Login In
2005 Volume 21 Issue 2
2005, 21(02): 113-116
doi: 10.3866/PKU.WHXB20050201
Abstract:
Monodisperse surfactant-capped CdSe nanocrystals were prepared by the pyrolysis of ligands of Se and Cd in a hot coordinating solvent. The CdSe nanocrystals synthesized at different reaction times have been characterized by UV-Vis and fluorescence (FL) spectra. Results of UV-Vis and FL spectra showed that the CdSe nanocrystals prepared at the reaction time of 15 min exhibited the largest fluorescence intensity.
Monodisperse surfactant-capped CdSe nanocrystals were prepared by the pyrolysis of ligands of Se and Cd in a hot coordinating solvent. The CdSe nanocrystals synthesized at different reaction times have been characterized by UV-Vis and fluorescence (FL) spectra. Results of UV-Vis and FL spectra showed that the CdSe nanocrystals prepared at the reaction time of 15 min exhibited the largest fluorescence intensity.
2005, 21(02): 117-122
doi: 10.3866/PKU.WHXB20050202
Abstract:
A new sol-gel process for the preparation of ultrafine nickel hydroxide electrode materials was developed. The particle size and configuration of the nickel hydroxide product can be controlled with polyethylene glycol. The hydroxide particles have a diameter range of 100～200 nm and take on an unique chain-bead like configuration. The composite electrodes consisting of carbon nanotubes and Ni(OH)2 were developed by mixing the hydroxide and carbon nanotubes together in varous ratios. A maximum capacitance of 320 F•g－1 was obtained for the composite electrode containing 20％ carbon nanotubes compared with that of activated carbon(184 F•g－1). The performance of a newly designed combined electrochemical capacitor was evaluated. The capacitor was prepared by using nickel hydroxide/carbon nanotubes composite as a positive electrode and activated carbon as a negative electrode. Values for the specific energy and maximum specific power of 20.11 W•h•kg－1 and 8.6 W•g－1,respectively,were demonstrated for a cell voltage between 0 and 1.6 V. By using the modified anode of a Ni(OH)2/carbon nanotubes composite electrode, the combined supercapacitor exhibited high energy density and stable power characteristics.
A new sol-gel process for the preparation of ultrafine nickel hydroxide electrode materials was developed. The particle size and configuration of the nickel hydroxide product can be controlled with polyethylene glycol. The hydroxide particles have a diameter range of 100～200 nm and take on an unique chain-bead like configuration. The composite electrodes consisting of carbon nanotubes and Ni(OH)2 were developed by mixing the hydroxide and carbon nanotubes together in varous ratios. A maximum capacitance of 320 F•g－1 was obtained for the composite electrode containing 20％ carbon nanotubes compared with that of activated carbon(184 F•g－1). The performance of a newly designed combined electrochemical capacitor was evaluated. The capacitor was prepared by using nickel hydroxide/carbon nanotubes composite as a positive electrode and activated carbon as a negative electrode. Values for the specific energy and maximum specific power of 20.11 W•h•kg－1 and 8.6 W•g－1,respectively,were demonstrated for a cell voltage between 0 and 1.6 V. By using the modified anode of a Ni(OH)2/carbon nanotubes composite electrode, the combined supercapacitor exhibited high energy density and stable power characteristics.
2005, 21(02): 123-127
doi: 10.3866/PKU.WHXB20050203
Abstract:
This study was designed to explore the binding mode of pefloxacin mesylate(PFLX) with human serum albumin (HSA).Fluorescence spectroscopic results showed pefloxacin-HSA complex with binding constants of 1.7×105 L•mol－1.The enthalpy change (ΔrHm) and entropy change (ΔrSm) were measured by microcalorimetry to be 1.03 kJ•mol－1 and 101.28 J•K－1•mol－1,which indicated that hydrophobic interaction played a major role in the binding of PFLX with HSA. The possible binding domains of HSA for PFLX were studied by molecular modeling, which predicted that the hydrophobic interaction played a dominating role in this drug-protein interaction and PFLX could bind to Sudlow’s sites I and II of HSA. The binding energies obtained from the molecular modeling were in accordance with the experiment results.
This study was designed to explore the binding mode of pefloxacin mesylate(PFLX) with human serum albumin (HSA).Fluorescence spectroscopic results showed pefloxacin-HSA complex with binding constants of 1.7×105 L•mol－1.The enthalpy change (ΔrHm) and entropy change (ΔrSm) were measured by microcalorimetry to be 1.03 kJ•mol－1 and 101.28 J•K－1•mol－1,which indicated that hydrophobic interaction played a major role in the binding of PFLX with HSA. The possible binding domains of HSA for PFLX were studied by molecular modeling, which predicted that the hydrophobic interaction played a dominating role in this drug-protein interaction and PFLX could bind to Sudlow’s sites I and II of HSA. The binding energies obtained from the molecular modeling were in accordance with the experiment results.
