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2006 Volume 22 Issue 3
2006, 22(03): 261-264
doi: 10.3866/PKU.WHXB20060301
Abstract:
Polypyrrole (PPy) nano-fiber array electrodes were fabricated by electrochemical deposition of PPy in the pores of anodic aluminium oxide (AAO) templates. The photocurrent appeared at the potential below －0.1 V (vs Ag/AgCl) was caused by the p-type semiconductor properties of PPy material. Its flat-band potential Efb was determined as －0.217 V (vs Ag/AgCl). The photocurrent of PPy nano-fiber array electrode varied with the length of the PPy nanofibers. For very thin PPy nano-fiber array the photocurrent was small. But if the arrays were too thick the photocurrent was also small because the photo-induced electrons might recombine with photo-induced holes in the film before reaching the back contact. The optimum thickness was 42 nm. The PPy nano-fiber devices might be used as nano photo-electronic device in the future.
Polypyrrole (PPy) nano-fiber array electrodes were fabricated by electrochemical deposition of PPy in the pores of anodic aluminium oxide (AAO) templates. The photocurrent appeared at the potential below －0.1 V (vs Ag/AgCl) was caused by the p-type semiconductor properties of PPy material. Its flat-band potential Efb was determined as －0.217 V (vs Ag/AgCl). The photocurrent of PPy nano-fiber array electrode varied with the length of the PPy nanofibers. For very thin PPy nano-fiber array the photocurrent was small. But if the arrays were too thick the photocurrent was also small because the photo-induced electrons might recombine with photo-induced holes in the film before reaching the back contact. The optimum thickness was 42 nm. The PPy nano-fiber devices might be used as nano photo-electronic device in the future.
2006, 22(03): 265-269
doi: 10.3866/PKU.WHXB20060302
Abstract:
The reaction of Au+(1S, 3D) ions with N2O(1Σ+) are studied by means of B3LYP/6-311+G*(the basis set of Au+ is(8s7p6d)/[6s5p3d]). The structures of all reactants, products, complexes, and transition structure have been optimized and characterized at the fundamental singlet and excited triplet electronic states. The calculated results show that two main reaction pathways [ Au+(1S) + N2O(1Σ+)→1NA-Complex-1→1NA-TS1→1NA-Complex-2→ 1NA-Crossing→[3OAuNN]+ and Au+(1S) + N2O(1Σ+) →1NB-Complex →1NB-Crossing →[AuNN(1Σ+)]+ + O(3P)] must proceed through a crossing point of the singlet and triplet surfaces and appear as “intersystem crossing”. Crossing points are located by means of the intrinsic reaction coordinate single point vertical excited approach. The mechanisms of spin inversion are discussed.
The reaction of Au+(1S, 3D) ions with N2O(1Σ+) are studied by means of B3LYP/6-311+G*(the basis set of Au+ is(8s7p6d)/[6s5p3d]). The structures of all reactants, products, complexes, and transition structure have been optimized and characterized at the fundamental singlet and excited triplet electronic states. The calculated results show that two main reaction pathways [ Au+(1S) + N2O(1Σ+)→1NA-Complex-1→1NA-TS1→1NA-Complex-2→ 1NA-Crossing→[3OAuNN]+ and Au+(1S) + N2O(1Σ+) →1NB-Complex →1NB-Crossing →[AuNN(1Σ+)]+ + O(3P)] must proceed through a crossing point of the singlet and triplet surfaces and appear as “intersystem crossing”. Crossing points are located by means of the intrinsic reaction coordinate single point vertical excited approach. The mechanisms of spin inversion are discussed.
2006, 22(03): 270-274
doi: 10.1016/S1872-1508(06)60001-6
Abstract:
Molecular dynamic (MD) quench method and grand canonical Monte Carlo method (GCMC) are used to study the adsorption of water on NanZSM-5 type zeolite. The simulated adsorption isotherm is in od agreement with the experimental data reported in literatures. Based on these facts, adsorption of water on NanZSM-5 with various nSi/nAl ratios is predicted. The simulation results indicate that nSi/nAl ratio of zeolite framework affects the water adsorption and adsorption isotherms greatly and the adsorption amount decreases as the nSi/nAl ratio increases, which can be explained by that the atomic charge of Na+ cation would influence greatly the polar water molecules due to the Coulomb force. The adsorbed water molecules are located around Na cations and Al atoms on the zeolite framework and the average number around Na cation and Al atom is four at lower loading. However, there are hydrogen bonds between the dsorbed water molecules and the oxygen atoms on the zeolite frameworks at higher loading. At the same loading, the isosteric heat decreases as the nSi/nAl ratio increases.
Molecular dynamic (MD) quench method and grand canonical Monte Carlo method (GCMC) are used to study the adsorption of water on NanZSM-5 type zeolite. The simulated adsorption isotherm is in od agreement with the experimental data reported in literatures. Based on these facts, adsorption of water on NanZSM-5 with various nSi/nAl ratios is predicted. The simulation results indicate that nSi/nAl ratio of zeolite framework affects the water adsorption and adsorption isotherms greatly and the adsorption amount decreases as the nSi/nAl ratio increases, which can be explained by that the atomic charge of Na+ cation would influence greatly the polar water molecules due to the Coulomb force. The adsorbed water molecules are located around Na cations and Al atoms on the zeolite framework and the average number around Na cation and Al atom is four at lower loading. However, there are hydrogen bonds between the dsorbed water molecules and the oxygen atoms on the zeolite frameworks at higher loading. At the same loading, the isosteric heat decreases as the nSi/nAl ratio increases.
