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2007 Volume 23 Issue 11
2007, 23(11):
Abstract:
2007, 23(11): 1657-1661
doi: 10.3866/PKU.WHXB20071101
Abstract:
The surface property and aggregation behavior of an anionic surfactant, sodium dodecylsulfate (SDS), in a mixed solvent of a water-soluble room temperature ionic liquid 1-butyl-3-methyl-imidazolium tetrafluoroborate ([BMim]BF4) and water were investigated by means of surface tension measurements and nuclear magnetic resonance (NMR) spectroscopy. It was found that the critical micelle concentration (cmc) of SDS could be remarkably reduced and the surface activity of the system was enhanced by the addition of a small amount of [BMim]BF4. Moreover, the surface activity and aggregation ability of SDS aqueous solution could be promoted when the molar fraction of [BMim]BF4 in the mixed solvent (x1) was at the range of 0-0.0458. This promotion function was most efficient at x1=0.0018.
The surface property and aggregation behavior of an anionic surfactant, sodium dodecylsulfate (SDS), in a mixed solvent of a water-soluble room temperature ionic liquid 1-butyl-3-methyl-imidazolium tetrafluoroborate ([BMim]BF4) and water were investigated by means of surface tension measurements and nuclear magnetic resonance (NMR) spectroscopy. It was found that the critical micelle concentration (cmc) of SDS could be remarkably reduced and the surface activity of the system was enhanced by the addition of a small amount of [BMim]BF4. Moreover, the surface activity and aggregation ability of SDS aqueous solution could be promoted when the molar fraction of [BMim]BF4 in the mixed solvent (x1) was at the range of 0-0.0458. This promotion function was most efficient at x1=0.0018.
2007, 23(11): 1662-1666
doi: 10.1016/S1872-1508(07)60079-5
Abstract:
Carbon-doped TiO2 thin films were prepared by direct current (DC) reactive magnetron sputtering at room temperature in an Ar/O2 ambience, using a titanium target incrusted with graphite pieces. The films as prepared were characterized by X-ray diffraction (XRD), UV-Vis transmission spectra, and photoelectrochemistry methods. The XRD patterns of the films showed that the doping of carbon was beneficial to the crystallization of the films. When the ratio of area of C/Ti in the target was less than 0.10, the crystallization of the films increased with the increase in graphite area in the target. The band gap of the films decreased from 3.4 eV to 3.1 eV when the ratio of area of C/Ti in the target was 0.05. The photoelctrochemical property of the films improved when the ratio of area of C/Ti in the target was less than 0.10. When this ratio was 0.10 the photocurrent density of the film was 0.069 μA·cm-2 at 0 V under visible light illumination. However, an abnormal photoelectrochemical response was observed when the ratio of area of C/Ti in the target was 0.16.
Carbon-doped TiO2 thin films were prepared by direct current (DC) reactive magnetron sputtering at room temperature in an Ar/O2 ambience, using a titanium target incrusted with graphite pieces. The films as prepared were characterized by X-ray diffraction (XRD), UV-Vis transmission spectra, and photoelectrochemistry methods. The XRD patterns of the films showed that the doping of carbon was beneficial to the crystallization of the films. When the ratio of area of C/Ti in the target was less than 0.10, the crystallization of the films increased with the increase in graphite area in the target. The band gap of the films decreased from 3.4 eV to 3.1 eV when the ratio of area of C/Ti in the target was 0.05. The photoelctrochemical property of the films improved when the ratio of area of C/Ti in the target was less than 0.10. When this ratio was 0.10 the photocurrent density of the film was 0.069 μA·cm-2 at 0 V under visible light illumination. However, an abnormal photoelectrochemical response was observed when the ratio of area of C/Ti in the target was 0.16.
2007, 23(11): 1667-1670
doi: 10.3866/PKU.WHXB20071103
Abstract:
Monodispersed ZnO spheres were produced by strictly isolating the formation and growth of crystal nuclear, and the sphere diameters were controlled by varying the amount of the crystal nuclear. Photonic crystals (PCs) were produced from ZnO spheres by using a kind of sedimentation self-assembly process. The concentrated reaction solution was dropped onto a substrate typically at 140 ℃, and as the solvent evaporated, the particles spontaneously assembled into periodic structures. By measuring the normal-incidence transmission spectra, the photonic band gap (PBG) of our periodic structures was observed, the PCs assembled by monodisperse ZnO spheres with diameters of 220 and 250 nmcorresponded to the PBG with the center wavelengths of 460 and 540 nm, respectively.
Monodispersed ZnO spheres were produced by strictly isolating the formation and growth of crystal nuclear, and the sphere diameters were controlled by varying the amount of the crystal nuclear. Photonic crystals (PCs) were produced from ZnO spheres by using a kind of sedimentation self-assembly process. The concentrated reaction solution was dropped onto a substrate typically at 140 ℃, and as the solvent evaporated, the particles spontaneously assembled into periodic structures. By measuring the normal-incidence transmission spectra, the photonic band gap (PBG) of our periodic structures was observed, the PCs assembled by monodisperse ZnO spheres with diameters of 220 and 250 nmcorresponded to the PBG with the center wavelengths of 460 and 540 nm, respectively.
2007, 23(11): 1671-1676
doi: 10.1016/S1872-1508(07)60080-1
Abstract:
Bi2MoO6 films on ITO glass substrates were prepared from amorphous complex precursor by dip-coating technique. The relationships between conditions of preparation, structures, morphologies and photoelectrochemical properties of Bi2MoO6 films were investigated by using scanning electron microscope (SEM), X-ray diffraction (XRD), laserRamanspectroscopy (LRS), diffuse reflectance spectroscopy(DRS), photocurrent actioncurves, andincident photon-to-current conversion efficiency (IPCE). Bi2MoO6 films prepared at 500 ℃ for 1 h were γ-Bi2MoO6 phase, and Bi2MoO6 nanoparticles grew along (131) plane. The thickness of the films obtained was about 69 nm. The size of the Bi2MoO6 nanoparticles was increased with rising calcination temperature and extention of calcination time, in addition γ-Bi2MoO6 changed into β-Bi2MoO6 and γ’-Bi2MoO6 at 525 ℃. Bi2MoO6 films had visible-light response, and detectable photocurrent was generated under the visible-light (λ>400 nm) irradiation. The IPCE of the optimized Bi2MoO6 films was 2.14% at 400 nm. The photocurrent density and IPCE could be controlled by modifying the surface structure of Bi2MoO6 films, which could be achieved by changing the preparation conditions.
Bi2MoO6 films on ITO glass substrates were prepared from amorphous complex precursor by dip-coating technique. The relationships between conditions of preparation, structures, morphologies and photoelectrochemical properties of Bi2MoO6 films were investigated by using scanning electron microscope (SEM), X-ray diffraction (XRD), laserRamanspectroscopy (LRS), diffuse reflectance spectroscopy(DRS), photocurrent actioncurves, andincident photon-to-current conversion efficiency (IPCE). Bi2MoO6 films prepared at 500 ℃ for 1 h were γ-Bi2MoO6 phase, and Bi2MoO6 nanoparticles grew along (131) plane. The thickness of the films obtained was about 69 nm. The size of the Bi2MoO6 nanoparticles was increased with rising calcination temperature and extention of calcination time, in addition γ-Bi2MoO6 changed into β-Bi2MoO6 and γ’-Bi2MoO6 at 525 ℃. Bi2MoO6 films had visible-light response, and detectable photocurrent was generated under the visible-light (λ>400 nm) irradiation. The IPCE of the optimized Bi2MoO6 films was 2.14% at 400 nm. The photocurrent density and IPCE could be controlled by modifying the surface structure of Bi2MoO6 films, which could be achieved by changing the preparation conditions.
