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2003 Volume 19 Issue 9
2003, 19(09): 785-790
doi: 10.3866/PKU.WHXB20030901
Abstract:
A series of novel La1－xSrxNi1－yCoyO3（x= 0, 0.1, 0.2, 0.5； y=0～1.0）perovskite oxides were prepared by sol-gel method and characterized by XRD and XPS. The activity of bifunctional oxygen electrodes made by the perovskite-type catalyst dispersed on active carbon was investigated using electrochemical impedance spectroscopy (EIS). The impedance spectra of both cathodic and anodic polarization were analyzed. The results show that the properties of electrodes are improved by doping Co3＋ ions on B site because the concentration of B site ions on the catalysts surface are increased. But by doping Sr2＋ ions on A site could impair the effect because the ordering level of oxygen vacancy and the electrode resistance are increased. The polarization resistance is mainly caused by the slow Nernstian diffusion and charge transfer reaction and not by concentration of adsorption of oxygen species and oxygen vacancy. So it is concluded that by increasing the concentration of B site ions on perovskite oxide surface and improving the thickness of electrolyte film the performance of oxygen electrodes could by improved.
A series of novel La1－xSrxNi1－yCoyO3（x= 0, 0.1, 0.2, 0.5； y=0～1.0）perovskite oxides were prepared by sol-gel method and characterized by XRD and XPS. The activity of bifunctional oxygen electrodes made by the perovskite-type catalyst dispersed on active carbon was investigated using electrochemical impedance spectroscopy (EIS). The impedance spectra of both cathodic and anodic polarization were analyzed. The results show that the properties of electrodes are improved by doping Co3＋ ions on B site because the concentration of B site ions on the catalysts surface are increased. But by doping Sr2＋ ions on A site could impair the effect because the ordering level of oxygen vacancy and the electrode resistance are increased. The polarization resistance is mainly caused by the slow Nernstian diffusion and charge transfer reaction and not by concentration of adsorption of oxygen species and oxygen vacancy. So it is concluded that by increasing the concentration of B site ions on perovskite oxide surface and improving the thickness of electrolyte film the performance of oxygen electrodes could by improved.
2003, 19(09): 791-794
doi: 10.3866/PKU.WHXB20030902
Abstract:
The effects of thermal history of liquid metal Al on its solidification microstructures have been studied by using molecular dynamics simulation. It has been found that under different thermal history conditions, in the same system, both the 1551 bond-type and the icosahedron (expressed by (12 0 12 0)) related to the 1551 bond-type play a remarkable role during microstructure transitions (see Fig.4). The number of repeatable icosahedra not always increased with the decrease of temperature and has a maximum during the isothermal runs at given temperatures (see Fig.6). The maximum point corresponds to the glass transition temperature Tg, and can be moved under different thermal history conditions. It is also demonstrated that the thermal history conditions seriously influence the solidification microstructures and their effects are mainly demonstrated after the glass transition point. These results give a new way to understand and control the microstructure transitions during solidification processes.
The effects of thermal history of liquid metal Al on its solidification microstructures have been studied by using molecular dynamics simulation. It has been found that under different thermal history conditions, in the same system, both the 1551 bond-type and the icosahedron (expressed by (12 0 12 0)) related to the 1551 bond-type play a remarkable role during microstructure transitions (see Fig.4). The number of repeatable icosahedra not always increased with the decrease of temperature and has a maximum during the isothermal runs at given temperatures (see Fig.6). The maximum point corresponds to the glass transition temperature Tg, and can be moved under different thermal history conditions. It is also demonstrated that the thermal history conditions seriously influence the solidification microstructures and their effects are mainly demonstrated after the glass transition point. These results give a new way to understand and control the microstructure transitions during solidification processes.
2003, 19(09): 795-799
doi: 10.3866/PKU.WHXB20030903
Abstract:
Polyaniline (PANI)-C60 composites film was prepared by liquid-state mixture of PANI and C60 solutions. The interaction between polyaniline emerald base and C60 were investigated and explained according to the results of FTIR spectroscopy. The improvement of crystallinity of PANI-C60 composites was evaluated by using X-ray diffraction spectra (XRD). The mechanism of charge transport in these composites was also studied. The photoconductivity of PANI-C60 composites film was enhanced markedly and photoluminescence spectra (PL) intensity decreased greatly, which take the photoinduced charge transfer between PANI and C60 into consideration.
Polyaniline (PANI)-C60 composites film was prepared by liquid-state mixture of PANI and C60 solutions. The interaction between polyaniline emerald base and C60 were investigated and explained according to the results of FTIR spectroscopy. The improvement of crystallinity of PANI-C60 composites was evaluated by using X-ray diffraction spectra (XRD). The mechanism of charge transport in these composites was also studied. The photoconductivity of PANI-C60 composites film was enhanced markedly and photoluminescence spectra (PL) intensity decreased greatly, which take the photoinduced charge transfer between PANI and C60 into consideration.
