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2003 Volume 19 Issue 5
2003, 19(05): 385-388
doi: 10.3866/PKU.WHXB20030501
Abstract:
A polyclonal antibody (PcAb) prepared with piceatannol, a known inhibitor against the epidermal growth factor receptor (EGFR),was adopted as a stationary phase in the chromatographic system. Using the antibody to mimic the enzyme, several anti-EGFR inhibitors were recognized directly from a crude extract of Tibetan herb. Frontal affinity chromatography (FAC) was used here for analyzing molecular interactions between the analytes and an immobilized ligand (in this case the PcAb conjugated to Sepharose CL-4B) by calculating the extent of retardation of the elution front. By combining FAC with mass spectrometry (MS) in the current study, a very efficient and straightforward procedure was developed for analyzing the binding properties of different inhibitors. The novel effective screening of anti-EGFR inhibitors using PcAb from natural resources affords us a new feasible approach for the discovery of lead compounds.
A polyclonal antibody (PcAb) prepared with piceatannol, a known inhibitor against the epidermal growth factor receptor (EGFR),was adopted as a stationary phase in the chromatographic system. Using the antibody to mimic the enzyme, several anti-EGFR inhibitors were recognized directly from a crude extract of Tibetan herb. Frontal affinity chromatography (FAC) was used here for analyzing molecular interactions between the analytes and an immobilized ligand (in this case the PcAb conjugated to Sepharose CL-4B) by calculating the extent of retardation of the elution front. By combining FAC with mass spectrometry (MS) in the current study, a very efficient and straightforward procedure was developed for analyzing the binding properties of different inhibitors. The novel effective screening of anti-EGFR inhibitors using PcAb from natural resources affords us a new feasible approach for the discovery of lead compounds.
2003, 19(05): 389-392
doi: 10.3866/PKU.WHXB20030502
Abstract:
The gas-phase elimination of 2-bromopropionic acid was investigated using density functional theory (DFT) method. Molecular structures were calculated at the B3LYP/6-31G** level. The results obtained show that the gas-phase elimination of 2-bromopropionic acid proceeds via a semi-polar five-membered cyclic transition state, where the acidic H of the group COOH assisted the leaving Br atom, and the carboxylic oxygen stabilized this transition state. The single-point energies of all optimized molecular structures by B3LYP/6-31G** were counted at B3LYP/6-311＋＋G (3df,3pd) level. The activation energy(Ea1=ETS1－ERe)of the rate-controlling step obtained at B3LYP/6-311＋＋G (3df,3pd) level was 189.5 kJ•mol－1,which is closely correlated with the available experimental data(180.3±3.4) kJ•mol－1.The relative error is 5.08％.
The gas-phase elimination of 2-bromopropionic acid was investigated using density functional theory (DFT) method. Molecular structures were calculated at the B3LYP/6-31G** level. The results obtained show that the gas-phase elimination of 2-bromopropionic acid proceeds via a semi-polar five-membered cyclic transition state, where the acidic H of the group COOH assisted the leaving Br atom, and the carboxylic oxygen stabilized this transition state. The single-point energies of all optimized molecular structures by B3LYP/6-31G** were counted at B3LYP/6-311＋＋G (3df,3pd) level. The activation energy(Ea1=ETS1－ERe)of the rate-controlling step obtained at B3LYP/6-311＋＋G (3df,3pd) level was 189.5 kJ•mol－1,which is closely correlated with the available experimental data(180.3±3.4) kJ•mol－1.The relative error is 5.08％.
2003, 19(05): 393-397
doi: 10.3866/PKU.WHXB20030503
Abstract:
The difference in adsorption for CO on the M(100) (M= Cu, Ag, Au, Pd, Pt) surfaces has been systematically investigated by first-principle density functional theory. The results indicate that the chemisorption of CO on these transition metal surfaces belongs to non-dissociative adsorption. The increased theoretical CO bond length of 0.1154～0.1161 nm (compared to 0.1128 nm in the gas phase) demonstrates the activation of the CO bond. We have carried out binding energy analysis, a natural bond orbital analysis and Mülliken population analysis of CO/M(100) adsorption systems. It can be concluded from the analyzed results that the adsorbability of CO decreases in the order of Pd(100),Pt(100),Cu(100),Ag(100) and Au(100).We have also discussed the implications of these results in terms of the catalysis of the water gas shift (WGS) reaction. From the volcano-shaped relationship between metal turnover number at 300 ℃ and binding energy of carbon monooxide and the electron transfer number of d orbital, it can be found that copper may be the optimum reactivity component of the catalyst in corresponding to the WGS reaction. Our calculations agree well with the experimental values and may explain the reason why copper is more activitive than other metals in a qualitative view.
