第8届国际共振电离谱学及其应用会议(Eighth International Symposium on ResonanceIonization Spectroscopy and Its Applications)于1996年6月30日至7月5日在美国宾夕法尼亚州立大学召开。本届会议由田纳西大学共振电离谱学研究所和...第8届国际共振电离谱学及其应用会议(Eighth International Symposium on ResonanceIonization Spectroscopy and Its Applications)于1996年6月30日至7月5日在美国宾夕法尼亚州立大学召开。本届会议由田纳西大学共振电离谱学研究所和宾州州立大学联合主办。约100位科研工作者来自近30个国家,在会上发表论文109篇。其中我国清华大学2人,大连化物所、吉林大学各1名,在会上发表特邀报告1篇,口头报告2篇,展贴报告5篇。笔者的特邀报告"原子双里德堡态的自电离过程",引起了与会代表的关注。共振电离谱学是70年代发展起来的新兴研究领域,其主要特点是利用激光的高分辨率、高选择性,配合其他手段,实现高灵敏测量,以期在科学技术的各个领域中获得应用。展开更多
Pyrolysis of benzene at 30 Torr was studied from 1360 K to 1820 K in this work. Synchrotron vacuum ultraviolet photoionization mass spectrometry was employed to detect the pyroly- sis products such as radicals, isomer...Pyrolysis of benzene at 30 Torr was studied from 1360 K to 1820 K in this work. Synchrotron vacuum ultraviolet photoionization mass spectrometry was employed to detect the pyroly- sis products such as radicals, isomers and polycyclic aromatic hydrocarbons, and measure their mole fraction profiles versus temperature. A low-pressure pyrolysis model of benzene was developed and validated by the experimental results. Rate of production analysis was performed to reveal the major reaction networks in both fuel decomposition and aromatic growth processes. It is concluded that benzene is mainly decomposed via H-abstraction reaction to produce phenyl and partly decomposed via unimolecular decomposition reac- tions to produce propargyl or phenyl. The decomposition process stops at the formation of acetylene and polyyne species like diacetylene and 1,3,5-hexatriyne due to their high thermal stabilities. Besides, the aromatic growth process in the low-pressure pyrolysis of benzene is concluded to initiate from benzene and phenyl, and is controlled by the even carbon growth mechanism due to the inhibited formation of C5 and C7 species which play important roles in the odd carbon growth mechanism.展开更多
LiNi1/3Co1/3Mn1/3O2 was coated with uniform nano-sized AlF3 layer by chemical precipitation method to improve its rate capability.The samples were characterized by X-ray diffractometry (XRD),transmission electron micr...LiNi1/3Co1/3Mn1/3O2 was coated with uniform nano-sized AlF3 layer by chemical precipitation method to improve its rate capability.The samples were characterized by X-ray diffractometry (XRD),transmission electron microscopy (TEM),energy dispersive spectroscopy (EDS),charge-discharge cycling,cyclic voltammetry (CV),and electrochemical impedance spectroscopy (EIS).Uniform coated layer with a thickness of about 3 nm was observed on the surface of LiNi1/3Co1/3Mn1/3O2 particle by TEM.At 0.5C and 2C rates,1.5% (mass fraction) AlF3-coated LiNi1/3Co1/3Mn1/3O2/Li in 2.8-4.3 V versus Li/Li+ after 80 cycles showed less than 3% of capacity fading,while those of the bare one were 16.5% and 45.9%,respectively.At 5C rate,the capacity retention of the coated sample after 50 cycles maintained 91.4% of the initial discharge capacity,while that of the bare one decreased to 52.6%.EIS result showed that a little change of charge transfer resistance of the coated sample resulting from uniform thin AlF3 layer was proposed as the main reason why its rate capability was improved obviously.CV result further indicated a greater reversibility for the electrode processes and better electrochemical performance of AlF3-coated layer.展开更多
The current distributions over carbon steel under iron red alkyd primer exposed to 3.5% sodium chloride solution were mapped using the wire beam electrode (WBE). The electrochemical impedance spectroscopy (EIS) of...The current distributions over carbon steel under iron red alkyd primer exposed to 3.5% sodium chloride solution were mapped using the wire beam electrode (WBE). The electrochemical impedance spectroscopy (EIS) of the WBE was carded out to analyze the performance of coating delamination and corrosion behavior of carbon steel beneath defective coating. The EIS data revealed that protective capability of coating decreased with immersion time and the degree of cathodic delamination showed a rapid rise. The current density distribution of WBE indicated that cathodic sites was located at the defect at the beginning of immersion and gradually spread into the intact coating. The cathodic regions were distinguished from the anodic area and distributed over the WBE. The changes of cathodic sites could reflect the deterioration process of defective coating. The cathodic area ratio was a more useful parameter than the cathodic delamination degree to evaluate the coating cathodic delamination. The polarity reversals of electrodes at the defect and beneath coating were observed. A simple discussion of relationship between the blister and the polarity reversal was made from a standpoint of electrochemical distribution. WBE method was able to map and record the changes of local cathodic sites beneath defective coating in real time, which could provide more detailed information about the local degradation of coating.展开更多
