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2004 Volume 20 Issue 6
2004, 20(06): 561-564
doi: 10.3866/PKU.WHXB20040601
Abstract:
A binary charge transfer complex—dipropylamine tetracyanoquinodimethane(DPA(TCNQ)2) was synthesized. Using STM we studied the surface topography of the single crystal and observed the molecular arrangement of the ab plane. Section analysis indicates that the surface lattice constants are in nice agreement with the XRD data of the bulk lattice constants. We successfully wrote information dot array on the crystal surface with a writing probability of 100％. Experimental results indicate that pulse width has strong influence on the threshold voltage for hole formation. This result does not support the typical field-induced evaporation mechanism but strongly supports the thermochemical hole burning (THB) mechanism.
A binary charge transfer complex—dipropylamine tetracyanoquinodimethane(DPA(TCNQ)2) was synthesized. Using STM we studied the surface topography of the single crystal and observed the molecular arrangement of the ab plane. Section analysis indicates that the surface lattice constants are in nice agreement with the XRD data of the bulk lattice constants. We successfully wrote information dot array on the crystal surface with a writing probability of 100％. Experimental results indicate that pulse width has strong influence on the threshold voltage for hole formation. This result does not support the typical field-induced evaporation mechanism but strongly supports the thermochemical hole burning (THB) mechanism.
2004, 20(06): 565-568
doi: 10.3866/PKU.WHXB20040602
Abstract:
A series of charge transfer complexes containing iodine were synthesized and the thermochemical hole burning properties of these materials were investigated. Experimental results suggest that dot array can be written on the crystal surface of all these materials using scanning tunneling microscope. It was found that the decomposition temperature has remarkable influence on the threshold voltage for hole burning. This results from the fact that, the activation energy has strong influence on the hole burning reaction rate, and the decomposition temperature is a measure of the activation energy. The influence of decomposition temperature on the threshold voltage is consistent with the principle of material design of thermochemical hole burning.
A series of charge transfer complexes containing iodine were synthesized and the thermochemical hole burning properties of these materials were investigated. Experimental results suggest that dot array can be written on the crystal surface of all these materials using scanning tunneling microscope. It was found that the decomposition temperature has remarkable influence on the threshold voltage for hole burning. This results from the fact that, the activation energy has strong influence on the hole burning reaction rate, and the decomposition temperature is a measure of the activation energy. The influence of decomposition temperature on the threshold voltage is consistent with the principle of material design of thermochemical hole burning.
2004, 20(06): 569-572
doi: 10.3866/PKU.WHXB20040603
Abstract:
The paper proposed a possible binding mode of MS-275, a benzamide histone deacetylase (HDAC) inhibitor, to HDAC by intensive docking study. This binding mode is different from those observed in the crystal structure of complexes formed by a histone deacetylase-like protein (HDLP) with trichostatin A (TSA) or suberoylanilide hydroxamic acid (SAHA). The docking result implicates that the main target of MS-275 is the narrowest part of HDAC active pocket. It seems to be able to explain the low toxicity of MS-275 and provides new insights on the design of novel HDAC inhibitors.
The paper proposed a possible binding mode of MS-275, a benzamide histone deacetylase (HDAC) inhibitor, to HDAC by intensive docking study. This binding mode is different from those observed in the crystal structure of complexes formed by a histone deacetylase-like protein (HDLP) with trichostatin A (TSA) or suberoylanilide hydroxamic acid (SAHA). The docking result implicates that the main target of MS-275 is the narrowest part of HDAC active pocket. It seems to be able to explain the low toxicity of MS-275 and provides new insights on the design of novel HDAC inhibitors.
2004, 20(06): 573-576
doi: 10.3866/PKU.WHXB20040604
Abstract:
Ca-containing Endohedral Metallofullerenes were synthesized by DC arc discharge method.C88 and C90-based group-2 metallofullerenes, Ca@C88 and Ca@C90 (I, II),were first isolated by multi-stage high-performance liquid chromatography (HPLC).All species were characterized by MAL-DI-TOF MS and UV-Vis-NIR absorption spectroscopy. Their electronic structure and possible molecular symmetries were discussed according to their retention times and absorption spectra.