2006, 22(03): 275-279
doi: 10.1016/S1872-1508(06)60002-8
Abstract:
The reactions of active nitrogen with SO2 and SOCl2 have been studied on a flowing afterglow apparatus. The emissions ranging from 280 to 500 nm were assigned to SO2 (~A2, 1B1→1A1) and SO2(3B1→1A1). With the aim to discerning the roles of active N atom and N2(A3Σ+u) played in the reactions above, N2(A3Σ+u) generated by Ar(3P0, 2) reacting with N2 has substituted the active nitrogen to react with SO2 and SOCl2, respectively. It shows that when reacting with SO2, both the active nitrogen and N2(A3Σ+u) without N atom can produce SO2 (~A2, 1B1) and SO2 (3B1); while reacting with SOCl2, only when N2(A3Σ+u) and the active N atoms coexist, could SO2 (3B1) be formed. Therefore, it is concluded that N2 (A3Σ+u) dominates the reaction of active nitrogen with SO2 and makes SO2 excited directly; N2 (A3Σ+u)and active N atom reacting with SOCl2 can generate the constitutions to form SO2 (3B1), which were suggested as N2O(X1Σ+) and SO(X).
The reactions of active nitrogen with SO2 and SOCl2 have been studied on a flowing afterglow apparatus. The emissions ranging from 280 to 500 nm were assigned to SO2 (~A2, 1B1→1A1) and SO2(3B1→1A1). With the aim to discerning the roles of active N atom and N2(A3Σ+u) played in the reactions above, N2(A3Σ+u) generated by Ar(3P0, 2) reacting with N2 has substituted the active nitrogen to react with SO2 and SOCl2, respectively. It shows that when reacting with SO2, both the active nitrogen and N2(A3Σ+u) without N atom can produce SO2 (~A2, 1B1) and SO2 (3B1); while reacting with SOCl2, only when N2(A3Σ+u) and the active N atoms coexist, could SO2 (3B1) be formed. Therefore, it is concluded that N2 (A3Σ+u) dominates the reaction of active nitrogen with SO2 and makes SO2 excited directly; N2 (A3Σ+u)and active N atom reacting with SOCl2 can generate the constitutions to form SO2 (3B1), which were suggested as N2O(X1Σ+) and SO(X).
2006, 22(03): 280-285
doi: 10.1016/S1872-1508(06)60003-X
Abstract:
A series of new light rare earth complexes of RE(C10H9N2O4)(C10H8N2O4)•nH2O (RE = La, Ce, Pr, Nd, Sm, Eu, Gd) have been synthesized. The composition of the complexes is determined by elemental analysis, IR, UV, fluorescence and XRD. The enthalpies of dissolution for the complexes in DMF were measured and it was found that the correlation of the enthalpies of dissolution for the complexes and atomic number was not monotonic. The enthalpy of dissolution curves of the light rare earth complexes are regarded as the front two groups of “quadripartite effect”.
A series of new light rare earth complexes of RE(C10H9N2O4)(C10H8N2O4)•nH2O (RE = La, Ce, Pr, Nd, Sm, Eu, Gd) have been synthesized. The composition of the complexes is determined by elemental analysis, IR, UV, fluorescence and XRD. The enthalpies of dissolution for the complexes in DMF were measured and it was found that the correlation of the enthalpies of dissolution for the complexes and atomic number was not monotonic. The enthalpy of dissolution curves of the light rare earth complexes are regarded as the front two groups of “quadripartite effect”.
2006, 22(03): 286-290
doi: 10.3866/PKU.WHXB20060306
Abstract:
CaSiO3∶Pb, Mn phosphor particles with red-luminescence were prepared by aqueous co-deposition reaction. Surface modification of CaSiO3∶Pb, Mn phosphors was carried out by coating transparent conductive films of Al-doped zinc oxide which were formed by homogeneous phase co-precipitation and heat treatment process. The coated phosphors were characterized by X-ray diffraction (XRD), photoluminescence (PL), transmittance electron microscopy (TEM) and conductance measurements. The results showed that the conductivity of ZnO∶Al-coated phosphors, n(Zn)/n(Ca)=10%, n(Al)/n(Zn)=5%, had been improved obviously while the corresponding photoluminescence intensity remained the same as the as-prepared phosphors. For lowering the resistivity of phosphors, experimental conditions have been optimized, which include hydrolyzing at 75 ℃ for 1.5 h, heat treatment at 500 ℃ for 45 min, respectively.
CaSiO3∶Pb, Mn phosphor particles with red-luminescence were prepared by aqueous co-deposition reaction. Surface modification of CaSiO3∶Pb, Mn phosphors was carried out by coating transparent conductive films of Al-doped zinc oxide which were formed by homogeneous phase co-precipitation and heat treatment process. The coated phosphors were characterized by X-ray diffraction (XRD), photoluminescence (PL), transmittance electron microscopy (TEM) and conductance measurements. The results showed that the conductivity of ZnO∶Al-coated phosphors, n(Zn)/n(Ca)=10%, n(Al)/n(Zn)=5%, had been improved obviously while the corresponding photoluminescence intensity remained the same as the as-prepared phosphors. For lowering the resistivity of phosphors, experimental conditions have been optimized, which include hydrolyzing at 75 ℃ for 1.5 h, heat treatment at 500 ℃ for 45 min, respectively.
2006, 22(03): 291-295
doi: 10.1016/S1872-1508(06)60004-1
Abstract:
The electrooxidation behavior of formic acid on Pt-Ru/GC electrode was investigated by CV, multi-potential steps and SERS. It was found that formic acid could dissociate spontaneously on Pt-Ru/GC electrode as it dissociated on rough Pt electrode, produce strong absorption intermediate CO and reactive intermediate —COO－. The results demonstrated that Ru could improve the electrocatalytic activity of formic acid on Pt-Ru/GC electrode. As the ratio of Pt and Ru in desposition solution changed from 10∶1 to 1∶1, the oxidation potential of CO shifted negatively about 60 mV(from 0.41 V to 0.35 V). Compared to rough Pt electrode, the oxidation potential of CO on Pt-Ru/GC(1∶1) shifted negatively 200 mV. These results indicate that SERS is hopeful to be a comprehensive spectroscopy tool of investigating the electrocatalytic reaction mechanism.
