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2007 Volume 23 Issue 5
2007, 23(05):
Abstract:
2007, 23(05): 625-629
doi: 10.1016/S1872-1508(07)60038-2
Abstract:
Tantalumoxide (Ta2O5) thin filmphotocatalysts were prepared on single crystal Si(110) substrates via sol-gel and spin coating methods. Ta2O5 crystallinity was improved, and the crystal size became larger with the increasing of heat treating temperature. The interface diffusion and reaction of the film were studied by using Auger electron spectroscopy (AES) depth profile and line shape analysis. Diffusion was dominant at the interface layer when the calcination, temperature was below 700 ℃. When the temperature reached 800 ℃, both interface diffusion and reaction occurred. The photocatalytic activity was studied using aqueous salicylic acid as a degradation probe molecule under UV-light irradiation. It was found that Ta2O5/Si filmshowed a photocatalytic activity similar to that of TiO2/Si film.
Tantalumoxide (Ta2O5) thin filmphotocatalysts were prepared on single crystal Si(110) substrates via sol-gel and spin coating methods. Ta2O5 crystallinity was improved, and the crystal size became larger with the increasing of heat treating temperature. The interface diffusion and reaction of the film were studied by using Auger electron spectroscopy (AES) depth profile and line shape analysis. Diffusion was dominant at the interface layer when the calcination, temperature was below 700 ℃. When the temperature reached 800 ℃, both interface diffusion and reaction occurred. The photocatalytic activity was studied using aqueous salicylic acid as a degradation probe molecule under UV-light irradiation. It was found that Ta2O5/Si filmshowed a photocatalytic activity similar to that of TiO2/Si film.
2007, 23(05): 630-634
doi: 10.1016/S1872-1508(07)60039-4
Abstract:
The dimer and trimer of N-(1-naphthyl)-succinimide, NaS, molecules were constructed using a combination method of solvate building and conformational random searching performed in the Sybyl software, and the dimer thus obtained agreed well with the structure of the lowest energy provided by the docking method. Density function theory (DFT) simulation of the dimer of NaS could gain the minimum energy conformation, and the study of the molecular mechanics in high level on the trimer was carried out to obtain the stable conformation of lower energy. The difference between the dominant conformation in solution and the dimer calculated in this study, showed that the intermolecular interaction played an important role in the crystallization process in solution. The result might shed light on the intermolecular interaction of N-(1-naphthyl)-succinimide supermolecules and the mechanism research of crystallization in solution.
The dimer and trimer of N-(1-naphthyl)-succinimide, NaS, molecules were constructed using a combination method of solvate building and conformational random searching performed in the Sybyl software, and the dimer thus obtained agreed well with the structure of the lowest energy provided by the docking method. Density function theory (DFT) simulation of the dimer of NaS could gain the minimum energy conformation, and the study of the molecular mechanics in high level on the trimer was carried out to obtain the stable conformation of lower energy. The difference between the dominant conformation in solution and the dimer calculated in this study, showed that the intermolecular interaction played an important role in the crystallization process in solution. The result might shed light on the intermolecular interaction of N-(1-naphthyl)-succinimide supermolecules and the mechanism research of crystallization in solution.
2007, 23(05): 635-640
doi: 10.1016/S1872-1508(07)60040-0
Abstract:
Second-derivative absorption spectra and steady-state fluorescence quenching were used to investigate the interaction between three anti-inflammatory drugs (NSAIDs), namely, indomethacin, sulindac and tolmetin, with egg phosphatidylcholine (EPC) liposomes, which served as a membrane mimetic system. The absorbance of drugs decreased with the addition of EPC liposomes and no shift was observed in the spectra, which indicated that drug molecules did not move to the less polar media constituted by hydrocarbon, but bound on the surface of phosphatidylcholine bilayer. Drugs had the ability to displace, in a dose-dependent manner, 1-anilino-8-naphthalene-sulfonate (ANS), a fluorescent anionic probe previously bound to the head group of phosphatidylcholine molecules. The existence of drugs in liposomes could inhibit the binding of ANS obviously. These factors suggested that the anti-inflammatory drugs could reach the surface of the bilayer, probably with the negative carboxyl group anchored near the phospholipid headgroup, and with the rest of the molecule buried partly in the membrane and aligned with the phospholipid aliphatic tails. These results provided evidence that NSAIDs reduced the ability of surface-active phospholipids to form a hydrophobic protective layer. The strongest interaction was observed between sulindac and liposomes.
Second-derivative absorption spectra and steady-state fluorescence quenching were used to investigate the interaction between three anti-inflammatory drugs (NSAIDs), namely, indomethacin, sulindac and tolmetin, with egg phosphatidylcholine (EPC) liposomes, which served as a membrane mimetic system. The absorbance of drugs decreased with the addition of EPC liposomes and no shift was observed in the spectra, which indicated that drug molecules did not move to the less polar media constituted by hydrocarbon, but bound on the surface of phosphatidylcholine bilayer. Drugs had the ability to displace, in a dose-dependent manner, 1-anilino-8-naphthalene-sulfonate (ANS), a fluorescent anionic probe previously bound to the head group of phosphatidylcholine molecules. The existence of drugs in liposomes could inhibit the binding of ANS obviously. These factors suggested that the anti-inflammatory drugs could reach the surface of the bilayer, probably with the negative carboxyl group anchored near the phospholipid headgroup, and with the rest of the molecule buried partly in the membrane and aligned with the phospholipid aliphatic tails. These results provided evidence that NSAIDs reduced the ability of surface-active phospholipids to form a hydrophobic protective layer. The strongest interaction was observed between sulindac and liposomes.
2007, 23(05): 641-646
doi: 10.1016/S1872-1508(07)60041-2
Abstract:
A series of mesoporous multicomponent mixed oxide catalysts La-Mn-Ce-O with various (nLa+nMn)/(nLa+nMn+nCe) ratios were prepared by citric acid complexation-organic template decomposition (CAC-OTD) method. For comparison, the sample with the same composition was also prepared by conventional coprecipitation method. The results of N2 adsorption/desorption showed that the samples prepared by CAC-OTD method possessed relatively large specific surface area and uniformpore diameter distribution (3.4-4.4 nm). The results of X-ray diffraction (XRD) identified the formation of La-Ce and Mn-Ce solid solution. No Mn species were detected by XRD. The results of X-ray photoelectron spectroscopy (XPS) showed that there was a strong electronic state interaction betweenMn and Ce species, resulting in the formation of Mn 2p shake-up peak. Such interaction enhanced the transfer of oxygen species from Ce to Mn oxide and therefore increased the redox activity of the samples. The sample with the strongest shake-up peak showed the highest oxidation activity. The results of temperature programmed reduction (TPR) showed that the manganese species in the samples prepared by using CAC-OTD method were easier to be reduced, which was relevant to the oxidation activity of the catalysts. The results of activity evaluation showed that the light-off temperature of the LMC(0.5)-500 sample was about 50 ℃ lower than that of the sample prepared by using coprecipitation method. The samples prepared by using CAC-OTDmethod showed od thermal stability.
