Login In
2005 Volume 21 Issue 11
2005, 21(11): 1195-1197
doi: 10.3866/PKU.WHXB20051101
Abstract:
On a flowing afterglow apparatus, the quenching of SO(c1Σ－) by SO2, O2, CO2, N2, He, CS2, CH3OH, C2H5OH, C3H7OH, C4H9OH, CH3COCH3, C6H6, CH2Cl2, CH2Br2, CHCl3, or CCl4 was studied firstly and successfully. The quenching rate constants of SO(c1Σ－) by them were measured. By analysis, it demonstrates that the quenching rate constants of SO(c1Σ－) by the alkanol molecules, CnH2n+1OH(n=1, 2, 3, 4), are semi-proportional to the number of C—H bond in them; the quenching by the non-polar small molecules, such as CO2 and N2 is not efficient; while it is obvious by SO2 because of its strong polarity. The size and volume of halogen atoms in the halomethane molecules play an important role in quenching SO(c1Σ－), and it seems that there is no evident correlation between the quenching rate constants and the number of the chlorine atom in the chlomethane molecules.
On a flowing afterglow apparatus, the quenching of SO(c1Σ－) by SO2, O2, CO2, N2, He, CS2, CH3OH, C2H5OH, C3H7OH, C4H9OH, CH3COCH3, C6H6, CH2Cl2, CH2Br2, CHCl3, or CCl4 was studied firstly and successfully. The quenching rate constants of SO(c1Σ－) by them were measured. By analysis, it demonstrates that the quenching rate constants of SO(c1Σ－) by the alkanol molecules, CnH2n+1OH(n=1, 2, 3, 4), are semi-proportional to the number of C—H bond in them; the quenching by the non-polar small molecules, such as CO2 and N2 is not efficient; while it is obvious by SO2 because of its strong polarity. The size and volume of halogen atoms in the halomethane molecules play an important role in quenching SO(c1Σ－), and it seems that there is no evident correlation between the quenching rate constants and the number of the chlorine atom in the chlomethane molecules.
2005, 21(11): 1198-1204
doi: 10.3866/PKU.WHXB20051102
Abstract:
The interactions between three kinds of water-soluble polymers, i.e. polyacrylic acid (PAA), polymethylacrylic acid (PMAA), and acrylic acid-methyl acrylate copolymer (AA-MA), and calcite crystal have been simulated by molecular dynamics (MD). The results show that the orders of binding energies for three polymers with two calcite crystal surfaces are PAA ＞ AA-MA ＞ PMAA, and the interactions of polymers with calcite (1 0) face are significantly stronger than those with (104) face. The binding energies are mainly determined by coulomb interaction by analysis various interactions and the pair correlation functions of the systems. Polymers deform during their combining with calcite crystal surfaces, and the deformation energies of polymers on (1 0) face are about 2 times as those on (104) face, but all of them are far lower than respective nonbonding energies. The dynamics behaviors of carboxyls at different positions of polymer chains are widely different. Carboxyls at the end of chains oscillate more rapidly than those in the middle, so the middle ones hinder scale crystal growth more effectively than the end segments because they combine with calcite crystal more firmly.
The interactions between three kinds of water-soluble polymers, i.e. polyacrylic acid (PAA), polymethylacrylic acid (PMAA), and acrylic acid-methyl acrylate copolymer (AA-MA), and calcite crystal have been simulated by molecular dynamics (MD). The results show that the orders of binding energies for three polymers with two calcite crystal surfaces are PAA ＞ AA-MA ＞ PMAA, and the interactions of polymers with calcite (1 0) face are significantly stronger than those with (104) face. The binding energies are mainly determined by coulomb interaction by analysis various interactions and the pair correlation functions of the systems. Polymers deform during their combining with calcite crystal surfaces, and the deformation energies of polymers on (1 0) face are about 2 times as those on (104) face, but all of them are far lower than respective nonbonding energies. The dynamics behaviors of carboxyls at different positions of polymer chains are widely different. Carboxyls at the end of chains oscillate more rapidly than those in the middle, so the middle ones hinder scale crystal growth more effectively than the end segments because they combine with calcite crystal more firmly.
2005, 21(11): 1205-1210
doi: 10.3866/PKU.WHXB20051103
Abstract:
The interfacial dilational viscoelastic properties of hydrophobically associating block copolymer composed of acrylamide (AM) and a low amount of 2-ethylhexyl acrylate (EHA) (＜ 1.0% mole fraction) with a hydrolysis degree of about 1.5%～2.0% at the octane-water interfaces were investigated by interfacial tension relaxation method. The influences of anionic surfactant sodium dodecyl sulfate (SDS), cationic surfactant cetyl trimethylammonium bromide (CTAB) and nonionic surfactant Triton X-100 on the dilational viscoelastic properties of 7 g•L-1 polymer solutions were studied. The results showed that surfactants can influence the dilational properties of polymer solutions by providing a new fast relaxation process involving the exchange of surfactant molecules between monomers and mixed micelles at interface. By adding SDS, this new process is so fast that its characteristic time can′t be obtained. However, for Triton X-100, which has a relative higher molecular weight, the characteristic time was about 0.9 s. By adding CTAB, the slow process changed obviously due to the strong electrostatic interaction between oppositely charged surfactant and hydrolyzed part of polymer chain.
The interfacial dilational viscoelastic properties of hydrophobically associating block copolymer composed of acrylamide (AM) and a low amount of 2-ethylhexyl acrylate (EHA) (＜ 1.0% mole fraction) with a hydrolysis degree of about 1.5%～2.0% at the octane-water interfaces were investigated by interfacial tension relaxation method. The influences of anionic surfactant sodium dodecyl sulfate (SDS), cationic surfactant cetyl trimethylammonium bromide (CTAB) and nonionic surfactant Triton X-100 on the dilational viscoelastic properties of 7 g•L-1 polymer solutions were studied. The results showed that surfactants can influence the dilational properties of polymer solutions by providing a new fast relaxation process involving the exchange of surfactant molecules between monomers and mixed micelles at interface. By adding SDS, this new process is so fast that its characteristic time can′t be obtained. However, for Triton X-100, which has a relative higher molecular weight, the characteristic time was about 0.9 s. By adding CTAB, the slow process changed obviously due to the strong electrostatic interaction between oppositely charged surfactant and hydrolyzed part of polymer chain.