The electrooxidation behavior of formic acid on Pt-Ru/GC electrode was investigated by CV, multi-potential steps and SERS. It was found that formic acid could dissociate spontaneously on Pt-Ru/GC electrode as it dissociated on rough Pt electrode, produce strong absorption intermediate CO and reactive intermediate —COO－. The results demonstrated that Ru could improve the electrocatalytic activity of formic acid on Pt-Ru/GC electrode. As the ratio of Pt and Ru in desposition solution changed from 10∶1 to 1∶1, the oxidation potential of CO shifted negatively about 60 mV(from 0.41 V to 0.35 V). Compared to rough Pt electrode, the oxidation potential of CO on Pt-Ru/GC(1∶1) shifted negatively 200 mV. These results indicate that SERS is hopeful to be a comprehensive spectroscopy tool of investigating the electrocatalytic reaction mechanism.
2006, 22(03): 296-300
doi: 10.3866/PKU.WHXB20060308
Abstract:
Carbon nanotubes (CNTs), with well defined one-dimension nanoscale tubular structure, have potential applications for elctromagnetic wave absorption. The complex permittivity and permeability spectra of different kinds of CNTs were measured in the range from 2 GHz to 18 GHz. The coefficient of attenuation, impedance and loss tangents of different kinds of carbon nanotube composites were compared. The order of loss tangents is as follows: aligned multi-walled CNTs > raw tangled multi-walled CNTs > purified tangled multi-walled CNTs > raw tangled single-walled CNTs > purified tangled single-walled CNTs. The reflectivities of different kinds of carbon nanotube composites were calculated. Compared with multi-walled CNTs, single-walled CNTs have wider absorption capability. Both experimental and calculated results indicated that CNTs as filler in nano-composite materials have excellent elctromagenetic wave absorption properties.
Carbon nanotubes (CNTs), with well defined one-dimension nanoscale tubular structure, have potential applications for elctromagnetic wave absorption. The complex permittivity and permeability spectra of different kinds of CNTs were measured in the range from 2 GHz to 18 GHz. The coefficient of attenuation, impedance and loss tangents of different kinds of carbon nanotube composites were compared. The order of loss tangents is as follows: aligned multi-walled CNTs > raw tangled multi-walled CNTs > purified tangled multi-walled CNTs > raw tangled single-walled CNTs > purified tangled single-walled CNTs. The reflectivities of different kinds of carbon nanotube composites were calculated. Compared with multi-walled CNTs, single-walled CNTs have wider absorption capability. Both experimental and calculated results indicated that CNTs as filler in nano-composite materials have excellent elctromagenetic wave absorption properties.
2006, 22(03): 301-305
doi: 10.1016/S1872-1508(06)60005-3
Abstract:
The effects of partial substitution of Pd for Mg on the corrosion behaviors of Mg0.9－xTi0.1PdxNi(x=0.04～0.1)hydrogen storage alloys were studied in this paper. The alloys were prepared by mechanical alloying. The alloy structures became amorphous after ball milling 120 h, which was confirmed by XRD and TEM analyses. The cyclic charge-discharge tests showed that the Pd addition prolonged the cycle life of the alloys effectively. The corrosion performances of the alloys were investigated by open circuit potential measurements, anodic polarization, electrochemical impedance spectroscopy, and XPS experiments. The increase of Pd content shifted the alloy corrosion potentials towards more positive values. The initial corrosion currents of the alloys and its increment rates along with cycle number decreased with the increase of Pd content in the alloys. The measured electrochemical impedance spectra were fitted well with the proposed equivalent circuit model. The analyses suggested that the thickness and the resistance of passive film on the surface of alloys increased with the increase of Pd content in the alloys. The results of XPS experiments demonstrated that the addition of Pd in the alloys suppressed the oxidation and enhanced the anti-corrosion capabilities of the alloys. When the Pd content reached 0.1, the corrosion resistant performances of Mg0.9－xTi0.1PdxNi(x=0.04～0.1) alloys are the best and the discharge capacity retention rate is the highest.
The effects of partial substitution of Pd for Mg on the corrosion behaviors of Mg0.9－xTi0.1PdxNi(x=0.04～0.1)hydrogen storage alloys were studied in this paper. The alloys were prepared by mechanical alloying. The alloy structures became amorphous after ball milling 120 h, which was confirmed by XRD and TEM analyses. The cyclic charge-discharge tests showed that the Pd addition prolonged the cycle life of the alloys effectively. The corrosion performances of the alloys were investigated by open circuit potential measurements, anodic polarization, electrochemical impedance spectroscopy, and XPS experiments. The increase of Pd content shifted the alloy corrosion potentials towards more positive values. The initial corrosion currents of the alloys and its increment rates along with cycle number decreased with the increase of Pd content in the alloys. The measured electrochemical impedance spectra were fitted well with the proposed equivalent circuit model. The analyses suggested that the thickness and the resistance of passive film on the surface of alloys increased with the increase of Pd content in the alloys. The results of XPS experiments demonstrated that the addition of Pd in the alloys suppressed the oxidation and enhanced the anti-corrosion capabilities of the alloys. When the Pd content reached 0.1, the corrosion resistant performances of Mg0.9－xTi0.1PdxNi(x=0.04～0.1) alloys are the best and the discharge capacity retention rate is the highest.
2006, 22(03): 306-311
doi: 10.1016/S1872-1508(06)60006-5
Abstract:
Electrocatalytic reductive dechlorination of 2,4,5-PCB(PCB: polychlorinated biphenyls) in aqueous solution containing methanol and hexadecyltrimethyl ammonium bromide (CTAB) was studied in a Teflon-made two-compartment flow-through cell with a palladium-loaded permeable titanium mini mesh cathode and a platinum foil anode. The experiments were carried out to explore the effects of palladium loading, electrode structure, applied cathode potential and catholyte flow rate on dechlorination. The results indicated that the optimal conditions were 3 mg Pd loading /cm2 geometric area, three-layer cathode and －1.10 V (vs SCE) controlled potential. After 9 h electrocatalytic reduction under the optimal conditions, the dechlorination rate of 2,4,5-PCB reached 96.2%, but the conversion rate to biphenyl was 89.6%. The current efficiency changed between 11.3% and 33.0% during the electrocatalytic reduction.
