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2003 Volume 19 Issue 6
2003, 19(06): 481-486
doi: 10.3866/PKU.WHXB20030601
Abstract:
Absolute rate constant for the reaction of CCl2 radical with H2O is obtained as (5.45±0.95)×10－14 cm3•molecule－1•s－1 by LPLIF technique. The CCl2 is first produced by 213 nm laser photolysis of CCl4. The mechanism for the reaction CCl2＋H2O has been studied using a highlevel ab initio G2MP2 method. It is found that there are two reaction mechanisms: insertion and additionelimination. The three primary product channels, HCl＋HClCO， HCl＋transClCOH and HCl＋cisClCOH, are studied in detail. Moreover, the branch ratios are calculated using RRKMTST and convention transition state theories. The calculations show that at lower temperatures the major product channel is HCl＋HCClO via the insretion of C atom of CCl2 into OH bond of H2O, whereas the formation of HCl＋transClCOH dominates at higher temperatures.
Absolute rate constant for the reaction of CCl2 radical with H2O is obtained as (5.45±0.95)×10－14 cm3•molecule－1•s－1 by LPLIF technique. The CCl2 is first produced by 213 nm laser photolysis of CCl4. The mechanism for the reaction CCl2＋H2O has been studied using a highlevel ab initio G2MP2 method. It is found that there are two reaction mechanisms: insertion and additionelimination. The three primary product channels, HCl＋HClCO， HCl＋transClCOH and HCl＋cisClCOH, are studied in detail. Moreover, the branch ratios are calculated using RRKMTST and convention transition state theories. The calculations show that at lower temperatures the major product channel is HCl＋HCClO via the insretion of C atom of CCl2 into OH bond of H2O, whereas the formation of HCl＋transClCOH dominates at higher temperatures.
2003, 19(06): 487-491
doi: 10.3866/PKU.WHXB20030602
Abstract:
Nanosized NaY zeolite with crystal size below 100 nm was synthesized by microwave heating method under reflux.Crystallization rate for adding citric acid is close to that of adding rare earth ions(Ln3＋),and furthermore,synthetic NaY zeolites both possess close crystal size about 40 nm and SiO2/Al2O3 ratio(5.2),with which is smaller insize and higher in ratio than that of no adding synthesis under the same condition.Compared to crystal size of NaY zeolite synthesized by conventional heating with the same composition,crystal size synthesized by microwave heating is reduced and that crystallization time is shortened remarkably,which fully testify that the microwave heating possesses rapid and uniform as well as reducing crystal size characters.
Nanosized NaY zeolite with crystal size below 100 nm was synthesized by microwave heating method under reflux.Crystallization rate for adding citric acid is close to that of adding rare earth ions(Ln3＋),and furthermore,synthetic NaY zeolites both possess close crystal size about 40 nm and SiO2/Al2O3 ratio(5.2),with which is smaller insize and higher in ratio than that of no adding synthesis under the same condition.Compared to crystal size of NaY zeolite synthesized by conventional heating with the same composition,crystal size synthesized by microwave heating is reduced and that crystallization time is shortened remarkably,which fully testify that the microwave heating possesses rapid and uniform as well as reducing crystal size characters.
2003, 19(06): 492-497
doi: 10.3866/PKU.WHXB20030603
Abstract:
Role of Ce on the catalytic performance of Ce-Ag-Mo-P-O catalyst in selective oxidation of propane to acrolein was investigated.In order to establish the relationship between the catalytic performance and properties,the properties of Ag0.3Mo0.5P0.3Ox and Ce-doped Ag0.3Mo0.5P0.3Ox catalysts have been comparatively characterized by BET,XRD,H2-TPR,O2-TPD,C3H8-TPD and EPR.The addition of Ce to Ag0.3Mo0.5P0.3Ox catalyst distinctly improved the conversion of propane and the selectivity of acrolein.Ce0.1 Ag0.3Mo0.5P0.3Oy catalyst exhibited the highest selectivity and yield of acrolein in this reaction.The activation energy of propane oxidation was lower on the Ce0.1 Ag0.3Mo0.5P0.3Oy than on the Ag0.3Mo0.5P0.3Ox catalyst.Propene was a possible intermediate for the formation of acrolein in selective oxidation of propane on these catalysts.The proper addition of Ce enhanced the conversion of intermediate propene to acrolein.On the other hand,the addition of Ce improved the reducibility and Mo5＋/Mo6＋ ratio,furthermore,it caused a stronger adsorption of propane on the catalysts.The addition of Ce to the catalysts modified the properties by the formation of redox cycle “Ce3＋＋Mo6＋Ce4＋＋Mo5＋” in the catalysts.Such modification determined the catalytic performance of the catalysts in selective oxidation of propane to acrolein.