2003, 19(09): 800-804
doi: 10.3866/PKU.WHXB20030904
Abstract:
A promoter-probe plasmid pKK232-8 was used as a vector, which functioned in eubacteria Escherichia(E.) coli HB101. The promoter function of the chromosome DNA fragment from Halobacterium(H.) halobium R1, RM13 DNA fragment, active as eubacteria promoters in E.coli HB101, was studied by microcalorimetry. The promoter is of about 1000 bp(base pair).It can promote the chloramphenicol acetyltransferase (CAT) gene in plasmid pKK232-8, and the chloramphenicol resistance level is about 150 mg•L－1.The result indicates that there are probably double-function promoters in H.halobium chromosome.
A promoter-probe plasmid pKK232-8 was used as a vector, which functioned in eubacteria Escherichia(E.) coli HB101. The promoter function of the chromosome DNA fragment from Halobacterium(H.) halobium R1, RM13 DNA fragment, active as eubacteria promoters in E.coli HB101, was studied by microcalorimetry. The promoter is of about 1000 bp(base pair).It can promote the chloramphenicol acetyltransferase (CAT) gene in plasmid pKK232-8, and the chloramphenicol resistance level is about 150 mg•L－1.The result indicates that there are probably double-function promoters in H.halobium chromosome.
2003, 19(09): 805-809
doi: 10.3866/PKU.WHXB20030905
Abstract:
The distribution of aluminum in the zeolite MCM-22 lattice has been investigated by 27Al MQ MAS NMR and quantum chemical calculation. Three different aluminum species in tetrahedral coordination were clearly observed in the 2D 5Q MAS NMR spectrum of zeolite MCM-22. From the spectrum, we can calculate the isotropic chemical shifts(δ 50.5, δ 57.3, δ 62.4 ) and the quadrupolar coupling constant (1.74, 1.68, 1.92 MHz) of the three species. The structure of MCM-22 has the 8 crystallographically distinct T sites. From the simulated 27Al 5Q MAS NMR spectrum, it is evident that 8 T sites can be divided into 3 groups. Sites T2 and T6 correspond to the signals at δ 61, δ 49, respectively; while sites T1, T3, T4, T5, T7, T8 give rise to signal atδ 56. Al is randomly distributed in the framework of MCM-22 zeolite when the Si/Al atom ratio is varied from 10 to 15.
The distribution of aluminum in the zeolite MCM-22 lattice has been investigated by 27Al MQ MAS NMR and quantum chemical calculation. Three different aluminum species in tetrahedral coordination were clearly observed in the 2D 5Q MAS NMR spectrum of zeolite MCM-22. From the spectrum, we can calculate the isotropic chemical shifts(δ 50.5, δ 57.3, δ 62.4 ) and the quadrupolar coupling constant (1.74, 1.68, 1.92 MHz) of the three species. The structure of MCM-22 has the 8 crystallographically distinct T sites. From the simulated 27Al 5Q MAS NMR spectrum, it is evident that 8 T sites can be divided into 3 groups. Sites T2 and T6 correspond to the signals at δ 61, δ 49, respectively; while sites T1, T3, T4, T5, T7, T8 give rise to signal atδ 56. Al is randomly distributed in the framework of MCM-22 zeolite when the Si/Al atom ratio is varied from 10 to 15.
2003, 19(09): 810-814
doi: 10.3866/PKU.WHXB20030906
Abstract:
The doped polyaniline (PANI) films with different thickness electrodeposited on flat platinum electrode surface have been studied by confocal Raman spectroscopy. It was found that the overall features of the Raman spectra depend strongly on the confocal depth. Therefore, it can be deduced that the doping level of the PANI film increases with film thickness during film growing process. X-ray photoelectron spectroscopic (XPS) analysis and ultraviolet-visible (UV) absorption spectrum results also confirmed this idea.
The doped polyaniline (PANI) films with different thickness electrodeposited on flat platinum electrode surface have been studied by confocal Raman spectroscopy. It was found that the overall features of the Raman spectra depend strongly on the confocal depth. Therefore, it can be deduced that the doping level of the PANI film increases with film thickness during film growing process. X-ray photoelectron spectroscopic (XPS) analysis and ultraviolet-visible (UV) absorption spectrum results also confirmed this idea.
2003, 19(09): 815-818
doi: 10.3866/PKU.WHXB20030907
Abstract:
The adsorption of O2 at oxygen vacancy site (F, F＋ or F2＋site) and magnesium vacancy site (V, V－ or V2－ site) has been studied using cluster models embedding in a large array of point charges coupled to density functional method at B3LYP/6-31G(d) level. The value of point charges is determined by the self-consistent technique. The calculated results indicate that the M (001) surface with oxygen vacancies has more excellent catalyst structure contributing to the adsorptive-decomposition of O2 in comparison with the low-coordinated corner site in the previous study. The adsorption energies for O2 adsorbed on M (001) surface with oxygen vacancies are larger than those on M (001) surface with magnesium vacancies. Moreover, the M (001) surface with magnesium vacancies hardly exhibits catalytic reactivity toward O2 decomposition. The Mülliken charge analysis illustrates that, for O2 adsorption on M (001) surface with oxygen vacancies, the electrons are transferred from the substrate to the adsorbed O2 and occupy the anti-bonding orbital, π* of O2. Thus, the O－O bond strength is weakened. Potential energy curve shows that the energy barrier is considerably decreased for O2 adsorbed at oxygen vacancy site of M (001) surface when compared to that at corner site in our previous study.
