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2008 Volume 24 Issue 9
2008, 24(09):
Abstract:
2008, 24(09): 1535-1539
doi: 10.1016/S1872-1508(08)60062-5
Abstract:
The structures and properties of some Schiff base compounds doped in organogels were investigated. It was found that although individual Schiff bases could not form organogels with organic solvents, they can gel by mixing with an organogelator, N,N’-bisoctadecyl-L-Boc-glutamic-diamide, which formed transparent organogels in dimethyl sulfoxide (DMSO) or toluene (Tol). The enhancement of doping Schiff bases fluorescence in the organogel was observed in comparison with that of the corresponding solution. Furthermore, in the DMSO organogel, the induced chirality was obtained fromthe doping Schiff base with long alkyl chain. In contrast, the Schiff bases without long alkyl chain could not formsupramolecular chiral assemblies in organogel. It was suggested that through gel formation the chirality of the gelator could be transferred to the Schiff base through hydrophobic interaction among the long alkyl chains.
The structures and properties of some Schiff base compounds doped in organogels were investigated. It was found that although individual Schiff bases could not form organogels with organic solvents, they can gel by mixing with an organogelator, N,N’-bisoctadecyl-L-Boc-glutamic-diamide, which formed transparent organogels in dimethyl sulfoxide (DMSO) or toluene (Tol). The enhancement of doping Schiff bases fluorescence in the organogel was observed in comparison with that of the corresponding solution. Furthermore, in the DMSO organogel, the induced chirality was obtained fromthe doping Schiff base with long alkyl chain. In contrast, the Schiff bases without long alkyl chain could not formsupramolecular chiral assemblies in organogel. It was suggested that through gel formation the chirality of the gelator could be transferred to the Schiff base through hydrophobic interaction among the long alkyl chains.
2008, 24(09): 1540-1546
doi: 10.3866/PKU.WHXB20080902
Abstract:
Composition and phase transformation mechanism in the oxidization process of CaO-FeOx-SiO2 (CFS) system with high iron content were investigated by comprehensive thermodynamic calculation and deduction. Variation of the iron valence states with oxygen equilibrium fractional pressure at different temperatures was calculated and phase microstructure was observed and confirmed by metallographic microscope, SEM, EDX, and XRD. Grain size and crystallizing quantity of magnetite were determined by imagine analyzer, and contents of iron in different valence states were obtained by chemical analysis. Thermodynamic regularity of oxidation process and magnetite (Fe3O4) precipitation were studied by calculation and confirmed by experiment data. Effects of CaO addition on enrichment of magnetite were also discussed. The results showed that, with increasing the oxygen partial pressure, content of magnetite grew up rapidly, became saturation and precipitate, iron was enriched into the magnetite phase. Main phases in the cooling down system were magnetite, fayalite (Fe2SiO4), and glass state silicate ((Fe, Ca)SiO4). In oxidizing process, contents of fayalite declined while those of magnetite increased. Above 1423 K, while keeping oxygen partial pressure lg(pO2 /p0)>-7.89, most iron was enriched into the magnetite phase and precipitated after cooling down, magnetite was always the first precipitated crystal phase. When molecule ratio n(Fe3+)/n(Fe2+) in the system was 1/4, initialmagnetite precipitate temperature was about 1640 K. As n(Fe3+)/n(Fe2+) ratio increased, crystal precipitated temperature became higher, and it was about 1720 K while n(Fe3+)/n(Fe2+)=1.8/1. Increasing the content of CaO in the systempromoted the enrichment of iron into magnetite phase during oxidizing process.
Composition and phase transformation mechanism in the oxidization process of CaO-FeOx-SiO2 (CFS) system with high iron content were investigated by comprehensive thermodynamic calculation and deduction. Variation of the iron valence states with oxygen equilibrium fractional pressure at different temperatures was calculated and phase microstructure was observed and confirmed by metallographic microscope, SEM, EDX, and XRD. Grain size and crystallizing quantity of magnetite were determined by imagine analyzer, and contents of iron in different valence states were obtained by chemical analysis. Thermodynamic regularity of oxidation process and magnetite (Fe3O4) precipitation were studied by calculation and confirmed by experiment data. Effects of CaO addition on enrichment of magnetite were also discussed. The results showed that, with increasing the oxygen partial pressure, content of magnetite grew up rapidly, became saturation and precipitate, iron was enriched into the magnetite phase. Main phases in the cooling down system were magnetite, fayalite (Fe2SiO4), and glass state silicate ((Fe, Ca)SiO4). In oxidizing process, contents of fayalite declined while those of magnetite increased. Above 1423 K, while keeping oxygen partial pressure lg(pO2 /p0)>-7.89, most iron was enriched into the magnetite phase and precipitated after cooling down, magnetite was always the first precipitated crystal phase. When molecule ratio n(Fe3+)/n(Fe2+) in the system was 1/4, initialmagnetite precipitate temperature was about 1640 K. As n(Fe3+)/n(Fe2+) ratio increased, crystal precipitated temperature became higher, and it was about 1720 K while n(Fe3+)/n(Fe2+)=1.8/1. Increasing the content of CaO in the systempromoted the enrichment of iron into magnetite phase during oxidizing process.
2008, 24(09): 1547-1552
doi: 10.3866/PKU.WHXB20080903
Abstract:
La0.9Cu0.1MnO3 and LaCoO3 catalysts were synthesized by amorphous complexing method. Platinum nanoparticles supported by these composite oxide catalysts were prepared by using colloid deposition process. The structure, morphology, and Pt valence of the catalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS); and the cataluminescence (CTL) response of CO over the catalysts was investigated. Because of the agglomeration of Pt nanoparticles at the surface of La0.9Cu0.1MnO3 catalyst, its cataluminescence spectra displayed a peak splitting, but the Pt/LaCoO3 system, where Pt nanoparticles dispersed well at its surface, did not exhibit the phenomenon. We can use the cataluminescence spectra of CO to determine the dispersed state of noble metal nanoparticles at the surface of supports.
La0.9Cu0.1MnO3 and LaCoO3 catalysts were synthesized by amorphous complexing method. Platinum nanoparticles supported by these composite oxide catalysts were prepared by using colloid deposition process. The structure, morphology, and Pt valence of the catalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS); and the cataluminescence (CTL) response of CO over the catalysts was investigated. Because of the agglomeration of Pt nanoparticles at the surface of La0.9Cu0.1MnO3 catalyst, its cataluminescence spectra displayed a peak splitting, but the Pt/LaCoO3 system, where Pt nanoparticles dispersed well at its surface, did not exhibit the phenomenon. We can use the cataluminescence spectra of CO to determine the dispersed state of noble metal nanoparticles at the surface of supports.
2008, 24(09): 1553-1557
doi: 10.1016/S1872-1508(08)60063-7
Abstract:
The electrochemical measurement and surface analysis methods were employed to investigate the corrosion behavior of steel A3 influenced by Thiobacillus ferrooxidans (T.f). Polarization curve results indicated that the presence of Thiobacillus ferrooxidans resulted in higher corrosion potential of the electrode and obviously accelerated the corrosion current density. Atomic force microscope (AFM) results showed that asymmetric biofilms adhered to the surface of steel A3 after 7 days of exposure. The scanning electronic microscopy (SEM) results showed that pitting appeared on the surface of steel A3 after 7 days of exposure in T.f solution, which was induced by the metabolismof bacteria and the morphology of the deposit. Pitting holes of steel A3 in T.f solution were deeper after 20 days of exposure, the presence of Thiobacillus ferrooxidans aggravated the localized corrosion of A3 steel.
The electrochemical measurement and surface analysis methods were employed to investigate the corrosion behavior of steel A3 influenced by Thiobacillus ferrooxidans (T.f). Polarization curve results indicated that the presence of Thiobacillus ferrooxidans resulted in higher corrosion potential of the electrode and obviously accelerated the corrosion current density. Atomic force microscope (AFM) results showed that asymmetric biofilms adhered to the surface of steel A3 after 7 days of exposure. The scanning electronic microscopy (SEM) results showed that pitting appeared on the surface of steel A3 after 7 days of exposure in T.f solution, which was induced by the metabolismof bacteria and the morphology of the deposit. Pitting holes of steel A3 in T.f solution were deeper after 20 days of exposure, the presence of Thiobacillus ferrooxidans aggravated the localized corrosion of A3 steel.
