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2008 Volume 24 Issue 6
2008, 24(06):
Abstract:
2008, 24(06): 927-931
doi: 10.1016/S1872-1508(08)60038-8
Abstract:
One dimension (1D) Fe-B amorphous alloy nanowires with diameter of 50-80 nm and length of several micrometers were synthesized under weak DC(direct current) magnetic field by KBH4 reducing in aqueous solution. The structure, composition, and morphology were characterized by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES), and scanning electron microscope (SEM), respectively. The results revealed that the magnetic field led to the fabrication of Fe-B amorphous alloy nanowire structure. Vibrating sample magnetometer (VSM) has been used to detect the magnetic properties of the samples. The results showed that the inducing of magnetic field had an obvious effect on the magnetic properties of the samples.
One dimension (1D) Fe-B amorphous alloy nanowires with diameter of 50-80 nm and length of several micrometers were synthesized under weak DC(direct current) magnetic field by KBH4 reducing in aqueous solution. The structure, composition, and morphology were characterized by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES), and scanning electron microscope (SEM), respectively. The results revealed that the magnetic field led to the fabrication of Fe-B amorphous alloy nanowire structure. Vibrating sample magnetometer (VSM) has been used to detect the magnetic properties of the samples. The results showed that the inducing of magnetic field had an obvious effect on the magnetic properties of the samples.
2008, 24(06): 932-938
doi: 10.1016/S1872-1508(08)60039-X
Abstract:
Aseries ofAu/Fe2O3 catalysts for the water gas shift (WGS) reaction were prepared by modified deposition-precipitation method. The sample calcined at 300 ℃ showed higher catalytic activity and better stability than other samples. Using N2 physisorption, in situ XRD, H2-TPR, and XPS techniques, the influence of calcination temperature on properties of Au/Fe2O3 catalyst was explored, and the cause of deactivation was analyzed as well. The results showed that the catalytic behaviors were related to the interaction between Au and Fe2O3, and the reductive property of support, both of which were significantly affected by calcination temperature. Furthermore, according to the results of XPS, although stable carbonate and carbonyl surface species were found on the spent catalysts, the semiquantitative analysis of these species indicated that they were not the main cause of the deactivation. In fact, the deactivation of Au/Fe2O3 was sensitive to the structure change of support. During the water gas shift reaction, Fe3O4 particle would aggregate and crystallize leading to increase in the crystallinity of support and a significant reduction in the surface area of the catalysts, which resulted in the deactivation of Au/Fe2O3.
Aseries ofAu/Fe2O3 catalysts for the water gas shift (WGS) reaction were prepared by modified deposition-precipitation method. The sample calcined at 300 ℃ showed higher catalytic activity and better stability than other samples. Using N2 physisorption, in situ XRD, H2-TPR, and XPS techniques, the influence of calcination temperature on properties of Au/Fe2O3 catalyst was explored, and the cause of deactivation was analyzed as well. The results showed that the catalytic behaviors were related to the interaction between Au and Fe2O3, and the reductive property of support, both of which were significantly affected by calcination temperature. Furthermore, according to the results of XPS, although stable carbonate and carbonyl surface species were found on the spent catalysts, the semiquantitative analysis of these species indicated that they were not the main cause of the deactivation. In fact, the deactivation of Au/Fe2O3 was sensitive to the structure change of support. During the water gas shift reaction, Fe3O4 particle would aggregate and crystallize leading to increase in the crystallinity of support and a significant reduction in the surface area of the catalysts, which resulted in the deactivation of Au/Fe2O3.
2008, 24(06): 939-944
doi: 10.1016/S1872-1508(08)60040-6
Abstract:
Aluminum was successfully electrodeposited on Al electrodes from aluminum chloride (AlCl3)/triethylamine hydrochloride (Et3NHCl) ionic liquids by the constant potential electrolysis. Electrical conductivities of AlCl3/Et3NHCl ionic liquids were measured as a function of the temperature and composition. The nucleation processes and the influence of experimental conditions on the current efficiency and surface morphology of aluminum electrodeposits were studied on Al electrodes from 2:1 molar ratio AlCl3/Et3NHCl ionic liquid. The electrical conductivities of ionic liquids increased as the electrolyte temperature increased, following the Arrhenius behavior. Analyses of the chronoamperograms indicated that the deposition process of aluminium on Al substrates was controlled by instantaneous nucleation with diffusion-controlled growth. Constant potential deposition experiments showed that the electrodeposits obtained on Al electrodes were dense, continuous, and well adherent, and the current efficiency was 73% at -2.4 V ( vs Pt) for 20 min electrolysis at room temperature. The purity of aluminum electrodeposits on Al electrodes was above 96% (w).
Aluminum was successfully electrodeposited on Al electrodes from aluminum chloride (AlCl3)/triethylamine hydrochloride (Et3NHCl) ionic liquids by the constant potential electrolysis. Electrical conductivities of AlCl3/Et3NHCl ionic liquids were measured as a function of the temperature and composition. The nucleation processes and the influence of experimental conditions on the current efficiency and surface morphology of aluminum electrodeposits were studied on Al electrodes from 2:1 molar ratio AlCl3/Et3NHCl ionic liquid. The electrical conductivities of ionic liquids increased as the electrolyte temperature increased, following the Arrhenius behavior. Analyses of the chronoamperograms indicated that the deposition process of aluminium on Al substrates was controlled by instantaneous nucleation with diffusion-controlled growth. Constant potential deposition experiments showed that the electrodeposits obtained on Al electrodes were dense, continuous, and well adherent, and the current efficiency was 73% at -2.4 V ( vs Pt) for 20 min electrolysis at room temperature. The purity of aluminum electrodeposits on Al electrodes was above 96% (w).
2008, 24(06): 945-950
doi: 10.1016/S1872-1508(08)60041-8
Abstract:
The rate constants for the reactions between·OH and six reduced sulfur compounds in air, N2, and O2 were measured using relative rate constant method in a 180-L Teflon bag at 298 K and 1.013伊105 Pa. These results were compared with previous published data and were discussed in terms of trends in different buffer gases.
The rate constants for the reactions between·OH and six reduced sulfur compounds in air, N2, and O2 were measured using relative rate constant method in a 180-L Teflon bag at 298 K and 1.013伊105 Pa. These results were compared with previous published data and were discussed in terms of trends in different buffer gases.
2008, 24(06): 951-954
doi: 10.1016/S1872-1508(08)60042-X
Abstract:
A simple acid treatment method was applied to remove the catalyst impurities and other residues contaminated in the vertically aligned carbon nanotube arrays. We demonstrated that acid treatment was an efficient approach for aligned carbon nanotube purification. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to characterize the morphology of the aligned carbon nanotube arrays and to determine the efficiency of the purification. Using hydrochloric acid could efficiently eliminate catalyst impurities and retain the original structures of the aligned carbon nanotube arrays. The method provided a simple, economical, and effective way to purify the aligned carbon nanotubes, and it would promote the applications of vertically aligned carbon nanotube arrays in electronics field.
A simple acid treatment method was applied to remove the catalyst impurities and other residues contaminated in the vertically aligned carbon nanotube arrays. We demonstrated that acid treatment was an efficient approach for aligned carbon nanotube purification. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to characterize the morphology of the aligned carbon nanotube arrays and to determine the efficiency of the purification. Using hydrochloric acid could efficiently eliminate catalyst impurities and retain the original structures of the aligned carbon nanotube arrays. The method provided a simple, economical, and effective way to purify the aligned carbon nanotubes, and it would promote the applications of vertically aligned carbon nanotube arrays in electronics field.
2008, 24(06): 955-960
doi: 10.3866/PKU.WHXB20080606
Abstract:
1,3-bis (3-phenyl-3-oxopropanoyl)benzene (BPOB) was prepared by Claisen condensation of acetophenone and dimethyl isophthalate and characterized by elemental analysis, MS, 1H NMR, UV absorption spectrum, solid-state circular dichroism(CD) spectra, and X-ray single-crystal diffraction. The X-ray crystallographic data indicated that BPOB crystallized in a Sohncke group P212121, UV and 1H NMR showed that the enol tautomer was the most dominant form in solution, and the solid-state CD spectra and repeated recrytallization revealed that the formation of chiral BPOB crystals could be regarded as crystallization-induced asymmetric synthesis.
