Login In
2004 Volume 20 Issue 8
2004, 20(08): 785-789
doi: 10.3866/PKU.WHXB20040801
Abstract:
By combining the genetic al rithm, fast simulated annealing and conjugated gradient al rithm, a novel global optimization method, termed as fast hybrid global optimized al rithm (FH A), was proposed and applied to global geometry optimization of water clusters (H2O)n. In the case of TIP3P, we found lower energy water clusters compared with those reported in literature and the computational efficiency by using FH A has been greatly improved. In the case of TIPS2, the global optimized geometries of water clusters (H2O)n in the size range of 2 to 27 were found. The water clusters are all-surface structures when n < 17,and the cage structure with one interior water molecule and two interior water molecules appear when n=17 and n=25, respectively. This transformation from all-surface structure to the cage structure with one interior water molecule and then to the cage structure with two interior water molecules is in agreement with the case of TTM2-F.The results of this work show that TIPS2 has the ability of modeling large water clusters and is a suitable potential function for MD and MC simulation.
By combining the genetic al rithm, fast simulated annealing and conjugated gradient al rithm, a novel global optimization method, termed as fast hybrid global optimized al rithm (FH A), was proposed and applied to global geometry optimization of water clusters (H2O)n. In the case of TIP3P, we found lower energy water clusters compared with those reported in literature and the computational efficiency by using FH A has been greatly improved. In the case of TIPS2, the global optimized geometries of water clusters (H2O)n in the size range of 2 to 27 were found. The water clusters are all-surface structures when n < 17,and the cage structure with one interior water molecule and two interior water molecules appear when n=17 and n=25, respectively. This transformation from all-surface structure to the cage structure with one interior water molecule and then to the cage structure with two interior water molecules is in agreement with the case of TTM2-F.The results of this work show that TIPS2 has the ability of modeling large water clusters and is a suitable potential function for MD and MC simulation.
2004, 20(08): 790-794
doi: 10.3866/PKU.WHXB20040802
Abstract:
The spinel LiMn2O4 synthesized by the method of solid-state reaction was modified with aluminum oxide through the heterogeneous nucleation process. The pristine and surface-modified spinel LiMn2O4 were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM) and particle size analysis. Effects of the surface-modification and preparation conditions on the cycleability and the rate capability were studied. The initial capacity of unmodified LiMn2O4 was 86.5 mA•h•g－1 and the capacity fade was 26.3％ after 50 cycles. The initial capacities of LiMn2O4 modified with 0.5％ and 1％(w) aluminum oxide were 96.0 mA•h•g－1 and 80.1 mA•h•g－1, and the capacity fades were 7.0％ and 5.6％, respectively. The results showed that the cycling life of LiMn2O4 was clearly improved by modification of aluminum oxide through the process of heterogeneous nucleation. With the increase of aluminum oxide, the cycling life increases, however, the capacity obviously decreases. The process of heterogeneous nucleation showed some special characters, such as the homogeneous coating. It is more suitable for the surface-modification of LiMn2O4.
The spinel LiMn2O4 synthesized by the method of solid-state reaction was modified with aluminum oxide through the heterogeneous nucleation process. The pristine and surface-modified spinel LiMn2O4 were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM) and particle size analysis. Effects of the surface-modification and preparation conditions on the cycleability and the rate capability were studied. The initial capacity of unmodified LiMn2O4 was 86.5 mA•h•g－1 and the capacity fade was 26.3％ after 50 cycles. The initial capacities of LiMn2O4 modified with 0.5％ and 1％(w) aluminum oxide were 96.0 mA•h•g－1 and 80.1 mA•h•g－1, and the capacity fades were 7.0％ and 5.6％, respectively. The results showed that the cycling life of LiMn2O4 was clearly improved by modification of aluminum oxide through the process of heterogeneous nucleation. With the increase of aluminum oxide, the cycling life increases, however, the capacity obviously decreases. The process of heterogeneous nucleation showed some special characters, such as the homogeneous coating. It is more suitable for the surface-modification of LiMn2O4.
2004, 20(08): 795-800
doi: 10.3866/PKU.WHXB20040803
Abstract:
Function of the composite copper coating containing lubricating oil microcapsules was discussed with codeposition mechanism. The oil-containing microcapsules were prepared by a method of simple coacervation in aqueous solution. Lubricating oil and PVA (polyvinyl alcohol) were used as the core and wall materials of microcapsules, respectively. The surface micrograph of the composite copper coating containing oil microcapsules was observed by scan electron microscope. The surface composition was analyzed by dot-scan and line-scan of energy dispersion spectrum. Corrosion resistance of the composite copper coating was evaluated by anodic polarization curve obtained in 0.5 mol•L－1 H2SO4 solution. Wear-resistance of the composite copper was evaluated by the curves of weight lost and sliding friction coefficient during abrasion. Results showed that the microcapsules were contained in the copper coating. The composite copper coating containing the lubricating oil microcapsule had much better corrosion resistance and wear-resistance than the copper coating without microcapsule. In addition, the electrocodeposition mechanism could be explained by a two-step adsorption and an electrochemistry mechanism, which had been used for solid particulate codeposition. The lubricative and repairing function of the oil-containing microcapsule composite copper coating had also been discussed in the paper.