The difference in adsorption for CO on the M(100) (M= Cu, Ag, Au, Pd, Pt) surfaces has been systematically investigated by first-principle density functional theory. The results indicate that the chemisorption of CO on these transition metal surfaces belongs to non-dissociative adsorption. The increased theoretical CO bond length of 0.1154～0.1161 nm (compared to 0.1128 nm in the gas phase) demonstrates the activation of the CO bond. We have carried out binding energy analysis, a natural bond orbital analysis and Mülliken population analysis of CO/M(100) adsorption systems. It can be concluded from the analyzed results that the adsorbability of CO decreases in the order of Pd(100),Pt(100),Cu(100),Ag(100) and Au(100).We have also discussed the implications of these results in terms of the catalysis of the water gas shift (WGS) reaction. From the volcano-shaped relationship between metal turnover number at 300 ℃ and binding energy of carbon monooxide and the electron transfer number of d orbital, it can be found that copper may be the optimum reactivity component of the catalyst in corresponding to the WGS reaction. Our calculations agree well with the experimental values and may explain the reason why copper is more activitive than other metals in a qualitative view.
2003, 19(05): 398-402
doi: 10.3866/PKU.WHXB20030504
Abstract:
Tb-doped SiO2-B2O3-NaF glass was prepared by sol-gel process,using tetraethoxy silcane, boric acid and sodium fluoride as precursors,0.10 mol•L－1 TbCl3 solution as the dopant. The luminescent properties of Tb3＋ doped SiO2-B2O3-NaF phosphors were investigated. The phosphors showed prominent luminescence in green, due to the electronic transition of 5D4—7F5 (Tb3＋).For all Tb3＋ concentrations used the emission spectrum was essentially the same with the exception of intensity and weak peak belonging to transition from 5D3 was detected in lower Tb3＋ doped samples and lower annealing temperature samples. The intensity of emission from 5D3 quenches with increasing of the Tb3＋ concentration and annealing temperature. The observation showed that cross-relaxation obviously took place in the transition 5D3－5D47F6—7F0 and/or 5D3—7F07F6—5D4.The excitation spectra of Tb3＋ emission in SiO2-B2O3-NaF glass consist of broad bands with a maximum at about 230 nm, corresponding to 4f 8—4f 75d 1 transition of Tb3＋ ion, and a series of sharp lines in the range of 300 to 380 nm which belong to transitions between the energy levels of the 4f 8 configuration. The structural characterization of these luminescent materials were carried by using XRD and TEM. The results showed that the phosphor was in amorphous phase.
Tb-doped SiO2-B2O3-NaF glass was prepared by sol-gel process,using tetraethoxy silcane, boric acid and sodium fluoride as precursors,0.10 mol•L－1 TbCl3 solution as the dopant. The luminescent properties of Tb3＋ doped SiO2-B2O3-NaF phosphors were investigated. The phosphors showed prominent luminescence in green, due to the electronic transition of 5D4—7F5 (Tb3＋).For all Tb3＋ concentrations used the emission spectrum was essentially the same with the exception of intensity and weak peak belonging to transition from 5D3 was detected in lower Tb3＋ doped samples and lower annealing temperature samples. The intensity of emission from 5D3 quenches with increasing of the Tb3＋ concentration and annealing temperature. The observation showed that cross-relaxation obviously took place in the transition 5D3－5D47F6—7F0 and/or 5D3—7F07F6—5D4.The excitation spectra of Tb3＋ emission in SiO2-B2O3-NaF glass consist of broad bands with a maximum at about 230 nm, corresponding to 4f 8—4f 75d 1 transition of Tb3＋ ion, and a series of sharp lines in the range of 300 to 380 nm which belong to transitions between the energy levels of the 4f 8 configuration. The structural characterization of these luminescent materials were carried by using XRD and TEM. The results showed that the phosphor was in amorphous phase.
2003, 19(05): 403-407
doi: 10.3866/PKU.WHXB20030505
Abstract:
The spontaneous passivation of 316# stainless steel in simulated cooling water is studied by electrochemical impedance spectroscopy, and a suitable model is chosen through fitting. It is shown that the film resistance R2 increases while the value of Y02 , which reflects the film capacitance decreases continuously in the course of immersion of the electrode, but R2 decreases sharply with addition of sulfide. The Mott-Schottky plots show that the donor and accepter densities of the passive films on stainless steel immersed in simulated cooling water for 65 days have the values of 1.47×1020 cm－3 and 2.20×1020 cm－3, respectively, but the values increase to 4.52×1020 cm－3 and 7.02×1020 cm－3 after the addition of 9 mg•L－1 sulfide for 1 h. The polarization curves indicate that the passive current rises in the presence of sulfide.