Role of Ce on the catalytic performance of Ce-Ag-Mo-P-O catalyst in selective oxidation of propane to acrolein was investigated.In order to establish the relationship between the catalytic performance and properties,the properties of Ag0.3Mo0.5P0.3Ox and Ce-doped Ag0.3Mo0.5P0.3Ox catalysts have been comparatively characterized by BET,XRD,H2-TPR,O2-TPD,C3H8-TPD and EPR.The addition of Ce to Ag0.3Mo0.5P0.3Ox catalyst distinctly improved the conversion of propane and the selectivity of acrolein.Ce0.1 Ag0.3Mo0.5P0.3Oy catalyst exhibited the highest selectivity and yield of acrolein in this reaction.The activation energy of propane oxidation was lower on the Ce0.1 Ag0.3Mo0.5P0.3Oy than on the Ag0.3Mo0.5P0.3Ox catalyst.Propene was a possible intermediate for the formation of acrolein in selective oxidation of propane on these catalysts.The proper addition of Ce enhanced the conversion of intermediate propene to acrolein.On the other hand,the addition of Ce improved the reducibility and Mo5＋/Mo6＋ ratio,furthermore,it caused a stronger adsorption of propane on the catalysts.The addition of Ce to the catalysts modified the properties by the formation of redox cycle “Ce3＋＋Mo6＋Ce4＋＋Mo5＋” in the catalysts.Such modification determined the catalytic performance of the catalysts in selective oxidation of propane to acrolein.
2003, 19(06): 498-503
doi: 10.3866/PKU.WHXB20030604
Abstract:
A series of SnxZr1-xO2 solid solution catalysts with SnO2 content varied from 10％(w) to 90％(w) were prepared by co-current coprecipitation method (CCP method) using ammonia solution as precipitating agent and calcined at 500 ℃ for 4 h in air.The structure variation with SnO2 content was investigated by XRD,electron diffraction,FT-Raman and FT-IR.Tin dioxide and zirconia can react with each other to form solid solutions within a large composition range.In the present work,zirconia prepared by CCP method and calcined at 500 ℃ was monoclinic,and tin dioxide prepared by the same way possessed rutile structure.The experiment results showed the following dependence of the solid solution structure on SnO2 content.First,less than 20％ SnO2 inserted into the lattice of ZrO2 could stabilize the tetra nal structure of zirconia and form the zirconia-rich solid solutions.Then,amorphous zirconia-rich solid solutions were formed in the SnO2 content region from 30 ％ to 50％.Furthermore,a rutile structure tin dioxide-rich solid solution existed as SnO2 content over 60％.Finally,the zirconia-rich solid solution and tin dioxide-rich solid solution could co-exist while the SnO2 content maintained at 55％,which exhibited a structure transition between zirconia-rich and tin dioxide-rich solid solutions.Because the Sn－O bond was weakened and the effective electropositivity of Sn4＋ was decreased as Zr4＋ inserted into SnO2 lattice as proved by FT-Raman and FT-IR measurements,both the activation and the complete combustion of propene were restrained by Zr4＋,as a result,the catalytic performance for NO selective reduction was promoted.
A series of SnxZr1-xO2 solid solution catalysts with SnO2 content varied from 10％(w) to 90％(w) were prepared by co-current coprecipitation method (CCP method) using ammonia solution as precipitating agent and calcined at 500 ℃ for 4 h in air.The structure variation with SnO2 content was investigated by XRD,electron diffraction,FT-Raman and FT-IR.Tin dioxide and zirconia can react with each other to form solid solutions within a large composition range.In the present work,zirconia prepared by CCP method and calcined at 500 ℃ was monoclinic,and tin dioxide prepared by the same way possessed rutile structure.The experiment results showed the following dependence of the solid solution structure on SnO2 content.First,less than 20％ SnO2 inserted into the lattice of ZrO2 could stabilize the tetra nal structure of zirconia and form the zirconia-rich solid solutions.Then,amorphous zirconia-rich solid solutions were formed in the SnO2 content region from 30 ％ to 50％.Furthermore,a rutile structure tin dioxide-rich solid solution existed as SnO2 content over 60％.Finally,the zirconia-rich solid solution and tin dioxide-rich solid solution could co-exist while the SnO2 content maintained at 55％,which exhibited a structure transition between zirconia-rich and tin dioxide-rich solid solutions.Because the Sn－O bond was weakened and the effective electropositivity of Sn4＋ was decreased as Zr4＋ inserted into SnO2 lattice as proved by FT-Raman and FT-IR measurements,both the activation and the complete combustion of propene were restrained by Zr4＋,as a result,the catalytic performance for NO selective reduction was promoted.
