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2006 Volume 22 Issue 2
2006, 22(02): 131-134
doi: 10.3866/PKU.WHXB20060201
Abstract:
Three pseudo-side-binary systems, LiCl-(2ZnCl2•KCl); LiCl-(ZnCl2•2KCl) and (2ZnCl2•KCl)-(ZnCl2•2KCl) in the pseudo-ternary LiCl-(2ZnCl2•KCl)-(ZnCl2•2KCl), have been investigated by visual-polythermal, DTA and XRD methods. Three new compounds were found in these systems. The ternary compound Li3K2Zn4Cl13 congruently melts at 245 ℃. The incongruent ternary compound Li12K2ZnCl16 and the binary incongruent compound K5Zn4Cl13 peritecticly melt at 432 ℃ and 249 ℃ respectively.
Three pseudo-side-binary systems, LiCl-(2ZnCl2•KCl); LiCl-(ZnCl2•2KCl) and (2ZnCl2•KCl)-(ZnCl2•2KCl) in the pseudo-ternary LiCl-(2ZnCl2•KCl)-(ZnCl2•2KCl), have been investigated by visual-polythermal, DTA and XRD methods. Three new compounds were found in these systems. The ternary compound Li3K2Zn4Cl13 congruently melts at 245 ℃. The incongruent ternary compound Li12K2ZnCl16 and the binary incongruent compound K5Zn4Cl13 peritecticly melt at 432 ℃ and 249 ℃ respectively.
2006, 22(02): 135-140
doi: 10.3866/PKU.WHXB20060202
Abstract:
ld colloids prepared through chemical reduction were self-assembled on the surface of quartz slide to form Au colloidal films. The obtained Au colloidal films were immersed into the mixture of silver enhancer and initiator to fabricate Au core-Ag shell nanoparticles films. The optical characteristics and surface morphology of Au core-Ag shell nanoparticles films prepared under different conditions were characterized by means of UV-Vis spectroscopy and atomic force microscopy. The performance of these Au core-Ag shell nanoparticles films used as SERS-active substrates was evaluated using crystal violet as a molecular probe by the measurement of corresponding surface enhanced Raman spectrum (SERS). It was found that both the distribution of Au colloidal particles on the surface of quartz and the reaction time significantly influence the formation of Au core-Ag shell nanoparticles films. The research results indicate that the Au core-Ag shell nanoparticles film with suitable particles size and od SERS activity can be obtained by controlling the reaction condition.
ld colloids prepared through chemical reduction were self-assembled on the surface of quartz slide to form Au colloidal films. The obtained Au colloidal films were immersed into the mixture of silver enhancer and initiator to fabricate Au core-Ag shell nanoparticles films. The optical characteristics and surface morphology of Au core-Ag shell nanoparticles films prepared under different conditions were characterized by means of UV-Vis spectroscopy and atomic force microscopy. The performance of these Au core-Ag shell nanoparticles films used as SERS-active substrates was evaluated using crystal violet as a molecular probe by the measurement of corresponding surface enhanced Raman spectrum (SERS). It was found that both the distribution of Au colloidal particles on the surface of quartz and the reaction time significantly influence the formation of Au core-Ag shell nanoparticles films. The research results indicate that the Au core-Ag shell nanoparticles film with suitable particles size and od SERS activity can be obtained by controlling the reaction condition.
2006, 22(02): 141-145
doi: 10.3866/PKU.WHXB20060203
Abstract:
The PtRu-NdOx /C catalysts have been prepared by deposition-reduction method. EDX、XRD, and TEM measurements have been used to characterize the composition, particle size, and crystallinity of the catalysts. The catalyst materials consist of Pt-Ru alloy particles and varying amounts of Nd oxide. The average particle size and the lattice parameter of the catalysts are about 2 nm and 0.3896 nm, respectively, which indicates that Nd oxide in PtRu-NdOx /C has no effects on the crystal structure of the Pt-Ru alloy particles. The electrocatalytic activities of the PtRu-NdOx /C catalysts and PtRu/C catalysts have been investigated by cyclic voltammetry and chronoamperometric measurements. Nd oxide can improve the degree of dispersion of the noble metals in the catalysts and as co-catalyst lead to an improvement of the catalytic activity towards methanol oxidation.
The PtRu-NdOx /C catalysts have been prepared by deposition-reduction method. EDX、XRD, and TEM measurements have been used to characterize the composition, particle size, and crystallinity of the catalysts. The catalyst materials consist of Pt-Ru alloy particles and varying amounts of Nd oxide. The average particle size and the lattice parameter of the catalysts are about 2 nm and 0.3896 nm, respectively, which indicates that Nd oxide in PtRu-NdOx /C has no effects on the crystal structure of the Pt-Ru alloy particles. The electrocatalytic activities of the PtRu-NdOx /C catalysts and PtRu/C catalysts have been investigated by cyclic voltammetry and chronoamperometric measurements. Nd oxide can improve the degree of dispersion of the noble metals in the catalysts and as co-catalyst lead to an improvement of the catalytic activity towards methanol oxidation.