The adsorption of O2 at oxygen vacancy site (F, F＋ or F2＋site) and magnesium vacancy site (V, V－ or V2－ site) has been studied using cluster models embedding in a large array of point charges coupled to density functional method at B3LYP/6-31G(d) level. The value of point charges is determined by the self-consistent technique. The calculated results indicate that the M (001) surface with oxygen vacancies has more excellent catalyst structure contributing to the adsorptive-decomposition of O2 in comparison with the low-coordinated corner site in the previous study. The adsorption energies for O2 adsorbed on M (001) surface with oxygen vacancies are larger than those on M (001) surface with magnesium vacancies. Moreover, the M (001) surface with magnesium vacancies hardly exhibits catalytic reactivity toward O2 decomposition. The Mülliken charge analysis illustrates that, for O2 adsorption on M (001) surface with oxygen vacancies, the electrons are transferred from the substrate to the adsorbed O2 and occupy the anti-bonding orbital, π* of O2. Thus, the O－O bond strength is weakened. Potential energy curve shows that the energy barrier is considerably decreased for O2 adsorbed at oxygen vacancy site of M (001) surface when compared to that at corner site in our previous study.
2003, 19(09): 819-823
doi: 10.3866/PKU.WHXB20030908
Abstract:
The preparation of monolithic silica aerogels via non-supercritical drying is realized by the following procedures:(1) formation of silica alcogels with perfect network structure by controlling two-step hydrolysis and condensation reaction rates of tetraethoxysilane； (2) improvement and reinforcement of network structure and strength of silica gels through exchanging the pore fluid with ethanol solvent thoroughly, immersing of gels in the ethanol solutions of tetraethyoxysilane and aging; (3) gradual drying under ethanol fluid whose surface tension is much lower than water under ambient pressure. The resulting aerogels were characterized by means of SEM， TEM, TG-DTA, XRD, and adsorption-desorption techniques. It is found that the aerogels, which are made up of uniform spherical nanoparticles with diameters of about 10 nm, are of coherent network structures. Furthermore, the aerogels are porous, and the porosity is as high as 91％. The diameter of the pore sizes is in the range of 10～30 nm, and the density of the aerogels is low（200～400 kg•m－3）. The specific surface area of the aerogels can be as high as 625.65 m2•g－1. The appearance， microstructure，diameters of primary particles and pore size distributions of the aerogels are in concordance with those prepared by conventional supercritical drying. It is demonstrated that the quality of the resulting aerogels is affected by the preparation conditions adopted in the preparation process. In fact, by adjusting the proportions of the reaction systems， and controlling the adding amounts of acid and base during the two-step hydrolysis and condensation process，silica aerogels with required density， definite strength and ideal morphology can be produced.
The preparation of monolithic silica aerogels via non-supercritical drying is realized by the following procedures:(1) formation of silica alcogels with perfect network structure by controlling two-step hydrolysis and condensation reaction rates of tetraethoxysilane； (2) improvement and reinforcement of network structure and strength of silica gels through exchanging the pore fluid with ethanol solvent thoroughly, immersing of gels in the ethanol solutions of tetraethyoxysilane and aging; (3) gradual drying under ethanol fluid whose surface tension is much lower than water under ambient pressure. The resulting aerogels were characterized by means of SEM， TEM, TG-DTA, XRD, and adsorption-desorption techniques. It is found that the aerogels, which are made up of uniform spherical nanoparticles with diameters of about 10 nm, are of coherent network structures. Furthermore, the aerogels are porous, and the porosity is as high as 91％. The diameter of the pore sizes is in the range of 10～30 nm, and the density of the aerogels is low（200～400 kg•m－3）. The specific surface area of the aerogels can be as high as 625.65 m2•g－1. The appearance， microstructure，diameters of primary particles and pore size distributions of the aerogels are in concordance with those prepared by conventional supercritical drying. It is demonstrated that the quality of the resulting aerogels is affected by the preparation conditions adopted in the preparation process. In fact, by adjusting the proportions of the reaction systems， and controlling the adding amounts of acid and base during the two-step hydrolysis and condensation process，silica aerogels with required density， definite strength and ideal morphology can be produced.
2003, 19(09): 824-828
doi: 10.3866/PKU.WHXB20030909
Abstract:
Nanoparticle spinel MnFe1.95Ru0.05O4 catalyst was prepared via wet chemical method and the influence of Cu additive on this catalyst was investigated. The specific surface area and pore volume of the catalyst were increased by adding Cu additive. The results of XPS demonstrate that the chemical environment of elements such as Mn and Fe was greatly influenced by Ru modification while hardly influenced by Cu additive; however, the chemical environment of Ru was affected by Cu additive. The results of EXAFS characterization demonstrate the newly formed active Ru=O bond, which is attributed to Cu additive. The influence of Cu additive on catalytic activity was studied using the oxidations of cinnamyl alcohol and benzyl alcohol as typical reactions.