Function of the composite copper coating containing lubricating oil microcapsules was discussed with codeposition mechanism. The oil-containing microcapsules were prepared by a method of simple coacervation in aqueous solution. Lubricating oil and PVA (polyvinyl alcohol) were used as the core and wall materials of microcapsules, respectively. The surface micrograph of the composite copper coating containing oil microcapsules was observed by scan electron microscope. The surface composition was analyzed by dot-scan and line-scan of energy dispersion spectrum. Corrosion resistance of the composite copper coating was evaluated by anodic polarization curve obtained in 0.5 mol•L－1 H2SO4 solution. Wear-resistance of the composite copper was evaluated by the curves of weight lost and sliding friction coefficient during abrasion. Results showed that the microcapsules were contained in the copper coating. The composite copper coating containing the lubricating oil microcapsule had much better corrosion resistance and wear-resistance than the copper coating without microcapsule. In addition, the electrocodeposition mechanism could be explained by a two-step adsorption and an electrochemistry mechanism, which had been used for solid particulate codeposition. The lubricative and repairing function of the oil-containing microcapsule composite copper coating had also been discussed in the paper.
2004, 20(08): 801-805
doi: 10.3866/PKU.WHXB20040804
Abstract:
The kinetics of iridium(III) catalyzed oxidation of isobutyl alcohol by cerium(III) in aqueous sulphuric acid medium has been investigated by titrimetric technique in the temperature range of 25～40 ℃.The reaction order of [Ce(IV)] was found to be unity and that in isobutyl alcohol to be positive fractional. It was found that the pseudo first order ([(CH3)2CHCH2OH] >> [Ce(IV)]) rate constants kobs increases with the increase of [Ir(III)] and [H＋],but decreases with the increase of [HSO4-].Under the protection of nitrogen the reaction system does not induce polymerization of acrylamide indicating no generation of free radicals. Formatoin of a dinuclear complex involving the oxidant, catalyst and the substrate before the rate-determining step has been proposed in the reaction mechanism, and the rate equation derived from the mechanism can explain all experimental observations. From the hydrogensulphate dependence, Ce(SO4)2＋ has been found as the kinetically active species. The pre-equilibrium constants, rate constants of the rate-determining step together with the parameters were evaluated.
The kinetics of iridium(III) catalyzed oxidation of isobutyl alcohol by cerium(III) in aqueous sulphuric acid medium has been investigated by titrimetric technique in the temperature range of 25～40 ℃.The reaction order of [Ce(IV)] was found to be unity and that in isobutyl alcohol to be positive fractional. It was found that the pseudo first order ([(CH3)2CHCH2OH] >> [Ce(IV)]) rate constants kobs increases with the increase of [Ir(III)] and [H＋],but decreases with the increase of [HSO4-].Under the protection of nitrogen the reaction system does not induce polymerization of acrylamide indicating no generation of free radicals. Formatoin of a dinuclear complex involving the oxidant, catalyst and the substrate before the rate-determining step has been proposed in the reaction mechanism, and the rate equation derived from the mechanism can explain all experimental observations. From the hydrogensulphate dependence, Ce(SO4)2＋ has been found as the kinetically active species. The pre-equilibrium constants, rate constants of the rate-determining step together with the parameters were evaluated.
2004, 20(08): 806-810
doi: 10.3866/PKU.WHXB20040805
Abstract:
This paper presents the results of calculations on the first hyperpolarizability and molecular frontier orbital properties of hemicyanine derivatives by the finite-field (FF)/ PM3 method. It is evident that the first hyperpolarizability tensor of hemicyanine derivatives strongly depends on the D-π-A electronic structure of the molecule, but not sensitive to the σ-alkyl chain length. The HOMO-LUMO calculations reveal that the first hyperpolarizability of these derivatives is linearly related to the HOMO-LUMO energy gap ΔEHL.
This paper presents the results of calculations on the first hyperpolarizability and molecular frontier orbital properties of hemicyanine derivatives by the finite-field (FF)/ PM3 method. It is evident that the first hyperpolarizability tensor of hemicyanine derivatives strongly depends on the D-π-A electronic structure of the molecule, but not sensitive to the σ-alkyl chain length. The HOMO-LUMO calculations reveal that the first hyperpolarizability of these derivatives is linearly related to the HOMO-LUMO energy gap ΔEHL.
2004, 20(08): 811-815
doi: 10.3866/PKU.WHXB20040806
Abstract:
The mesoscopic phase separation of block polymers, Pluronic 64(PL64)and Pluronic 25R4 (25R4), was investigated by dissipative particle dynamics(DPD)simulation, and the dynamics process of different aggregates in the solution was simulated. The results showed that: different morphologies were found in solutions of polymer with different concentrations including dispersive phase, spherical micelle, bicontinuous phase and so on. One conclusion is that the DPD simulation can be considered as an adjunct for the experiments, to provide information at the mesoscopic level.