Ca-containing Endohedral Metallofullerenes were synthesized by DC arc discharge method.C88 and C90-based group-2 metallofullerenes, Ca@C88 and Ca@C90 (I, II),were first isolated by multi-stage high-performance liquid chromatography (HPLC).All species were characterized by MAL-DI-TOF MS and UV-Vis-NIR absorption spectroscopy. Their electronic structure and possible molecular symmetries were discussed according to their retention times and absorption spectra.
2004, 20(06): 577-581
doi: 10.3866/PKU.WHXB20040605
Abstract:
The three-dimensional quantitative structure-activity relationships of new sulfonylureas, related to their herbicidal activity, were systematically studied using the comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA).For CoMFA, the influence of different grid spaces on the structure-activity relationship was investigated, the results show that the grid space of 0.20 nm is the best, and the contributions of rcv2 steric and electrostatic fields to the activity are 0.791 and 0.209 respectively. The cross-validated and the relation coefficient r2 for the model established by the study are 0.806 and 0.995 respectively, with a F value of 401.553 and a standard deviation (s) of 0.087.For CoMSIA, the influence of variations of grid spaces and combinations of all kinds of field types was studied. It was found that the most satisfactory 3D-QSAR models could be constructed by taking into account of the components of steric, hydrophobic and H-bond acceptor with the grid space of 0.20 nm. The results indicate that two models are significant and have od predictability and the resulting 3D contour maps provide useful guidance for designing highly active compounds prior to their synthesis.
The three-dimensional quantitative structure-activity relationships of new sulfonylureas, related to their herbicidal activity, were systematically studied using the comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA).For CoMFA, the influence of different grid spaces on the structure-activity relationship was investigated, the results show that the grid space of 0.20 nm is the best, and the contributions of rcv2 steric and electrostatic fields to the activity are 0.791 and 0.209 respectively. The cross-validated and the relation coefficient r2 for the model established by the study are 0.806 and 0.995 respectively, with a F value of 401.553 and a standard deviation (s) of 0.087.For CoMSIA, the influence of variations of grid spaces and combinations of all kinds of field types was studied. It was found that the most satisfactory 3D-QSAR models could be constructed by taking into account of the components of steric, hydrophobic and H-bond acceptor with the grid space of 0.20 nm. The results indicate that two models are significant and have od predictability and the resulting 3D contour maps provide useful guidance for designing highly active compounds prior to their synthesis.
2004, 20(06): 582-586
doi: 10.3866/PKU.WHXB20040606
Abstract:
Two different methods(mechanical ball-milling and co-precipitation)were applied to prepare lithium iron phosphate(LiFePO4) containing low concentration(1％, mole fraction) Cr3＋ ion dopant. The samples were characterized by X-ray diffraction and scanning electron microscope, and their electrochemical performances were investigated including cycling behavior and large current discharging. The results indicate that the Cr3＋ ion dopant does not affect the structure of the material but considerably improves its kinetics in terms of capacity delivery and cycle performance. At a low discharging rate (0.1 C), LiFePO4 samples doping via mechanical ball-milling and co-precipitation are capable of delivering reversible specific capacities of 144 mAh•g－1 and 158 mAh•g－1 respectively, with fairly stable cycleability. Even at a 2 C discharging rate, they can show capacities of 110 mAh•g－1 and 130 mAh•g－1 respectively, too. The results also confirm that doping via co-precipitation with Fe sources is an effective method to improve the ion doping effect.
Two different methods(mechanical ball-milling and co-precipitation)were applied to prepare lithium iron phosphate(LiFePO4) containing low concentration(1％, mole fraction) Cr3＋ ion dopant. The samples were characterized by X-ray diffraction and scanning electron microscope, and their electrochemical performances were investigated including cycling behavior and large current discharging. The results indicate that the Cr3＋ ion dopant does not affect the structure of the material but considerably improves its kinetics in terms of capacity delivery and cycle performance. At a low discharging rate (0.1 C), LiFePO4 samples doping via mechanical ball-milling and co-precipitation are capable of delivering reversible specific capacities of 144 mAh•g－1 and 158 mAh•g－1 respectively, with fairly stable cycleability. Even at a 2 C discharging rate, they can show capacities of 110 mAh•g－1 and 130 mAh•g－1 respectively, too. The results also confirm that doping via co-precipitation with Fe sources is an effective method to improve the ion doping effect.