The spontaneous passivation of 316# stainless steel in simulated cooling water is studied by electrochemical impedance spectroscopy, and a suitable model is chosen through fitting. It is shown that the film resistance R2 increases while the value of Y02 , which reflects the film capacitance decreases continuously in the course of immersion of the electrode, but R2 decreases sharply with addition of sulfide. The Mott-Schottky plots show that the donor and accepter densities of the passive films on stainless steel immersed in simulated cooling water for 65 days have the values of 1.47×1020 cm－3 and 2.20×1020 cm－3, respectively, but the values increase to 4.52×1020 cm－3 and 7.02×1020 cm－3 after the addition of 9 mg•L－1 sulfide for 1 h. The polarization curves indicate that the passive current rises in the presence of sulfide.
2003, 19(05): 408-413
doi: 10.3866/PKU.WHXB20030506
Abstract:
The optimized geometries, infrared spectra, electron structure and bonding behavior of the isomers and transition states of 2-amino-5-mercapto-1,3,4-thiadiazole are studied by density functional theory(DFT) and second-order Müller-Plesset perturbation theory at B3LYP/6-311G(d, p)and MP2/6-31G(d) levels. The mechanisms of interconversion of 2-amino-5-mercapto-1,3,4- thiadiazole(AMT) isomers are studied, and a mechanism of cyclic interconversion of AMT isomers abcda is proposed. The atom charges, bond order and hybrids orbitals of the AMT isomers are discussed using the natural bond orbital (NBO) analysis.
The optimized geometries, infrared spectra, electron structure and bonding behavior of the isomers and transition states of 2-amino-5-mercapto-1,3,4-thiadiazole are studied by density functional theory(DFT) and second-order Müller-Plesset perturbation theory at B3LYP/6-311G(d, p)and MP2/6-31G(d) levels. The mechanisms of interconversion of 2-amino-5-mercapto-1,3,4- thiadiazole(AMT) isomers are studied, and a mechanism of cyclic interconversion of AMT isomers abcda is proposed. The atom charges, bond order and hybrids orbitals of the AMT isomers are discussed using the natural bond orbital (NBO) analysis.
2003, 19(05): 414-418
doi: 10.3866/PKU.WHXB20030507
Abstract:
The adsorption of O2 on the perfect and lowcoordinated sites of M (001) surface has been studied with the finite cluster models embedded in a large array of point charges by density functional method. The point charge value was determined by self－consistence technique. Different kinds of possible models of O2 adsorbed on M (001) surface were calculated. The optimization of the geometry, calculation of the adsorption energy, vibrational frequency and analysis of the Mülliken population to those adsorption models were carried out. The results indicate that cationic site in the lowest coordinated corner is the most advantageous position for O2 adsorbed on M (001) surface. The O－O bond strength is considerably weakened when O2 lies flatly on the Mg atom at the corner(Mg3c). The calculated adsorption energy of O2 on M (001) perfect surface is in od agreement with experimental value. For O2 adsorbed on the perfect surface embedded in nominal ±2.0 e point charges and on perfect surface using the bare cluster, the adsorption energies given in this paper show that they have a large deviation from the experimental value. The vibrational frequency of adsorbed O2, which is experimentally difficult to measure due to the existence of isotope exchange, was also calculated.
The adsorption of O2 on the perfect and lowcoordinated sites of M (001) surface has been studied with the finite cluster models embedded in a large array of point charges by density functional method. The point charge value was determined by self－consistence technique. Different kinds of possible models of O2 adsorbed on M (001) surface were calculated. The optimization of the geometry, calculation of the adsorption energy, vibrational frequency and analysis of the Mülliken population to those adsorption models were carried out. The results indicate that cationic site in the lowest coordinated corner is the most advantageous position for O2 adsorbed on M (001) surface. The O－O bond strength is considerably weakened when O2 lies flatly on the Mg atom at the corner(Mg3c). The calculated adsorption energy of O2 on M (001) perfect surface is in od agreement with experimental value. For O2 adsorbed on the perfect surface embedded in nominal ±2.0 e point charges and on perfect surface using the bare cluster, the adsorption energies given in this paper show that they have a large deviation from the experimental value. The vibrational frequency of adsorbed O2, which is experimentally difficult to measure due to the existence of isotope exchange, was also calculated.