2005, 21(02): 128-133
doi: 10.3866/PKU.WHXB20050204
Abstract:
The solubilities of the ternary CeCl3-CdCl2-H2O system and the quaternary CeCl3-CdCl2-HCl-H2O system were determined at 25 ℃,and the corresponding equilibrium diagrams were constructed. The results show that the ternary system was complicated with five equilibrim solid phases, and they are CdCl2•2.5H2O,CdCl2•H2O, 6CdCl2•CeCl3•14H2O (6:1 type), 4CdCl2•CeCl3•12H2O(4:1 type) and CeCl3•7H2O.The quaternary system was also complicated with five equilibrium solid phases, that is, CdCl2•H2O, 9CdCl2•CeCl3•19H2O (9:1 type), 6CdCl2•CeCl3•14H2O (6:1 type), 4CdCl2•CeCl3•12H2O (4:1 type) and CeCl3•7H2O.Three new compounds, 9CdCl2•CeCl3•19H2O, 6CdCl2•CeCl3•14H2O,and 4CdCl2•CeCl3•12H2O have not yet been reported in literatures, and they were congruently soluble in the quaternary.6CdCl2•CeCl3•14H2O was a kind of metastable compound in the ternary system, and it was changed into 4CdCl2•CeCl3•12H2O with time. Both 6:1 type and 4:1 type were non-congruently soluble compounds in the ternary system. The three new compounds have been prepared and have been characterized by XRD, TC-DTG, and DSC. X-ray powder diffraction patterns are indicated.
The solubilities of the ternary CeCl3-CdCl2-H2O system and the quaternary CeCl3-CdCl2-HCl-H2O system were determined at 25 ℃,and the corresponding equilibrium diagrams were constructed. The results show that the ternary system was complicated with five equilibrim solid phases, and they are CdCl2•2.5H2O,CdCl2•H2O, 6CdCl2•CeCl3•14H2O (6:1 type), 4CdCl2•CeCl3•12H2O(4:1 type) and CeCl3•7H2O.The quaternary system was also complicated with five equilibrium solid phases, that is, CdCl2•H2O, 9CdCl2•CeCl3•19H2O (9:1 type), 6CdCl2•CeCl3•14H2O (6:1 type), 4CdCl2•CeCl3•12H2O (4:1 type) and CeCl3•7H2O.Three new compounds, 9CdCl2•CeCl3•19H2O, 6CdCl2•CeCl3•14H2O,and 4CdCl2•CeCl3•12H2O have not yet been reported in literatures, and they were congruently soluble in the quaternary.6CdCl2•CeCl3•14H2O was a kind of metastable compound in the ternary system, and it was changed into 4CdCl2•CeCl3•12H2O with time. Both 6:1 type and 4:1 type were non-congruently soluble compounds in the ternary system. The three new compounds have been prepared and have been characterized by XRD, TC-DTG, and DSC. X-ray powder diffraction patterns are indicated.
2005, 21(02): 134-138
doi: 10.3866/PKU.WHXB20050205
Abstract:
Considering the limitation of now available adiabatic kinetic analysis, a method to calculate activation energy by dealing with pressure data obtained from the adiabatic measurement is proposed. New kinetic equation is established and the apparent activation energies for the thermal decomposition of di-tert-butyl peroxide and 2-methyl-4-nitrobenzenesulfonic acid are calculated. The obtained apparent activation energies are compared with the values in the literature and the values obtained from other methods, and the difference between them and the underlying reasons are discussed.
Considering the limitation of now available adiabatic kinetic analysis, a method to calculate activation energy by dealing with pressure data obtained from the adiabatic measurement is proposed. New kinetic equation is established and the apparent activation energies for the thermal decomposition of di-tert-butyl peroxide and 2-methyl-4-nitrobenzenesulfonic acid are calculated. The obtained apparent activation energies are compared with the values in the literature and the values obtained from other methods, and the difference between them and the underlying reasons are discussed.
2005, 21(02): 139-145
doi: 10.3866/PKU.WHXB20050206
Abstract:
A novel chiral Salen 1 and its dinuclear Salen Mn complex 2 (host) were synthesized and characterized by elemental analysis,1H NMR,FT-IR,UV-Vis, and CD spectra. The molecular recognition of 2 with imidazoles and pydines were studied by method of UV-Vis spectrophotometric titration, and it seems that the binding constants are in the orders of K(Im) > K(2-MeIm) > K(N-MeIm) (imidazoles), K(4-MePy) > K(3-MePy) > K(Py) (pydines). All of them have a coordination number of two. The thermodynamic functions ΔrHmθ,ΔrSmθ were also calculated. The results indicated that the processes were exothermic and entropy decreasing. CD spectra of recognition process were studied and the results were consistent with those of thermodynamics. Moreover, the lowest energy configurations of host-guest were obtained by simulated annealing, and quantum chemical calculation was performed based on these configurations. The experimental phenomena were confirmed by the results of quantum chemical calculation.
A novel chiral Salen 1 and its dinuclear Salen Mn complex 2 (host) were synthesized and characterized by elemental analysis,1H NMR,FT-IR,UV-Vis, and CD spectra. The molecular recognition of 2 with imidazoles and pydines were studied by method of UV-Vis spectrophotometric titration, and it seems that the binding constants are in the orders of K(Im) > K(2-MeIm) > K(N-MeIm) (imidazoles), K(4-MePy) > K(3-MePy) > K(Py) (pydines). All of them have a coordination number of two. The thermodynamic functions ΔrHmθ,ΔrSmθ were also calculated. The results indicated that the processes were exothermic and entropy decreasing. CD spectra of recognition process were studied and the results were consistent with those of thermodynamics. Moreover, the lowest energy configurations of host-guest were obtained by simulated annealing, and quantum chemical calculation was performed based on these configurations. The experimental phenomena were confirmed by the results of quantum chemical calculation.