2008, 24(09): 1558-1562
doi: 10.1016/S1872-1508(08)60064-9
Abstract:
Conomarphin, a novel conopeptide containing D-amino acid, was identified from the venom of Conus marmoreus and classified into M-superfamily of conotoxin. In this article, we reported the 3D structure of conomarphin at pH 5 determined using 2D 1H NMR method in aqueous solution. Twenty converged structures of this peptide were obtained based on 205 distance constraints, 8 dihedral angle constraints, and 2 hydrogen bond constraints. The root mean square deviation (RMSD) values of the backbone atoms were (0.074依0.029) nm. The refined structure of conomarphin at pH 5 contained a short 310-helix at C-terminal of the peptide. It was also characterized by a loose loop centered at Ala6. Comparison of structural and electrostatic potential between conomarphin at pH 3 and pH 5 were presented. Although the solution structure of conomarphin at pH 5 shared part of the same secondary structure element with the structure of conomarphin at pH 3, it adopted a distinctive backbone conformation with the overall molecule resembling a“flexcual arm”when viewed fromthe front. Structural differences imply that this conopeptide is rather pH sensitive and its bioactivity in vivo might be related to the acidity.
Conomarphin, a novel conopeptide containing D-amino acid, was identified from the venom of Conus marmoreus and classified into M-superfamily of conotoxin. In this article, we reported the 3D structure of conomarphin at pH 5 determined using 2D 1H NMR method in aqueous solution. Twenty converged structures of this peptide were obtained based on 205 distance constraints, 8 dihedral angle constraints, and 2 hydrogen bond constraints. The root mean square deviation (RMSD) values of the backbone atoms were (0.074依0.029) nm. The refined structure of conomarphin at pH 5 contained a short 310-helix at C-terminal of the peptide. It was also characterized by a loose loop centered at Ala6. Comparison of structural and electrostatic potential between conomarphin at pH 3 and pH 5 were presented. Although the solution structure of conomarphin at pH 5 shared part of the same secondary structure element with the structure of conomarphin at pH 3, it adopted a distinctive backbone conformation with the overall molecule resembling a“flexcual arm”when viewed fromthe front. Structural differences imply that this conopeptide is rather pH sensitive and its bioactivity in vivo might be related to the acidity.
2008, 24(09): 1563-1567
doi: 10.3866/PKU.WHXB20080906
Abstract:
Under ultrasonic andusingthe additive LomarDas dispersant, the printing“ink”can be prepared with LiMn2O4, which was synthesized through a sol-gel method. Through an ink-jet printing process, thin film LiMn2O4 electrode with thickness of about 1.8 μm was fabricated successfully. XRD, TG-DTA, SEM, electrochemical impedance spectrum, CV, and charge/discharge tests were used to characterize the LiMn2O4 nano particles and LiMn2O4 thin film electrode. It was found that LiMn2O4 filmelectrode could be charge-discharged at relative high current rate and kept stable. At the current density of 100 μA·cm-2 (2C), the thin film LiMn2O4 electrode had an initial capacity of 109 mAh·g-1, after 54 cycles the discharge capacity remained 97.4%, as a value of 105 mAh·g-1. This od electrochemical behavior of LiMn2O4 thin filmelectrode was mainly due to the thin thickness of electrode and well-crystallized LiMn2O4 nano particles.
Under ultrasonic andusingthe additive LomarDas dispersant, the printing“ink”can be prepared with LiMn2O4, which was synthesized through a sol-gel method. Through an ink-jet printing process, thin film LiMn2O4 electrode with thickness of about 1.8 μm was fabricated successfully. XRD, TG-DTA, SEM, electrochemical impedance spectrum, CV, and charge/discharge tests were used to characterize the LiMn2O4 nano particles and LiMn2O4 thin film electrode. It was found that LiMn2O4 filmelectrode could be charge-discharged at relative high current rate and kept stable. At the current density of 100 μA·cm-2 (2C), the thin film LiMn2O4 electrode had an initial capacity of 109 mAh·g-1, after 54 cycles the discharge capacity remained 97.4%, as a value of 105 mAh·g-1. This od electrochemical behavior of LiMn2O4 thin filmelectrode was mainly due to the thin thickness of electrode and well-crystallized LiMn2O4 nano particles.
2008, 24(09): 1568-1572
doi: 10.3866/PKU.WHXB20080907
Abstract:
Ni/γ-Al2O3 catalysts modified by La2O3 were prepared with incipient wetness impregnation and used in biogas reforming to hydrogen. The catalysts were characterized with XRD, H2-TPR, BET, and TEM, respectively, and the relationship between the performance and the structural properties of the catalysts was investigated. The biogas was simulated with CH4 and CO2, and the volume ratio of CH4/CO2 was 1. The results showed that the amount of La2O3 added was a key influence factor. The increment of La2O3 in γ-Al2O3 support strengthened the interaction between Ni and γ-Al2O3. Appropriate accession of La2O3 could improve the reducibility of catalysts, increase the dispersity of metallic Ni on support, suppress the sintering of metallic Ni particles and enhance the adsorption of CO2 on support during the reaction. As a result, the performance of catalyst, including resistance to coking, activity and stability, was improved significantly. However, excessive addition of La2O3 deteriorated the performance of catalyst. It was found that the best performance of catalyst could be reached at the addition of 6% (w) La2O3 in γ-Al2O3.
Ni/γ-Al2O3 catalysts modified by La2O3 were prepared with incipient wetness impregnation and used in biogas reforming to hydrogen. The catalysts were characterized with XRD, H2-TPR, BET, and TEM, respectively, and the relationship between the performance and the structural properties of the catalysts was investigated. The biogas was simulated with CH4 and CO2, and the volume ratio of CH4/CO2 was 1. The results showed that the amount of La2O3 added was a key influence factor. The increment of La2O3 in γ-Al2O3 support strengthened the interaction between Ni and γ-Al2O3. Appropriate accession of La2O3 could improve the reducibility of catalysts, increase the dispersity of metallic Ni on support, suppress the sintering of metallic Ni particles and enhance the adsorption of CO2 on support during the reaction. As a result, the performance of catalyst, including resistance to coking, activity and stability, was improved significantly. However, excessive addition of La2O3 deteriorated the performance of catalyst. It was found that the best performance of catalyst could be reached at the addition of 6% (w) La2O3 in γ-Al2O3.
2008, 24(09): 1573-1578
doi: 10.3866/PKU.WHXB20080908
Abstract:
The NICS (nucleus-independent chemical shift) values of steady structures of the transition-metal pure clusters Nbn, Con (n≤4) and binary transition-metal clusters NbxCoy (x+y≤8) were calculated by using density functional theory. The electronic configurations of Nbn, Con (n≤4) and NbxCoy (x+y≤8) conformations were analyzed, and individual contributions of different orbitals to the NICS were discussed. The results indicated that s and p orbitals contributed to σ, πaromaticity of the clusters, and more importantly, d orbitals contributed to the δ aromaticity of the clusters.
The NICS (nucleus-independent chemical shift) values of steady structures of the transition-metal pure clusters Nbn, Con (n≤4) and binary transition-metal clusters NbxCoy (x+y≤8) were calculated by using density functional theory. The electronic configurations of Nbn, Con (n≤4) and NbxCoy (x+y≤8) conformations were analyzed, and individual contributions of different orbitals to the NICS were discussed. The results indicated that s and p orbitals contributed to σ, πaromaticity of the clusters, and more importantly, d orbitals contributed to the δ aromaticity of the clusters.
2008, 24(09): 1579-1583
doi: 10.1016/S1872-1508(08)60065-0
Abstract:
The radial breathing modes (RBMs) of (M )n and (BeO)n rings (n=3-10) were calculated using the density functional theory at B3LYP/6-31G(d) level. It was found that for large rings, the radial breathing mode (RBM) frequency was inversely proportional to the centre diameter, but the variation of bond length may lead to deviations from a linear behavior. The deviations caused by inverse cubic term of diameter and variation of bond length, became dramatic with the decrease of ring diameter. From the point of chemical bond view, using one-dimensional harmonic oscillator and the method of cascade and parallel connection of “springs”, the linear relation and deviations were explained. The model can be applied to nanotubes.
The radial breathing modes (RBMs) of (M )n and (BeO)n rings (n=3-10) were calculated using the density functional theory at B3LYP/6-31G(d) level. It was found that for large rings, the radial breathing mode (RBM) frequency was inversely proportional to the centre diameter, but the variation of bond length may lead to deviations from a linear behavior. The deviations caused by inverse cubic term of diameter and variation of bond length, became dramatic with the decrease of ring diameter. From the point of chemical bond view, using one-dimensional harmonic oscillator and the method of cascade and parallel connection of “springs”, the linear relation and deviations were explained. The model can be applied to nanotubes.
