Since the discovery of carbon nanotubes (CNT), this material has been recognized as an attractive catalyst support. CNT must be functionalized before use as a catalyst support and typically this involves oxidation. Ho...Since the discovery of carbon nanotubes (CNT), this material has been recognized as an attractive catalyst support. CNT must be functionalized before use as a catalyst support and typically this involves oxidation. However, the functional group distribution on the CNT is very complex mixture of groups and varies with oxidation agent used. Here a simple acid-base titration is introduced to characterize the oxygen functionalized CNT. By comparing characterization with near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS) for both at the C and O K-edges, it can be demonstrated that potentiometric proton titration can be a fast and quantitative analysis for Brnsted acid functional groups on CNT.展开更多
The molecular orientation of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) multilayers adsorbed on Au (111) surface has been investigated using angular dependent O K-edge near edge X-ray absorption fine s...The molecular orientation of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) multilayers adsorbed on Au (111) surface has been investigated using angular dependent O K-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The significant angular dependence of important resonant structures (π* and σ*) reveals that PTCDA molecules adopt an ordered geometry on the substrate surface. The average tilt angle of the PTCDA molecular planes is 27°±10° from the Au (111) surface.展开更多
In recent years, Near Edge X-ray Absorption Fine Structure (NEXAFS) has become an important method for the determination of surface structure. The intermediate in the catalytic decomposition of formic acid on copper s...In recent years, Near Edge X-ray Absorption Fine Structure (NEXAFS) has become an important method for the determination of surface structure. The intermediate in the catalytic decomposition of formic acid on copper surface, formate (HCOO), interests several research groups. The studies of electron-energy-loss spectroscopy and NEXAFS indicate that the formate is oriented with its molecular plane perpendicular to the metal surface,展开更多
The possible configurations of pyrrole absorbed on a Si(100)surface have been investigated by x-ray photoelectron spectroscopy(XPS)and near-edge x-ray absorption fine structure(NEXAFS)spectra.The C-1s XPS and NEXAFS s...The possible configurations of pyrrole absorbed on a Si(100)surface have been investigated by x-ray photoelectron spectroscopy(XPS)and near-edge x-ray absorption fine structure(NEXAFS)spectra.The C-1s XPS and NEXAFS spectra of these adsorption configurations have been calculated by using the density functional theory(DFT)method and fullcore hole(FCH)approximation to investigate the relationship between the adsorption configurations and the spectra.The result shows that the XPS and NEXAFS spectra are structurally dependent on the configurations of pyrrole absorbed on the Si(100)surface.Compared with the XPS,the NEXAFS spectra are relatively sensitive to the adsorption configurations and can accurately identify them.The NEXAFS decomposition spectra produced by non-equivalent carbon atoms have also been calculated and show that the spectral features vary with the diverse types of carbon atoms and their structural environments.展开更多
The synthesis and structure of hexagonal boron carbonitride (h-BCN) film on polycrystalline diamond surface were reported. Polycrystalline diamond and/or diamond-like carbon were first fabricated on Si (100) and then ...The synthesis and structure of hexagonal boron carbonitride (h-BCN) film on polycrystalline diamond surface were reported. Polycrystalline diamond and/or diamond-like carbon were first fabricated on Si (100) and then diamond like carbon was used as substrate. The deposition was performed by radio frequency plasma enhanced chemical vapor deposition. In order to reduce the content of nitrogen void defects, the deposition was performed at the high temperature of 950°C under the working pressure of 2.6 Pa. The typical sample with atomic composition of B31 C37 N26 O6 in the h-BCN lattice was characterized by X-ray photoelectron spectroscopy. The fine structure of the film was studied by near-edge X-ray absorption fine structure (NEXAFS) measurements. The B K-edge and N K-edge of NEXAFS spectra revealed that the synthesized h-BCN film had the ideal honeycomb- like BN3 configuration without nitrogen void defects.展开更多
Hexagonal nano-crystalline boron carbonitride (h-BCN) films grown on Si (100) substrate have been precisely investigated. The films were synthesized by radio frequency plasma enhanced chemical vapor deposition using t...Hexagonal nano-crystalline boron carbonitride (h-BCN) films grown on Si (100) substrate have been precisely investigated. The films were synthesized by radio frequency plasma enhanced chemical vapor deposition using tris-dimethylamino borane as a single-source molecular precursor. The deposition was performed by setting RF power at 400 - 800 W. The reaction pressure was at 2.6 Pa and the substrate temperature was recorded at 700°C - 800°C. Formation of the nano-crystalline h-BCN compound has been confirmed by X-ray diffraction analysis. The diffraction peaks at 26.3° together with a small unknown peak at 29.2° were elucidated due to the formation of an h-BCN structure. The films composed of B, C, and N atoms with different B-N, B-C, C-N chemical bonds in forming the sp2-BCN atomic configuration studied by X-ray photoelectron spectroscopy. Orientation and local structures of the h-BCN hybrid were studied by near-edge X-ray absorption fine structure (NEXAFS) measurements. The dominant presence of p* and s* resonance peaks of the sp2-hybrid orbitals in the B K-edge NEXAFS spectra revealed the formation of the sp2-BCN configuration around B atoms like-BN3 in h-BN. The orientation was suggested on the basis of the polarization dependence of B K-edge and N K-edge of the NEXAFS spectra.展开更多