1,3-bis (3-phenyl-3-oxopropanoyl)benzene (BPOB) was prepared by Claisen condensation of acetophenone and dimethyl isophthalate and characterized by elemental analysis, MS, 1H NMR, UV absorption spectrum, solid-state circular dichroism(CD) spectra, and X-ray single-crystal diffraction. The X-ray crystallographic data indicated that BPOB crystallized in a Sohncke group P212121, UV and 1H NMR showed that the enol tautomer was the most dominant form in solution, and the solid-state CD spectra and repeated recrytallization revealed that the formation of chiral BPOB crystals could be regarded as crystallization-induced asymmetric synthesis.
2008, 24(06): 961-964
doi: 10.3866/PKU.WHXB20080607
Abstract:
The laser induced fluorescence (LIF) excitation spectrumof molecular ions in cooperating with resonance-enhanced multi-photon ionization (REMPI) process was demonstrated with CO+ ions. The CO+ ions at the ground X2∑+ state were prepared by (2+1) REMPI of supersonically cooled COmolecules at 230.1 nm, and the rovibronically resolved LIF spectra of CO+(A2∏1/2,3/2←X2∑+) were measured by scanning another laser in the range of 487-493 nm and 453-459 nm, which belong to (0,0) and (1,0) bands, respectively.
The laser induced fluorescence (LIF) excitation spectrumof molecular ions in cooperating with resonance-enhanced multi-photon ionization (REMPI) process was demonstrated with CO+ ions. The CO+ ions at the ground X2∑+ state were prepared by (2+1) REMPI of supersonically cooled COmolecules at 230.1 nm, and the rovibronically resolved LIF spectra of CO+(A2∏1/2,3/2←X2∑+) were measured by scanning another laser in the range of 487-493 nm and 453-459 nm, which belong to (0,0) and (1,0) bands, respectively.
2008, 24(06): 965-970
doi: 10.3866/PKU.WHXB200806081
Abstract:
The highly dispersed supported catalyst (Ru/ZrO2·xH2O) was prepared and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microsocpy. The results showed that ruthenium was reduced to low oxidation state and the average partical diameter of Ru particles was about 3.8 nm. The catalyst exhibited high activity in hydrogenation of quinoline under the mild reaction conditions, 40 ℃, 2 MPa, quinoline/Ru molar ratio of 250/1 and H2O as solvent. The conversion of quinoline was 98.2% and the selectity of 1,2,3,4-tetrahydroquinoline was 98.0%. The catalyst can be reused for several times. The mechanismof quinoline hydrogenation over Ru/ZrO2·xH2Ocatalyst was discussed. The coordination of nitrogen atomof quinoline on the surface of ruthenium nanoparticles and the effect of hydrogen bond between OH groups on ZrO2 surface and nitrogen in quinoline were favourable for the desorption of the substrate and products fromthe surface of catalyst.
The highly dispersed supported catalyst (Ru/ZrO2·xH2O) was prepared and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microsocpy. The results showed that ruthenium was reduced to low oxidation state and the average partical diameter of Ru particles was about 3.8 nm. The catalyst exhibited high activity in hydrogenation of quinoline under the mild reaction conditions, 40 ℃, 2 MPa, quinoline/Ru molar ratio of 250/1 and H2O as solvent. The conversion of quinoline was 98.2% and the selectity of 1,2,3,4-tetrahydroquinoline was 98.0%. The catalyst can be reused for several times. The mechanismof quinoline hydrogenation over Ru/ZrO2·xH2Ocatalyst was discussed. The coordination of nitrogen atomof quinoline on the surface of ruthenium nanoparticles and the effect of hydrogen bond between OH groups on ZrO2 surface and nitrogen in quinoline were favourable for the desorption of the substrate and products fromthe surface of catalyst.
2008, 24(06): 971-976
doi: 10.3866/PKU.WHXB20080609
Abstract:
Continuous SiC(Al) fibers were prepared by polymer-derived method using organometallic polymer polyaluminocarbosilane (PACS). The composition, structure, and properties of continuous SiC(Al) fibers were investigated by a series of analyses. The mechanism of high temperature resistance of the fibers was discussed through the comparison between Nicalon fibers and continuous SiC(Al) fibers. The results showed that the fibers exhibited excellent thermal stability. After heat treatment at 1800 ℃ in ar n for 1 h, the fibers maintained about 80% of the initial strength. Element analysis and 27Al MAS NMR indicated that the composition of continuous SiC(Al) fibers was close to stoichiometric ratio and the aluminum existed in the form of Al—O and Al—C bonds. The aluminum that existed in different manners could restrain the growth of grain of the fibers at super-high temperature. The high-temperature resistance of continuous SiC(Al) fibers was based on two factors: the near stoichiometric composition and the inhibition of the aluminumto the growth of the grain.
Continuous SiC(Al) fibers were prepared by polymer-derived method using organometallic polymer polyaluminocarbosilane (PACS). The composition, structure, and properties of continuous SiC(Al) fibers were investigated by a series of analyses. The mechanism of high temperature resistance of the fibers was discussed through the comparison between Nicalon fibers and continuous SiC(Al) fibers. The results showed that the fibers exhibited excellent thermal stability. After heat treatment at 1800 ℃ in ar n for 1 h, the fibers maintained about 80% of the initial strength. Element analysis and 27Al MAS NMR indicated that the composition of continuous SiC(Al) fibers was close to stoichiometric ratio and the aluminum existed in the form of Al—O and Al—C bonds. The aluminum that existed in different manners could restrain the growth of grain of the fibers at super-high temperature. The high-temperature resistance of continuous SiC(Al) fibers was based on two factors: the near stoichiometric composition and the inhibition of the aluminumto the growth of the grain.
2008, 24(06): 977-980
doi: 10.1016/S1872-1508(08)60043-1
Abstract:
Double-layer and triple-layer organic light-emitting diodes (OLEDs) were fabricated using a novel star-shaped hexafluorenylbenzene organic material, 1,2,3,4,5,6-hexakis(9,9-diethyl-9H-fluoren-2-yl)benzene (HKEthFLYPh) as an energy transfer layer, N,N’-bis-(1-naphthyl)-N,N’-diphenyl-(1,1’-biphenyl)-4,4’-diamine (NPB) as a hole-transport layer (HTL) and blue emissive layer (EML), and tris (8-hydroxyquinoline)aluminum (Alq3) as an electron-transport layer (ETL) and green light-emitting layer. Bright white light was obtained with a triple-layer device structure of indium-tin-oxide (ITO)/NPB (40 nm)/HKEthFLYPh (10 nm)/Alq3 (50 nm)/Mg:Ag (200 nm). A maximum luminance of 8523 cd·m-2 at 15 V and a power efficiency of 1.0 lm·W-1 at 5.5 V were achieved. The Commissions Internationale de L’Eclairage (CIE) coordinates of the device were (0.29, 0.34) at 9 V, which located in white light region. With increasing filmthickness of HKEthFLYPh, light emission intensity fromNPB increased compared to that of Alq3.
Double-layer and triple-layer organic light-emitting diodes (OLEDs) were fabricated using a novel star-shaped hexafluorenylbenzene organic material, 1,2,3,4,5,6-hexakis(9,9-diethyl-9H-fluoren-2-yl)benzene (HKEthFLYPh) as an energy transfer layer, N,N’-bis-(1-naphthyl)-N,N’-diphenyl-(1,1’-biphenyl)-4,4’-diamine (NPB) as a hole-transport layer (HTL) and blue emissive layer (EML), and tris (8-hydroxyquinoline)aluminum (Alq3) as an electron-transport layer (ETL) and green light-emitting layer. Bright white light was obtained with a triple-layer device structure of indium-tin-oxide (ITO)/NPB (40 nm)/HKEthFLYPh (10 nm)/Alq3 (50 nm)/Mg:Ag (200 nm). A maximum luminance of 8523 cd·m-2 at 15 V and a power efficiency of 1.0 lm·W-1 at 5.5 V were achieved. The Commissions Internationale de L’Eclairage (CIE) coordinates of the device were (0.29, 0.34) at 9 V, which located in white light region. With increasing filmthickness of HKEthFLYPh, light emission intensity fromNPB increased compared to that of Alq3.