2006, 22(02): 146-151
doi: 10.3866/PKU.WHXB20060204
Abstract:
Mg-Al and cation-incorporated(containing Zn2+、Ni2+、Fe3+) hydrotalcites were synthesized and characterized. A detailed comparative analysis of structure and composition was made. Different cations influenced strongly textural parameters of hydrotalcites and the basicity of the obtained Mg-Al oxides after calcinations. With the cation incorporation, the distance of the brucite and the mount of CO32－as the compensating anion changed. Meanwhile the CO2-TPD was used to determine the basicity of the samples. The results showed that the basicity of the calcined hydrotalcites reduced. Finally, the activated hydrotalcite catalysts may efficiently replace homogeneous catalysts in Claisen-Schmidt condensation reaction of the benzaldehyde and propanal. And it was noteworthy that the calcined cation-type(containing Zn2+、Fe3+) hydrotalcites as catalysts did not show significant activity, in agreement with their low basicity.
Mg-Al and cation-incorporated(containing Zn2+、Ni2+、Fe3+) hydrotalcites were synthesized and characterized. A detailed comparative analysis of structure and composition was made. Different cations influenced strongly textural parameters of hydrotalcites and the basicity of the obtained Mg-Al oxides after calcinations. With the cation incorporation, the distance of the brucite and the mount of CO32－as the compensating anion changed. Meanwhile the CO2-TPD was used to determine the basicity of the samples. The results showed that the basicity of the calcined hydrotalcites reduced. Finally, the activated hydrotalcite catalysts may efficiently replace homogeneous catalysts in Claisen-Schmidt condensation reaction of the benzaldehyde and propanal. And it was noteworthy that the calcined cation-type(containing Zn2+、Fe3+) hydrotalcites as catalysts did not show significant activity, in agreement with their low basicity.
2006, 22(02): 152-155
doi: 10.3866/PKU.WHXB20060205
Abstract:
Two new structures of cage (terminal cage) and ring for silica clusters (SiO2)nO2H4 (n＝2～22, n is even) are presented and compared with line structure. Geometric structures, average binding energies, energy gaps and second order difference of energy are systematically studied by density function theory (DFT) B3LYP with basis set 6-31G(d). The results indicate that for cage structures of (SiO2)nO2H4 (n＝2～22, n is even) magic number clusters exist not only at n=4, 8, but also at n=14. Ring structures of (SiO2)nO2H4 clusters are different from that of (SiO2)n. For the latter they are more stable than line structures from n=11. However, for the former it is from n=4 ring structures begin to be more stable than line structures. It means that the addition of water has an important effect on the stabilities of silica clusters.
Two new structures of cage (terminal cage) and ring for silica clusters (SiO2)nO2H4 (n＝2～22, n is even) are presented and compared with line structure. Geometric structures, average binding energies, energy gaps and second order difference of energy are systematically studied by density function theory (DFT) B3LYP with basis set 6-31G(d). The results indicate that for cage structures of (SiO2)nO2H4 (n＝2～22, n is even) magic number clusters exist not only at n=4, 8, but also at n=14. Ring structures of (SiO2)nO2H4 clusters are different from that of (SiO2)n. For the latter they are more stable than line structures from n=11. However, for the former it is from n=4 ring structures begin to be more stable than line structures. It means that the addition of water has an important effect on the stabilities of silica clusters.
2006, 22(02): 156-160
doi: 10.3866/PKU.WHXB20060206
Abstract:
Density Function Theory (DFT) B3LYP method was employed to study the mechanism of the reaction of CF3O2 radical and NO with the 6-31G、6-311G、6-311+G(d) basis sets. The study results indicate that there are three reaction pathways in this reaction. The main reaction pathway is CF3O2+NO→IM1→TS1→IM2→TS2→CF3O+NO2, the corresponding activation energy is 70.86 kJ•mol-1. The other reaction pathways are CF3O2+NO→ IM1→TS3→ CF3ONO2 and CF3O2+NO→TS4→IM3→TS5→IM4→TS6→CF3O+NOO, the corresponding activation energies are 258.71 kJ•mol-1 and 278.60 kJ•mol-1, and these reaction pathways are difficult to carry out. The results show that the main products are CF3O and NO2, which is in agreement with the results in literatures.
Density Function Theory (DFT) B3LYP method was employed to study the mechanism of the reaction of CF3O2 radical and NO with the 6-31G、6-311G、6-311+G(d) basis sets. The study results indicate that there are three reaction pathways in this reaction. The main reaction pathway is CF3O2+NO→IM1→TS1→IM2→TS2→CF3O+NO2, the corresponding activation energy is 70.86 kJ•mol-1. The other reaction pathways are CF3O2+NO→ IM1→TS3→ CF3ONO2 and CF3O2+NO→TS4→IM3→TS5→IM4→TS6→CF3O+NOO, the corresponding activation energies are 258.71 kJ•mol-1 and 278.60 kJ•mol-1, and these reaction pathways are difficult to carry out. The results show that the main products are CF3O and NO2, which is in agreement with the results in literatures.
2006, 22(02): 161-166
doi: 10.3866/PKU.WHXB20060207
Abstract:
The conductance of an Al-C60-Al molecule junction is calculated using a density functional theory combined with Green′s function method. When the molecule is connected to the electrodes and allowed to relax, resonant conductance is the main feature of the transport properties of the Al-C60-Al molecule junction. The conductance around the Fermi level is determined to be about 1.14G0 (G0=2e2/h). Analysis of the density of states projected onto the frontier molecular orbitals of the C60 molecule shows that electron transport occurs primarily through the lowest unoccupied molecular orbital (LUMO) and the second lowest unoccupied molecular orbital (LUMO+1) of C60. The dependence of the junction conductance on the distance between the C60 molecule and the electrodes is also discussed.