2003, 19(05): 419-422
doi: 10.3866/PKU.WHXB20030508
Abstract:
The corrosion inhibition property of 2-mercapto-N-methy-imidazole(MMI) for copper in 5％HCl was studied using weight-loss method. The influences of temperature and the concentration of MMI on the corrosion inhibition efficiency were determined, from which the adsorption isotherm was obtained. The heat of adsorption and the effect of the addition of MMI on the activation energy of the corrosion were calculated. The corrosion inhibition mechanism of MMI for copper was proposed. The results indicated that the corrosion inhibition efficiency of MMI for copper increased very sharply with the rise of the concentration of MMI when the concentration was between 3 mmol•L－1 and 8 mmol•L－1 and was approximately constant when the concentration was higher than 8 mmol•L－1, while the addition of MMI accelerated the corrosion of copper if the concentration is lower than 3 mmol•L－1. The interaction force between the adsorbed MMI molecules displayed attractive one on the whole when the concentration was in the range of 4.5 mmol•L－1 to 8 mmol•L－1. The adsorption of MMI on copper surface was a heat-absorbing reaction, and the addition of MMI reduced the activation energy of the corrosion of copper.
The corrosion inhibition property of 2-mercapto-N-methy-imidazole(MMI) for copper in 5％HCl was studied using weight-loss method. The influences of temperature and the concentration of MMI on the corrosion inhibition efficiency were determined, from which the adsorption isotherm was obtained. The heat of adsorption and the effect of the addition of MMI on the activation energy of the corrosion were calculated. The corrosion inhibition mechanism of MMI for copper was proposed. The results indicated that the corrosion inhibition efficiency of MMI for copper increased very sharply with the rise of the concentration of MMI when the concentration was between 3 mmol•L－1 and 8 mmol•L－1 and was approximately constant when the concentration was higher than 8 mmol•L－1, while the addition of MMI accelerated the corrosion of copper if the concentration is lower than 3 mmol•L－1. The interaction force between the adsorbed MMI molecules displayed attractive one on the whole when the concentration was in the range of 4.5 mmol•L－1 to 8 mmol•L－1. The adsorption of MMI on copper surface was a heat-absorbing reaction, and the addition of MMI reduced the activation energy of the corrosion of copper.
2003, 19(05): 423-427
doi: 10.3866/PKU.WHXB20030509
Abstract:
Various Mn-modified CuFeZrO2 catalysts for higher alcohols synthesis were characterized and tested by TPR, DRIFT, CO hydrogenation and reactive chemisorption of N2O.It was found that suitable addition of Mn could improve the catalytic activity and C2＋ alcohols selectivity and suppress the formation of methane. TPR results showed that the reduction of CuO in CuMnFeZrO2 catalyst became more difficult because of the interaction between Cu and Mn. And such interaction proceeded stronger with the amount of Mn increased. This fact is correlated with the change of Cu surface areas and dispersion. In situ DRIFT displayed CO adsorption on the CuMnFeZrO2 catalysts. It was also shown that the interaction between Cu and Mn had occurred, the CO adsorption on the catalysts was increased and blue shifted.
Various Mn-modified CuFeZrO2 catalysts for higher alcohols synthesis were characterized and tested by TPR, DRIFT, CO hydrogenation and reactive chemisorption of N2O.It was found that suitable addition of Mn could improve the catalytic activity and C2＋ alcohols selectivity and suppress the formation of methane. TPR results showed that the reduction of CuO in CuMnFeZrO2 catalyst became more difficult because of the interaction between Cu and Mn. And such interaction proceeded stronger with the amount of Mn increased. This fact is correlated with the change of Cu surface areas and dispersion. In situ DRIFT displayed CO adsorption on the CuMnFeZrO2 catalysts. It was also shown that the interaction between Cu and Mn had occurred, the CO adsorption on the catalysts was increased and blue shifted.
2003, 19(05): 428-431
doi: 10.3866/PKU.WHXB20030510
Abstract:
A purification procedure using microporous membrane and oxidation in air for single-walled carbon nanotubes (SWCNTs) prepared by arc-discharge was discussed which eliminated coexisting metal nanoparticles, carbon nanoparticles and other impurities. The characterization of SWCNTs was carried out at different steps of the purification by TGA, HRTEM and Raman spectra. Experiments show that the method we used is effective to purify the SWCNTs produced by arc-discharge, SWCNTs with the purity of more than 90％ could be obtained.
A purification procedure using microporous membrane and oxidation in air for single-walled carbon nanotubes (SWCNTs) prepared by arc-discharge was discussed which eliminated coexisting metal nanoparticles, carbon nanoparticles and other impurities. The characterization of SWCNTs was carried out at different steps of the purification by TGA, HRTEM and Raman spectra. Experiments show that the method we used is effective to purify the SWCNTs produced by arc-discharge, SWCNTs with the purity of more than 90％ could be obtained.