The mesoscopic phase separation of block polymers, Pluronic 64(PL64)and Pluronic 25R4 (25R4), was investigated by dissipative particle dynamics(DPD)simulation, and the dynamics process of different aggregates in the solution was simulated. The results showed that: different morphologies were found in solutions of polymer with different concentrations including dispersive phase, spherical micelle, bicontinuous phase and so on. One conclusion is that the DPD simulation can be considered as an adjunct for the experiments, to provide information at the mesoscopic level.
2004, 20(08): 816-820
doi: 10.3866/PKU.WHXB20040807
Abstract:
In order to investigate the surfactivity of the linear dodecyl polyoxyethylene polyoxypropylene ether series (LSmn), the surface tensions of LS36, LS45 and LS54 have been respectively measured at 298, 303, 313 and 323 K in aqueous solution. Their phase diagrams in water have also been separately made. The critical micelle concentration(cmc) and the corresponding surface tension at such concentration (γcmc) are determined from their γ－lgc curves, which is in the ranges 4.44×10－6～17.3×10－6 mol•L－1 and 30.1～33.5 mN•m－1, respectively. The thermodynamic functions on surface adsorption at cmc and on micellization have also been calculated, in which the adsorption and the micellization free energies (ΔGadΘ and ΔGmΘ) respectively are in the ranges －40.0～－49.5 kJ•mol－1 and －27.2～－33.1 kJ•mol－1 in the studied temperature range. The thermodynamic data show that both the adsorption and the micelliration processes for the studied surfactants are driven by entropy and that LS36 is much different from LS45 and LS54 in many aspects, due to its less component of polyoxyethylene group which has strong hydrophilic capacity in its hydrophilic segment.
In order to investigate the surfactivity of the linear dodecyl polyoxyethylene polyoxypropylene ether series (LSmn), the surface tensions of LS36, LS45 and LS54 have been respectively measured at 298, 303, 313 and 323 K in aqueous solution. Their phase diagrams in water have also been separately made. The critical micelle concentration(cmc) and the corresponding surface tension at such concentration (γcmc) are determined from their γ－lgc curves, which is in the ranges 4.44×10－6～17.3×10－6 mol•L－1 and 30.1～33.5 mN•m－1, respectively. The thermodynamic functions on surface adsorption at cmc and on micellization have also been calculated, in which the adsorption and the micellization free energies (ΔGadΘ and ΔGmΘ) respectively are in the ranges －40.0～－49.5 kJ•mol－1 and －27.2～－33.1 kJ•mol－1 in the studied temperature range. The thermodynamic data show that both the adsorption and the micelliration processes for the studied surfactants are driven by entropy and that LS36 is much different from LS45 and LS54 in many aspects, due to its less component of polyoxyethylene group which has strong hydrophilic capacity in its hydrophilic segment.
2004, 20(08): 821-825
doi: 10.3866/PKU.WHXB20040808
Abstract:
Quantitative structure-activity relationships (QSARs) are essential to optimize the structure to give desired biological activities in drug development. In this paper, a new descriptor, principal component scores vector of structural and topological variables (VSTV), was derived from a principal components analysis of a matrix of 25 structural and topological variables of 20 natural amino acids. Using the method of partial least squares regression, the scales were then applied in QSARs of 58 angiotensin-converting enzyme inhibitors, 12 bactericidal peptides and 20 thromboplastin inhibitors. od results were obtained and the multiple correlation coefficients (R2) and cross-validated R2 (Q2) of three models were 0.789, 0.767; 0.996, 0.879; 0.981, 0.480, respectively.
Quantitative structure-activity relationships (QSARs) are essential to optimize the structure to give desired biological activities in drug development. In this paper, a new descriptor, principal component scores vector of structural and topological variables (VSTV), was derived from a principal components analysis of a matrix of 25 structural and topological variables of 20 natural amino acids. Using the method of partial least squares regression, the scales were then applied in QSARs of 58 angiotensin-converting enzyme inhibitors, 12 bactericidal peptides and 20 thromboplastin inhibitors. od results were obtained and the multiple correlation coefficients (R2) and cross-validated R2 (Q2) of three models were 0.789, 0.767; 0.996, 0.879; 0.981, 0.480, respectively.
2004, 20(08): 826-830
doi: 10.3866/PKU.WHXB20040809
Abstract:
The geometries of reactant, product and transition state for the title reaction have been optimized using density functional theory (DFT) at the B3LYP/6-31G** and B3LYP/6-311＋＋G** levels. The equilibrium states and the transition state have been verified according to the number of imaginary frequency through vibrational analysis. The intrinsic reaction coordinates (IRC) have been traced, along which the changes of energies and geometric parameters have been analyzed. The computed results indicate that the present reaction is a one-step process, with the forward and reverse energy barriers being 192 and 208 kJ•mol－1 at the level of B3LYP/6-31G**, respectively, which means that the reaction might proceed at or above room temperature.