In order to uncover the real origin of red luminescence from Sr_3Al_2O_6：Eu and the physical mechanisms that were involved in the dynamical process of luminescence, variant amount of Eu and Dy activated Sr_3Al_2O_6 p...In order to uncover the real origin of red luminescence from Sr_3Al_2O_6：Eu and the physical mechanisms that were involved in the dynamical process of luminescence, variant amount of Eu and Dy activated Sr_3Al_2O_6 phosphors were synthesized with the solid-state reaction and the combustion-assisted solid-state reaction, respectively, using the fine graphite powder or the mixed H^2＋N_2gases as a reducing agent. The phase was examined with XRD analysis and the photoluminescence properties were characterized by a fluorescence spectrometer. Although the phosphors possessed the same Sr_3Al_2O_6 phase, different emission colors（red or green） were obtained, relying on synthesis conditions. The simultaneous existence of Eu^2＋ and Eu^3＋ was not only observed in the emission and excitation spectra, but also identified with the near edge X-ray absorption fine structure spectroscopy（NEXAFS）.The mixed valence（higher than ＋2 and less than ＋3） of Eu may be related with the six different sites of Sr, whose effective valence ranged from ＋1.5058 to ＋2.2698, in the crystal lattice of Sr_3Al_2O_6 that could accommodate Eu. Moreover, the reduction of Eu^3＋ to forming Eu^2＋ depended on the amount of Eu^3＋ or Dy^3＋ doped, due to the different energy barrier in each site of Sr that Eu had to overcome. The residual Eu^3＋, similar to the doped Dy^3＋, played an important role in supplying the hole for Eu^2＋ to form a bound trap（Eu^2＋）＊ after excitation. During electron returning to the 4f^7 ground state of Eu^2＋, the red luminescence was radiated. Therefore, the synergetic effects of Eu^2＋ and Eu^3＋（Dy^3＋） produce red luminescence.展开更多
基金the DOE, Office of Basic Energy Sciences, grant DE-FG02-01ER15183 for financial support
文摘Since the discovery of carbon nanotubes (CNT), this material has been recognized as an attractive catalyst support. CNT must be functionalized before use as a catalyst support and typically this involves oxidation. However, the functional group distribution on the CNT is very complex mixture of groups and varies with oxidation agent used. Here a simple acid-base titration is introduced to characterize the oxygen functionalized CNT. By comparing characterization with near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS) for both at the C and O K-edges, it can be demonstrated that potentiometric proton titration can be a fast and quantitative analysis for Brnsted acid functional groups on CNT.
基金supported by the National Natural Science Foundation of China (10975138, 10505019 and 10775126)the Scientific Research Foundation of the Graduate School of the University of Science and Technology of China
文摘The molecular orientation of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) multilayers adsorbed on Au (111) surface has been investigated using angular dependent O K-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The significant angular dependence of important resonant structures (π* and σ*) reveals that PTCDA molecules adopt an ordered geometry on the substrate surface. The average tilt angle of the PTCDA molecular planes is 27°±10° from the Au (111) surface.
基金Project supported by the National Natural Science Foundation of China
文摘In recent years, Near Edge X-ray Absorption Fine Structure (NEXAFS) has become an important method for the determination of surface structure. The intermediate in the catalytic decomposition of formic acid on copper surface, formate (HCOO), interests several research groups. The studies of electron-energy-loss spectroscopy and NEXAFS indicate that the formate is oriented with its molecular plane perpendicular to the metal surface,
基金Project supported by the Shandong Provincial Natural Science Foundation,China(Grant Nos.ZR2022MA025 and ZR2020MA077).
文摘The possible configurations of pyrrole absorbed on a Si(100)surface have been investigated by x-ray photoelectron spectroscopy(XPS)and near-edge x-ray absorption fine structure(NEXAFS)spectra.The C-1s XPS and NEXAFS spectra of these adsorption configurations have been calculated by using the density functional theory(DFT)method and fullcore hole(FCH)approximation to investigate the relationship between the adsorption configurations and the spectra.The result shows that the XPS and NEXAFS spectra are structurally dependent on the configurations of pyrrole absorbed on the Si(100)surface.Compared with the XPS,the NEXAFS spectra are relatively sensitive to the adsorption configurations and can accurately identify them.The NEXAFS decomposition spectra produced by non-equivalent carbon atoms have also been calculated and show that the spectral features vary with the diverse types of carbon atoms and their structural environments.