Electrocatalytic reductive dechlorination of 2,4,5-PCB(PCB: polychlorinated biphenyls) in aqueous solution containing methanol and hexadecyltrimethyl ammonium bromide (CTAB) was studied in a Teflon-made two-compartment flow-through cell with a palladium-loaded permeable titanium mini mesh cathode and a platinum foil anode. The experiments were carried out to explore the effects of palladium loading, electrode structure, applied cathode potential and catholyte flow rate on dechlorination. The results indicated that the optimal conditions were 3 mg Pd loading /cm2 geometric area, three-layer cathode and －1.10 V (vs SCE) controlled potential. After 9 h electrocatalytic reduction under the optimal conditions, the dechlorination rate of 2,4,5-PCB reached 96.2%, but the conversion rate to biphenyl was 89.6%. The current efficiency changed between 11.3% and 33.0% during the electrocatalytic reduction.
2006, 22(03): 312-315
doi: 10.3866/PKU.WHXB20060311
Abstract:
The cooperative effects of alkaline earth metal ions and EDTA(ethylenediamine tetraacetic acid) on the corrosion inhibition of pure aluminum in 4 mol•L-1 KOH solution were investigated by hydrogen collection, polarization curve and electrochemical impedance spectroscopy(EIS). It was found that aluminum exhibits minimum corrosion rate in 4 mol•L-1 KOH solution containing 0.02 mol•L-1 EDTA, saturated Ca(OH)2 and saturated Sr(OH)2. EDAX analysis showed that alkaline earth metal ions and EDTA have no contribution to the formation of the surface film on aluminum. Therefore the inhibition effect may be caused by the adsorption of the inhibitor on aluminum surface. This fact indicates that these two ions act as interface inhibitors rather than inter-phase ones.
The cooperative effects of alkaline earth metal ions and EDTA(ethylenediamine tetraacetic acid) on the corrosion inhibition of pure aluminum in 4 mol•L-1 KOH solution were investigated by hydrogen collection, polarization curve and electrochemical impedance spectroscopy(EIS). It was found that aluminum exhibits minimum corrosion rate in 4 mol•L-1 KOH solution containing 0.02 mol•L-1 EDTA, saturated Ca(OH)2 and saturated Sr(OH)2. EDAX analysis showed that alkaline earth metal ions and EDTA have no contribution to the formation of the surface film on aluminum. Therefore the inhibition effect may be caused by the adsorption of the inhibitor on aluminum surface. This fact indicates that these two ions act as interface inhibitors rather than inter-phase ones.
2006, 22(03): 316-321
doi: 10.3866/PKU.WHXB20060312
Abstract:
Aligned carbon nanotube/carbon (ACNT/C) nanocomposites were fabricated by traditional chemical vapor infiltration (CVI) technology. The oxidation properties and mechanism of ACNT/C nanocomposites were investigated through SEM, Raman, thermogravimetric analysis (TGA) and static isothermal oxidation. TGA result shows that weight loss temperature of ACNT/C nanocomposites (0.80 g•cm-3) is about 720 ℃, which is 50 ℃ higher than weight loss temperature of carbon/carbon(C/C) composites (1.5 g•cm-3) prepared in the same process. Static isothermal oxidation results further demonstrate that chemical reaction speed of ACNT/C nanocomposites is lower than that of C/C composites obviously in air oxidation process at 550 ℃. SEM micrographs prove that ACNT/C nanocomposites still keep tubular structure in the oxidation process, and the oxidation reaction proceeds from outer layer to inner layer along the radial direction. ACNT/C nanocomposites exhibit od oxidation properties due to stable interface and higher graphitization level. The oxidation mechanism of the nanocomposites is discussed.
Aligned carbon nanotube/carbon (ACNT/C) nanocomposites were fabricated by traditional chemical vapor infiltration (CVI) technology. The oxidation properties and mechanism of ACNT/C nanocomposites were investigated through SEM, Raman, thermogravimetric analysis (TGA) and static isothermal oxidation. TGA result shows that weight loss temperature of ACNT/C nanocomposites (0.80 g•cm-3) is about 720 ℃, which is 50 ℃ higher than weight loss temperature of carbon/carbon(C/C) composites (1.5 g•cm-3) prepared in the same process. Static isothermal oxidation results further demonstrate that chemical reaction speed of ACNT/C nanocomposites is lower than that of C/C composites obviously in air oxidation process at 550 ℃. SEM micrographs prove that ACNT/C nanocomposites still keep tubular structure in the oxidation process, and the oxidation reaction proceeds from outer layer to inner layer along the radial direction. ACNT/C nanocomposites exhibit od oxidation properties due to stable interface and higher graphitization level. The oxidation mechanism of the nanocomposites is discussed.
2006, 22(03): 322-325
doi: 10.1016/S1872-1508(06)60007-7
Abstract:
The critical reverse micelle concentrations of quaternary ammonium Gemini surfactants C12-s-C12•2Br (s=2, 3, 4, 5, 6, 8, 12) in n-heptane (cmcw) have been determined by water solubilization method. These values are smaller than the critical micelle concentration (cmcaq) of them in aqueous solution, where C12-s-C12•2Br forms normal micelles. The cmcw as a function of s es through a maximum at s=4, which is similar to the variation regularity of cmcaq with s. The saturation amounts of water solubilized in the reverse micelles measured by both water solubilization method and conductivity method show a maximum at about s=5. This is attributed to the change of folded conformation of the spacer chain.