2003, 19(05): 432-435
doi: 10.3866/PKU.WHXB20030511
Abstract:
Ab initio optimizations at HF/6-31G* level and subsequent electrostatic potential calculations have been performed for a group of 121 solvent molecules. High-level correlation of solubilities of fullerence (C60) in organic solvents with the theoretical descriptors of solvents have been obtained. The results also demonstrate that the solubilities of fullerence (C60) can be predicted better with the selective parameters, and the results obtained by neural network are superior to that by multiple regression.
Ab initio optimizations at HF/6-31G* level and subsequent electrostatic potential calculations have been performed for a group of 121 solvent molecules. High-level correlation of solubilities of fullerence (C60) in organic solvents with the theoretical descriptors of solvents have been obtained. The results also demonstrate that the solubilities of fullerence (C60) can be predicted better with the selective parameters, and the results obtained by neural network are superior to that by multiple regression.
2003, 19(05): 436-440
doi: 10.3866/PKU.WHXB20030512
Abstract:
Transition metal nanoclusters of Fe、Co、Ni and Cu have been obtained by Zn reduction in metal-ammonium sulfate solutions. The products were characterized by XRD, SEM, TEM and ED methods. Meantime, the reduction processes have especially been investigated. Experiments indicated that the nanoclusters were observed as solid solutions of displacement by zinc in varying extent. Fe displaced solid solution formed on the surface of zinc particles, however, Ni and Co nanoclusters formed as saturated solid solution with diameter about 7.5 nm and 12.1 nm, respectively. New phase of Cu5Zn8 was observed on the surface of Cu particles. The mechanism of the mentioned processes were discussed and considered as an influence by the driving force of EMF occurred from M-Zn oxidation-reduction cell.
Transition metal nanoclusters of Fe、Co、Ni and Cu have been obtained by Zn reduction in metal-ammonium sulfate solutions. The products were characterized by XRD, SEM, TEM and ED methods. Meantime, the reduction processes have especially been investigated. Experiments indicated that the nanoclusters were observed as solid solutions of displacement by zinc in varying extent. Fe displaced solid solution formed on the surface of zinc particles, however, Ni and Co nanoclusters formed as saturated solid solution with diameter about 7.5 nm and 12.1 nm, respectively. New phase of Cu5Zn8 was observed on the surface of Cu particles. The mechanism of the mentioned processes were discussed and considered as an influence by the driving force of EMF occurred from M-Zn oxidation-reduction cell.
2003, 19(05): 441-444
doi: 10.3866/PKU.WHXB20030513
Abstract:
Agglomerates of Pt nanoparticles were synthesized by using H2 as reduction reagent and nafion as stabilizer. The electrode of agglomerates of Pt nanoparticles was prepared by dispersing the agglomerates onto glassy carbon surface and is denoted as Ptnag/GC.The average size of the agglomerates in colloid and on the surface of electrode were characterized to be around 400 nm using TEM and SEM, respectively. Cyclic voltammetry and in situ FTIR spectroscopy were employed to study electrocatalytic properties of the Ptnag/GC electrode towards methanol oxidation. It has been revealed that the agglomerates of Pt nanoparticles exhibit significant electrocatalytic activity for the oxidation of CH3OH.In comparison with CH3OH oxidation on an electrode of Pt thin film supported on Au, the oxidation potential has been shifted negatively about 300 mV on the Ptnag/GC. The results demonstrated also that the oxidation of CH3OH is a complex process, which may be influenced by the diffusion of CH3OH and controlled by the oxidation-reduction of the agglomerates of Pt nanoparticles on electrode surface. Linearly adsorbed CO species (COL) is the only intermediate that has been determined by in situ FTIR spectroscopy. The IR features of COL illustrated that the agglomerates of Pt nanoparticles exhibit abnormal infrared effects as other kind low-dimensional nanomaterial does.