Nanoparticle spinel MnFe1.95Ru0.05O4 catalyst was prepared via wet chemical method and the influence of Cu additive on this catalyst was investigated. The specific surface area and pore volume of the catalyst were increased by adding Cu additive. The results of XPS demonstrate that the chemical environment of elements such as Mn and Fe was greatly influenced by Ru modification while hardly influenced by Cu additive; however, the chemical environment of Ru was affected by Cu additive. The results of EXAFS characterization demonstrate the newly formed active Ru=O bond, which is attributed to Cu additive. The influence of Cu additive on catalytic activity was studied using the oxidations of cinnamyl alcohol and benzyl alcohol as typical reactions.
2003, 19(09): 829-833
doi: 10.3866/PKU.WHXB20030910
Abstract:
Uniform and transparent nanoscale SiO2-TiO2 complex thin films with thickness of about 100 nm were prepared by sol method on glass substrates at room temperature in air. The photo-induced activity of the films has been measured. The effect of annealing on the hydrophilicity and the photocatalysis activity of the films were studied. The chemical states of the elements on the surface and near the surface were measured by XPS. The results show that the Ti in/on the surface of the films exists not only as Ti4＋ but also as Ti3＋.At the same time, part of the Ti4＋ has been changed to Ti3＋ after UV irradiation. The crystal structure of the TiO2 in the SiO2-TiO2 film is mainly anatase as shown by XRD and the crystal grain size is about 14～20 nm. The AFM was used to study the morphology of the films annealed at different temperatures.
Uniform and transparent nanoscale SiO2-TiO2 complex thin films with thickness of about 100 nm were prepared by sol method on glass substrates at room temperature in air. The photo-induced activity of the films has been measured. The effect of annealing on the hydrophilicity and the photocatalysis activity of the films were studied. The chemical states of the elements on the surface and near the surface were measured by XPS. The results show that the Ti in/on the surface of the films exists not only as Ti4＋ but also as Ti3＋.At the same time, part of the Ti4＋ has been changed to Ti3＋ after UV irradiation. The crystal structure of the TiO2 in the SiO2-TiO2 film is mainly anatase as shown by XRD and the crystal grain size is about 14～20 nm. The AFM was used to study the morphology of the films annealed at different temperatures.
2003, 19(09): 834-838
doi: 10.3866/PKU.WHXB20030911
Abstract:
The transcriptional activator GCN4 plays a key role in the regulation of amino acid anabolism in yeast. It is a DNA binding protein that has typical bZIP domain. We synthesized the basic region (226-252) of natural protein GCN4, and introduced a Trp residue at the N-terminal. CD experimental data show that the synthesized monomer peptide, GCN4-W, can still specifically recognize the DNA target sites AP-1 and ATF/CREB. We also obtained the apparent dissociation constant of the peptide-DNA complex of this monomer recognizing DNA site by fluorescence titration method.
The transcriptional activator GCN4 plays a key role in the regulation of amino acid anabolism in yeast. It is a DNA binding protein that has typical bZIP domain. We synthesized the basic region (226-252) of natural protein GCN4, and introduced a Trp residue at the N-terminal. CD experimental data show that the synthesized monomer peptide, GCN4-W, can still specifically recognize the DNA target sites AP-1 and ATF/CREB. We also obtained the apparent dissociation constant of the peptide-DNA complex of this monomer recognizing DNA site by fluorescence titration method.
2003, 19(09): 839-843
doi: 10.3866/PKU.WHXB20030912
Abstract:
In this paper several functional materials, such as Li2Mg2Si4O10F2 (LHT), H2Mn8O16•1.4H2O (CRYMO) and Li1.3Ti1.7Al0.3(PO4)3 (LTAP), were investigated in order to separate respectively iron, potassium and sodium impurities from the aqueous solution of high-concentration lithium chloride. The experimental results show that these functional materials have very high ion exchange selectivity to Fe3＋, K＋ and Na＋, respectively. And these functional materials are effective for the separation of impurities from high-concentration lithium chloride solution. The ion exchange behavior of these functional materials with impurities in high-concentration lithium chloride solution was analyzed and discussed. It is shown that the ion exchange kinetics of the Li2Mg2Si4O10F2, H2Mn8O16•1.4H2O and Li1.3Ti1.7Al0.3(PO4)3 with Fe3＋, K＋ and Na＋ respectively in high-concentration lithium chloride solution can be represented approximately by the equation of JMAK.