2005, 21(02): 146-150
doi: 10.3866/PKU.WHXB20050207
Abstract:
The reaction of MCM-41 with tetramethyl tin was studied under high vacuum condition, and the composition, structure and properties of the resulted solid were characterized by element analysis, gas volumetry analysis, ICP, XRD, FTIR, DRS(diffuse reflectance spectroscopy), 13C and 119Sn MAS NMR, XPS, BET,TPD, TPR, adsorption of nitrogen etc., respectively. The results showed that the reaction occurred on the surface without destroying the framework structure of the zeolite, leading to the formation of the monografted species (≡Si－O)SnMe3 for MCM-41 at 773 K. Grafting methyltin species on the surface resulted in decrease of the pore size and the mesoporous volume of MCM-41. The reaction temperature of MCM-41 with tetramethyl tin was 343 K which is higher than that of HY zeolite with tetramethyl tin (193 K) and SnMe3/MCM-41 is thermal stable under 673 K and its thermal stability is higher than that of SnMe3/HY.
The reaction of MCM-41 with tetramethyl tin was studied under high vacuum condition, and the composition, structure and properties of the resulted solid were characterized by element analysis, gas volumetry analysis, ICP, XRD, FTIR, DRS(diffuse reflectance spectroscopy), 13C and 119Sn MAS NMR, XPS, BET,TPD, TPR, adsorption of nitrogen etc., respectively. The results showed that the reaction occurred on the surface without destroying the framework structure of the zeolite, leading to the formation of the monografted species (≡Si－O)SnMe3 for MCM-41 at 773 K. Grafting methyltin species on the surface resulted in decrease of the pore size and the mesoporous volume of MCM-41. The reaction temperature of MCM-41 with tetramethyl tin was 343 K which is higher than that of HY zeolite with tetramethyl tin (193 K) and SnMe3/MCM-41 is thermal stable under 673 K and its thermal stability is higher than that of SnMe3/HY.
2005, 21(02): 151-155
doi: 10.3866/PKU.WHXB20050208
Abstract:
The properties of several rhodopsin sequences were analyzed by comparing withα2A-adrenergic receptor, and a great similarity was found between bovine rhodopsin andα2A-adrenergic receptor. Therefore transmembrane helices ofα2A-adrenergic receptor were constructed homologically based on the bovine rhodopsin.In the newly constructed structure, a 0.090 nm3 active-site, which was enclosed by several reported active residues, was found. In succession, docking researches of this structure as well as point-mutated ones with inhibitor Yohimbine were conducted using molecular dynamics. The results agree well to the experimental results reported. Furthermore the docking results indicate that a small hydrophobic zone constructed by a tryptophan and two phenylalanines was critical in stabilizing the inhibitor in the active site. At the same time, aspartic acid 113 also weighs heavily to stabilize the inhibitor as a H-bond acceptor.
The properties of several rhodopsin sequences were analyzed by comparing withα2A-adrenergic receptor, and a great similarity was found between bovine rhodopsin andα2A-adrenergic receptor. Therefore transmembrane helices ofα2A-adrenergic receptor were constructed homologically based on the bovine rhodopsin.In the newly constructed structure, a 0.090 nm3 active-site, which was enclosed by several reported active residues, was found. In succession, docking researches of this structure as well as point-mutated ones with inhibitor Yohimbine were conducted using molecular dynamics. The results agree well to the experimental results reported. Furthermore the docking results indicate that a small hydrophobic zone constructed by a tryptophan and two phenylalanines was critical in stabilizing the inhibitor in the active site. At the same time, aspartic acid 113 also weighs heavily to stabilize the inhibitor as a H-bond acceptor.
2005, 21(02): 156-160
doi: 10.3866/PKU.WHXB20050209
Abstract:
Two systems of VOx/ZrO2 and K-VOx/ZrO2 catalysts with different compositions were prepared by incipient-wetness impregnation method. The catalytic performances of these catalysts for diesel soot catalytic oxidation were investigated with temperature-programmed oxidation reaction (TPO). The results showed that the catalytic properties of the VOx/ZrO2 catalysts depend on the VOx concentration. The VOx/ZrO2 catalyst has the best activity for soot oxidation when nV∶nZr is 4:100.The VOx/ZrO2 and K-VOx/ZrO2 catalysts were characterized by FT-IR and UV-Vis. The results revealed that the highest concentration of polymerized vanadyl species presented on the surfaces of the VOx/ZrO2 catalysts when nV∶nZr =4∶100.The polymerized vanadyl can lower the oxidation temperature of diesel soot because they have very strong redox abilities. The addition of potassium to VOx/ZrO2 catalysts can improve the catalytic activities for soot oxidation apparently. When nK∶nV∶nZr =1∶4∶100,the catalyst K-VOx/ZrO2 has the best activity for soot oxidation, i.e., the lowest reaction temperature. But the catalytic activity of the K- VOx/ZrO2 catalysts decreased when nK∶nV > 1∶4,which is due to the formation of KVO3 whose surface atoms mobility is much weaker than that of polymeric VOx specie and dispersed potassium oxide.