The conductance of an Al-C60-Al molecule junction is calculated using a density functional theory combined with Green′s function method. When the molecule is connected to the electrodes and allowed to relax, resonant conductance is the main feature of the transport properties of the Al-C60-Al molecule junction. The conductance around the Fermi level is determined to be about 1.14G0 (G0=2e2/h). Analysis of the density of states projected onto the frontier molecular orbitals of the C60 molecule shows that electron transport occurs primarily through the lowest unoccupied molecular orbital (LUMO) and the second lowest unoccupied molecular orbital (LUMO+1) of C60. The dependence of the junction conductance on the distance between the C60 molecule and the electrodes is also discussed.
2006, 22(02): 167-171
doi: 10.3866/PKU.WHXB20060208
Abstract:
The simulation for electronic paramagnetic resonance (EPR) spectrum with hyperfine couplings as well as multiple coordination components is often difficult. Here we develop a simulation approach based on the second-order perturbation theory to address these issues. The EPR spectral simulations of the silk fibroin-Cu(II) complexes are taken as examples to illustrate this approach, efficiently revealing the function of Cu(II) in the spinning process of silkworm. In addition, this approach would be useful for the EPR simulations of complexes containing Fe(II), Mn(II), V(III) and other paramagnetic ions.
The simulation for electronic paramagnetic resonance (EPR) spectrum with hyperfine couplings as well as multiple coordination components is often difficult. Here we develop a simulation approach based on the second-order perturbation theory to address these issues. The EPR spectral simulations of the silk fibroin-Cu(II) complexes are taken as examples to illustrate this approach, efficiently revealing the function of Cu(II) in the spinning process of silkworm. In addition, this approach would be useful for the EPR simulations of complexes containing Fe(II), Mn(II), V(III) and other paramagnetic ions.
2006, 22(02): 172-177
doi: 10.3866/PKU.WHXB20060209
Abstract:
The initial nucleation and phase transformatin process of the Fe(OH)3 gel in five different mineralization systems with different dextran concentrations(from 0～2.0%(w) and the same [Fe3＋]=0.012 mol•L-1) have been investigated. The mineralizational phases in the initial stage were characterized by FTIR, XRD and ICP-AES spectrometry. The results showed that the concentration of Fe3＋ ions in supernatant increased suddenly in the third day during aging and then its secondary reduction stage occurred. There were the same chages of pH as [Fe3＋] in these process. The initial phases formed in the systems with dextran were mainly β-FeOOH, not α-FeOOH which growing rapidly in the system without dextran. The dextran molecules were adsorbed on the surfaces of iron oxide particles by complexing with Fe3＋. The adsorbed dextran molecules would facilitate the phase transformation from β-FeOOH into α-Fe2O3 by a dissolution-recrystallization mechanism. The secondary reduction stage of [Fe3＋] corresponded to the process of the phase transformation from β-FeOOH into α-Fe2O3. With the increasement of the concentrations of dextran (up to 2.0%(w)) in solution, the dissolution of β-FeOOH and the formation of α-Fe2O3 in these mineralization systems were accelerated. It was clear that dextran molecules could control the nuclei type and its phase transformation of the Fe(OH)3 gel.
The initial nucleation and phase transformatin process of the Fe(OH)3 gel in five different mineralization systems with different dextran concentrations(from 0～2.0%(w) and the same [Fe3＋]=0.012 mol•L-1) have been investigated. The mineralizational phases in the initial stage were characterized by FTIR, XRD and ICP-AES spectrometry. The results showed that the concentration of Fe3＋ ions in supernatant increased suddenly in the third day during aging and then its secondary reduction stage occurred. There were the same chages of pH as [Fe3＋] in these process. The initial phases formed in the systems with dextran were mainly β-FeOOH, not α-FeOOH which growing rapidly in the system without dextran. The dextran molecules were adsorbed on the surfaces of iron oxide particles by complexing with Fe3＋. The adsorbed dextran molecules would facilitate the phase transformation from β-FeOOH into α-Fe2O3 by a dissolution-recrystallization mechanism. The secondary reduction stage of [Fe3＋] corresponded to the process of the phase transformation from β-FeOOH into α-Fe2O3. With the increasement of the concentrations of dextran (up to 2.0%(w)) in solution, the dissolution of β-FeOOH and the formation of α-Fe2O3 in these mineralization systems were accelerated. It was clear that dextran molecules could control the nuclei type and its phase transformation of the Fe(OH)3 gel.