In this paper several functional materials, such as Li2Mg2Si4O10F2 (LHT), H2Mn8O16•1.4H2O (CRYMO) and Li1.3Ti1.7Al0.3(PO4)3 (LTAP), were investigated in order to separate respectively iron, potassium and sodium impurities from the aqueous solution of high-concentration lithium chloride. The experimental results show that these functional materials have very high ion exchange selectivity to Fe3＋, K＋ and Na＋, respectively. And these functional materials are effective for the separation of impurities from high-concentration lithium chloride solution. The ion exchange behavior of these functional materials with impurities in high-concentration lithium chloride solution was analyzed and discussed. It is shown that the ion exchange kinetics of the Li2Mg2Si4O10F2, H2Mn8O16•1.4H2O and Li1.3Ti1.7Al0.3(PO4)3 with Fe3＋, K＋ and Na＋ respectively in high-concentration lithium chloride solution can be represented approximately by the equation of JMAK.
2003, 19(09): 844-848
doi: 10.3866/PKU.WHXB20030913
Abstract:
Various Ni-15％ Sm3＋(x) doped CeO2(Ni-SDC)composite anodes prepared by impregnation method were studied to unveil the role of SDC in improving the performance of Ni anode. The electrochemical properties and the power generation characteristics of the cells based on these anodes show that the performance of the cells were improved significantly by the addition of SDC into Ni due to the reduced ohmic resistance and anodic overpotential. The decrease of anodic overpotential after the introduction of SDC could be due to the extension of three-phase-boundary (TPB) and the increase of active sites for H2 oxidation. However, the introduction of SDC also leaded to an increase of activation energy, which resulted in a higher anodic overpotential for Ni-SDC anodes at low temperatures compared with pure Ni. The impedance spectra of Ni-SDC anode consisted of two arcs at high temperatures. The high frequency arc increased with the amount of SDC, while the low frequency arc showed no dependency on the amount of SDC. The high frequency arc could be related to the charge transfer reaction at TPB, and the low frequency arc could correspond to the disassociative adsorption of H2 and the following diffusion processes. 75％(w) Ni-25％(w) SDC/LSGM/SSC exhibited the highest power density among the cells studied, and the highest power density at 1073, 973, 873 K reached 1.1, 0.43, 0.14 W•cm－2, respectively. The cells also showed od stability.
Various Ni-15％ Sm3＋(x) doped CeO2(Ni-SDC)composite anodes prepared by impregnation method were studied to unveil the role of SDC in improving the performance of Ni anode. The electrochemical properties and the power generation characteristics of the cells based on these anodes show that the performance of the cells were improved significantly by the addition of SDC into Ni due to the reduced ohmic resistance and anodic overpotential. The decrease of anodic overpotential after the introduction of SDC could be due to the extension of three-phase-boundary (TPB) and the increase of active sites for H2 oxidation. However, the introduction of SDC also leaded to an increase of activation energy, which resulted in a higher anodic overpotential for Ni-SDC anodes at low temperatures compared with pure Ni. The impedance spectra of Ni-SDC anode consisted of two arcs at high temperatures. The high frequency arc increased with the amount of SDC, while the low frequency arc showed no dependency on the amount of SDC. The high frequency arc could be related to the charge transfer reaction at TPB, and the low frequency arc could correspond to the disassociative adsorption of H2 and the following diffusion processes. 75％(w) Ni-25％(w) SDC/LSGM/SSC exhibited the highest power density among the cells studied, and the highest power density at 1073, 973, 873 K reached 1.1, 0.43, 0.14 W•cm－2, respectively. The cells also showed od stability.
2003, 19(09): 849-853
doi: 10.3866/PKU.WHXB20030914
Abstract:
An interlayer of samaria doped ceria(SDC) was prepared between Ni-SDC composite electrode and LSGM(La0.9Sr0.1Ga0.8Mg0.2O3) electrolyte using screen-printing method to improve the performance of Ni anodes. The effect of this interlayer on the performance of anode as well as the cell was studied using various electrochemical techniques. The results show that addition of the SDC interlayer reduced the anodic over-potential significantly, however, the ohmic resistance of the cell with an SDC interlayer increased, which leaded to a decrease of the power output. The electrochemical oxidation of H2 on Ni-SDC anodes was controlled by two processes, which corresponded to two arcs in the impedance spectra. The high frequency arc decreased with the addition of SDC interlayer, and could correspond to the electrochemical reaction at three-phase-boundary (TPB) or the transfer of oxygen ions from LSGM to SDC. The low frequency arc showed no dependency on the addition of SDC, and could be related to the adsorption and diffusion of H2 at the surface of electrode. The cells with an SDC interlayer showed much better stability compared with the cell using single layer anode, and the performance of the cell with Ni-SDC/SDC (1573 K) anode was higher than the cell with a single layer Ni-SDC anode after long time running.