The critical reverse micelle concentrations of quaternary ammonium Gemini surfactants C12-s-C12•2Br (s=2, 3, 4, 5, 6, 8, 12) in n-heptane (cmcw) have been determined by water solubilization method. These values are smaller than the critical micelle concentration (cmcaq) of them in aqueous solution, where C12-s-C12•2Br forms normal micelles. The cmcw as a function of s es through a maximum at s=4, which is similar to the variation regularity of cmcaq with s. The saturation amounts of water solubilized in the reverse micelles measured by both water solubilization method and conductivity method show a maximum at about s=5. This is attributed to the change of folded conformation of the spacer chain.
2006, 22(03): 326-329
doi: 10.1016/S1872-1508(06)60008-9
Abstract:
The fluorescence quenching and the fluorescence decay of a series of dendritic bis-(8-hydroxyquinoline) derivatives (Gn-QMQ, n=1~3) were studied. The quenching rate constant decreased and fluorescence lifetime increased with the generation n increase, which resulted from an increased site-isolating effect of the dendritic structure on the core. Photophysical studies in different solvents indicated that there was an enhanced site-isolating effect in CH3CN.
The fluorescence quenching and the fluorescence decay of a series of dendritic bis-(8-hydroxyquinoline) derivatives (Gn-QMQ, n=1~3) were studied. The quenching rate constant decreased and fluorescence lifetime increased with the generation n increase, which resulted from an increased site-isolating effect of the dendritic structure on the core. Photophysical studies in different solvents indicated that there was an enhanced site-isolating effect in CH3CN.
2006, 22(03): 330-334
doi: 10.3866/PKU.WHXB20060315
Abstract:
By changing the sputtering conditions, Fe∶NiOx films with different catalytic behaviors were fabricated. With the increase of working pressure the overpotential in 100 mA•cm-2 changed from 780 mV at 1.0 Pa to 330 mV at 4.0 Pa. At the same time the Tafel slop also decreased dramatically from 71 mV•dec-1 to 53 mV•dec-1. Then by further analysis of EDX, XRD, XPS, SEM, we found that the crystallinity and the effective reactive surface area, especially the content of Ni3+, all can affect the catalytic properties. Lastly, we studied the transmittance of Fe:NiOx film in the range of visible light. But as the anode catalytic film, the transmittance of Fe:NiOx film is poor, especially with the increase of depth.
By changing the sputtering conditions, Fe∶NiOx films with different catalytic behaviors were fabricated. With the increase of working pressure the overpotential in 100 mA•cm-2 changed from 780 mV at 1.0 Pa to 330 mV at 4.0 Pa. At the same time the Tafel slop also decreased dramatically from 71 mV•dec-1 to 53 mV•dec-1. Then by further analysis of EDX, XRD, XPS, SEM, we found that the crystallinity and the effective reactive surface area, especially the content of Ni3+, all can affect the catalytic properties. Lastly, we studied the transmittance of Fe:NiOx film in the range of visible light. But as the anode catalytic film, the transmittance of Fe:NiOx film is poor, especially with the increase of depth.
2006, 22(03): 335-340
doi: 10.1016/S1872-1508(06)60009-0
Abstract:
Effect of butyl sultone (BS) on the graphite interface of lithium ion battery in carbonate-based electrolytes is studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), as well as the density functional theory (DFT) calculation. The results indicate that BS has lower LUMO energy than the solvents and is reduced prior to solvent compositions of the electrolyte on graphite electrode, forming a stable solid electrolyte interface (SEI) film during the first cycle. The SEI film resistance and the charge transfer resistance of graphite electrode in BS containing solution change little after storage at 70 ℃ for 24 h, while those in BS-free solution increase significantly. The influence of BS on the electrochemical performance was also discussed. It was found that the discharge capacities at room temperature, low temperature and after high temperature storage were significantly improved due to the presence of BS.
Effect of butyl sultone (BS) on the graphite interface of lithium ion battery in carbonate-based electrolytes is studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), as well as the density functional theory (DFT) calculation. The results indicate that BS has lower LUMO energy than the solvents and is reduced prior to solvent compositions of the electrolyte on graphite electrode, forming a stable solid electrolyte interface (SEI) film during the first cycle. The SEI film resistance and the charge transfer resistance of graphite electrode in BS containing solution change little after storage at 70 ℃ for 24 h, while those in BS-free solution increase significantly. The influence of BS on the electrochemical performance was also discussed. It was found that the discharge capacities at room temperature, low temperature and after high temperature storage were significantly improved due to the presence of BS.
2006, 22(03): 341-344
doi: 10.3866/PKU.WHXB20060317
Abstract:
An electrochemical method to remove barrier of porous anodic alumina (PAA) is presented. The barrier of PAA was dissolved by electrolysis in a three-electrode cell with PAA as cathode, Pt as anode and Ag/AgCl as reference electrode in neutral potassium chloride solution. The effects of time, temperature and potential on removal of barrier were investigated. The surface morphologies of the PAA before and after removal of barrier were characterized by SEM. Prussian blue (PB) modified electrode was prepared by a simple electroless deposition in PAA. The electrochemical activity of the Prussian blue modified PAA electrode was investigated by cyclic voltammetry. The results showed that the cyclic voltammogram of PAA exhibited an anodic peak at －0.4 V (vs Ag/AgCl) after electrolyzed for a period of time. The Prussian blue modified PAA electrode exhibited two reversible redox couples resulting from Fe3+/Fe2+ and [Fe(CN)6]3－/[Fe(CN)6]4－ transitions in the film. With temperature rising and potential lowering, the speed to produce alkali in PAA rose and the time required to dissolve barrier reduced. At the same time, higher temperature and lower potential could also cause local excess erosion of template. The proper temperature was below 15 ℃. After electrolyzed for 900 s at －1.8 V(vs Ag/AgCl) and 5 ℃, the barrier of PAA could be removed without broadening diameter of pore. Electrochemical method can remove barrier of PAA easily by controlling proper potential, temperature and time.