2005, 21(11): 1211-1216
doi: 10.3866/PKU.WHXB20051104
Abstract:
Adsorption of benzoic acid and benzene from cyclohexane solution by silica gel was studied under 293~313 K. It was indicated that adsorption of benzoic acid by silica gel well fit the stoichiometric displacement mode for adsorption (SDM-A). But for benzene, when treated with SDM-A there was a turning point in its adsorption isotherm, which corresponding to the dividing point between monomolecular and multimolecular layer adsorption. Thermodynamics formulae of adsorption were also set up based on SDM-A. It was demonstrated that benzoic acid was spontaneously adsorbed by silica gel accompanied with an entropy increase process, but for benzene it was accompanied with an entropy decrease process. The free energy change for adsorption of benzoic acid was larger than that of benzene and the adsorption enthalpy change was reversed because of the stronger affinity to silica gel and the stronger solvophobic ability for benzoic acid than that for benzene.
Adsorption of benzoic acid and benzene from cyclohexane solution by silica gel was studied under 293~313 K. It was indicated that adsorption of benzoic acid by silica gel well fit the stoichiometric displacement mode for adsorption (SDM-A). But for benzene, when treated with SDM-A there was a turning point in its adsorption isotherm, which corresponding to the dividing point between monomolecular and multimolecular layer adsorption. Thermodynamics formulae of adsorption were also set up based on SDM-A. It was demonstrated that benzoic acid was spontaneously adsorbed by silica gel accompanied with an entropy increase process, but for benzene it was accompanied with an entropy decrease process. The free energy change for adsorption of benzoic acid was larger than that of benzene and the adsorption enthalpy change was reversed because of the stronger affinity to silica gel and the stronger solvophobic ability for benzoic acid than that for benzene.
2005, 21(11): 1217-1222
doi: 10.3866/PKU.WHXB20051105
Abstract:
Gemini surfactants, with two quaternary ammonium head groups separated by a spacer with variable configurations and with each head group attached to a same or different hydrophobic tail, can be used to control the packing parameter and the organic polycharge centers. By this means, the structure of mesoporous material prepared using surfactant template can be considerably controlled by changing the structures of Gemini surfactant, especially the characteristics of the spacer. The flexibility and the hydrophilicity of the spacer can be changed by varying the length of methylene chain of spacers from 3C to 12C, or adopting phenyl and hydroxyl radicals. These deduced successful synthesis of series of ordered mesoporous structure. When the length of methylene spacer chain of template was between 4C~8C, hexa nal mesoporous materials were produced, while cubic mesoporous materials were obtained when the length of spacer chain was 10C~12C. It is shown that the GEM16-6-16 and GEM16-12-16 were effective templates for highly ordered MCM-41 and MCM-48 respectively. The GEM16- 3(OH)-16, which introduced a hydrophilic flexible hydroxyl radical to the spacer, produced less ordered sandwich structure. The GEM16-(1-Ar-1)-16, with a hydrophobic rigid spacer of p-xylyl, was hard to dissolved in water. When ethanol was used as cosolvent, hollow sphere materials were produced. The samples were characterized by XRD, TEM, and N2 adsorption-desorpotion.
Gemini surfactants, with two quaternary ammonium head groups separated by a spacer with variable configurations and with each head group attached to a same or different hydrophobic tail, can be used to control the packing parameter and the organic polycharge centers. By this means, the structure of mesoporous material prepared using surfactant template can be considerably controlled by changing the structures of Gemini surfactant, especially the characteristics of the spacer. The flexibility and the hydrophilicity of the spacer can be changed by varying the length of methylene chain of spacers from 3C to 12C, or adopting phenyl and hydroxyl radicals. These deduced successful synthesis of series of ordered mesoporous structure. When the length of methylene spacer chain of template was between 4C~8C, hexa nal mesoporous materials were produced, while cubic mesoporous materials were obtained when the length of spacer chain was 10C~12C. It is shown that the GEM16-6-16 and GEM16-12-16 were effective templates for highly ordered MCM-41 and MCM-48 respectively. The GEM16- 3(OH)-16, which introduced a hydrophilic flexible hydroxyl radical to the spacer, produced less ordered sandwich structure. The GEM16-(1-Ar-1)-16, with a hydrophobic rigid spacer of p-xylyl, was hard to dissolved in water. When ethanol was used as cosolvent, hollow sphere materials were produced. The samples were characterized by XRD, TEM, and N2 adsorption-desorpotion.
2005, 21(11): 1223-1228
doi: 10.3866/PKU.WHXB20051106
Abstract:
The unity bond index-quadratic exponential potential (UBI-QEP) model is used to evaluate the heat of chemisorption of adsorbed species and activation barriers for the elementary reactions in the mechanisms for Fischer-Tropsch synthesis (FTS) reaction over a model catalyst Co(0001), including carbide mechanism, hydroxycarbene mechanism, and CO insertion mechanism. It is demonstrated that the reaction pathway for the formation of hydrocarbons proposed in the carbide mechanism is energetically favorable. The insertion of CO is the pathway for the formation of oxygenations. Dissociation of adsorbed CO and hydrogenation of Cads have higher activation barriers than other elementary steps in the reaction pathway. The energetically preferred pathway to initiate the carbon chain growth is via insertion of CH2, ads intermediate into the carbon-metal bond of CH3, ads or CH2, ads group. The activation barrier for termination of carbon chain propagation by β-H elimination is lower than hydrogenation. The olefins and oxygenates in the primary products during FTS are apt to conduct the secondary reaction via readsorption on the catalyst surface because of its low active energies. Compared with Fe/W(110), the activation barriers for CHx, ads hydrogenations and CH2, ads insertion are lower on Co(0001), which results in higher selectivity of methane and more yield of heavy hydrocarbons.