An interlayer of samaria doped ceria(SDC) was prepared between Ni-SDC composite electrode and LSGM(La0.9Sr0.1Ga0.8Mg0.2O3) electrolyte using screen-printing method to improve the performance of Ni anodes. The effect of this interlayer on the performance of anode as well as the cell was studied using various electrochemical techniques. The results show that addition of the SDC interlayer reduced the anodic over-potential significantly, however, the ohmic resistance of the cell with an SDC interlayer increased, which leaded to a decrease of the power output. The electrochemical oxidation of H2 on Ni-SDC anodes was controlled by two processes, which corresponded to two arcs in the impedance spectra. The high frequency arc decreased with the addition of SDC interlayer, and could correspond to the electrochemical reaction at three-phase-boundary (TPB) or the transfer of oxygen ions from LSGM to SDC. The low frequency arc showed no dependency on the addition of SDC, and could be related to the adsorption and diffusion of H2 at the surface of electrode. The cells with an SDC interlayer showed much better stability compared with the cell using single layer anode, and the performance of the cell with Ni-SDC/SDC (1573 K) anode was higher than the cell with a single layer Ni-SDC anode after long time running.
2003, 19(09): 854-857
doi: 10.3866/PKU.WHXB20030915
Abstract:
In MH/Ni battery, oxygen evolution causes a high inner pressure during charge and overcharge, and an inappropriate elimination of the oxygen in the battery results in accumulation of heat. This is the main obstacle in developing and applying high capability and high power battery. How to reduce the ratio of the chemical catalysis rate to the electric catalysis rate in MH/Ni battery is considered as an urgent question. In this paper, ring-metalated phthalocyanine compounds were chosen as an electrochemical catalyst. Batteries with or without of the electrochemical catalyst were prepared. The curves of their inner pressure, the capacity attenuation, the discharge voltage and capacity at high current were compared. Experimental results show that the performance of batteries was obviously improved by the addition of the electrochemical catalyst.
In MH/Ni battery, oxygen evolution causes a high inner pressure during charge and overcharge, and an inappropriate elimination of the oxygen in the battery results in accumulation of heat. This is the main obstacle in developing and applying high capability and high power battery. How to reduce the ratio of the chemical catalysis rate to the electric catalysis rate in MH/Ni battery is considered as an urgent question. In this paper, ring-metalated phthalocyanine compounds were chosen as an electrochemical catalyst. Batteries with or without of the electrochemical catalyst were prepared. The curves of their inner pressure, the capacity attenuation, the discharge voltage and capacity at high current were compared. Experimental results show that the performance of batteries was obviously improved by the addition of the electrochemical catalyst.
2003, 19(09): 858-863
doi: 10.3866/PKU.WHXB20030916
Abstract:
For stable excited states of some diatomic molecules, ωe has been known but not Re. The present paper provides an empirical formula relating ωe and Re, ωe=C, which is different from that give in Ref.[9] where α has been considered as a constant 2. Spectrum data of nearly 60 molecules have been simulated using this ωe～Re relation, the results show that the model is universal and reliable in use. At the same time, the first-excited states a 1Δfor NX(X=F, Cl, Br) molecules using the CIS/6-311＋g(3df)、MCSCF/6-311＋g(3df) and B3LYP/6-311＋g(3df) have been calculated. The analytical potential energy function has been also derived using ab initio calculation and spectrum parameters of experiment.
For stable excited states of some diatomic molecules, ωe has been known but not Re. The present paper provides an empirical formula relating ωe and Re, ωe=C, which is different from that give in Ref.[9] where α has been considered as a constant 2. Spectrum data of nearly 60 molecules have been simulated using this ωe～Re relation, the results show that the model is universal and reliable in use. At the same time, the first-excited states a 1Δfor NX(X=F, Cl, Br) molecules using the CIS/6-311＋g(3df)、MCSCF/6-311＋g(3df) and B3LYP/6-311＋g(3df) have been calculated. The analytical potential energy function has been also derived using ab initio calculation and spectrum parameters of experiment.
2003, 19(09): 864-866
doi: 10.3866/PKU.WHXB20030917
Abstract:
In this paper, under the catalytic effect of nickel particles supported on glass, self-aligned carbon nanotubes were synthesized by microwave plasma chemical vapor deposition under a mixture of methane and hydrogen gases at about 550 ℃.During the process of nanotubes growth, the total pressure in the chamber was kept at 3 kPa, the microwave plasma input power was 300 W, and the flow rates of H2 and CH4 were 50 and 1 standard cubic centimeter (sccm) per minute, respectively. It was found that the carbon nanotubes grew always perpendicular to the substrate surface under the effect of plasma. When the substrate was not contacted with plasma, only entangled carbon nanotubes grew on glass randomly. From the research results, we can demonstrate that the electrical self-bias imposed on the substrate is the primary mechanism responsible for the alignment of carbon nanotubes, and we can envision that this simple method can be of great importance for the fabrication of devices in the future.