2008, 24(06): 981-986
doi: 10.3866/PKU.WHXB20080611
Abstract:
Isomerization mechanism and conformation transformation of triazane were studied by quantum chemistry computation. The relationship between the energy and the conformation was obtained by a relaxed scan for all possible dihedral angles of triazane. By means of atoms in molecules (AIM) computation, the increase and decrease of the charge density of bond critical point and the positive and negative variation of its Laplace value induced by conformation can be obtained, which may provide clear information for the change, break, and formation of the nitrogen-nitrogen or nitrogen-hydrogen bond. Nature bond orbital (NBO) analysis revealed that the energy of isomer was increased by the steric effects, and it is decreased by the hyperconjugation effects. The relative stabilities of isomers can be attributed to the steric and hyperconjugation effects.
Isomerization mechanism and conformation transformation of triazane were studied by quantum chemistry computation. The relationship between the energy and the conformation was obtained by a relaxed scan for all possible dihedral angles of triazane. By means of atoms in molecules (AIM) computation, the increase and decrease of the charge density of bond critical point and the positive and negative variation of its Laplace value induced by conformation can be obtained, which may provide clear information for the change, break, and formation of the nitrogen-nitrogen or nitrogen-hydrogen bond. Nature bond orbital (NBO) analysis revealed that the energy of isomer was increased by the steric effects, and it is decreased by the hyperconjugation effects. The relative stabilities of isomers can be attributed to the steric and hyperconjugation effects.
2008, 24(06): 987-991
doi: 10.1016/S1872-1508(08)60044-3
Abstract:
Density and viscosity data of proline (Pro) in sodium dodecyl sulfate/cetyltrimethylammonium bromide/poly (oxyethylene) isooctyl phenyl ether in formamide were measured at 298.15, 303.15, 308.15, and 313.15 K and 0.1 MPa. The density data were utilized to evaluate standard partial molar volumes (φ0 v) and partial molar isobaric expansibility (φ0 E). The viscosity data were used to evaluate A-and B-coefficients, free energy of activation of viscous flow (⊿μ0*1 ) and (⊿μ0*2 ), per mole of solvent and solute respectively, enthalpy (⊿H*) and entropy (⊿utilized in the qualitative elucidation of the Pro-surfactant/formamide and Pro-Pro interactions in the present systems.
Density and viscosity data of proline (Pro) in sodium dodecyl sulfate/cetyltrimethylammonium bromide/poly (oxyethylene) isooctyl phenyl ether in formamide were measured at 298.15, 303.15, 308.15, and 313.15 K and 0.1 MPa. The density data were utilized to evaluate standard partial molar volumes (φ0 v) and partial molar isobaric expansibility (φ0 E). The viscosity data were used to evaluate A-and B-coefficients, free energy of activation of viscous flow (⊿μ0*1 ) and (⊿μ0*2 ), per mole of solvent and solute respectively, enthalpy (⊿H*) and entropy (⊿utilized in the qualitative elucidation of the Pro-surfactant/formamide and Pro-Pro interactions in the present systems.
2008, 24(06): 992-996
doi: 10.1016/S1872-1508(08)60045-5
Abstract:
Cobalt phthalocyanine (CoPc) was synthesized and self-assembled on the surface of nanoscale tin dioxide (SnO2) by in-situ process, marked as i, and Co-O interaction was verified to conjugate axially between macromolecule (CoPc) and SnO2 in CoPc/SnO2(i). The results indicated that the binding constant of CoPc/SnO2(i) was two-order higher than that of CoPc/SnO2(d) synthesized by dipping process, marked as d, while the numbers of binding sites were comparable in both samples. The degradation rate in the photocatalytic activity of CoPc/SnO2(i) was 32.5% higher than that of CoPc/SnO2(d) under visible-light irradiation for 150 min due to the effective electron separation and energy injection from LUMO of CoPc to conduction band of SnO2 for CoPc/SnO2(i) based on the strong interaction between CoPc and SnO2. The degradation recyclability of CoPc/SnO2(i) retained 48.8% in 10 times under the same circular photocatalytic process.
Cobalt phthalocyanine (CoPc) was synthesized and self-assembled on the surface of nanoscale tin dioxide (SnO2) by in-situ process, marked as i, and Co-O interaction was verified to conjugate axially between macromolecule (CoPc) and SnO2 in CoPc/SnO2(i). The results indicated that the binding constant of CoPc/SnO2(i) was two-order higher than that of CoPc/SnO2(d) synthesized by dipping process, marked as d, while the numbers of binding sites were comparable in both samples. The degradation rate in the photocatalytic activity of CoPc/SnO2(i) was 32.5% higher than that of CoPc/SnO2(d) under visible-light irradiation for 150 min due to the effective electron separation and energy injection from LUMO of CoPc to conduction band of SnO2 for CoPc/SnO2(i) based on the strong interaction between CoPc and SnO2. The degradation recyclability of CoPc/SnO2(i) retained 48.8% in 10 times under the same circular photocatalytic process.
2008, 24(06): 997-1001
doi: 10.3866/PKU.WHXB20080614
Abstract:
Thermal decomposition of hexanitrohexaazaisowurtzitane (HNIW)was studied bymass spectroscopy (MS) with low impacting electron energy. Non-isothermal kinetics treating method for ion curves in mass spectroscopy was established. The mechanism of HNIW thermal decomposition was analyzed according to the Arrhenius curves of ion products. The results showed that the apparent activation energy of the HNIW thermal decomposition was 145.1 kJ·mol-1. Between 130 and 150 ℃, ion products are mainly produced by electron impact, and activation energy is between 28 and 41 kJ·mol -1. Between 213 and 228 ℃, ion products are mainly produced by thermal decomposition, and activation energy is between 143 and 179 kJ·mol-1. The kinetic compensation effect occurs in thermal decomposition of HNIWbetween 213 and 228 ℃, and the compensation effect equation is lnA=0.252Ea-0.645. The main reactions of HNIWthermal decomposition are as HNIW.438→6NO2+2HCN+HNIW.108, HNIW.438→6NO2+3HCN+HNIW.81, HNIW.438→6NO2+4HCN+HNIW.54.
Thermal decomposition of hexanitrohexaazaisowurtzitane (HNIW)was studied bymass spectroscopy (MS) with low impacting electron energy. Non-isothermal kinetics treating method for ion curves in mass spectroscopy was established. The mechanism of HNIW thermal decomposition was analyzed according to the Arrhenius curves of ion products. The results showed that the apparent activation energy of the HNIW thermal decomposition was 145.1 kJ·mol-1. Between 130 and 150 ℃, ion products are mainly produced by electron impact, and activation energy is between 28 and 41 kJ·mol -1. Between 213 and 228 ℃, ion products are mainly produced by thermal decomposition, and activation energy is between 143 and 179 kJ·mol-1. The kinetic compensation effect occurs in thermal decomposition of HNIWbetween 213 and 228 ℃, and the compensation effect equation is lnA=0.252Ea-0.645. The main reactions of HNIWthermal decomposition are as HNIW.438→6NO2+2HCN+HNIW.108, HNIW.438→6NO2+3HCN+HNIW.81, HNIW.438→6NO2+4HCN+HNIW.54.
2008, 24(06): 1002-1006
doi: 10.3866/PKU.WHXB20080615
Abstract:
Using hydrated titanium oxide sol as raw material, porous carbon as template, a novel spinel Li4Ti5O12 was synthesized. SEM, XRD, galvanostatic charge-discharge test, and alternating current impedance test were used to characterize the appearance, structure, and electrochemical performance of the oxide. The results showed that the dimension of the crystal particle of the oxide was about 200 nm. At a 0.5C (1C=0.2 mA·cm-2) current condition, the first charge-discharge efficiency of the Li4Ti5O12 electrode was 99.8%, the lithium intercalation potential or the lithium extraction potential was quite flat, and it’s reversible capacity was 117 mAh·g-1. When the current increased from 0.5C to 5C, the reversible capacity of the oxide was still above 100 mAh·g-1, which was more than 86% of the initial capacity. The Li4Ti5O12 exhibited an excellent rate capability. A.C. impedance test proved that using porous carbon as template in synthesis process could make the spinel Li4Ti5O12 have od conductivity and obvious porous characteristic.