The unity bond index-quadratic exponential potential (UBI-QEP) model is used to evaluate the heat of chemisorption of adsorbed species and activation barriers for the elementary reactions in the mechanisms for Fischer-Tropsch synthesis (FTS) reaction over a model catalyst Co(0001), including carbide mechanism, hydroxycarbene mechanism, and CO insertion mechanism. It is demonstrated that the reaction pathway for the formation of hydrocarbons proposed in the carbide mechanism is energetically favorable. The insertion of CO is the pathway for the formation of oxygenations. Dissociation of adsorbed CO and hydrogenation of Cads have higher activation barriers than other elementary steps in the reaction pathway. The energetically preferred pathway to initiate the carbon chain growth is via insertion of CH2, ads intermediate into the carbon-metal bond of CH3, ads or CH2, ads group. The activation barrier for termination of carbon chain propagation by β-H elimination is lower than hydrogenation. The olefins and oxygenates in the primary products during FTS are apt to conduct the secondary reaction via readsorption on the catalyst surface because of its low active energies. Compared with Fe/W(110), the activation barriers for CHx, ads hydrogenations and CH2, ads insertion are lower on Co(0001), which results in higher selectivity of methane and more yield of heavy hydrocarbons.
2005, 21(11): 1229-1234
doi: 10.3866/PKU.WHXB20051107
Abstract:
The binding mode of a series of dicaffeoyl or digalloyl pyrrolidine and furan derivatives inhibitors with HIV-1 integrase was proposed by using molecular docking and molecular dynamics (MD) simulation methods. The results indicate that the interactions between HIV-1 integrase conserved DDE motif and caffeoyl or galloyl group of inhibitors play a critical role in the inhibition of integrase activity, and the binding affinity between integrase and inhibitors was improved when the side chain groups were galloyls. The linear interaction energy (LIE) method was used to calculate the binding free energies of HIV-1 integrase and their inhibitors, the predicted values are in od agreement with the experimental data, with a root-mean-square deviation (RMSD) of 1.39 kJ•mol-1. The above results provide useful information for structure-based HIV-1 integrase inhibitor design.
The binding mode of a series of dicaffeoyl or digalloyl pyrrolidine and furan derivatives inhibitors with HIV-1 integrase was proposed by using molecular docking and molecular dynamics (MD) simulation methods. The results indicate that the interactions between HIV-1 integrase conserved DDE motif and caffeoyl or galloyl group of inhibitors play a critical role in the inhibition of integrase activity, and the binding affinity between integrase and inhibitors was improved when the side chain groups were galloyls. The linear interaction energy (LIE) method was used to calculate the binding free energies of HIV-1 integrase and their inhibitors, the predicted values are in od agreement with the experimental data, with a root-mean-square deviation (RMSD) of 1.39 kJ•mol-1. The above results provide useful information for structure-based HIV-1 integrase inhibitor design.
2005, 21(11): 1235-1239
doi: 10.3866/PKU.WHXB20051108
Abstract:
The electrochemical characteristic of NiCl2(bpy)3 at glassy carbon electrode in DMF has been investigated by using cyclic voltammetry. Chronocoulometry was employed to determine the diffusion coefficients and the rate constants (kf and k0). The CV results imply that the redox reaction of NiCl2(bpy)3 at glassy carbon electrode is quasi-reversible. The diffusion coefficient increased with the increase of temperature between 302.15 K and 334.15 K. The forward rate constants (kf) at different potentials and standard rate constants (k0) at different temperatures were also obtained by analysis of charge-time data. According to the slope of lnk0 against T-1, the activation energy (Ea) of the electron transfer was 14.4 kJ•mol-1.
The electrochemical characteristic of NiCl2(bpy)3 at glassy carbon electrode in DMF has been investigated by using cyclic voltammetry. Chronocoulometry was employed to determine the diffusion coefficients and the rate constants (kf and k0). The CV results imply that the redox reaction of NiCl2(bpy)3 at glassy carbon electrode is quasi-reversible. The diffusion coefficient increased with the increase of temperature between 302.15 K and 334.15 K. The forward rate constants (kf) at different potentials and standard rate constants (k0) at different temperatures were also obtained by analysis of charge-time data. According to the slope of lnk0 against T-1, the activation energy (Ea) of the electron transfer was 14.4 kJ•mol-1.
2005, 21(11): 1240-1243
doi: 10.3866/PKU.WHXB20051109
Abstract:
By using drop-volume method, the surface tension of disodium hexadecyl diphenyl ether disulfonate (C16-MADS) was measured in different NaCl concentrations (0～0.50 mol•L-1 NaCl) at different temperatures (298.0～318.0 K). The results show that with the increase of temperature, the critical micelle concentration (cmc) of C16-MADS slightly increases, but the maximum surface excess concentration at the air/water interface (Γ∞) decreases. The cmc of C16-MADS decreases from 1.45×10-4 mol•L-1 down to 4.10×10-5 mol•L-1 as the concentration of NaCl increases from 0 to 0.50 mol•L-1, but the corresponding surface tension at the concentration (γcmc) shows no variation. As the increase of NaCl concentration, Γ∞ of C16-MADS increases as the increase of temperature in the range of 298.0～303.0 K, but abnormally decreases from 2.27 μmol•m-2 down to 1.41 μmol•m-2 in the range of 308.0～318.0 K. The micellization free energies (ΔGm0) are in the range －63.98～－76.20 kJ•mol-1 in the studied ranges of temperature and NaCl concentration. The process of micellization of C16-MADS in aqueous solution is mainly driven by the entropy.
By using drop-volume method, the surface tension of disodium hexadecyl diphenyl ether disulfonate (C16-MADS) was measured in different NaCl concentrations (0～0.50 mol•L-1 NaCl) at different temperatures (298.0～318.0 K). The results show that with the increase of temperature, the critical micelle concentration (cmc) of C16-MADS slightly increases, but the maximum surface excess concentration at the air/water interface (Γ∞) decreases. The cmc of C16-MADS decreases from 1.45×10-4 mol•L-1 down to 4.10×10-5 mol•L-1 as the concentration of NaCl increases from 0 to 0.50 mol•L-1, but the corresponding surface tension at the concentration (γcmc) shows no variation. As the increase of NaCl concentration, Γ∞ of C16-MADS increases as the increase of temperature in the range of 298.0～303.0 K, but abnormally decreases from 2.27 μmol•m-2 down to 1.41 μmol•m-2 in the range of 308.0～318.0 K. The micellization free energies (ΔGm0) are in the range －63.98～－76.20 kJ•mol-1 in the studied ranges of temperature and NaCl concentration. The process of micellization of C16-MADS in aqueous solution is mainly driven by the entropy.