2007, 23(11): 1677-1682
doi: 10.1016/S1872-1508(07)60081-3
Abstract:
The reaction mechanism between HNO2 and C6H5Br in aqueous solution in the presence or absence of O2 was studied using laser flash photolysis transient absorption spectrum technique under irradiation at 355 nm. The experimental results suggested the generation of·OH radical through the photolysis of HNO2. The addition of·OH radical to bromobenzene to form an OH-adduct, C6H5Br…OH, involved a second-order rate constant of (8.1±0.7)×109 L·mol-1·s-1 C6H5Br…OHcould be oxidized by O2 or HNO2. The second-order rate constant (3.0±0.5)×107 L·mol-1·s-1 for the reaction of C6H5Br…OHwith HNO2was much slower than (4.0±0.6)×108 L·mol-1·s-1 for the reaction of C6H5Br…OH with O2. The decay constant of C6H5Br…OHO2 produced by the reaction of C6H5Br…OH with O2 decayed was (2.4±0.1)×104 s-1. Gas chromatography and mass spectrometric (GC-MS) analysis suggested the formation of multiple compounds containing nitryl or quinone formed by the reaction of C6H5Br…OH with HNO2 or O2.
The reaction mechanism between HNO2 and C6H5Br in aqueous solution in the presence or absence of O2 was studied using laser flash photolysis transient absorption spectrum technique under irradiation at 355 nm. The experimental results suggested the generation of·OH radical through the photolysis of HNO2. The addition of·OH radical to bromobenzene to form an OH-adduct, C6H5Br…OH, involved a second-order rate constant of (8.1±0.7)×109 L·mol-1·s-1 C6H5Br…OHcould be oxidized by O2 or HNO2. The second-order rate constant (3.0±0.5)×107 L·mol-1·s-1 for the reaction of C6H5Br…OHwith HNO2was much slower than (4.0±0.6)×108 L·mol-1·s-1 for the reaction of C6H5Br…OH with O2. The decay constant of C6H5Br…OHO2 produced by the reaction of C6H5Br…OH with O2 decayed was (2.4±0.1)×104 s-1. Gas chromatography and mass spectrometric (GC-MS) analysis suggested the formation of multiple compounds containing nitryl or quinone formed by the reaction of C6H5Br…OH with HNO2 or O2.
2007, 23(11): 1683-1690
doi: 10.1016/S1872-1508(07)60082-5
Abstract:
The molecular structure, conformational stability, and vibrational frequencies of tert-butyl N-(2-bromocyclohex-2-enyl)-N-(2-furylmethyl)carbamate (TBBFC) were investigated by utilizing the Hartree-Fock (HF) and density functional theory (DFT) ab initio calculations with 6-31G* and 6-31G** basis sets. The optimized bond length and angle values obtained by HF method showed the best agreement with the experimental values. Comparison of the observed and calculated fundamental vibrational frequencies indicated that B3LYP was superior to the scaled HF approach for molecular problems. Optimal uniform scaling factors calculated for the title compound are 0.899/0.904, 0.958/0.961, and 0.988/0.989 for HF, B3LYP, and BLYP (6-31G*/6-31G**), respectively.
The molecular structure, conformational stability, and vibrational frequencies of tert-butyl N-(2-bromocyclohex-2-enyl)-N-(2-furylmethyl)carbamate (TBBFC) were investigated by utilizing the Hartree-Fock (HF) and density functional theory (DFT) ab initio calculations with 6-31G* and 6-31G** basis sets. The optimized bond length and angle values obtained by HF method showed the best agreement with the experimental values. Comparison of the observed and calculated fundamental vibrational frequencies indicated that B3LYP was superior to the scaled HF approach for molecular problems. Optimal uniform scaling factors calculated for the title compound are 0.899/0.904, 0.958/0.961, and 0.988/0.989 for HF, B3LYP, and BLYP (6-31G*/6-31G**), respectively.
2007, 23(11): 1691-1695
doi: 10.1016/S1872-1508(07)60083-7
Abstract:
A novel CeO2-Y2O3 (denoted as CeY) washcoat adhered to the cordierite honeycomb was prepared. The preparation technique, using nano-sized CeO2 and yttrium citrate as precursors, was friendly to environment because no deleterious products were formed during the operation. The CeY washcoat support and Pd/CeY catalysts were characterized using scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray fluorescence (XRF) spectrometer, and Raman spectroscopy. The results showed that the washcoat had sufficient adhesion and high adsorption efficiency for active species and was suitable for supporting Pd catalysts. For the catalysts, most of Y2O3 entered into the channel of the cordierite honeycomb, whereas CeO2 and Pd enriched on the surface. Furthermore, model reactions for the catalytic combustion of CO, toluene, and ethyl acetate were carried out to evaluate the performance of the Pd/CeY catalyst. It exhibited fairly od catalytic activity and thermal stability. For those catalysts calcined at 500℃, the T99 (the lowest reaction temperature when the conversion is 99%) of CO, toluene, and ethyl acetate was 150, 220, and 310 ℃, respectively, whereas for those catalysts calcined at 1050 ℃, the T99 of CO, toluene, and ethyl acetate was 180, 250, and 330 ℃, respectively. Catalysts calcined at higher temperature, the crystallite size of active species (PdO) increases, which possibly results in a decline in the catalytic activity.
A novel CeO2-Y2O3 (denoted as CeY) washcoat adhered to the cordierite honeycomb was prepared. The preparation technique, using nano-sized CeO2 and yttrium citrate as precursors, was friendly to environment because no deleterious products were formed during the operation. The CeY washcoat support and Pd/CeY catalysts were characterized using scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray fluorescence (XRF) spectrometer, and Raman spectroscopy. The results showed that the washcoat had sufficient adhesion and high adsorption efficiency for active species and was suitable for supporting Pd catalysts. For the catalysts, most of Y2O3 entered into the channel of the cordierite honeycomb, whereas CeO2 and Pd enriched on the surface. Furthermore, model reactions for the catalytic combustion of CO, toluene, and ethyl acetate were carried out to evaluate the performance of the Pd/CeY catalyst. It exhibited fairly od catalytic activity and thermal stability. For those catalysts calcined at 500℃, the T99 (the lowest reaction temperature when the conversion is 99%) of CO, toluene, and ethyl acetate was 150, 220, and 310 ℃, respectively, whereas for those catalysts calcined at 1050 ℃, the T99 of CO, toluene, and ethyl acetate was 180, 250, and 330 ℃, respectively. Catalysts calcined at higher temperature, the crystallite size of active species (PdO) increases, which possibly results in a decline in the catalytic activity.