Two systems of VOx/ZrO2 and K-VOx/ZrO2 catalysts with different compositions were prepared by incipient-wetness impregnation method. The catalytic performances of these catalysts for diesel soot catalytic oxidation were investigated with temperature-programmed oxidation reaction (TPO). The results showed that the catalytic properties of the VOx/ZrO2 catalysts depend on the VOx concentration. The VOx/ZrO2 catalyst has the best activity for soot oxidation when nV∶nZr is 4:100.The VOx/ZrO2 and K-VOx/ZrO2 catalysts were characterized by FT-IR and UV-Vis. The results revealed that the highest concentration of polymerized vanadyl species presented on the surfaces of the VOx/ZrO2 catalysts when nV∶nZr =4∶100.The polymerized vanadyl can lower the oxidation temperature of diesel soot because they have very strong redox abilities. The addition of potassium to VOx/ZrO2 catalysts can improve the catalytic activities for soot oxidation apparently. When nK∶nV∶nZr =1∶4∶100,the catalyst K-VOx/ZrO2 has the best activity for soot oxidation, i.e., the lowest reaction temperature. But the catalytic activity of the K- VOx/ZrO2 catalysts decreased when nK∶nV > 1∶4,which is due to the formation of KVO3 whose surface atoms mobility is much weaker than that of polymeric VOx specie and dispersed potassium oxide.
2005, 21(02): 161-165
doi: 10.3866/PKU.WHXB20050210
Abstract:
Heavy alkylbenzene sulfonates (HABS) have been applied in enhanced oil recovery(EOR) for many years, but the effect of oil flooding is quiet different as variety of HABS composition. In this study, HABS was separated into 6 group-types with column chromatography, and dialkylbenzene, polyphenylalkane, monoalkylbenzene, alkylnaphthalene were sulfonated and purified. The interfacial tension (IFT) and the synergistic effect between these components were studied，and the mechanism and rules of the synergistic effect between HABS components were obtained from the EACN value of oil and the nmin values of HABS components. Moreover, the rules were further confirmed by the synergistic effect between LAS and the HABS components.
Heavy alkylbenzene sulfonates (HABS) have been applied in enhanced oil recovery(EOR) for many years, but the effect of oil flooding is quiet different as variety of HABS composition. In this study, HABS was separated into 6 group-types with column chromatography, and dialkylbenzene, polyphenylalkane, monoalkylbenzene, alkylnaphthalene were sulfonated and purified. The interfacial tension (IFT) and the synergistic effect between these components were studied，and the mechanism and rules of the synergistic effect between HABS components were obtained from the EACN value of oil and the nmin values of HABS components. Moreover, the rules were further confirmed by the synergistic effect between LAS and the HABS components.
2005, 21(02): 166-172
doi: 10.3866/PKU.WHXB20050211
Abstract:
On the basis of density functional theory, the reaction paths for ClO and ClO have been studied. The reactants, intermediates, transition states, and products have been optimized at the B3LYP/6-311＋＋(3df) level. IRC (intrinsic reaction coordinate) calculations have also been processed. The energies with zero point energy correction have been calculated, the characters of the major critical points have been discussed by topological analysis of the electronic density, and the chemical bonds have been discussed. The energy transition states (ETS) and structure transition states (STS) have been found.
On the basis of density functional theory, the reaction paths for ClO and ClO have been studied. The reactants, intermediates, transition states, and products have been optimized at the B3LYP/6-311＋＋(3df) level. IRC (intrinsic reaction coordinate) calculations have also been processed. The energies with zero point energy correction have been calculated, the characters of the major critical points have been discussed by topological analysis of the electronic density, and the chemical bonds have been discussed. The energy transition states (ETS) and structure transition states (STS) have been found.
2005, 21(02): 173-176
doi: 10.3866/PKU.WHXB20050212
Abstract:
The dependence of pair distribution function of molten compound AuCu3 on temperature under rapid cooling conditions has been researched by molecular dynamics simulation technique. It is concluded that there exists noncrystal structure at 700 K from the result that the second peak of g(r) of molten AuCu3 has been splitted into two sub-peaks. The feature of version of cluster in molten AuCu3 has been investigated by Honeycutt pair analysis technique. It is demonstrated that the structural configuration in molten AuCu3 has remarkable variation during the formation of noncrystal according to the relationship between the bonded pairs, polyhedron and temperatures. The defective polyhedra in liquid AuCu3 have greatest change accompanying the changing temperatures. The noncrystal is not “frozen liquid”.
The dependence of pair distribution function of molten compound AuCu3 on temperature under rapid cooling conditions has been researched by molecular dynamics simulation technique. It is concluded that there exists noncrystal structure at 700 K from the result that the second peak of g(r) of molten AuCu3 has been splitted into two sub-peaks. The feature of version of cluster in molten AuCu3 has been investigated by Honeycutt pair analysis technique. It is demonstrated that the structural configuration in molten AuCu3 has remarkable variation during the formation of noncrystal according to the relationship between the bonded pairs, polyhedron and temperatures. The defective polyhedra in liquid AuCu3 have greatest change accompanying the changing temperatures. The noncrystal is not “frozen liquid”.
2005, 21(02): 177-181
doi: 10.3866/PKU.WHXB20050213
Abstract:
New low-temperature molten salt electrolytes based on LiClO4 and acetamide with proper molar ratio appear as liquid at room temperature through they are composed of two solids and have excellent thermal stability and electrochemical properties. The mechanism of action has been studied by FT-IR spectroscopy, FT-Raman spectroscopy and quantum chemistry calculation with nonlocal DFT. The results indicated that acetamide can coordinate with Li＋ cation in the LiClO4-acetamide system through Li－O bonding. A big coordinate cation was formed and the coulombic force was weakened. Meanwhile, Li－O can also lead to the breakage of hydrogen bonding between acetamide molecules, resulting in the decrease of the co-molten temperature of the system compared with that of pure salt. A part of samples of this molten salt could exist stably in liquid state at room temperature.