2008, 24(09): 1584-1588
doi: 10.1016/S1872-1508(08)60066-2
Abstract:
Photodegradation of a textile dye X3B and photoreduction of dichromate (Cr(VI)) in an acidic aqueous solution were studied under 320 nm cut-off UV light irradiation in the presence of two polyoxometalates (POM), H3PW12O40 (PW) and H4SiW12O40 (SiW). The reactions in POM-X3B-Cr(VI) systemwere faster than those in POM-X3B, POM-Cr(VI) and X3B-Cr(VI) systems. For all reactions, PWwas more photoactive than SiW. The reaction rates were proportional to the initial concentration of each component. The effects of N2, O2, and air were small but regular, indicating Cr(VI) photoreduction by a reduced POM. Quenching experiments with H2O2 and ethanol revealed that X3B photodegradation mainly occurred through hydroxyl radical (·OH). It was proposed that the production of·OH and a reduced POM- by the reaction between H2O and excited POM* was the rate determining step, with which all evidence could be well interpreted. Different effects of POM concentration in two-or three-component system on the reaction rates suggested that the reaction between H2Oand excited POM* was reversible.
Photodegradation of a textile dye X3B and photoreduction of dichromate (Cr(VI)) in an acidic aqueous solution were studied under 320 nm cut-off UV light irradiation in the presence of two polyoxometalates (POM), H3PW12O40 (PW) and H4SiW12O40 (SiW). The reactions in POM-X3B-Cr(VI) systemwere faster than those in POM-X3B, POM-Cr(VI) and X3B-Cr(VI) systems. For all reactions, PWwas more photoactive than SiW. The reaction rates were proportional to the initial concentration of each component. The effects of N2, O2, and air were small but regular, indicating Cr(VI) photoreduction by a reduced POM. Quenching experiments with H2O2 and ethanol revealed that X3B photodegradation mainly occurred through hydroxyl radical (·OH). It was proposed that the production of·OH and a reduced POM- by the reaction between H2O and excited POM* was the rate determining step, with which all evidence could be well interpreted. Different effects of POM concentration in two-or three-component system on the reaction rates suggested that the reaction between H2Oand excited POM* was reversible.
2008, 24(09): 1589-1596
doi: 10.3866/PKU.WHXB20080911
Abstract:
Commercial activated carbon (AC) was post-activated by means of simultaneous physical-chemical activation in order to produce porous carbon supports with different pore sizes and surface areas. Photocatalysts of AC-supported TiO2 were prepared by well-dispersed deposition using inorganic species of H2TiO3 as Ti source. Nitrogen adsorption, XRD, and SEM were used to characterize ACs and TiO2/ACs and to investigate the influence of AC surface area and pore size on the resultant catalysts. The photocatalytic performance of TiO2/AC catalysts was studied by degradation of methylene blue (MB) in aqueous solution. The influence of catalyst dosage and MB concentration on the degradation was investigated. The results showed that nano-TiO2 deposit was formed in the particle size of 12-20 nm. The larger the AC surface area and average pore size, the smaller the TiO2 particle formed on the carbon surface. It was found that TiO2/AC catalysts had a synergetic effect of AC adsorption and TiO2 photocatalysis on the degradation of MB, so that the efficiency increased significantly. The kinetics of MB degradation by TiO2/AC was of apparent first order reaction mechanism.
Commercial activated carbon (AC) was post-activated by means of simultaneous physical-chemical activation in order to produce porous carbon supports with different pore sizes and surface areas. Photocatalysts of AC-supported TiO2 were prepared by well-dispersed deposition using inorganic species of H2TiO3 as Ti source. Nitrogen adsorption, XRD, and SEM were used to characterize ACs and TiO2/ACs and to investigate the influence of AC surface area and pore size on the resultant catalysts. The photocatalytic performance of TiO2/AC catalysts was studied by degradation of methylene blue (MB) in aqueous solution. The influence of catalyst dosage and MB concentration on the degradation was investigated. The results showed that nano-TiO2 deposit was formed in the particle size of 12-20 nm. The larger the AC surface area and average pore size, the smaller the TiO2 particle formed on the carbon surface. It was found that TiO2/AC catalysts had a synergetic effect of AC adsorption and TiO2 photocatalysis on the degradation of MB, so that the efficiency increased significantly. The kinetics of MB degradation by TiO2/AC was of apparent first order reaction mechanism.
2008, 24(09): 1597-1601
doi: 10.3866/PKU.WHXB20080912
Abstract:
Li doping ZnO powders had been synthesized by using carbamide and glycine as fuel and zinc nitrate as oxidant. And then the as-synthesized powders were sintered by spark plasma sintering (SPS). XRD, SEM, and TEM were employed to characterize the microstructure and phase. The results showed that both Li doping ZnO powders and cramic were wurtzite without any other phases, the grain sizes of the powder and ceramic were 0.18-1.7 μm and 1-3 μstudied by XRD analysis. Li element occupied an interstitial site in ZnO powders and a substitutional site in ZnO target, a consequence of the Zn2+ ion being replaced by Li+, which introduced an acceptor level into the crystal. The results showed that the Li doping ZnO ceramic used as sputtering target was beneficial to the preparation of p-type ZnO film.
Li doping ZnO powders had been synthesized by using carbamide and glycine as fuel and zinc nitrate as oxidant. And then the as-synthesized powders were sintered by spark plasma sintering (SPS). XRD, SEM, and TEM were employed to characterize the microstructure and phase. The results showed that both Li doping ZnO powders and cramic were wurtzite without any other phases, the grain sizes of the powder and ceramic were 0.18-1.7 μm and 1-3 μstudied by XRD analysis. Li element occupied an interstitial site in ZnO powders and a substitutional site in ZnO target, a consequence of the Zn2+ ion being replaced by Li+, which introduced an acceptor level into the crystal. The results showed that the Li doping ZnO ceramic used as sputtering target was beneficial to the preparation of p-type ZnO film.
2008, 24(09): 1602-1608
doi: 10.3866/PKU.WHXB20080913
Abstract:
Geometries of manganese (III) 5,10,15-tris(pentafluorophenyl) corrole (TPFC)MnIII and its imidazole axial binding adduct (TPFC)MnIII(Im) were optimized by using DFT(UB3LYP) method at 6-31G* basis set level. Calculation results indicated that (TPFC)MnIII and (TPFC)MnIII(Im) had the same spin state (s=2) in their ground states. (TPFC) MnIII had a plane structure, whileMn atomin (TPFC)MnIII(Im) was above the corrole N4mean plane 0.02734 nm. NBOanalysis showed that the electronic configuration of centralMn atomin (TPFC)MnIII and (TPFC)MnIII(Im) was (dxz)1(dyz)1(dz2 )1(dx2-y2)1(dxy)0. The energies of frontier orbitals of (TPFC)MnIII(Im) were significantly higher than those of (TPFC)MnIII, and the Mn-imidazole d-pπ bonding could be found from β-(LUMO+3) obital of (TPFC)MnIII(Im). In addition, electronic spectra of (TPFC)MnIII and (TPFC)MnIII(Im) were calculated by using TD-UB3LYP/6-31G* method, and it could be found that Q band had more“four-orbital”characters than B band. CT band of (TPFC)MnIII was mainly contributed from β-(HOMO-1) to β-(LUMO+5) and β-HOMO to β-(LUMO+4) transitions, and CT band of (TPFC)MnIII(Im) was mainly contributed from β-(HOMO-1) to β-(LUMO+3) and β-HOMO to β-(LUMO+4) transitions.
Geometries of manganese (III) 5,10,15-tris(pentafluorophenyl) corrole (TPFC)MnIII and its imidazole axial binding adduct (TPFC)MnIII(Im) were optimized by using DFT(UB3LYP) method at 6-31G* basis set level. Calculation results indicated that (TPFC)MnIII and (TPFC)MnIII(Im) had the same spin state (s=2) in their ground states. (TPFC) MnIII had a plane structure, whileMn atomin (TPFC)MnIII(Im) was above the corrole N4mean plane 0.02734 nm. NBOanalysis showed that the electronic configuration of centralMn atomin (TPFC)MnIII and (TPFC)MnIII(Im) was (dxz)1(dyz)1(dz2 )1(dx2-y2)1(dxy)0. The energies of frontier orbitals of (TPFC)MnIII(Im) were significantly higher than those of (TPFC)MnIII, and the Mn-imidazole d-pπ bonding could be found from β-(LUMO+3) obital of (TPFC)MnIII(Im). In addition, electronic spectra of (TPFC)MnIII and (TPFC)MnIII(Im) were calculated by using TD-UB3LYP/6-31G* method, and it could be found that Q band had more“four-orbital”characters than B band. CT band of (TPFC)MnIII was mainly contributed from β-(HOMO-1) to β-(LUMO+5) and β-HOMO to β-(LUMO+4) transitions, and CT band of (TPFC)MnIII(Im) was mainly contributed from β-(HOMO-1) to β-(LUMO+3) and β-HOMO to β-(LUMO+4) transitions.
