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2003 Volume 19 Issue 4
2003, 19(04): 289-292
doi: 10.3866/PKU.WHXB20030401
Abstract:
A new set of parameters consistent with AMBER force field for generalized Born model was proposed. The new set of parameters includes the initial radius and screen parameters for 21 atom types. The parameters were developed by fitting the experimental aqueous free energies of solvation of 359 small organic molecules using a genetic al rithm. The derived parameters were then used to predict the solvation free energy of 44 small organic molecules. The calculated results are in od agreement with the experimental values, which are much better than those using the Jayaram’s parameters. Moreover, the derived parameters were then used to predict the solvation free energy of 15 proteins, and the calculated results showed higher linear correlation with those predicted by PB/SA.
A new set of parameters consistent with AMBER force field for generalized Born model was proposed. The new set of parameters includes the initial radius and screen parameters for 21 atom types. The parameters were developed by fitting the experimental aqueous free energies of solvation of 359 small organic molecules using a genetic al rithm. The derived parameters were then used to predict the solvation free energy of 44 small organic molecules. The calculated results are in od agreement with the experimental values, which are much better than those using the Jayaram’s parameters. Moreover, the derived parameters were then used to predict the solvation free energy of 15 proteins, and the calculated results showed higher linear correlation with those predicted by PB/SA.
2003, 19(04): 293-296
doi: 10.3866/PKU.WHXB20030402
Abstract:
Potential energy curves for the excited states of some halogen diatomic molecules have been studied using the energy-consistent method (ECM) .The results of these states,β1g(3P2) and A′(2μ3Π) of Br2,1μ(1D) of I2 and A′(2μ3Π) of Cl2,show that the ECM potential is superior to give correct full range potential to other potentials such as Morse and Huxley-Murrell-Sorbie (HMS) potential, especially for the electronic excited states of the halogen diatomic molecules. It is seen that ECM method is not only successfully applicable for the electronic states of lighter molecules but also for those of heavier molecules.
Potential energy curves for the excited states of some halogen diatomic molecules have been studied using the energy-consistent method (ECM) .The results of these states,β1g(3P2) and A′(2μ3Π) of Br2,1μ(1D) of I2 and A′(2μ3Π) of Cl2,show that the ECM potential is superior to give correct full range potential to other potentials such as Morse and Huxley-Murrell-Sorbie (HMS) potential, especially for the electronic excited states of the halogen diatomic molecules. It is seen that ECM method is not only successfully applicable for the electronic states of lighter molecules but also for those of heavier molecules.
2003, 19(04): 297-301
doi: 10.3866/PKU.WHXB20030403
Abstract:
The dilational viscoelasticity properties of decane-water interface containing two demulsifiers with straight chain SP169 (octadecanol polyoxypropylene-polyoxyethylene ether) and branch chain AE121 (tetraethylenehexamine polyoxypropylene-polyoxyethylene ether)respectively were investigated. The dependence of dilational modulus on dilational frequency and demulsifier concentration was expounded. The influences of two demulsifiers on dilational properties of oil-water interface containing surface-active fraction from crude oil were also studied. The dynamic interfacial tensions between solutions of two demulsifiers and decane were measured and were related to the interfacial dilational rheology properties. The results showed that the two demulsifiers could decrease remarkably the dilational modulus of oil-water interface containing surface-active fraction from crude oil. At low concentration, because of stronger adsorption ability, the effect of decreasing dilational modulus of SP169 was better. But above a certain concentration, AE121 was preferential because of its higher substitution ability. Since the interface film containing demulsifier had a certain dilational modulus itself, the dosage of demulsifier could not be much higher.
The dilational viscoelasticity properties of decane-water interface containing two demulsifiers with straight chain SP169 (octadecanol polyoxypropylene-polyoxyethylene ether) and branch chain AE121 (tetraethylenehexamine polyoxypropylene-polyoxyethylene ether)respectively were investigated. The dependence of dilational modulus on dilational frequency and demulsifier concentration was expounded. The influences of two demulsifiers on dilational properties of oil-water interface containing surface-active fraction from crude oil were also studied. The dynamic interfacial tensions between solutions of two demulsifiers and decane were measured and were related to the interfacial dilational rheology properties. The results showed that the two demulsifiers could decrease remarkably the dilational modulus of oil-water interface containing surface-active fraction from crude oil. At low concentration, because of stronger adsorption ability, the effect of decreasing dilational modulus of SP169 was better. But above a certain concentration, AE121 was preferential because of its higher substitution ability. Since the interface film containing demulsifier had a certain dilational modulus itself, the dosage of demulsifier could not be much higher.