The Spurge family (Euphorbiaceae) is a large family of flowering plants. Two plant species of this family were collected from the Egyptian desert, extracted with methanol subjected to silica gel column chromatograph...The Spurge family (Euphorbiaceae) is a large family of flowering plants. Two plant species of this family were collected from the Egyptian desert, extracted with methanol subjected to silica gel column chromatography to give six compounds, three compounds from each plant. The compounds isolated from the methanol extract of Euphorbia retusa Forssk were identified as kaempferol-3-beta-D glucopyranosyl (1), 3-O-alpha-L-xylopyranosyl (1→3)-alpha-L xylopyranosyl (1→2), beta-D glucopyranosyllup 1,12-diene-3,21-diol (2) and 5,7,8,3',4'-pentahydroxy-3-methoxyflavone (3) and the compounds isolated from Euphorbia paralais L. identified as 3,5,3'-trihydroxy-6,7-d-methoxy-4' (7"-hydroxygeranyl-1"-ether) flavones (4), 3-O-syringic acid (1→4)-alpha-L- xylopyranosyl (1→3), beta-D-rahminopyranosyl hederagenin (5) and 3-O-syringic acid (1→4), beta-D-rahminopyranosyl (1→3),beta-D-rahminopyranosyl hederagenin (6). The structure of the isolated compounds was elucidated by chemical and spectrometric analysis such as Infera red (IR), proton and carbon nuclear magnetic resonance (1H-, 13C-NMR) and chemical ionization mass spectrometry (CI-MS).展开更多
The Li Ni1/3Co1/3Mn1/3O2 is first obtained by the controlled crystallization method and then coated with Ni3(PO4)2particles. The effects of the coating on rate capability and cycle life at high cut-off voltage are inv...The Li Ni1/3Co1/3Mn1/3O2 is first obtained by the controlled crystallization method and then coated with Ni3(PO4)2particles. The effects of the coating on rate capability and cycle life at high cut-off voltage are investigated by electrochemical impedance spectroscopy and galvanostatic measurements. The element ratio of Ni:Mn:Co is tested by inductively-coupled plasma spectrometer(ICP) analysis and it testified to be 1:1:1. It is indicated that Ni3(PO4)2-coated Li Ni1/3Co1/3Mn1/3O2 has an outstanding capacity retention, where 99% capacity retention is maintained after 10 cycles at 5C discharge rate between 2.7 V and 4.6 V. The electrochemical impedance spectroscopy(EIS) results show that the current exchange density i0 of the coated sample is higher than that of Li Ni1/3Co1/3Mn1/3O2, which is beneficial to its electrochemical performances. All the conclusions show that the Ni3(PO4)2coating can prominently enhance the high rate performance of the Li Ni1/3Co1/3Mn1/3O2, especially at high cut-off voltage.展开更多
In this work,electron energy spectroscopic mapping of surface plasmon of Ag nanostructures on highly oriented pyrolytic graphite is reported.Benefitting from the angular dispersive feature of the present scanning prob...In this work,electron energy spectroscopic mapping of surface plasmon of Ag nanostructures on highly oriented pyrolytic graphite is reported.Benefitting from the angular dispersive feature of the present scanning probe electron energy spectrometer,a multi-channel detection mode is developed.By scanning along one direction,the two-dimensional intensity distribution of Ag surface plasmon excitation due to the collision of electron emitted from the tip can be obtained in parallel.The spectroscopic spatial resolution is determined to be around 80 nm.展开更多
Trichloromethanesulfenyl thiocyanate, CCl3SSCN, was generated and studied by photoelectron spectroscopy (PES), photoionization mass spectroscopy (PIMS), and theoretical calculations. This molecule exhibits a gauch...Trichloromethanesulfenyl thiocyanate, CCl3SSCN, was generated and studied by photoelectron spectroscopy (PES), photoionization mass spectroscopy (PIMS), and theoretical calculations. This molecule exhibits a gauche conformation, and the torsional angle around S-S bond is 91.4° due to the sulfur-sulfur lone pair interactions. After ionization, the ground-state cationic-radical form of CCl3SSCN+ adopts a trans planar main-atom structure with Cs symmetry. The highest occupied molecular orbital (HOMO) of CC13SSCN corresponds to the electrons mainly localized on the sulfur 3p lone pair MO. The first ionization energy is determined to be 10.40 cV.展开更多