2005, 21(11): 1244-1248
doi: 10.3866/PKU.WHXB20051110
Abstract:
1,6-hexamethylene diamine (HMD) was grafted onto multi-walled carbon nanotubes (MWNTs) via acid-thionyl chloride route. The characterization of MWNTs was carried out by Fourier transform infrared spectrum, thermal gravimetric analysis, field emission scanning electron microscopy and Raman spectrum. The results show that HMD is covalently bonded on the MWNTs after activating by thionyl chloride. During this process, the compact stacking microstructure induced by acid treatment is deaggregated. The apparent specific volume of functionalized MWNTs is even larger than that of the pristine MWNTs. The chemical processing of MWNTs modification was analyzed theoretically in detail and the mechanism of microstructure transformation was speculated. It is proposed that HMD molecules inserted in different carbon nanotubes and break the hydrogen bond structure formed in acidification process. Therefore the dense structure derived from acidification is modified, leading to a less compact stacking and larger apparent specific volume of MWNTs.
1,6-hexamethylene diamine (HMD) was grafted onto multi-walled carbon nanotubes (MWNTs) via acid-thionyl chloride route. The characterization of MWNTs was carried out by Fourier transform infrared spectrum, thermal gravimetric analysis, field emission scanning electron microscopy and Raman spectrum. The results show that HMD is covalently bonded on the MWNTs after activating by thionyl chloride. During this process, the compact stacking microstructure induced by acid treatment is deaggregated. The apparent specific volume of functionalized MWNTs is even larger than that of the pristine MWNTs. The chemical processing of MWNTs modification was analyzed theoretically in detail and the mechanism of microstructure transformation was speculated. It is proposed that HMD molecules inserted in different carbon nanotubes and break the hydrogen bond structure formed in acidification process. Therefore the dense structure derived from acidification is modified, leading to a less compact stacking and larger apparent specific volume of MWNTs.
2005, 21(11): 1249-1253
doi: 10.3866/PKU.WHXB20051111
Abstract:
The equilibrium solubility of the quaternary system NdCl3-CdCl2-HCl-H2O was determined at 298.15 K and the corresponding equilibrium diagram was constructed. The result shows that the quaternary system was complicated with four equilibrium solid phases CdCl2•H2O, 9CdCl2•NdCl3•20H2O (9:1 type), 5CdCl2•NdCl3•13H2O (5:1 type) and NdCl3•6H2O. The two new compounds, 9CdCl2•NdCl3•20H2O and 5CdCl2•NdCl3•13H2O, have not yet been reported in literatures, and they were congruently soluble in the quaternary. The two new compounds have been prepared from the system and characterized by XRD, TG-DTG, and fluorescence (FL) spectra. Result of FL spectra showed that the 9CdCl2•NdCl3•20H2O has weak fluorescence intensity, and 5CdCl2•NdCl3•13H2O exhibited larger fluorescence intensity than 9CdCl2•NdCl3•20H2O. X-ray powder diffraction patterns were indexed.
The equilibrium solubility of the quaternary system NdCl3-CdCl2-HCl-H2O was determined at 298.15 K and the corresponding equilibrium diagram was constructed. The result shows that the quaternary system was complicated with four equilibrium solid phases CdCl2•H2O, 9CdCl2•NdCl3•20H2O (9:1 type), 5CdCl2•NdCl3•13H2O (5:1 type) and NdCl3•6H2O. The two new compounds, 9CdCl2•NdCl3•20H2O and 5CdCl2•NdCl3•13H2O, have not yet been reported in literatures, and they were congruently soluble in the quaternary. The two new compounds have been prepared from the system and characterized by XRD, TG-DTG, and fluorescence (FL) spectra. Result of FL spectra showed that the 9CdCl2•NdCl3•20H2O has weak fluorescence intensity, and 5CdCl2•NdCl3•13H2O exhibited larger fluorescence intensity than 9CdCl2•NdCl3•20H2O. X-ray powder diffraction patterns were indexed.
2005, 21(11): 1254-1258
doi: 10.3866/PKU.WHXB20051112
Abstract:
The highly ordered anodic aluminum oxide (AAO) film, was prepared with electrochemical anodization method. The as-synthesized AAO film was amorphous as seen from XRD result. Amorphous alumina nanowires were successfully and easily obtained with high yield by etching AAO films in a mixture of H3PO4 and H2CrO4, NaOH, HCl, or H3PO4 solutions. The AAO film annealed at 800 ℃ for 4 h turned to γ-Al2O3. γ-Al2O3alumina nanowires were also obtained with high yield by etching γ-Al2O3 AAO film. Effects of the type of etching solutions, the etching time and the crystalline structure of AAO film on the preparation of alumina nanowire were carefully investigated. And the morphology and structure of alumina nanowires were studied by SEM, TEM and XRD. The results showed that in many kinds of solutions the alumina nanowire could be fabricated by etching method. The length (L) of the nanowire would increase and the diameter (D) would decrease when the etching time became longer, but the ratio of L /D would increase. The crystalline structure of the alumina nanowire was in accordance with that of the AAO film. Furthermore, the morphology of the AAO film was characterized by atomic force microscope (AFM) and SEM in detail. On the basis of AFM and SEM observations, a possible formation mechanism of the alumina nanowire was discussed, and the plum bloom-shape microstructure of the AAO film was considered to be the essential factor deciding the formation of the alumina nanowire.
The highly ordered anodic aluminum oxide (AAO) film, was prepared with electrochemical anodization method. The as-synthesized AAO film was amorphous as seen from XRD result. Amorphous alumina nanowires were successfully and easily obtained with high yield by etching AAO films in a mixture of H3PO4 and H2CrO4, NaOH, HCl, or H3PO4 solutions. The AAO film annealed at 800 ℃ for 4 h turned to γ-Al2O3. γ-Al2O3alumina nanowires were also obtained with high yield by etching γ-Al2O3 AAO film. Effects of the type of etching solutions, the etching time and the crystalline structure of AAO film on the preparation of alumina nanowire were carefully investigated. And the morphology and structure of alumina nanowires were studied by SEM, TEM and XRD. The results showed that in many kinds of solutions the alumina nanowire could be fabricated by etching method. The length (L) of the nanowire would increase and the diameter (D) would decrease when the etching time became longer, but the ratio of L /D would increase. The crystalline structure of the alumina nanowire was in accordance with that of the AAO film. Furthermore, the morphology of the AAO film was characterized by atomic force microscope (AFM) and SEM in detail. On the basis of AFM and SEM observations, a possible formation mechanism of the alumina nanowire was discussed, and the plum bloom-shape microstructure of the AAO film was considered to be the essential factor deciding the formation of the alumina nanowire.