A series of mesoporous multicomponent mixed oxide catalysts La-Mn-Ce-O with various (nLa+nMn)/(nLa+nMn+nCe) ratios were prepared by citric acid complexation-organic template decomposition (CAC-OTD) method. For comparison, the sample with the same composition was also prepared by conventional coprecipitation method. The results of N2 adsorption/desorption showed that the samples prepared by CAC-OTD method possessed relatively large specific surface area and uniformpore diameter distribution (3.4-4.4 nm). The results of X-ray diffraction (XRD) identified the formation of La-Ce and Mn-Ce solid solution. No Mn species were detected by XRD. The results of X-ray photoelectron spectroscopy (XPS) showed that there was a strong electronic state interaction betweenMn and Ce species, resulting in the formation of Mn 2p shake-up peak. Such interaction enhanced the transfer of oxygen species from Ce to Mn oxide and therefore increased the redox activity of the samples. The sample with the strongest shake-up peak showed the highest oxidation activity. The results of temperature programmed reduction (TPR) showed that the manganese species in the samples prepared by using CAC-OTD method were easier to be reduced, which was relevant to the oxidation activity of the catalysts. The results of activity evaluation showed that the light-off temperature of the LMC(0.5)-500 sample was about 50 ℃ lower than that of the sample prepared by using coprecipitation method. The samples prepared by using CAC-OTDmethod showed od thermal stability.
2007, 23(05): 647-650
doi: 10.1016/S1872-1508(07)60042-4
Abstract:
The influence of non-isothermal melt crystallization on thermal behavior and morphology of poly-L-lactide (PLLA) was investigated by differential scanning calorimetry (DSC), polarizing micrograph (POM), and scanning electron microscopy (SEM). Crystallization performed at lower cooling rate (2 ℃·min-1) was accompanied by a change of the kinetics around 118 ℃. The glass transition temperature of PLLA decreased with the increase of cooling rate. The crystallinity at the end of crystallization and the size of PLLA spherulites increased with decreasing cooling rate, and PLLA became almost amorphous cooled at a rapid rate of 10 ℃·min-1. PLLA biodegradable material with spherulites structure was obtained by using compression mould and controlling the cooling rates, and spherulites developed rapidly at lower cooling rates. The fracture surfaces of PLLA at low cooling rates were more compacter and smoother, but more brittle, than those at high cooling rates.
The influence of non-isothermal melt crystallization on thermal behavior and morphology of poly-L-lactide (PLLA) was investigated by differential scanning calorimetry (DSC), polarizing micrograph (POM), and scanning electron microscopy (SEM). Crystallization performed at lower cooling rate (2 ℃·min-1) was accompanied by a change of the kinetics around 118 ℃. The glass transition temperature of PLLA decreased with the increase of cooling rate. The crystallinity at the end of crystallization and the size of PLLA spherulites increased with decreasing cooling rate, and PLLA became almost amorphous cooled at a rapid rate of 10 ℃·min-1. PLLA biodegradable material with spherulites structure was obtained by using compression mould and controlling the cooling rates, and spherulites developed rapidly at lower cooling rates. The fracture surfaces of PLLA at low cooling rates were more compacter and smoother, but more brittle, than those at high cooling rates.
2007, 23(05): 651-654
doi: 10.3866/PKU.WHXB20070506
Abstract:
The different structures of PdOH2, PdOH, and PdO were optimized by the relativistic effective core potential (RECP) and the density functional method B3LYP. The results showed that Pd and H2O of stable Pd-OH2 molecule were not in the same plane, and the bond length (RPdO) was 0.2283 nm. For PdOH molecule, the ground state was 2A', the structure parameters RPdO, ROH, and ∠PdOH were 0.1965 nm, 0.0968 nm, and 110.186°, respectively; The
ground state of PdO was 3Π, and the bond length was 0.1858 nm. Furthermore, the thermodynamic functions of PdOH2, PdOH, and PdO were also calculated according to electronic-vibration approximation, and based on this results, the relationship of the equilibrium pressures with temperatures was obtained. From the results, it was deduced that the poisoning effect of H2O was due to the adsorption of O and OH dissociated from H2O on palladium surface.
The different structures of PdOH2, PdOH, and PdO were optimized by the relativistic effective core potential (RECP) and the density functional method B3LYP. The results showed that Pd and H2O of stable Pd-OH2 molecule were not in the same plane, and the bond length (RPdO) was 0.2283 nm. For PdOH molecule, the ground state was 2A', the structure parameters RPdO, ROH, and ∠PdOH were 0.1965 nm, 0.0968 nm, and 110.186°, respectively; The
ground state of PdO was 3Π, and the bond length was 0.1858 nm. Furthermore, the thermodynamic functions of PdOH2, PdOH, and PdO were also calculated according to electronic-vibration approximation, and based on this results, the relationship of the equilibrium pressures with temperatures was obtained. From the results, it was deduced that the poisoning effect of H2O was due to the adsorption of O and OH dissociated from H2O on palladium surface.
2007, 23(05): 655-658
doi: 10.3866/PKU.WHXB20070507
Abstract:
Pure spinel Co3O4 was successfully synthesized by solvothermal method with polyethylene glycol as dispersant. The shape and size of the final product can be controlled by adjusting the solvent ratio of n-butanol to water. The interimproduct was characterized by IR, X-ray powder diffraction (XRD), TG-DTA, and transmission electron microscope (TEM). The results showed that the formation mechanism of Co3O4 included two steps: Co (OH)2-x·(NO3)x formed in solution was oxidated into Co0.81IICo0.19III(OH)2.11·(NO3)0.08·0.43H2O firstly, and then transformed to Co3O4.
Pure spinel Co3O4 was successfully synthesized by solvothermal method with polyethylene glycol as dispersant. The shape and size of the final product can be controlled by adjusting the solvent ratio of n-butanol to water. The interimproduct was characterized by IR, X-ray powder diffraction (XRD), TG-DTA, and transmission electron microscope (TEM). The results showed that the formation mechanism of Co3O4 included two steps: Co (OH)2-x·(NO3)x formed in solution was oxidated into Co0.81IICo0.19III(OH)2.11·(NO3)0.08·0.43H2O firstly, and then transformed to Co3O4.