2003, 19(04): 302-306
doi: 10.3866/PKU.WHXB20030404
Abstract:
A pair of optical isomerism amphiphlic molecules L-C10HL（N-(4-decaoxygen- 2-hydroxybenzene methylene)-L-leucine） and D-C10HL（N-(4-decaoxygen-2-hydroxybenzene methylene)-D-leucine）were synthesized. It was found that these two compounds showed superior surface activity and aggregation capability at higher pH value, which is so different from the traditional carboxylate surfactants. Furthermore, the interaction of L-C10HL and D-C10HL with cyclodextrin was also investigated by fluorescence excitation spectrum and circular dichroism spectrum.
A pair of optical isomerism amphiphlic molecules L-C10HL（N-(4-decaoxygen- 2-hydroxybenzene methylene)-L-leucine） and D-C10HL（N-(4-decaoxygen-2-hydroxybenzene methylene)-D-leucine）were synthesized. It was found that these two compounds showed superior surface activity and aggregation capability at higher pH value, which is so different from the traditional carboxylate surfactants. Furthermore, the interaction of L-C10HL and D-C10HL with cyclodextrin was also investigated by fluorescence excitation spectrum and circular dichroism spectrum.
2003, 19(04): 307-310
doi: 10.3866/PKU.WHXB20030405
Abstract:
Poly(1-aminoanthraquinone) is synthesized by chemical method and used as positive electrode in rechargeable lithium battery. Using the techniques of infrared (IR) spectrum, scan electronic microscopy (SEM), granularity, cyclic voltammograms (CVs) and charge-discharge, the function group, microscopic structure, particulate size and the electrochemical performance of the polymer are studied and analyzed. When used in lithium second battery with lithium, the initial discharge capacity of poly(1-aminoanthraquinone) is 218.3 mAh•g－1,it can keep excellent cycle efficiency after 25 charge-discharge cycles. In virtue of its high energy density and od cycling capability, the poly (1-aminoanthraquinone) is a promising positive electrode material for lithium secondary battery.
Poly(1-aminoanthraquinone) is synthesized by chemical method and used as positive electrode in rechargeable lithium battery. Using the techniques of infrared (IR) spectrum, scan electronic microscopy (SEM), granularity, cyclic voltammograms (CVs) and charge-discharge, the function group, microscopic structure, particulate size and the electrochemical performance of the polymer are studied and analyzed. When used in lithium second battery with lithium, the initial discharge capacity of poly(1-aminoanthraquinone) is 218.3 mAh•g－1,it can keep excellent cycle efficiency after 25 charge-discharge cycles. In virtue of its high energy density and od cycling capability, the poly (1-aminoanthraquinone) is a promising positive electrode material for lithium secondary battery.
2003, 19(04): 311-314
doi: 10.3866/PKU.WHXB20030406
Abstract:
The fluorescence-doped silica nanoparticles (FDS-NP) were synthesized in a microemulsion system of polyoxyethylene nonylphenyl ether (OP-10)/ cyclohexane/ammonium hydroxide. To elucidate the character of FDS-NP, techniques of electron microscopy, analysis of spectrum and collisional quenching of fluorescence were used. In order to study the fluorescent signal and intensity of FDS-NP in the cultured cells, laser-scanning confocal microscope and the analysis of flow cytometry were utilized. The results showed that the size of FDS-NP was very small (about 20 nm), the distribution was narrow, the shape was circular and lubricity, and the fluorescence was photostable. Cultured cells could efficiently uptake FDS-NP, and yield high fluorescent signal and intensity. All these indicated that FDS-NP is an important nanoparticulate biomarker, and is applicable to many areas of modern biochemical analysis, such as ultrasensitive detection, immunoassys, as well as cellular biology.