2005, 21(11): 1259-1263
doi: 10.3866/PKU.WHXB20051113
Abstract:
Three dimensional structure-activity relationship of 55 muscarinic receptor a nists were studied using comparative molecular field analysis (CoMFA) technique. The relationship between the activities and structures was significant with cross-validated value (q2), non-cross-validated value (R2) and standard error of estimate (SEE) of 0.507, 0.982 and 0.218, respectively. The result indicated that there is a od correlation between the distribution of molecular steric and electrostatic field and bioactivity. This model can not only well predict the activity of the compound in the training set and test set, but also contribute to gain further insights into the requirements for potential a nists and rational design of novel molecules based on the CoMFA contour plots.
Three dimensional structure-activity relationship of 55 muscarinic receptor a nists were studied using comparative molecular field analysis (CoMFA) technique. The relationship between the activities and structures was significant with cross-validated value (q2), non-cross-validated value (R2) and standard error of estimate (SEE) of 0.507, 0.982 and 0.218, respectively. The result indicated that there is a od correlation between the distribution of molecular steric and electrostatic field and bioactivity. This model can not only well predict the activity of the compound in the training set and test set, but also contribute to gain further insights into the requirements for potential a nists and rational design of novel molecules based on the CoMFA contour plots.
2005, 21(11): 1263-1268
doi: 10.3866/PKU.WHXB20051114
Abstract:
A novel gel polymer electrolyte (GPE) based on noepentyl glycol diacrylate (NPGDA) and poly(vinyli-dene fluofide-co-hexafluoropropylenen) (PVDF-HFP) was prepared by a thermal polymerization method. GPE with a stable interpenetrating polymer network (IPN) structure was used to assemble polymer lithium-ion batteries. The influence of PVDF-HFP/NPGDA mass ratios on the characteristics of GPE was studied by scanning electron microscopy, linear sweep voltammetry and electrochemical impedance spectroscopy. The results show that PVDF-HFP/NPGDA mass ratio greatly affects the performances of GPE, such as surface morphology and ionic conductivity. When the mass ratio between PVDF-HFP and NPGDA is 1:1, GPE boasts a high ionic conductivity of 6.99×10-3 S•cm-1 and an electrochemical stability window of 4.8 V(vs Li+/Li) at 25 ℃. The polymer lithium-ion batteries based on GPE also present excellent performances, such as high rate capability and discharge voltage plateau, od temperature reliability, and excellent cycling.
A novel gel polymer electrolyte (GPE) based on noepentyl glycol diacrylate (NPGDA) and poly(vinyli-dene fluofide-co-hexafluoropropylenen) (PVDF-HFP) was prepared by a thermal polymerization method. GPE with a stable interpenetrating polymer network (IPN) structure was used to assemble polymer lithium-ion batteries. The influence of PVDF-HFP/NPGDA mass ratios on the characteristics of GPE was studied by scanning electron microscopy, linear sweep voltammetry and electrochemical impedance spectroscopy. The results show that PVDF-HFP/NPGDA mass ratio greatly affects the performances of GPE, such as surface morphology and ionic conductivity. When the mass ratio between PVDF-HFP and NPGDA is 1:1, GPE boasts a high ionic conductivity of 6.99×10-3 S•cm-1 and an electrochemical stability window of 4.8 V(vs Li+/Li) at 25 ℃. The polymer lithium-ion batteries based on GPE also present excellent performances, such as high rate capability and discharge voltage plateau, od temperature reliability, and excellent cycling.
2005, 21(11): 1269-1273
doi: 10.3866/PKU.WHXB20051115
Abstract:
In the multi-photon ionization experiment, the parent ion peak of time-of-flight (TOF) was observed to become broader with increasing laser power. Briefly, this phenomenon is caused by the space-charge effect of ions. A qualitative theoretical model, that the ion cloud created by the laser has a spherical form and the initial charge distribution is Gaussian, is used to evaluate the full width at half maximum (FWHM), which depends on the laser intensity, the pressure of the sample gas, the extraction electric field, the ionic mass, and the focal length of the lens employed. The proposed model agrees well with the experimental data.
In the multi-photon ionization experiment, the parent ion peak of time-of-flight (TOF) was observed to become broader with increasing laser power. Briefly, this phenomenon is caused by the space-charge effect of ions. A qualitative theoretical model, that the ion cloud created by the laser has a spherical form and the initial charge distribution is Gaussian, is used to evaluate the full width at half maximum (FWHM), which depends on the laser intensity, the pressure of the sample gas, the extraction electric field, the ionic mass, and the focal length of the lens employed. The proposed model agrees well with the experimental data.
2005, 21(11): 1274-1279
doi: 10.3866/PKU.WHXB20051116
Abstract:
A series of TiO2-X films doped with different halides X－(I－, Br－, Cl－, and F－) coated on the slide was prepared by dip-coating in the TiO2 sol into which potassium halide (including KI, KBr, KCl and KF) was introduced. The photo-induced hydrophilicity of TiO2-I films with different contents I－ was investigated by testing the change of water contact angle on film’s surface with UV light irradiation time, so was the changes in photoinduced hydrophilicity of TiO2 films containing different halides. Then, the durability of the TiO2-X films was investigated by testing the change of water contact angle with dark storage time. Firstly, this result shows that the photo-induced hydrophilic property of TiO2 films could be enhanced by introducing a little KI into TiO2 sol, at the best with KI content of 1.0×10-5 mol•L-1. However, with the further increase of KI, the photo-induced hydrophilic property of TiO2-I films would decrease, and even worse than that of pure TiO2 films when the KI contents is 1.0×10-2 mol•L-1. Secondly, introducing KBr and KCl of 1.0×10-5 mol•L-1 into TiO2 sol could also enhance the photo-induced hydrophilicity of TiO2 films in an order of KI>KBr>KCl, but introducing KF decreased that of TiO2 films. Finally, introducing KX (KI and KF) could increase durability of hydrophilicity of TiO2 films under dark storage condition, and KF shows a better effect than KI. Based on these results, it is suggested that the halides act as electron donors or scavengers to affect the photo-induced hydrophility of TiO2 films, and the mechanisms of photo-induced hydrophilicity of TiO2-X films is proposed. However, the higher durability of hydrophilicity of TiO2-X films compared with pure TiO2 films may be due to a great stability of hydrophilicity site Ti—OH, which is caused by the strong binding action (hydron bond) between Ti—X and Ti—OH.