The geometries of reactant, product and transition state for the title reaction have been optimized using density functional theory (DFT) at the B3LYP/6-31G** and B3LYP/6-311＋＋G** levels. The equilibrium states and the transition state have been verified according to the number of imaginary frequency through vibrational analysis. The intrinsic reaction coordinates (IRC) have been traced, along which the changes of energies and geometric parameters have been analyzed. The computed results indicate that the present reaction is a one-step process, with the forward and reverse energy barriers being 192 and 208 kJ•mol－1 at the level of B3LYP/6-31G**, respectively, which means that the reaction might proceed at or above room temperature.
2004, 20(08): 831-836
doi: 10.3866/PKU.WHXB20040810
Abstract:
Sugars are not only biologically important compounds but also typical nonelectrolyte with hydrophilic hydroxyl group, which are capable of hydrogen bonding. D-fructose is an important class of single sugar, and exists in human body with a certain concentration. D-fructose can be absorbed by cells directly. Chemists and biologists pay great attention to it, because of its importance in the research work of biochemistry. In this paper the thermodynamic properties of HCl-NaCl- C6H12O6-H2O system has been studied by EMF measurement in cells without liquid junction from 278.15 to 318.15 K Pt, H2(105 Pa)|HCl(m), C6H12O6 (w), H2O(1－w)|AgCl-Ag (A) Pt, H2(105 Pa)|HCl(mA), NaCl(mB), C6H12O6 (w), H2O(1－w)|AgCl-Ag (B) with the mass fraction of fructose w(C6H12O6)=2.5％、5％ or 7.5％ at a total ionic strength I=1.0000 mol•kg－1. The standard electrode potential of AgCl-Ag in the mixed solvent was determined for cell (A). The standard transfer Gibbs free energies, entropy and enthalpy of HCl from water to mixed solvent were calculated. The activity coefficients of HCl(γA) in the mixed solvent was determined from cell (B). The results show that the activity coefficients of HCl in HCl-NaCl solutions still obeys Harned′s Rule. The primary,secondary and total medium effect of HCl were calculated and discussed.
Sugars are not only biologically important compounds but also typical nonelectrolyte with hydrophilic hydroxyl group, which are capable of hydrogen bonding. D-fructose is an important class of single sugar, and exists in human body with a certain concentration. D-fructose can be absorbed by cells directly. Chemists and biologists pay great attention to it, because of its importance in the research work of biochemistry. In this paper the thermodynamic properties of HCl-NaCl- C6H12O6-H2O system has been studied by EMF measurement in cells without liquid junction from 278.15 to 318.15 K Pt, H2(105 Pa)|HCl(m), C6H12O6 (w), H2O(1－w)|AgCl-Ag (A) Pt, H2(105 Pa)|HCl(mA), NaCl(mB), C6H12O6 (w), H2O(1－w)|AgCl-Ag (B) with the mass fraction of fructose w(C6H12O6)=2.5％、5％ or 7.5％ at a total ionic strength I=1.0000 mol•kg－1. The standard electrode potential of AgCl-Ag in the mixed solvent was determined for cell (A). The standard transfer Gibbs free energies, entropy and enthalpy of HCl from water to mixed solvent were calculated. The activity coefficients of HCl(γA) in the mixed solvent was determined from cell (B). The results show that the activity coefficients of HCl in HCl-NaCl solutions still obeys Harned′s Rule. The primary,secondary and total medium effect of HCl were calculated and discussed.
2004, 20(08): 837-842
doi: 10.3866/PKU.WHXB20040811
Abstract:
The interactions between α-cyclodextrin (α-CD) and 3-alkoxyl-2-hydroxypropyl trimethyl ammonium bromides (CnNBr), new surfactants synthesized in this laboratory, in aqueous solutions have been investigated with titration microcalorimetry at 298.15 K. Stoichiometric ratio of the host-guest complex changes from 1:1 to 2:1 as the number of carbon atoms(n) in hydrophobic chain, CnH2n＋1O, increases from 8 to 14. All the complexes are quite stable with the apparent experiential stability constants beingβ1=1.95×103 dm3•mol－1, β1=2.62×103 dm3•mol－1, β2=3.06×106 dm6•mol－2, β2=13.75×106 dm6•mol－2, respectively for n=7, 8, 12, 14. All the complexation processes are proved to be enthalpy beneficial but entropy unfavorable, and the absolute value of enthalpy changes(ΔHΘ) increases, while entropy change (ΔSΘ) decreases, with the enlarging of the number of methylene in the hydrophobic chain. The results are discussed in the light of hydrophobic interaction of α-CD with CnNBr and the iceberg structure formed by water molecules existing around the hydrophobic tail of surfactant.