2003, 19(06): 504-508
doi: 10.3866/PKU.WHXB20030605
Abstract:
Monolithic silica aerogels have been prepared from cheap silica sols using nonsupercritical drying by controlling the gelation process and drying conditions. The external appearances of the resulting aerogels are quite in accordance with those prepared by conventional supercritical drying. The microstructures of aerogels，which consist of well primary nanoparticles and pore distribution， are excellent. The compositions and pH of the solutions effectually influence the gelation process and the densities of resulting aerogels, and the variation of the particle diameters of aerogels with pH of the solutions in gelation process is obvious. On the basis of the variations of preparation conditions， the densities of aerogels are in the range of 200～400 kg•m－3， and the specific surface areas can vary from 250 m2•g－1 to 300 m2•g－1, while their average pore sizes are 11～20 nm with porosity of about 91％.
Monolithic silica aerogels have been prepared from cheap silica sols using nonsupercritical drying by controlling the gelation process and drying conditions. The external appearances of the resulting aerogels are quite in accordance with those prepared by conventional supercritical drying. The microstructures of aerogels，which consist of well primary nanoparticles and pore distribution， are excellent. The compositions and pH of the solutions effectually influence the gelation process and the densities of resulting aerogels, and the variation of the particle diameters of aerogels with pH of the solutions in gelation process is obvious. On the basis of the variations of preparation conditions， the densities of aerogels are in the range of 200～400 kg•m－3， and the specific surface areas can vary from 250 m2•g－1 to 300 m2•g－1, while their average pore sizes are 11～20 nm with porosity of about 91％.
2003, 19(06): 509-513
doi: 10.3866/PKU.WHXB20030606
Abstract:
Ruthenium oxide-carbon nanotubes composites with different loadings of RuO2 on carbon nanotubes have been synthesized.In order to design nanotube-based ruthenium oxide coated supercapacitor electrodes with large surface area,a new sol-gel process for the preparation of ultrafine RuO2 particles was developed.The composite electrodes consisting of carbon nanotube and RuO2•xH2O were developed by the deposition of RuO2 on the surface of carbon nanotube.Maximum capacitance was observed after heat treatment at 250 ℃ for all the composites.Supercapacitors based on the composite electrodes show much higher specific capacitance than those based on pure carbon nanotube ones.A specific capacitance of 570 F•g－1 can be achieved when the weight percent of RuO2•xH2O in the composite electrodes reaches 100％.In addition,supercapacitors based on the composite electrodes show both high energy density and high power density characteristics.
Ruthenium oxide-carbon nanotubes composites with different loadings of RuO2 on carbon nanotubes have been synthesized.In order to design nanotube-based ruthenium oxide coated supercapacitor electrodes with large surface area,a new sol-gel process for the preparation of ultrafine RuO2 particles was developed.The composite electrodes consisting of carbon nanotube and RuO2•xH2O were developed by the deposition of RuO2 on the surface of carbon nanotube.Maximum capacitance was observed after heat treatment at 250 ℃ for all the composites.Supercapacitors based on the composite electrodes show much higher specific capacitance than those based on pure carbon nanotube ones.A specific capacitance of 570 F•g－1 can be achieved when the weight percent of RuO2•xH2O in the composite electrodes reaches 100％.In addition,supercapacitors based on the composite electrodes show both high energy density and high power density characteristics.
2003, 19(06): 514-518
doi: 10.3866/PKU.WHXB20030607
Abstract:
Chitosan(CS)/CdS nanocomposite films have been prepared via in situ generation of CdS nanoparticles. The factors affecting the hydrothermal stability and the fluorescence properties of the films have been studied. Furthermore, the sensing properties of the nanocomposite films to pyridine in water have been systematically investigated. SEM observation showed that the sizes of the CdS particles are around 70 nm, and the particles are evenly doped within the CS films. The positions of the fluorescence emission of the nanocomposite films indicate that the sizes of the real fluorescing CdS particles are less than 20 nm, suggesting that the CdS particles observed via SEM may be aggregates of small CdS particles, and the small particles may be separated by the organics. It has been found that the fluorescence emission of the nanocomposite films is very sensitive to the presence of pyridine, and microamount of pyridine makes the emission increase dramatically. The emission is hardly affected by common ions in water, except copper and iodide ions. It is predicted that the films may be developed into an excellent sensing films for pyridine in water.