2004, 20(06): 587-592
doi: 10.3866/PKU.WHXB20040607
Abstract:
The crystal structures of the TGEV 3CL proteinase is used to study the electrostatic and hydrophobic interactions between two monomers. Solving the Poisson-Boltzmanne equation using the finite difference method is used to calculate the electrostatic potential. The solvent accessible surface model is supplied for the molecular surface and hydrophobicity. The electrostatic and hydrophobic interactions are explored in the condition of different pH values. The electrostatic interaction energy, electrostatic desolvation free energy, and hydrophobic desolvation free energy show smaller values when pH values are between 5.5 and 8.5, which indicates that, in the condition, the electrostatic and hydrophobic interaction are favorable to the stability of the TGEV 3CL proteinase dimer. The results are consistent with the experimental condition for the crystallization of the TGEV 3CL proteinase dimer. pH values have stronger influence on the electrostatic desolvation free energy than on the hydrophobic desolvation free energy, which implies that the electrostatic interaction is the key factor to the instability of the TGEV 3Cl proteinase dimer in acid or alkali condition.
The crystal structures of the TGEV 3CL proteinase is used to study the electrostatic and hydrophobic interactions between two monomers. Solving the Poisson-Boltzmanne equation using the finite difference method is used to calculate the electrostatic potential. The solvent accessible surface model is supplied for the molecular surface and hydrophobicity. The electrostatic and hydrophobic interactions are explored in the condition of different pH values. The electrostatic interaction energy, electrostatic desolvation free energy, and hydrophobic desolvation free energy show smaller values when pH values are between 5.5 and 8.5, which indicates that, in the condition, the electrostatic and hydrophobic interaction are favorable to the stability of the TGEV 3CL proteinase dimer. The results are consistent with the experimental condition for the crystallization of the TGEV 3CL proteinase dimer. pH values have stronger influence on the electrostatic desolvation free energy than on the hydrophobic desolvation free energy, which implies that the electrostatic interaction is the key factor to the instability of the TGEV 3Cl proteinase dimer in acid or alkali condition.
2004, 20(06): 593-597
doi: 10.3866/PKU.WHXB20040608
Abstract:
Nano-fibrous polyaniline (PANI) film was synthesized by pulse galvanostatic method (PGM) and the electrodes of the nano-fibrous PANI film were used to construct electrochemical capacitor in this paper. The scanning electron microscopy result shows that the nano-fibrous PANI has a diameter of about 100 nm and a length of several micrometers. The PANI electrochemical capacitor was characterized by cyclic voltammetry, galvanostatic charge/discharge and ac impedance in NaClO4＋HClO4 mixed electrolyte. The results show that, the supercapacitor constructed by nano-fibrous PANI contains larger capacitance than capacitors constructed by granular PANI, which is prepared by galvanostatic method (GM) with the same deposited charge as PGM. From charge/discharge studies of nano-fibrous polyaniline capacitor, a specific capacitance of 699 F•g－1 and a specific energy density of 54.6 Wh•kg－1 have been obtained at discharge current density of 3.5 mA•cm－2. The PANI supercapacitor also shows little degradation of capacitance after long cycles. All results suggest that the nano-fibrous PANI is a prospect material for supercapacitor.
Nano-fibrous polyaniline (PANI) film was synthesized by pulse galvanostatic method (PGM) and the electrodes of the nano-fibrous PANI film were used to construct electrochemical capacitor in this paper. The scanning electron microscopy result shows that the nano-fibrous PANI has a diameter of about 100 nm and a length of several micrometers. The PANI electrochemical capacitor was characterized by cyclic voltammetry, galvanostatic charge/discharge and ac impedance in NaClO4＋HClO4 mixed electrolyte. The results show that, the supercapacitor constructed by nano-fibrous PANI contains larger capacitance than capacitors constructed by granular PANI, which is prepared by galvanostatic method (GM) with the same deposited charge as PGM. From charge/discharge studies of nano-fibrous polyaniline capacitor, a specific capacitance of 699 F•g－1 and a specific energy density of 54.6 Wh•kg－1 have been obtained at discharge current density of 3.5 mA•cm－2. The PANI supercapacitor also shows little degradation of capacitance after long cycles. All results suggest that the nano-fibrous PANI is a prospect material for supercapacitor.