2008, 24(09): 1609-1614
doi: 10.3866/PKU.WHXB20080914
Abstract:
Sm2O3 nanoparticles were prepared in W/O reverse microemulsion composed of cetyltrimethylammonium bromide (CTAB), n-butanol, n-octane, Sm(NO3)3 brine, and ammonia water. Based on the pseudo-ternary phase diagrams of the microemulsions at 25 ℃, a microemulsion region for preparation of Sm2O3 was determined, and the precursor products of Sm2O3 nanoparticles were synthesized in the microemulsion region. The influences of the reactant concentration and the reaction time on the size of the precursors were studied. The result derived from thermal analysis (TG-DSC) indicated that the proper calcination temperature was 900 ℃. The structures and morphologies of the nanoparticles were characterized by X-ray powder diffraction (XRD), transmission electron microscope (TEM), nanoparticle size analyzer (NSA), and fluorescence spectroscope (FS), respectively. The results showed that the Sm2O3 fluorescent nanoparticles with narrow distribution in size could be obtained by using this method.
Sm2O3 nanoparticles were prepared in W/O reverse microemulsion composed of cetyltrimethylammonium bromide (CTAB), n-butanol, n-octane, Sm(NO3)3 brine, and ammonia water. Based on the pseudo-ternary phase diagrams of the microemulsions at 25 ℃, a microemulsion region for preparation of Sm2O3 was determined, and the precursor products of Sm2O3 nanoparticles were synthesized in the microemulsion region. The influences of the reactant concentration and the reaction time on the size of the precursors were studied. The result derived from thermal analysis (TG-DSC) indicated that the proper calcination temperature was 900 ℃. The structures and morphologies of the nanoparticles were characterized by X-ray powder diffraction (XRD), transmission electron microscope (TEM), nanoparticle size analyzer (NSA), and fluorescence spectroscope (FS), respectively. The results showed that the Sm2O3 fluorescent nanoparticles with narrow distribution in size could be obtained by using this method.
2008, 24(09): 1615-1619
doi: 10.3866/PKU.WHXB20080915
Abstract:
Pt/C catalysts with different Pt particle sizes were prepared with the organic sol method. Pt particles in the Pt/C catalyst had high dispersity and excellent homogenicity. The electrochemical study indicated that there was an obvious size effect of Pt particles on the electrocatalytic oxidation of ethanol. The Pt/C catalyst with 3.2 nm average size of the Pt particles exhibited the optimal electrocatalytic activity for the ethanol oxidation. The study of X-ray photoelectron spectroscopy (XPS) showed that the size effect of Pt/Ccatalysts on the electrocatalytic oxidation of ethanol was closely related to the Pt0 content and the specific surface area of the Pt particles.
Pt/C catalysts with different Pt particle sizes were prepared with the organic sol method. Pt particles in the Pt/C catalyst had high dispersity and excellent homogenicity. The electrochemical study indicated that there was an obvious size effect of Pt particles on the electrocatalytic oxidation of ethanol. The Pt/C catalyst with 3.2 nm average size of the Pt particles exhibited the optimal electrocatalytic activity for the ethanol oxidation. The study of X-ray photoelectron spectroscopy (XPS) showed that the size effect of Pt/Ccatalysts on the electrocatalytic oxidation of ethanol was closely related to the Pt0 content and the specific surface area of the Pt particles.
2008, 24(09): 1620-1624
doi: 10.1016/S1872-1508(08)60067-4
Abstract:
The corrosion and anodic dissolution behaviors of pure aluminumin Na2SnO3-containing 4 mol·L-1 KOH methanol-water mixed solutions with a methanol/water volume ratio of 4:1 were investigated. This was carried out by means of hydrogen collection, polarization curve, galvanostatic discharge, scanning electron microscopy (SEM), and energy dispersive analysis of X-ray (EDAX). The experimental results indicated that the addition of stannate inhibited the corrosion of aluminum in the 4 mol·L-1 KOH methanol-water solutions by the deposition of tin with a higher hydrogen evolution overpotential on the electrode surface. In the electrolytes with higher stannate contents the inhibiting effect decreased because of the occurrence of some cracks on the tin deposition film. The results of galvanostatic discharge showed that the discharge of aluminum in the Na2SnO3-containing 4 mol·L-1 KOH methanol-water solutions were obviously improved. In addition, the improvement effect enhanced with the increase of stannate content. It was noted that the aluminum anode showed a very flat discharge plateau at relatively low potentials in the electrolyte with 10.0 mmol·L-1 Na2SnO3 at 20 mA·cm-2 discharge current density.
The corrosion and anodic dissolution behaviors of pure aluminumin Na2SnO3-containing 4 mol·L-1 KOH methanol-water mixed solutions with a methanol/water volume ratio of 4:1 were investigated. This was carried out by means of hydrogen collection, polarization curve, galvanostatic discharge, scanning electron microscopy (SEM), and energy dispersive analysis of X-ray (EDAX). The experimental results indicated that the addition of stannate inhibited the corrosion of aluminum in the 4 mol·L-1 KOH methanol-water solutions by the deposition of tin with a higher hydrogen evolution overpotential on the electrode surface. In the electrolytes with higher stannate contents the inhibiting effect decreased because of the occurrence of some cracks on the tin deposition film. The results of galvanostatic discharge showed that the discharge of aluminum in the Na2SnO3-containing 4 mol·L-1 KOH methanol-water solutions were obviously improved. In addition, the improvement effect enhanced with the increase of stannate content. It was noted that the aluminum anode showed a very flat discharge plateau at relatively low potentials in the electrolyte with 10.0 mmol·L-1 Na2SnO3 at 20 mA·cm-2 discharge current density.
2008, 24(09): 1625-1630
doi: 10.1016/S1872-1508(08)60068-6
Abstract:
B3LYP/6-311++G** and MP2/6-311++G** calculations were used to analyze the interaction between hypochlorous acid (HOCl) and formyl chloride (HCOCl). The results showed that there were four equilibriumgeometries (S1, S2, S3, and S4) optimized at B3LYP/6-311++G** level, and all the equilibrium geometries were confirmed to be in stable states by analytical frequency calculations. Complexes S1 and S3 use the 5H atom of HOCl as proton donor and the terminal 1O atom of HCOCl as acceptor to form red shift hydrogen bond systems. However, the blue-shifted hydrogen bond (2C—3H…6O) coexists with 4Cl…5Ointeraction in structures S2. As for S4, it uses the 7Cl atomofHOCl as proton donor and the terminal 1O atom of HCOCl as acceptor to form red shift halogen bond system. Interaction energies between monomers in the four complexes corrected with basis set superposition error (BSSE) and zero-point vibrational energy (ZPVE) lie in the range from -5.05 to -14.76 kJ·mol-1 at MP2/6-311++G** level. The natural bond orbital (NBO) and atoms in molecules (AIM) theories have also been applied to explain the structures and the properties of the complexes.
B3LYP/6-311++G** and MP2/6-311++G** calculations were used to analyze the interaction between hypochlorous acid (HOCl) and formyl chloride (HCOCl). The results showed that there were four equilibriumgeometries (S1, S2, S3, and S4) optimized at B3LYP/6-311++G** level, and all the equilibrium geometries were confirmed to be in stable states by analytical frequency calculations. Complexes S1 and S3 use the 5H atom of HOCl as proton donor and the terminal 1O atom of HCOCl as acceptor to form red shift hydrogen bond systems. However, the blue-shifted hydrogen bond (2C—3H…6O) coexists with 4Cl…5Ointeraction in structures S2. As for S4, it uses the 7Cl atomofHOCl as proton donor and the terminal 1O atom of HCOCl as acceptor to form red shift halogen bond system. Interaction energies between monomers in the four complexes corrected with basis set superposition error (BSSE) and zero-point vibrational energy (ZPVE) lie in the range from -5.05 to -14.76 kJ·mol-1 at MP2/6-311++G** level. The natural bond orbital (NBO) and atoms in molecules (AIM) theories have also been applied to explain the structures and the properties of the complexes.
2008, 24(09): 1631-1636
doi: 10.3866/PKU.WHXB20080918
Abstract:
Cyclobis(paraquat-p-anthracene) is a novel electron-deficient macrocyclic host. One of the most important applications of the host is molecular recognition. The binding energies of the host to several guest molecules like water, ammonia, alcohol, and heterocycles were investigated. The structures of the host-guest complexes were optimized using DFT (density functional theory) at B3LYP/3-21G level. The energies of the complexes were calculated at B3LYP/6-31G(d) level. The binding energies of the complexes were obtained after the correction of basis set superposition error. The 13C and 3He chemical shifts of the complexes were calculated by the gauge-including atomic orbital (GIAO) method at B3LYP/3-21G level. It indicates that the host can bind the guest molecules via hydrogen bonds between the heteroatoms in the guest and hydrogen atoms in the host. The binding energies of the complexes were mainly affected by the number and distance of the hydrogen bonds. The energy gaps for some of the complexes were increased owing to the formation of the hydrogen bonds. At the same time, the chemical shifts of the carbon atoms on the C—H bonds connected with the hydrogen bonds in the complexes relative to those of the same carbon atoms in the host were transferred downfield. The aromaticities of the complexes were relevant to the binding energies and ways. The aromaticity of the host was increased by the weak interaction between the host and guest molecules. The cyclic current of the host was decreased, thus the aromaticity was lowered owing to too strong host-guest interaction and incorporation of the guest molecules inside the cavity of the host.