A series of TiO2-X films doped with different halides X－(I－, Br－, Cl－, and F－) coated on the slide was prepared by dip-coating in the TiO2 sol into which potassium halide (including KI, KBr, KCl and KF) was introduced. The photo-induced hydrophilicity of TiO2-I films with different contents I－ was investigated by testing the change of water contact angle on film’s surface with UV light irradiation time, so was the changes in photoinduced hydrophilicity of TiO2 films containing different halides. Then, the durability of the TiO2-X films was investigated by testing the change of water contact angle with dark storage time. Firstly, this result shows that the photo-induced hydrophilic property of TiO2 films could be enhanced by introducing a little KI into TiO2 sol, at the best with KI content of 1.0×10-5 mol•L-1. However, with the further increase of KI, the photo-induced hydrophilic property of TiO2-I films would decrease, and even worse than that of pure TiO2 films when the KI contents is 1.0×10-2 mol•L-1. Secondly, introducing KBr and KCl of 1.0×10-5 mol•L-1 into TiO2 sol could also enhance the photo-induced hydrophilicity of TiO2 films in an order of KI>KBr>KCl, but introducing KF decreased that of TiO2 films. Finally, introducing KX (KI and KF) could increase durability of hydrophilicity of TiO2 films under dark storage condition, and KF shows a better effect than KI. Based on these results, it is suggested that the halides act as electron donors or scavengers to affect the photo-induced hydrophility of TiO2 films, and the mechanisms of photo-induced hydrophilicity of TiO2-X films is proposed. However, the higher durability of hydrophilicity of TiO2-X films compared with pure TiO2 films may be due to a great stability of hydrophilicity site Ti—OH, which is caused by the strong binding action (hydron bond) between Ti—X and Ti—OH.
2005, 21(11): 1280-1284
doi: 10.3866/PKU.WHXB20051117
Abstract:
The adsorption and oxidation of isopropanol in alkaline media at platinum electrode have been investigated by using electrochemical quartz crystal microbalance (EQCM) and in situ FTIR spectroscopy. The results show that there is no self-poisoning in the electrooxidation of isopropanol in alkaline media. Though no poison species, such as CO, are evidenced by in situ FTIR spectroscopy, the adsorption of isopropanol or its dissociative products on Pt surface is suggested by EQCM data. The final product of isopropanol oxidation is only acetone under experimental condition, which suggests that the oxidation of isopropanol into acetone takes place via dehydrogenation step. The EQCM studies provide quantitative results of surface mass variation and have thrown new light in the elucidating isopropanol oxidation.
The adsorption and oxidation of isopropanol in alkaline media at platinum electrode have been investigated by using electrochemical quartz crystal microbalance (EQCM) and in situ FTIR spectroscopy. The results show that there is no self-poisoning in the electrooxidation of isopropanol in alkaline media. Though no poison species, such as CO, are evidenced by in situ FTIR spectroscopy, the adsorption of isopropanol or its dissociative products on Pt surface is suggested by EQCM data. The final product of isopropanol oxidation is only acetone under experimental condition, which suggests that the oxidation of isopropanol into acetone takes place via dehydrogenation step. The EQCM studies provide quantitative results of surface mass variation and have thrown new light in the elucidating isopropanol oxidation.
2005, 21(11): 1285-1290
doi: 10.3866/PKU.WHXB20051118
Abstract:
Spinel LiMn2O4 and LiNiyCo0.1－yMn1.9O4 (y=0, 0.05, 0.10) samples were prepared by a precipitation method. The structure, morphology, and electrochemical performance of the samples were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron micrographs (SEM), charge-discharge measurements, and electrochemical impedance spectra (EIS). The results of FT-IR and XRD indicated that the absorption band at about 519 cm-1 shifts to the high frequency with the decrease of Ni content in LiNiyCo0.1－yMn1.9O4 samples and the lattice parameter(a) of LiMn2O4 samples decreases with the addition of Ni, Co, or Ni/Co. The SEM observation displayed that the LiNiyCo0.1－yMn1.9O4 samples have lower agglomeration degree and smaller particle size. The results of the electrochemical experiments showed that the improvements on the electrochemical performance of substituted samples have some different reasons, and the LiNiyCo0.1－yMn1.9O4 sample manifests better electrochemical performance in 4 V region due to its lower electrochemical polarization and larger diffusion coefficient of Li+ ions.
Spinel LiMn2O4 and LiNiyCo0.1－yMn1.9O4 (y=0, 0.05, 0.10) samples were prepared by a precipitation method. The structure, morphology, and electrochemical performance of the samples were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron micrographs (SEM), charge-discharge measurements, and electrochemical impedance spectra (EIS). The results of FT-IR and XRD indicated that the absorption band at about 519 cm-1 shifts to the high frequency with the decrease of Ni content in LiNiyCo0.1－yMn1.9O4 samples and the lattice parameter(a) of LiMn2O4 samples decreases with the addition of Ni, Co, or Ni/Co. The SEM observation displayed that the LiNiyCo0.1－yMn1.9O4 samples have lower agglomeration degree and smaller particle size. The results of the electrochemical experiments showed that the improvements on the electrochemical performance of substituted samples have some different reasons, and the LiNiyCo0.1－yMn1.9O4 sample manifests better electrochemical performance in 4 V region due to its lower electrochemical polarization and larger diffusion coefficient of Li+ ions.