The fluorescence-doped silica nanoparticles (FDS-NP) were synthesized in a microemulsion system of polyoxyethylene nonylphenyl ether (OP-10)/ cyclohexane/ammonium hydroxide. To elucidate the character of FDS-NP, techniques of electron microscopy, analysis of spectrum and collisional quenching of fluorescence were used. In order to study the fluorescent signal and intensity of FDS-NP in the cultured cells, laser-scanning confocal microscope and the analysis of flow cytometry were utilized. The results showed that the size of FDS-NP was very small (about 20 nm), the distribution was narrow, the shape was circular and lubricity, and the fluorescence was photostable. Cultured cells could efficiently uptake FDS-NP, and yield high fluorescent signal and intensity. All these indicated that FDS-NP is an important nanoparticulate biomarker, and is applicable to many areas of modern biochemical analysis, such as ultrasensitive detection, immunoassys, as well as cellular biology.
2003, 19(04): 315-319
doi: 10.3866/PKU.WHXB20030407
Abstract:
The kinetics of formation of ZnSe nanocrystals from the complex ZnSe (C2H8N2) has been investigated by means of non-isothermal TG-DTG at various heating rates of 5.0,10.0,15.0 and 20.0 ℃•min－1.The results show that the formation of ZnSe nanocrystals was controlled by three-dimension diffusion. The most probable kinetic function in differential form, and in integral form, the apparent activation energy (E) and the pre-exponential constant (A) of the process are f (α)＝ ，G(α)＝ ,209.61 kJ•mol－1 and 1015.7 s－1, respectively. The kinetics equation is . The calculated results are in accordance with the experiments. ZnO nanocrystal with less than 40 nm sizes has also been obtained from ZnSe nanocrystals.
The kinetics of formation of ZnSe nanocrystals from the complex ZnSe (C2H8N2) has been investigated by means of non-isothermal TG-DTG at various heating rates of 5.0,10.0,15.0 and 20.0 ℃•min－1.The results show that the formation of ZnSe nanocrystals was controlled by three-dimension diffusion. The most probable kinetic function in differential form, and in integral form, the apparent activation energy (E) and the pre-exponential constant (A) of the process are f (α)＝ ，G(α)＝ ,209.61 kJ•mol－1 and 1015.7 s－1, respectively. The kinetics equation is . The calculated results are in accordance with the experiments. ZnO nanocrystal with less than 40 nm sizes has also been obtained from ZnSe nanocrystals.
2003, 19(04): 320-325
doi: 10.3866/PKU.WHXB20030408
Abstract:
Four novel chiral dinuclear Salen complexes [(Cu)2L•H2O(2), (Ni)2L(3), (Zn)2L•H2O(4), (MnCl)2L•2H2O(5)] have been synthesized (L is chiral dimeric Salen ligand which is synthesized from (R, R)-diaminocyclohexane, 3,5-di-tert-butyl salicylaldehyde, 5,5′-methylene-di-salicylaldehyde). These ligands and complexes were characterized by elemental analysis, 1H NMR, UV-Vis, FT-IR, CD spectra. The UV-Vis spectra were compared with those of monomeric Salen ligand and complex. It was found that the position and shape of absorption band are similar to those of the corresponding monomeric compounds, but the values of the absorption peak(ε) are approximately two folds larger. Furthermore Cotton effect and Cotton split of CD spectra of these chiral compounds were explained by the exciton interaction theory. It seemed that the direction of Cotton split depend on the configuration of diaminocyclohexane. (R, R)-diaminocyclohexane termined the chirality of Salen compounds as negative, and the positive and negative component of Cotton split lie at higher and lower energy respectively.
Four novel chiral dinuclear Salen complexes [(Cu)2L•H2O(2), (Ni)2L(3), (Zn)2L•H2O(4), (MnCl)2L•2H2O(5)] have been synthesized (L is chiral dimeric Salen ligand which is synthesized from (R, R)-diaminocyclohexane, 3,5-di-tert-butyl salicylaldehyde, 5,5′-methylene-di-salicylaldehyde). These ligands and complexes were characterized by elemental analysis, 1H NMR, UV-Vis, FT-IR, CD spectra. The UV-Vis spectra were compared with those of monomeric Salen ligand and complex. It was found that the position and shape of absorption band are similar to those of the corresponding monomeric compounds, but the values of the absorption peak(ε) are approximately two folds larger. Furthermore Cotton effect and Cotton split of CD spectra of these chiral compounds were explained by the exciton interaction theory. It seemed that the direction of Cotton split depend on the configuration of diaminocyclohexane. (R, R)-diaminocyclohexane termined the chirality of Salen compounds as negative, and the positive and negative component of Cotton split lie at higher and lower energy respectively.