Chitosan(CS)/CdS nanocomposite films have been prepared via in situ generation of CdS nanoparticles. The factors affecting the hydrothermal stability and the fluorescence properties of the films have been studied. Furthermore, the sensing properties of the nanocomposite films to pyridine in water have been systematically investigated. SEM observation showed that the sizes of the CdS particles are around 70 nm, and the particles are evenly doped within the CS films. The positions of the fluorescence emission of the nanocomposite films indicate that the sizes of the real fluorescing CdS particles are less than 20 nm, suggesting that the CdS particles observed via SEM may be aggregates of small CdS particles, and the small particles may be separated by the organics. It has been found that the fluorescence emission of the nanocomposite films is very sensitive to the presence of pyridine, and microamount of pyridine makes the emission increase dramatically. The emission is hardly affected by common ions in water, except copper and iodide ions. It is predicted that the films may be developed into an excellent sensing films for pyridine in water.
2003, 19(06): 519-522
doi: 10.3866/PKU.WHXB20030608
Abstract:
The local structures of monolayer dispersive CuO/γ-Al2O3 catalysts prepared by means of impregnation have been investigated by XAFS technique.For the CuO/γ-Al2O3 sample with CuO loading 0.4 mmol/100 m2 lower than the monolayer dispersion threshold,the XAFS results indicate that only the first coordination shell appears in the radial distribution function of Cu atoms,and that the RCu－O and coordination number in the first shell are 0.195 nm and 4,respectively.Hence,we consider that the CuO active species on the surface of γ-Al2O3 are in the form of isolated atomic cluster ().Small amount of CuO nano-grains is formed onto the surface of γ-Al2O3 while the CuO loading is just equal to the threshold 0.8 mmol/100 m2.For sample with CuO loading of 1.2 mmol/100 m2,the local structure of Cu atom in CuO/γ-Al2O3 is similar to that of CuO powder.On the basis of the XAFS results,a monolayer dispersion model of CuO/γ-Al2O3 catalysts has been proposed.
The local structures of monolayer dispersive CuO/γ-Al2O3 catalysts prepared by means of impregnation have been investigated by XAFS technique.For the CuO/γ-Al2O3 sample with CuO loading 0.4 mmol/100 m2 lower than the monolayer dispersion threshold,the XAFS results indicate that only the first coordination shell appears in the radial distribution function of Cu atoms,and that the RCu－O and coordination number in the first shell are 0.195 nm and 4,respectively.Hence,we consider that the CuO active species on the surface of γ-Al2O3 are in the form of isolated atomic cluster ().Small amount of CuO nano-grains is formed onto the surface of γ-Al2O3 while the CuO loading is just equal to the threshold 0.8 mmol/100 m2.For sample with CuO loading of 1.2 mmol/100 m2,the local structure of Cu atom in CuO/γ-Al2O3 is similar to that of CuO powder.On the basis of the XAFS results,a monolayer dispersion model of CuO/γ-Al2O3 catalysts has been proposed.
2003, 19(06): 523-527
doi: 10.3866/PKU.WHXB20030609
Abstract:
This paper reported the dielectric properties of the reverse osmosis membrane UTC-70 in NaCl and KCl aqueous solution of different concentrations,studied by dielectric relaxation theory of bilamellar structure.The membrane/aqueous systems had an interfacial polarization behavior that their conductance and capacity displayed a sudden increasing and decreasing in the frequency range of 103～104 Hz.The dielectric parameters of the systems were obtained by nonlinear curve fitting.The relaxation intensity and the characteristic relaxation frequency increasd with the electrolyte concentration supporting the theory of the interfacial polarization.Furthermore,the dielectric characteristics of the systems was analyzed and the phase parameters including the dielectric constant and the conductivity of the membrane were obtained.It was found that the reverse osmosis membrane UTC-70 had a very low density of permanent negative charges.In electrolytes of low concentration the membrane behaved like an ion-exchange membrane.The conductivity ratio of the membrane phase to the aqueous phase first decreased and then approched to a constant as the electrolyte concentration increasesd.This is attributed to the Donnan effect of the permanent charges in the membrane.
This paper reported the dielectric properties of the reverse osmosis membrane UTC-70 in NaCl and KCl aqueous solution of different concentrations,studied by dielectric relaxation theory of bilamellar structure.The membrane/aqueous systems had an interfacial polarization behavior that their conductance and capacity displayed a sudden increasing and decreasing in the frequency range of 103～104 Hz.The dielectric parameters of the systems were obtained by nonlinear curve fitting.The relaxation intensity and the characteristic relaxation frequency increasd with the electrolyte concentration supporting the theory of the interfacial polarization.Furthermore,the dielectric characteristics of the systems was analyzed and the phase parameters including the dielectric constant and the conductivity of the membrane were obtained.It was found that the reverse osmosis membrane UTC-70 had a very low density of permanent negative charges.In electrolytes of low concentration the membrane behaved like an ion-exchange membrane.The conductivity ratio of the membrane phase to the aqueous phase first decreased and then approched to a constant as the electrolyte concentration increasesd.This is attributed to the Donnan effect of the permanent charges in the membrane.