An electrochemical method to remove barrier of porous anodic alumina (PAA) is presented. The barrier of PAA was dissolved by electrolysis in a three-electrode cell with PAA as cathode, Pt as anode and Ag/AgCl as reference electrode in neutral potassium chloride solution. The effects of time, temperature and potential on removal of barrier were investigated. The surface morphologies of the PAA before and after removal of barrier were characterized by SEM. Prussian blue (PB) modified electrode was prepared by a simple electroless deposition in PAA. The electrochemical activity of the Prussian blue modified PAA electrode was investigated by cyclic voltammetry. The results showed that the cyclic voltammogram of PAA exhibited an anodic peak at －0.4 V (vs Ag/AgCl) after electrolyzed for a period of time. The Prussian blue modified PAA electrode exhibited two reversible redox couples resulting from Fe3+/Fe2+ and [Fe(CN)6]3－/[Fe(CN)6]4－ transitions in the film. With temperature rising and potential lowering, the speed to produce alkali in PAA rose and the time required to dissolve barrier reduced. At the same time, higher temperature and lower potential could also cause local excess erosion of template. The proper temperature was below 15 ℃. After electrolyzed for 900 s at －1.8 V(vs Ag/AgCl) and 5 ℃, the barrier of PAA could be removed without broadening diameter of pore. Electrochemical method can remove barrier of PAA easily by controlling proper potential, temperature and time.
2006, 22(03): 345-349
doi: 10.3866/PKU.WHXB20060318
Abstract:
Textural and structure characterizations of Ce1－xMnxO2 (0≤x≤1) samples were studied by N2 adsorption/desorption, XRD and Raman spectroscopy. The N2 adsorption/desorption isotherms are found to be IV-type according to BDDT and their related hysteresis loops are H1 type. Pore size distribution of the Ce1－xMnxO2 samples is in the mesopores range with Rp (max) between 2.5 nm and 3.7 nm. Particle sizes of the samples with both high Mn (x>0.7) and low Mn (x<0.3) contents are larger than those with 0.3≤x≤0.7. Raman spectroscopic results show that the Ce1－xMnxO2 (x≠0, 1) samples contain mixed phases of α-Mn2O3 and Ce-Mn-O solid solution, although the presence of α-Mn2O3 phase is not detected in the XRD measurement of the samples with x≤0.7, suggesting that Raman spectroscopy is more sensitive in the structural characterization of Ce1－xMnxO2 samples.
Textural and structure characterizations of Ce1－xMnxO2 (0≤x≤1) samples were studied by N2 adsorption/desorption, XRD and Raman spectroscopy. The N2 adsorption/desorption isotherms are found to be IV-type according to BDDT and their related hysteresis loops are H1 type. Pore size distribution of the Ce1－xMnxO2 samples is in the mesopores range with Rp (max) between 2.5 nm and 3.7 nm. Particle sizes of the samples with both high Mn (x>0.7) and low Mn (x<0.3) contents are larger than those with 0.3≤x≤0.7. Raman spectroscopic results show that the Ce1－xMnxO2 (x≠0, 1) samples contain mixed phases of α-Mn2O3 and Ce-Mn-O solid solution, although the presence of α-Mn2O3 phase is not detected in the XRD measurement of the samples with x≤0.7, suggesting that Raman spectroscopy is more sensitive in the structural characterization of Ce1－xMnxO2 samples.
2006, 22(03): 350-354
doi: 10.3866/PKU.WHXB20060319
Abstract:
Linear and zigzag micro-beads were arranged by means of micro-molding in capillary (MIMIC), the mechanism of self-assembling in MIMIC was primarily studied. Annular micro-beads or semi-annual micro-beads with different numbers of microsphere were arranged through the template of the micro-droplet. When heated up to the softening temperature of polystyrene(PS) microspheres, the microspheres were joint up together. After the aluminum thin film on the substrate was dissolved, the stand-free micro-beads would be obtained. In the further study, the way linking the microsphere will be improved, so that the flexibly stand-free micro-beads can be obatined. The micro-beads can be used as a simple and direct “model” of macromolecular chain. It is hopeful to simulate condensed process of real macromolecules in a mesoscopic scale.
Linear and zigzag micro-beads were arranged by means of micro-molding in capillary (MIMIC), the mechanism of self-assembling in MIMIC was primarily studied. Annular micro-beads or semi-annual micro-beads with different numbers of microsphere were arranged through the template of the micro-droplet. When heated up to the softening temperature of polystyrene(PS) microspheres, the microspheres were joint up together. After the aluminum thin film on the substrate was dissolved, the stand-free micro-beads would be obtained. In the further study, the way linking the microsphere will be improved, so that the flexibly stand-free micro-beads can be obatined. The micro-beads can be used as a simple and direct “model” of macromolecular chain. It is hopeful to simulate condensed process of real macromolecules in a mesoscopic scale.
2006, 22(03): 355-358
doi: 10.3866/PKU.WHXB20060320
Abstract:
The lattice density functional theory (LDFT) for a Gibbs ensemble system of monoatomic molecules adsorbed in finite-width slits was modified by introducing the intermolecular-action-pair′s correction factor. The adsorption and desorption isotherms of solute were then calculated by a successive iteration procedure. The micro mechanisms of hysteresis loops are discussed by both the revised and original LDFT model. It is found that they can both predict hysteresis loops but large differences are found between results of them. As Monte Carlo simulation has demonstrated that revised model is more suitable to predict adsorbing properties in slits according to our former works, it can be concluded that the original LDFT model may arouse obvious system errors for its simple mean field assumption in theory treatments.
The lattice density functional theory (LDFT) for a Gibbs ensemble system of monoatomic molecules adsorbed in finite-width slits was modified by introducing the intermolecular-action-pair′s correction factor. The adsorption and desorption isotherms of solute were then calculated by a successive iteration procedure. The micro mechanisms of hysteresis loops are discussed by both the revised and original LDFT model. It is found that they can both predict hysteresis loops but large differences are found between results of them. As Monte Carlo simulation has demonstrated that revised model is more suitable to predict adsorbing properties in slits according to our former works, it can be concluded that the original LDFT model may arouse obvious system errors for its simple mean field assumption in theory treatments.