Agglomerates of Pt nanoparticles were synthesized by using H2 as reduction reagent and nafion as stabilizer. The electrode of agglomerates of Pt nanoparticles was prepared by dispersing the agglomerates onto glassy carbon surface and is denoted as Ptnag/GC.The average size of the agglomerates in colloid and on the surface of electrode were characterized to be around 400 nm using TEM and SEM, respectively. Cyclic voltammetry and in situ FTIR spectroscopy were employed to study electrocatalytic properties of the Ptnag/GC electrode towards methanol oxidation. It has been revealed that the agglomerates of Pt nanoparticles exhibit significant electrocatalytic activity for the oxidation of CH3OH.In comparison with CH3OH oxidation on an electrode of Pt thin film supported on Au, the oxidation potential has been shifted negatively about 300 mV on the Ptnag/GC. The results demonstrated also that the oxidation of CH3OH is a complex process, which may be influenced by the diffusion of CH3OH and controlled by the oxidation-reduction of the agglomerates of Pt nanoparticles on electrode surface. Linearly adsorbed CO species (COL) is the only intermediate that has been determined by in situ FTIR spectroscopy. The IR features of COL illustrated that the agglomerates of Pt nanoparticles exhibit abnormal infrared effects as other kind low-dimensional nanomaterial does.
2003, 19(05): 445-449
doi: 10.3866/PKU.WHXB20030514
Abstract:
The crystalline complex of holmium chloride with alanine, [Ho2(Ala)4(H2O)8]Cl6,was synthesized. Heat capacities of [Ho2(Ala)4(H2O)8]Cl6 were measured by adiabatic calorimetry over the temperature range from 78 to 363 K. A solid-solid phase transition was found between 214 K and 255 K with the peak temperature of 235.09 K. The enthalpy and entropy of the transition were determined to be 3.017 kJ•mol－1 and 12.83 J•K－1•mol－1,respectively.The molar heat capacities were presented by a fitted polynomial as a function of reduced temperature. The thermodynamic functions relative to the reference temperature 298.15 K were calculated based on the heat capacity data. Thermal stability of the complex was studied by thermogravimetry (TG) and differential scanning calorimetry (DSC) over the temperature range from 40 to 800 ℃.From the DTG curves, two peaks were observed in the process of the thermal decompositions for the complex. The first mass-loss peak started from 80 ℃ and ended at 179 ℃,and the second mass-loss peak started from 242 ℃ and ended at 479 ℃.A possible mechanism of the thermal decomposition was presented.
The crystalline complex of holmium chloride with alanine, [Ho2(Ala)4(H2O)8]Cl6,was synthesized. Heat capacities of [Ho2(Ala)4(H2O)8]Cl6 were measured by adiabatic calorimetry over the temperature range from 78 to 363 K. A solid-solid phase transition was found between 214 K and 255 K with the peak temperature of 235.09 K. The enthalpy and entropy of the transition were determined to be 3.017 kJ•mol－1 and 12.83 J•K－1•mol－1,respectively.The molar heat capacities were presented by a fitted polynomial as a function of reduced temperature. The thermodynamic functions relative to the reference temperature 298.15 K were calculated based on the heat capacity data. Thermal stability of the complex was studied by thermogravimetry (TG) and differential scanning calorimetry (DSC) over the temperature range from 40 to 800 ℃.From the DTG curves, two peaks were observed in the process of the thermal decompositions for the complex. The first mass-loss peak started from 80 ℃ and ended at 179 ℃,and the second mass-loss peak started from 242 ℃ and ended at 479 ℃.A possible mechanism of the thermal decomposition was presented.
2003, 19(05): 450-454
doi: 10.3866/PKU.WHXB20030515
Abstract:
Nickel catalysts with SiO2 as the support were prepared by impregnation (IM) and sol-gel-supercritical fluid drying (Sol-Gel-SCFD) methods. The catalyst were tested with hydrogenation of maleic anhydride (MA) and characterized by XRD, TPR and IR techniques. The preparation methods and nickel content determine the catalysts final structure, activity and selectivity. The NiO forms and interaction with SiO2 are important factors affecting the activity and selectivity. For catalyst prepared by Sol-Gel-SCFD method, the NiO form is related to the Ni content, and the hydrogenation products of MA are succinic anhydride (SA) and γ-butyrolactone (γ-BL).But for catalyst prepared by IM method, the form of NiO is independent on the Ni content, and the MA hydrogenation product is SA only.
Nickel catalysts with SiO2 as the support were prepared by impregnation (IM) and sol-gel-supercritical fluid drying (Sol-Gel-SCFD) methods. The catalyst were tested with hydrogenation of maleic anhydride (MA) and characterized by XRD, TPR and IR techniques. The preparation methods and nickel content determine the catalysts final structure, activity and selectivity. The NiO forms and interaction with SiO2 are important factors affecting the activity and selectivity. For catalyst prepared by Sol-Gel-SCFD method, the NiO form is related to the Ni content, and the hydrogenation products of MA are succinic anhydride (SA) and γ-butyrolactone (γ-BL).But for catalyst prepared by IM method, the form of NiO is independent on the Ni content, and the MA hydrogenation product is SA only.