2007, 23(05): 659-663
doi: 10.3866/PKU.WHXB20070508
Abstract:
The CeO2 and Ce-Sn-O complex oxides were prepared by sol-gel method using citric acid and glucose as complexing agents, respectively. The complex oxides were characterized by XRD, TPR, FT-IR, BET, and TEM, and their catalytic activities for the combustion of methane were evaluted. The results showed that the Ce-Sn-O complex oxide, which used glucose as complexing agent, had lower complete methane conversion temperature and larger specific surface area. The TEManalysis of the Ce-Sn-O complex oxide, which used glucose as complexing agent, revealed that the particles had a mean size of 14 nm and better dispersity, while the catalyst which used citric acid as complexing agent was seriously agglomerated.
The CeO2 and Ce-Sn-O complex oxides were prepared by sol-gel method using citric acid and glucose as complexing agents, respectively. The complex oxides were characterized by XRD, TPR, FT-IR, BET, and TEM, and their catalytic activities for the combustion of methane were evaluted. The results showed that the Ce-Sn-O complex oxide, which used glucose as complexing agent, had lower complete methane conversion temperature and larger specific surface area. The TEManalysis of the Ce-Sn-O complex oxide, which used glucose as complexing agent, revealed that the particles had a mean size of 14 nm and better dispersity, while the catalyst which used citric acid as complexing agent was seriously agglomerated.
2007, 23(05): 664-670
doi: 10.3866/PKU.WHXB20070509
Abstract:
A series of Co-M (M=La, Ce, Fe, Mn, Cu, Cr) composite oxide catalysts were prepared by co-precipitation method and tested in catalytic decomposition of N2O. The results showed that Co-Ce composite oxide with Ce/Co molar ratio of 0.05 (CoCe0.05 catalyst) performed best in the N2O decomposition reaction. The presence of NO and O2 in the feed affected the decomposition rate of N2O over CoCe0.05 by adsorption of nitrate or nitrite species on the active site. The XRD, BET, O2-TPD, and H2-TPR methods were used to characterize the Co-Mmixed catalysts. The analysis results showed that the redox ability of the active site (Co2+) was very important for the decomposition of N2O over these catalysts. The surface decomposition of N2O was accompanied by the oxidation of Co2+ to Co3+, and the desorption of surface oxygen was accompanied by the reduction of Co3+ to Co2+. The addition of other transition metal oxides except CeO2 lowered the redox ability of Co3 +/Co2 +, and thus lowered the catalytic activities for the decomposition of N2O. In addition, the rate-determining step of the catalytic N2O decomposition was also influenced by the addition of various metal oxides.
A series of Co-M (M=La, Ce, Fe, Mn, Cu, Cr) composite oxide catalysts were prepared by co-precipitation method and tested in catalytic decomposition of N2O. The results showed that Co-Ce composite oxide with Ce/Co molar ratio of 0.05 (CoCe0.05 catalyst) performed best in the N2O decomposition reaction. The presence of NO and O2 in the feed affected the decomposition rate of N2O over CoCe0.05 by adsorption of nitrate or nitrite species on the active site. The XRD, BET, O2-TPD, and H2-TPR methods were used to characterize the Co-Mmixed catalysts. The analysis results showed that the redox ability of the active site (Co2+) was very important for the decomposition of N2O over these catalysts. The surface decomposition of N2O was accompanied by the oxidation of Co2+ to Co3+, and the desorption of surface oxygen was accompanied by the reduction of Co3+ to Co2+. The addition of other transition metal oxides except CeO2 lowered the redox ability of Co3 +/Co2 +, and thus lowered the catalytic activities for the decomposition of N2O. In addition, the rate-determining step of the catalytic N2O decomposition was also influenced by the addition of various metal oxides.
2007, 23(05): 671-675
doi: 10.3866/PKU.WHXB20070510
Abstract:
Theoretical investigations of conducting molecular wire of oli -polyphenylene molecules under external electronic field were carried out using ab initio Hartree-Fock method with 6-31G* basis set. The electric field dependence of the molecular geometry, electronic structure, the spatial distribution, and the energy level of the frontier orbitals of the molecular wire was revealed. The torsion angle deviation was a function of square of electric field. When the external electric field increased, the torsion angles became smaller, the single bonds became shorter, and the molecular configuration tended to be more planar. All these features made the molecular wire more conjugated. The molecular electronic structure was sensitive to the electric field as well. With increasing electric field, the HOMO-LUMO gap decreased. Moreover, the spatial distribution of LUMO moved to the high potential end, whereas HOMO to the low potential end. Furthermore, the polyphenylene (PP) molecule with sulfur atoms bridged between two ld electrodes was studied by non-equilibrium Green's function formalism to further understand the electron transport of molecular wire under external electric field.
Theoretical investigations of conducting molecular wire of oli -polyphenylene molecules under external electronic field were carried out using ab initio Hartree-Fock method with 6-31G* basis set. The electric field dependence of the molecular geometry, electronic structure, the spatial distribution, and the energy level of the frontier orbitals of the molecular wire was revealed. The torsion angle deviation was a function of square of electric field. When the external electric field increased, the torsion angles became smaller, the single bonds became shorter, and the molecular configuration tended to be more planar. All these features made the molecular wire more conjugated. The molecular electronic structure was sensitive to the electric field as well. With increasing electric field, the HOMO-LUMO gap decreased. Moreover, the spatial distribution of LUMO moved to the high potential end, whereas HOMO to the low potential end. Furthermore, the polyphenylene (PP) molecule with sulfur atoms bridged between two ld electrodes was studied by non-equilibrium Green's function formalism to further understand the electron transport of molecular wire under external electric field.
2007, 23(05): 676-682
doi: 10.3866/PKU.WHXB20070511
Abstract:
Density functional theory (DFT) B3LYP calculations were performed on end-on linear and bent FeN2 structures using 6-311+G(d) basis sets. The geometric structures, bonding properties, natural electronic configuration, natural charges, and total spin densities were studied. The linear structure was more stable than the bent one. Lots of electronic states were investigated and compared with earlier calculations at high level ab initio molecular orbital and DFT methods. The lowest state was 13∑- for L-FeN2 but its energy was 21.6 kJ·mol -1 higher than the ground state reactants Fe(a5D) and N2(1∑+g) by 21.6 kJ·mol-1. The results showed that the nitrogen molecule was activated very little by the excited states Fe atom, the bond length of N2 in L-FeN2 complex elongated less than 7 pm in all states, and adsorbed with ground state by the van der Waals interaction force.
Density functional theory (DFT) B3LYP calculations were performed on end-on linear and bent FeN2 structures using 6-311+G(d) basis sets. The geometric structures, bonding properties, natural electronic configuration, natural charges, and total spin densities were studied. The linear structure was more stable than the bent one. Lots of electronic states were investigated and compared with earlier calculations at high level ab initio molecular orbital and DFT methods. The lowest state was 13∑- for L-FeN2 but its energy was 21.6 kJ·mol -1 higher than the ground state reactants Fe(a5D) and N2(1∑+g) by 21.6 kJ·mol-1. The results showed that the nitrogen molecule was activated very little by the excited states Fe atom, the bond length of N2 in L-FeN2 complex elongated less than 7 pm in all states, and adsorbed with ground state by the van der Waals interaction force.