2003, 19(06): 528-532
doi: 10.3866/PKU.WHXB20030610
Abstract:
The poly(ophenylenediamine) molecularly imprinting nanometer layer with high sensitivity to phosphorus agent sarin has been prepared by electropolymerization. Quartz crystal microbalance verifies the existence of molecularly imprinting. Cyclovoltammetry，atomic force microscope and Xray photoelectron spectroscopy have been used to characterize these films. The results show that the layer thickness is only 20 nm，and the film surface is hollowprotruding， lax and has many holes. XPS further certifies that molecularly imprinting mostly influence the threedimension arrangement of polymers， but the chemical composition of polymers does not change. The poly(ophenylenediamine) molecularly imprinting nanometer layers have wide application foreground on the selective detection to the nerve agent sarin.
The poly(ophenylenediamine) molecularly imprinting nanometer layer with high sensitivity to phosphorus agent sarin has been prepared by electropolymerization. Quartz crystal microbalance verifies the existence of molecularly imprinting. Cyclovoltammetry，atomic force microscope and Xray photoelectron spectroscopy have been used to characterize these films. The results show that the layer thickness is only 20 nm，and the film surface is hollowprotruding， lax and has many holes. XPS further certifies that molecularly imprinting mostly influence the threedimension arrangement of polymers， but the chemical composition of polymers does not change. The poly(ophenylenediamine) molecularly imprinting nanometer layers have wide application foreground on the selective detection to the nerve agent sarin.
2003, 19(06): 533-537
doi: 10.3866/PKU.WHXB20030611
Abstract:
This paper reports the preparation and properties of biosenor using conducting composite material consisted of ethyl cellulose and acetylene black. The final biosensor was constructed by applying a mixture containing 0.010 g ethyl cellulose, 0.004 g acetylene black，a little paraffin wax and 0.2 mg glucose oxidase (23000 units/g solid, E.C.1.1.3.4, Sigma Chemical Co.) on a platinum electrode (3 mm×3 mm). Effect of various factors on the response current of the biosensor was discussed. The response current increases linearly with increasing glucose concentration under 11.5 mmol•dm－3. Its activation energy is 40.3 kJ•mol－1 in enzymecatalyzed reaction. AFM shows that the surface of conducting polymer composite materialglucose oxidase electrode′s presents uniform granular structure after paraffin wax being washed with cyclohexane, which is favorable for enzymecatalyzed reaction.
This paper reports the preparation and properties of biosenor using conducting composite material consisted of ethyl cellulose and acetylene black. The final biosensor was constructed by applying a mixture containing 0.010 g ethyl cellulose, 0.004 g acetylene black，a little paraffin wax and 0.2 mg glucose oxidase (23000 units/g solid, E.C.1.1.3.4, Sigma Chemical Co.) on a platinum electrode (3 mm×3 mm). Effect of various factors on the response current of the biosensor was discussed. The response current increases linearly with increasing glucose concentration under 11.5 mmol•dm－3. Its activation energy is 40.3 kJ•mol－1 in enzymecatalyzed reaction. AFM shows that the surface of conducting polymer composite materialglucose oxidase electrode′s presents uniform granular structure after paraffin wax being washed with cyclohexane, which is favorable for enzymecatalyzed reaction.
2003, 19(06): 538-542
doi: 10.3866/PKU.WHXB20030612
Abstract:
The pore size distribution(PSD) is the major characteristics of the heterogeneity for the mesoporous materials.Together with statistics integral equation,two methods,grand canonical Monte Carlo(GCMC)method and density functional theory(DFT),are used to study the PSD of mesoporous materials.In order to compare the two methods,the PSD of activated meso-carbon microbeads( a-MCMBs) is calculated based on the nitrogen adsorption isotherm at 77 K.In GCMC simulation and DFT calculation,the nitrogen is modeled as a Lennord-Jones (LJ)spherical molecule.The well-known steele's 10-4-3 potential is used to represent the interaction between the fluid molecule and the solid wall.The weighted density approximation of Tarazona's theory is used to get the free energy.The PSDs for the mesoporous material predicted by the two methods are in od line for larger pore sizes(larger than 1.125 nm),while for small pore sizes,DFT deviates significantly due to inherent approximations.