The interactions between α-cyclodextrin (α-CD) and 3-alkoxyl-2-hydroxypropyl trimethyl ammonium bromides (CnNBr), new surfactants synthesized in this laboratory, in aqueous solutions have been investigated with titration microcalorimetry at 298.15 K. Stoichiometric ratio of the host-guest complex changes from 1:1 to 2:1 as the number of carbon atoms(n) in hydrophobic chain, CnH2n＋1O, increases from 8 to 14. All the complexes are quite stable with the apparent experiential stability constants beingβ1=1.95×103 dm3•mol－1, β1=2.62×103 dm3•mol－1, β2=3.06×106 dm6•mol－2, β2=13.75×106 dm6•mol－2, respectively for n=7, 8, 12, 14. All the complexation processes are proved to be enthalpy beneficial but entropy unfavorable, and the absolute value of enthalpy changes(ΔHΘ) increases, while entropy change (ΔSΘ) decreases, with the enlarging of the number of methylene in the hydrophobic chain. The results are discussed in the light of hydrophobic interaction of α-CD with CnNBr and the iceberg structure formed by water molecules existing around the hydrophobic tail of surfactant.
2004, 20(08): 843-848
doi: 10.3866/PKU.WHXB20040812
Abstract:
A mixed-ligand complex Ni(mnt)(bipyO2) with large conjugate system was synthesized by reaction of bipyO2(2,2′-bipyridine-1,1′-dioxide),mnt2－(maleonitriledithiolate) and NiCl2. The determinations of elemental analysis, IR, UV, molar conductivity and TG-DTA showed the complex to have electroneutrality and a square planar structure. It is a thermostable brown solid under temperature 335 ℃. The ultraviolet absorption spectra of the complex in DMSO solution exhibited intensive absorption bands at 255～290 nm(π-π* in bipyO2 and mnt), 310～340 nm(n-π*, metel cation to ligands), 370～420 nm(π-π* in mnt) and 440～520 nm, and the latter was assigned as a large conjugate system interlocking metal ion and ligands π to π* transition. The study of sensitive properties showed the complex to be a od sensitive material of ammonia. The sensor manufactured using the complex has a od sensitivity and selectivity to ammonia. When working voltage is 10 V and NH3 concentration is less than 2.6 mmol•L－1. The output voltage of the sensor varied linearly in response to the change of NH3 concentration (Fig.3). The average recovery rate of the sensor is 100.2％(Table 4). The responsive time is about 20 s, and the return time is about 45 s. The sensor could be used in quantitative analysis of trace ammonia.
A mixed-ligand complex Ni(mnt)(bipyO2) with large conjugate system was synthesized by reaction of bipyO2(2,2′-bipyridine-1,1′-dioxide),mnt2－(maleonitriledithiolate) and NiCl2. The determinations of elemental analysis, IR, UV, molar conductivity and TG-DTA showed the complex to have electroneutrality and a square planar structure. It is a thermostable brown solid under temperature 335 ℃. The ultraviolet absorption spectra of the complex in DMSO solution exhibited intensive absorption bands at 255～290 nm(π-π* in bipyO2 and mnt), 310～340 nm(n-π*, metel cation to ligands), 370～420 nm(π-π* in mnt) and 440～520 nm, and the latter was assigned as a large conjugate system interlocking metal ion and ligands π to π* transition. The study of sensitive properties showed the complex to be a od sensitive material of ammonia. The sensor manufactured using the complex has a od sensitivity and selectivity to ammonia. When working voltage is 10 V and NH3 concentration is less than 2.6 mmol•L－1. The output voltage of the sensor varied linearly in response to the change of NH3 concentration (Fig.3). The average recovery rate of the sensor is 100.2％(Table 4). The responsive time is about 20 s, and the return time is about 45 s. The sensor could be used in quantitative analysis of trace ammonia.
2004, 20(08): 849-853
doi: 10.3866/PKU.WHXB20040813
Abstract:
The photoelectrochemical behaviors of the TiO2 nanocrystalline electrode sensitized by Cy5 (N-carboxylbenzyl-3,3-dimethyl-3H-indole squarylium cyanine dye)were reported. The sensitized conditions were optimized. The ground state level and the excited state level of the dye were determined by using the cyclic voltammetry and the optical absorption spectroscopy. The results show that the excited state level of this dye matches the conduction band edge of TiO2 nanoparticles. Therefore the sensitization of the dye can obviously increase the photocurrent density of TiO2 nanocrystalline electrode and results in a red-shift of optical absorption from the ultra-violet region to the visible and near infra-red region. As a result, the light-to-electricity conversion efficiency was greatly improved and the maximum value of IPCE reached 46.4％ and η was 1.70％ when the TiO2 nanostructured porous film was 6.5μm thick and was sensitized for 6 h.