2004, 20(06): 598-601
doi: 10.3866/PKU.WHXB20040609
Abstract:
Fe3O4 nanoparticles were introduced into microporous poly(vinylidene fluoride) (PVDF)membrane by in-situ membrane phase permeating method and a magnetic composite Fe3O4/PVDF membrane was prepared. Optimum preparation conditions were studied. FT-IR and DSC study indicates that the introducing of Fe3O4 did not affect the PVDF structure and the composite membranes show od thermo-stability. Fe3O4 particle size calculated from XRD result is about 68 nm. The susceptibility of the resulting composite membrane reached 0.044 cm3•g－1 and changed with reaction conditions. The variations of pore size of the composite membrane were investigated by gas permeating method. The maximum and average pore size, as well as pore size distribution, of the composite membranes are different from those of PVDF host membrane, and changed obviously with preparing conditions.
Fe3O4 nanoparticles were introduced into microporous poly(vinylidene fluoride) (PVDF)membrane by in-situ membrane phase permeating method and a magnetic composite Fe3O4/PVDF membrane was prepared. Optimum preparation conditions were studied. FT-IR and DSC study indicates that the introducing of Fe3O4 did not affect the PVDF structure and the composite membranes show od thermo-stability. Fe3O4 particle size calculated from XRD result is about 68 nm. The susceptibility of the resulting composite membrane reached 0.044 cm3•g－1 and changed with reaction conditions. The variations of pore size of the composite membrane were investigated by gas permeating method. The maximum and average pore size, as well as pore size distribution, of the composite membranes are different from those of PVDF host membrane, and changed obviously with preparing conditions.
2004, 20(06): 602-607
doi: 10.3866/PKU.WHXB20040610
Abstract:
This paper aimed at the dispersancy of lubricant succinimide dispersants. The molecular and mesoscale simulation methods were integrated to study the impact factors such as dispersant structure, concentration, and interaction with lubricant on the dispersancy. The mesoscopic parameters of succinimide polar groups were evaluated by the BLEND method of Cerius2 software. The dissipative particle dynamics simulation was used for lubricant-soot-dispersant systems. The simulated results are gualitatively consistent with experiments by the comparison between macro-index and micro-index to each system’s dispersing performance. The simulation results can give theoretical guidance to the molecular design for dispersants.
This paper aimed at the dispersancy of lubricant succinimide dispersants. The molecular and mesoscale simulation methods were integrated to study the impact factors such as dispersant structure, concentration, and interaction with lubricant on the dispersancy. The mesoscopic parameters of succinimide polar groups were evaluated by the BLEND method of Cerius2 software. The dissipative particle dynamics simulation was used for lubricant-soot-dispersant systems. The simulated results are gualitatively consistent with experiments by the comparison between macro-index and micro-index to each system’s dispersing performance. The simulation results can give theoretical guidance to the molecular design for dispersants.
2004, 20(06): 608-611
doi: 10.3866/PKU.WHXB20040611
Abstract:
With hydroxyapatite nanoparticles as the starting material, porous hydroxyapatite nanosolid was prepared by a unique solvothermal hot press method. The samples were characterized by X-ray diffraction, scanning electron microscope and thermal analysis method. The effects of solvent species and the uniformity of the distribution of solvents on the pore volume and pore radius of the porous hydroxyapatite nanosolids were investigated. Besides, the thermal stability of the porous hydroxyapatite nanosolids was also examined.
With hydroxyapatite nanoparticles as the starting material, porous hydroxyapatite nanosolid was prepared by a unique solvothermal hot press method. The samples were characterized by X-ray diffraction, scanning electron microscope and thermal analysis method. The effects of solvent species and the uniformity of the distribution of solvents on the pore volume and pore radius of the porous hydroxyapatite nanosolids were investigated. Besides, the thermal stability of the porous hydroxyapatite nanosolids was also examined.
2004, 20(06): 612-615
doi: 10.3866/PKU.WHXB20040612
Abstract:
The effects of sulfite on the etching processes of silicon and silica in 40％(w) NH4F aqueous solution have been studied by a method based on photolithography and atomic force microscopy (AFM). It is demonstrated that the silicon and silica etching rates depend on the sulfite concentrations. The spectra of the F 1s core level in the high-resolution X-ray photoelectron spectroscopy (XPS) for surfaces treated in solutions with/without sulfite suggest the chemistry of the surfaces is different in the two cases. The experimental results indicate that sulfite not only acts as an oxygen scavenger, but also influences the surface reactions in the wetting etching of Si and SiO2.