2007, 23(05): 683-687
doi: 10.1016/S1872-1508(07)60043-6
Abstract:
According to the relationship between gravitational potential and electrostatic potential, and the physical meaning of the contrastive mass-to-electricity (mass of per unit electricity) Sr, the authors studied the relationship between ionic radius r and Sr. For the positive ions with same electronic configuration r varied directly with lgSr, and for negative ions with same electronic configuration, the relationship between r and Sr conformed to the mathematical model of Michealis-Menten. With regression analysis, ionic radii of 94 elements, among which there were 108 radii of positive ions and 16 radii of negative ions, could be fitted. The correlation coefficient R and test of significance (F) showed that r was closely related to Sr. The average absolute error of the 102 radii of positive ions was only 0.9 pm with the representative radii of ions, the relative error was 1.08%. This led to a set of od ionic radius values. It is a new path of calculating ionic radius that contains complex ions.
According to the relationship between gravitational potential and electrostatic potential, and the physical meaning of the contrastive mass-to-electricity (mass of per unit electricity) Sr, the authors studied the relationship between ionic radius r and Sr. For the positive ions with same electronic configuration r varied directly with lgSr, and for negative ions with same electronic configuration, the relationship between r and Sr conformed to the mathematical model of Michealis-Menten. With regression analysis, ionic radii of 94 elements, among which there were 108 radii of positive ions and 16 radii of negative ions, could be fitted. The correlation coefficient R and test of significance (F) showed that r was closely related to Sr. The average absolute error of the 102 radii of positive ions was only 0.9 pm with the representative radii of ions, the relative error was 1.08%. This led to a set of od ionic radius values. It is a new path of calculating ionic radius that contains complex ions.
2007, 23(05): 688-694
doi: 10.1016/S1872-1508(07)60044-8
Abstract:
The new method developed by Li et al. is used to calculate the energy between two colloidal particles, which can break through the limit that the surface potential to be taken as a constant as electrolyte concentration changes in the classic DLVO theory. Also in this research, both the Boltzmann theory of kinetic energy of colloidal particles and Monte Carlo method are used to simulate the movement of colloidal particles, and the inelastic collision theory is used to solve the problem of effective collision probability. By improving the DDA model, the relationship between the cohesion efficiency and the electrolyte concentration in gravity field is established successfully. The results showed that: (1) the curves of the fractal dimension change with electrolyte concentration as gravity field presence were quite different from that as the gravity field absence. The curves were “L”-shaped as the gravity field absence; however, as the gravity field presence, the curves were“S”-shaped. (2) As gravity field presence, the slow aggregating process can be divided into two sections: the sensitive and non-sensitive sections to electrolyte concentration. In the sensitive section, an inflexion of electrolyte concentration was found. (3) As gravity field absence, the fractal dimension of aggregates was 1.86±0.01 for different size of colloidal particles as the aggregating process was fast under a higher electrolyte concentration condition. Comparatively, for a slow aggregating process of low electrolyte concentration, the fractal dimension increased to 2.01±0.02. However, under the same low electrolyte concentration, the fractal dimension of aggregates approached 3 as the gravity field presence.
The new method developed by Li et al. is used to calculate the energy between two colloidal particles, which can break through the limit that the surface potential to be taken as a constant as electrolyte concentration changes in the classic DLVO theory. Also in this research, both the Boltzmann theory of kinetic energy of colloidal particles and Monte Carlo method are used to simulate the movement of colloidal particles, and the inelastic collision theory is used to solve the problem of effective collision probability. By improving the DDA model, the relationship between the cohesion efficiency and the electrolyte concentration in gravity field is established successfully. The results showed that: (1) the curves of the fractal dimension change with electrolyte concentration as gravity field presence were quite different from that as the gravity field absence. The curves were “L”-shaped as the gravity field absence; however, as the gravity field presence, the curves were“S”-shaped. (2) As gravity field presence, the slow aggregating process can be divided into two sections: the sensitive and non-sensitive sections to electrolyte concentration. In the sensitive section, an inflexion of electrolyte concentration was found. (3) As gravity field absence, the fractal dimension of aggregates was 1.86±0.01 for different size of colloidal particles as the aggregating process was fast under a higher electrolyte concentration condition. Comparatively, for a slow aggregating process of low electrolyte concentration, the fractal dimension increased to 2.01±0.02. However, under the same low electrolyte concentration, the fractal dimension of aggregates approached 3 as the gravity field presence.
2007, 23(05): 695-700
doi: 10.3866/PKU.WHXB20070514
Abstract:
The solubilities of rubidium bromide and cesium bromide in water, water+ methanol, and water+ethanol were measured by using accurate analytical method at different temperatures. And refractive indices were determined for the two ternary systems in saturated solution with varied salt concentrations as well. In all cases, the presence of either methanol or ethanol significantly reduced the solubilities of rubidium bromide and cesium bromide in aqueous solution, but the refractive indices reduced with the increasing mass fraction of either methanol or ethanol. The solubilities of the saturated solutions were fitted via polynomial equations as a function of the mass fraction of methanol or ethanol, and the salting-out ratios of RbBr and CsBr by methanol and ethanol were also obtained.
The solubilities of rubidium bromide and cesium bromide in water, water+ methanol, and water+ethanol were measured by using accurate analytical method at different temperatures. And refractive indices were determined for the two ternary systems in saturated solution with varied salt concentrations as well. In all cases, the presence of either methanol or ethanol significantly reduced the solubilities of rubidium bromide and cesium bromide in aqueous solution, but the refractive indices reduced with the increasing mass fraction of either methanol or ethanol. The solubilities of the saturated solutions were fitted via polynomial equations as a function of the mass fraction of methanol or ethanol, and the salting-out ratios of RbBr and CsBr by methanol and ethanol were also obtained.
2007, 23(05): 701-708
doi: 10.3866/PKU.WHXB20070515
Abstract:
A yellowish Ti1-xSyO2 photocatalyst exhibiting high activity in wide light spectrum range was prepared by acid catalyzed hydrolysis method. Photocatalytic activity was investigated through the photocatalytic degradation of phenol under UV, artificial visible (Vis) and solar light irradiation, respectively. XPS, DRS, XRD, FT-IR, SEM, and N2 adsorption were used for catalyst characterization. The results showed that cationic S6 + was incorporated into TiO2 lattice and substitutes a part of Ti4+. Ti1-xSyO2 with optimum S-doping exhibited the highest activity in both Vis and UV regions. The new band-gap formed by doped-S could induce a second adsorption edge (450-550 nm) which could be excited by Vis irradiation and induce Vis activity. Under UV irradiation, the new formed band-energy could accept holes generated by bulk TiO2 and form a composite semiconductor structure, then improve hole-electron pairs separation. In addition, doped-S also benefited the dispersity of TiO2, increased SBET and retarded phase transformation.