2003, 19(04): 326-328
doi: 10.3866/PKU.WHXB20030409
Abstract:
Using urea as homogeneous precipitant, the precursor of mesoporous zirconia was synthesized by hydrothermal method. After heat-treatment at 500～550 ℃ for 2 h, the crystalline (t or m phase) mesoporous zirconia with short-range order was prepared. Their BJH desorption pore size and BET surface area are about 4～6 nm and 60～90 m2•g－1, respectively.
Using urea as homogeneous precipitant, the precursor of mesoporous zirconia was synthesized by hydrothermal method. After heat-treatment at 500～550 ℃ for 2 h, the crystalline (t or m phase) mesoporous zirconia with short-range order was prepared. Their BJH desorption pore size and BET surface area are about 4～6 nm and 60～90 m2•g－1, respectively.
2003, 19(04): 329-333
doi: 10.3866/PKU.WHXB20030410
Abstract:
The photocatalytic generation of hydrogen from water using single and binary component pollutants as electron donors in aqueous Pt/TiO2 suspension has been investigated. The adsorption of these donors on TiO2 was also monitored by in situ attenuated total reflection infrared spectroscopy (ATR-IR). In the single component system (formaldehyde, formic acid and oxalic acid), the efficiencies of electron donors follow the order:H2C2O4 >HCOOH >HCHO. The order is consistent with the adsorption strength of the electron donors on TiO2 determined by ATR-IR, which suggests that the hydrogen evolution efficiency is dependent on the strength of surface interaction. In the binary mixture systems consisting of oxalic acid and formic acid, the overall kinetics of hydrogen evolution and decomposition of pollutants are dependent on their adsorption strengths on TiO2 and their concentration levels as well. The result can be explained by their competitive adsorption on TiO2. ATR-IR characterization confirmed illustratively the above explanation.
The photocatalytic generation of hydrogen from water using single and binary component pollutants as electron donors in aqueous Pt/TiO2 suspension has been investigated. The adsorption of these donors on TiO2 was also monitored by in situ attenuated total reflection infrared spectroscopy (ATR-IR). In the single component system (formaldehyde, formic acid and oxalic acid), the efficiencies of electron donors follow the order:H2C2O4 >HCOOH >HCHO. The order is consistent with the adsorption strength of the electron donors on TiO2 determined by ATR-IR, which suggests that the hydrogen evolution efficiency is dependent on the strength of surface interaction. In the binary mixture systems consisting of oxalic acid and formic acid, the overall kinetics of hydrogen evolution and decomposition of pollutants are dependent on their adsorption strengths on TiO2 and their concentration levels as well. The result can be explained by their competitive adsorption on TiO2. ATR-IR characterization confirmed illustratively the above explanation.
2003, 19(04): 334-337
doi: 10.3866/PKU.WHXB20030411
Abstract:
The quantitative structure-property relationship(QSPR) was used to predict cloud point of nonionic surfactants. Several structural, electronic, spatial and thermodynamic properties were selected as descriptors to build the relation between the macroscopic properties (such as cloud point) and microscopic structures. These descriptors include the octanol/water partition coefficient, the molecular area, relative molecular mass and molecular dipole. A general five-parameter structure-property relationship between the logarithm of cloud point and the descriptors, which was developed for a set of 49 nonionic surfactants (r2=0.844), can be sued to predict cloud point of surfactants without the experimental data.
The quantitative structure-property relationship(QSPR) was used to predict cloud point of nonionic surfactants. Several structural, electronic, spatial and thermodynamic properties were selected as descriptors to build the relation between the macroscopic properties (such as cloud point) and microscopic structures. These descriptors include the octanol/water partition coefficient, the molecular area, relative molecular mass and molecular dipole. A general five-parameter structure-property relationship between the logarithm of cloud point and the descriptors, which was developed for a set of 49 nonionic surfactants (r2=0.844), can be sued to predict cloud point of surfactants without the experimental data.