New low-temperature molten salt electrolytes based on LiClO4 and acetamide with proper molar ratio appear as liquid at room temperature through they are composed of two solids and have excellent thermal stability and electrochemical properties. The mechanism of action has been studied by FT-IR spectroscopy, FT-Raman spectroscopy and quantum chemistry calculation with nonlocal DFT. The results indicated that acetamide can coordinate with Li＋ cation in the LiClO4-acetamide system through Li－O bonding. A big coordinate cation was formed and the coulombic force was weakened. Meanwhile, Li－O can also lead to the breakage of hydrogen bonding between acetamide molecules, resulting in the decrease of the co-molten temperature of the system compared with that of pure salt. A part of samples of this molten salt could exist stably in liquid state at room temperature.
2005, 21(02): 182-186
doi: 10.3866/PKU.WHXB20050214
Abstract:
Fe3O4/EDTA nano-composite particles with capability of chelating general metal ions and radio-nuclide metal ions were prepared, and characterized by IR, XRD, XPS, TEM, VSM(vibrating sample magnetometer) and AAS(atomic absorption spectrometer).Chelating agent EDTA was used for the surface modification of Fe3O4 magnetic particles with 20 nm in size. The effects of temperature of preparation process on the crystal form and magnetization, and the capability of the Fe3O4/EDTA nano-composite particles to chelate metal ions were investigated. The results showed that (1) the magnetization of the composite particles prepared at 50～70 ℃ modification condition was equal to that of unmodified Fe3O4 nanometer particles;(2) the stability against oxidization of the Fe3O4/EDTA composite particles was improved owing to the modification of the Fe3O4 particles by EDTA;(3) the composite particles could chelate several general metal ions, such as Cu(Ⅱ)、Ca(Ⅱ)、Mg(Ⅱ) and Ni(Ⅱ),due to that the surface of the Fe3O4/EDTA composite particles was possessed of chelating function groups.
Fe3O4/EDTA nano-composite particles with capability of chelating general metal ions and radio-nuclide metal ions were prepared, and characterized by IR, XRD, XPS, TEM, VSM(vibrating sample magnetometer) and AAS(atomic absorption spectrometer).Chelating agent EDTA was used for the surface modification of Fe3O4 magnetic particles with 20 nm in size. The effects of temperature of preparation process on the crystal form and magnetization, and the capability of the Fe3O4/EDTA nano-composite particles to chelate metal ions were investigated. The results showed that (1) the magnetization of the composite particles prepared at 50～70 ℃ modification condition was equal to that of unmodified Fe3O4 nanometer particles;(2) the stability against oxidization of the Fe3O4/EDTA composite particles was improved owing to the modification of the Fe3O4 particles by EDTA;(3) the composite particles could chelate several general metal ions, such as Cu(Ⅱ)、Ca(Ⅱ)、Mg(Ⅱ) and Ni(Ⅱ),due to that the surface of the Fe3O4/EDTA composite particles was possessed of chelating function groups.
2005, 21(02): 187-181
doi: 10.3866/PKU.WHXB20050215
Abstract:
Direct electrochemical behaviors of Hemoglobin(Hb) adsorbed on carbon paste electrode modified by carbon nano-tubes(CNTs) were investigated. Hb-CNT-modified electrode showed a pair of well-defined and nearly reversible cyclic voltammetric peaks for HbhemeFe(Ⅲ)/Fe(Ⅱ) redox couple in phosphate buffered saline solution(pH=7.0).The formal potential (E01) was －0.160 V (vs SCE),which was almost independent of the scan rate. The number of electron transferred (n) was 1.021,suggesting about an electron transfer between the heme group of Hb and the electrode. The average apparent heterogeneous electron transfer rate constant (ks) obtained by fitting CV data for Hb on CNT-modified electrode was 0.0816 s－1,greater than the value obtained from the same method for Hb with methylene blue as mediators. Hb-CNT-modified electrode showed a stable and significant catalytic activity for the electrochemical reduction of hydrogen peroxide, trichloroacetic acid and nitrobenzene.
Direct electrochemical behaviors of Hemoglobin(Hb) adsorbed on carbon paste electrode modified by carbon nano-tubes(CNTs) were investigated. Hb-CNT-modified electrode showed a pair of well-defined and nearly reversible cyclic voltammetric peaks for HbhemeFe(Ⅲ)/Fe(Ⅱ) redox couple in phosphate buffered saline solution(pH=7.0).The formal potential (E01) was －0.160 V (vs SCE),which was almost independent of the scan rate. The number of electron transferred (n) was 1.021,suggesting about an electron transfer between the heme group of Hb and the electrode. The average apparent heterogeneous electron transfer rate constant (ks) obtained by fitting CV data for Hb on CNT-modified electrode was 0.0816 s－1,greater than the value obtained from the same method for Hb with methylene blue as mediators. Hb-CNT-modified electrode showed a stable and significant catalytic activity for the electrochemical reduction of hydrogen peroxide, trichloroacetic acid and nitrobenzene.