The effects of sulfite on the etching processes of silicon and silica in 40％(w) NH4F aqueous solution have been studied by a method based on photolithography and atomic force microscopy (AFM). It is demonstrated that the silicon and silica etching rates depend on the sulfite concentrations. The spectra of the F 1s core level in the high-resolution X-ray photoelectron spectroscopy (XPS) for surfaces treated in solutions with/without sulfite suggest the chemistry of the surfaces is different in the two cases. The experimental results indicate that sulfite not only acts as an oxygen scavenger, but also influences the surface reactions in the wetting etching of Si and SiO2.
2004, 20(06): 616-620
doi: 10.3866/PKU.WHXB20040613
Abstract:
The cocatalysis of adsorbed Eu3＋ or Ho3＋ for the ethanol electrooxidation at Pt-TiO2/C electrode was investigated with the cyclic voltammetric technique. It was found that the electrocatalytic activities of the Pt-TiO2-Ho3＋/C and Pt-TiO2-Eu3＋/C electrodes are better than that of the Pt-TiO2/C electrode both in acidic and neutral solutions. It can be explained as follows. When ethanol is electrooxidized, the intermediates, such as CO and COH can be formed. These species would be strongly adsorbed on the Pt surface and decrease the electrocatalytic activity for the ethanol oxidation. Both Eu3＋ and Ho3＋ can strongly coordinate with H2O, forming OH species, which can accelerate the electrooxidation of the strongly adsorbed CO. Therefore, Both Eu3＋ and Ho3＋ show the promoting action for the electrooxidation of ethanol.
The cocatalysis of adsorbed Eu3＋ or Ho3＋ for the ethanol electrooxidation at Pt-TiO2/C electrode was investigated with the cyclic voltammetric technique. It was found that the electrocatalytic activities of the Pt-TiO2-Ho3＋/C and Pt-TiO2-Eu3＋/C electrodes are better than that of the Pt-TiO2/C electrode both in acidic and neutral solutions. It can be explained as follows. When ethanol is electrooxidized, the intermediates, such as CO and COH can be formed. These species would be strongly adsorbed on the Pt surface and decrease the electrocatalytic activity for the ethanol oxidation. Both Eu3＋ and Ho3＋ can strongly coordinate with H2O, forming OH species, which can accelerate the electrooxidation of the strongly adsorbed CO. Therefore, Both Eu3＋ and Ho3＋ show the promoting action for the electrooxidation of ethanol.
2004, 20(06): 621-625
doi: 10.3866/PKU.WHXB20040614
Abstract:
In the present work, the influence of silver deposition on the transfer of photogenerated electrons was investigated. The catalyst was characterized by in-situ EPR, DRS, BET and phenol degradation under different conditions. The result showed that suitable size of silver cluster deposition can attract photogenerated electrons effectively and then the electrons transferred to the adsorbed oxygen and surface Ti4＋ efficiently. The recombination of the photogenerated electrons and holes was inhibited. The enhanced photocatalytic activity was mainly caused by the increased amount of reactive species, the higher amount of surface reactive center Ti3＋ and photogenerated holes.
In the present work, the influence of silver deposition on the transfer of photogenerated electrons was investigated. The catalyst was characterized by in-situ EPR, DRS, BET and phenol degradation under different conditions. The result showed that suitable size of silver cluster deposition can attract photogenerated electrons effectively and then the electrons transferred to the adsorbed oxygen and surface Ti4＋ efficiently. The recombination of the photogenerated electrons and holes was inhibited. The enhanced photocatalytic activity was mainly caused by the increased amount of reactive species, the higher amount of surface reactive center Ti3＋ and photogenerated holes.
2004, 20(06): 626-630
doi: 10.3866/PKU.WHXB20040615
Abstract:
The molar heat capacities of the azeotrope in the binary system of water and ethanol were measured by an adiabatic calorimeter in the temperature range from 78 K to 320 K. The functions of the heat capacity with respect to the thermodynamic temperature were established. The glass transition occurred at 98.496 K. The phase transitions took place in the temperature ranges from 123.08 K to 156.96 K and 269.03 K to 273.20 K corresponding to the solid-solid phase transition of ethanol, solid-liquid phase transition of ethanol, and solid-liquid phase transition of water, respectively. The thermodynamic functions and the excess thermodynamic functions of the azeotrope relative to 298.15 K were derived based on the relationships of the thermodynamic functions and the function of the measured heat capacity with respect to the temperature.