Using hydrated titanium oxide sol as raw material, porous carbon as template, a novel spinel Li4Ti5O12 was synthesized. SEM, XRD, galvanostatic charge-discharge test, and alternating current impedance test were used to characterize the appearance, structure, and electrochemical performance of the oxide. The results showed that the dimension of the crystal particle of the oxide was about 200 nm. At a 0.5C (1C=0.2 mA·cm-2) current condition, the first charge-discharge efficiency of the Li4Ti5O12 electrode was 99.8%, the lithium intercalation potential or the lithium extraction potential was quite flat, and it’s reversible capacity was 117 mAh·g-1. When the current increased from 0.5C to 5C, the reversible capacity of the oxide was still above 100 mAh·g-1, which was more than 86% of the initial capacity. The Li4Ti5O12 exhibited an excellent rate capability. A.C. impedance test proved that using porous carbon as template in synthesis process could make the spinel Li4Ti5O12 have od conductivity and obvious porous characteristic.
2008, 24(06): 1007-1011
doi: 10.3866/PKU.WHXB20080616
Abstract:
The white zinc aluminium oxide (ZAO) nanocrystals with excellent dispersity and electrical conductivity were efficiently synthesized by the ultrasonic-template method. The morphologies, structures of the ZAO nanocrystals andthe thermochemistry of the precursorwere researchedbyTEM,XRD, FT-IR, TG-DTA, and UV-Vis, etc. The relationships of Al2O3 addition quantity with the resistivity, UV-Vis absorption wavelength, and energy band gap of ZAO nanocrystals were also studied. The ZAO nanocrystals were added to the anlistatig-coatings system, and the obtained coating’s color was easy to be modulated, its electrical conductivity and UV-absorption were also obviously improved.
The white zinc aluminium oxide (ZAO) nanocrystals with excellent dispersity and electrical conductivity were efficiently synthesized by the ultrasonic-template method. The morphologies, structures of the ZAO nanocrystals andthe thermochemistry of the precursorwere researchedbyTEM,XRD, FT-IR, TG-DTA, and UV-Vis, etc. The relationships of Al2O3 addition quantity with the resistivity, UV-Vis absorption wavelength, and energy band gap of ZAO nanocrystals were also studied. The ZAO nanocrystals were added to the anlistatig-coatings system, and the obtained coating’s color was easy to be modulated, its electrical conductivity and UV-absorption were also obviously improved.
2008, 24(06): 1012-1016
doi: 10.3866/PKU.WHXB20080617
Abstract:
Polymer doped organic light-emitting diodes (OLEDs) with the structure of indium-tin oxide (ITO)/poly(N-vinylcarbazole) (PVK):(pbi)2Ir(acac)/2,9-dimethyl-4,7-diphenyl-1,10-phenan throline (BCP)/Mg:Ag were fabricated. The light-emitting layer was processed by doping noble metal iridiumcomplex (pbi)2Ir(acac) into a PVKmatrix with the concentrations of 4%and 5%(w), using spin coating method. Through characterizing the UV-Vis absorption spectrum, photoluminescence (PL) spectrum of the (pbi)2Ir(acac) and the electroluminescence (EL) properties of the devices, the main energy transfer mechanisms from phosphorescent material (pbi)2Ir(acac) to PVK were discussed. The device performance was investigated at different current densities and doping concentrations. The results showed that the devices with above two different doping concentrations have the maximum brightness of 11210 and 9174 cd·m-2 and maximum luminance efficiency of 1.53 and 1.31 lm·W-1, respectively. The EL spectrum and the Commissions Internationale de 1’Eclairage (CIE) coordinates were independent on the variation of bias voltage and the doping concentration, indicating a stable color purity.
Polymer doped organic light-emitting diodes (OLEDs) with the structure of indium-tin oxide (ITO)/poly(N-vinylcarbazole) (PVK):(pbi)2Ir(acac)/2,9-dimethyl-4,7-diphenyl-1,10-phenan throline (BCP)/Mg:Ag were fabricated. The light-emitting layer was processed by doping noble metal iridiumcomplex (pbi)2Ir(acac) into a PVKmatrix with the concentrations of 4%and 5%(w), using spin coating method. Through characterizing the UV-Vis absorption spectrum, photoluminescence (PL) spectrum of the (pbi)2Ir(acac) and the electroluminescence (EL) properties of the devices, the main energy transfer mechanisms from phosphorescent material (pbi)2Ir(acac) to PVK were discussed. The device performance was investigated at different current densities and doping concentrations. The results showed that the devices with above two different doping concentrations have the maximum brightness of 11210 and 9174 cd·m-2 and maximum luminance efficiency of 1.53 and 1.31 lm·W-1, respectively. The EL spectrum and the Commissions Internationale de 1’Eclairage (CIE) coordinates were independent on the variation of bias voltage and the doping concentration, indicating a stable color purity.
2008, 24(06): 1017-1022
doi: 10.3866/PKU.WHXB20080618
Abstract:
Porous silicon (PS) was formed on the surface of silicon wafer by electrochemical etching method under different current densities. In order to form VOx/PS/Si structure, vanadium oxide thin films were deposited on PS surface utilizing novel facing targets DC reactive sputtering technique. Field emission scanning electron microscope (FESEM) was utilized to observe the microstructure of PS and VOx/PS/Si structure, the nano-mechanical property of VOx/PS/Si structure was studied by nanoindentor instrument, and the temperature sensitive property was analyzed with resistance-power curves. The results showed that the average pore sizes of PS samples prepared under current densities of 40 and 80 mA·cm-2 were 18 and 24 nm, and the thermal conductivities tested by micro Raman spectroscopy were 3.282 and 1.278 kW·K-1, respectively. The average speeds of resistance varying with power for VOx/PS/Si structure were 60×109 and 100×109 Ω·W-1, and the nano-hardness were 1.917 and 0.928 GPa, respectively. The experimental results indicated that the microstructure of PS had great influence on the nano-mechanical property and temperature sensitivity of VOx/PS/Si structure; this structure formed on PS with high porosity had better temperature sensitivity than PS with low porosity, but a worse mechanical stability.
Porous silicon (PS) was formed on the surface of silicon wafer by electrochemical etching method under different current densities. In order to form VOx/PS/Si structure, vanadium oxide thin films were deposited on PS surface utilizing novel facing targets DC reactive sputtering technique. Field emission scanning electron microscope (FESEM) was utilized to observe the microstructure of PS and VOx/PS/Si structure, the nano-mechanical property of VOx/PS/Si structure was studied by nanoindentor instrument, and the temperature sensitive property was analyzed with resistance-power curves. The results showed that the average pore sizes of PS samples prepared under current densities of 40 and 80 mA·cm-2 were 18 and 24 nm, and the thermal conductivities tested by micro Raman spectroscopy were 3.282 and 1.278 kW·K-1, respectively. The average speeds of resistance varying with power for VOx/PS/Si structure were 60×109 and 100×109 Ω·W-1, and the nano-hardness were 1.917 and 0.928 GPa, respectively. The experimental results indicated that the microstructure of PS had great influence on the nano-mechanical property and temperature sensitivity of VOx/PS/Si structure; this structure formed on PS with high porosity had better temperature sensitivity than PS with low porosity, but a worse mechanical stability.
2008, 24(06): 1023-1029
doi: 10.3866/PKU.WHXB20080619
Abstract:
Using Ce0.5Ti0.5O2 as carrier, CuO/Ce0.5Ti0.5O2 catalysts with different CuO loadings were prepared by the impregnation method. The catalytic activities of the catalysts for NO+CO reaction were examined with a micro-reactor gas chromatography reaction system and the catalysts were characterized by of TPR, XRD, and Raman spectroscopy. It was found that the activity of CuO/Ce0.5Ti0.5O2 for NO+CO reaction was depended on CuO loading, and became maximal when CuO loading was 22% and the calcined temperature was 500 ℃. However, after calcination at 700 ℃ 14%CuO/Ce0.5Ti0.5O2 had the highest activity, possibly due to the formation of CeTi2O6-mixed oxide. The TPR analysis showed that CuO/Ce0.5Ti0.5O2 had four TPRreduction peaks (α, β, γ, and δ peaks). The α and β peaks were the reduction of highly dispersed CuO species; the γpeak was due to the isolated bulk CuO interacted intensively with Ce0.5Ti0.5O2; and the δ peak was due to the bulk CuO on the surface of CuO/Ce0.5Ti0.5O2. As shown by XRD, CuO/Ce0.5Ti0.5O2 calcined at 700 ℃ had new oxide CeTi2O6, and the diffraction peaks of CeTi2O6 became obvious as the calcined temperature increased, indicating that high temperature enhanced solid reaction of Ce and Ti, and formation of CeTi2O6. The Raman results indicated that after calcination Ce0.5Ti0.5O2 was no longer a simple combination of TiO2 and CeO2, but had formed new crystal structure.