2006, 22(02): 178-182
doi: 10.3866/PKU.WHXB20060210
Abstract:
The geometric configurations, electronic structures, vibrational frequencies, and atomic charge of the AlmN2－ (m=1～8) clusters were studied using the B3LYP (DFT) method at 6-311G* level. The results show that there exist two types of bonding character in the ground state of AlmN2－ clusters. One is formed through N—N bonds and aluminum atom, the other is combined with AlnN(n
The geometric configurations, electronic structures, vibrational frequencies, and atomic charge of the AlmN2－ (m=1～8) clusters were studied using the B3LYP (DFT) method at 6-311G* level. The results show that there exist two types of bonding character in the ground state of AlmN2－ clusters. One is formed through N—N bonds and aluminum atom, the other is combined with AlnN(n
2006, 22(02): 183-188
doi: 10.3866/PKU.WHXB20060211
Abstract:
The effect of Ti-doping on different morphologic LiCoO2 was characterized by scanning electron microscope(SEM) along with energy dispersive spectroscopy(EDS), X-ray diffraction(XRD), electrochemical impedance spectroscopy(EIS), and galvanostatic charge-discharge tests. The result indicated that Ti-doping did not affect the structure of different morphologic LiCoO2 but considerably improved its electrochemical performance, especially the behavior of large current discharge (1 C). In the case of being discharged at a 1 C discharge rate, 3.8 V voltage plateau(the ratio of capacity above 3.8 V to total capacity) of secondary particles doped with TiO2 could retain 60% after 20 cycles, which was better than primary particles doped with TiO2 (40%). EIS result showed that Ti-doping could evidently suppress the increase of the electrochemical reaction resistant at large current discharge rate for secondary particles.
The effect of Ti-doping on different morphologic LiCoO2 was characterized by scanning electron microscope(SEM) along with energy dispersive spectroscopy(EDS), X-ray diffraction(XRD), electrochemical impedance spectroscopy(EIS), and galvanostatic charge-discharge tests. The result indicated that Ti-doping did not affect the structure of different morphologic LiCoO2 but considerably improved its electrochemical performance, especially the behavior of large current discharge (1 C). In the case of being discharged at a 1 C discharge rate, 3.8 V voltage plateau(the ratio of capacity above 3.8 V to total capacity) of secondary particles doped with TiO2 could retain 60% after 20 cycles, which was better than primary particles doped with TiO2 (40%). EIS result showed that Ti-doping could evidently suppress the increase of the electrochemical reaction resistant at large current discharge rate for secondary particles.
2006, 22(02): 189-192
doi: 10.3866/PKU.WHXB20060212
Abstract:
A novel strategy of preparing of hollow barium ferrite submicrospheres based on chemical self-assembly technique is described in this paper. That is, using poly (styrene-co-acrylic acid) latexes as template, the chemical interaction between the carboxyl groups on the latex surface and the hydroxyl groups on the surface of barium ferrite precursor prepared in poly-glycol solution results in the formation of poly(styrene-co-acrylic acid)/ barium ferrite precursors core-shell nanocomposite particles. Heat-treatment of the composite particles by upgrading temperature to 750 ℃ leads to hollow barium ferrite submicrospheres with BaFe12O19 crystal phase mainly. The products might find significant applications in such fields as radar absorbers or electro-magneto-rheological fluids.
A novel strategy of preparing of hollow barium ferrite submicrospheres based on chemical self-assembly technique is described in this paper. That is, using poly (styrene-co-acrylic acid) latexes as template, the chemical interaction between the carboxyl groups on the latex surface and the hydroxyl groups on the surface of barium ferrite precursor prepared in poly-glycol solution results in the formation of poly(styrene-co-acrylic acid)/ barium ferrite precursors core-shell nanocomposite particles. Heat-treatment of the composite particles by upgrading temperature to 750 ℃ leads to hollow barium ferrite submicrospheres with BaFe12O19 crystal phase mainly. The products might find significant applications in such fields as radar absorbers or electro-magneto-rheological fluids.
2006, 22(02): 193-197
doi: 10.3866/PKU.WHXB20060213
Abstract:
Layered zinc benzoate hydroxide compound with a basal spacing of 1.44 nm was prepared by hydrothermal reaction in a temperature range of 110～180 ℃. XRD, TG-DTA, SEM, TEM, and elementary analysis were used to characterize the structure, particle morphology, characteristic, and chemical composition of the synthesized layered compounds. Meanwhile, the effect of the synthetic conditions on the obtained compound was also investigated. The results indicated that when the molar ratio of C6H5COOH/Zn was 0.9～1.0, the temperature 130～150 ℃ and the reaction time 12 h, the prepared compound was of fibrous particle morphology, and its chemical formula can be written as Zn(OH)1.12•(C6H5COO)0.88.
Layered zinc benzoate hydroxide compound with a basal spacing of 1.44 nm was prepared by hydrothermal reaction in a temperature range of 110～180 ℃. XRD, TG-DTA, SEM, TEM, and elementary analysis were used to characterize the structure, particle morphology, characteristic, and chemical composition of the synthesized layered compounds. Meanwhile, the effect of the synthetic conditions on the obtained compound was also investigated. The results indicated that when the molar ratio of C6H5COOH/Zn was 0.9～1.0, the temperature 130～150 ℃ and the reaction time 12 h, the prepared compound was of fibrous particle morphology, and its chemical formula can be written as Zn(OH)1.12•(C6H5COO)0.88.