文摘The synthesis and structure of hexagonal boron carbonitride (h-BCN) film on polycrystalline diamond surface were reported. Polycrystalline diamond and/or diamond-like carbon were first fabricated on Si (100) and then diamond like carbon was used as substrate. The deposition was performed by radio frequency plasma enhanced chemical vapor deposition. In order to reduce the content of nitrogen void defects, the deposition was performed at the high temperature of 950°C under the working pressure of 2.6 Pa. The typical sample with atomic composition of B31 C37 N26 O6 in the h-BCN lattice was characterized by X-ray photoelectron spectroscopy. The fine structure of the film was studied by near-edge X-ray absorption fine structure (NEXAFS) measurements. The B K-edge and N K-edge of NEXAFS spectra revealed that the synthesized h-BCN film had the ideal honeycomb- like BN3 configuration without nitrogen void defects.
文摘Hexagonal nano-crystalline boron carbonitride (h-BCN) films grown on Si (100) substrate have been precisely investigated. The films were synthesized by radio frequency plasma enhanced chemical vapor deposition using tris-dimethylamino borane as a single-source molecular precursor. The deposition was performed by setting RF power at 400 - 800 W. The reaction pressure was at 2.6 Pa and the substrate temperature was recorded at 700°C - 800°C. Formation of the nano-crystalline h-BCN compound has been confirmed by X-ray diffraction analysis. The diffraction peaks at 26.3° together with a small unknown peak at 29.2° were elucidated due to the formation of an h-BCN structure. The films composed of B, C, and N atoms with different B-N, B-C, C-N chemical bonds in forming the sp2-BCN atomic configuration studied by X-ray photoelectron spectroscopy. Orientation and local structures of the h-BCN hybrid were studied by near-edge X-ray absorption fine structure (NEXAFS) measurements. The dominant presence of p* and s* resonance peaks of the sp2-hybrid orbitals in the B K-edge NEXAFS spectra revealed the formation of the sp2-BCN configuration around B atoms like-BN3 in h-BN. The orientation was suggested on the basis of the polarization dependence of B K-edge and N K-edge of the NEXAFS spectra.
基金Project supported by the National High-Tech R&D Program(863 program)(2013AA03A114)the joint funding of National Natural Science Foundation of China and the Chinese Academy of Sciences(U1332133)+3 种基金the Science and Technology Program of Anhui Province of China(1301022062,1301022067)the Special Fund for Research and Development of the Hefei Institute(IMICZ2015112)the Fund of Beijing National Laboratory for Molecular Sciences(20140143)and the Key Discipline of Information and Communication Engineering of University of Science and Technology of Anhui(AKZDXK2015C02)
文摘In order to uncover the real origin of red luminescence from Sr_3Al_2O_6：Eu and the physical mechanisms that were involved in the dynamical process of luminescence, variant amount of Eu and Dy activated Sr_3Al_2O_6 phosphors were synthesized with the solid-state reaction and the combustion-assisted solid-state reaction, respectively, using the fine graphite powder or the mixed H^2＋N_2gases as a reducing agent. The phase was examined with XRD analysis and the photoluminescence properties were characterized by a fluorescence spectrometer. Although the phosphors possessed the same Sr_3Al_2O_6 phase, different emission colors（red or green） were obtained, relying on synthesis conditions. The simultaneous existence of Eu^2＋ and Eu^3＋ was not only observed in the emission and excitation spectra, but also identified with the near edge X-ray absorption fine structure spectroscopy（NEXAFS）.The mixed valence（higher than ＋2 and less than ＋3） of Eu may be related with the six different sites of Sr, whose effective valence ranged from ＋1.5058 to ＋2.2698, in the crystal lattice of Sr_3Al_2O_6 that could accommodate Eu. Moreover, the reduction of Eu^3＋ to forming Eu^2＋ depended on the amount of Eu^3＋ or Dy^3＋ doped, due to the different energy barrier in each site of Sr that Eu had to overcome. The residual Eu^3＋, similar to the doped Dy^3＋, played an important role in supplying the hole for Eu^2＋ to form a bound trap（Eu^2＋）＊ after excitation. During electron returning to the 4f^7 ground state of Eu^2＋, the red luminescence was radiated. Therefore, the synergetic effects of Eu^2＋ and Eu^3＋（Dy^3＋） produce red luminescence.