A yellowish Ti1-xSyO2 photocatalyst exhibiting high activity in wide light spectrum range was prepared by acid catalyzed hydrolysis method. Photocatalytic activity was investigated through the photocatalytic degradation of phenol under UV, artificial visible (Vis) and solar light irradiation, respectively. XPS, DRS, XRD, FT-IR, SEM, and N2 adsorption were used for catalyst characterization. The results showed that cationic S6 + was incorporated into TiO2 lattice and substitutes a part of Ti4+. Ti1-xSyO2 with optimum S-doping exhibited the highest activity in both Vis and UV regions. The new band-gap formed by doped-S could induce a second adsorption edge (450-550 nm) which could be excited by Vis irradiation and induce Vis activity. Under UV irradiation, the new formed band-energy could accept holes generated by bulk TiO2 and form a composite semiconductor structure, then improve hole-electron pairs separation. In addition, doped-S also benefited the dispersity of TiO2, increased SBET and retarded phase transformation.
2007, 23(05): 709-712
doi: 10.3866/PKU.WHXB20070516
Abstract:
The dielectric relaxation measurements on binary mixtures of esters (methyl acrylate, ethyl acrylate, and butyl acrylate) with phenol derivatives (p-cresol, p-chlorophenol, and 2,4-dichlorophenol) were carried out at different concentrations at 303 K using the time domain reflectometry (TDR) over the frequency range from10 MHz to 20 GHz. The Kirkwood correlation factor and excess inverse relaxation time were determined and discussed to yield information on the molecular interactions of the systems. The relaxation time increased with increasing concentration of phenols and increasing chain length of esters. The excess inverse relaxation time values were negative for all the systems, which indicated the solute-solvent interaction existing between esters and phenols producing a field in such a way that the effective dipole rotation was hindered.
The dielectric relaxation measurements on binary mixtures of esters (methyl acrylate, ethyl acrylate, and butyl acrylate) with phenol derivatives (p-cresol, p-chlorophenol, and 2,4-dichlorophenol) were carried out at different concentrations at 303 K using the time domain reflectometry (TDR) over the frequency range from10 MHz to 20 GHz. The Kirkwood correlation factor and excess inverse relaxation time were determined and discussed to yield information on the molecular interactions of the systems. The relaxation time increased with increasing concentration of phenols and increasing chain length of esters. The excess inverse relaxation time values were negative for all the systems, which indicated the solute-solvent interaction existing between esters and phenols producing a field in such a way that the effective dipole rotation was hindered.
2007, 23(05): 713-716
doi: 10.3866/PKU.WHXB20070517
Abstract:
Defective LB film was used as model for injured renal epithelial membrane to induce the growth of calcium oxalate monohydrate (COM) crystals, which was the major inorganic component found in renal calculi. After the LB film of dipalmitoylphosphatidylcholine (DPPC) was treated by 2.5 mmol·L-1 potassium oxalate, the structural differentiation between liquid expanded (LE) phase and liquid condensed (LC) phase in LB film was strengthened and circular defects appeared. These circular defects were proved by atomic force microscopy (AFM). Such circular defects could induce ring-shaped patterns of COM crystals. In comparison, the LB films without pretreatment by potassium oxalate only induced randomly growth of COMcrystals.
Defective LB film was used as model for injured renal epithelial membrane to induce the growth of calcium oxalate monohydrate (COM) crystals, which was the major inorganic component found in renal calculi. After the LB film of dipalmitoylphosphatidylcholine (DPPC) was treated by 2.5 mmol·L-1 potassium oxalate, the structural differentiation between liquid expanded (LE) phase and liquid condensed (LC) phase in LB film was strengthened and circular defects appeared. These circular defects were proved by atomic force microscopy (AFM). Such circular defects could induce ring-shaped patterns of COM crystals. In comparison, the LB films without pretreatment by potassium oxalate only induced randomly growth of COMcrystals.
2007, 23(05): 717-722
doi: 10.3866/PKU.WHXB20070518
Abstract:
The surface organic modification of nanosized CaCO3 with palmitic acid was carried out. The prepared samples were characterized by SEM, TEM, XRD, FTIR, and TG-DTG techniques. A comparative study on the crystal structure and thermal decomposition characteristics of nanosized CaCO3, modified nanosized CaCO3, and microsized CaCO3 was made. According to the spectra of FTIR, it was inferred that the chemical binding and the physical adsorption between palmitic acid and nanosized CaCO3 have happened during the modification reaction. The results also revealed that the infrared absorption peaks of C—O bond of modified and unmodified nanosized CaCO3 shifted to a higher frequency by 35 cm-1 compared with that of microsized CaCO3. The mechanism of blue shift in nanosized CaCO3 was discussed, and it was believed that crystalline electric field effect and size effect influenced their infrared spectra. TG-DTG analysis showed that nanosized CaCO3, modified nanosized CaCO3, and microsized CaCO3 decomposed at 735.0, 764.7, and 775.6 ℃, respectively. The decrease of the decomposition temperature was supposed to be related to the lattice expansion and crystallographic deformation of nanosized CaCO3.
The surface organic modification of nanosized CaCO3 with palmitic acid was carried out. The prepared samples were characterized by SEM, TEM, XRD, FTIR, and TG-DTG techniques. A comparative study on the crystal structure and thermal decomposition characteristics of nanosized CaCO3, modified nanosized CaCO3, and microsized CaCO3 was made. According to the spectra of FTIR, it was inferred that the chemical binding and the physical adsorption between palmitic acid and nanosized CaCO3 have happened during the modification reaction. The results also revealed that the infrared absorption peaks of C—O bond of modified and unmodified nanosized CaCO3 shifted to a higher frequency by 35 cm-1 compared with that of microsized CaCO3. The mechanism of blue shift in nanosized CaCO3 was discussed, and it was believed that crystalline electric field effect and size effect influenced their infrared spectra. TG-DTG analysis showed that nanosized CaCO3, modified nanosized CaCO3, and microsized CaCO3 decomposed at 735.0, 764.7, and 775.6 ℃, respectively. The decrease of the decomposition temperature was supposed to be related to the lattice expansion and crystallographic deformation of nanosized CaCO3.