We measured the photoelectron spectra of Al_(n)C_(4)^(−)(n=2−4)clusters by using size-selected anion photoelectron spectroscopy.The structures of Al_(n)C_(4)^(−/0)(n=2−4)clusters were explored with quantum chemistry c...We measured the photoelectron spectra of Al_(n)C_(4)^(−)(n=2−4)clusters by using size-selected anion photoelectron spectroscopy.The structures of Al_(n)C_(4)^(−/0)(n=2−4)clusters were explored with quantum chemistry calculations and were determined by comparing the theoretical results with the experimental spectra.It is found that the most stable structure of Al_(2)C_(4)^(−) anion is a C_(2v)symmetry planar structure with two Al atoms interacting with two C_(2)units.In addition,Al_(2)C_(4)^(−) anion also has a D∞h symmetry linear structure with two Al atoms located at the two ends of a C_(4)chain,which is slightly higher in energy than the planar structure.The most stable structure of neutral Al_(2)C_(4)has a D∞h symmetry linear structure.The most stable structure of Al_(3)C_(4)^(−) anion is a planar structure with three Al atoms interacting with two C_(2)units.Whereas neutral Al_(3)C_(4)cluster has a C_(2v)symmetric V-shaped bent structure.The global minima structures of both Al_(4)C_(4)^(−) and neutral Al_(4)C_(4)are C_(2)h symmetry planar structures with four Al atoms interacting with the ends of two C_(2)units.Adaptive natural density partitioning analyses of Al_(n)C_(4)^(−)(n=2−4)clusters show that the interactions between the Al atoms and C_(2)units have bothσandπcharacters.展开更多
This study describes the development and validation of a sensitive and reliable method for determination of polybrominated diphenyl ethers(PBDEs)in atmospheric particulate matter using selective pressurized liquid e...This study describes the development and validation of a sensitive and reliable method for determination of polybrominated diphenyl ethers(PBDEs)in atmospheric particulate matter using selective pressurized liquid extraction(SPLE)and gas chromatography–mass spectrometry with a negative chemical ionization(GC-NCI-MS).Extraction and clean-up were performed using PLE with 2 g florisil and 3 g silica placed in the extraction cells.Under optimal conditions,14 PBDEs were extracted at 70℃ using hexane/dichloromethane(50:50,v/v)as solvent.Validation of SPLE returned excellent recoveries for most analytes,with relative standard deviations mostly below20%.Method detection limits ranged from 0.13 to15.38 ng·mL^-1 for the GC-MS analyses.The method was successfully applied to atmospheric particulate matter of Beijing,where analytes were detected in the range of182.79 to 468.99 pg·m^-3.展开更多
We have conducted a two-color visible-ultraviolet (VIS-UV) resonance-enhanced laser pho- toionization and pulsed field ionization-photoelectron (PFI-PE) study of gaseous vana- dium mononitride (VN) in the total ...We have conducted a two-color visible-ultraviolet (VIS-UV) resonance-enhanced laser pho- toionization and pulsed field ionization-photoelectron (PFI-PE) study of gaseous vana- dium mononitride (VN) in the total energy range of 56900-59020 cm-1. The VN molecules were selectively excited to single rotational levels of the intermediate VN(D3H0, v'=0) state by using a VIS dye laser prior to photoionization by employing a UV laser. This two-color scheme allows the measurements of rovibronically selected and re- solved PFI-PE spectra for the VN+(X2A; v+=0, 1, and 2) ion vibrational bands. By simulating the rotationally resolved PFI-PE spectra, J+=3/2 is determined to be the lowest rotational level of the ground electronic state, indicating that the symmetry of the ground VN+ electronic state is 2A3/2. The analysis of the PFI-PE spectra for VN+ also yields accurate values for the adiabatic ionization energy for the formation of VN+(X2A3/2), IE(VN)=56909.5+0.8 cm-1 (7.05588±0.00010 eV), the vibrational fre- quency wc+=1068.0±0.8 cm-1, the anharmonicity constant wc+Xe+=5.8±0.8 cm-1, the rotational constants Be+=0.6563±0.0005 cm-1 and ae+=0.0069±0.0004 cm-1, and the equi-librium bond length, re+=1.529A, for VN+(X2A3/2); along with the rotational constants Bc+=0.6578i0.0028 cm-1 and a+=0.0085±0.0028 cm-1, and the equilibrium bond length re+=1.527A for VN+(X2As/2), and the spin-orbit coupling constant A=153.3±0.8 cm-1 for VN+(X2/k5/2,3/2). The highly precise energetic and spectroscopic data obtained in the present study are valuable for benchmarking the predictions based on state-of-the-art ab initio quantum calculations.展开更多