In this paper, under the catalytic effect of nickel particles supported on glass, self-aligned carbon nanotubes were synthesized by microwave plasma chemical vapor deposition under a mixture of methane and hydrogen gases at about 550 ℃.During the process of nanotubes growth, the total pressure in the chamber was kept at 3 kPa, the microwave plasma input power was 300 W, and the flow rates of H2 and CH4 were 50 and 1 standard cubic centimeter (sccm) per minute, respectively. It was found that the carbon nanotubes grew always perpendicular to the substrate surface under the effect of plasma. When the substrate was not contacted with plasma, only entangled carbon nanotubes grew on glass randomly. From the research results, we can demonstrate that the electrical self-bias imposed on the substrate is the primary mechanism responsible for the alignment of carbon nanotubes, and we can envision that this simple method can be of great importance for the fabrication of devices in the future.
2003, 19(09): 867-870
doi: 10.3866/PKU.WHXB20030918
Abstract:
Standard thermodynamic functions of transfer of naphthalene from water to H2O-t-butyl alcohol (TBA) mixtures were determined from the solubility measurements at different temperatures. Standard free energies of transfer for naphthalene showed a complex decreasing tendency with the increasing of x(TBA), and the standard entropy and enthalpy of transfer exhibited a variation of double peak curves with x(TBA).This illustrated that the micro structures of series mixed solvents of H2O-TBA underwent a complicated process from relative order to relative disorder and then from relative disorder to relative order, and back to relative disorder again, then up to relative order. The results suggested that there was a relatively ordered structure near x(TBA)= 0.08 in H2O-TBA solutions besides the existence of a clathrate structure in the water-rich region.
Standard thermodynamic functions of transfer of naphthalene from water to H2O-t-butyl alcohol (TBA) mixtures were determined from the solubility measurements at different temperatures. Standard free energies of transfer for naphthalene showed a complex decreasing tendency with the increasing of x(TBA), and the standard entropy and enthalpy of transfer exhibited a variation of double peak curves with x(TBA).This illustrated that the micro structures of series mixed solvents of H2O-TBA underwent a complicated process from relative order to relative disorder and then from relative disorder to relative order, and back to relative disorder again, then up to relative order. The results suggested that there was a relatively ordered structure near x(TBA)= 0.08 in H2O-TBA solutions besides the existence of a clathrate structure in the water-rich region.
2003, 19(09): 871-874
doi: 10.3866/PKU.WHXB20030919
Abstract:
Optimized geometries of twenty three pyridylamine ligands for the nicotinic acetylcholine receptor are obtained by using simulated annealing method of molecular dynamics. Then these complexes are optimized by molecular mechanics and semi-empirical quantum mechanics method-AM1 and the electronic structures are calculated. The result reveals that the value of pKi has some relationship with the energy of lowest unoccupied molecular orbital, charge on the pyridyl group and molecular conformation.
Optimized geometries of twenty three pyridylamine ligands for the nicotinic acetylcholine receptor are obtained by using simulated annealing method of molecular dynamics. Then these complexes are optimized by molecular mechanics and semi-empirical quantum mechanics method-AM1 and the electronic structures are calculated. The result reveals that the value of pKi has some relationship with the energy of lowest unoccupied molecular orbital, charge on the pyridyl group and molecular conformation.
2003, 19(09): 875-878
doi: 10.3866/PKU.WHXB20030920
Abstract:
The ion spectrum of the O(3PJ″) from the photodissociation of NO2 at laser wavelength λ=355 nm (28 169 cm－1) has been investigated using resonance enhanced multiphoton ionization (REMPI) and time of light (TOF) mass spectrometer technique. The spin-orbit fine structure resolved ion spectrum of the atomic oxygen from the two-photon transition of O (2p 3PJ″→3p 3PJ’)is obtained. The ion signal intensity of oxygen as a function of the UV ionization laser energy (λ=226 nm) can be well simulated with cubic proportional curve. It shows, atomic oxygen O(3PJ″) is ionized by (2＋1) multiphoton absorption process. The obtained three spin-orbit sublevels branching rations of f1=I(3P1)/I(3P2) and f0=I(3P0)/I(3P2) for O(3PJ″=2, 1, 0) are 0.54±0.09 and 0.20±0.04 respectively which is in od agreement with the statistical distribution of 3P2∶3P1∶3P0=1∶0.6∶0.2 .In lower sample(NO2) pressure the collision-induced energy transfer between atomic oxygen sublevels O(3PJ″=2, 1, 0) can’t occur during photodissociation-ionization time (10－8 s).The population of spin-orbit angular momentum split sublevels O(3PJ″=2, 1, 0) is statistical distribution.
The ion spectrum of the O(3PJ″) from the photodissociation of NO2 at laser wavelength λ=355 nm (28 169 cm－1) has been investigated using resonance enhanced multiphoton ionization (REMPI) and time of light (TOF) mass spectrometer technique. The spin-orbit fine structure resolved ion spectrum of the atomic oxygen from the two-photon transition of O (2p 3PJ″→3p 3PJ’)is obtained. The ion signal intensity of oxygen as a function of the UV ionization laser energy (λ=226 nm) can be well simulated with cubic proportional curve. It shows, atomic oxygen O(3PJ″) is ionized by (2＋1) multiphoton absorption process. The obtained three spin-orbit sublevels branching rations of f1=I(3P1)/I(3P2) and f0=I(3P0)/I(3P2) for O(3PJ″=2, 1, 0) are 0.54±0.09 and 0.20±0.04 respectively which is in od agreement with the statistical distribution of 3P2∶3P1∶3P0=1∶0.6∶0.2 .In lower sample(NO2) pressure the collision-induced energy transfer between atomic oxygen sublevels O(3PJ″=2, 1, 0) can’t occur during photodissociation-ionization time (10－8 s).The population of spin-orbit angular momentum split sublevels O(3PJ″=2, 1, 0) is statistical distribution.