2005, 21(02): 192-196
doi: 10.3866/PKU.WHXB20050216
Abstract:
In order to understand the mechanism of NOx removal in non-thermal plasma, the conversion of NO with different reacting gas mixtures under atmospheric pressure has been studied using dielectric barrier discharge plasma at 523 K. Experiments demonstrate that in the NO/N2 system, NO decomposition to N2 and O2 is in the majority. In the NO/O2/N2 system, NO conversion is the lowest for the formation of NO2 and NO. In the NO/C2H4/N2 system, NO is reduced to N2 at the same NO conversion as that in the NO/N2 system. Because the O atoms from NO decomposition are consumed more effectively by reaction of O and C2H4 than reaction of O and NO, NO2 formation is not observed. Dielectric barrier discharge is a very effective means for oxidizing NO to NO2 in the NO/O2/C2H4/N2 system. At the energy density of 125 J•L－1, NO conversion and concentration of NO2 formed in the NO/O2/C2H4/N2 system are the highest, the energy consumption is the lowest, 61 eV per converted NO molecule. C2H4 is mainly oxidized to CO in the dielectric barrier discharge plasma. A small amount of N2O is formed in the four systems. The in-situ optical emission spectra(200～900 nm) have also been investigated under atmospheric pressure at 523 K. The observations of N2 second positive band, NO γ-band and NO β-band with different gas mixtures imply that some excited-state active species from plasma-induced processes can effectively convert NO. Finally, mechanisms for the NO conversion in the four systems were proposed on the basis of experiment and relative literature.
In order to understand the mechanism of NOx removal in non-thermal plasma, the conversion of NO with different reacting gas mixtures under atmospheric pressure has been studied using dielectric barrier discharge plasma at 523 K. Experiments demonstrate that in the NO/N2 system, NO decomposition to N2 and O2 is in the majority. In the NO/O2/N2 system, NO conversion is the lowest for the formation of NO2 and NO. In the NO/C2H4/N2 system, NO is reduced to N2 at the same NO conversion as that in the NO/N2 system. Because the O atoms from NO decomposition are consumed more effectively by reaction of O and C2H4 than reaction of O and NO, NO2 formation is not observed. Dielectric barrier discharge is a very effective means for oxidizing NO to NO2 in the NO/O2/C2H4/N2 system. At the energy density of 125 J•L－1, NO conversion and concentration of NO2 formed in the NO/O2/C2H4/N2 system are the highest, the energy consumption is the lowest, 61 eV per converted NO molecule. C2H4 is mainly oxidized to CO in the dielectric barrier discharge plasma. A small amount of N2O is formed in the four systems. The in-situ optical emission spectra(200～900 nm) have also been investigated under atmospheric pressure at 523 K. The observations of N2 second positive band, NO γ-band and NO β-band with different gas mixtures imply that some excited-state active species from plasma-induced processes can effectively convert NO. Finally, mechanisms for the NO conversion in the four systems were proposed on the basis of experiment and relative literature.
2005, 21(02): 197-201
doi: 10.3866/PKU.WHXB20050217
Abstract:
A nano-hydroxyapatite coating on titanium substrate was directly prepared by electrochemical deposition method and was characterized by EDS,SEM, XRD and FTIR. It was observed that under a wide range of deposition conditions calcium-deficient hydroxyapatite coatings with different topographies can be prepared. Under a representative preparation condition, i.e. a titanium substrate was used as working electrode with a Pt electrode as counter electrode, the electrolyte was composed of 4.2×10－4 mol•L－1 Ca(NO3)2 , 2.5×10－4 mol•L－1 NaH2PO4 and 0.9％ NaCl, with a pH adjusted to be 6.0, and galvanostatic mode with 1 mA•cm－2 cathodic current density was applied at the temperature of 100 ℃, a series of hydroxyapatite coatings under different deposition durations (15, 30, 60, 120 and 240 min) were prepared and characterized to investigate the coating growth behavior. Following laws of coating growth were observed: (1) preferential growth with the c-axis of the hydroxyapatite crystal perpendicular to working surface is always detected in the XRD measurements with the peak of (002) crystal face being greatly intensified; (2) the growth of grains at inner layer is impeded by the growth of those at outer layer; when grains are packed closely, competition between the growths of grains at the same layer takes place; (3) the amount of deposited coating increases with deposition time while the chemical composition almost keeps the same.
A nano-hydroxyapatite coating on titanium substrate was directly prepared by electrochemical deposition method and was characterized by EDS,SEM, XRD and FTIR. It was observed that under a wide range of deposition conditions calcium-deficient hydroxyapatite coatings with different topographies can be prepared. Under a representative preparation condition, i.e. a titanium substrate was used as working electrode with a Pt electrode as counter electrode, the electrolyte was composed of 4.2×10－4 mol•L－1 Ca(NO3)2 , 2.5×10－4 mol•L－1 NaH2PO4 and 0.9％ NaCl, with a pH adjusted to be 6.0, and galvanostatic mode with 1 mA•cm－2 cathodic current density was applied at the temperature of 100 ℃, a series of hydroxyapatite coatings under different deposition durations (15, 30, 60, 120 and 240 min) were prepared and characterized to investigate the coating growth behavior. Following laws of coating growth were observed: (1) preferential growth with the c-axis of the hydroxyapatite crystal perpendicular to working surface is always detected in the XRD measurements with the peak of (002) crystal face being greatly intensified; (2) the growth of grains at inner layer is impeded by the growth of those at outer layer; when grains are packed closely, competition between the growths of grains at the same layer takes place; (3) the amount of deposited coating increases with deposition time while the chemical composition almost keeps the same.