The photoelectrochemical behaviors of the TiO2 nanocrystalline electrode sensitized by Cy5 (N-carboxylbenzyl-3,3-dimethyl-3H-indole squarylium cyanine dye)were reported. The sensitized conditions were optimized. The ground state level and the excited state level of the dye were determined by using the cyclic voltammetry and the optical absorption spectroscopy. The results show that the excited state level of this dye matches the conduction band edge of TiO2 nanoparticles. Therefore the sensitization of the dye can obviously increase the photocurrent density of TiO2 nanocrystalline electrode and results in a red-shift of optical absorption from the ultra-violet region to the visible and near infra-red region. As a result, the light-to-electricity conversion efficiency was greatly improved and the maximum value of IPCE reached 46.4％ and η was 1.70％ when the TiO2 nanostructured porous film was 6.5μm thick and was sensitized for 6 h.
2004, 20(08): 854-859
doi: 10.3866/PKU.WHXB20040814
Abstract:
ZSM-5/Y composite zeolite, a new composite material synthesized in situ from NaY gel, was dealuminated by hydrothermal treatment to study the effect of dealumination on physicochemical properties (undertook with XRD, IR spectroscopy, N2 adsorption/desorption) and catalytic activity (in n-hexane cracking). Compared to the mechanical mixtures, Y phases of the composites had better retained crystallinity under steaming at 550 ℃ and 700 ℃.Steaming resulted in the loss of microporosity of the crystalline material but the increase of mesoporous structure (5～30 nm at 550 ℃ and 5～40 nm at 700 ℃).The size of the mesopore distribution of dealuminated composites was larger than the dealuminated mechanical mixtures, but their macro- and mesopore volume was smaller. Quantitative IR studies of pyridine sorption showed Brønsted and Lewis acid sites of the composite after dealuminated at 550 ℃ decreased (mainly the medium strength acid sites).Compared to the hydrogen type zeolite, the catalytic activity of the dealuminated zeolite for n-hexane cracking increased greatly after 550 ℃ dealumination, and then decreased by further dealumination. The analysis of the product distribution showed that the enhanced activity was related to the change of reaction mechanism.
ZSM-5/Y composite zeolite, a new composite material synthesized in situ from NaY gel, was dealuminated by hydrothermal treatment to study the effect of dealumination on physicochemical properties (undertook with XRD, IR spectroscopy, N2 adsorption/desorption) and catalytic activity (in n-hexane cracking). Compared to the mechanical mixtures, Y phases of the composites had better retained crystallinity under steaming at 550 ℃ and 700 ℃.Steaming resulted in the loss of microporosity of the crystalline material but the increase of mesoporous structure (5～30 nm at 550 ℃ and 5～40 nm at 700 ℃).The size of the mesopore distribution of dealuminated composites was larger than the dealuminated mechanical mixtures, but their macro- and mesopore volume was smaller. Quantitative IR studies of pyridine sorption showed Brønsted and Lewis acid sites of the composite after dealuminated at 550 ℃ decreased (mainly the medium strength acid sites).Compared to the hydrogen type zeolite, the catalytic activity of the dealuminated zeolite for n-hexane cracking increased greatly after 550 ℃ dealumination, and then decreased by further dealumination. The analysis of the product distribution showed that the enhanced activity was related to the change of reaction mechanism.
2004, 20(08): 860-863
doi: 10.3866/PKU.WHXB20040815
Abstract:
The electronic states of InI molecule are computed using the coupled-cluster single- and double-linear response theory (CCSD-LRT) based on the relativistic effective core potential basis sets. The spectroscopic constants of the 12 valence states and 4 bound Rydberg states, including the excitation energy (Te), the equilibrium bond distance (Re), and the vibrational constants (ωe and ωeχe), are obtained. Meanwhile, we obtain potential energy curves (PECs) of the electronic states. The results match well with the experimental data. There are some states with shallow potential wells at about 33 000 cm－1 above the 1Π state. The observed continuous absorption band system at about 31 500 cm－1 can be contributed to the transitions from these states and the 1Π state to the ground state.
The electronic states of InI molecule are computed using the coupled-cluster single- and double-linear response theory (CCSD-LRT) based on the relativistic effective core potential basis sets. The spectroscopic constants of the 12 valence states and 4 bound Rydberg states, including the excitation energy (Te), the equilibrium bond distance (Re), and the vibrational constants (ωe and ωeχe), are obtained. Meanwhile, we obtain potential energy curves (PECs) of the electronic states. The results match well with the experimental data. There are some states with shallow potential wells at about 33 000 cm－1 above the 1Π state. The observed continuous absorption band system at about 31 500 cm－1 can be contributed to the transitions from these states and the 1Π state to the ground state.
2004, 20(08): 864-867
doi: 10.3866/PKU.WHXB20040816
Abstract:
The binding reaction between ofloxacin and bovine lactoferrin(BLf) was studied by fluorescence spectra in dilute aqueous solution. The binding constant K was found to be 9.4×104 L•mol－1 and the binding sits n to be 2.43 by fluorescence quenching method. The binding distance (r=2.93 nm) and energy-transfer efficiency (E=0.253) between ofloxacin and bovine lactoferrin were also obtained according to the mechanism of Förster-type dipole-dipole nonradiative energy-transfer. The effect of ofloxacin on the conformation of bovine lactoferrin was also analyzed using synchronous fluorescence spectroscopy. The interaction between ofloxacin and bovine lactoferrin is quite strong. Ofloxacin can effect the conformation of bovine lactoferrin in some degree.