The pore size distribution(PSD) is the major characteristics of the heterogeneity for the mesoporous materials.Together with statistics integral equation,two methods,grand canonical Monte Carlo(GCMC)method and density functional theory(DFT),are used to study the PSD of mesoporous materials.In order to compare the two methods,the PSD of activated meso-carbon microbeads( a-MCMBs) is calculated based on the nitrogen adsorption isotherm at 77 K.In GCMC simulation and DFT calculation,the nitrogen is modeled as a Lennord-Jones (LJ)spherical molecule.The well-known steele's 10-4-3 potential is used to represent the interaction between the fluid molecule and the solid wall.The weighted density approximation of Tarazona's theory is used to get the free energy.The PSDs for the mesoporous material predicted by the two methods are in od line for larger pore sizes(larger than 1.125 nm),while for small pore sizes,DFT deviates significantly due to inherent approximations.
2003, 19(06): 543-548
doi: 10.3866/PKU.WHXB20030613
Abstract:
The concept of twobody perturbation potential was introduced in this paper, and a new theoretical method was offered for the analytic potential of threeatom interaction,which is constructed by perturbation potential of twobody. Using this method, the analytic potential function of H2O, which is a nonlinear threeatom interaction system, was obtained. The potential correctly described the character of pathways in the O（1D）＋H2→H2O→OH＋H reaction. The theoretical results are in well agreement with the experimental results. This method is easily extended to construct the analytic potential of fouratom interaction system.
The concept of twobody perturbation potential was introduced in this paper, and a new theoretical method was offered for the analytic potential of threeatom interaction,which is constructed by perturbation potential of twobody. Using this method, the analytic potential function of H2O, which is a nonlinear threeatom interaction system, was obtained. The potential correctly described the character of pathways in the O（1D）＋H2→H2O→OH＋H reaction. The theoretical results are in well agreement with the experimental results. This method is easily extended to construct the analytic potential of fouratom interaction system.
2003, 19(06): 549-552
doi: 10.3866/PKU.WHXB20030614
Abstract:
The phenolato-bridged CuⅡ-CoⅡ heterobinuclear complex ,CuCo(TS)（H2O） has been studied with density functional theory(DFT) calculations at ROB3LYP/SDD//ROB3LYP/LanL2MB level ,the equilibrium geometries in singlet and triplet configurations of the complex were optimized and the harmonic vibrational frequencies were calculated .The results show that the triplet electronic configuration of the complex is more stable than the singlet one.The spin populations of electrons are predominantly located on the Co(6) atom and its neighbours,no population is found on the Cu(1) atom.There is a strong effect of spin delocalization in the complex.The frontier orbits are mainly composed of d-like orbits of Co(6)atom and p-like orbits of the ligand.The frontier orbits of this constitution favors the electron transfer between Co(6)atom and the ligand.These results are in od agreement with the results obtained from experiment.
The phenolato-bridged CuⅡ-CoⅡ heterobinuclear complex ,CuCo(TS)（H2O） has been studied with density functional theory(DFT) calculations at ROB3LYP/SDD//ROB3LYP/LanL2MB level ,the equilibrium geometries in singlet and triplet configurations of the complex were optimized and the harmonic vibrational frequencies were calculated .The results show that the triplet electronic configuration of the complex is more stable than the singlet one.The spin populations of electrons are predominantly located on the Co(6) atom and its neighbours,no population is found on the Cu(1) atom.There is a strong effect of spin delocalization in the complex.The frontier orbits are mainly composed of d-like orbits of Co(6)atom and p-like orbits of the ligand.The frontier orbits of this constitution favors the electron transfer between Co(6)atom and the ligand.These results are in od agreement with the results obtained from experiment.
2003, 19(06): 553-556
doi: 10.3866/PKU.WHXB20030615
Abstract:
Geometrical optimization and theoretical calculation of the vibrational spectra of pxylene（pC8H10）and its cation were performed using the 631G basis sets of the Gaussian98 program. The primary peaks of spectra of the first excited state are verified and the results are in od agreement with the experimental values. The peaks of spectra of ionic state are assigned using ab initio calculation, and the vibrational mode on 341 cm－1 is 3.
Geometrical optimization and theoretical calculation of the vibrational spectra of pxylene（pC8H10）and its cation were performed using the 631G basis sets of the Gaussian98 program. The primary peaks of spectra of the first excited state are verified and the results are in od agreement with the experimental values. The peaks of spectra of ionic state are assigned using ab initio calculation, and the vibrational mode on 341 cm－1 is 3.