The authenticity of 91 wines produced in Cyprus from both indigenous and other vine varieties were investigated by a holistic approach, using, advanced technology such as SNIF-NMR (site-specific natural isotopic frac...The authenticity of 91 wines produced in Cyprus from both indigenous and other vine varieties were investigated by a holistic approach, using, advanced technology such as SNIF-NMR (site-specific natural isotopic fractionation-nuclear magnetic resonance) and 1R-MS (isotope ratio-mass spectrometry) for the determination of the stable isotopes and ICP (inductively coupled plasma spectroscopy) for some heavy metals. The spectroscopic characteristics were evaluated statistically using different chemometric methods. The dependency of the D/H (deuterium/hydrogen) ratio of the methylene site in the ethanol molecule (D/H)ll and also theδ ^18O values of the wine water, were the most useful discriminators. Isotopic results allow us to have a complete idea about the regional variability of the isotopes. Among the metals, Ni followed by Pb was the ones with the highest discrimination value. The determined concentrations of Pb, Ni, Cr and Cd that are related to the safety of wines were within the acceptable limits that have been established by the OIV (international organization of vine and wine) or comparable with the results of the wines of other European countries. The study of the correlation between the load of heavy metals and isotopes in wines showed a dependence on the grape variety but not the geographical location of the vineyard. This is probably due to the close proximity of wine regions in Cyprus.展开更多
Room-temperature ferromagnetism is observed in the O^(+)-implanted AIN films with O+doses of 5×10^(16) cm^(-2)(AIN:Osxion)and 2×10^(17) cm^(-2)(AIN:O_(2x1on)).The observed magnetic anisotropy indicates that ...Room-temperature ferromagnetism is observed in the O^(+)-implanted AIN films with O+doses of 5×10^(16) cm^(-2)(AIN:Osxion)and 2×10^(17) cm^(-2)(AIN:O_(2x1on)).The observed magnetic anisotropy indicates that the ferromagnetism is attributed to the intrinsic properties of O^(+) -implanted AIN films.The out-of-plane saturation magnetization(Ms)of the AIN:O5×10^(16) is about 0.68 emu/g,much higher than that of AIN:O_(2x1017),0.09 emu/g,which is due to the excessively high O^(+)dose made more O+ions occupy adjacent A1^(3+)positions in forms of antiferromagnetic coupling.Doppler broadening of positron annihilation radiation measurements demonstrate the existence of Al vacancies in the O^(+)-implanted AIN films.The first-principles calculations suggest that the ferromagnetism originates mainly from the Al vacancies.Meanwhile,the formation of divacancies or vacancy clusters by high concentrations of Al vacancies will lead to the transformation of VA-VAi coupling from ferromagnetim to antiferromagnetism,ultimately weakening the ferromagnetism of the sample.展开更多
Photocatalytic hydrogen production coupled with selective oxidation of organic substrates to produce highvalue-added fine chemicals has drawn increasing attention.Herein,we report a noble metal-free photocatalyst for ...Photocatalytic hydrogen production coupled with selective oxidation of organic substrates to produce highvalue-added fine chemicals has drawn increasing attention.Herein,we report a noble metal-free photocatalyst for the highly efficient and simultaneous generation of hydrogen and the selective oxidation of benzyl alcohol into benzaldehyde over Cd S@Mo S2 heterostructures under visible light.Without the need for a sacrificial agent,Cd S@Mo S2 displayed an excellent hydrogen production rate of 4233μmol g^-1h^-1with0.3 mmol benzyl alcohol,which is approximately 53 times higher than that of bare Cd S nanorods(80μmol g^-1h^-1).The reaction system was highly selective for the oxidation of benzyl alcohol into benzaldehyde.When the amount of benzyl alcohol increased to 1.0 mmol,the hydrogen production reached9033μmol g^-1h^-1.Scanning electron microscopy and transmission electron microscopy images revealed that p-type Mo S2 sheets with a flower-like structure closely adhered to n-type semiconductor Cd S nanorods through the formation of a p-n heterojunction.As a potential Z-scheme photocatalyst,the Cd S@Mo S2 heterostructure effectively produces and separates electron-hole pairs under visible light.Thus,the electrons are used for reduction to generate hydrogen,and the holes oxidize benzyl alcohol into benzaldehyde.Moreover,a mechanism of photogenerated charge transfer and separation was proposed and verified by photoluminescence,electrochemical impedance spectroscopy,photocurrent and Mott-Schottky measurements.The results reveal that the Cd S@Mo S2 heterojunctions have rapid and efficient charge separation and transfer,thereby greatly improving benzyl alcohol dehydrogenation.This work provides insight into the rational design of high-performance Z-scheme photocatalysts and the use of holes and electrons to obtain two valuable chemicals simultaneously.展开更多