The binding reaction between ofloxacin and bovine lactoferrin(BLf) was studied by fluorescence spectra in dilute aqueous solution. The binding constant K was found to be 9.4×104 L•mol－1 and the binding sits n to be 2.43 by fluorescence quenching method. The binding distance (r=2.93 nm) and energy-transfer efficiency (E=0.253) between ofloxacin and bovine lactoferrin were also obtained according to the mechanism of Förster-type dipole-dipole nonradiative energy-transfer. The effect of ofloxacin on the conformation of bovine lactoferrin was also analyzed using synchronous fluorescence spectroscopy. The interaction between ofloxacin and bovine lactoferrin is quite strong. Ofloxacin can effect the conformation of bovine lactoferrin in some degree.
2004, 20(08): 868-870
doi: 10.3866/PKU.WHXB20040817
Abstract:
This paper investigated a method of modifying potassium titanate whiskers (K2O•6TiO2) to obtain polymethyl methacrylate (PMMA)/K2O•6TiO2 composite particles through emulsion polymerization. The interface properties of pure and modified potassium titanate whiskers were studied in details. According to the characterizations of FT-IR、 SEM and EDS, the surface of the potassium titanate whiskers was covered by PMMA molecules and the composite particles have a core-shell structure. The characterization of surface energy and interfacial tension showed that the interface property of modified whiskers has changed thoroughly and it was similar to that of PMMA, so the whiskers were covered by PMMA thoroughly. It made the potassium titanate whiskers modified from hydrophilic to hydrophobic and the dispersibility of the whiskers in organic liquids improved greatly.
This paper investigated a method of modifying potassium titanate whiskers (K2O•6TiO2) to obtain polymethyl methacrylate (PMMA)/K2O•6TiO2 composite particles through emulsion polymerization. The interface properties of pure and modified potassium titanate whiskers were studied in details. According to the characterizations of FT-IR、 SEM and EDS, the surface of the potassium titanate whiskers was covered by PMMA molecules and the composite particles have a core-shell structure. The characterization of surface energy and interfacial tension showed that the interface property of modified whiskers has changed thoroughly and it was similar to that of PMMA, so the whiskers were covered by PMMA thoroughly. It made the potassium titanate whiskers modified from hydrophilic to hydrophobic and the dispersibility of the whiskers in organic liquids improved greatly.
2004, 20(08): 871-876
doi: 10.3866/PKU.WHXB20040818
Abstract:
A novel lead dioxide anode modified by fluorine and characterized by X-ray diffraction (XRD) and SEM, was applied to the organic degradation by using phenolic compounds as model pollutants. It was found that this anode showed od resistance to corrosion, perfect electrocatalytic activity and stability, indicating potential for future environmental application. Further, the degradation of organics was confirmed to be mainly of the hydroxyl radical mechanism by using isopropanol as radical scavenger, hence, such an oxidation process is essentially an advanced electrochemical oxidation process (AEOPs).
A novel lead dioxide anode modified by fluorine and characterized by X-ray diffraction (XRD) and SEM, was applied to the organic degradation by using phenolic compounds as model pollutants. It was found that this anode showed od resistance to corrosion, perfect electrocatalytic activity and stability, indicating potential for future environmental application. Further, the degradation of organics was confirmed to be mainly of the hydroxyl radical mechanism by using isopropanol as radical scavenger, hence, such an oxidation process is essentially an advanced electrochemical oxidation process (AEOPs).
2004, 20(08): 877-881
doi: 10.3866/PKU.WHXB20040819
Abstract:
The excited potential surface of H2O＋ is calculated using CASSCF method with Gaussian98 program, and then fitted to an analytical expression. At the same time, the selections of the complete active space (CAS) and the basis sets are discussed during CASSCF calculation. The potential surface obtained agrees very well with the result from MRD-CI method.
The excited potential surface of H2O＋ is calculated using CASSCF method with Gaussian98 program, and then fitted to an analytical expression. At the same time, the selections of the complete active space (CAS) and the basis sets are discussed during CASSCF calculation. The potential surface obtained agrees very well with the result from MRD-CI method.
2004, 20(08): 882-886
doi: 10.3866/PKU.WHXB20040820
Abstract:
Interphases at the adhesion bonded interfaces between aluminum sheet and polypropylene(PP)/and PP blended with maleic anhydride grafted polypropylene(PP-g-MAH) were studied by X-ray photoelectron spectroscopy (XPS), and a mechanism of coordination bonding at the interfaces was proposed. Compared to PP, for PP with addition of PP-g-MAH the spectra of Al 2p and O 1s at the surface of aluminum sheet shift to higher binding energy obviously, which indicates that chemical interaction between PP-g-MAH and surface of the aluminum sheet occurs, and as a result Al－O－C bond is formed. There is no chemical interaction between PP and surface of the aluminum sheet. The obvious improvement of the adhesion strength between aluminum sheet and PP with PP-g-MAH could be attributed to the formation of Al－O－C bonds.