2007, 23(11): 1696-1700
doi: 10.3866/PKU.WHXB20071108
Abstract:
A series of poly(aryl ether) dendrimers with carbazole (CZ) at the periphery and with/without a crown ether at the core (CZ-Gn-CR/CZ-Gn-OH, n=1-3) were synthesized. The photophysical properties of CZ-Gn-CR and CZ-Gn-OH were investigated with different concentrations of Li+, Na+, K+, Ca2+, Cu2+, Zn2+, Eu3+, and Tb3+. There are interactions between the dendrimer and Eu3+, Tb3+, and Cu2+ in the ground state, and the crown ether structure at the core enhances the interactions. The fluorescence of the dendrimers was quenched by Eu3+, Tb3+, and Cu2+ via a static quenching process, and the quenching rate constants were calculated. Li +, Na+, K+, Ca2+, and Zn2+ have no obvious influence on the UV-absorption and fluorescence spectra of the dendrimers.
A series of poly(aryl ether) dendrimers with carbazole (CZ) at the periphery and with/without a crown ether at the core (CZ-Gn-CR/CZ-Gn-OH, n=1-3) were synthesized. The photophysical properties of CZ-Gn-CR and CZ-Gn-OH were investigated with different concentrations of Li+, Na+, K+, Ca2+, Cu2+, Zn2+, Eu3+, and Tb3+. There are interactions between the dendrimer and Eu3+, Tb3+, and Cu2+ in the ground state, and the crown ether structure at the core enhances the interactions. The fluorescence of the dendrimers was quenched by Eu3+, Tb3+, and Cu2+ via a static quenching process, and the quenching rate constants were calculated. Li +, Na+, K+, Ca2+, and Zn2+ have no obvious influence on the UV-absorption and fluorescence spectra of the dendrimers.
2007, 23(11): 1701-1706
doi: 10.3866/PKU.WHXB20071109
Abstract:
Twonewoxovanadiumcomplexes withpoly(pyrazolyl)borate and carboxylic acid as ligands,VO[phCH2CH(NH2)COO][HB(pz)3] (1) and VO(3,5-Me2pz)[HB(3,5-Me2pz)3](CH3COO) (2), were synthesized successfully. The two complexes were characterized by IR, elemental analyses, thermal analyses, and single crystal X-ray diffraction. The study of non-isothermal decomposition kinetics for complex 1 showed that the possible reaction mechanisms of the two steps were nucleation and growth with n=1/4, and chemical reaction, respectively; the kinetic equations may be expressed as dα/dT=(A/β)e-E/RT(1/4)(1-α)[-ln(1-α)]-3 and dα/dT=(A/β)e-E/RT(1-α)2, respectively, the apparent activation energies of the steps are 223.52 and 331.94 kJ·mol-1, respectively, the pre-exponentials ln(A/s-1) are 49.67 as well as 57.50. The study of non-isothermal decomposition kinetics for complex 2 showed: the possible reaction mechanisms of the two steps were chemical reaction, and nucleation and growth with n=1/2, respectively, the kinetic equations may be expressed as dα/dT=(A/β)e-E/RT(1-α)2, and dα/dT=(A/β)e-E/RT(1/2)(1-α)[-ln(1-α)]-1, respectively, the apparent activation energies of the steps were 300.56 and 444.72 kJ·mol-1, respectively, the pre-exponentials ln(A/s-1) were 75.53 as well
as 92.50.
Twonewoxovanadiumcomplexes withpoly(pyrazolyl)borate and carboxylic acid as ligands,VO[phCH2CH(NH2)COO][HB(pz)3] (1) and VO(3,5-Me2pz)[HB(3,5-Me2pz)3](CH3COO) (2), were synthesized successfully. The two complexes were characterized by IR, elemental analyses, thermal analyses, and single crystal X-ray diffraction. The study of non-isothermal decomposition kinetics for complex 1 showed that the possible reaction mechanisms of the two steps were nucleation and growth with n=1/4, and chemical reaction, respectively; the kinetic equations may be expressed as dα/dT=(A/β)e-E/RT(1/4)(1-α)[-ln(1-α)]-3 and dα/dT=(A/β)e-E/RT(1-α)2, respectively, the apparent activation energies of the steps are 223.52 and 331.94 kJ·mol-1, respectively, the pre-exponentials ln(A/s-1) are 49.67 as well as 57.50. The study of non-isothermal decomposition kinetics for complex 2 showed: the possible reaction mechanisms of the two steps were chemical reaction, and nucleation and growth with n=1/2, respectively, the kinetic equations may be expressed as dα/dT=(A/β)e-E/RT(1-α)2, and dα/dT=(A/β)e-E/RT(1/2)(1-α)[-ln(1-α)]-1, respectively, the apparent activation energies of the steps were 300.56 and 444.72 kJ·mol-1, respectively, the pre-exponentials ln(A/s-1) were 75.53 as well
as 92.50.
2007, 23(11): 1707-1713
doi: 10.1016/S1872-1508(07)60084-9
Abstract:
The floating self-assembly of submicron monodisperse polystyrene (PS) spheres and SiO2 nanoparticles at water-air interface of suspension (floating assembly method) was presented in this article. The mechanismof this method was extensively studied. It was shown that the assembly of PS microspheres was dominant in the floating assembly of binary colloidal particles. At definite phase concentration, the formation of ordered structure of PS microspheres had nothing to do with the initial volume ratio of PS microspheres and SiO2 nanoparticles in suspension. When the diameter of PS microspheres was in the range of 150-500 nm, the ordered structure could be obtained easily, otherwise it was difficult. The self-assembly of SiO2 nanoparticles was a depositing process at the surface of PS microspheres as substrate. The volume fraction of SiO2 particles in binary colloidal crystal was determined by the phase concentration of SiO2 in suspension.
The floating self-assembly of submicron monodisperse polystyrene (PS) spheres and SiO2 nanoparticles at water-air interface of suspension (floating assembly method) was presented in this article. The mechanismof this method was extensively studied. It was shown that the assembly of PS microspheres was dominant in the floating assembly of binary colloidal particles. At definite phase concentration, the formation of ordered structure of PS microspheres had nothing to do with the initial volume ratio of PS microspheres and SiO2 nanoparticles in suspension. When the diameter of PS microspheres was in the range of 150-500 nm, the ordered structure could be obtained easily, otherwise it was difficult. The self-assembly of SiO2 nanoparticles was a depositing process at the surface of PS microspheres as substrate. The volume fraction of SiO2 particles in binary colloidal crystal was determined by the phase concentration of SiO2 in suspension.
2007, 23(11): 1714-1718
doi: 10.3866/PKU.WHXB20071111
Abstract:
NMR chemical shifts of C8 adduct in the reaction of guanosine with N-acetyl-4-biphenyl nitrenium ion were studied using ab initio calculations. The results were in od agreement with experimental data. Additionally, the charges obtained by atom-bond electronegativity equalization method σπ (ABEEM σπ) also corresponded with the NMR chemical shifts. For imine adduct in the reaction of adenosine with N-acetyl-4-biphenyl nitrenium ion, theoretical NMR chemical shifts of some key C atoms were very different to the experimental values. Hence, it was predicted that the final adduct in studied reaction should include azepine adduct besides imine adduct.
NMR chemical shifts of C8 adduct in the reaction of guanosine with N-acetyl-4-biphenyl nitrenium ion were studied using ab initio calculations. The results were in od agreement with experimental data. Additionally, the charges obtained by atom-bond electronegativity equalization method σπ (ABEEM σπ) also corresponded with the NMR chemical shifts. For imine adduct in the reaction of adenosine with N-acetyl-4-biphenyl nitrenium ion, theoretical NMR chemical shifts of some key C atoms were very different to the experimental values. Hence, it was predicted that the final adduct in studied reaction should include azepine adduct besides imine adduct.