2005, 21(02): 202-204
doi: 10.3866/PKU.WHXB20050218
Abstract:
The existing state of aluminum in aqueous aluminum citrate(AlCit) solution and the effect of pH value on it are investigated by 27Al NMR, atomic aborbance spetrum and dialysis. The experimental results show that there are two states of Al in AlCit solution, one is in molecular state, and the other is in colloidal state. When the pH value of solution is increased, the amount of the Al in molecular state is decreased, and the amount of the Al in colloidal state is increased gradually.
The existing state of aluminum in aqueous aluminum citrate(AlCit) solution and the effect of pH value on it are investigated by 27Al NMR, atomic aborbance spetrum and dialysis. The experimental results show that there are two states of Al in AlCit solution, one is in molecular state, and the other is in colloidal state. When the pH value of solution is increased, the amount of the Al in molecular state is decreased, and the amount of the Al in colloidal state is increased gradually.
2005, 21(02): 205-208
doi: 10.3866/PKU.WHXB20050219
Abstract:
The periodic precipitation patterns of calcium bilirubinate were produced in the metal ion-deoxycholate-bilirubinate diffusion system. By considering of the interactions among the bilirubinate, deoxycholate, Cu2＋ and Ca2＋, the growth regulations of periodic precipitation patterns were investigated. It was found that the deoxycholate and bilirubinate could form the reunited micelle that could diffuse and react with metal ions in agar gels. When meeting with Ca2＋, the bilirubinate will separate out from micelle to produce calcium bilirubinate. When meeting with Cu2＋＋Ca2＋ ions, deoxycholate would first unite with Cu2＋ ions, then the bilirubinate would further separate out from micelle and react with Ca2＋ ions to produce calcium bilirubinate. Because the reunited micelle has bigger volume and slower speed in diffusion and reaction, its duration to produce precipitation pattern is much longer (roughly 6 months), which is more like the duration of gallstone growth. It was also found that when the copper ions present, the durations of the pattern formation became shorter.
The periodic precipitation patterns of calcium bilirubinate were produced in the metal ion-deoxycholate-bilirubinate diffusion system. By considering of the interactions among the bilirubinate, deoxycholate, Cu2＋ and Ca2＋, the growth regulations of periodic precipitation patterns were investigated. It was found that the deoxycholate and bilirubinate could form the reunited micelle that could diffuse and react with metal ions in agar gels. When meeting with Ca2＋, the bilirubinate will separate out from micelle to produce calcium bilirubinate. When meeting with Cu2＋＋Ca2＋ ions, deoxycholate would first unite with Cu2＋ ions, then the bilirubinate would further separate out from micelle and react with Ca2＋ ions to produce calcium bilirubinate. Because the reunited micelle has bigger volume and slower speed in diffusion and reaction, its duration to produce precipitation pattern is much longer (roughly 6 months), which is more like the duration of gallstone growth. It was also found that when the copper ions present, the durations of the pattern formation became shorter.
2005, 21(02): 209-213
doi: 10.3866/PKU.WHXB20050220
Abstract:
The structure of C60 aggregation was controlled successfully by LB(Langmuir-Blodgett) technique using behenic acid(BA), arachic acid(AA), stearic acid(SA) and octadecanyl amine(OA) as the assistant material. Dynamic force microscopy(DFM) data showed that there were two kinds of structures for the special C60 assembly(molar ratio of nC60∶nSA∶nAA∶nOA=2∶3∶3∶4)∶one’s diameter was about 180 nm; the other was 30 nm. It indicated that the dents on top of the fatty chain in the LB films prevented the further aggregation and controlled the structures of the C60 aggregates. The size of C60 congeries was not uniform for the acid/amine with the same chain length or with other molar ratio, and there was only one kind of structure for these C60 assemblies. UV-Vis absorption spectrum also indicated that the C60 molecules aggregated in some extent in the LB films, which was relevant to the DFM data.
The structure of C60 aggregation was controlled successfully by LB(Langmuir-Blodgett) technique using behenic acid(BA), arachic acid(AA), stearic acid(SA) and octadecanyl amine(OA) as the assistant material. Dynamic force microscopy(DFM) data showed that there were two kinds of structures for the special C60 assembly(molar ratio of nC60∶nSA∶nAA∶nOA=2∶3∶3∶4)∶one’s diameter was about 180 nm; the other was 30 nm. It indicated that the dents on top of the fatty chain in the LB films prevented the further aggregation and controlled the structures of the C60 aggregates. The size of C60 congeries was not uniform for the acid/amine with the same chain length or with other molar ratio, and there was only one kind of structure for these C60 assemblies. UV-Vis absorption spectrum also indicated that the C60 molecules aggregated in some extent in the LB films, which was relevant to the DFM data.