2003, 19(04): 338-341
doi: 10.3866/PKU.WHXB20030412
Abstract:
The alcoholysis of dichloromethylsilane has been studied experimentally and theoretically, the first and the second step both are cooperating exothermic processes. The best reaction temperature (30 ℃), the best proportion of ethanol and dichloromethylsilane(1.8), the best mode of dropping(ethanol dropping into the solvent of dichloromethylsilane), the activation energies(72.51 and 90.29 kJ•mol－1 for main reactions, 182.6 kJ•mol－1 for side-reaction) are obtained. The reaction pathway of the main reaction is shown in Fig.1. The results of the calculation are in consistent with those of the experiments.
The alcoholysis of dichloromethylsilane has been studied experimentally and theoretically, the first and the second step both are cooperating exothermic processes. The best reaction temperature (30 ℃), the best proportion of ethanol and dichloromethylsilane(1.8), the best mode of dropping(ethanol dropping into the solvent of dichloromethylsilane), the activation energies(72.51 and 90.29 kJ•mol－1 for main reactions, 182.6 kJ•mol－1 for side-reaction) are obtained. The reaction pathway of the main reaction is shown in Fig.1. The results of the calculation are in consistent with those of the experiments.
Studies on PEMFC Electrocatalysts: Physicochemical Characterization of Homemade Pt/C Electrocatalyst
2003, 19(04): 342-346
doi: 10.3866/PKU.WHXB20030413
Abstract:
A homemade Pt/C electrocatalyst(named as THYT-1) for proton-exchange membrane fuel cell(PEMFC) was prepared and characterized comprehensively. Single-cell measurements showed that the performance of THYT-1 for hydrogen electro-oxidation was superior to that of the E-TEK Pt/C catalyst. Cyclic voltammetry measurements in a half PEM fuel cell indicated that the electro-oxidation behavior of adsorbed CO on THYT-1 and the E-TEK Pt/C catalyst was indistinguishable. XPS and XRD detections showed that platinum of the two catalysts exist mainly in the metallic state. Uniformly dispersed Pt-particles with sizes of 2～3 nm were found to be the dominant images of Pt in the TEM micrographs for both THYT-1 and the E-TEK catalysts. Application of THYT-1 catalyst in the research and development of PEMFC technology can be expected.
A homemade Pt/C electrocatalyst(named as THYT-1) for proton-exchange membrane fuel cell(PEMFC) was prepared and characterized comprehensively. Single-cell measurements showed that the performance of THYT-1 for hydrogen electro-oxidation was superior to that of the E-TEK Pt/C catalyst. Cyclic voltammetry measurements in a half PEM fuel cell indicated that the electro-oxidation behavior of adsorbed CO on THYT-1 and the E-TEK Pt/C catalyst was indistinguishable. XPS and XRD detections showed that platinum of the two catalysts exist mainly in the metallic state. Uniformly dispersed Pt-particles with sizes of 2～3 nm were found to be the dominant images of Pt in the TEM micrographs for both THYT-1 and the E-TEK catalysts. Application of THYT-1 catalyst in the research and development of PEMFC technology can be expected.
2003, 19(04): 347-351
doi: 10.3866/PKU.WHXB20030414
Abstract:
Carbon nanotubes were prepared from catalytic decomposition of methane on an aerogel catalyst. The structure of carbon nanotubes was characterized by XRD,TGA,SEM,TEM and Raman spectroscopic methods. The carbon nanotubes grown on the aerogel catalysts are hollow with smooth wall and even diameters. The average diameter of the tubes is in the range of 10～20 nm. The nanotubes obtained in this work have a large surface area and a od oxygen resistance. From the Raman spectra of carbon nanotubes grown on the aerogel catalysts, it was observed that the nanotubes prepared with this method contained defects in the graphene layers and contained amorphous carbon. Carbon species become more graphitic when reaction temperature increases or concentration of methane decreases.
Carbon nanotubes were prepared from catalytic decomposition of methane on an aerogel catalyst. The structure of carbon nanotubes was characterized by XRD,TGA,SEM,TEM and Raman spectroscopic methods. The carbon nanotubes grown on the aerogel catalysts are hollow with smooth wall and even diameters. The average diameter of the tubes is in the range of 10～20 nm. The nanotubes obtained in this work have a large surface area and a od oxygen resistance. From the Raman spectra of carbon nanotubes grown on the aerogel catalysts, it was observed that the nanotubes prepared with this method contained defects in the graphene layers and contained amorphous carbon. Carbon species become more graphitic when reaction temperature increases or concentration of methane decreases.