Electrochemical reductive exfoliation of graphite to few layered graphene(FLG) in presence of 1-ethyl-2,3-dimethyl imidazolium bis(trifluoromethylsulfonyl) imide ionic liquid and redox ionic liquid based ferrocene has...Electrochemical reductive exfoliation of graphite to few layered graphene(FLG) in presence of 1-ethyl-2,3-dimethyl imidazolium bis(trifluoromethylsulfonyl) imide ionic liquid and redox ionic liquid based ferrocene has been investigated. Thus, by applying a mild negative potential(-2.7 V vs. Fc/Fc^+) to carbon electrode in ionic liquid graphene flakes could be generated. The generated materials have been characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, high resolution transmission electron microscopy and atomic force microscopy. XPS and Raman analysis show that the electrochemical reductive exfoliation provides the formation of FLG. The thickness of the resulting FLG was found to be ranged between 4 and1 nm. HR-TEM images reveal the formation of few graphene layers and in some cases single graphene layer was observed.Moreover, this electrochemical route conduces to the formation of ionic liquid functionalized FLG. Finally, the reductive exfoliation was further investigated in the presence of redox ionic liquid. XPS and electrochemical measurements confirm the presence of ferrocene.展开更多
文摘第8届国际共振电离谱学及其应用会议(Eighth International Symposium on ResonanceIonization Spectroscopy and Its Applications)于1996年6月30日至7月5日在美国宾夕法尼亚州立大学召开。本届会议由田纳西大学共振电离谱学研究所和宾州州立大学联合主办。约100位科研工作者来自近30个国家,在会上发表论文109篇。其中我国清华大学2人,大连化物所、吉林大学各1名,在会上发表特邀报告1篇,口头报告2篇,展贴报告5篇。笔者的特邀报告"原子双里德堡态的自电离过程",引起了与会代表的关注。共振电离谱学是70年代发展起来的新兴研究领域,其主要特点是利用激光的高分辨率、高选择性,配合其他手段,实现高灵敏测量,以期在科学技术的各个领域中获得应用。
基金This work is supported by the National Natu- ral Science Foundation of China (No.51106146 and No.51036007), China Postdoctoral Science Foundation (No.20100480047 and No.201104326), Chinese Univer- sities Scientific Fund (No.WK2310000010), and Chinese Academy of Sciences.
文摘Pyrolysis of benzene at 30 Torr was studied from 1360 K to 1820 K in this work. Synchrotron vacuum ultraviolet photoionization mass spectrometry was employed to detect the pyroly- sis products such as radicals, isomers and polycyclic aromatic hydrocarbons, and measure their mole fraction profiles versus temperature. A low-pressure pyrolysis model of benzene was developed and validated by the experimental results. Rate of production analysis was performed to reveal the major reaction networks in both fuel decomposition and aromatic growth processes. It is concluded that benzene is mainly decomposed via H-abstraction reaction to produce phenyl and partly decomposed via unimolecular decomposition reac- tions to produce propargyl or phenyl. The decomposition process stops at the formation of acetylene and polyyne species like diacetylene and 1,3,5-hexatriyne due to their high thermal stabilities. Besides, the aromatic growth process in the low-pressure pyrolysis of benzene is concluded to initiate from benzene and phenyl, and is controlled by the even carbon growth mechanism due to the inhibited formation of C5 and C7 species which play important roles in the odd carbon growth mechanism.
基金Project(50542004) supported by the National Natural Science Foundation of ChinaProject(1960-71131100017) supported by Graduate Degree Thesis Innovation Foundation of Central South University,China
文摘LiNi1/3Co1/3Mn1/3O2 was coated with uniform nano-sized AlF3 layer by chemical precipitation method to improve its rate capability.The samples were characterized by X-ray diffractometry (XRD),transmission electron microscopy (TEM),energy dispersive spectroscopy (EDS),charge-discharge cycling,cyclic voltammetry (CV),and electrochemical impedance spectroscopy (EIS).Uniform coated layer with a thickness of about 3 nm was observed on the surface of LiNi1/3Co1/3Mn1/3O2 particle by TEM.At 0.5C and 2C rates,1.5% (mass fraction) AlF3-coated LiNi1/3Co1/3Mn1/3O2/Li in 2.8-4.3 V versus Li/Li+ after 80 cycles showed less than 3% of capacity fading,while those of the bare one were 16.5% and 45.9%,respectively.At 5C rate,the capacity retention of the coated sample after 50 cycles maintained 91.4% of the initial discharge capacity,while that of the bare one decreased to 52.6%.EIS result showed that a little change of charge transfer resistance of the coated sample resulting from uniform thin AlF3 layer was proposed as the main reason why its rate capability was improved obviously.CV result further indicated a greater reversibility for the electrode processes and better electrochemical performance of AlF3-coated layer.