The molar heat capacities of the azeotrope in the binary system of water and ethanol were measured by an adiabatic calorimeter in the temperature range from 78 K to 320 K. The functions of the heat capacity with respect to the thermodynamic temperature were established. The glass transition occurred at 98.496 K. The phase transitions took place in the temperature ranges from 123.08 K to 156.96 K and 269.03 K to 273.20 K corresponding to the solid-solid phase transition of ethanol, solid-liquid phase transition of ethanol, and solid-liquid phase transition of water, respectively. The thermodynamic functions and the excess thermodynamic functions of the azeotrope relative to 298.15 K were derived based on the relationships of the thermodynamic functions and the function of the measured heat capacity with respect to the temperature.
2004, 20(06): 631-636
doi: 10.3866/PKU.WHXB20040616
Abstract:
The semiconducting properties of the oxide film formed on chromium were studied by capacitance measurement and the Mott-Schottky analysis. It is shown that the oxide films formed on chromium within the passive potential region in 0.5 mol•L－1 H2SO4 solution, the thickness of which is about 1.2±0.3 nm, behavior like a p-type semiconductor. The impedance response of the film showed a low-frequency dispersion, which can be accounted for by dielectric relaxation with complex capacitance. The effects of the film-formation potential, the polarization time, and the solution pH on the semiconductive parameters of acceptor density (NA) and flatband potential (EFB) were investigated. The increase of NA corresponds to the increase of the hydration degree of the oxide films. The linear relationship with a slope of ～59 mV/pH unit between EFB and solution pH was observed.
The semiconducting properties of the oxide film formed on chromium were studied by capacitance measurement and the Mott-Schottky analysis. It is shown that the oxide films formed on chromium within the passive potential region in 0.5 mol•L－1 H2SO4 solution, the thickness of which is about 1.2±0.3 nm, behavior like a p-type semiconductor. The impedance response of the film showed a low-frequency dispersion, which can be accounted for by dielectric relaxation with complex capacitance. The effects of the film-formation potential, the polarization time, and the solution pH on the semiconductive parameters of acceptor density (NA) and flatband potential (EFB) were investigated. The increase of NA corresponds to the increase of the hydration degree of the oxide films. The linear relationship with a slope of ～59 mV/pH unit between EFB and solution pH was observed.
2004, 20(06): 637-641
doi: 10.3866/PKU.WHXB20040617
Abstract:
MoO2 nano-arrays were simply prepared by reduction of thermally diffused MoO3 on anodic aluminum oxide(AAO) template. The structure and morphology of the nano-arrays were studied by XRD, SEM, TEM and HRTEM. The results showed that, after hydrogenation of the evaporates under 600 ℃ in H2/N2 mixture, single crystalline MoO2 nanotubes/nanowires were produced on 70 nm AAO template, while on 50 nm AAO template yielded was the piling-up of MoO2 nanocrystallites in nanotubes. Addition of ethanol into the powdered MoO3 precursors greatly improved the morphology of the nanowires. Further reduction of MoO2 at above 650 ℃ in H2 led to the production of Mo nanotube arrays.
MoO2 nano-arrays were simply prepared by reduction of thermally diffused MoO3 on anodic aluminum oxide(AAO) template. The structure and morphology of the nano-arrays were studied by XRD, SEM, TEM and HRTEM. The results showed that, after hydrogenation of the evaporates under 600 ℃ in H2/N2 mixture, single crystalline MoO2 nanotubes/nanowires were produced on 70 nm AAO template, while on 50 nm AAO template yielded was the piling-up of MoO2 nanocrystallites in nanotubes. Addition of ethanol into the powdered MoO3 precursors greatly improved the morphology of the nanowires. Further reduction of MoO2 at above 650 ℃ in H2 led to the production of Mo nanotube arrays.
2004, 20(06): 642-646
doi: 10.3866/PKU.WHXB20040618
Abstract:
All species involved in the multi-channel reaction of an oxygen atom with a fluorinated methyl radical have been investigated using density functional theory (DFT). The geometries of the reactants, intermediates, transition states and products are optimized at the B3LYP/6-311＋＋G(2d, 2p) level. The potential energy surface for this reaction is calculated at the same level of theory. Various possible production channels involved in the reaction of O(3P)＋CH2F are examined. The vibrational mode analysis is used to elucidate the relationship between the transition states, intermediates and the products. The extensive investigation shows that the reaction mechanism is reliable.