2006, 22(03): 359-364
doi: 10.3866/PKU.WHXB20060321
Abstract:
The pharmacophore model of γ-secretase inhibitors was established by the Catalyst software with the training set of Benzodiazepine-based γ-secretase inhibitors. Based on the action mechanism and the known structure-activity relationship, a fitting pharmacophore model (RMS=0.366343, Correl=0.95535, Weight=1.17389, Config=18.8671) including two hydrogen-bonding acceptors, an aliphatic hydrophobic core and an aromatic ring center, was confirmed. This pharmacophore model will contribute to the design and synthesis of new-type γ-secretase inhibitors.
The pharmacophore model of γ-secretase inhibitors was established by the Catalyst software with the training set of Benzodiazepine-based γ-secretase inhibitors. Based on the action mechanism and the known structure-activity relationship, a fitting pharmacophore model (RMS=0.366343, Correl=0.95535, Weight=1.17389, Config=18.8671) including two hydrogen-bonding acceptors, an aliphatic hydrophobic core and an aromatic ring center, was confirmed. This pharmacophore model will contribute to the design and synthesis of new-type γ-secretase inhibitors.
2006, 22(03): 365-368
doi: 10.3866/PKU.WHXB20060322
Abstract:
The monodisperse spherical particles of TiO2 were prepared by sol-gel process in mixed solvents at low temperature. The TEM, SEM, and size distribution analysis showed that the size variation of as-synthesized spherical TiO2 colloidal particles is within 5% and the polyindex is 0.013. The thermal analysis clearly demonstrated that as-synthesized particles were hydrous amorphous TiO2. The structure of the TiO2 colloids after annealed at different temperatures were determined by XRD. The results showed that the phase transition from amorphous to anatase occurred at a temperature around 600 ℃ and both rutile and anatase appeared at 900 ℃.
The monodisperse spherical particles of TiO2 were prepared by sol-gel process in mixed solvents at low temperature. The TEM, SEM, and size distribution analysis showed that the size variation of as-synthesized spherical TiO2 colloidal particles is within 5% and the polyindex is 0.013. The thermal analysis clearly demonstrated that as-synthesized particles were hydrous amorphous TiO2. The structure of the TiO2 colloids after annealed at different temperatures were determined by XRD. The results showed that the phase transition from amorphous to anatase occurred at a temperature around 600 ℃ and both rutile and anatase appeared at 900 ℃.
2006, 22(03): 369-372
doi: 10.3866/PKU.WHXB20060323
Abstract:
The measurement of the fluorescence, UV-Vis absorption, FTIR and XPS spectroscopy demonstrated that the oxygen atom in polydimethylsioxane (PDMS) can coordinate with Tb3+, forming the complex of Tb3+ and PDMS complex (Tb3+-PDMS). It was found that after Tb3+-PDMS is formed, both the fluorescence emissions of PDMS and Tb3+ in the complex are enhanced comparing with that of Tb3+ and PDMS. The enhancement of the fluorescence intensity of the complex is related to the content of Tb3+ in the complex. When the content of Tb3+ in the complex is 2.0%(w), the fluorescence intensity of the complex is largest. The fluorescence intensity can be enhanced by 1547%.
The measurement of the fluorescence, UV-Vis absorption, FTIR and XPS spectroscopy demonstrated that the oxygen atom in polydimethylsioxane (PDMS) can coordinate with Tb3+, forming the complex of Tb3+ and PDMS complex (Tb3+-PDMS). It was found that after Tb3+-PDMS is formed, both the fluorescence emissions of PDMS and Tb3+ in the complex are enhanced comparing with that of Tb3+ and PDMS. The enhancement of the fluorescence intensity of the complex is related to the content of Tb3+ in the complex. When the content of Tb3+ in the complex is 2.0%(w), the fluorescence intensity of the complex is largest. The fluorescence intensity can be enhanced by 1547%.
2006, 22(03): 373-377
doi: 10.3866/PKU.WHXB20060324
Abstract:
The precursor Ti(OEt)4 was prepared by anodic dissolution of metallic titanium in absolute ethanol and directly hydrolyzed to prepare nanocrystalline TiO2-carbon nanotube(nanoTiO2-CNT) complex film by a sol-gel process. Redox behavior and electrocatalytic activities of the nanoTiO2-CNT complex film electrode were investigated by cyclic voltammetry (CV) and bulk electrolysis in DMF solution. It was found that there were two pairs of well-defined redox peaks for nanoTiO2-CNT complex film electrode with Er1/2 of －1.27 V and －2.44 V(vs SCE) at 100 mV•s-1 in correspondence with TiO2/Ti2O3 reversible and TiO2/Ti(OH)3 quasi-reversible electrode process, and the heterogeneous electrocatalytic reduction activities of TiO2/Ti(OH)3 redox system for furfural; The indirect electroreduction of furfural to furfural alcohol by Ti(IV)/Ti(III) redox system on nanoTiO2-CNT complex film surface in DMF. The electrode reaction mechanism is the called catalytic (EC′) mechanism.
The precursor Ti(OEt)4 was prepared by anodic dissolution of metallic titanium in absolute ethanol and directly hydrolyzed to prepare nanocrystalline TiO2-carbon nanotube(nanoTiO2-CNT) complex film by a sol-gel process. Redox behavior and electrocatalytic activities of the nanoTiO2-CNT complex film electrode were investigated by cyclic voltammetry (CV) and bulk electrolysis in DMF solution. It was found that there were two pairs of well-defined redox peaks for nanoTiO2-CNT complex film electrode with Er1/2 of －1.27 V and －2.44 V(vs SCE) at 100 mV•s-1 in correspondence with TiO2/Ti2O3 reversible and TiO2/Ti(OH)3 quasi-reversible electrode process, and the heterogeneous electrocatalytic reduction activities of TiO2/Ti(OH)3 redox system for furfural; The indirect electroreduction of furfural to furfural alcohol by Ti(IV)/Ti(III) redox system on nanoTiO2-CNT complex film surface in DMF. The electrode reaction mechanism is the called catalytic (EC′) mechanism.