Interphases at the adhesion bonded interfaces between aluminum sheet and polypropylene(PP)/and PP blended with maleic anhydride grafted polypropylene(PP-g-MAH) were studied by X-ray photoelectron spectroscopy (XPS), and a mechanism of coordination bonding at the interfaces was proposed. Compared to PP, for PP with addition of PP-g-MAH the spectra of Al 2p and O 1s at the surface of aluminum sheet shift to higher binding energy obviously, which indicates that chemical interaction between PP-g-MAH and surface of the aluminum sheet occurs, and as a result Al－O－C bond is formed. There is no chemical interaction between PP and surface of the aluminum sheet. The obvious improvement of the adhesion strength between aluminum sheet and PP with PP-g-MAH could be attributed to the formation of Al－O－C bonds.
2004, 20(08): 887-891
doi: 10.3866/PKU.WHXB20040821
Abstract:
The interaction of La3＋ or Eu3＋ with MP-8 was studied and the interaction strength of La3＋ or Eu3＋ with MP-8 was compared. Comparing with the UV-Vis absorption spectrum of the MP-8 solution without La3＋ or Eu3＋,the position of the Soret band for the MP-8 solution with La3＋ or Eu3＋ shifts to the red direction and the absorbance decreases. The extents of the red shift of the band position and the decrease in the absorbance for Eu3＋ in the solutions without or with NaCl are larger than that for La3＋. In 0.10 mol•L－1 NaCl solution, La3＋ or Eu3＋ could completely coordinate with carboxylate oxygen of two propionic acid groups of the heme group in an MP-8 molecule when the molar ratio of La3＋ or Eu3＋ and MP-8 is 10 and 5, respectively. In addition, the cyclic voltammetric results showed that the redox peak area of Eu3＋ decreased 20％ after adding MP-8 into the solution. These results clearly illustrated that one La3＋ or Eu3＋ ion would coordinate strongly with carboxylate oxygen of two propionic acid groups of the heme group in an MP-8 molecule and the excessive La3＋ or Eu3＋ ions weakly interact with the carboxylate oxygen in the peptide chain. The interaction between Eu3＋ and MP-8 is stronger than that between La3＋ and MP-8.
The interaction of La3＋ or Eu3＋ with MP-8 was studied and the interaction strength of La3＋ or Eu3＋ with MP-8 was compared. Comparing with the UV-Vis absorption spectrum of the MP-8 solution without La3＋ or Eu3＋,the position of the Soret band for the MP-8 solution with La3＋ or Eu3＋ shifts to the red direction and the absorbance decreases. The extents of the red shift of the band position and the decrease in the absorbance for Eu3＋ in the solutions without or with NaCl are larger than that for La3＋. In 0.10 mol•L－1 NaCl solution, La3＋ or Eu3＋ could completely coordinate with carboxylate oxygen of two propionic acid groups of the heme group in an MP-8 molecule when the molar ratio of La3＋ or Eu3＋ and MP-8 is 10 and 5, respectively. In addition, the cyclic voltammetric results showed that the redox peak area of Eu3＋ decreased 20％ after adding MP-8 into the solution. These results clearly illustrated that one La3＋ or Eu3＋ ion would coordinate strongly with carboxylate oxygen of two propionic acid groups of the heme group in an MP-8 molecule and the excessive La3＋ or Eu3＋ ions weakly interact with the carboxylate oxygen in the peptide chain. The interaction between Eu3＋ and MP-8 is stronger than that between La3＋ and MP-8.
2004, 20(08): 892-896
doi: 10.3866/PKU.WHXB20040822
Abstract:
The growth of perylene on Ag (110) has been studied by the ultraviolet photoemission spectroscopy (UPS) measurements and the low-energy electron diffraction (LEED).Four emission features from perylene are located at 3.5,4.8,6.4 and 8.5 eV below the Fermi level respectively. An ordered structure of C(6×2) can be observed when the organic film is about one monolayer (0.3 nm thickness). The angle-resolved ultraviolet photoemission spectroscopy (ARUPS) measurements show that the molecules of perylene near the interface are parallel to the substrate. The desorption of the organic material occurs with warming the substrate, but the perylene molecules are stable on Ag(110) surface, no decomposition is observed below 140 ℃.
The growth of perylene on Ag (110) has been studied by the ultraviolet photoemission spectroscopy (UPS) measurements and the low-energy electron diffraction (LEED).Four emission features from perylene are located at 3.5,4.8,6.4 and 8.5 eV below the Fermi level respectively. An ordered structure of C(6×2) can be observed when the organic film is about one monolayer (0.3 nm thickness). The angle-resolved ultraviolet photoemission spectroscopy (ARUPS) measurements show that the molecules of perylene near the interface are parallel to the substrate. The desorption of the organic material occurs with warming the substrate, but the perylene molecules are stable on Ag(110) surface, no decomposition is observed below 140 ℃.