All species involved in the multi-channel reaction of an oxygen atom with a fluorinated methyl radical have been investigated using density functional theory (DFT). The geometries of the reactants, intermediates, transition states and products are optimized at the B3LYP/6-311＋＋G(2d, 2p) level. The potential energy surface for this reaction is calculated at the same level of theory. Various possible production channels involved in the reaction of O(3P)＋CH2F are examined. The vibrational mode analysis is used to elucidate the relationship between the transition states, intermediates and the products. The extensive investigation shows that the reaction mechanism is reliable.
2004, 20(06): 647-650
doi: 10.3866/PKU.WHXB20040619
Abstract:
ld nanoparticles were reduced by sodium from HAuCl4 citrate and then modified by PyDDP（O,O’-Dioctadecane dithiophosphate）. IR spectra indicated that PyDDP covalent bond with the surface of the ld nanoparticle. TEM results showed that nanoparticles modified by PyDDP had a similar size with that of the original nanoparticles. At the same time it had been found that the surface plasma resonance (SPR) absorbance of the PyDDP-modified ld nanoparticles had a large red shift. Furthermore, the Jellium model was used to analyze the characteristics of SPR；the dipole model and the IR spectrum were used to form a new dipole model. It can be used to explain the mechanism of the red shift.
ld nanoparticles were reduced by sodium from HAuCl4 citrate and then modified by PyDDP（O,O’-Dioctadecane dithiophosphate）. IR spectra indicated that PyDDP covalent bond with the surface of the ld nanoparticle. TEM results showed that nanoparticles modified by PyDDP had a similar size with that of the original nanoparticles. At the same time it had been found that the surface plasma resonance (SPR) absorbance of the PyDDP-modified ld nanoparticles had a large red shift. Furthermore, the Jellium model was used to analyze the characteristics of SPR；the dipole model and the IR spectrum were used to form a new dipole model. It can be used to explain the mechanism of the red shift.
2004, 20(06): 651-655
doi: 10.3866/PKU.WHXB20040620
Abstract:
Polystyrene microspheres with carboxyl of 210 nm were prepared by emulsifier-free polymerization, and characterized by FTIR, TEM, and dynamics light scattering. The results indicate that the PS microspheres modified by methacrylic acid were monodisperse and highly charged. PS colloidal crystal was fabricated quickly from aqueous colloidal solutions by the vertical deposition method at proper temperature and humidity, and its photonic band gap was at 590 nm. The stacking of PS colloid crystal between (111) planes was determined by electron microscopy (TEM and SEM), and the results indicate that the sample of PS colloid crystal is face-centered-cubic (fcc) structure.
Polystyrene microspheres with carboxyl of 210 nm were prepared by emulsifier-free polymerization, and characterized by FTIR, TEM, and dynamics light scattering. The results indicate that the PS microspheres modified by methacrylic acid were monodisperse and highly charged. PS colloidal crystal was fabricated quickly from aqueous colloidal solutions by the vertical deposition method at proper temperature and humidity, and its photonic band gap was at 590 nm. The stacking of PS colloid crystal between (111) planes was determined by electron microscopy (TEM and SEM), and the results indicate that the sample of PS colloid crystal is face-centered-cubic (fcc) structure.
2004, 20(06): 656-658
doi: 10.3866/PKU.WHXB20040621
Abstract:
The oxidation of sulfite is an important process in flue gas desulfurization by ammonia method. In this experiment, gas discharge was introduced to oxidize higher concentration of sodium sulfite under different voltages and frequencies. The results indicated that gas discharge could enhance the oxidation with rather low power consumption. By using power of DC superimposed AC, oxidation rate rose with increase of voltage but had nothing to do with frequencies in this experiment.
The oxidation of sulfite is an important process in flue gas desulfurization by ammonia method. In this experiment, gas discharge was introduced to oxidize higher concentration of sodium sulfite under different voltages and frequencies. The results indicated that gas discharge could enhance the oxidation with rather low power consumption. By using power of DC superimposed AC, oxidation rate rose with increase of voltage but had nothing to do with frequencies in this experiment.
2004, 20(06): 659-663
doi: 10.3866/PKU.WHXB20040622
Abstract:
The atmospheric corrosion of A3 steel with Na2SO4、(NH4)2SO4、NH4Cl and NaCl deposited on it has been investigated at 298 K with relative humidity of (85±5)％. The results show: that A3 steel deposited by the salts corroded more and more seriously as the corrosion time went on and metal loss obeys the equation of Δm/A =K•tb. FTIR, SEM and XRD were utilized to study the development and characterization of corrosion products, and the results indicate that A3 steel with the salts deposited corroded much faster than the blank samples, and the corrosion of A3 steel initialed along the deposition area of the salts.