基金supported by the National Natural Science Foundation of China (Grant No. 51131005)
文摘The current distributions over carbon steel under iron red alkyd primer exposed to 3.5% sodium chloride solution were mapped using the wire beam electrode (WBE). The electrochemical impedance spectroscopy (EIS) of the WBE was carded out to analyze the performance of coating delamination and corrosion behavior of carbon steel beneath defective coating. The EIS data revealed that protective capability of coating decreased with immersion time and the degree of cathodic delamination showed a rapid rise. The current density distribution of WBE indicated that cathodic sites was located at the defect at the beginning of immersion and gradually spread into the intact coating. The cathodic regions were distinguished from the anodic area and distributed over the WBE. The changes of cathodic sites could reflect the deterioration process of defective coating. The cathodic area ratio was a more useful parameter than the cathodic delamination degree to evaluate the coating cathodic delamination. The polarity reversals of electrodes at the defect and beneath coating were observed. A simple discussion of relationship between the blister and the polarity reversal was made from a standpoint of electrochemical distribution. WBE method was able to map and record the changes of local cathodic sites beneath defective coating in real time, which could provide more detailed information about the local degradation of coating.
文摘The Spurge family (Euphorbiaceae) is a large family of flowering plants. Two plant species of this family were collected from the Egyptian desert, extracted with methanol subjected to silica gel column chromatography to give six compounds, three compounds from each plant. The compounds isolated from the methanol extract of Euphorbia retusa Forssk were identified as kaempferol-3-beta-D glucopyranosyl (1), 3-O-alpha-L-xylopyranosyl (1→3)-alpha-L xylopyranosyl (1→2), beta-D glucopyranosyllup 1,12-diene-3,21-diol (2) and 5,7,8,3',4'-pentahydroxy-3-methoxyflavone (3) and the compounds isolated from Euphorbia paralais L. identified as 3,5,3'-trihydroxy-6,7-d-methoxy-4' (7"-hydroxygeranyl-1"-ether) flavones (4), 3-O-syringic acid (1→4)-alpha-L- xylopyranosyl (1→3), beta-D-rahminopyranosyl hederagenin (5) and 3-O-syringic acid (1→4), beta-D-rahminopyranosyl (1→3),beta-D-rahminopyranosyl hederagenin (6). The structure of the isolated compounds was elucidated by chemical and spectrometric analysis such as Infera red (IR), proton and carbon nuclear magnetic resonance (1H-, 13C-NMR) and chemical ionization mass spectrometry (CI-MS).
基金Supported by the National Natural Science Foundation of China(51074096)
文摘The Li Ni1/3Co1/3Mn1/3O2 is first obtained by the controlled crystallization method and then coated with Ni3(PO4)2particles. The effects of the coating on rate capability and cycle life at high cut-off voltage are investigated by electrochemical impedance spectroscopy and galvanostatic measurements. The element ratio of Ni:Mn:Co is tested by inductively-coupled plasma spectrometer(ICP) analysis and it testified to be 1:1:1. It is indicated that Ni3(PO4)2-coated Li Ni1/3Co1/3Mn1/3O2 has an outstanding capacity retention, where 99% capacity retention is maintained after 10 cycles at 5C discharge rate between 2.7 V and 4.6 V. The electrochemical impedance spectroscopy(EIS) results show that the current exchange density i0 of the coated sample is higher than that of Li Ni1/3Co1/3Mn1/3O2, which is beneficial to its electrochemical performances. All the conclusions show that the Ni3(PO4)2coating can prominently enhance the high rate performance of the Li Ni1/3Co1/3Mn1/3O2, especially at high cut-off voltage.
基金supported by the National Key Research and Development Program of China(No.2017YFA0303500)the National Natural Science Foundation of China(No.11674302)。
文摘In this work,electron energy spectroscopic mapping of surface plasmon of Ag nanostructures on highly oriented pyrolytic graphite is reported.Benefitting from the angular dispersive feature of the present scanning probe electron energy spectrometer,a multi-channel detection mode is developed.By scanning along one direction,the two-dimensional intensity distribution of Ag surface plasmon excitation due to the collision of electron emitted from the tip can be obtained in parallel.The spectroscopic spatial resolution is determined to be around 80 nm.
基金This work was supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (No.KZCX2-YW-205) and the Hundred Talents Fund, the 973 Program of Ministry of Science and Technology of China (No.2006CB403701), and the National Natural Science Foundation of China (No.20577052, No.20673123, No.20473094, and No.20503035).
文摘Trichloromethanesulfenyl thiocyanate, CCl3SSCN, was generated and studied by photoelectron spectroscopy (PES), photoionization mass spectroscopy (PIMS), and theoretical calculations. This molecule exhibits a gauche conformation, and the torsional angle around S-S bond is 91.4° due to the sulfur-sulfur lone pair interactions. After ionization, the ground-state cationic-radical form of CCl3SSCN+ adopts a trans planar main-atom structure with Cs symmetry. The highest occupied molecular orbital (HOMO) of CC13SSCN corresponds to the electrons mainly localized on the sulfur 3p lone pair MO. The first ionization energy is determined to be 10.40 cV.