Using Ce0.5Ti0.5O2 as carrier, CuO/Ce0.5Ti0.5O2 catalysts with different CuO loadings were prepared by the impregnation method. The catalytic activities of the catalysts for NO+CO reaction were examined with a micro-reactor gas chromatography reaction system and the catalysts were characterized by of TPR, XRD, and Raman spectroscopy. It was found that the activity of CuO/Ce0.5Ti0.5O2 for NO+CO reaction was depended on CuO loading, and became maximal when CuO loading was 22% and the calcined temperature was 500 ℃. However, after calcination at 700 ℃ 14%CuO/Ce0.5Ti0.5O2 had the highest activity, possibly due to the formation of CeTi2O6-mixed oxide. The TPR analysis showed that CuO/Ce0.5Ti0.5O2 had four TPRreduction peaks (α, β, γ, and δ peaks). The α and β peaks were the reduction of highly dispersed CuO species; the γpeak was due to the isolated bulk CuO interacted intensively with Ce0.5Ti0.5O2; and the δ peak was due to the bulk CuO on the surface of CuO/Ce0.5Ti0.5O2. As shown by XRD, CuO/Ce0.5Ti0.5O2 calcined at 700 ℃ had new oxide CeTi2O6, and the diffraction peaks of CeTi2O6 became obvious as the calcined temperature increased, indicating that high temperature enhanced solid reaction of Ce and Ti, and formation of CeTi2O6. The Raman results indicated that after calcination Ce0.5Ti0.5O2 was no longer a simple combination of TiO2 and CeO2, but had formed new crystal structure.
2008, 24(06): 1030-1034
doi: 10.3866/PKU.WHXB20080620
Abstract:
Nanocrystals with different Eu3+ doping levels were prepared by sol-gel and hydrothermal synthetic methods using titanium tetraisopropoxide (TTIP) as titanium source. The crystallite size, crystal form, surface shape, composition and optical property of the nanocrystals were characterized by X-ray diffraction patterns, UV-Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma atomic emission spectroscopy. The products exhibited anatase phase structure, with an average size of 9 nm, and Eu3+ entered into the crystal cell of TiO2 (interstitial mode) in the form of Eu2O3. Furthermore, the photocatalytic activity of prepared Eu3+ doped TiO2 was studied by degrading partially hydrolyzed polyacrylamide (HPAM) under UV light irradiation. The results showed that HPAM was completely degraded. Ultimate mineralization ratio reached 67% when Eu3+ loading was 2.4% (w). In addition, intermediate products were detected via liquid chromatography/mass spectrometry, and degradation mechanismwas analyzed.
Nanocrystals with different Eu3+ doping levels were prepared by sol-gel and hydrothermal synthetic methods using titanium tetraisopropoxide (TTIP) as titanium source. The crystallite size, crystal form, surface shape, composition and optical property of the nanocrystals were characterized by X-ray diffraction patterns, UV-Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma atomic emission spectroscopy. The products exhibited anatase phase structure, with an average size of 9 nm, and Eu3+ entered into the crystal cell of TiO2 (interstitial mode) in the form of Eu2O3. Furthermore, the photocatalytic activity of prepared Eu3+ doped TiO2 was studied by degrading partially hydrolyzed polyacrylamide (HPAM) under UV light irradiation. The results showed that HPAM was completely degraded. Ultimate mineralization ratio reached 67% when Eu3+ loading was 2.4% (w). In addition, intermediate products were detected via liquid chromatography/mass spectrometry, and degradation mechanismwas analyzed.
Molecular Dynamics Simulation of Microperoxidase in Aqueous Solution in Terms of the ABEEM/MM Method
2008, 24(06): 1035-1040
doi: 10.3866/PKU.WHXB20080621
Abstract:
In terms of the atom-bond electronegativity equilization fluctuating charge molecularmechanics(ABEEM/MM), molecular dynamics simulation on aqueous microperoxidases (MP) was performed. The impact of water molecules on the structure of MP, the ruffling conformation of the heme, and the orientation of the axially ligated imidazole were investigated. Results show that, in the aqueous solution, the backbone amino acids of the MP are stable, while the ruffling conformation of heme turns to be planar, which comes from the interaction between water and MP. The orientation of the axially coordinated imidazole is mainly determined by the histidine bonded with the imidazole, while the electrostatic force between the imidazole and the side-chained propionic acid group of the heme is only a subsidiary factor.
In terms of the atom-bond electronegativity equilization fluctuating charge molecularmechanics(ABEEM/MM), molecular dynamics simulation on aqueous microperoxidases (MP) was performed. The impact of water molecules on the structure of MP, the ruffling conformation of the heme, and the orientation of the axially ligated imidazole were investigated. Results show that, in the aqueous solution, the backbone amino acids of the MP are stable, while the ruffling conformation of heme turns to be planar, which comes from the interaction between water and MP. The orientation of the axially coordinated imidazole is mainly determined by the histidine bonded with the imidazole, while the electrostatic force between the imidazole and the side-chained propionic acid group of the heme is only a subsidiary factor.
2008, 24(06): 1041-1046
doi: 10.3866/PKU.WHXB20080622
Abstract:
SA-CS/PVA bipolar membrane was prepared by sodium alginate (SA) and chitosan (CS), which were
modified by glutaraldehyde and Fe3+ as linking reagents, respectively, then blended with PVA. SA-CS/PVA membrane was characterized by IR, I-V curves, ion exchange capacity, changes of pH in anode and cathode chambers, and SEM. IR and contact angle analysis results showed that the hydrophilic property of CS improved after modified by glutaraldehyde and PVA. Using SA-CS/PVA and Nafion membrane in electroxidation to prepare 3-methyl-2-formylaminopyridine. The experiment results showed that the yield of 3-methyl-2-formylaminopyridine prepared using SA-CS/PVAmembrane was 49.8%, which was higher than that using Nafion membrane. To compare with the traditional method, the condition of electroxidation was moderate and the pollution to environment was reduced.
SA-CS/PVA bipolar membrane was prepared by sodium alginate (SA) and chitosan (CS), which were
modified by glutaraldehyde and Fe3+ as linking reagents, respectively, then blended with PVA. SA-CS/PVA membrane was characterized by IR, I-V curves, ion exchange capacity, changes of pH in anode and cathode chambers, and SEM. IR and contact angle analysis results showed that the hydrophilic property of CS improved after modified by glutaraldehyde and PVA. Using SA-CS/PVA and Nafion membrane in electroxidation to prepare 3-methyl-2-formylaminopyridine. The experiment results showed that the yield of 3-methyl-2-formylaminopyridine prepared using SA-CS/PVAmembrane was 49.8%, which was higher than that using Nafion membrane. To compare with the traditional method, the condition of electroxidation was moderate and the pollution to environment was reduced.
2008, 24(06): 1047-1052
doi: 10.3866/PKU.WHXB20080623
Abstract:
Eleven stable adenine-Zn2+ isomers in aqueous phase were investigated at B3LYP/6-311++G** level in combination with the PCMand Onsager models. Different from those in gas phase, the stabilization ordering of these adenine-Zn2+ isomers in the aqueous phase changed and the binding sites of Zn2+ showed obvious regularity. In the adenine-Zn2+ isomerswith imine group, the complexeswith the combination between Zn2+ and (N7 andN6 ) sitesweremore stable than those with the combination between the Zn2+ and (N1 and N6) sites. In those isomers with amido groups, the preferred ordering of double nitrogen sites for Zn2+ combination was (N3 and N9)>(N7 and N6)>(N1 and N6). Activation energy calculations indicated that the intramolecular proton transfer (i.e., (N6)Ha→Ha(N1) in a9=>a9→a19l) was difficult for an isolated adenine (a9). Moreover, Zn2+ could hardly induce the decrease of activation energy of intramolecular proton transfer both in the gas and aqueous phases, whereas the Cu2+ could and the effect was obvious.