2006, 22(02): 198-202
doi: 10.3866/PKU.WHXB20060214
Abstract:
A series of high silica mordenite samples synthesized from amine-free system using fluoride as structure-directing agent were characterized by XRD, SEM, FT-IR, and MAS NMR. The results confirmed that the samples were truly mordenite with high SiO2/Al2O3 molar ratio. The unit cell constants a, b, c and the unit cell volume (a×b×c) of M-36 sample were smaller than those of mordenite with silica alumina molar ratio(SAR)=10 reported in the literature, which indicated the unit cell contraction caused by the replacement of Al atoms by smaller Si atoms. However, compared with the sample with SAR=31.5 synthesized from free-fluoride system, the lattice parameters of M-36 were somewhat increased in the a and c directions, but elongated obviously in b direction, which indicated some influences on 8-membered ring parallel to the b axis of mordenite structure should be brought by using fluoride as structure-directing agent. As the SAR of mordenite samples increased, a variety of crystal morphologies (cuboids, hexa nal prismatic crystals, rectangular parallelepiped crystals) was observed and a wide variation in the crystallite size was presented. As the SAR changed from 14 to 55, in the infrared spectra of the samples, the band attributed to T—O bending vibration shifted from 434 cm-1 to 450 cm-1, and its absorption intensity also increased. The band at 720 cm-1 which corresponded to the internal symmetric stretching vibration of the AlO4 tetrahedral in the mordenite from a weak band developed into a broad band and nearly disappeared at last, indicating that the number of SiO4 in the framework was increased. In 27Al MAS NMR spectra, almost all high silica mordenite samples presented a peak at δ(55.6) and no non-framework Al species peak at about δ(0), which was different from steamed or acid-leached siliceous mordenite.
A series of high silica mordenite samples synthesized from amine-free system using fluoride as structure-directing agent were characterized by XRD, SEM, FT-IR, and MAS NMR. The results confirmed that the samples were truly mordenite with high SiO2/Al2O3 molar ratio. The unit cell constants a, b, c and the unit cell volume (a×b×c) of M-36 sample were smaller than those of mordenite with silica alumina molar ratio(SAR)=10 reported in the literature, which indicated the unit cell contraction caused by the replacement of Al atoms by smaller Si atoms. However, compared with the sample with SAR=31.5 synthesized from free-fluoride system, the lattice parameters of M-36 were somewhat increased in the a and c directions, but elongated obviously in b direction, which indicated some influences on 8-membered ring parallel to the b axis of mordenite structure should be brought by using fluoride as structure-directing agent. As the SAR of mordenite samples increased, a variety of crystal morphologies (cuboids, hexa nal prismatic crystals, rectangular parallelepiped crystals) was observed and a wide variation in the crystallite size was presented. As the SAR changed from 14 to 55, in the infrared spectra of the samples, the band attributed to T—O bending vibration shifted from 434 cm-1 to 450 cm-1, and its absorption intensity also increased. The band at 720 cm-1 which corresponded to the internal symmetric stretching vibration of the AlO4 tetrahedral in the mordenite from a weak band developed into a broad band and nearly disappeared at last, indicating that the number of SiO4 in the framework was increased. In 27Al MAS NMR spectra, almost all high silica mordenite samples presented a peak at δ(55.6) and no non-framework Al species peak at about δ(0), which was different from steamed or acid-leached siliceous mordenite.
2006, 22(02): 203-208
doi: 10.3866/PKU.WHXB20060215
Abstract:
The hollow and Fe nanoparticle-encapsulated nano onion-like fullerenes (NOLFs) were synthesized respectively by DC arc-discharge in water and chemical vapor deposition (CVD). The microstructures of two products were characterized and analyzed by XRD, FESEM, and HRTEM. 2～18 GHz complex permittivity and complex permeability of different carbon materials, including NOLFs, graphite, and active carbon, were measured using HP8722ES vector network analyzer for comparison. The results showed that complex permittivity and dielectric loss of two NOLFs are higher; Fe nanoparticles-encapsulated NOLFs have magnetic loss.
The hollow and Fe nanoparticle-encapsulated nano onion-like fullerenes (NOLFs) were synthesized respectively by DC arc-discharge in water and chemical vapor deposition (CVD). The microstructures of two products were characterized and analyzed by XRD, FESEM, and HRTEM. 2～18 GHz complex permittivity and complex permeability of different carbon materials, including NOLFs, graphite, and active carbon, were measured using HP8722ES vector network analyzer for comparison. The results showed that complex permittivity and dielectric loss of two NOLFs are higher; Fe nanoparticles-encapsulated NOLFs have magnetic loss.
2006, 22(02): 209-214
doi: 10.3866/PKU.WHXB20060216
Abstract:
N-aminoimidazoles (NAIMs) can inhibit the replication of HIV-1 in three different modes. From a set of NAIM molecules with similar backbone, a 3D-QSAR model has been made by means of the comparative molecular field analysis (CoMFA) approach. Unlike common 3D-QSAR approaching, in PLS (partial least-squares) analysis we try to import the energy information of molecular orbitals into the model, in order to investigate the relationship between bio-activity and molecular orbital energies. The results show that several models were achieved, and the contribution of the energies of molecular orbitals reached to 21.7% in the combination model, especially the energy of the HOMO5 has the most contribution.