2007, 23(11): 1719-1722
doi: 10.3866/PKU.WHXB20071112
Abstract:
The electrochemical reduction of nitromethane was investigated in the room temperature ionic liquid 1-butyl-3-methylimidazoliumtetrafluoroborate (BMImBF4) on a Pt disk microelectrode. The influences of temperature and scan rate on the electrochemical characteristics of nitromethane were also investigated by using cyclic voltammetry. The results showed that the electroreduction of nitromethane in BMImBF4 was an irreversible process with one electron transferred, which was controlled by diffusion. Steady-state limiting currents for the electroreduction of nitromethane in BMImBF4 at various temperatures were obtained. The diffusion coefficient was increased with temperature due to the diminution of the BMImBF4 viscosity. In terms of Arrhenius equation, the activation energy (Ea) of diffusion of nitromethane in BMImBF4 was calculated to be 39.5 kJ·mol-1.
The electrochemical reduction of nitromethane was investigated in the room temperature ionic liquid 1-butyl-3-methylimidazoliumtetrafluoroborate (BMImBF4) on a Pt disk microelectrode. The influences of temperature and scan rate on the electrochemical characteristics of nitromethane were also investigated by using cyclic voltammetry. The results showed that the electroreduction of nitromethane in BMImBF4 was an irreversible process with one electron transferred, which was controlled by diffusion. Steady-state limiting currents for the electroreduction of nitromethane in BMImBF4 at various temperatures were obtained. The diffusion coefficient was increased with temperature due to the diminution of the BMImBF4 viscosity. In terms of Arrhenius equation, the activation energy (Ea) of diffusion of nitromethane in BMImBF4 was calculated to be 39.5 kJ·mol-1.
2007, 23(11): 1723-1727
doi: 10.3866/PKU.WHXB20071113
Abstract:
The geometric configurations, vibrational frequencies of Pdn(n=1-7) clusters and their interactions with a CH4 molecule were studied using the DFT/B3LYP method. Increasing the total number of palladium atoms made the cluster less size-dependent and structural parameters approach to the bulk solid. Methane adsorption on Pdn(n=1-7) clusters was very weak. Methane was activated by Pd2 cluseter, activation and adsorption energy were aggrandized. With increasing cluster size, the interaction of molecular-surface in PdnCH4 (n=1,3-7) clusters became weak, and the adsorption energy approached to that on the bulk metal.
The geometric configurations, vibrational frequencies of Pdn(n=1-7) clusters and their interactions with a CH4 molecule were studied using the DFT/B3LYP method. Increasing the total number of palladium atoms made the cluster less size-dependent and structural parameters approach to the bulk solid. Methane adsorption on Pdn(n=1-7) clusters was very weak. Methane was activated by Pd2 cluseter, activation and adsorption energy were aggrandized. With increasing cluster size, the interaction of molecular-surface in PdnCH4 (n=1,3-7) clusters became weak, and the adsorption energy approached to that on the bulk metal.
2007, 23(11): 1728-1732
doi: 10.3866/PKU.WHXB20071114
Abstract:
Generalized gradient approximation (GGA) of the density function theory (DFT) was applied to investigate the structure of CO chemisorption on low-index platinum surfaces. Many properties including chemisorption energy, bond lengths of C—O and C—Pt, population analysis, and density of state were calculated by CASTEP-module of Materials Studio package. It was shown that when the coverage was 0.25 ML (monolayer), the preference sites of CO chemisorption on Pt were the bridge site of Pt(100), short bridge site of Pt(110) and hcp hollowsite of Pt(111), the chemisorption energies were 2.11, 2.37 and 1.96 eV, respectively. There existed electron transfer between CO molecule and Pt atoms during the adsorption. After adsorption, C—O bond was weaken, its bond length was longer than before, the interactions of inner Pt atoms were weaken too. The population of the first layer Pt atoms on surface was reduced obviously. According to DOS analysis, some mixing of the 4σ, 1π, 5σ, 2π molecular orbitals with metal states was observed.
Generalized gradient approximation (GGA) of the density function theory (DFT) was applied to investigate the structure of CO chemisorption on low-index platinum surfaces. Many properties including chemisorption energy, bond lengths of C—O and C—Pt, population analysis, and density of state were calculated by CASTEP-module of Materials Studio package. It was shown that when the coverage was 0.25 ML (monolayer), the preference sites of CO chemisorption on Pt were the bridge site of Pt(100), short bridge site of Pt(110) and hcp hollowsite of Pt(111), the chemisorption energies were 2.11, 2.37 and 1.96 eV, respectively. There existed electron transfer between CO molecule and Pt atoms during the adsorption. After adsorption, C—O bond was weaken, its bond length was longer than before, the interactions of inner Pt atoms were weaken too. The population of the first layer Pt atoms on surface was reduced obviously. According to DOS analysis, some mixing of the 4σ, 1π, 5σ, 2π molecular orbitals with metal states was observed.
2007, 23(11): 1733-1737
doi: 10.3866/PKU.WHXB20071115
Abstract:
The vibration spectrum of quasi 1D (one dimensional) nanosize lines was calculated using the density function theory (DFT)/B3LYP method at 6-31G(d) level. The results showed that the vibration frequency and intensity of IR and Raman spectra obviously indicated even-odd oscillation with the number of SiO2 units. For different vibration modes, the even-odd oscillation was strong or weak because of the effect of the polar group’s orientation relative to silicon-oxygen two-member ring. Moreover, the analyses of the polarization indicated the effect of hydroxyl on even-odd oscillation.
The vibration spectrum of quasi 1D (one dimensional) nanosize lines was calculated using the density function theory (DFT)/B3LYP method at 6-31G(d) level. The results showed that the vibration frequency and intensity of IR and Raman spectra obviously indicated even-odd oscillation with the number of SiO2 units. For different vibration modes, the even-odd oscillation was strong or weak because of the effect of the polar group’s orientation relative to silicon-oxygen two-member ring. Moreover, the analyses of the polarization indicated the effect of hydroxyl on even-odd oscillation.
2007, 23(11): 1738-1742
doi: 10.3866/PKU.WHXB20071116
Abstract:
La-Ba co-modified alumina was prepared from two kinds of pseudo boehmite and HNO3 as peptizer by peptizing method. The structure and surface property of the alumina were characterized by XRD, BET surface area analyzer, NH3-temperature programmed desorption and NO2-temperature programmed desorption technology. XRD results showed that γ-Al2O3 phase existed in all the modified alumina samples after calcination at 1273 K. A little BaCO3 was generated when content of BaO was increased to 14%(w). BET results showed that both of 5%(w) La2O3-modified and 5% La2O3-8%BaO co-modified alumina (Ba-8) samples exhibited larger specific surface area and pore volume after calcination at 1273 K. N2 adsorption and desorption isotherms of all alumina exhibited that their surface pore structure was slit-shape and ink-shape pores, pore diameter distribution of Ba-8 was broader and centered between 5 and 10 nm, and other samples centered at 10 nm. NH3-TPD results indicated that the larger the BaO doping concentration, the less the acidic amount was. At the same time, surface acidity of alumina apparently became weak. NO2-TPD results showed that BaO doped alumina adsorbed more NO2 than La2O3 doped, sample Ba-8 adsorbed the most NO2. As sample Ba-8 simultaneously exhibited od textural properties, proper surface acidic amount, acidity and stronger NO2 adsorption capacity, it had the best catalytic performance when it was used as catalyst carrier. The temperatures of light-off and complete conversion of C3H8 were 526 K and 593 K, respectively.