2005, 21(11): 1291-1294
doi: 10.3866/PKU.WHXB20051119
Abstract:
Methane coupling to produce C2 hydrocarbons was studied with a newly developed rotary helix electrode in glow discharge plasma at atmospheric pressure. Effects of peak electric voltage and feed flow rates of methane and hydrogen on CH4 conversion, C2 yield, and the selectivity were investigated using copper or stainless steel electrode. 69.85% of C2 single process yield, 70.46% of CH4 conversion, and 99.14% of C2 selectivity were obtained at optimized conditions.
Methane coupling to produce C2 hydrocarbons was studied with a newly developed rotary helix electrode in glow discharge plasma at atmospheric pressure. Effects of peak electric voltage and feed flow rates of methane and hydrogen on CH4 conversion, C2 yield, and the selectivity were investigated using copper or stainless steel electrode. 69.85% of C2 single process yield, 70.46% of CH4 conversion, and 99.14% of C2 selectivity were obtained at optimized conditions.
2005, 21(11): 1295-1298
doi: 10.3866/PKU.WHXB20051120
Abstract:
The lattice-fluid hydrogen bond equation of state model(LFHB model) is used to correlate 1H NMR chemical shift of the proton in hydroxyl(—OH) of alcohol + inert solvent mixtures. The 29 sets of data for 17 systems are correlated using only one parameter. In addition, this parameter can be used to predict the chemical shift of mixtures at different temperatures.
The lattice-fluid hydrogen bond equation of state model(LFHB model) is used to correlate 1H NMR chemical shift of the proton in hydroxyl(—OH) of alcohol + inert solvent mixtures. The 29 sets of data for 17 systems are correlated using only one parameter. In addition, this parameter can be used to predict the chemical shift of mixtures at different temperatures.
2005, 21(11): 1299-1302
doi: 10.3866/PKU.WHXB20051121
Abstract:
By measuring polarization curves and alternating-current impedances, the corrosion resistance of electroless Ni-P deposits with P contents from 16.2% to 23.4%(x) was investigated in 5% (w) NaCl solution. It was found that there was a maximum of polarization resistance (Rp) when the P content was at 21%～22%(x) and the peak temperature of crystallization(Tp) of electroless Ni-P alloys, determinated by differential scanning calorimetry (DSC), also showed a maximum at such a P content. X-ray diffraction (XRD) experiments indicated that the electroless Ni-P deposits were amorphous. The maxima for both polarization resistance (Rp) and the peak temperature of crystallization(Tp) were explained in terms of the rhomb unit structure model (RUSM) for amorphous structures. The corrosion resistance of electroless Ni-P deposits was related to the changes of the bond numbers formed between metal (Ni) and metalloid element (P) with the P contents. The rationalization to adopt RUSM was also discussed by comparing the measured and theoretically calculated densities for electroless Ni-P deposits with various P contents.
By measuring polarization curves and alternating-current impedances, the corrosion resistance of electroless Ni-P deposits with P contents from 16.2% to 23.4%(x) was investigated in 5% (w) NaCl solution. It was found that there was a maximum of polarization resistance (Rp) when the P content was at 21%～22%(x) and the peak temperature of crystallization(Tp) of electroless Ni-P alloys, determinated by differential scanning calorimetry (DSC), also showed a maximum at such a P content. X-ray diffraction (XRD) experiments indicated that the electroless Ni-P deposits were amorphous. The maxima for both polarization resistance (Rp) and the peak temperature of crystallization(Tp) were explained in terms of the rhomb unit structure model (RUSM) for amorphous structures. The corrosion resistance of electroless Ni-P deposits was related to the changes of the bond numbers formed between metal (Ni) and metalloid element (P) with the P contents. The rationalization to adopt RUSM was also discussed by comparing the measured and theoretically calculated densities for electroless Ni-P deposits with various P contents.
2005, 21(11): 1303-1306
doi: 10.3866/PKU.WHXB20051122
Abstract:
Electrochemical scanning tunnelling microscope (ECSTM) was used to induce local electrodeposition under mild electrochemical and tunnelling bias conditions. The Pd nanocluster arrays were fabricated on Au(111) in PdCl2 and PdSO4 solutions respectively and different parameters for nanostructructuring were explored in the corresponding solutions.
Electrochemical scanning tunnelling microscope (ECSTM) was used to induce local electrodeposition under mild electrochemical and tunnelling bias conditions. The Pd nanocluster arrays were fabricated on Au(111) in PdCl2 and PdSO4 solutions respectively and different parameters for nanostructructuring were explored in the corresponding solutions.
2005, 21(11): 1307-1310
doi: 10.3866/PKU.WHXB20051123
Abstract:
The glass transition behaviors of N-alkyl chitosan were investigated by means of differential scanning calorimetry (DSC) and thermally stimulated current (TSC) spectroscopy. In DSC measurements, the second heating run was used to eliminate the effect of solvents and heat history on glass transition temperature (Tg), and also physical aging was used to improve the sensitivity of Tg measurements by enhancing the enthalpy endothermal peaks. The results of two techniques showed that the glass transition temperatures of three N-alkyl chitosans were all within 110~150 ℃. When the length of flexible side-alkyl groups was larger, the transition points shifted to lower temperature. But N-methyl chitosan is an exception, its Tg is slightly higher than chitosan because of the steric hindrance of side group.
The glass transition behaviors of N-alkyl chitosan were investigated by means of differential scanning calorimetry (DSC) and thermally stimulated current (TSC) spectroscopy. In DSC measurements, the second heating run was used to eliminate the effect of solvents and heat history on glass transition temperature (Tg), and also physical aging was used to improve the sensitivity of Tg measurements by enhancing the enthalpy endothermal peaks. The results of two techniques showed that the glass transition temperatures of three N-alkyl chitosans were all within 110~150 ℃. When the length of flexible side-alkyl groups was larger, the transition points shifted to lower temperature. But N-methyl chitosan is an exception, its Tg is slightly higher than chitosan because of the steric hindrance of side group.