2003, 19(05): 455-459
doi: 10.3866/PKU.WHXB20030516
Abstract:
The dilational viscoelasticity properties of decane-water interface containing two demulsifiers with straight chain (SP169, octadecanol polyoxypropylene-polyoxyethylene ether) and branch chain (AE121, tetraethylenehexamine polyoxypropylene-polyoxyethylene ether) respectively were investigated by interfacial tension relaxation method. The dependence of dilational modulus on dilational frequency was expounded. Our results show that when the dilational frequency is lower, the dilational modulus of the two demulsifiers approaches zero; the dilational modulus of the two demulsifiers increases when the dilational frequency becomes higher in the range of medial frequency; and when the dilational frequency is much higher, the dilational modulus of the two demulsifiers reaches to a limiting dilational viscoelasticity. It is also shown that dilational modulus of the two demulsifiers approaches a maximum value near the critical micelle concentration. Along with the increase of demulsifier concentration, the number of relaxation processes gradually increases and the contribution of them also changes regularly.
The dilational viscoelasticity properties of decane-water interface containing two demulsifiers with straight chain (SP169, octadecanol polyoxypropylene-polyoxyethylene ether) and branch chain (AE121, tetraethylenehexamine polyoxypropylene-polyoxyethylene ether) respectively were investigated by interfacial tension relaxation method. The dependence of dilational modulus on dilational frequency was expounded. Our results show that when the dilational frequency is lower, the dilational modulus of the two demulsifiers approaches zero; the dilational modulus of the two demulsifiers increases when the dilational frequency becomes higher in the range of medial frequency; and when the dilational frequency is much higher, the dilational modulus of the two demulsifiers reaches to a limiting dilational viscoelasticity. It is also shown that dilational modulus of the two demulsifiers approaches a maximum value near the critical micelle concentration. Along with the increase of demulsifier concentration, the number of relaxation processes gradually increases and the contribution of them also changes regularly.
2003, 19(05): 460-463
doi: 10.3866/PKU.WHXB20030517
Abstract:
The geometries of fifteen [99Tcm(NO)Cl(PL)2]＋ complexes were optimized by semi-empirical quantum mechanics method——ZINDO/1 and many physical and chemical descriptors were obtained. Four equations were obtained by the multiple regressions between these drescriptors and heart intial uptake. New uptake mechanism of redox mechanism was revealed when analyzing these equations.
The geometries of fifteen [99Tcm(NO)Cl(PL)2]＋ complexes were optimized by semi-empirical quantum mechanics method——ZINDO/1 and many physical and chemical descriptors were obtained. Four equations were obtained by the multiple regressions between these drescriptors and heart intial uptake. New uptake mechanism of redox mechanism was revealed when analyzing these equations.
2003, 19(05): 464-468
doi: 10.3866/PKU.WHXB20030518
Abstract:
In the present paper, in-situ preparation of spherical silver nanoparticles(10～30 nm),triangular and hexangular single silver crystal(200～2000 nm) have been conducted in linear chitosan films by photochemical reduction. The spherical silver nanoparticles(5～8 nm) have also been obtained electrochemically in the film. The chitosan/Ag complex has been characterized by means of TEM, SEM, IR spectra and XRD, the preliminary analysis and discussion about the causes of changing of silver crystal structure from multi crystal to single crystal in photochemical reduction process have been carried out.
In the present paper, in-situ preparation of spherical silver nanoparticles(10～30 nm),triangular and hexangular single silver crystal(200～2000 nm) have been conducted in linear chitosan films by photochemical reduction. The spherical silver nanoparticles(5～8 nm) have also been obtained electrochemically in the film. The chitosan/Ag complex has been characterized by means of TEM, SEM, IR spectra and XRD, the preliminary analysis and discussion about the causes of changing of silver crystal structure from multi crystal to single crystal in photochemical reduction process have been carried out.
2003, 19(05): 469-473
doi: 10.3866/PKU.WHXB20030519
Abstract:
The photoionization of benzene seeded in He, N2, Ar gases by an intense 25 ns Nd-YAG 532 nm laser has been studied by time-of-flight mass spectrometry. At the laser intensity about 1010～1011 W•cm－2, strong multi-charged ions Cq+(q=1～3) appeared in the mass spectra when Ar was used as carrier gas. From the peak splitting, the most probable kinetic energies of C2＋ and C3＋ are calculated to be 12.9 eV and 37.5 eV, respectively. From the experimental results of changing the He, N2, Ar carrier gases, their pressure and the laser intensity, we can draw the conclusion that those multi-charge ions come from the Coulomb explosion of benzene cluster ions.