2008, 24(09): 1637-1642
doi: 10.3866/PKU.WHXB20080919
Abstract:
The calculations on the interaction between cytosine and carbon monoxide have been performed at B3LYP/6-311+G** level and six local minimum isomers have been found. Both C and O can combine with N—H bond of cytosine and then hydrogen bonds between them are formed. The carbon atom of CO has a privilege to bind with cytosine. The length of CO bond is diminished in C combined complexes and it is lengthened in O combined complexes. In addition, the frequencies of CO suffer blue shifts in the former and red shifts in the latter.
The calculations on the interaction between cytosine and carbon monoxide have been performed at B3LYP/6-311+G** level and six local minimum isomers have been found. Both C and O can combine with N—H bond of cytosine and then hydrogen bonds between them are formed. The carbon atom of CO has a privilege to bind with cytosine. The length of CO bond is diminished in C combined complexes and it is lengthened in O combined complexes. In addition, the frequencies of CO suffer blue shifts in the former and red shifts in the latter.
Electrooxidation of Ethanol at Ni-B Amorphous Alloy Electrode and Measurements of Kinetic Parameters
2008, 24(09): 1643-1649
doi: 10.3866/PKU.WHXB20080920
Abstract:
Electrocatalytic oxidation of ethanol at the nano Ni-B amorphous alloy powder microelectrode and the electroless Ni-B amorphous alloy microdisk electrode in alkaline media was studied by using cyclic voltammetry. It was found that the nano Ni-B amorphous alloy microelectrode had higher electrocatalytic activity for the oxidation of ethanol than the electroless Ni-B amorphous alloy microdisk electrode. The kinetic parameters were determined with the steady polarization curves. The rates of electrocatalytic oxidation of ethanol at the nano Ni-B amorphous alloy microelectrode in alkaline media were much higher than those at the highly preferred orientation (220) nickel electrode. The proton diffusion coefficient of Ni(OH)2 at the nano Ni-B amorphous alloy powder microelectrode determined by cyclic voltammetry was increased by about 2 orders of magnitude, in comparison with the reported values at Ni nanowire electrode and the spherical Ni(OH)2 microencapsulated by cobalt.
Electrocatalytic oxidation of ethanol at the nano Ni-B amorphous alloy powder microelectrode and the electroless Ni-B amorphous alloy microdisk electrode in alkaline media was studied by using cyclic voltammetry. It was found that the nano Ni-B amorphous alloy microelectrode had higher electrocatalytic activity for the oxidation of ethanol than the electroless Ni-B amorphous alloy microdisk electrode. The kinetic parameters were determined with the steady polarization curves. The rates of electrocatalytic oxidation of ethanol at the nano Ni-B amorphous alloy microelectrode in alkaline media were much higher than those at the highly preferred orientation (220) nickel electrode. The proton diffusion coefficient of Ni(OH)2 at the nano Ni-B amorphous alloy powder microelectrode determined by cyclic voltammetry was increased by about 2 orders of magnitude, in comparison with the reported values at Ni nanowire electrode and the spherical Ni(OH)2 microencapsulated by cobalt.
2008, 24(09): 1650-1654
doi: 10.3866/PKU.WHXB20080921
Abstract:
A novel one-dimensional zinc(II) coordination polymer [Zn(acac)2(4,4’-bipy)]n was solvothermally synthesized and characterized by IR, elemental analysis, thermal analysis, 1H NMR, and X-ray diffraction methods. The complex crystallized in monoclinic system, space group P2(1)/c with a=1.1366(10) nm, b=1.4914(14) nm, c=1.5534(10) nm, β=132.00(4)°, V=1.957(3) nm3, Z=4. It was confirmed that the Zn(acac)2 and 4,4’-bipy formed a one-dimension linear structure with molecular ratio of 1:1. The result of TG analysis showed that the title complex was stable under 197 ℃. The distribution of charges and the composition of frontier molecular orbits provided a od testimony for the coordination condition in the crystal structure.
A novel one-dimensional zinc(II) coordination polymer [Zn(acac)2(4,4’-bipy)]n was solvothermally synthesized and characterized by IR, elemental analysis, thermal analysis, 1H NMR, and X-ray diffraction methods. The complex crystallized in monoclinic system, space group P2(1)/c with a=1.1366(10) nm, b=1.4914(14) nm, c=1.5534(10) nm, β=132.00(4)°, V=1.957(3) nm3, Z=4. It was confirmed that the Zn(acac)2 and 4,4’-bipy formed a one-dimension linear structure with molecular ratio of 1:1. The result of TG analysis showed that the title complex was stable under 197 ℃. The distribution of charges and the composition of frontier molecular orbits provided a od testimony for the coordination condition in the crystal structure.
2008, 24(09): 1655-1661
doi: 10.3866/PKU.WHXB20080922
Abstract:
The ground-state structures of ZrnB(n=1-13) clusters were determined by using density functional theory (DFT). The second-order energy differences and fragmentation energies of the ground-state structures were calculated and discussed. The results indicated that the relative stabilities of Zr2B, Zr5B, and Zr12B were stronger than these of other sized clusters, especially Zr5B cluster possessed the highest stability. The electronic properties and magnetism were analyzed. The results showed that the energy gap of clusters presented an odd-even oscillation tendency along with n increase, especially, the energy gap of Zr12B cluster was as small as 0.015 eV, implying that Zr12B cluster possessed metallic-like features. The charge transfer gradually strengthened along with the n increase. For ZrnB(n=1-13) clusters but n=1 (ZrB), we found charge transferred fromBto Zr site. The magnetic moment of ZrB(5.000 μB) and Zr4B(3.000 μB) were bigger andthe totalmagnetic moment of ZrnB clusters mainly came fromthe localed 4d orbital of Zr atom.
The ground-state structures of ZrnB(n=1-13) clusters were determined by using density functional theory (DFT). The second-order energy differences and fragmentation energies of the ground-state structures were calculated and discussed. The results indicated that the relative stabilities of Zr2B, Zr5B, and Zr12B were stronger than these of other sized clusters, especially Zr5B cluster possessed the highest stability. The electronic properties and magnetism were analyzed. The results showed that the energy gap of clusters presented an odd-even oscillation tendency along with n increase, especially, the energy gap of Zr12B cluster was as small as 0.015 eV, implying that Zr12B cluster possessed metallic-like features. The charge transfer gradually strengthened along with the n increase. For ZrnB(n=1-13) clusters but n=1 (ZrB), we found charge transferred fromBto Zr site. The magnetic moment of ZrB(5.000 μB) and Zr4B(3.000 μB) were bigger andthe totalmagnetic moment of ZrnB clusters mainly came fromthe localed 4d orbital of Zr atom.
2008, 24(09): 1662-1668
doi: 10.3866/PKU.WHXB20080923
Abstract:
The gradient corrected density functional theory (DFT) calculations were presented on the adsorption of both hydrogen and sulfur on pure Pd(111), Cu(111) and Au(111) surfaces, as well as on PdM3(111), Pd2M2(111), and Pd3M(111) surfaces. The most favorable adsorption sites, binding energies and the relaxation during adsorption were obtained with a coverage of 0.25. The Pd surface exhibited the strongest adsorption of both hydrogen and sulfur atoms. Cu was the next and Au had the weakest affinity with them. The binding energies of adsorption of hydrogen and sulfur on PdM alloys decreased with the increase of the concentration of metal M, except Pd3Au, in which case, the adsorption of hydrogen on Pd3Au (111) surface was even stronger than that on pure Pd, due to the larger lattice constant. According to the values of binding energy, it was found that the binding energies of both hydrogen and sulfur on PdAu decreased slower than that on PdCu, when the concentration of Au was lower than 25% (molar fraction). However, they decreased quickly when the concentration of Au exceeded 50%. PdAu alloy with 25%-50% Au was a promising candidate to resist sulfur and also with high performance in hydrogen permeation.
The gradient corrected density functional theory (DFT) calculations were presented on the adsorption of both hydrogen and sulfur on pure Pd(111), Cu(111) and Au(111) surfaces, as well as on PdM3(111), Pd2M2(111), and Pd3M(111) surfaces. The most favorable adsorption sites, binding energies and the relaxation during adsorption were obtained with a coverage of 0.25. The Pd surface exhibited the strongest adsorption of both hydrogen and sulfur atoms. Cu was the next and Au had the weakest affinity with them. The binding energies of adsorption of hydrogen and sulfur on PdM alloys decreased with the increase of the concentration of metal M, except Pd3Au, in which case, the adsorption of hydrogen on Pd3Au (111) surface was even stronger than that on pure Pd, due to the larger lattice constant. According to the values of binding energy, it was found that the binding energies of both hydrogen and sulfur on PdAu decreased slower than that on PdCu, when the concentration of Au was lower than 25% (molar fraction). However, they decreased quickly when the concentration of Au exceeded 50%. PdAu alloy with 25%-50% Au was a promising candidate to resist sulfur and also with high performance in hydrogen permeation.
