphization. The incorpo- ration of A13 ＋ into the HA lattice decreased the unit cell parameters. From the FfiR measurements, the representing bands of apatite were identified in all cases. The mechanosynthesized nanopowders consisted of nanospheroids with an average size of 44 - 20 nm and therefore are promising for bone tissue regeneration.
文摘Zea mays L. is one of the biggest cropping systems among the sustainable development agronomy. Pollen from this crop source is unexplored and apiculture can be a good partner adding value to the product and creating new jobs helping to solve some social issues as unemployment. However, food safety is crucial, thus the aim of this study was to explore the flavonoid/phenolic profiles from Z. mays L. pollen as a fingerprint for this plant identification and also to demonstrate how the method of bee pollen samples （honeybee collected pollen） is applied. For this purpose, several sources ofZ. mays L. pollen were analyzed, including corn hybrids and genetic modified samples collected at the breeding fields. For this work, samples were taken at several years from 2000 to 2012 and collected from different countries and locations, such as Portugal, Mexico and Brazil. Results showed, for the first time, that the fingerprint （flavonoid/phenolic profile） for Z. mays L. pollen does not change over the time of sampling neither with the region of harvesting. The high performance liquid chromatography-diode array detector （HPLC/DAD） fingerprints of phenolic/flavonoid extract from Z. mays remain unchanged for all samples analyzed from different countries, hybrids and/or genetic modified plants. This is also the first study reporting these phenolic compounds not only in pollen collected directly from hybrid plants, but also in Z. mays bee pollen. The described fingerprinting method is easy, fast and accurate for the characterization of Z. mays L. pollen samples and complete microscopic analysis because it is species-specific.
基金supported by the National Natural Science Foundation of China (21771067)the Natural Science Foundation of Fujian Province (2017J06005 and 2019J01058)+3 种基金the Program for New Century Excellent Talents in Fujian Province Universitythe Promotion Program for Young and Middle-aged Teacher in Science and Technology Research of Huaqiao University (ZQN-PY507)the Scientific Research Funds of Huaqiao Universitythe Instrumental Analysis Center of Huaqiao University for the analysis support。
文摘Heteroatom-doped Pt-based nanocrystals have generated considerable interest and hold great prospects in heterocatalysis. However, engineering the superficial atomic configurations of these nanocrystals via in situ surface doping remains exceedingly challenging. Herein, we propose a onepot, in situ surface doping chemical synthesis protocol to prepare quatermetallic Pt Ni Co Rh dendritic nanocrystals as versatile and active catalysts for the electrooxidation of C_(1) fuels. Leveraging the selective coordination effect between ascorbic acid and Rh^(3+)ions, the doping of trace Rh atoms can be guided specifically at the near-surface of Pt Ni Co Rh nanocatalysts. Electrocatalytic tests indicate that Pt_(67)Ni_(16)Co_(16)Rh_(1) nanocrystals with in situ trace Rh-doped surface exhibit substantially enhanced activity, durability, and CO tolerance for the electrooxidation of methanol, formaldehyde, and formic acid. In situ Fourier transform infrared spectroscopy provides molecular-level insight into the exceptional performance of these nanocatalysts. The surface incorporation of anticorrosive Rh atoms enables the transfer of CO intermediates from the atop Pt sites to the bridged Rh–Pt surface sites,thereby facilitating the elimination of these poisoning species from the catalyst surface. This study presents an effective in situ surface doping strategy which can enable the design of more atom-economic heterocatalysts.
基金supported by the National Natural Science Foundation of China (Grant Nos. 20935004 and 20775080)National Basic Research Program of China (Grant No. 2007CB914100)Knowledge Innovation Program of Chinese Academy of Sciences (Grant No. KJCX2YW.H09)
文摘In proteomics, attention has focused on various immobilized enzyme reactors (IMERs) for the realization of high throughput digestion. In this report, a novel organic-inorganic hybrid monolith based IMER was prepared in a 100 μm i.d. capillary with 3-glycidoxypropyltrimethoxysilane (GLYMO) as the monomer and tetraethoxysilane (TEOS) as the crosslinker. Trypsin immobilization was achieved via the reaction between vicinal diol groups, which were obtained from hydrolysis of epoxy groups, and the amino groups of trypsin. Bovine serum albumin was digested thoroughly by this IMER in 47 s. After micro-reverse phase liquid chromatography-tandem mass spectrometry (μRPLC-MS/MS) analysis and database searching, beyond 35% sequence coverage was obtained, and the result was comparable to that of 12 h in solution digestion. The present IMER has potential for high throughput digestion.
基金supported by the National Natural Science Foundation of China(U1162204,21236009,21376262)
文摘Delayed coking is an important petroleum resid conversion process.The processability of coking liquids is known to be dependent on the heteroatom compounds present in the coking liquids.Eight commercial delayed coking liquids were characterized by electrospray ionization(ESI)Fourier transform ion cyclotron resonance mass spectrometry(ESI FT-ICR MS)and gas chromatographic techniques.High relatively abundant heteroatom compounds in the coking liquids were 1-4 aromatic-ring pyridinic nitrogen compounds,carbazoles,benzocarbazoles,phenols,mercaptans,benzothiophenes,dibenzothiophenes,and naphthobenzothiophenes.Coking liquids derived from various feeds had similar compound class types,molecular weight distribution ranges,and double bond equivalents(DBE).However,the concentration of individual compounds and the distribution of DBE versus carbon number of heteroatom compounds varied.A comparison of heteroatom compounds in coker feeds and products revealed the various reaction mechanism of heteroatom compounds occurred during the coking process.The results suggested that molecular-level process models can be developed for optimization of unit operation to obtain desirable products that meet the environmental specifications and quality requirements.
基金supported by the National Natural Science Foundation of China(21371025),the 111 Project(B07012)the degree and postgraduate education development research project(YJYJG2015B07)by Beijing Institute of Technology
文摘High performance liquid chromatography coupled with quadruple-time-of-flight mass spectrometry(HPLC-Q-TOF-MS)method was developed for analyzing the hydrolytic mixtures of ginsenoside R_(g1) in acidic conditions(pH 3). Three catalysts, a heteropolyacid(H_4SiW_(12)O_(40), SiW_(12) for short), its complex with γ-CD(SiW_(12)/γ-CD for short) and formic acid, were used for comparison. The chemical transformation products were identified based on the accurate mass measurement and the fragment ions obtained from tandem mass spectrometry. It was concluded that the catalytic efficiency of SiW_(12)(≈SiW_(12)/γ-CD) is ca. 410 times higher than that of formic acid, thus becoming the most efficient catalyst for chemical transformations of ginsenosides.