La-Ba co-modified alumina was prepared from two kinds of pseudo boehmite and HNO3 as peptizer by peptizing method. The structure and surface property of the alumina were characterized by XRD, BET surface area analyzer, NH3-temperature programmed desorption and NO2-temperature programmed desorption technology. XRD results showed that γ-Al2O3 phase existed in all the modified alumina samples after calcination at 1273 K. A little BaCO3 was generated when content of BaO was increased to 14%(w). BET results showed that both of 5%(w) La2O3-modified and 5% La2O3-8%BaO co-modified alumina (Ba-8) samples exhibited larger specific surface area and pore volume after calcination at 1273 K. N2 adsorption and desorption isotherms of all alumina exhibited that their surface pore structure was slit-shape and ink-shape pores, pore diameter distribution of Ba-8 was broader and centered between 5 and 10 nm, and other samples centered at 10 nm. NH3-TPD results indicated that the larger the BaO doping concentration, the less the acidic amount was. At the same time, surface acidity of alumina apparently became weak. NO2-TPD results showed that BaO doped alumina adsorbed more NO2 than La2O3 doped, sample Ba-8 adsorbed the most NO2. As sample Ba-8 simultaneously exhibited od textural properties, proper surface acidic amount, acidity and stronger NO2 adsorption capacity, it had the best catalytic performance when it was used as catalyst carrier. The temperatures of light-off and complete conversion of C3H8 were 526 K and 593 K, respectively.
2007, 23(11): 1743-1746
doi: 10.3866/PKU.WHXB20071117
Abstract:
The autocatalytic electroless deposition (AED) of palladiumonto p-silicon (100) with hydrogen termination was studied. Pd films were prepared by immersing the hydrogen-terminated silicon wafers into conventional HF-PdCl2-HCl solution at room temperature. The anodic stripping behaviors and morphologies of the Pd deposits were studied using cyclic voltammetry (CV), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The results showed that the Pd growth was in Volmer-Weber (VW) mode and the Pd filmhad od adhesion.
The autocatalytic electroless deposition (AED) of palladiumonto p-silicon (100) with hydrogen termination was studied. Pd films were prepared by immersing the hydrogen-terminated silicon wafers into conventional HF-PdCl2-HCl solution at room temperature. The anodic stripping behaviors and morphologies of the Pd deposits were studied using cyclic voltammetry (CV), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The results showed that the Pd growth was in Volmer-Weber (VW) mode and the Pd filmhad od adhesion.
2007, 23(11): 1747-1752
doi: 10.3866/PKU.WHXB20071118
Abstract:
In this research, different polypyrrole (PPy) film samples with same thickness were electro-polymerized on Pt micro-disk electrode by method of chronopotentiometry at current densities, ranging from 0.05 mA·cm-2 to 10 mA·cm-2. The electrochemical behaviors of obtained PPy samples were investigated in lithium perchlorate-proylene carbonate electrolyte by electrochemical methods: cyclic voltammetry (CV), chronopotentionmetry and electrochemical impedance spectroscopy (EIS). The results indicated that the polyprrole samples fabricated at suitable current density,t hat was, 1-5 mA·cm-2, could exhibit better electrochemical behavior, such as, higher d egree of electrochemical redox reversibility, more positive redox potential, and larger capacity. It was found that each of the potential response signals was considerably stable and there was a clear linear relationship between corresponding potential response signal and used electro-polymerization current density in the process of electro-polymerization reaction. At the condition of suitable current density, corresponding potential signal was changed from3.9Vto 4.1 V (vs Li/Li+) with the increasing of used electro-polymerization current density. Moreover, each outstanding properties, for example, the most doping degree, 30%or so, lower membrane impedance and charge transfer impedance at oxidated state, could be achieved on the PPy samples fabricated at abovementioned suitable current density. It was also found that each kind of obtained polypyrrole sample exhibited excellent columbic efficiency and electrochemical reversibility during galvanostatic charge/discharge process in the electrolytes of Li-ion battery. Those polypyrrole samples obtained at abovementioned suitable electro-polymerization condition should be promising candidate for the fabrication of the positive electrode of secondary lithium/LiClO4 /polypyrrole battery.
In this research, different polypyrrole (PPy) film samples with same thickness were electro-polymerized on Pt micro-disk electrode by method of chronopotentiometry at current densities, ranging from 0.05 mA·cm-2 to 10 mA·cm-2. The electrochemical behaviors of obtained PPy samples were investigated in lithium perchlorate-proylene carbonate electrolyte by electrochemical methods: cyclic voltammetry (CV), chronopotentionmetry and electrochemical impedance spectroscopy (EIS). The results indicated that the polyprrole samples fabricated at suitable current density,t hat was, 1-5 mA·cm-2, could exhibit better electrochemical behavior, such as, higher d egree of electrochemical redox reversibility, more positive redox potential, and larger capacity. It was found that each of the potential response signals was considerably stable and there was a clear linear relationship between corresponding potential response signal and used electro-polymerization current density in the process of electro-polymerization reaction. At the condition of suitable current density, corresponding potential signal was changed from3.9Vto 4.1 V (vs Li/Li+) with the increasing of used electro-polymerization current density. Moreover, each outstanding properties, for example, the most doping degree, 30%or so, lower membrane impedance and charge transfer impedance at oxidated state, could be achieved on the PPy samples fabricated at abovementioned suitable current density. It was also found that each kind of obtained polypyrrole sample exhibited excellent columbic efficiency and electrochemical reversibility during galvanostatic charge/discharge process in the electrolytes of Li-ion battery. Those polypyrrole samples obtained at abovementioned suitable electro-polymerization condition should be promising candidate for the fabrication of the positive electrode of secondary lithium/LiClO4 /polypyrrole battery.
2007, 23(11): 1753-1759
doi: 10.3866/PKU.WHXB20071119
Abstract:
A kind of core-shell Cu/Al powder has been prepared via a facile displacement method, in which the micron-sized Al cores were coated in Cu shells. SEM, EDS and XRD were employed to characterize the samples. The thermal performance of micron-sized Al particles and Cu/Al micron-nano composites with WO3 were investigated by differential scanning calorimetry (DSC) as a function of the equivalence ratio. Mechanisms of thermite reactions have been proposed. Results indicated that the reactivity of Cu/Al micron-nano composites with WO3 was significantly higher than that of micron-sized Al particles, but depending strongly on equivalence ratio. The optimum equivalence was reached when the composites were fuel slightly rich. The activation energy of Cu/Al-WO3 was decreased by 68.185 kJ·mol-1 compared with that of Al-WO3.