The photoionization of benzene seeded in He, N2, Ar gases by an intense 25 ns Nd-YAG 532 nm laser has been studied by time-of-flight mass spectrometry. At the laser intensity about 1010～1011 W•cm－2, strong multi-charged ions Cq+(q=1～3) appeared in the mass spectra when Ar was used as carrier gas. From the peak splitting, the most probable kinetic energies of C2＋ and C3＋ are calculated to be 12.9 eV and 37.5 eV, respectively. From the experimental results of changing the He, N2, Ar carrier gases, their pressure and the laser intensity, we can draw the conclusion that those multi-charge ions come from the Coulomb explosion of benzene cluster ions.
2003, 19(05): 474-477
doi: 10.3866/PKU.WHXB20030520
Abstract:
The multilayer films of horseradish peroxidase(HRP) were fabricated by layer-by-layer assembly of HRP and poly(sodium-p-styrenesulfonate)(PSS) on PET(polyethylene glycol terephthalate) and ld electrode surface. The activity of the assembly films was investigated. The surface topography was characterized by atomic force microscope (AFM). The relationship between the activity of the immobilized HRP with the surface roughness and topography was also studies. Cyclic voltammetry (CV) was used for the study of electrochemical properties of the films. The enzyme electrode of mltilayer films was sensitive for the reduction of hydrogen peroxide in the methylene blue (MB) solution. The response current is linear with the concentration of H2O2 in the concentration range of 0.2～5.0 mmol•L－1.
The multilayer films of horseradish peroxidase(HRP) were fabricated by layer-by-layer assembly of HRP and poly(sodium-p-styrenesulfonate)(PSS) on PET(polyethylene glycol terephthalate) and ld electrode surface. The activity of the assembly films was investigated. The surface topography was characterized by atomic force microscope (AFM). The relationship between the activity of the immobilized HRP with the surface roughness and topography was also studies. Cyclic voltammetry (CV) was used for the study of electrochemical properties of the films. The enzyme electrode of mltilayer films was sensitive for the reduction of hydrogen peroxide in the methylene blue (MB) solution. The response current is linear with the concentration of H2O2 in the concentration range of 0.2～5.0 mmol•L－1.
2003, 19(05): 478-480
doi: 10.3866/PKU.WHXB20030521
Abstract:
Highly oriented ZnO submicrorod arrays have been prepared on SnO2 conducting glass substrates which were modified with densely packed ZnO crystal nucleus. The growth procedure of ZnO submicrorod arrays consists of two steps:(1) modification of SnO2 conducting glass substrates with dispersed ZnO crystal nucleus by immersing the substrates into concentrated solution, and (2) hydrothermal growth of ZnO submicrorods in aqueous solution. Scanning electron microscope (SEM), selected area electron diffraction (SAED) and X-ray diffraction(XRD) have been employed to investigate the ZnO submicrorod arrays.SEM images indicate that ZnO hexa nal submicrorod arrays grow nearly perpendicularly to the substrates. The diameter and the length of ZnO submicrorod are about 400～500 nm and 2 μm for 2 h growth time, respectively. Result of SAED reveals that the ZnO submicrorod arrays are single-crystalline hexa nal rods. XRD shows that the ZnO submicrorods are wurtzite. The significantly higher intensity obtained from the (002) diffraction peak indicates that the submicrorods are preferentially oriented in the c-axis direction (grown along the[001] crystallographic face direction).
Highly oriented ZnO submicrorod arrays have been prepared on SnO2 conducting glass substrates which were modified with densely packed ZnO crystal nucleus. The growth procedure of ZnO submicrorod arrays consists of two steps:(1) modification of SnO2 conducting glass substrates with dispersed ZnO crystal nucleus by immersing the substrates into concentrated solution, and (2) hydrothermal growth of ZnO submicrorods in aqueous solution. Scanning electron microscope (SEM), selected area electron diffraction (SAED) and X-ray diffraction(XRD) have been employed to investigate the ZnO submicrorod arrays.SEM images indicate that ZnO hexa nal submicrorod arrays grow nearly perpendicularly to the substrates. The diameter and the length of ZnO submicrorod are about 400～500 nm and 2 μm for 2 h growth time, respectively. Result of SAED reveals that the ZnO submicrorod arrays are single-crystalline hexa nal rods. XRD shows that the ZnO submicrorods are wurtzite. The significantly higher intensity obtained from the (002) diffraction peak indicates that the submicrorods are preferentially oriented in the c-axis direction (grown along the[001] crystallographic face direction).