2003, 19(04): 352-355
doi: 10.3866/PKU.WHXB20030415
Abstract:
Equilibrium molecular dynamics simulations have been used to calculate the shear viscosity of fluid ar n both in macrovolume system and in porous media at different temperatures, densities and pore widths. Simultaneously, based on the Chapman-Enskog(CE) theory for the transport properties of hard-sphere fluids and Heyes relationships which extend the CE theory to Lennard-Jones fluids, two correlation models which can describe the viscosity of simple fluid in porous media are proposed as a function of the reduced temperature, density and pore width. The validity of the models is evaluated by comparing the calculated viscosity to the simulation data.
Equilibrium molecular dynamics simulations have been used to calculate the shear viscosity of fluid ar n both in macrovolume system and in porous media at different temperatures, densities and pore widths. Simultaneously, based on the Chapman-Enskog(CE) theory for the transport properties of hard-sphere fluids and Heyes relationships which extend the CE theory to Lennard-Jones fluids, two correlation models which can describe the viscosity of simple fluid in porous media are proposed as a function of the reduced temperature, density and pore width. The validity of the models is evaluated by comparing the calculated viscosity to the simulation data.
2003, 19(04): 356-360
doi: 10.3866/PKU.WHXB20030416
Abstract:
Density function (B3LYP) method with relativistic effective core potential (RECP) have been used to optimize the structures for the ground states (X5Σ－,X5A2) of PuC and PuC2 molecules. For PuC2（C2v） molecule, the equilibrium geometry, dissociation energy and harmonic frequency are calculated, the results show that RPuC=0.22819 nm,∠CPuC=147.67°and De=5.543 eV, and ν1,ν2 and ν3 are 61.736 cm－1,229.89 cm－1,305.58 cm－1, respectively. Analytical potential energy function for the PuC2 has been derived using many-body expansion method which is successfully used for describing the equilibrium geometry of PuC2.Molecular reaction kinetics of C＋PuC and Pu＋C2 based on this potential energy function is under way.
Density function (B3LYP) method with relativistic effective core potential (RECP) have been used to optimize the structures for the ground states (X5Σ－,X5A2) of PuC and PuC2 molecules. For PuC2（C2v） molecule, the equilibrium geometry, dissociation energy and harmonic frequency are calculated, the results show that RPuC=0.22819 nm,∠CPuC=147.67°and De=5.543 eV, and ν1,ν2 and ν3 are 61.736 cm－1,229.89 cm－1,305.58 cm－1, respectively. Analytical potential energy function for the PuC2 has been derived using many-body expansion method which is successfully used for describing the equilibrium geometry of PuC2.Molecular reaction kinetics of C＋PuC and Pu＋C2 based on this potential energy function is under way.
2003, 19(04): 361-363
doi: 10.3866/PKU.WHXB20030417
Abstract:
The thermodynamic properties of the system HCl-In2(SO4)3-H2O were studied by EMF measurement in cells without liquid junction: Pt, H2(101.325 kPa )│HCl(mA), In2(SO4)3(mB),H2O│AgCl-Ag (A) at constant total ionic strength I = 0.2、0.4、0.6、0.8、1.0、1.5 mol•kg－1 and yB=0、0.10、0.20、0.30、0.50、0.70 at different temperatures ranging from 278.15～318.15 K. The activity coefficients of HCl γA in the solution have been determined from cell (A).
The thermodynamic properties of the system HCl-In2(SO4)3-H2O were studied by EMF measurement in cells without liquid junction: Pt, H2(101.325 kPa )│HCl(mA), In2(SO4)3(mB),H2O│AgCl-Ag (A) at constant total ionic strength I = 0.2、0.4、0.6、0.8、1.0、1.5 mol•kg－1 and yB=0、0.10、0.20、0.30、0.50、0.70 at different temperatures ranging from 278.15～318.15 K. The activity coefficients of HCl γA in the solution have been determined from cell (A).