2003, 19(06): 557-559
doi: 10.3866/PKU.WHXB20030616
Abstract:
The effects of n-hexanol on the micellization of quaternary ammonium dimeric surfactants (C12-s-C12•2Br,s=3,4,6) have been examined using conductivity and steady fluorescence measurements.The results showed that the critical micelle concentration cmc decreases with the addition of n-hexanol.The larger s,the stronger the effect.The dimeric surfactant and n-hexanol form the mixed micelles with the alkyl chains of n-hexanol molecules penetrating into the micelle interior and with hydroxyl groups lie in the palisade layer of the micelle.At the same concentration of n-hexanol in aqueous solution,the molar fraction of n-hexanol in the mixed micelle is almost the same for different s.The ionization degree of the mixed micelle increases with increasing n-hexanol concentration.
The effects of n-hexanol on the micellization of quaternary ammonium dimeric surfactants (C12-s-C12•2Br,s=3,4,6) have been examined using conductivity and steady fluorescence measurements.The results showed that the critical micelle concentration cmc decreases with the addition of n-hexanol.The larger s,the stronger the effect.The dimeric surfactant and n-hexanol form the mixed micelles with the alkyl chains of n-hexanol molecules penetrating into the micelle interior and with hydroxyl groups lie in the palisade layer of the micelle.At the same concentration of n-hexanol in aqueous solution,the molar fraction of n-hexanol in the mixed micelle is almost the same for different s.The ionization degree of the mixed micelle increases with increasing n-hexanol concentration.
2003, 19(06): 560-563
doi: 10.3866/PKU.WHXB20030617
Abstract:
Using 2277 bioactivity monitoring system,we determined the changes of heat effect of inhibition of Clarithromycin with Pr(NO3)3 or La(NO3)3 on Escherichia coli growth at 37 ℃.According to the thermokinetic model,the relationship between the concentration of antibiotics (c) and growth rate constant (k) and its half inhibitory concentration,Ic50,were analyzed quantitatively. Clarithromycin: k=0.03106－1.273×10－3c Ic50=8.81 μg•mL－1 (0.5～20 μg•mL－1) Clarithromycin＋Pr3＋: k=0.02967－1.332×10－3c Ic50=7.38 μg•mL－1 (1～15 μg•mL－1) Clarithromycin＋La3＋: k=0.02741－1.194×10－3c Ic50=6.34 μg•mL－1 (1～15 μg•mL－1) The results of microcalorimetry experiments not only indicated that antibacterial activity of Clarithromycin was stronger than that of erythromycin,but also the changeable features of thermokinetics of the bacterial cell in biological,biochemical and metabolic process under the action of different drugs.
Using 2277 bioactivity monitoring system,we determined the changes of heat effect of inhibition of Clarithromycin with Pr(NO3)3 or La(NO3)3 on Escherichia coli growth at 37 ℃.According to the thermokinetic model,the relationship between the concentration of antibiotics (c) and growth rate constant (k) and its half inhibitory concentration,Ic50,were analyzed quantitatively. Clarithromycin: k=0.03106－1.273×10－3c Ic50=8.81 μg•mL－1 (0.5～20 μg•mL－1) Clarithromycin＋Pr3＋: k=0.02967－1.332×10－3c Ic50=7.38 μg•mL－1 (1～15 μg•mL－1) Clarithromycin＋La3＋: k=0.02741－1.194×10－3c Ic50=6.34 μg•mL－1 (1～15 μg•mL－1) The results of microcalorimetry experiments not only indicated that antibacterial activity of Clarithromycin was stronger than that of erythromycin,but also the changeable features of thermokinetics of the bacterial cell in biological,biochemical and metabolic process under the action of different drugs.
2003, 19(06): 564-568
doi: 10.3866/PKU.WHXB20030618
Abstract:
In this work isopropanol(iP) oxidation was adopted as a model reaction for studying the catalytic activity of poly2,5dimethylaniline (PDMAn) and polyotoluidine (POT) membrane modified electrode. Each voltammetric curve of PDMAn and POT modified electrodes has two pair of redox peaks. In comparison with platinized Pt electrode, platinized PDMAn and POT modified electrodes enhance iP oxidation current significantly, furthermore the oxidation current increase with potential cycling numbers, whereas the oxidation current at platinized Pt electrode decreases with potential cycling numbers. It is indicated that the functional membrane modified electrode exhibits higher catalytic activity to iP oxidation. POT modified electrode with low platinum loading shows great catalytic activity for iP oxidation, and has higher response sensitivity than PDMAn in the condition of low concentration iP. It is also found that PDMAn has degraded after preservation in air for three years, while POT has excellent environmental stability. Therefore, POT is promising to be an electrochemical sensor material with practical application prospect.