2003, 19(09): 879-882
doi: 10.3866/PKU.WHXB20030921
Abstract:
Authors report on the detection of DNA hybridization using electrochemistry method. The target ss-DNA was immobilized on glassy carbon electrode and hybridized with the ld nanoparticle-oli nucleotide DNA probe. A nanoparticle-promoted Ag precipitation was used to enlarge the nanoparticle tag, forming the Au/Ag core-shell structure, followed by the release of the silver metal atoms anchored on the hybrids by oxidative metal dissolution and the indirect determination of the solubilized Ag ions by anodic stripping voltammetry (ASV) at a carbon fiber microelectrode. Further signal amplification, and lowering of the detection limits to the picomolar domains, was achieved by precipitating silver. The results show that this method has od correlation for detection of DNA in the range of 100～1 000 pmol•L－1and allows detection at levels as low as 10 pmol•L－1 of the target oli nucleotides.
Authors report on the detection of DNA hybridization using electrochemistry method. The target ss-DNA was immobilized on glassy carbon electrode and hybridized with the ld nanoparticle-oli nucleotide DNA probe. A nanoparticle-promoted Ag precipitation was used to enlarge the nanoparticle tag, forming the Au/Ag core-shell structure, followed by the release of the silver metal atoms anchored on the hybrids by oxidative metal dissolution and the indirect determination of the solubilized Ag ions by anodic stripping voltammetry (ASV) at a carbon fiber microelectrode. Further signal amplification, and lowering of the detection limits to the picomolar domains, was achieved by precipitating silver. The results show that this method has od correlation for detection of DNA in the range of 100～1 000 pmol•L－1and allows detection at levels as low as 10 pmol•L－1 of the target oli nucleotides.
2003, 19(09): 883-885
doi: 10.3866/PKU.WHXB20030922
Abstract:
The heat capacities of the high efficient working fluid used for a heat pipe(Cp) were measured by a low temperature adiabatic calorimeter over the range from 78 to 320 K. No thermal anomaly was observed in the range from 78 to 245 K and 274 to 320 K. The functions of Cp vs T were established based on the measured heat capacity data by least-square fitting method to be Cp/(J•K－1•g－1)=0.5369T＋0.07279 in the range of 78.41～245.19 K. The freezing point, freezing enthalpy and freezing entropy of it were determined to be 271.21 K, 353.6 J•g－1 and 1.304 J•K－1•g－1, respectively. The heat capacities of it are near a constant to be Cp/(J•K－1•g－1)=3.403±0.020 in the range 274 K≤T≤320 K. According to the relationship of thermodynamic functions, the thermodynamic function values of the working fluid were calculated in the temperature range of 280～320 K with 5 K intervals.
The heat capacities of the high efficient working fluid used for a heat pipe(Cp) were measured by a low temperature adiabatic calorimeter over the range from 78 to 320 K. No thermal anomaly was observed in the range from 78 to 245 K and 274 to 320 K. The functions of Cp vs T were established based on the measured heat capacity data by least-square fitting method to be Cp/(J•K－1•g－1)=0.5369T＋0.07279 in the range of 78.41～245.19 K. The freezing point, freezing enthalpy and freezing entropy of it were determined to be 271.21 K, 353.6 J•g－1 and 1.304 J•K－1•g－1, respectively. The heat capacities of it are near a constant to be Cp/(J•K－1•g－1)=3.403±0.020 in the range 274 K≤T≤320 K. According to the relationship of thermodynamic functions, the thermodynamic function values of the working fluid were calculated in the temperature range of 280～320 K with 5 K intervals.
2003, 19(09): 886-888
doi: 10.3866/PKU.WHXB20030923
Abstract:
A 3D database searching was conducted with 3DFS in 3D database using the pharmacophore of epidermal growth factor receptor(EGFR) tyrosine kinase inhibitors. Twelve compounds were selected from the hits and their biological activities were predicted using the Flexible Atom Receptor Model (FLARM) method. Two compounds among them were found to have high activities according to the prediction results. So these two compounds may have the inhibition function and structure optimization can be done with these two lead compounds.
A 3D database searching was conducted with 3DFS in 3D database using the pharmacophore of epidermal growth factor receptor(EGFR) tyrosine kinase inhibitors. Twelve compounds were selected from the hits and their biological activities were predicted using the Flexible Atom Receptor Model (FLARM) method. Two compounds among them were found to have high activities according to the prediction results. So these two compounds may have the inhibition function and structure optimization can be done with these two lead compounds.