基金supported by the Beijing Municipal Science&Technology Commission(No.Z191100007219009)the National Natural Science Foundation of China(No.21773255)。
文摘We measured the photoelectron spectra of Al_(n)C_(4)^(−)(n=2−4)clusters by using size-selected anion photoelectron spectroscopy.The structures of Al_(n)C_(4)^(−/0)(n=2−4)clusters were explored with quantum chemistry calculations and were determined by comparing the theoretical results with the experimental spectra.It is found that the most stable structure of Al_(2)C_(4)^(−) anion is a C_(2v)symmetry planar structure with two Al atoms interacting with two C_(2)units.In addition,Al_(2)C_(4)^(−) anion also has a D∞h symmetry linear structure with two Al atoms located at the two ends of a C_(4)chain,which is slightly higher in energy than the planar structure.The most stable structure of neutral Al_(2)C_(4)has a D∞h symmetry linear structure.The most stable structure of Al_(3)C_(4)^(−) anion is a planar structure with three Al atoms interacting with two C_(2)units.Whereas neutral Al_(3)C_(4)cluster has a C_(2v)symmetric V-shaped bent structure.The global minima structures of both Al_(4)C_(4)^(−) and neutral Al_(4)C_(4)are C_(2)h symmetry planar structures with four Al atoms interacting with the ends of two C_(2)units.Adaptive natural density partitioning analyses of Al_(n)C_(4)^(−)(n=2−4)clusters show that the interactions between the Al atoms and C_(2)units have bothσandπcharacters.
基金supported by the National Natural Science Foundation of China(41325010)
文摘This study describes the development and validation of a sensitive and reliable method for determination of polybrominated diphenyl ethers(PBDEs)in atmospheric particulate matter using selective pressurized liquid extraction(SPLE)and gas chromatography–mass spectrometry with a negative chemical ionization(GC-NCI-MS).Extraction and clean-up were performed using PLE with 2 g florisil and 3 g silica placed in the extraction cells.Under optimal conditions,14 PBDEs were extracted at 70℃ using hexane/dichloromethane(50:50,v/v)as solvent.Validation of SPLE returned excellent recoveries for most analytes,with relative standard deviations mostly below20%.Method detection limits ranged from 0.13 to15.38 ng·mL^-1 for the GC-MS analyses.The method was successfully applied to atmospheric particulate matter of Beijing,where analytes were detected in the range of182.79 to 468.99 pg·m^-3.
文摘We have conducted a two-color visible-ultraviolet (VIS-UV) resonance-enhanced laser pho- toionization and pulsed field ionization-photoelectron (PFI-PE) study of gaseous vana- dium mononitride (VN) in the total energy range of 56900-59020 cm-1. The VN molecules were selectively excited to single rotational levels of the intermediate VN(D3H0, v'=0) state by using a VIS dye laser prior to photoionization by employing a UV laser. This two-color scheme allows the measurements of rovibronically selected and re- solved PFI-PE spectra for the VN+(X2A; v+=0, 1, and 2) ion vibrational bands. By simulating the rotationally resolved PFI-PE spectra, J+=3/2 is determined to be the lowest rotational level of the ground electronic state, indicating that the symmetry of the ground VN+ electronic state is 2A3/2. The analysis of the PFI-PE spectra for VN+ also yields accurate values for the adiabatic ionization energy for the formation of VN+(X2A3/2), IE(VN)=56909.5+0.8 cm-1 (7.05588±0.00010 eV), the vibrational fre- quency wc+=1068.0±0.8 cm-1, the anharmonicity constant wc+Xe+=5.8±0.8 cm-1, the rotational constants Be+=0.6563±0.0005 cm-1 and ae+=0.0069±0.0004 cm-1, and the equi-librium bond length, re+=1.529A, for VN+(X2A3/2); along with the rotational constants Bc+=0.6578i0.0028 cm-1 and a+=0.0085±0.0028 cm-1, and the equilibrium bond length re+=1.527A for VN+(X2As/2), and the spin-orbit coupling constant A=153.3±0.8 cm-1 for VN+(X2/k5/2,3/2). The highly precise energetic and spectroscopic data obtained in the present study are valuable for benchmarking the predictions based on state-of-the-art ab initio quantum calculations.
文摘The authenticity of 91 wines produced in Cyprus from both indigenous and other vine varieties were investigated by a holistic approach, using, advanced technology such as SNIF-NMR (site-specific natural isotopic fractionation-nuclear magnetic resonance) and 1R-MS (isotope ratio-mass spectrometry) for the determination of the stable isotopes and ICP (inductively coupled plasma spectroscopy) for some heavy metals. The spectroscopic characteristics were evaluated statistically using different chemometric methods. The dependency of the D/H (deuterium/hydrogen) ratio of the methylene site in the ethanol molecule (D/H)ll and also theδ ^18O values of the wine water, were the most useful discriminators. Isotopic results allow us to have a complete idea about the regional variability of the isotopes. Among the metals, Ni followed by Pb was the ones with the highest discrimination value. The determined concentrations of Pb, Ni, Cr and Cd that are related to the safety of wines were within the acceptable limits that have been established by the OIV (international organization of vine and wine) or comparable with the results of the wines of other European countries. The study of the correlation between the load of heavy metals and isotopes in wines showed a dependence on the grape variety but not the geographical location of the vineyard. This is probably due to the close proximity of wine regions in Cyprus.