2008, 24(09): 1669-1674
doi: 10.3866/PKU.WHXB20080924
Abstract:
The precursor of sodium manganese oxide xerogel was prepared from Mn(CH3COO)2·4H2O and Na2CO3 solution by sol-gel method, then sodiummanganese oxide cathode materials were prepared through calcinating xerogel precursors in air atmosphere. The structure and performance of as-prepared cathode materials were characterized by Flourier-infrared spectra (FT-IR), thermogravimetric analysis (TG), X-ray diffractometer (XRD), scanning electron microscope (SEM), and galvanostatic charge/discharge. The results showed that layered sodium manganese oxide with a stable phase could be obtained at a temperature of about 600 ℃, and its crystal system was hexa nal P2 structure with space group P63/mmc. It had been found by PowderX calculation that the lattice parameters a was 0.284 nmand c was 1.116 nm. Since the radius of Na+ (0.095 nm) was bigger than Li+ (0.076 nm), limited removal of sodium ions fromthe layered host lattice could decrease the resistance of lithiuminsertion/deinsertion in MnO6 layers, and thus the electrochemical performance of the material could be apparently improved. The second discharge capacity of the material reached 176 mAh·g -1 at a rate of 25 mA·g -1 in the cutoff voltage range of 2.0-4.3 V, and the capacity retention was still 90.9%after 20 cycles.
The precursor of sodium manganese oxide xerogel was prepared from Mn(CH3COO)2·4H2O and Na2CO3 solution by sol-gel method, then sodiummanganese oxide cathode materials were prepared through calcinating xerogel precursors in air atmosphere. The structure and performance of as-prepared cathode materials were characterized by Flourier-infrared spectra (FT-IR), thermogravimetric analysis (TG), X-ray diffractometer (XRD), scanning electron microscope (SEM), and galvanostatic charge/discharge. The results showed that layered sodium manganese oxide with a stable phase could be obtained at a temperature of about 600 ℃, and its crystal system was hexa nal P2 structure with space group P63/mmc. It had been found by PowderX calculation that the lattice parameters a was 0.284 nmand c was 1.116 nm. Since the radius of Na+ (0.095 nm) was bigger than Li+ (0.076 nm), limited removal of sodium ions fromthe layered host lattice could decrease the resistance of lithiuminsertion/deinsertion in MnO6 layers, and thus the electrochemical performance of the material could be apparently improved. The second discharge capacity of the material reached 176 mAh·g -1 at a rate of 25 mA·g -1 in the cutoff voltage range of 2.0-4.3 V, and the capacity retention was still 90.9%after 20 cycles.
2008, 24(09): 1675-1680
doi: 10.3866/PKU.WHXB20080925
Abstract:
Layered double hydroxide (LDH) had been used as a carrier of acetylsalicylic acid (ASP) to prepare intercalation compound LDH-ASP via ion exchange reaction. The influence of release medium on the carrier was investigated through extrinsic release test and XRD, FT-IR, TEM, TG-DSC, and BET-N2 surface area characterizations. The results showed that the carrier’s laminar features weakened in a pH range from 4.30 to 6.89, but the LDH crystal-class kept unchanged. In a pH range from 2.48 to 4.30, the probable grating reaction between H2PO-4 and hydroxyls of LDH caused laminar carrier transformation into complex phosphates. Along with pH decreased from 6.89 to 2.48, the carrier’s purity decreased, crystallinity weakened, and micro-pore absorbability declined.
Layered double hydroxide (LDH) had been used as a carrier of acetylsalicylic acid (ASP) to prepare intercalation compound LDH-ASP via ion exchange reaction. The influence of release medium on the carrier was investigated through extrinsic release test and XRD, FT-IR, TEM, TG-DSC, and BET-N2 surface area characterizations. The results showed that the carrier’s laminar features weakened in a pH range from 4.30 to 6.89, but the LDH crystal-class kept unchanged. In a pH range from 2.48 to 4.30, the probable grating reaction between H2PO-4 and hydroxyls of LDH caused laminar carrier transformation into complex phosphates. Along with pH decreased from 6.89 to 2.48, the carrier’s purity decreased, crystallinity weakened, and micro-pore absorbability declined.
2008, 24(09): 1681-1684
doi: 10.3866/PKU.WHXB20080926
Abstract:
The electronic structure and magnetic properties of the molecule-based magnet [Cu(μ(H2O)]n (cbdca=cyclobutanedicarboxylate) compound with copper ions as the metallic magnetic center were studied using the FP_LAPW(first-principle full-potential linearized augmented plane wave) method of first-principles, based on density functional theory (DFT) with generalized gradient approximation (GGA) method and local spin density approximation (LSDA) method. The total energies of the ferromagnetic, antiferromagnetic, and non-magnetic phases of organic-inorganic metal phosphonoacetate [Cu(μ-cbdca)(H2O)]n were calculated. The calculations revealed that the compound [Cu(μ-cbdca)(H2O)]n had a stable metal-ferromagnetic ground state, which was in agreement with the experimental result. There were large and positive spin populations on copper (II) ions, small and positive populations on the oxygen and carbon atoms of the bidentate ligand, which connected to the copper ions.
The electronic structure and magnetic properties of the molecule-based magnet [Cu(μ(H2O)]n (cbdca=cyclobutanedicarboxylate) compound with copper ions as the metallic magnetic center were studied using the FP_LAPW(first-principle full-potential linearized augmented plane wave) method of first-principles, based on density functional theory (DFT) with generalized gradient approximation (GGA) method and local spin density approximation (LSDA) method. The total energies of the ferromagnetic, antiferromagnetic, and non-magnetic phases of organic-inorganic metal phosphonoacetate [Cu(μ-cbdca)(H2O)]n were calculated. The calculations revealed that the compound [Cu(μ-cbdca)(H2O)]n had a stable metal-ferromagnetic ground state, which was in agreement with the experimental result. There were large and positive spin populations on copper (II) ions, small and positive populations on the oxygen and carbon atoms of the bidentate ligand, which connected to the copper ions.
2008, 24(09): 1685-1688
doi: 10.3866/PKU.WHXB20080927
Abstract:
XPS spectra were used to determine the binding energies for Pt-PVP nanoparticles before and after Ar+ ion sputtering, as well as for some oxides nanoparticles (TiO2, ZnO, and SiO2). The binding energies of the nanoparticles were compared with those of the corresponding bulk materials. The results showed that, compared with bulk Pt, the Pt 4f binding energy of Pt-PVP nanoparticles before Ar + ion sputtering shifted to lower binding energy side. After Ar+ sputtering, the PVP on Pt nanoparticles was sputtered away and the Pt nanoparticles became bare, the binding energy shifted to higher binding energy side. By comparison with the bulk oxides, the binding energies of TiO2, ZnO, and SiO2 nanoparticles also shifted to the higher binding energy side, and the magnitude of binding energy shift was in the order of TiO2<ZnO<SiO2. The effect of extra-atomic relaxation was used to explain the binding energy shift of nanoparticles.
XPS spectra were used to determine the binding energies for Pt-PVP nanoparticles before and after Ar+ ion sputtering, as well as for some oxides nanoparticles (TiO2, ZnO, and SiO2). The binding energies of the nanoparticles were compared with those of the corresponding bulk materials. The results showed that, compared with bulk Pt, the Pt 4f binding energy of Pt-PVP nanoparticles before Ar + ion sputtering shifted to lower binding energy side. After Ar+ sputtering, the PVP on Pt nanoparticles was sputtered away and the Pt nanoparticles became bare, the binding energy shifted to higher binding energy side. By comparison with the bulk oxides, the binding energies of TiO2, ZnO, and SiO2 nanoparticles also shifted to the higher binding energy side, and the magnitude of binding energy shift was in the order of TiO2<ZnO<SiO2. The effect of extra-atomic relaxation was used to explain the binding energy shift of nanoparticles.
2008, 24(09): 1689-1693
doi: 10.3866/PKU.WHXB20080928
Abstract:
A new low-cost method to prepare polycrystalline silicon thin films by solution-based aluminum-induced crystallization (AIC) was introduced in this article. Amorphous silicon (a-Si) thin films with 50 nm thickness were deposited by low-pressure chemical vapor deposition (LPCVD) and used as the precursors of crystallization. Aluminate solution with several components was spun on the surface of the a-Si films. Crystallization was accomplished at the annealing temperature between 550 and 620 ℃ for several hours in furnace and N2 ambience. The crystallization effect was dependent on the aluminumconcentration in aluminate solution and the surface status of the studied a-Si films. We found that the AIC process could take place only with solution containing meta-aluminates, and continuous polycrystalline silicon thin films could be obtained if the solution concentration was not too low. The natural oxide layers on the surface of a-Si films were od for adhesion of aluminate solution to the films and the formation of larger grains, but would lead to a higher crystallization temperature. In addition, various micrographic patterns taken fromthe crystallized films were observed, which were resulted from different kinds of Al-salt solution as the source for AIC. In one word, it was important to choose appropriate experiment parameters.