2005, 21(02): 214-217
doi: 10.3866/PKU.WHXB20050221
Abstract:
Classical trajectory calculation based on extended London-Eying-Polanyi-Sato (LEPS) potential energy surface (PES) is carried out to study the dependence of the energy partition among the reaction product molecules on the properties of PES and the reaction dynamic conditions. All the PESes have different topological-structures, which can be described by 6 features, and the reaction conditions can be described by 7 features. By this method, 3 sample collections are obtained. Then, the methodology of pattern recognition is used to analyze the relationship between the observables and the PESes and the reaction conditions. After the analysis, some known rules are obtained. We also found that the multiplication between different features has more important effect than single features. By pattern recognition, 3 discrimination equations are obtained, which only have 3,4,2 different features but not the whole 13 features. The 3 discrimination equations can be used to predict the behavior of unknown samples.
Classical trajectory calculation based on extended London-Eying-Polanyi-Sato (LEPS) potential energy surface (PES) is carried out to study the dependence of the energy partition among the reaction product molecules on the properties of PES and the reaction dynamic conditions. All the PESes have different topological-structures, which can be described by 6 features, and the reaction conditions can be described by 7 features. By this method, 3 sample collections are obtained. Then, the methodology of pattern recognition is used to analyze the relationship between the observables and the PESes and the reaction conditions. After the analysis, some known rules are obtained. We also found that the multiplication between different features has more important effect than single features. By pattern recognition, 3 discrimination equations are obtained, which only have 3,4,2 different features but not the whole 13 features. The 3 discrimination equations can be used to predict the behavior of unknown samples.
2005, 21(02): 218-220
doi: 10.3866/PKU.WHXB20050222
Abstract:
Thermal decomposition of NaNH4CrO4•2H2O was studied by means of thermogravimetric analysis (TG),differential thermogravimetric (DTG), differential thermal analysis (DTA) and X-ray diffraction (XRD). The results showed that the thermal decomposition of NaNH4CrO4•2H2O proceeds in three steps, i.e., the release of crystal water at temperature from 50 ℃ to 95 ℃ at first, the formation of the intermediates sodium chromate and ammonium dichromate with the partial release of ammonia at temperature from 100 ℃ to 180 ℃,and the complete elimination of ammonia from 215 ℃ to 385 ℃ .In flowing ambient and suitable temperature（400～790 ℃）,the final decomposition product was mostly sodium dichromate. This leads to a cleaner process for sodium dichromate production.
Thermal decomposition of NaNH4CrO4•2H2O was studied by means of thermogravimetric analysis (TG),differential thermogravimetric (DTG), differential thermal analysis (DTA) and X-ray diffraction (XRD). The results showed that the thermal decomposition of NaNH4CrO4•2H2O proceeds in three steps, i.e., the release of crystal water at temperature from 50 ℃ to 95 ℃ at first, the formation of the intermediates sodium chromate and ammonium dichromate with the partial release of ammonia at temperature from 100 ℃ to 180 ℃,and the complete elimination of ammonia from 215 ℃ to 385 ℃ .In flowing ambient and suitable temperature（400～790 ℃）,the final decomposition product was mostly sodium dichromate. This leads to a cleaner process for sodium dichromate production.
2005, 21(02): 221-224
doi: 10.3866/PKU.WHXB20050223
Abstract:
Al2O3 bulk aerogels were prepared by using Al(H2O)9(NO3)3 as a precursor and 1,2-epoxy propane as a gelation agent. Methane amide was used as drying control chemical additives (DCCA) to improve the gel texture and the structure evolution. Wet gels were aged by a successively solvent exchanging of alcohol, tetra-ethylorthosilicate (TEOS)/alcohol and alcohol at a certain temperature. The aged gels were dried at the non-supercritical fluid drying condition to obtain bulk alumina aerogels. Those aerogels had high surface areas and porosity. The mechanism about drying Al2O3 wet gels at an ambient pressure was also discussed.
Al2O3 bulk aerogels were prepared by using Al(H2O)9(NO3)3 as a precursor and 1,2-epoxy propane as a gelation agent. Methane amide was used as drying control chemical additives (DCCA) to improve the gel texture and the structure evolution. Wet gels were aged by a successively solvent exchanging of alcohol, tetra-ethylorthosilicate (TEOS)/alcohol and alcohol at a certain temperature. The aged gels were dried at the non-supercritical fluid drying condition to obtain bulk alumina aerogels. Those aerogels had high surface areas and porosity. The mechanism about drying Al2O3 wet gels at an ambient pressure was also discussed.
2005, 21(02): 225-228
doi: 10.3866/PKU.WHXB20050224
Abstract:
The adsorption behaviors of CO2 and CO2＋H2 on zirconia polymorphs were investigated by FT-IR technique. The results showed that absorbed CO2 and surface intermediates varied with zirconia polymorphs. Bicarbonate and ion carbonate species were detected on amorphous zirconia. In addition to the two species, bidented carbonate was also formed on monoclinic zirconia. The strongest adsorbed CO2 and polydentate carbonate species were found on tetra nal zirconia. In the case of CO2 hydrogenation, methane was formed on monoclinic zirconia while formate species was observed on tetra nal zirconia.
The adsorption behaviors of CO2 and CO2＋H2 on zirconia polymorphs were investigated by FT-IR technique. The results showed that absorbed CO2 and surface intermediates varied with zirconia polymorphs. Bicarbonate and ion carbonate species were detected on amorphous zirconia. In addition to the two species, bidented carbonate was also formed on monoclinic zirconia. The strongest adsorbed CO2 and polydentate carbonate species were found on tetra nal zirconia. In the case of CO2 hydrogenation, methane was formed on monoclinic zirconia while formate species was observed on tetra nal zirconia.