N-aminoimidazoles (NAIMs) can inhibit the replication of HIV-1 in three different modes. From a set of NAIM molecules with similar backbone, a 3D-QSAR model has been made by means of the comparative molecular field analysis (CoMFA) approach. Unlike common 3D-QSAR approaching, in PLS (partial least-squares) analysis we try to import the energy information of molecular orbitals into the model, in order to investigate the relationship between bio-activity and molecular orbital energies. The results show that several models were achieved, and the contribution of the energies of molecular orbitals reached to 21.7% in the combination model, especially the energy of the HOMO5 has the most contribution.
2006, 22(02): 215-220
doi: 10.3866/PKU.WHXB20060217
Abstract:
The dilution enthalpies of D-mannitol and D-sorbitol in aqueous sodium chloride solution have been determined by using flow-mix-isothermal microcalorimetry at 298.15 K. The enthalpic pairwise interaction coefficients(h2) in the range of sodium chloride concentration (0～1.2 mol•kg-1) have been calculated according to the McMillan-Mayer theory. It is found that h2 of coefficients D-mannitol and D-sorbitol are all positive in aqueous sodium chloride solution and become more positive with increase of the concentration of sodium chloride. Further analysis indicates that the increasing rate of the h2 coefficient [dh2/dm(NaCl)] for D-sorbitol is larger than that of D-mannitol. The results are discussed in terms of the different conformations of the two polylols, interactions of solute with solute and solute with solvent.
The dilution enthalpies of D-mannitol and D-sorbitol in aqueous sodium chloride solution have been determined by using flow-mix-isothermal microcalorimetry at 298.15 K. The enthalpic pairwise interaction coefficients(h2) in the range of sodium chloride concentration (0～1.2 mol•kg-1) have been calculated according to the McMillan-Mayer theory. It is found that h2 of coefficients D-mannitol and D-sorbitol are all positive in aqueous sodium chloride solution and become more positive with increase of the concentration of sodium chloride. Further analysis indicates that the increasing rate of the h2 coefficient [dh2/dm(NaCl)] for D-sorbitol is larger than that of D-mannitol. The results are discussed in terms of the different conformations of the two polylols, interactions of solute with solute and solute with solvent.
2006, 22(02): 221-225
doi: 10.3866/PKU.WHXB20060218
Abstract:
Titanate nanotubes were prepared by hydrothermal method, and the products were characterized with TEM, XRD, and XPS. The diameter of the nanotube was around 5 nm to 30 nm with a length ranging from approximately 0.1 μm to 1 μm. The structure of the nanotube was that of titanate different from anatase phase； the composition of the products may be Na4－xHxTi2O5. The photoelectrochemical properties of the titanate nanotubes were investigated. Titanate nanotubes produced anodic photocurrent, exhibiting the property of the n-type semiconductor.
Titanate nanotubes were prepared by hydrothermal method, and the products were characterized with TEM, XRD, and XPS. The diameter of the nanotube was around 5 nm to 30 nm with a length ranging from approximately 0.1 μm to 1 μm. The structure of the nanotube was that of titanate different from anatase phase； the composition of the products may be Na4－xHxTi2O5. The photoelectrochemical properties of the titanate nanotubes were investigated. Titanate nanotubes produced anodic photocurrent, exhibiting the property of the n-type semiconductor.
2006, 22(02): 226-229
doi: 10.3866/PKU.WHXB20060219
Abstract:
The liposomes of cefazolin sodium were prepared using one step supercritical CO2 (scCO2) method. The size, stability, and trapping efficiency of liposomes were investigated. The experimental results demonstrate that the size and stability of liposomes depend on the pressure. The trapping efficiency of liposomes relates to the concentration of ethanol and lipid. The trapping efficiency by the scCO2 method is much higher than the results from the Bangham method.
The liposomes of cefazolin sodium were prepared using one step supercritical CO2 (scCO2) method. The size, stability, and trapping efficiency of liposomes were investigated. The experimental results demonstrate that the size and stability of liposomes depend on the pressure. The trapping efficiency of liposomes relates to the concentration of ethanol and lipid. The trapping efficiency by the scCO2 method is much higher than the results from the Bangham method.
2006, 22(02): 230-233
doi: 10.3866/PKU.WHXB20060220
Abstract:
The acid-dissociation constant pKa of different polycarboxyl imidazolium ionic liquids (ILs) has been determined by potentiometric titration method at 25 ℃, and the values are in the range of 1.43 to 1.92, which are close to that of oxalic acid, but much smaller than those of succinic acid and acetic acid. The stronger acidity of polycarboxyl imidazolium ILs results from the strong electron withdrawing effect of positively charged imidazolium ring. It is also demonstrated that the acidity of the ILs is enhanced as the number of carboxylic groups appended to cations increases from two to three. The acidity of the ILs also depends on properties of the anions, and decreases in the order HSO4－ ＞ NO3－ ＞ PF6－ ＞ H2PO4－＞ Cl－、Br－ ＞ CF3CO2－ ＞ BF4－ ＞ CF3SO3－. The Brønsted acidity of the polycarboxyl imidazolium ILs has also been studied by IR technique using pyridine as the spectroscopic probe.