A kind of core-shell Cu/Al powder has been prepared via a facile displacement method, in which the micron-sized Al cores were coated in Cu shells. SEM, EDS and XRD were employed to characterize the samples. The thermal performance of micron-sized Al particles and Cu/Al micron-nano composites with WO3 were investigated by differential scanning calorimetry (DSC) as a function of the equivalence ratio. Mechanisms of thermite reactions have been proposed. Results indicated that the reactivity of Cu/Al micron-nano composites with WO3 was significantly higher than that of micron-sized Al particles, but depending strongly on equivalence ratio. The optimum equivalence was reached when the composites were fuel slightly rich. The activation energy of Cu/Al-WO3 was decreased by 68.185 kJ·mol-1 compared with that of Al-WO3.
2007, 23(11): 1760-1764
doi: 10.3866/PKU.WHXB20071120
Abstract:
Mesoporous silicon dioxide materials doped with tungsten were synthesized by hydrothermal technique, employing nonionic surfactant block copolymer (P123) as template, ethyl silicate (TEOS) as inorganic precursor and sodium tungstate (Na2WO4·2H2O) as the source of tungsten. Several methods such as XRD, HRTEM, EDX, FT-IR and nitrogen adsorption-desorption isotherms were employed to characterize the structure of the W-doped SiO2 mesoporous materials and the state of tungsten in the mesoporous materials. The results showed that the tungsten species in W-SiO2 was highly dispersed when the amount of WO3 was less than 10%; when the amount of WO3 was 20%, some WO3 crystal could be detected in W-SiO2. When the amount of WO3 was lower than 60%, well organized pore structures could still be detected in W-SiO2 material. As the amount of WO3 was more than 60%, the mesoprous structure was collapsed.
Mesoporous silicon dioxide materials doped with tungsten were synthesized by hydrothermal technique, employing nonionic surfactant block copolymer (P123) as template, ethyl silicate (TEOS) as inorganic precursor and sodium tungstate (Na2WO4·2H2O) as the source of tungsten. Several methods such as XRD, HRTEM, EDX, FT-IR and nitrogen adsorption-desorption isotherms were employed to characterize the structure of the W-doped SiO2 mesoporous materials and the state of tungsten in the mesoporous materials. The results showed that the tungsten species in W-SiO2 was highly dispersed when the amount of WO3 was less than 10%; when the amount of WO3 was 20%, some WO3 crystal could be detected in W-SiO2. When the amount of WO3 was lower than 60%, well organized pore structures could still be detected in W-SiO2 material. As the amount of WO3 was more than 60%, the mesoprous structure was collapsed.
2007, 23(11): 1765-1770
doi: 10.3866/PKU.WHXB20071121
Abstract:
To understand the substituting effects of imidazole ring on the reaction equilibrium, the interactions between diperoxovanadate complex NH4[OV(O2)2{2-(2’-Pyridine)-Imidazole}]·4H2O (abbr. bpV(Imi-Py)) and a series of imidazole-like ligands (imidazole, 2-methyl-imidazole, 4-methyl-imidazole, and histidine) in solution were explored usingmultinuclear (1H, 13C, and 51V)magnetic resonance, diffusionordered spectroscopy (DOSY), and variable temperature NMR in 0.15 mol·L -1 NaCl ionic medium for mimicking the physiological conditions. The experimental results indicatedthat the activities of bpV(Imi-Py) and organic ligandswere as follows: imidazole≈4-methyl-imidazole>2-methyl-imidazole>histidine. The steric effect of the organic ligands affects the reaction equilibrium. At the same time, newsix-coordinated peroxovanadate species [OV(O2)2L]- (L= imidazole-like ligands) were formed due to the competitive coordination between 2-(2’-pyridyl)-imidazole and the imidazole-like ligands. When the ligand was 4-methyl-imidazole or histidine, a pair of isomers was formed.
To understand the substituting effects of imidazole ring on the reaction equilibrium, the interactions between diperoxovanadate complex NH4[OV(O2)2{2-(2’-Pyridine)-Imidazole}]·4H2O (abbr. bpV(Imi-Py)) and a series of imidazole-like ligands (imidazole, 2-methyl-imidazole, 4-methyl-imidazole, and histidine) in solution were explored usingmultinuclear (1H, 13C, and 51V)magnetic resonance, diffusionordered spectroscopy (DOSY), and variable temperature NMR in 0.15 mol·L -1 NaCl ionic medium for mimicking the physiological conditions. The experimental results indicatedthat the activities of bpV(Imi-Py) and organic ligandswere as follows: imidazole≈4-methyl-imidazole>2-methyl-imidazole>histidine. The steric effect of the organic ligands affects the reaction equilibrium. At the same time, newsix-coordinated peroxovanadate species [OV(O2)2L]- (L= imidazole-like ligands) were formed due to the competitive coordination between 2-(2’-pyridyl)-imidazole and the imidazole-like ligands. When the ligand was 4-methyl-imidazole or histidine, a pair of isomers was formed.
2007, 23(11): 1771-1775
doi: 10.3866/PKU.WHXB20071122
Abstract:
Sodiumalginate (SA) and chitosan (CS) were modified by Ca2+ and glutaraldehyde (GA) as linking reagents respectively to prepare Ni-mSA-mCS (m: modified) bipolar membrane (BM). The nickel net was settled down to the surface of the mSA cation membrane as a cathode. It improved the mechanical property of membranes and realized zero polar distance, minimized the IR drop in the cathode electrolyte. It was characterized by FTIR and SEM, and used as a separator in the electrolysis cell to produce thioglycolic acid (TGA). The experiment results showed that TGA was preparedeffectivelyby electro-reduction of dithiodidiglycolic acid (DTDGA). The current efficiencywas up to 66.7% at room temperature (25 ℃) under the current density of 10 mA·cm-2. Compared with the traditional metal reduction method, the electro-reduction technology saves the zinc powder and eliminates the pollution to environment.
Sodiumalginate (SA) and chitosan (CS) were modified by Ca2+ and glutaraldehyde (GA) as linking reagents respectively to prepare Ni-mSA-mCS (m: modified) bipolar membrane (BM). The nickel net was settled down to the surface of the mSA cation membrane as a cathode. It improved the mechanical property of membranes and realized zero polar distance, minimized the IR drop in the cathode electrolyte. It was characterized by FTIR and SEM, and used as a separator in the electrolysis cell to produce thioglycolic acid (TGA). The experiment results showed that TGA was preparedeffectivelyby electro-reduction of dithiodidiglycolic acid (DTDGA). The current efficiencywas up to 66.7% at room temperature (25 ℃) under the current density of 10 mA·cm-2. Compared with the traditional metal reduction method, the electro-reduction technology saves the zinc powder and eliminates the pollution to environment.
2007, 23(11): 1776-1780
doi: 10.3866/PKU.WHXB20071123
Abstract:
By introducing the functional theory into the calculation of electric double layer (EDL) interaction, the interaction energies of two identical parallel plates were calculated at 128, 77, and 25 mV potentials, respectively. Compared with the results from the Debye-Huckel (DH), Langmuir, and numerical methods, respectively, the results showed that DH and Langmuir methods were applicable just for the critical potentials, but the functional approach with quite accurate and simple analytic expression held true at any potential.
By introducing the functional theory into the calculation of electric double layer (EDL) interaction, the interaction energies of two identical parallel plates were calculated at 128, 77, and 25 mV potentials, respectively. Compared with the results from the Debye-Huckel (DH), Langmuir, and numerical methods, respectively, the results showed that DH and Langmuir methods were applicable just for the critical potentials, but the functional approach with quite accurate and simple analytic expression held true at any potential.