Eleven stable adenine-Zn2+ isomers in aqueous phase were investigated at B3LYP/6-311++G** level in combination with the PCMand Onsager models. Different from those in gas phase, the stabilization ordering of these adenine-Zn2+ isomers in the aqueous phase changed and the binding sites of Zn2+ showed obvious regularity. In the adenine-Zn2+ isomerswith imine group, the complexeswith the combination between Zn2+ and (N7 andN6 ) sitesweremore stable than those with the combination between the Zn2+ and (N1 and N6) sites. In those isomers with amido groups, the preferred ordering of double nitrogen sites for Zn2+ combination was (N3 and N9)>(N7 and N6)>(N1 and N6). Activation energy calculations indicated that the intramolecular proton transfer (i.e., (N6)Ha→Ha(N1) in a9=>a9→a19l) was difficult for an isolated adenine (a9). Moreover, Zn2+ could hardly induce the decrease of activation energy of intramolecular proton transfer both in the gas and aqueous phases, whereas the Cu2+ could and the effect was obvious.
2008, 24(06): 1053-1057
doi: 10.3866/PKU.WHXB20080624
Abstract:
The six-parameter QSFR (quantitative structure-bioconcentration factor relationship) model of the bioconcentration factor (FBC) was constructed based on valence connectivity index (xi), electrotopological state index (ej), andmolecular electronegativitydistance vector (mk), for 239organic pollutants. The traditional correlation coefficient (R2) and the cross-validation correlation coefficient (Q2) were 0.821 and 0.809, respectively. The result demonstrated that the model was highly reliable and had od predictive ability from the point of view of statistics. From the six parameters of the model, it was known that the dominant influencing factors of bioconcentration factor were the molecular structure fragments: —C—, >C—, —O—, —X, —NH2, and the space factors: the flexibility and the puckered degree of organic pollutant molecules. It may be considered that the induced fit mechanism plays a definite action in the process of biological enrichment. The ortho nal transformation of independent variable did not influence the correlativity of model and could reduce the autocorrelation of independent variable.
The six-parameter QSFR (quantitative structure-bioconcentration factor relationship) model of the bioconcentration factor (FBC) was constructed based on valence connectivity index (xi), electrotopological state index (ej), andmolecular electronegativitydistance vector (mk), for 239organic pollutants. The traditional correlation coefficient (R2) and the cross-validation correlation coefficient (Q2) were 0.821 and 0.809, respectively. The result demonstrated that the model was highly reliable and had od predictive ability from the point of view of statistics. From the six parameters of the model, it was known that the dominant influencing factors of bioconcentration factor were the molecular structure fragments: —C—, >C—, —O—, —X, —NH2, and the space factors: the flexibility and the puckered degree of organic pollutant molecules. It may be considered that the induced fit mechanism plays a definite action in the process of biological enrichment. The ortho nal transformation of independent variable did not influence the correlativity of model and could reduce the autocorrelation of independent variable.
2008, 24(06): 1058-1062
doi: 10.3866/PKU.WHXB20080625
Abstract:
1H, 13C, DEPT, 1H-1H COSY NMR and HSQC NMR spectra of (s)-doxazosin were reported. All the 1H and 13CNMRdata were assigned. There were 9 quaternaryCatoms in the (s)-doxazosin molecule, and most of them were difficult to be identified only by experimental data. 13C NMR chemical shifts of (s)-doxazosin were calculated by means of the Hartree-Fock (HF) and Becke-3-Lee-Yang-Parr (B3LYP) density functional theory methods with 6-21G basis sets respectively. Comparison between the experimental and the theoretical results indicated that both methods had od correlation. This was helpful to assign the NMR shifts of quaternary C atoms.
1H, 13C, DEPT, 1H-1H COSY NMR and HSQC NMR spectra of (s)-doxazosin were reported. All the 1H and 13CNMRdata were assigned. There were 9 quaternaryCatoms in the (s)-doxazosin molecule, and most of them were difficult to be identified only by experimental data. 13C NMR chemical shifts of (s)-doxazosin were calculated by means of the Hartree-Fock (HF) and Becke-3-Lee-Yang-Parr (B3LYP) density functional theory methods with 6-21G basis sets respectively. Comparison between the experimental and the theoretical results indicated that both methods had od correlation. This was helpful to assign the NMR shifts of quaternary C atoms.
2008, 24(06): 1063-1067
doi: 10.3866/PKU.WHXB20080626
Abstract:
In order to promote the energy output of microbial fuel cell (MFC), reduce the internal resistance of MFC and the cost of processing organics, a direct-air cathode single-chamber microbial fuel cell was constructed by using air electrode as cathode, foamed nickel (ferrumiron) as anode and glucose as the anode fed. The results demonstrated that the open circuit voltage reached 0.62 V, the internal resistance of the cell was 33.8 Ω, the maximum power density reached 700 mW·m-2 (4146 mW·m-3), and the electron recovery was 20%. The discharge curve and cyclic voltammetry tests revealed that the first discharge capacity and energy density were 263 mAh·g-1 COD (chemical oxygen demand) and 77.3 mWh·g-1 COD, respectively. The charge-discharge performance and stability of MFC were pretty od. The electrochemical impedance spectroscopy analysis demonstrated that the cell impedance increased with the increase of discharge time, which was one of the reasons resulting in the decrease of output voltage. The degradation rate of COD (chemical oxygen demand) reached 56.5% after it operating for 8 h. The degradation of COD followed the first order reaction model.
In order to promote the energy output of microbial fuel cell (MFC), reduce the internal resistance of MFC and the cost of processing organics, a direct-air cathode single-chamber microbial fuel cell was constructed by using air electrode as cathode, foamed nickel (ferrumiron) as anode and glucose as the anode fed. The results demonstrated that the open circuit voltage reached 0.62 V, the internal resistance of the cell was 33.8 Ω, the maximum power density reached 700 mW·m-2 (4146 mW·m-3), and the electron recovery was 20%. The discharge curve and cyclic voltammetry tests revealed that the first discharge capacity and energy density were 263 mAh·g-1 COD (chemical oxygen demand) and 77.3 mWh·g-1 COD, respectively. The charge-discharge performance and stability of MFC were pretty od. The electrochemical impedance spectroscopy analysis demonstrated that the cell impedance increased with the increase of discharge time, which was one of the reasons resulting in the decrease of output voltage. The degradation rate of COD (chemical oxygen demand) reached 56.5% after it operating for 8 h. The degradation of COD followed the first order reaction model.
Interaction of 1,4,8,9-Tetraazatriphenylene-Copper (II)-L-Serinate (L-Argininate) Complexes with DNA
2008, 24(06): 1068-1072
doi: 10.3866/PKU.WHXB20080627
Abstract:
Interactions of ternary Cu(II) complexes [Cu(TATP)(L-Ser)(H2O)]·ClO4(1) and [Cu(TATP)(L-Arg) (H2O)]2ClO4·0.5H2O (2) (TATP=1,4,8,9-tetraazatriphenylene, L-Ser=L-serinate, L-Arg=L-argininate) with DNA have been investigated by electronic absorption spectroscopy, fluorescence spectroscopy, viscosity, and gel electrophoresis measurements. The intensity of maximal absorption peaks of absorption spectra of the complexes was weakened with the increase in DNA concentration, and the complexes could remarkably quench the emission intensity of ethidium bromide (EB)-DNA system. At the same time, the viscosity of DNA decreased with the increase in the concentration of the complexes. The results indicated that the intercalative interaction of the complexes with DNA was strong and gave the order of the binding abilities of the complexes to DNA: complex 2>1. Moreover, the result of agarose gel electrophoresis showed that the complexes had high cleaving efficiency to pBR322 DNA in the presence of vitamin C.
Interactions of ternary Cu(II) complexes [Cu(TATP)(L-Ser)(H2O)]·ClO4(1) and [Cu(TATP)(L-Arg) (H2O)]2ClO4·0.5H2O (2) (TATP=1,4,8,9-tetraazatriphenylene, L-Ser=L-serinate, L-Arg=L-argininate) with DNA have been investigated by electronic absorption spectroscopy, fluorescence spectroscopy, viscosity, and gel electrophoresis measurements. The intensity of maximal absorption peaks of absorption spectra of the complexes was weakened with the increase in DNA concentration, and the complexes could remarkably quench the emission intensity of ethidium bromide (EB)-DNA system. At the same time, the viscosity of DNA decreased with the increase in the concentration of the complexes. The results indicated that the intercalative interaction of the complexes with DNA was strong and gave the order of the binding abilities of the complexes to DNA: complex 2>1. Moreover, the result of agarose gel electrophoresis showed that the complexes had high cleaving efficiency to pBR322 DNA in the presence of vitamin C.