The atmospheric corrosion of A3 steel with Na2SO4、(NH4)2SO4、NH4Cl and NaCl deposited on it has been investigated at 298 K with relative humidity of (85±5)％. The results show: that A3 steel deposited by the salts corroded more and more seriously as the corrosion time went on and metal loss obeys the equation of Δm/A =K•tb. FTIR, SEM and XRD were utilized to study the development and characterization of corrosion products, and the results indicate that A3 steel with the salts deposited corroded much faster than the blank samples, and the corrosion of A3 steel initialed along the deposition area of the salts.
2004, 20(06): 664-667
doi: 10.3866/PKU.WHXB20040623
Abstract:
The effect of thiourea(TU) on the corrosion behavior of bulk nanocrystallized and coarse grain industrial pure iron in 1 mol•L－1 HCl at room temperature was investigated, by means of electrochemical impedance spectroscopy(EIS).Bulk nanocrystallized industrial pure iron is less prone to get corrosive than its coarse grain counterpart in blank 1 mol•L－1 HCl at room temperature from the EIS fitting results. On the basis of the variation of impedance behaviors of bulk nanocrystallized and coarse grain industrial pure iron in the inhibitor-containing 1 mol•L－1 HCl solutions with the immersion time, an relationship between immersion time and Nyquist plot was established, for very short immersion time,namely,5 min, an inductive loop appeared at different concentrations in the Nyquist plots of coarse industrial pure iron rod, but it did not appear in those of nanocrystallized industrial pure iron. A critical concentration of thiourea with the largest Rct (charge transfer resistance) in the complex impedance plane appeared for both samples.
The effect of thiourea(TU) on the corrosion behavior of bulk nanocrystallized and coarse grain industrial pure iron in 1 mol•L－1 HCl at room temperature was investigated, by means of electrochemical impedance spectroscopy(EIS).Bulk nanocrystallized industrial pure iron is less prone to get corrosive than its coarse grain counterpart in blank 1 mol•L－1 HCl at room temperature from the EIS fitting results. On the basis of the variation of impedance behaviors of bulk nanocrystallized and coarse grain industrial pure iron in the inhibitor-containing 1 mol•L－1 HCl solutions with the immersion time, an relationship between immersion time and Nyquist plot was established, for very short immersion time,namely,5 min, an inductive loop appeared at different concentrations in the Nyquist plots of coarse industrial pure iron rod, but it did not appear in those of nanocrystallized industrial pure iron. A critical concentration of thiourea with the largest Rct (charge transfer resistance) in the complex impedance plane appeared for both samples.
2004, 20(06): 668-672
doi: 10.3866/PKU.WHXB20040624
Abstract:
The lattice density functional theory (LDFT) was modified for monoatomic molecule adsorption systems in slits, and the revised mean field approximation and Gibbs-Helmholtz equation were introduced into the construction of Helmholtz function. Results of the revised model show a satisfactory consistence with that by Monte Carlo (MC) simulation, whereas the original LDFT data show a large deviation from it. It indicates that the mean field approximation will bring obvious system errors in the original LDFT. Multilevel adsorption occurs in slits, and different density profiles exist at a specific equilibrium concentration. This kind of multilevel adsorption is also clearly shown on the Gibbs isotherm. By comparison of results between the revised and the original LDFT, it is found that both of them can predict the multilevel adsorption behaviors, but there are still large differences between them.
The lattice density functional theory (LDFT) was modified for monoatomic molecule adsorption systems in slits, and the revised mean field approximation and Gibbs-Helmholtz equation were introduced into the construction of Helmholtz function. Results of the revised model show a satisfactory consistence with that by Monte Carlo (MC) simulation, whereas the original LDFT data show a large deviation from it. It indicates that the mean field approximation will bring obvious system errors in the original LDFT. Multilevel adsorption occurs in slits, and different density profiles exist at a specific equilibrium concentration. This kind of multilevel adsorption is also clearly shown on the Gibbs isotherm. By comparison of results between the revised and the original LDFT, it is found that both of them can predict the multilevel adsorption behaviors, but there are still large differences between them.