2006, 22(03): 378-382
doi: 10.3866/PKU.WHXB20060325
Abstract:
The electrodeposition conditions for the preparation of copper deposits with fully preferred orientation were investigated in detail. XRD results of copper electrodeposits showed that texture with (110) could be improved by either polyethylene glycol (PEG) or chloride ions. However, the presence of the both additives resulted in a fully preferred orientation of (110) plane because of the strong synergistic effect between PEG and Cl－. The strong adsorption of PEG and Cl－ on different lattice planes of different grains was thought to be responsible for the preferential growth. The microstress of the copper deposits with fully preferred orientation was small which indicated that the deposits were stable. The influence of PEG and Cl－ on the copper electrodeposition had also been studied.
The electrodeposition conditions for the preparation of copper deposits with fully preferred orientation were investigated in detail. XRD results of copper electrodeposits showed that texture with (110) could be improved by either polyethylene glycol (PEG) or chloride ions. However, the presence of the both additives resulted in a fully preferred orientation of (110) plane because of the strong synergistic effect between PEG and Cl－. The strong adsorption of PEG and Cl－ on different lattice planes of different grains was thought to be responsible for the preferential growth. The microstress of the copper deposits with fully preferred orientation was small which indicated that the deposits were stable. The influence of PEG and Cl－ on the copper electrodeposition had also been studied.
2006, 22(03): 383-387
doi: 10.3866/PKU.WHXB20060326
Abstract:
SnSe thin film has been successfully fabricated by using pulsed laser ablation of mixed target of Sn and Se. The structure and electrochemical properties of the as-deposited thin film at different substrate temperatures have been investigated by X-ray diffraction (XRD), the charge/discharge and cyclic voltammetry (CV) measurements. The thin film deposited at room temperature consisted of a mixture of Sn and Se. When the substrate temperature was 200 ℃, the as-deposited thin film was mainly composed of crystallized SnSe. The reversible discharge capacities fell into the range from 260 mAh•g-1 to 498 mAh•g-1. A reduction and an oxidation peaks at 0.75 V and 2.17 V from CV curves of Li/SnSe cell were firstly found, indicating the reversible formation and decomposition of Li2Se. This feature is utterly different from those of SnOx and SnSx, in which Li2O and Li2S are inactive. The lithium electrochemical reaction of SnSe thin film electrode was investigated by XRD. Both classical alloying process and the selenylation-reduction of metal tin were revealed in lithium electrochemical reaction of SnSe. SnSe as the starting material for conversion to the Li-Sn alloy can improve its electrochemical performance with high reversible capacity and od stable cycle, demonstrating to be one of promise anode materials for future rechargeable lithium batteries.
SnSe thin film has been successfully fabricated by using pulsed laser ablation of mixed target of Sn and Se. The structure and electrochemical properties of the as-deposited thin film at different substrate temperatures have been investigated by X-ray diffraction (XRD), the charge/discharge and cyclic voltammetry (CV) measurements. The thin film deposited at room temperature consisted of a mixture of Sn and Se. When the substrate temperature was 200 ℃, the as-deposited thin film was mainly composed of crystallized SnSe. The reversible discharge capacities fell into the range from 260 mAh•g-1 to 498 mAh•g-1. A reduction and an oxidation peaks at 0.75 V and 2.17 V from CV curves of Li/SnSe cell were firstly found, indicating the reversible formation and decomposition of Li2Se. This feature is utterly different from those of SnOx and SnSx, in which Li2O and Li2S are inactive. The lithium electrochemical reaction of SnSe thin film electrode was investigated by XRD. Both classical alloying process and the selenylation-reduction of metal tin were revealed in lithium electrochemical reaction of SnSe. SnSe as the starting material for conversion to the Li-Sn alloy can improve its electrochemical performance with high reversible capacity and od stable cycle, demonstrating to be one of promise anode materials for future rechargeable lithium batteries.
2006, 22(03): 388-390
doi: 10.3866/PKU.WHXB20060327
Abstract:
A novel method based on three-dimensional holographic vector of atomic interaction field (3D-HoVAIF) was employed to express 3D structures of 68 dihydrofolate reductase (DHFR) inhibitors and 48 bitter tasting thresholds (BTT). Better model was developed based on multiple linear regression (MLR) through a stepwise manner for DHFR and genetic arithmetic-partial least square for BTT, and the following results were obtained: the multiple correlation coefficient (Rmm2) of 0.893 and 0.936, the cross validated RCV2 of 0.853 and 0.849 by the leave-one-out procedure, respectively. atisfactory results showed that information related to biological activities of DHFR and BTT can preferably be expressed by 3D-HoVAIF with definite physical and chemical meaning, easy interpretation, and well understanding, which may become a useful structural expression technique to study quantitative structure-activity relationships (QSAR) for various bioactive substances.
A novel method based on three-dimensional holographic vector of atomic interaction field (3D-HoVAIF) was employed to express 3D structures of 68 dihydrofolate reductase (DHFR) inhibitors and 48 bitter tasting thresholds (BTT). Better model was developed based on multiple linear regression (MLR) through a stepwise manner for DHFR and genetic arithmetic-partial least square for BTT, and the following results were obtained: the multiple correlation coefficient (Rmm2) of 0.893 and 0.936, the cross validated RCV2 of 0.853 and 0.849 by the leave-one-out procedure, respectively. atisfactory results showed that information related to biological activities of DHFR and BTT can preferably be expressed by 3D-HoVAIF with definite physical and chemical meaning, easy interpretation, and well understanding, which may become a useful structural expression technique to study quantitative structure-activity relationships (QSAR) for various bioactive substances.