2008, 24(06): 1073-1079
doi: 10.3866/PKU.WHXB20080628
Abstract:
One-step electrodeposition(ED) of Cu(In1-x, Gax)Se2 (CIGS) thin films on Mo/glass substrates from aqueous solutions containing CuCl2, InCl3, GaCl3, and H2SeO3 was studied. In order to stabilize the solutions, they were buffered using a potassium biphthalate/sulfamic acid mixture giving a bath of pH 2.5. The type of the solutions would influence Ga concentration in the CIGS films. In general, CIGS thin film is called stoichiometric compound when the molar ratio of Cu to In+Ga is 1, and when the ratio is in the range of 0.8-1, it is called near stoichiometric and slightly Cu-poor or In-rich CIGS compound. As-deposited films were near stoichiometric and slightly Cu-poor CIGS precursors with smooth, compact, crack-free surface by the optimization of the solution composition and the deposition condition. The electrodeposition mechanisms of CIGS on Mo substrates were studied by cyclic voltammetry. The results showed that Se4+ was first reduced to Se, and then Cu2+, In3 +, and Ga3+ were deposited via the induced co- deposition mechanism at more positive potentials than they were reduced. As-deposited films were selenized and recrystallized at 550 ℃ in Se vapor with a Se source temperature of 280 ℃, which improved crystal structure of the films and changed little the compositions of ED-CIGS thin films, but resulted in cracking of the films.
One-step electrodeposition(ED) of Cu(In1-x, Gax)Se2 (CIGS) thin films on Mo/glass substrates from aqueous solutions containing CuCl2, InCl3, GaCl3, and H2SeO3 was studied. In order to stabilize the solutions, they were buffered using a potassium biphthalate/sulfamic acid mixture giving a bath of pH 2.5. The type of the solutions would influence Ga concentration in the CIGS films. In general, CIGS thin film is called stoichiometric compound when the molar ratio of Cu to In+Ga is 1, and when the ratio is in the range of 0.8-1, it is called near stoichiometric and slightly Cu-poor or In-rich CIGS compound. As-deposited films were near stoichiometric and slightly Cu-poor CIGS precursors with smooth, compact, crack-free surface by the optimization of the solution composition and the deposition condition. The electrodeposition mechanisms of CIGS on Mo substrates were studied by cyclic voltammetry. The results showed that Se4+ was first reduced to Se, and then Cu2+, In3 +, and Ga3+ were deposited via the induced co- deposition mechanism at more positive potentials than they were reduced. As-deposited films were selenized and recrystallized at 550 ℃ in Se vapor with a Se source temperature of 280 ℃, which improved crystal structure of the films and changed little the compositions of ED-CIGS thin films, but resulted in cracking of the films.
2008, 24(06): 1080-1084
doi: 10.3866/PKU.WHXB20080629
Abstract:
ZnO nanowires with (002) oriented direction was synthesized via modified CVD method. Bottom-up assembly including photolithography/lift off was employed to fabricate gas sensor based on single ZnO nanwire with 50-300 nm in diameter and 2-10 μm in length. The as-prepared device showed gas sensitivities of 1.3 and 1.2 to oxygen and ethanol gases with concentration of 500 μL·L-1 at room temperature, and the corresponding temporal responses were 10 and 5 s, respectively. The improved gas sensing properties were attributed to the enhancement of the current-induced heating on the quasi-one-dimensional nanostructure.
ZnO nanowires with (002) oriented direction was synthesized via modified CVD method. Bottom-up assembly including photolithography/lift off was employed to fabricate gas sensor based on single ZnO nanwire with 50-300 nm in diameter and 2-10 μm in length. The as-prepared device showed gas sensitivities of 1.3 and 1.2 to oxygen and ethanol gases with concentration of 500 μL·L-1 at room temperature, and the corresponding temporal responses were 10 and 5 s, respectively. The improved gas sensing properties were attributed to the enhancement of the current-induced heating on the quasi-one-dimensional nanostructure.
2008, 24(06): 1085-1089
doi: 10.3866/PKU.WHXB20080630
Abstract:
CuCo/ZrO2 catalysts for lower-alcohol synthesis from syngas were prepared by glow discharge plasma and conventional calcination method. The effects of plasma atmosphere(N2, H2 or first N2 then H2) on the catalyst structure and performance were investigated. These catalysts were characterized using BET, XPS, XRD, TG, and TPR techniques. The experimental results indicated that plasma treatment restrained effectively the production of hydrocarbon and enhanced the selectivity to total alcohols. Compared with the calcined sample, the plasma treated catalyst had higher activity and space time yield (STY). Characterization results showed that the catalyst precursor with plasma treatment was decomposed to active phase under low temperature and the specific surface area of catalyst was significantly improved. Meanwhile, the plasma treatment promoted the grain refining, dispersion of the active component and enrichment of copper on the catalyst surface.
CuCo/ZrO2 catalysts for lower-alcohol synthesis from syngas were prepared by glow discharge plasma and conventional calcination method. The effects of plasma atmosphere(N2, H2 or first N2 then H2) on the catalyst structure and performance were investigated. These catalysts were characterized using BET, XPS, XRD, TG, and TPR techniques. The experimental results indicated that plasma treatment restrained effectively the production of hydrocarbon and enhanced the selectivity to total alcohols. Compared with the calcined sample, the plasma treated catalyst had higher activity and space time yield (STY). Characterization results showed that the catalyst precursor with plasma treatment was decomposed to active phase under low temperature and the specific surface area of catalyst was significantly improved. Meanwhile, the plasma treatment promoted the grain refining, dispersion of the active component and enrichment of copper on the catalyst surface.
2008, 24(06): 1090-1094
doi: 10.3866/PKU.WHXB20080631
Abstract:
A method used for the study of thermal decomposition kinetics by peak analysis was developed. This method needs only a few eigenvalues of the thermogravimetric mass loss curves for the determination of kinetic parameters. A peak separation was performed to separate the thermal decomposition of phenolic resin into three stages according to the characteristic of the experimental differential mass loss curve. Kinetic parameters for each stage were determined using peak analysis method. A decomposition kinetic model, which was shown to accurately describe the decomposition process of phenolic resin, was obtained by the combination of these three stages.
A method used for the study of thermal decomposition kinetics by peak analysis was developed. This method needs only a few eigenvalues of the thermogravimetric mass loss curves for the determination of kinetic parameters. A peak separation was performed to separate the thermal decomposition of phenolic resin into three stages according to the characteristic of the experimental differential mass loss curve. Kinetic parameters for each stage were determined using peak analysis method. A decomposition kinetic model, which was shown to accurately describe the decomposition process of phenolic resin, was obtained by the combination of these three stages.
2008, 24(06): 1095-1099
doi: 10.3866/PKU.WHXB20080632
Abstract:
Sol-gel process was employed to prepare TiO2 and nickle-modified TiO2 powders. Photodegradation of 4-chlorophenol was employed to evaluate the photocatalytic activities of the catalysts. Compared to TiO2, nickle-modified TiO2 exhibited improved activity for degradation of 4-chlorophenol under both ultraviolet and visible light irradiations. The properties of these catalysts were investigated with X-ray diffraction (XRD), diffuse reflectance UV-Vis spectra, infrared spectra (IR), Raman spectra, and surface photovoltage spectroscopy (SPS). We found that Ni2+ was chemisorbed on the surface of TiO2 and formed ONiOO, which introduced the energy level of surface states 2.84 eV above the valence band. This energy level not only generated response to visible light but also promoted the separation of photogenerated carriers. Thus, the activity under ultraviolet and visible light irradiations was increased.
Sol-gel process was employed to prepare TiO2 and nickle-modified TiO2 powders. Photodegradation of 4-chlorophenol was employed to evaluate the photocatalytic activities of the catalysts. Compared to TiO2, nickle-modified TiO2 exhibited improved activity for degradation of 4-chlorophenol under both ultraviolet and visible light irradiations. The properties of these catalysts were investigated with X-ray diffraction (XRD), diffuse reflectance UV-Vis spectra, infrared spectra (IR), Raman spectra, and surface photovoltage spectroscopy (SPS). We found that Ni2+ was chemisorbed on the surface of TiO2 and formed ONiOO, which introduced the energy level of surface states 2.84 eV above the valence band. This energy level not only generated response to visible light but also promoted the separation of photogenerated carriers. Thus, the activity under ultraviolet and visible light irradiations was increased.