2007, 23(11): 1781-1786
doi: 10.3866/PKU.WHXB20071124
Abstract:
The ground states of 3-(3’-pyridyl)-6-aryl-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole derivatives (in which, aryl is phenyl (compound A), 3’-pyridyl (compoundB), or styryl (compoundC))were optimized with density functional theory at B3LYP level. Ionization potential (IP), electron affinity (EA), and other energies of the three compounds were calculated. Absorption spectra were obtained by using Zerner’s intermediate neglect of differential overlap (ZINDO) and time-depended density functional theory (TDDFT)methods. Single-excitation configuration interaction (CIS)method was used to calculate the S1 excited states of the three compounds and to analyze the relationship between their energies and emission spectra. The absorption and emission spectra were calculated in solvent and compared with the experimental data. The results indicated that the abilities for accepting electrons from A, B to C were strengthened for their electron affinities were increased in turn, and the absorption as well as emission spectra were red-shifted.
The ground states of 3-(3’-pyridyl)-6-aryl-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole derivatives (in which, aryl is phenyl (compound A), 3’-pyridyl (compoundB), or styryl (compoundC))were optimized with density functional theory at B3LYP level. Ionization potential (IP), electron affinity (EA), and other energies of the three compounds were calculated. Absorption spectra were obtained by using Zerner’s intermediate neglect of differential overlap (ZINDO) and time-depended density functional theory (TDDFT)methods. Single-excitation configuration interaction (CIS)method was used to calculate the S1 excited states of the three compounds and to analyze the relationship between their energies and emission spectra. The absorption and emission spectra were calculated in solvent and compared with the experimental data. The results indicated that the abilities for accepting electrons from A, B to C were strengthened for their electron affinities were increased in turn, and the absorption as well as emission spectra were red-shifted.
2007, 23(11): 1787-1791
doi: 10.3866/PKU.WHXB20071125
Abstract:
The electrochromic behaviors of the tetra nal Bi2O3 films deposited by pulsed laser deposition at 300 ℃ were investigated by potential step and cyclic voltammetry coupled with an in situ charge-coupled device (CCD) spectrophotometer. The time-resolved absorption spectrum determined by potential step method indicated that the coloration time for Bi2O3 film was estimated to be 30 s. In addition, the electrochromic properties determined by cyclic voltammetry showed that this film could exhibit a significantly reversible variation between transparent and dark brown more than 50 times on switching between 3.5 and 0.7 V. The color efficiency at 630 nm was estimated to be 15 cm2·C-1.
The electrochromic behaviors of the tetra nal Bi2O3 films deposited by pulsed laser deposition at 300 ℃ were investigated by potential step and cyclic voltammetry coupled with an in situ charge-coupled device (CCD) spectrophotometer. The time-resolved absorption spectrum determined by potential step method indicated that the coloration time for Bi2O3 film was estimated to be 30 s. In addition, the electrochromic properties determined by cyclic voltammetry showed that this film could exhibit a significantly reversible variation between transparent and dark brown more than 50 times on switching between 3.5 and 0.7 V. The color efficiency at 630 nm was estimated to be 15 cm2·C-1.
2007, 23(11): 1792-1796
doi: 10.3866/PKU.WHXB20071126
Abstract:
Configurations of C50 fullerene and its two dimers C100 and C101 were optimized at B3LYP/6-31G* level. On the basis of the optimized geometrical structures, their excited states, electronic absorption spectra and third-order nonlinear optical polarizabilities in different optical processes were investigated at TDB3LYP/3-21G* level coupled with sum-over-states method. The results obtained from the electronic absorption spectra showed that the largest wavelength absorption peaks of C50 fullerene dimers had a remarkable red shift compared with that of C50 fullerene, and their third-order nonlinear optical polarizabilities increased after the dimerization. Especially, [5,5]-[5,5] dumbbell-like C50 fullerene dimer C101 had a larger third-order nonlinear optical polarizability than [2+2]-closed C50 fullerene dimer C100.
Configurations of C50 fullerene and its two dimers C100 and C101 were optimized at B3LYP/6-31G* level. On the basis of the optimized geometrical structures, their excited states, electronic absorption spectra and third-order nonlinear optical polarizabilities in different optical processes were investigated at TDB3LYP/3-21G* level coupled with sum-over-states method. The results obtained from the electronic absorption spectra showed that the largest wavelength absorption peaks of C50 fullerene dimers had a remarkable red shift compared with that of C50 fullerene, and their third-order nonlinear optical polarizabilities increased after the dimerization. Especially, [5,5]-[5,5] dumbbell-like C50 fullerene dimer C101 had a larger third-order nonlinear optical polarizability than [2+2]-closed C50 fullerene dimer C100.
2007, 23(11): 1797-1802
doi: 10.3866/PKU.WHXB20071127
Abstract:
Anodization of titanium in a fluorinated glycerol, dimethyl sulfoxide (DMSO) and H2O electrolyte was investigated. The prepared anodic filmhad a highly ordered nanotube-array surface architecture with 0.4 to 1.5 μm tube length. Field emission scanning electron microscopy(FESEM) technique had been used to characterize the morphology of TiO2 nanotubes. The result showed that voltage and the volume ratio of DMSO to H2O were important factors to control the appearance and sizes of the TiO2 nanotube arrays. The average pore size increased with increasing anodizing voltage and decreasing the volume ratio of DMSO to H2O. And tube length increased with increasing anodizing voltage and the volume ratio of DMSO to H2O. A possible growth mechanism for the nanotubes formation had been proposed. X-ray diffraction (XRD) technique had been used to characterize the phase of TiO2 nanotubes. It was showed that the TiO2 structure depends on the heating condition. Amorphous phase was found at room temperature, the anatase phase was the predominant phase at 350 ℃, and with further heating to 550 ℃ the coexistence of rutile phase with anatase phase could be seen. Moreover the photoelectrochemical response of the nanotube-array photoeledtrode was studied using a 1 mol·L-1 KOH solution under UV illumination.
Anodization of titanium in a fluorinated glycerol, dimethyl sulfoxide (DMSO) and H2O electrolyte was investigated. The prepared anodic filmhad a highly ordered nanotube-array surface architecture with 0.4 to 1.5 μm tube length. Field emission scanning electron microscopy(FESEM) technique had been used to characterize the morphology of TiO2 nanotubes. The result showed that voltage and the volume ratio of DMSO to H2O were important factors to control the appearance and sizes of the TiO2 nanotube arrays. The average pore size increased with increasing anodizing voltage and decreasing the volume ratio of DMSO to H2O. And tube length increased with increasing anodizing voltage and the volume ratio of DMSO to H2O. A possible growth mechanism for the nanotubes formation had been proposed. X-ray diffraction (XRD) technique had been used to characterize the phase of TiO2 nanotubes. It was showed that the TiO2 structure depends on the heating condition. Amorphous phase was found at room temperature, the anatase phase was the predominant phase at 350 ℃, and with further heating to 550 ℃ the coexistence of rutile phase with anatase phase could be seen. Moreover the photoelectrochemical response of the nanotube-array photoeledtrode was studied using a 1 mol·L-1 KOH solution under UV illumination.