2007, 23(05): 723-727
doi: 10.3866/PKU.WHXB20070519
Abstract:
Underpotential deposition (upd) of rutheniumon a platinumelectrode was adopted to obtain a submonolayer of ruthenium on platinum surface. Ru coverage was evaluated according to the change of the hydrogen desorption area in the cyclic voltammograms (CV) of Pt electrodes before and after upd-Ru modification in 0.5 mol·L-1 H2SO4. The effects
of the potential for formation of upd-Ru and coverage of upd-Ru adtoms on methanol oxidation were investigated and analyzed. It was shown that Ru adatoms could be underpotentially deposited on a platinum surface. The submonolayer of upd-Ru on the Pt electrode could enhance methanol electrooxidation several times as large as that on the pure Pt electrode. It was also shown that as long as the amount of upd-Ru adatoms was controlled in a proper range, upd-Ru deposits would enhance the methanol oxidation independently of the deposition potential. The catalytic activity of binary Pt-Ru catalysts for methanol electrooxidation was highly associated with the surface composition of Pt and Ru, but was free of whether Pt-Ru deposits appear in a formof alloy, bimetallic compounds, adatoms, or something else.
Underpotential deposition (upd) of rutheniumon a platinumelectrode was adopted to obtain a submonolayer of ruthenium on platinum surface. Ru coverage was evaluated according to the change of the hydrogen desorption area in the cyclic voltammograms (CV) of Pt electrodes before and after upd-Ru modification in 0.5 mol·L-1 H2SO4. The effects
of the potential for formation of upd-Ru and coverage of upd-Ru adtoms on methanol oxidation were investigated and analyzed. It was shown that Ru adatoms could be underpotentially deposited on a platinum surface. The submonolayer of upd-Ru on the Pt electrode could enhance methanol electrooxidation several times as large as that on the pure Pt electrode. It was also shown that as long as the amount of upd-Ru adatoms was controlled in a proper range, upd-Ru deposits would enhance the methanol oxidation independently of the deposition potential. The catalytic activity of binary Pt-Ru catalysts for methanol electrooxidation was highly associated with the surface composition of Pt and Ru, but was free of whether Pt-Ru deposits appear in a formof alloy, bimetallic compounds, adatoms, or something else.
2007, 23(05): 728-732
doi: 10.3866/PKU.WHXB20070520
Abstract:
The preparation process of nano-aluminum hydroxide sol by peptizing aluminum hydroxide precipitate produced via carbonation of sodium aluminate was investigated. The reaction, in which the sodium aluminate solution was dropwise added into abundant sodium bicarbonate solution, was analyzed. The XRD results indicated that the amorphous aluminum hydroxide precipitates transformed into pseudo-boehmite because the precipitates dissolved and recrystallized into pseudo-boehmite crystals during the sol preparation. Furthermore, the increase of absorption at 270 nm in the UV spectra indicated the presence of Al(OH)3-6 ion during the sodium aluminate solution with caustic ratio of 1.7 was neutralized to 1.3. Comparing with the absorption spectrum of the structure of six hydroxyl groups around Al atom, it could be concluded that the coordination numbers of Al atom with hydroxyl groups changed from four to six during the decomposition of sodium aluminate solution. Besides, the morphology of particles in the sol was also influenced by surfactants and acids used.
The preparation process of nano-aluminum hydroxide sol by peptizing aluminum hydroxide precipitate produced via carbonation of sodium aluminate was investigated. The reaction, in which the sodium aluminate solution was dropwise added into abundant sodium bicarbonate solution, was analyzed. The XRD results indicated that the amorphous aluminum hydroxide precipitates transformed into pseudo-boehmite because the precipitates dissolved and recrystallized into pseudo-boehmite crystals during the sol preparation. Furthermore, the increase of absorption at 270 nm in the UV spectra indicated the presence of Al(OH)3-6 ion during the sodium aluminate solution with caustic ratio of 1.7 was neutralized to 1.3. Comparing with the absorption spectrum of the structure of six hydroxyl groups around Al atom, it could be concluded that the coordination numbers of Al atom with hydroxyl groups changed from four to six during the decomposition of sodium aluminate solution. Besides, the morphology of particles in the sol was also influenced by surfactants and acids used.
2007, 23(05): 733-737
doi: 10.3866/PKU.WHXB20070521
Abstract:
The geometric configurations, electronic structures and vibrational frequencies of the (BCO)+n (n=1-12) were calculated with B3LYP method at 6-31G*level. The result revealed that the ground states of the clusters favor three- and five-member rings and disfavored four-and six-member rings in the framework, in which all the carbonyls were terminal. Energy analysis exhibited that the (BCO)+n with odd n was more stable than that with even n.
The geometric configurations, electronic structures and vibrational frequencies of the (BCO)+n (n=1-12) were calculated with B3LYP method at 6-31G*level. The result revealed that the ground states of the clusters favor three- and five-member rings and disfavored four-and six-member rings in the framework, in which all the carbonyls were terminal. Energy analysis exhibited that the (BCO)+n with odd n was more stable than that with even n.
2007, 23(05): 738-742
doi: 10.3866/PKU.WHXB20070522
Abstract:
Y-doped β-Ni(OH)2 and α-Ni(OH)2 materials were synthesized, and the influences of Y on the structure, morphology and high-temperature electrochemical characteristics of the two kinds of materials were studied through XRD, TEM, CV, and charging/discharging tests. The results indicated that yttrium improved high-temperature electrochemical performances of β-Ni(OH)2 and α-Ni(OH)2 materials by the same mechanism that the charge efficiency was enhanced through the increase of oxygen evolution overpotentials. However, further efforts are still necessary to improve the phase stability of α-Ni(OH)2 at high temperatures.
Y-doped β-Ni(OH)2 and α-Ni(OH)2 materials were synthesized, and the influences of Y on the structure, morphology and high-temperature electrochemical characteristics of the two kinds of materials were studied through XRD, TEM, CV, and charging/discharging tests. The results indicated that yttrium improved high-temperature electrochemical performances of β-Ni(OH)2 and α-Ni(OH)2 materials by the same mechanism that the charge efficiency was enhanced through the increase of oxygen evolution overpotentials. However, further efforts are still necessary to improve the phase stability of α-Ni(OH)2 at high temperatures.
2007, 23(05): 743-745
doi: 10.3866/PKU.WHXB20070523
Abstract:
Planar coordinate carbon-centered transition-metal hydrometal complexes MnHnC (M=Ni, Pd, and Pt for n=4, and M=Cu, Ag, and Au for n=5) were predicted to be stable species by density functional theory. The result showed that the planar tetracoordinate carbon centers in M4H4C systems followed the octet rule while the planar pentacoordinate carbon centers in M5H5C form partially ionic bonds with their transition metal ligands. The possibility to form one-dimensional M2n+2H2n+2Cn or multi-dimensional chains containing double or multi planar tetracoordinate carbons was also investigated.