2003, 19(04): 364-367
doi: 10.3866/PKU.WHXB20030418
Abstract:
The diffusion coefficients of the SDS(Sodium dodecyl sulfate) molecules in lyotropic liquid crystal of SDS/n-C5H11OH/H2O system have been determined by the method of platinum microelectrode voltammetry.The results show that the diffusion coefficients of SDS molecules in lyotropic liquid crystal increase with water content at constant mass ratio of SDS/n-C5H11OH and also with n-pentanol content at constant mass ratio of SDS/H2O, but decrease with SDS content at constant mass ratio of H2O/n-C5H11OH.The diffusion coefficient of the SDS molecule in hexa nal liquid crystal is nearly one order of magnitude less than that of the SDS molecule in lamellar liquid crystal, but is about three to five orders less than that of the W/O and the O/W droplets.
The diffusion coefficients of the SDS(Sodium dodecyl sulfate) molecules in lyotropic liquid crystal of SDS/n-C5H11OH/H2O system have been determined by the method of platinum microelectrode voltammetry.The results show that the diffusion coefficients of SDS molecules in lyotropic liquid crystal increase with water content at constant mass ratio of SDS/n-C5H11OH and also with n-pentanol content at constant mass ratio of SDS/H2O, but decrease with SDS content at constant mass ratio of H2O/n-C5H11OH.The diffusion coefficient of the SDS molecule in hexa nal liquid crystal is nearly one order of magnitude less than that of the SDS molecule in lamellar liquid crystal, but is about three to five orders less than that of the W/O and the O/W droplets.
2003, 19(04): 368-371
doi: 10.3866/PKU.WHXB20030419
Abstract:
The effects of structurally-specific carboxylates on the crystallization of calcium oxalate(CaOx) were investigated in gel by a double diffusion technique. The ability to inhibit the aggregation of calcium oxalate monohydrate (COM) follows the sequence: tetracarboxylate (Na2EDTA) >tricarboxylate (sodium citrate) > dicarboxylate (sodium tartrate) >monocarboxylate (NaAc). The ability to induce calcium oxalate dihydrate (COD) follows the order: sodium citrate >sodium tartrate >Na2EDTA >NaAc. The counterions of carboxylic acids affected the crystallization of CaOx. The ability of both inhibiting the aggregation of COM and inducing the formation of COD follows the sequence: potassium citrate >> sodium citrate >citric acid. Both inhibiting the aggregation of COM and inducing the formation of COD can decrease the probability of the formation of urinary stones. These results may have positive significance in the prevention and cure of urinary stones.
The effects of structurally-specific carboxylates on the crystallization of calcium oxalate(CaOx) were investigated in gel by a double diffusion technique. The ability to inhibit the aggregation of calcium oxalate monohydrate (COM) follows the sequence: tetracarboxylate (Na2EDTA) >tricarboxylate (sodium citrate) > dicarboxylate (sodium tartrate) >monocarboxylate (NaAc). The ability to induce calcium oxalate dihydrate (COD) follows the order: sodium citrate >sodium tartrate >Na2EDTA >NaAc. The counterions of carboxylic acids affected the crystallization of CaOx. The ability of both inhibiting the aggregation of COM and inducing the formation of COD follows the sequence: potassium citrate >> sodium citrate >citric acid. Both inhibiting the aggregation of COM and inducing the formation of COD can decrease the probability of the formation of urinary stones. These results may have positive significance in the prevention and cure of urinary stones.
2003, 19(04): 372-375
doi: 10.3866/PKU.WHXB20030420
Abstract:
The EIS of the anodic dissolution process of pure aluminum in an alkaline solution was fitted using an expression of Faradic admittance previously proposed by Cao[11-12], based on which the mechanism of the process was proposed. The results show that the capacitive loop in low frequency region of EIS is caused by the reaction of Al (ss), and the inductive loop in middle frequency region is caused by the reaction of Al(OH)ads. The time constants of Faradic admittance τ1 and τ2 mean the converting time of unit species Al(ss) and Al(OH)ads on unit bare surface site. Generally, τ1 and τ2 both decrease with the increase of the potential E.τ1 >0, τ2 >0, satisfy the conditions required by stability, and by Kramers-Kronig transforms as well. g1 and g2 relate to the variation of covering density of reactants Al(ss) and Al(OH)ads. g1< 0 indicates that the aluminum surface tends to be passive when the potential increases.