The acid-dissociation constant pKa of different polycarboxyl imidazolium ionic liquids (ILs) has been determined by potentiometric titration method at 25 ℃, and the values are in the range of 1.43 to 1.92, which are close to that of oxalic acid, but much smaller than those of succinic acid and acetic acid. The stronger acidity of polycarboxyl imidazolium ILs results from the strong electron withdrawing effect of positively charged imidazolium ring. It is also demonstrated that the acidity of the ILs is enhanced as the number of carboxylic groups appended to cations increases from two to three. The acidity of the ILs also depends on properties of the anions, and decreases in the order HSO4－ ＞ NO3－ ＞ PF6－ ＞ H2PO4－＞ Cl－、Br－ ＞ CF3CO2－ ＞ BF4－ ＞ CF3SO3－. The Brønsted acidity of the polycarboxyl imidazolium ILs has also been studied by IR technique using pyridine as the spectroscopic probe.
2006, 22(02): 234-238
doi: 10.3866/PKU.WHXB20060221
Abstract:
The first delithiation of the spinel LiMn2O4 electrode was studied using electrochemical impedance spectroscopy (EIS). Appropriate equivalent circuits were proposed to fit the experimental EIS data. Based on the fitting results, the variation of the capacitance and the resistance of SEI (solid electrolyte interphase) film, the resistance of charge transfer, and the capacitance of double layer along with the increase of polarization potential were quantitatively analyzed. The results demonstrated that the resistance and the thickness of the SEI film formed on the spinel LiMn2O4 electrode were both increased with the increase of polarization potential in the first delithiation of the spinel LiMn2O4 electrode; The charge transfer resistance decreases below 4.15 V and increases above 4.15 V, corresponding to the two-step reversible (de)intercalation of lithium between LiMn2O4 and λ-MnO2; The double layer capacitance was influenced by both the state of the spinel LiMn2O4 electrode(different polarization potential) and the two-step reversible (de)intercalation of lithium.
The first delithiation of the spinel LiMn2O4 electrode was studied using electrochemical impedance spectroscopy (EIS). Appropriate equivalent circuits were proposed to fit the experimental EIS data. Based on the fitting results, the variation of the capacitance and the resistance of SEI (solid electrolyte interphase) film, the resistance of charge transfer, and the capacitance of double layer along with the increase of polarization potential were quantitatively analyzed. The results demonstrated that the resistance and the thickness of the SEI film formed on the spinel LiMn2O4 electrode were both increased with the increase of polarization potential in the first delithiation of the spinel LiMn2O4 electrode; The charge transfer resistance decreases below 4.15 V and increases above 4.15 V, corresponding to the two-step reversible (de)intercalation of lithium between LiMn2O4 and λ-MnO2; The double layer capacitance was influenced by both the state of the spinel LiMn2O4 electrode(different polarization potential) and the two-step reversible (de)intercalation of lithium.
2006, 22(02): 239-243
doi: 10.3866/PKU.WHXB20060222
Abstract:
After surface metallized modification, fly ash cenospheres which have the properties of light, hollow, low density, fine granularity, high intensity, heat-resistant and od conductivity are widely used as the fillings in composite materials and may probably become a new type of microwave absorber to replace the ultrafine metallic and ferrite powders. In this paper, conductive and magnetic cenospheres were fabricated by electroless plating Ni-Co-P alloy films on the surface of fly ash cenospheres after the pretreatment of sensitization and activation by SnCl2 and PdCl2. XRD, EDS, SEM and metallic microgragh analytical methods were utilized to characterize the properties and microstructure of the cenospheres coated with Ni-Co-P films by electroless plating. The results indicate that uniform and high quality Ni-Co-P alloy film with 2～4 μm thickness could be obtained after the activation by PdCl2.
After surface metallized modification, fly ash cenospheres which have the properties of light, hollow, low density, fine granularity, high intensity, heat-resistant and od conductivity are widely used as the fillings in composite materials and may probably become a new type of microwave absorber to replace the ultrafine metallic and ferrite powders. In this paper, conductive and magnetic cenospheres were fabricated by electroless plating Ni-Co-P alloy films on the surface of fly ash cenospheres after the pretreatment of sensitization and activation by SnCl2 and PdCl2. XRD, EDS, SEM and metallic microgragh analytical methods were utilized to characterize the properties and microstructure of the cenospheres coated with Ni-Co-P films by electroless plating. The results indicate that uniform and high quality Ni-Co-P alloy film with 2～4 μm thickness could be obtained after the activation by PdCl2.
2006, 22(02): 244-248
doi: 10.3866/PKU.WHXB20060223
Abstract:
The complex stability constants for the 1∶1 inclusion complexation of various dihydroxybenzenes (pyrocatechol, hydroquinone, resorcinol) with cellulose fibre grafted β-cyclodextrin have been determined by means of spectrophotometric titrations at different temperatures in aqueous solutions with different pH values. The molecular recognition mechanism for various complexes of dihydroxybenzenes and β-cyclodextrin is discussed from the viewpoint of stability constants, apparent thermodynamic parameters, the size/shape-fit, multiple recognition, and pH value of inclusion systems of dihydroxybenzenes between the host cavity and the guest molecules. The results show that the cellulose fibre grafted β-cyclodextrin possesses a special binding ability and molecular selectivity for dihydroxybenzenes, the complex stability constants of dihydroxybenzenes are Ka(resorcinol)>Ka(hydroquinone)>Ka(pyrocatechol), apparent thermodynamic parameters of dihydroxybenzenes are ΔH(resorcinol )<ΔH(hydroquinone)<ΔH(pyrocatechol) and ΔS(resorcinol)<ΔS(hydroquinone)< ΔS(pyrocatechol).