2005, 21(11): 1311-1314
doi: 10.3866/PKU.WHXB20051124
Abstract:
Mesoporous Cr-MSU-1 was successfully prepared by using sodium silicate, chromium nitrate, fatty alcohol polyoxyethylene ether (A(EO)9) as the source of silicone, metal and mesostructure-directing agent, respectively. Cr-MSU-1 and MSU-1 were comparatively characterized by XRD, HRTEM, N2 adsorption-desorption, FT-IR and DR UV-Vis techniques. No obvious differences on structural and textural properties between them were observed from XRD patterns and N2 adsorption-desorption isotherms. The HRTEM image confirmed that Cr-MSU-1 took on wormlike mesostructure that was similar to MSU-1. In the FT-IR patterns, the introduction of Cr showed slight influence to adsorption bands of MSU-1, which indicated that Cr was incorporated into the framework of MSU-1. It is suggested from the DR UV-Vis spectra that Cr species mostly formed Cr(VI) in tetrahedral coordination in Cr-MSU-1. The Cr-MSU-1 catalyst performs well in the dehydrogenation of ethane with CO2, resulting in the production of ethylene with a conversion of 31.7% and a selectivity of 96.1% at 650 ℃.
Mesoporous Cr-MSU-1 was successfully prepared by using sodium silicate, chromium nitrate, fatty alcohol polyoxyethylene ether (A(EO)9) as the source of silicone, metal and mesostructure-directing agent, respectively. Cr-MSU-1 and MSU-1 were comparatively characterized by XRD, HRTEM, N2 adsorption-desorption, FT-IR and DR UV-Vis techniques. No obvious differences on structural and textural properties between them were observed from XRD patterns and N2 adsorption-desorption isotherms. The HRTEM image confirmed that Cr-MSU-1 took on wormlike mesostructure that was similar to MSU-1. In the FT-IR patterns, the introduction of Cr showed slight influence to adsorption bands of MSU-1, which indicated that Cr was incorporated into the framework of MSU-1. It is suggested from the DR UV-Vis spectra that Cr species mostly formed Cr(VI) in tetrahedral coordination in Cr-MSU-1. The Cr-MSU-1 catalyst performs well in the dehydrogenation of ethane with CO2, resulting in the production of ethylene with a conversion of 31.7% and a selectivity of 96.1% at 650 ℃.
2005, 21(11): 1315-1318
doi: 10.3866/PKU.WHXB20051125
Abstract:
Densities of L-serine-n-propanol-water ternary solutions have been measured at 298.15 K by an oscillating-tube densimeter. Apparent molar volumes, limiting partial molar volumes, transfer partial molar volumes and hydration numbers for L-serine have been calculated. The transfer volumes from water to n-propanol-water mixtures and hydration numbers have been discussed in terms of the structural hydration interaction model. The results show that a dominant interaction between —OH group of n-propanol and the zwitterionic group of serine gives positive contribution to the transfer volume. The transfer volumes of serine from water to n-propanol-water mixed solvents are positive, and increase with increasing n-propanol concentration, while the hydration numbers decrease with increasing n-propanol concentration.
Densities of L-serine-n-propanol-water ternary solutions have been measured at 298.15 K by an oscillating-tube densimeter. Apparent molar volumes, limiting partial molar volumes, transfer partial molar volumes and hydration numbers for L-serine have been calculated. The transfer volumes from water to n-propanol-water mixtures and hydration numbers have been discussed in terms of the structural hydration interaction model. The results show that a dominant interaction between —OH group of n-propanol and the zwitterionic group of serine gives positive contribution to the transfer volume. The transfer volumes of serine from water to n-propanol-water mixed solvents are positive, and increase with increasing n-propanol concentration, while the hydration numbers decrease with increasing n-propanol concentration.
2005, 21(11): 1319-1323
doi: 10.3866/PKU.WHXB20051126
Abstract:
The dynamical Lie algebraic (DLA) formulation is used to describe the nonlinear optical process for the model system of substituted benzenes in a Pariser-Parr-Pople(PPP) Hamiltonian. It is shown how to generate the dynamical Lie algebra for the given Hamiltonian, and then the evolution operator for the system is expressed as a function of group parameters in terms of the elements of the dynamical algebra. The group parameters can be determined with a set of coupled nonlinear differential equations. The statistical average of the molecular electronic polarization can be determined according to the density operator formalism in statistical mechanics, and the hyperpolarizability of the molecules is thus obtained readily. An expression for the hyperpolarizabilities of the di-substituted benzenes as a function of the on-site energy is derived. Compared with other quantum calculations, DLA method appears to provide an effective method for the calculation of the hyperpolarizability of conjugated organic molecules.
The dynamical Lie algebraic (DLA) formulation is used to describe the nonlinear optical process for the model system of substituted benzenes in a Pariser-Parr-Pople(PPP) Hamiltonian. It is shown how to generate the dynamical Lie algebra for the given Hamiltonian, and then the evolution operator for the system is expressed as a function of group parameters in terms of the elements of the dynamical algebra. The group parameters can be determined with a set of coupled nonlinear differential equations. The statistical average of the molecular electronic polarization can be determined according to the density operator formalism in statistical mechanics, and the hyperpolarizability of the molecules is thus obtained readily. An expression for the hyperpolarizabilities of the di-substituted benzenes as a function of the on-site energy is derived. Compared with other quantum calculations, DLA method appears to provide an effective method for the calculation of the hyperpolarizability of conjugated organic molecules.
2005, 21(11): 1324-1330
doi: 10.3866/PKU.WHXB20051127
Abstract:
Recent progress in temperature-controlled transition of self assemblies in surfactant solutions was summarized. Special attention was paid on the phase transition of vesicles, temperature-induced micelle/vesicle transition, cloud point phenomenon in ionic surfactant systems, temperature-controlled vesicle aggregation and temperature-induced formation and transformation of liquid crystals etc. It was demonstrated that temperature can serve as a simple and effective way in adjusting organized self-assemblies under certain conditions.
Recent progress in temperature-controlled transition of self assemblies in surfactant solutions was summarized. Special attention was paid on the phase transition of vesicles, temperature-induced micelle/vesicle transition, cloud point phenomenon in ionic surfactant systems, temperature-controlled vesicle aggregation and temperature-induced formation and transformation of liquid crystals etc. It was demonstrated that temperature can serve as a simple and effective way in adjusting organized self-assemblies under certain conditions.