The EIS of the anodic dissolution process of pure aluminum in an alkaline solution was fitted using an expression of Faradic admittance previously proposed by Cao[11-12], based on which the mechanism of the process was proposed. The results show that the capacitive loop in low frequency region of EIS is caused by the reaction of Al (ss), and the inductive loop in middle frequency region is caused by the reaction of Al(OH)ads. The time constants of Faradic admittance τ1 and τ2 mean the converting time of unit species Al(ss) and Al(OH)ads on unit bare surface site. Generally, τ1 and τ2 both decrease with the increase of the potential E.τ1 >0, τ2 >0, satisfy the conditions required by stability, and by Kramers-Kronig transforms as well. g1 and g2 relate to the variation of covering density of reactants Al(ss) and Al(OH)ads. g1< 0 indicates that the aluminum surface tends to be passive when the potential increases.
2003, 19(04): 376-379
doi: 10.3866/PKU.WHXB20030421
Abstract:
An efficient method for separating thin-long carbon nanotubes (CNTs)from carbon fibers is presented. The process involves grinding, dispersion, flocculating deposition and filtration treatments. SEM, TEM and TGA were used to evaluate the purification effect. The as-prepared CNTs specimen consists of large amounts of thin-long entangled CNTs that are 10～20 nm in outer diameter and some larger carbon fibers with diameters of more than 100 nm. After grinded, carbon fibers can be broken, while thin-long CNTs are undamaged. Dispersed in a water/surfactant solution under ultra-sonic treatment, most pieces of fibers and carbonaceous impurity were left suspended in a kinetically stable colloidal solution, while many thin-long CNTs flocculated into agglomerates and settled down. Most CNTs were extracted from the suspension as flocculated agglomerates leaving pieces of carbon fibers and other carbonaceous impurity in the filtrate. The purification mechanism is based on the difference of tensile strength and dispersibility of thin-long CNTs with that of carbon fibers.
An efficient method for separating thin-long carbon nanotubes (CNTs)from carbon fibers is presented. The process involves grinding, dispersion, flocculating deposition and filtration treatments. SEM, TEM and TGA were used to evaluate the purification effect. The as-prepared CNTs specimen consists of large amounts of thin-long entangled CNTs that are 10～20 nm in outer diameter and some larger carbon fibers with diameters of more than 100 nm. After grinded, carbon fibers can be broken, while thin-long CNTs are undamaged. Dispersed in a water/surfactant solution under ultra-sonic treatment, most pieces of fibers and carbonaceous impurity were left suspended in a kinetically stable colloidal solution, while many thin-long CNTs flocculated into agglomerates and settled down. Most CNTs were extracted from the suspension as flocculated agglomerates leaving pieces of carbon fibers and other carbonaceous impurity in the filtrate. The purification mechanism is based on the difference of tensile strength and dispersibility of thin-long CNTs with that of carbon fibers.
2003, 19(04): 380-384
doi: 10.3866/PKU.WHXB20030422
Abstract:
The influences of methanol on the performances of Pt/C and CoPcTc(cobalt of tetracarboxyl phthalocyanine)/C heat-treated at 800 ℃ for oxygen reduction reaction(ORR) were studied and compared. The results showed that for Pt/C electrocatalyst methanol oxidation and ORR occurred with no apparent interaction above 0.64 V and below 0.18 V vs SCE. But in the range of 0.18 to 0.64 V, methanol adversely affects the performance of Pt/C for ORR. The methanol had no effect on the performance of CoPcTc/C heat-treated at 800 ℃ for ORR. Thus CoPcTc/C heat-treated at 800 ℃ is a promising catalyst for ORR with higher activity and od methanol-tolerant ability.
The influences of methanol on the performances of Pt/C and CoPcTc(cobalt of tetracarboxyl phthalocyanine)/C heat-treated at 800 ℃ for oxygen reduction reaction(ORR) were studied and compared. The results showed that for Pt/C electrocatalyst methanol oxidation and ORR occurred with no apparent interaction above 0.64 V and below 0.18 V vs SCE. But in the range of 0.18 to 0.64 V, methanol adversely affects the performance of Pt/C for ORR. The methanol had no effect on the performance of CoPcTc/C heat-treated at 800 ℃ for ORR. Thus CoPcTc/C heat-treated at 800 ℃ is a promising catalyst for ORR with higher activity and od methanol-tolerant ability.