2008, 24(06): 1100-1104
doi: 10.3866/PKU.WHXB20080633
Abstract:
The thermal degradation behaviors of fluoroelastomer and the blends of fluoroelastomer/MEPDM were investigated by thermogravimetry (TG) and derivative thermogravimetry (DTG). The kinetic parameters were evaluated by differential method and integral method. The results showed that the fluoroelastomer/MEPDM blends had higher thermal degradation temperature, but smaller apparent activation energy E than FPM, the E values were 251.74, 244.98, and 219.60 kJ·mol-1 for FPM, FPM/MEPDM(5%), and FPM/MEPDM(10%), respectively. The thermal decomposition reaction order was 0.95 for both FPM and FPM/MEPDM blends. The thermal decomposition apparent activation energy E increased with increasing mass fraction loss α. The TG and DTG results suggested that the FPM/MEPDM blends had excellent thermalstability. The kinetic data indicated that the FPM/MEPDM blends decomposed easily than FPMafter onset degradation temperature.
The thermal degradation behaviors of fluoroelastomer and the blends of fluoroelastomer/MEPDM were investigated by thermogravimetry (TG) and derivative thermogravimetry (DTG). The kinetic parameters were evaluated by differential method and integral method. The results showed that the fluoroelastomer/MEPDM blends had higher thermal degradation temperature, but smaller apparent activation energy E than FPM, the E values were 251.74, 244.98, and 219.60 kJ·mol-1 for FPM, FPM/MEPDM(5%), and FPM/MEPDM(10%), respectively. The thermal decomposition reaction order was 0.95 for both FPM and FPM/MEPDM blends. The thermal decomposition apparent activation energy E increased with increasing mass fraction loss α. The TG and DTG results suggested that the FPM/MEPDM blends had excellent thermalstability. The kinetic data indicated that the FPM/MEPDM blends decomposed easily than FPMafter onset degradation temperature.
2008, 24(06): 1105-1110
doi: 10.3866/PKU.WHXB20080634
Abstract:
Uniform dandelion-like, sisal-like and bindle-like architectures of compounds were successfully prepared in water/hexadecyltrimethyl ammonium bromide (CTAB)/hexane/n-pentanol quaternary microemulsion under hydrothermal conditions at 100 ℃, and morphologies of the three pyrolysis products at 300 ℃ were similar to those of their corresponding precursors. X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that as-synthesized Co3O4 possessed cubic spinel-type structure. The hydrothermal time played an important role in the morphologies of the materials. Electrochemical capacitance properties of the prepared Co3O4were investigated by means of cyclic voltammetry and galvanostatic charge/discharge measurements. When the hydrothermal time increased to 6 h, the obtained Co3O4 had the excellent electrochemical capacitance with the highest capacitance of 340 F·g-1.
Uniform dandelion-like, sisal-like and bindle-like architectures of compounds were successfully prepared in water/hexadecyltrimethyl ammonium bromide (CTAB)/hexane/n-pentanol quaternary microemulsion under hydrothermal conditions at 100 ℃, and morphologies of the three pyrolysis products at 300 ℃ were similar to those of their corresponding precursors. X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that as-synthesized Co3O4 possessed cubic spinel-type structure. The hydrothermal time played an important role in the morphologies of the materials. Electrochemical capacitance properties of the prepared Co3O4were investigated by means of cyclic voltammetry and galvanostatic charge/discharge measurements. When the hydrothermal time increased to 6 h, the obtained Co3O4 had the excellent electrochemical capacitance with the highest capacitance of 340 F·g-1.
2008, 24(06): 1111-1114
doi: 10.3866/PKU.WHXB20080635
Abstract:
This paper presents the application of a novel conductance detector together with a self-made conductance probe, for studying the homogeneous nucleation of Al(OH)3 from supersaturated sodium aluminate solution under isothermal, batch crystallization conditions. The effects of supersaturation on indication period were examined. The nucleation kinetics showed a (4±1)-order dependence upon Al2O3 relative supersaturation and an interfacial energy of (40.6±2.0) mJ·m-2, which were used to predict the critical nucleus size of (1.1±0.2) nm at 323 K, S>3.8. These results were consistent with those in literatures, indicating the satisfactory reliability and sensitivity of the apparatus.
This paper presents the application of a novel conductance detector together with a self-made conductance probe, for studying the homogeneous nucleation of Al(OH)3 from supersaturated sodium aluminate solution under isothermal, batch crystallization conditions. The effects of supersaturation on indication period were examined. The nucleation kinetics showed a (4±1)-order dependence upon Al2O3 relative supersaturation and an interfacial energy of (40.6±2.0) mJ·m-2, which were used to predict the critical nucleus size of (1.1±0.2) nm at 323 K, S>3.8. These results were consistent with those in literatures, indicating the satisfactory reliability and sensitivity of the apparatus.
2008, 24(06): 1115-1119
doi: 10.3866/PKU.WHXB20080636
Abstract:
Novel size-tunable alumina hollow spheres were successfully prepared using colloidal carbon spheres as templates and aluminum nitrate as alumina source. The samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD). The influences of the synthesis conditions such as reaction time, reaction temperature, and the concentration of Al(NO3)3 were studied. According to the experiment, the synthesized alumina hollow spheres with a narrow size distribution showed tunable shell thickness and uniform shell. The morphology of the alumina hollow spheres was influenced mainly by the reaction temperature.
Novel size-tunable alumina hollow spheres were successfully prepared using colloidal carbon spheres as templates and aluminum nitrate as alumina source. The samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD). The influences of the synthesis conditions such as reaction time, reaction temperature, and the concentration of Al(NO3)3 were studied. According to the experiment, the synthesized alumina hollow spheres with a narrow size distribution showed tunable shell thickness and uniform shell. The morphology of the alumina hollow spheres was influenced mainly by the reaction temperature.
2008, 24(06): 1120-1126
doi: 10.3866/PKU.WHXB20080637
Abstract:
A highly ordered TiO2 nanotube layer was fabricated on fluorine-doped tin oxide-coated glass substrate (FTO) by potentiostatic anodization of pure titanium film at room temperature, which was deposited by radio frequency (RF) magnetron sputtering. The structure and the composition of the as prepared TiO2 nanotubes were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), UV-Vis transmission spectra, and photoelectrochemistry methods. The results showed that the Ti films converted to TiO2 nanotubes of 380 nm length, 90 nm pore diameter, and 15 nm wall thickness at the voltage of 20 V for 50 min. After annealing at 500 ℃ for 6 h in air, the anatase phase of TiO2 nanotube/FTO transparent electrodes were obtained, which had an average transmittance of 80% in visible wavelength range. The bandgap of TiO2 was determined as 3.28 eV, with a bandgap tail extending to 2.6 eV. Moreover, the photoelectrochemistry measurements indicated that the crystallized electrode exhibited a significant improvement of photoelectrochemical current response in comparison with the as-anodized electrode, and both the electrode potential and UV-illumination surely enhanced the effective separation of the electron-hole pairs, leading to the fact that the photo-induced electrons transferred quickly to the conducting glass via external circuit and formed photocurrent.
A highly ordered TiO2 nanotube layer was fabricated on fluorine-doped tin oxide-coated glass substrate (FTO) by potentiostatic anodization of pure titanium film at room temperature, which was deposited by radio frequency (RF) magnetron sputtering. The structure and the composition of the as prepared TiO2 nanotubes were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), UV-Vis transmission spectra, and photoelectrochemistry methods. The results showed that the Ti films converted to TiO2 nanotubes of 380 nm length, 90 nm pore diameter, and 15 nm wall thickness at the voltage of 20 V for 50 min. After annealing at 500 ℃ for 6 h in air, the anatase phase of TiO2 nanotube/FTO transparent electrodes were obtained, which had an average transmittance of 80% in visible wavelength range. The bandgap of TiO2 was determined as 3.28 eV, with a bandgap tail extending to 2.6 eV. Moreover, the photoelectrochemistry measurements indicated that the crystallized electrode exhibited a significant improvement of photoelectrochemical current response in comparison with the as-anodized electrode, and both the electrode potential and UV-illumination surely enhanced the effective separation of the electron-hole pairs, leading to the fact that the photo-induced electrons transferred quickly to the conducting glass via external circuit and formed photocurrent.