2007, 23(11): 1803-1807
doi: 10.3866/PKU.WHXB20071128
Abstract:
The photocatalytic degradation of surfactant cetyltrimethylammonium bromide (CTAB) and organic pigment light fast scarlet BBN (barium 4-[(5-chloro-4-methyl-2-sulfophenyl) azo]-3-hydroxy-2-naphthalenecarboxylate, BBN) was investigated using TiO2 as photocatalyst in aqueous solution under ultraviolet light irradiation. Decolorization rate and interaction mechanism of the surfactant and BBN were discussed, and the adsorption model of BBN and surfactant on TiO2 was also shown. The results showed that the degradation of the bicomponents depended on pH and substrate concentration obviously. The alkaline medium was favorable to the degradation of BBN and CTAB. The degradation of the two compounds systemwas faster than individual organic compounds in neutral condition (pH=6.8). The degradation of CTAB was slightly slower than that without BBN in alkaline (pH=9.2). The concentration of CTAB greatly affected the discoloration of BBN. When the concentration of CTAB was 1 cmc, the degradation rates of BBN and CTAB were the fastest. BBN was adsorbed strongly on TiO2 surface, and was preferentially degraded.
The photocatalytic degradation of surfactant cetyltrimethylammonium bromide (CTAB) and organic pigment light fast scarlet BBN (barium 4-[(5-chloro-4-methyl-2-sulfophenyl) azo]-3-hydroxy-2-naphthalenecarboxylate, BBN) was investigated using TiO2 as photocatalyst in aqueous solution under ultraviolet light irradiation. Decolorization rate and interaction mechanism of the surfactant and BBN were discussed, and the adsorption model of BBN and surfactant on TiO2 was also shown. The results showed that the degradation of the bicomponents depended on pH and substrate concentration obviously. The alkaline medium was favorable to the degradation of BBN and CTAB. The degradation of the two compounds systemwas faster than individual organic compounds in neutral condition (pH=6.8). The degradation of CTAB was slightly slower than that without BBN in alkaline (pH=9.2). The concentration of CTAB greatly affected the discoloration of BBN. When the concentration of CTAB was 1 cmc, the degradation rates of BBN and CTAB were the fastest. BBN was adsorbed strongly on TiO2 surface, and was preferentially degraded.
2007, 23(11): 1808-1810
doi: 10.3866/PKU.WHXB20071129
Abstract:
The polarizabilities of ZrO2 and SiO2 nanoparticles were studied on the basis of hyper Rayleigh scattering measurement. It was found that the polarizability of system depended on both particle size and concentration.
The polarizabilities of ZrO2 and SiO2 nanoparticles were studied on the basis of hyper Rayleigh scattering measurement. It was found that the polarizability of system depended on both particle size and concentration.
2007, 23(11): 1811-1814
doi: 10.3866/PKU.WHXB20071130
Abstract:
The unsaturated germylenoid H2C=GeLiCl was studied by using the DFT method at the B3LYP/6-311G(d,p) level of theory. Geometry optimization calculations indicated that H2C=GeLiCl had three equilibrium configurations, in which the non-planar p-complex was lowest in energy and was the most stable structure. The transition states for isomerization reactions of H2C=GeLiCl were located and the energy barriers were calculated. For the most stable structure, the vibrational frequencies and infrared intensities had been predicted.
The unsaturated germylenoid H2C=GeLiCl was studied by using the DFT method at the B3LYP/6-311G(d,p) level of theory. Geometry optimization calculations indicated that H2C=GeLiCl had three equilibrium configurations, in which the non-planar p-complex was lowest in energy and was the most stable structure. The transition states for isomerization reactions of H2C=GeLiCl were located and the energy barriers were calculated. For the most stable structure, the vibrational frequencies and infrared intensities had been predicted.
2007, 23(11): 1815-1820
doi: 10.3866/PKU.WHXB20071131
Abstract:
The pharmacophore model of p53-MDM2 binding inhibitors was established by the Catalyst software with the training set of 24 inhibitors containing 5 different kinds of structures. Based on the information of p53-MDM2 binding structure, a fitting pharmacophore model (Correl=0.941, Config=17.530, ⊿cost=150.830) including one hydrogen-bonding acceptor, one aromatic ring center and three aliphatic hydrophobic cores was confirmed. The pharmacophore model could be used to screen new lead compound of p53-MDM2 binding inhibitor.
The pharmacophore model of p53-MDM2 binding inhibitors was established by the Catalyst software with the training set of 24 inhibitors containing 5 different kinds of structures. Based on the information of p53-MDM2 binding structure, a fitting pharmacophore model (Correl=0.941, Config=17.530, ⊿cost=150.830) including one hydrogen-bonding acceptor, one aromatic ring center and three aliphatic hydrophobic cores was confirmed. The pharmacophore model could be used to screen new lead compound of p53-MDM2 binding inhibitor.
2007, 23(11): 1821-1826
doi: 10.3866/PKU.WHXB20071132
Abstract:
Double-layer heterojunction organic electroluminescent devices (OELDs) with a conventional structure of anode/N,N’-bis-(3-naphthyl)-N,N’-biphenyl-(1,1’-biphenyl)-4,4’-diamine [NPB(40 nm)]/tris-(8-hydroxyquinoline)-aluminum[Alq3(50 nm)]/cathode were fabricated using different materials as anode and cathode. The impact of electrode materials on device performance was studied by varying the electrodes of OELDs. The testing results of device electroluminescent characteristics showed that the current-voltage (I-V) relationship of the devices is in accordance with the theory of trapped charge limited current (TCLC) regime. Due to the disorder of organic material energy levels and the dependence of carrier mobility on temperature as well as electric field, charge carrier injection ability of different electrodes was not necessarily dependent on the work function of the electrodes. The introduction of hole transporting layer in double-layer devices enables the recombination zone of charge carriers to locate near the interface of organic heterojunction, which efficiently reduces the quenching effect of electrode on excitons, and thus largely enhances device performance. In addition, the microcavity effect in OELDs device with metallic electrode may lead to the shift of emissive spectra and the shrinkage of spectrum full width at half maximum. The results showed that enhanced device performance compared with conventional device can be anticipated by surface modification and optimization of metallic electrodes.
Double-layer heterojunction organic electroluminescent devices (OELDs) with a conventional structure of anode/N,N’-bis-(3-naphthyl)-N,N’-biphenyl-(1,1’-biphenyl)-4,4’-diamine [NPB(40 nm)]/tris-(8-hydroxyquinoline)-aluminum[Alq3(50 nm)]/cathode were fabricated using different materials as anode and cathode. The impact of electrode materials on device performance was studied by varying the electrodes of OELDs. The testing results of device electroluminescent characteristics showed that the current-voltage (I-V) relationship of the devices is in accordance with the theory of trapped charge limited current (TCLC) regime. Due to the disorder of organic material energy levels and the dependence of carrier mobility on temperature as well as electric field, charge carrier injection ability of different electrodes was not necessarily dependent on the work function of the electrodes. The introduction of hole transporting layer in double-layer devices enables the recombination zone of charge carriers to locate near the interface of organic heterojunction, which efficiently reduces the quenching effect of electrode on excitons, and thus largely enhances device performance. In addition, the microcavity effect in OELDs device with metallic electrode may lead to the shift of emissive spectra and the shrinkage of spectrum full width at half maximum. The results showed that enhanced device performance compared with conventional device can be anticipated by surface modification and optimization of metallic electrodes.