Planar coordinate carbon-centered transition-metal hydrometal complexes MnHnC (M=Ni, Pd, and Pt for n=4, and M=Cu, Ag, and Au for n=5) were predicted to be stable species by density functional theory. The result showed that the planar tetracoordinate carbon centers in M4H4C systems followed the octet rule while the planar pentacoordinate carbon centers in M5H5C form partially ionic bonds with their transition metal ligands. The possibility to form one-dimensional M2n+2H2n+2Cn or multi-dimensional chains containing double or multi planar tetracoordinate carbons was also investigated.
2007, 23(05): 746-750
doi: 10.3866/PKU.WHXB20070524
Abstract:
The ground states of methyl vinyl siloxane under different intense electric fields ranging from0 to 0.04 a.u. were optimized using density functional theory DFT/B3P86 at 6-311++G(d,p) level. The excitation energies and oscillator strengths under the same intense applied electric fields were calculated employing the revised hybrid CIS-DFT method. The result showed that the electronic state, molecular geometry, total energy, dipole moment, and excitation energy were strongly dependent on the applied electric field. As the electric field changed from 0 to 0.03 a. u., the bond length of Si-O decreased because of the charge transfer induced by the applied electric field. Further increase of the electric field resulted in an increase of the bond length. The dipole moment of the ground state increased sharply with the applied field strength. As the electric field increased to 0.02 a.u., the total energy of the molecule reached the maximum -483.5393952 a.u.. Further increase of the electric field strengths resulted in a decrease of the total energy. The excitation energies of the first five excited states of methyl vinyl siloxane decreased as the increase of the applied electric field, indicating that the molecule was easy to be excited under electric field and hence could be easily dissociated.
The ground states of methyl vinyl siloxane under different intense electric fields ranging from0 to 0.04 a.u. were optimized using density functional theory DFT/B3P86 at 6-311++G(d,p) level. The excitation energies and oscillator strengths under the same intense applied electric fields were calculated employing the revised hybrid CIS-DFT method. The result showed that the electronic state, molecular geometry, total energy, dipole moment, and excitation energy were strongly dependent on the applied electric field. As the electric field changed from 0 to 0.03 a. u., the bond length of Si-O decreased because of the charge transfer induced by the applied electric field. Further increase of the electric field resulted in an increase of the bond length. The dipole moment of the ground state increased sharply with the applied field strength. As the electric field increased to 0.02 a.u., the total energy of the molecule reached the maximum -483.5393952 a.u.. Further increase of the electric field strengths resulted in a decrease of the total energy. The excitation energies of the first five excited states of methyl vinyl siloxane decreased as the increase of the applied electric field, indicating that the molecule was easy to be excited under electric field and hence could be easily dissociated.
2007, 23(05): 751-756
doi: 10.3866/PKU.WHXB20070525
Abstract:
Field-free alignment of N2 molecule induced by laser pulse with intensity of 1.5×1014 W·cm-2 and duration of 50 fs was investigated by solving time-dependent Schrodinger equation numerically. The results showed that the alignment could be optimized by dividing the laser pulse into two pulses with same duration. The degree of alignment could be maximumwith an intensity ratio of 0.3636 at the appropriate delay time of the second pulse relative to the peak of the first pulse.
Field-free alignment of N2 molecule induced by laser pulse with intensity of 1.5×1014 W·cm-2 and duration of 50 fs was investigated by solving time-dependent Schrodinger equation numerically. The results showed that the alignment could be optimized by dividing the laser pulse into two pulses with same duration. The degree of alignment could be maximumwith an intensity ratio of 0.3636 at the appropriate delay time of the second pulse relative to the peak of the first pulse.
2007, 23(05): 757-760
doi: 10.3866/PKU.WHXB20070526
Abstract:
Monolithic carbon sieves with meso-macroporous structure were successfully synthesized with phenol-formaldehyde resin oli mer as precursor by dual-template method. The macropores and mesopores were attained by the removal of SiO2 opal and self-assembling block copolymer respectively. The as-prepared samples were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and nitrogen adsorption-desorption isotherm measurement. The results indicated that the mesopores with diameters of 10 nm and macropores with diameters of 230 nm were formed during the removal of SiO2 opal and block copolymer.
2007, 23(05): 761-764
doi: 10.3866/PKU.WHXB20070527
Abstract:
Photocatalysts La2Ti2-xCoxO7(x=0, 0.05, 0.10, 0.20) with pyrochlore structure were synthesized by sol-gel method. XRD, FT-IR, BET, and UV-Vis diffuse reflectance spectroscopy were used to characterize the crystal structure, specific surface area, and diffuse reflectance spectra, respectively, the formation rate of hydrogen was measured by the photocatalytic activity measurement device and gas chromatography (GC). The results indicated that the absorption pattern of La2Ti2O7 was only generated in the ultraviolet region but La2Ti2O7 with Co doping at B site had strong photoabsorption in the visible light region. The evolution rate of H2 in photolysis of H2O by the La2Ti2-xCoxO7 photocatalysts which doped with Co at B site was highter than that of undoped La2Ti2O7. La2Ti1.9Co0.1O7 showed the best photocatalyst property in all photocatalysts of La2Ti2-xCoxO7 (x=0-0.20).
Photocatalysts La2Ti2-xCoxO7(x=0, 0.05, 0.10, 0.20) with pyrochlore structure were synthesized by sol-gel method. XRD, FT-IR, BET, and UV-Vis diffuse reflectance spectroscopy were used to characterize the crystal structure, specific surface area, and diffuse reflectance spectra, respectively, the formation rate of hydrogen was measured by the photocatalytic activity measurement device and gas chromatography (GC). The results indicated that the absorption pattern of La2Ti2O7 was only generated in the ultraviolet region but La2Ti2O7 with Co doping at B site had strong photoabsorption in the visible light region. The evolution rate of H2 in photolysis of H2O by the La2Ti2-xCoxO7 photocatalysts which doped with Co at B site was highter than that of undoped La2Ti2O7. La2Ti1.9Co0.1O7 showed the best photocatalyst property in all photocatalysts of La2Ti2-xCoxO7 (x=0-0.20).
2007, 23(05): 765-768
doi: 10.3866/PKU.WHXB20070528
Abstract:
TiO2 thin films (anatase and rutile) were prepared on soda-lime glass substrates by sol-gel method. The effects of adsorbed oxygen on the photocatalytic activity of different TiO2 crystals were studied by photocurent measurement and XPS technology. The photocatalytic activity of the different TiO2 crystals (anatase and rutile) was evaluated by the degradation of cyclohexane. The results showed that anatase was more active than rutile, which was attributed to the higher capability of adsorbing oxygen and lower electron-hole recombination rates of the anatase.