A new low-cost method to prepare polycrystalline silicon thin films by solution-based aluminum-induced crystallization (AIC) was introduced in this article. Amorphous silicon (a-Si) thin films with 50 nm thickness were deposited by low-pressure chemical vapor deposition (LPCVD) and used as the precursors of crystallization. Aluminate solution with several components was spun on the surface of the a-Si films. Crystallization was accomplished at the annealing temperature between 550 and 620 ℃ for several hours in furnace and N2 ambience. The crystallization effect was dependent on the aluminumconcentration in aluminate solution and the surface status of the studied a-Si films. We found that the AIC process could take place only with solution containing meta-aluminates, and continuous polycrystalline silicon thin films could be obtained if the solution concentration was not too low. The natural oxide layers on the surface of a-Si films were od for adhesion of aluminate solution to the films and the formation of larger grains, but would lead to a higher crystallization temperature. In addition, various micrographic patterns taken fromthe crystallized films were observed, which were resulted from different kinds of Al-salt solution as the source for AIC. In one word, it was important to choose appropriate experiment parameters.
2008, 24(09): 1694-1698
doi: 10.3866/PKU.WHXB20080929
Abstract:
V2.1TiNi0.4Zr0.06Cux (x=0-0.12) hydrogen storage alloys were prepared by induction melting with magnetic levitation, and the effects of Cu content on the microstructure and electrochemical properties of the alloys were investigated by XRD, SEM, EDS, and electrochemical test. It was found that all the alloys was consisted of a V-based solid solution main phase and a C14-type Laves secondary phase in the form of three-dimensional network. The secondary phase precipitates along the grain boundaries of the main phase. The unit cells of both main phase and secondary phase expand with increasing Cu content. The results showed that the maximum discharge capacity was improved and the activation behavior was invariable as some Cu (x=0.03-0.06) was added into the V2.1TiNi0.4Zr0.06 alloy. However, higher Cu content (x≥0.09) in the alloy impairs the discharge capacity. Furthermore, adding Cu into the V2.1TiNi0.4Zr0.06 alloy can improve its cycling stability and high-rate dischargeability significantly.
V2.1TiNi0.4Zr0.06Cux (x=0-0.12) hydrogen storage alloys were prepared by induction melting with magnetic levitation, and the effects of Cu content on the microstructure and electrochemical properties of the alloys were investigated by XRD, SEM, EDS, and electrochemical test. It was found that all the alloys was consisted of a V-based solid solution main phase and a C14-type Laves secondary phase in the form of three-dimensional network. The secondary phase precipitates along the grain boundaries of the main phase. The unit cells of both main phase and secondary phase expand with increasing Cu content. The results showed that the maximum discharge capacity was improved and the activation behavior was invariable as some Cu (x=0.03-0.06) was added into the V2.1TiNi0.4Zr0.06 alloy. However, higher Cu content (x≥0.09) in the alloy impairs the discharge capacity. Furthermore, adding Cu into the V2.1TiNi0.4Zr0.06 alloy can improve its cycling stability and high-rate dischargeability significantly.
2008, 24(09): 1699-1702
doi: 10.3866/PKU.WHXB20080930
Abstract:
Heat capacity Cp,m of 1-docosanol was precisely measured in the temperature range from 78 to 400 K by means of an automated adiabatic calorimeter. The dependence of heat capacity on the temperature was fitted to polynomial equations with least square method. The melting temperature, molar enthalpy, and molar entropy of fusion were determined to be 340.844 K, 85.07 kJ·mol-1, and 249.6 J·K-1·mol-1, respectively. The thermodynamic functions, [HT-H298.15] and [ST-S298.15], were derived from the thermodynamic equations in the temperature range from 80 to 400 K with an interval of 5 K. The thermostability of the compound was further investigated by DSC and TG techniques from400 to 900 K.
Heat capacity Cp,m of 1-docosanol was precisely measured in the temperature range from 78 to 400 K by means of an automated adiabatic calorimeter. The dependence of heat capacity on the temperature was fitted to polynomial equations with least square method. The melting temperature, molar enthalpy, and molar entropy of fusion were determined to be 340.844 K, 85.07 kJ·mol-1, and 249.6 J·K-1·mol-1, respectively. The thermodynamic functions, [HT-H298.15] and [ST-S298.15], were derived from the thermodynamic equations in the temperature range from 80 to 400 K with an interval of 5 K. The thermostability of the compound was further investigated by DSC and TG techniques from400 to 900 K.
2008, 24(09): 1703-1708
doi: 10.3866/PKU.WHXB20080931
Abstract:
Using combinational chip method, all-components Zn-Al film samples were prepared via ion beam sputtering. The as-deposited multilayer films were transformed into alloy films after annealing in Ar/H2 atmosphere for 2 h at 370 ℃. The compositom, structure, and morphology of the alloy films were characterized using Auger electron spectrum (AES), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results indicated that homogeneous alloy films with od crystallinity and dense surface were attained after low temperature annealing. The polarization resistance tests in 0.1 mol·L-1 NaCl for characterization of anti-corrosion properties indicated that the Zn-Al alloy thin films with Al mole fraction of about 87% possessed the highest polarization resistance. Further experiments showed that the polarization resistances of Zn-Al alloy thin films with Al mole fraction from 83% to 86% were all higher than 105 Ω·cm-2, which was one order higher than that of hot dip galvanizing coating.
Using combinational chip method, all-components Zn-Al film samples were prepared via ion beam sputtering. The as-deposited multilayer films were transformed into alloy films after annealing in Ar/H2 atmosphere for 2 h at 370 ℃. The compositom, structure, and morphology of the alloy films were characterized using Auger electron spectrum (AES), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results indicated that homogeneous alloy films with od crystallinity and dense surface were attained after low temperature annealing. The polarization resistance tests in 0.1 mol·L-1 NaCl for characterization of anti-corrosion properties indicated that the Zn-Al alloy thin films with Al mole fraction of about 87% possessed the highest polarization resistance. Further experiments showed that the polarization resistances of Zn-Al alloy thin films with Al mole fraction from 83% to 86% were all higher than 105 Ω·cm-2, which was one order higher than that of hot dip galvanizing coating.
2008, 24(09): 1709-1713
doi: 10.3866/PKU.WHXB20080932
Abstract:
Fluorescence spectroscopic properties of p-N,N-dimethylaminobenzonitrile (DMABN) in various kinds of surfactant micellar solutions were investigated. The results showed that the characteristics of the palisade layers of different surfactant micelles affected the twisted intramolecular charge transfer (TICT) properties of DMABN. In the ionic micellar solution, the electric field of the charged head-groups in the palisade layer was found to be a main affecting factor that promoting the formation of TICT state. The larger of the counterion dissociation degree, the stronger of Ia/Ib in the micellar solution. In the nonionic micellar solution, the effect of hydrogen bonding became distinct due to a large amount of water wrapped in the shell of the poly(ethylene oxide) (PEO) chains. Besides, the terminal hydroxyl groups of the short PEO chains were also able to hydrogen-bond with DMABN. In the view of photo-physics of DMABN, the anionic micelles with large dissociation degree of the counterions were suitable to as DMABN dispersed carriers for their TICT properties, for example, SDS or SDSO.
Fluorescence spectroscopic properties of p-N,N-dimethylaminobenzonitrile (DMABN) in various kinds of surfactant micellar solutions were investigated. The results showed that the characteristics of the palisade layers of different surfactant micelles affected the twisted intramolecular charge transfer (TICT) properties of DMABN. In the ionic micellar solution, the electric field of the charged head-groups in the palisade layer was found to be a main affecting factor that promoting the formation of TICT state. The larger of the counterion dissociation degree, the stronger of Ia/Ib in the micellar solution. In the nonionic micellar solution, the effect of hydrogen bonding became distinct due to a large amount of water wrapped in the shell of the poly(ethylene oxide) (PEO) chains. Besides, the terminal hydroxyl groups of the short PEO chains were also able to hydrogen-bond with DMABN. In the view of photo-physics of DMABN, the anionic micelles with large dissociation degree of the counterions were suitable to as DMABN dispersed carriers for their TICT properties, for example, SDS or SDSO.