The complex stability constants for the 1∶1 inclusion complexation of various dihydroxybenzenes (pyrocatechol, hydroquinone, resorcinol) with cellulose fibre grafted β-cyclodextrin have been determined by means of spectrophotometric titrations at different temperatures in aqueous solutions with different pH values. The molecular recognition mechanism for various complexes of dihydroxybenzenes and β-cyclodextrin is discussed from the viewpoint of stability constants, apparent thermodynamic parameters, the size/shape-fit, multiple recognition, and pH value of inclusion systems of dihydroxybenzenes between the host cavity and the guest molecules. The results show that the cellulose fibre grafted β-cyclodextrin possesses a special binding ability and molecular selectivity for dihydroxybenzenes, the complex stability constants of dihydroxybenzenes are Ka(resorcinol)>Ka(hydroquinone)>Ka(pyrocatechol), apparent thermodynamic parameters of dihydroxybenzenes are ΔH(resorcinol )<ΔH(hydroquinone)<ΔH(pyrocatechol) and ΔS(resorcinol)<ΔS(hydroquinone)< ΔS(pyrocatechol).
2006, 22(02): 249-253
doi: 10.3866/PKU.WHXB20060224
Abstract:
The adsorptive behavior of three cationic Gemini surfactants (C16H33(CH3)2N-C4H8-N(CH3)2C16H33 (C16-C4-C16), C12H25(CH3)2N-C4H8-N(CH3)2C12H25 (C12-C4-C12), C8H17(CH3)2N-C4H8-N(CH3)2C8H17 (C8-C4-C8)) at bare ld electrode has been studied with cyclic voltammetry, alternating current impedance spectra(ACIS), and quartz crystal microbalance (QCM). It is found that the electrochemical probe catechol (CC) can exhibit two pairs of redox peaks in the range of 0～0.8 V (vs SCE) in 0.3 mol•L-1 KNO3 solutions. When some cationic Gemini surfactants are introduced into the solutions, the first pair of peaks decreases, but the second pair of peaks increases. At the same time, the anodic peaks move in positive direction and the cathodic peaks shift in negative direction. For the three Gemini surfactants, their influence on the voltammetric behavior of CC follows such order as C8-C4-C8 ＜ C12-C4-C12 ＜ C16-C4-C16. ACIS shows that in the presence of Gemini surfactants, the impedance of the electrode interface grows. For those surfactants, the impedance rises with increasing alkyl-chain length. Similar result is obtained in QCM experiment. Namely, when the alkyl-chain is longer, the Gemini surfactant makes the frequency change more. The adsorption modes of those Gemini surfactants are estimated according to the change of the first anodic peak area of CC. It is found that their adsorption belongs to Langmuir adsorption.
The adsorptive behavior of three cationic Gemini surfactants (C16H33(CH3)2N-C4H8-N(CH3)2C16H33 (C16-C4-C16), C12H25(CH3)2N-C4H8-N(CH3)2C12H25 (C12-C4-C12), C8H17(CH3)2N-C4H8-N(CH3)2C8H17 (C8-C4-C8)) at bare ld electrode has been studied with cyclic voltammetry, alternating current impedance spectra(ACIS), and quartz crystal microbalance (QCM). It is found that the electrochemical probe catechol (CC) can exhibit two pairs of redox peaks in the range of 0～0.8 V (vs SCE) in 0.3 mol•L-1 KNO3 solutions. When some cationic Gemini surfactants are introduced into the solutions, the first pair of peaks decreases, but the second pair of peaks increases. At the same time, the anodic peaks move in positive direction and the cathodic peaks shift in negative direction. For the three Gemini surfactants, their influence on the voltammetric behavior of CC follows such order as C8-C4-C8 ＜ C12-C4-C12 ＜ C16-C4-C16. ACIS shows that in the presence of Gemini surfactants, the impedance of the electrode interface grows. For those surfactants, the impedance rises with increasing alkyl-chain length. Similar result is obtained in QCM experiment. Namely, when the alkyl-chain is longer, the Gemini surfactant makes the frequency change more. The adsorption modes of those Gemini surfactants are estimated according to the change of the first anodic peak area of CC. It is found that their adsorption belongs to Langmuir adsorption.
2006, 22(02): 254-260
doi: 10.3866/PKU.WHXB20060225
Abstract:
Our results and the applications of spectroscopic methods in studying protein-surfactant system are systematically summarized. Those methods include UV absorption spectroscopy, fluorescence spectroscopy, circular dichroism and electron spin resonance. Many studies indicate that spectroscopic methods can be used to not only study the relationship between structure and function of protein but also probe the interaction mechanism of protein and surfactant.
Our results and the applications of spectroscopic methods in studying protein-surfactant system are systematically summarized. Those methods include UV absorption spectroscopy, fluorescence spectroscopy, circular dichroism and electron spin resonance. Many studies indicate that spectroscopic methods can be used to not only study the relationship between structure and function of protein but also probe the interaction mechanism of protein and surfactant.