TiO2 thin films (anatase and rutile) were prepared on soda-lime glass substrates by sol-gel method. The effects of adsorbed oxygen on the photocatalytic activity of different TiO2 crystals were studied by photocurent measurement and XPS technology. The photocatalytic activity of the different TiO2 crystals (anatase and rutile) was evaluated by the degradation of cyclohexane. The results showed that anatase was more active than rutile, which was attributed to the higher capability of adsorbing oxygen and lower electron-hole recombination rates of the anatase.
2007, 23(05): 769-773
doi: 10.3866/PKU.WHXB20070529
Abstract:
Au nanoparticles coatings were successfully electrodeposited from an electrode/reverse microemulsion system using the reverse microemulsion composed of Triton X-100, n-hexanol, n-hexane and aqueous ld chloride solution with strong acitity. The electrodeposition process of Au was studied by cyclic voltammograms and electrochemical impedance spectroscopy. The results indicated that the reduction of Au(III) was a completely irreversible process, and the impedance of the electrochemical reaction in the microemulsion was 5.5 times as high as that in water solution. The scanning electron microscopy images showed that the coatings electrodeposited from the reverse microemulsions were made up of ld nanoparticles with diameter about 50 nm. Due to the large specific surface area, the electrochemical reaction activity of the Au nanoparticles modified electrode was higher than that of the pure ld electrode, the Au nanoparticles modified electrode had od hydrogen evolution capability in acid solution and od electrocatalytic capability for glycerol oxidation in alkaline media.
Au nanoparticles coatings were successfully electrodeposited from an electrode/reverse microemulsion system using the reverse microemulsion composed of Triton X-100, n-hexanol, n-hexane and aqueous ld chloride solution with strong acitity. The electrodeposition process of Au was studied by cyclic voltammograms and electrochemical impedance spectroscopy. The results indicated that the reduction of Au(III) was a completely irreversible process, and the impedance of the electrochemical reaction in the microemulsion was 5.5 times as high as that in water solution. The scanning electron microscopy images showed that the coatings electrodeposited from the reverse microemulsions were made up of ld nanoparticles with diameter about 50 nm. Due to the large specific surface area, the electrochemical reaction activity of the Au nanoparticles modified electrode was higher than that of the pure ld electrode, the Au nanoparticles modified electrode had od hydrogen evolution capability in acid solution and od electrocatalytic capability for glycerol oxidation in alkaline media.
2007, 23(05): 774-778
doi: 10.3866/PKU.WHXB20070530
Abstract:
To tune the surface wettability of Cu2(OH)2CO3 microspheres, polystyrene nanoparticles were attached to their surfaces via a dispersion polymerization. The products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transmitting infrared spectrum (FT-IR). The immersion times of the modified Cu2(OH)2CO3 microspheres in a water-methanol mixed solution were measured. The results showed that with the increase of the size of the attached polystyrene nanoparticles, the hydrophobicity of the modified Cu2(OH)2CO3 microspheres was enhanced. Using polystyrene nanoparticle-attached Cu2(OH)2CO3 microspheres with intermediate hydrophilicity as emulsifiers, stable water-in-tricaprylin Pickering emulsions were produced. By gelling the water droplets of the Pickering emulsions, the hierarchical structures of polystyrene nanoparticle-modified Cu2(OH)2CO3 microspheres-armored agarose gel microspheres were obtained.
To tune the surface wettability of Cu2(OH)2CO3 microspheres, polystyrene nanoparticles were attached to their surfaces via a dispersion polymerization. The products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transmitting infrared spectrum (FT-IR). The immersion times of the modified Cu2(OH)2CO3 microspheres in a water-methanol mixed solution were measured. The results showed that with the increase of the size of the attached polystyrene nanoparticles, the hydrophobicity of the modified Cu2(OH)2CO3 microspheres was enhanced. Using polystyrene nanoparticle-attached Cu2(OH)2CO3 microspheres with intermediate hydrophilicity as emulsifiers, stable water-in-tricaprylin Pickering emulsions were produced. By gelling the water droplets of the Pickering emulsions, the hierarchical structures of polystyrene nanoparticle-modified Cu2(OH)2CO3 microspheres-armored agarose gel microspheres were obtained.
2007, 23(05): 779-785
doi: 10.3866/PKU.WHXB20070531
Abstract:
Several sets of long-range F-S potential parameters for α-Fe and γ-Fe were deduced according to the method introduced by Sutton et al., and the optima were determined as follows: ε=0.2453, a=0.28664 nm, n=7, m=4, c=7.7525 for α-Fe and ε=0.0006, a=0.36467 nm, n=15, m=4, c=1104.7351 for γ-Fe. Accordingly, the isothermal- isobaric MD simulations were carried out with the set of optimal parameters for α-Fe and γ-Fe at different temperatures in barometric condition. The most-scale agreements between simulations and experiments both for microstructures and macroscopic properties strongly validate the application of this set of parameters to the MD simulation of α-Fe and γ-Fe, and further to the study of interfacial dynamics between metal and oxide.
Several sets of long-range F-S potential parameters for α-Fe and γ-Fe were deduced according to the method introduced by Sutton et al., and the optima were determined as follows: ε=0.2453, a=0.28664 nm, n=7, m=4, c=7.7525 for α-Fe and ε=0.0006, a=0.36467 nm, n=15, m=4, c=1104.7351 for γ-Fe. Accordingly, the isothermal- isobaric MD simulations were carried out with the set of optimal parameters for α-Fe and γ-Fe at different temperatures in barometric condition. The most-scale agreements between simulations and experiments both for microstructures and macroscopic properties strongly validate the application of this set of parameters to the MD simulation of α-Fe and γ-Fe, and further to the study of interfacial dynamics between metal and oxide.
2007, 23(05): 786-789
doi: 10.3866/PKU.WHXB20070532
Abstract:
The values of bond valence parameters R0 for the bonds of main group metal halides are usually obtained by systematic analysis of the crystal structure data by assuming B=0.037 nm. In this work, conversely, the values of B were proposed to be fitted with crystal structure data on assuming the values of R0 equal to the bond lengths of rg accurately determined by gaseous electron diffraction. As an example, the new sets of R0 /B for the Pb(II)—X (X=F, Cl, Br, I) bonds were obtained and fitted as 0.2036/0.0382, 0.2447/0.040, 0.2598/0.040, and 0.2804/0.0386, respectively. Compared with the values of R0=0.203, 0.253, 0.264, and 0.278 nm based on B=0.037nm for Pb(II)—X bonds reported in the literature, these new parameters were not only accurate and reliable for bond valence calculations, but also revealed the physical meaning inherent in every R0 as unit valence bond length.
2007, 23(05): 790-794
doi: 10.3866/PKU.WHXB20070533
Abstract:
The progress of theoretical chemistry of Chinese Mainland in 2006 has been reviewed according to both the methodological developments and their applications.
The progress of theoretical chemistry of Chinese Mainland in 2006 has been reviewed according to both the methodological developments and their applications.