2008, 24(09): 1714-1718
doi: 10.3866/PKU.WHXB20080933
Abstract:
Selective adsorptive desulfurization of model gasolines containing different amounts of aromatics and olefin compounds, such as benzene and 1-octene, on Ce(IV)Y zeolite was studied using a fixed-bed adsorption column, Fourier transform-infrared spectroscopy (FT-IR), and ultraviolet diffuse reflection spectroscopy (UV-DRS) techniques. It was found that both benzene and 1-octene had strong inhibiting effects on the desulfurization which could be detected by the decreases in the desulfurization capacities of the Ce(IV)Yin the presence of benzene and 1-octene in the model gasoline. The FT-IR and UV-DRS spectra of the Ce(IV)Y zeolites adsorbing the model gasolines revealed that benzene was desorbed easily because of the formation of π-complexes, while 1-octene was desorbed difficultly due to the strong interactions between the double-bond of 1-octene and the Ce4+ to form the π-complexes through the σ-π electron donations. Therefore, it could be concluded that the effect of benzene on the adsorptive removal of sulfur compounds could be ascribed to the competitive adsorption on the Ce(IV)Ybetween the aromatics and the organosulfur compounds in the fuels. While for the effect of 1-octene, the Ce(IV)Y zeolites adsorbed preferentially the 1-octene molecules onto adsorption sites, resulting in descending adsorptive selectivity for removing thiophene from the model fuel containing even minor amount of olefin.
Selective adsorptive desulfurization of model gasolines containing different amounts of aromatics and olefin compounds, such as benzene and 1-octene, on Ce(IV)Y zeolite was studied using a fixed-bed adsorption column, Fourier transform-infrared spectroscopy (FT-IR), and ultraviolet diffuse reflection spectroscopy (UV-DRS) techniques. It was found that both benzene and 1-octene had strong inhibiting effects on the desulfurization which could be detected by the decreases in the desulfurization capacities of the Ce(IV)Yin the presence of benzene and 1-octene in the model gasoline. The FT-IR and UV-DRS spectra of the Ce(IV)Y zeolites adsorbing the model gasolines revealed that benzene was desorbed easily because of the formation of π-complexes, while 1-octene was desorbed difficultly due to the strong interactions between the double-bond of 1-octene and the Ce4+ to form the π-complexes through the σ-π electron donations. Therefore, it could be concluded that the effect of benzene on the adsorptive removal of sulfur compounds could be ascribed to the competitive adsorption on the Ce(IV)Ybetween the aromatics and the organosulfur compounds in the fuels. While for the effect of 1-octene, the Ce(IV)Y zeolites adsorbed preferentially the 1-octene molecules onto adsorption sites, resulting in descending adsorptive selectivity for removing thiophene from the model fuel containing even minor amount of olefin.
2008, 24(09): 1719-1723
doi: 10.3866/PKU.WHXB20080934
Abstract:
Finite field polymerization was applied to prepare carbon nanotubes-polyaniline (CNTs-PANI) composite based on coating polyaniline on the surface of the CNTs. The microstructure and component of the obtained materials were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), and Fourier transform infrared (FTIR) spectroscopy. The electrochemical performances of the samples were tested by cyclic voltammogram and galvanostatic charge/discharge by assembling the materials into electrochemical supercapacitors. The results showed that PANI could symmetrically grow on the surface of the CNTs by the finite field method. The specific capacitance of the obtained composite material was about 117.7 F·g-1 (organic electrolyte) whereas the specific capacitances of the pure CNTs and the pure PANI were about 25.0 and 65.0 F·g-1 at the same conditions. All these indicated that the finite field polymerization was a promising method to prepare nano-composite.
Finite field polymerization was applied to prepare carbon nanotubes-polyaniline (CNTs-PANI) composite based on coating polyaniline on the surface of the CNTs. The microstructure and component of the obtained materials were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), and Fourier transform infrared (FTIR) spectroscopy. The electrochemical performances of the samples were tested by cyclic voltammogram and galvanostatic charge/discharge by assembling the materials into electrochemical supercapacitors. The results showed that PANI could symmetrically grow on the surface of the CNTs by the finite field method. The specific capacitance of the obtained composite material was about 117.7 F·g-1 (organic electrolyte) whereas the specific capacitances of the pure CNTs and the pure PANI were about 25.0 and 65.0 F·g-1 at the same conditions. All these indicated that the finite field polymerization was a promising method to prepare nano-composite.
Inhibition Action and Adsorption Behavior of Environment-Friendly Inhibitor Poly-Aspartate on Copper
2008, 24(09): 1724-1728
doi: 10.3866/PKU.WHXB20080935
Abstract:
The inhibition action and adsorption behavior of an environment-friendly inhibitor poly-aspartate (PASP) on copper in aqueous NaCl (0.02%) solution were investigated by means of electrochemical techniques. The results indicated that the best inhibition efficiency of PASP was 78.3% with the concentration of 15 mg·L-1 at 20 ℃. The adsorption of PASP prevented Cu from being corroded and PASP was an anodic inhibitor. The inhibition efficiency of PASP decreased with the increase in solution temperature, it decreased to 40.4% at 50 ℃. The adsorption behavior of PASP followed Langmuir isotherm, it was spontaneous and exothermic, and belonged to chemical adsorption.
The inhibition action and adsorption behavior of an environment-friendly inhibitor poly-aspartate (PASP) on copper in aqueous NaCl (0.02%) solution were investigated by means of electrochemical techniques. The results indicated that the best inhibition efficiency of PASP was 78.3% with the concentration of 15 mg·L-1 at 20 ℃. The adsorption of PASP prevented Cu from being corroded and PASP was an anodic inhibitor. The inhibition efficiency of PASP decreased with the increase in solution temperature, it decreased to 40.4% at 50 ℃. The adsorption behavior of PASP followed Langmuir isotherm, it was spontaneous and exothermic, and belonged to chemical adsorption.
2008, 24(09): 1729-1732
doi: 10.3866/PKU.WHXB20080936
Abstract:
The electrocatalytic performance of the Ir catalyst prepared with a new complex reduction method using NH4F as the complexing reagent for the oxidation of ammonia was reported. The results indicated that the average size of Ir particles in the Ir catalyst prepared with the complex reduction method was 2.8 nm, which was much smaller than that (7.5 nm) of the Ir catalyst prepared with the reduction method without the complexing reagent, because Ir3+ could form the complex with NH4F. Thus, the electrocatalytic activity and stability of the Ir catalyst prepared with the complex reduction method for the oxidation of ammonia are better than that of the Ir catalyst prepared with the reduction method without the complexing reagent. This preparation method is very simple. Therefore, it is hopeful to have a practical application in the catalyst preparation.
The electrocatalytic performance of the Ir catalyst prepared with a new complex reduction method using NH4F as the complexing reagent for the oxidation of ammonia was reported. The results indicated that the average size of Ir particles in the Ir catalyst prepared with the complex reduction method was 2.8 nm, which was much smaller than that (7.5 nm) of the Ir catalyst prepared with the reduction method without the complexing reagent, because Ir3+ could form the complex with NH4F. Thus, the electrocatalytic activity and stability of the Ir catalyst prepared with the complex reduction method for the oxidation of ammonia are better than that of the Ir catalyst prepared with the reduction method without the complexing reagent. This preparation method is very simple. Therefore, it is hopeful to have a practical application in the catalyst preparation.
2008, 24(09): 1733-1738
doi: 10.3866/PKU.WHXB20080937
Abstract:
The effect of CO2-3 on copper electrodeposits from 1-hydroxyethylidene-1,1-diphosphonic acid (HEDPA) baths was investigated over a wide range of concentration by electrochemical measurements, XRD, and IR spectra of the complex. It could be seen from potentiodynamic polarization curves that CO2-3 in the bath could not only enhance the cathodic polarization but also promote anodic dissolution. The X-ray diffraction results indicated the changing of preferred orientation of the copper deposits, from a preferential growth orientation (222) plane containing little CO2-3 to (111) plane containing more CO2-3. The IR spectra of the solid complex purified from the bath showed that CO2-3 could enter the complex and stabilize Cu2+ in the structure as the second ligand, so the potential of copper deposition was negatively shifted and the (111) plane orientation was preferred.
The effect of CO2-3 on copper electrodeposits from 1-hydroxyethylidene-1,1-diphosphonic acid (HEDPA) baths was investigated over a wide range of concentration by electrochemical measurements, XRD, and IR spectra of the complex. It could be seen from potentiodynamic polarization curves that CO2-3 in the bath could not only enhance the cathodic polarization but also promote anodic dissolution. The X-ray diffraction results indicated the changing of preferred orientation of the copper deposits, from a preferential growth orientation (222) plane containing little CO2-3 to (111) plane containing more CO2-3. The IR spectra of the solid complex purified from the bath showed that CO2-3 could enter the complex and stabilize Cu2+ in the structure as the second ligand, so the potential of copper deposition was negatively shifted and the (111) plane orientation was preferred.