In this work isopropanol(iP) oxidation was adopted as a model reaction for studying the catalytic activity of poly2,5dimethylaniline (PDMAn) and polyotoluidine (POT) membrane modified electrode. Each voltammetric curve of PDMAn and POT modified electrodes has two pair of redox peaks. In comparison with platinized Pt electrode, platinized PDMAn and POT modified electrodes enhance iP oxidation current significantly, furthermore the oxidation current increase with potential cycling numbers, whereas the oxidation current at platinized Pt electrode decreases with potential cycling numbers. It is indicated that the functional membrane modified electrode exhibits higher catalytic activity to iP oxidation. POT modified electrode with low platinum loading shows great catalytic activity for iP oxidation, and has higher response sensitivity than PDMAn in the condition of low concentration iP. It is also found that PDMAn has degraded after preservation in air for three years, while POT has excellent environmental stability. Therefore, POT is promising to be an electrochemical sensor material with practical application prospect.
2003, 19(06): 569-572
doi: 10.3866/PKU.WHXB20030619
Abstract:
Pd/Mm(mischmetal) rare earth films were prepared by magnetron sputtering technology,the crystal structure,morphology and electrochemical behavior of the asprepared films were investigated by using XRD,AFM and electrochemical measurement techniques including cyclic voltammetry and AC impedance.The results showed that Pd coatings is a kind of island structure with 30～50 nm in size.The electrochemical reduction or oxidation of hydrogen only occurred on the Pd coatings.The electrochemical impedance spectra of Pd/Mm film electrodes was composed of two semicircles,of which the low frequency zone is corresponded to the solid diffusion process of H atom in the film,and the high one to the electrochemical reaction on the surface of the electrode.The solid diffusion process of H atom in the inner rare earth layer is the ratecontrolled step.
Pd/Mm(mischmetal) rare earth films were prepared by magnetron sputtering technology,the crystal structure,morphology and electrochemical behavior of the asprepared films were investigated by using XRD,AFM and electrochemical measurement techniques including cyclic voltammetry and AC impedance.The results showed that Pd coatings is a kind of island structure with 30～50 nm in size.The electrochemical reduction or oxidation of hydrogen only occurred on the Pd coatings.The electrochemical impedance spectra of Pd/Mm film electrodes was composed of two semicircles,of which the low frequency zone is corresponded to the solid diffusion process of H atom in the film,and the high one to the electrochemical reaction on the surface of the electrode.The solid diffusion process of H atom in the inner rare earth layer is the ratecontrolled step.
2003, 19(06): 573-576
doi: 10.3866/PKU.WHXB20030620
Abstract:
The present work deals with the effect of N(2aminoethyl)dodecanamide on the flotation behavior of aluminosilicates(including kaolinite, illite and pyrophyllite). It was found that the N(2aminoethyl)dode canamide made the recovery of pyrophyllite more than 97.7％. The collecting power of N(2aminoethyl) dodecanamide for kaolinite and illite are relatively weak, generally, the recovery does not beyond 82％. The pulp pH has less effect on the recovery of aluminosilicate. In the acidic range,the surfactants were adsorbed on mineral surface mainly by electrostatic forces, while, in the alkaline pulp, they were adsorbed mainly by way of hydrogen bond. The FTIR spectra give a proof of hydroxyl groups on the aluminosilicates surface. The Zeta potential is negative over a wide pHrange. SEM photographs(×15000) of aluminosilicate particles show that pyrophyllite particle take the shape of thin slice, but kaolinite and illite are particles with irregular appearance.
The present work deals with the effect of N(2aminoethyl)dodecanamide on the flotation behavior of aluminosilicates(including kaolinite, illite and pyrophyllite). It was found that the N(2aminoethyl)dode canamide made the recovery of pyrophyllite more than 97.7％. The collecting power of N(2aminoethyl) dodecanamide for kaolinite and illite are relatively weak, generally, the recovery does not beyond 82％. The pulp pH has less effect on the recovery of aluminosilicate. In the acidic range,the surfactants were adsorbed on mineral surface mainly by electrostatic forces, while, in the alkaline pulp, they were adsorbed mainly by way of hydrogen bond. The FTIR spectra give a proof of hydroxyl groups on the aluminosilicates surface. The Zeta potential is negative over a wide pHrange. SEM photographs(×15000) of aluminosilicate particles show that pyrophyllite particle take the shape of thin slice, but kaolinite and illite are particles with irregular appearance.