文摘Room-temperature ferromagnetism is observed in the O^(+)-implanted AIN films with O+doses of 5×10^(16) cm^(-2)(AIN:Osxion)and 2×10^(17) cm^(-2)(AIN:O_(2x1on)).The observed magnetic anisotropy indicates that the ferromagnetism is attributed to the intrinsic properties of O^(+) -implanted AIN films.The out-of-plane saturation magnetization(Ms)of the AIN:O5×10^(16) is about 0.68 emu/g,much higher than that of AIN:O_(2x1017),0.09 emu/g,which is due to the excessively high O^(+)dose made more O+ions occupy adjacent A1^(3+)positions in forms of antiferromagnetic coupling.Doppler broadening of positron annihilation radiation measurements demonstrate the existence of Al vacancies in the O^(+)-implanted AIN films.The first-principles calculations suggest that the ferromagnetism originates mainly from the Al vacancies.Meanwhile,the formation of divacancies or vacancy clusters by high concentrations of Al vacancies will lead to the transformation of VA-VAi coupling from ferromagnetim to antiferromagnetism,ultimately weakening the ferromagnetism of the sample.
基金supported by the National Key Research and Development Program of China(2017YFA0700102)the National Natural Science Foundation of China(21520102001,21871263 and 21671188)+1 种基金the Key Research Program of Frontier Sciences,CAS(QYZDJ-SSW-SLH045)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB20000000)。
文摘Photocatalytic hydrogen production coupled with selective oxidation of organic substrates to produce highvalue-added fine chemicals has drawn increasing attention.Herein,we report a noble metal-free photocatalyst for the highly efficient and simultaneous generation of hydrogen and the selective oxidation of benzyl alcohol into benzaldehyde over Cd S@Mo S2 heterostructures under visible light.Without the need for a sacrificial agent,Cd S@Mo S2 displayed an excellent hydrogen production rate of 4233μmol g^-1h^-1with0.3 mmol benzyl alcohol,which is approximately 53 times higher than that of bare Cd S nanorods(80μmol g^-1h^-1).The reaction system was highly selective for the oxidation of benzyl alcohol into benzaldehyde.When the amount of benzyl alcohol increased to 1.0 mmol,the hydrogen production reached9033μmol g^-1h^-1.Scanning electron microscopy and transmission electron microscopy images revealed that p-type Mo S2 sheets with a flower-like structure closely adhered to n-type semiconductor Cd S nanorods through the formation of a p-n heterojunction.As a potential Z-scheme photocatalyst,the Cd S@Mo S2 heterostructure effectively produces and separates electron-hole pairs under visible light.Thus,the electrons are used for reduction to generate hydrogen,and the holes oxidize benzyl alcohol into benzaldehyde.Moreover,a mechanism of photogenerated charge transfer and separation was proposed and verified by photoluminescence,electrochemical impedance spectroscopy,photocurrent and Mott-Schottky measurements.The results reveal that the Cd S@Mo S2 heterojunctions have rapid and efficient charge separation and transfer,thereby greatly improving benzyl alcohol dehydrogenation.This work provides insight into the rational design of high-performance Z-scheme photocatalysts and the use of holes and electrons to obtain two valuable chemicals simultaneously.
基金supported by the European Community Seventh Framework Programme(266391)
文摘Electrochemical reductive exfoliation of graphite to few layered graphene(FLG) in presence of 1-ethyl-2,3-dimethyl imidazolium bis(trifluoromethylsulfonyl) imide ionic liquid and redox ionic liquid based ferrocene has been investigated. Thus, by applying a mild negative potential(-2.7 V vs. Fc/Fc^+) to carbon electrode in ionic liquid graphene flakes could be generated. The generated materials have been characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, high resolution transmission electron microscopy and atomic force microscopy. XPS and Raman analysis show that the electrochemical reductive exfoliation provides the formation of FLG. The thickness of the resulting FLG was found to be ranged between 4 and1 nm. HR-TEM images reveal the formation of few graphene layers and in some cases single graphene layer was observed.Moreover, this electrochemical route conduces to the formation of ionic liquid functionalized FLG. Finally, the reductive exfoliation was further investigated in the presence of redox ionic liquid. XPS and electrochemical measurements confirm the presence of ferrocene.