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2003 Volume 19 Issue 10
2003, 19(10): 889-891
doi: 10.3866/PKU.WHXB20031001
Abstract:
The aim of this study is to explore new phosphorescent materials as highly efficient electroluminescent (EL) emitters in organic light emitting diodes (OLEDs).Iridium (III) complexes were selected as the target compounds for their strong spin orbit coupling that may result in high efficient electro-phosphorescence in OLED at room temperature. Thus, a new iridium pyrazine complex, Ir(MDPP)2(acac)(MDPP=5-methyl-2,3-diphenylpyrazine; acac= acetylacetone) was synthesized by reaction of 5-methyl-2,3-diphenylpyrazine with iridium trichloride hydrate. The procedure of synthesis is simple and easy control. The complex was characterized by elemental analysis, 1H NMR, and mass spectroscopy. The complex shows strong 1MLCT (singlet metal to ligand charge-transfer) and 3MLCT (triplet metal to ligand charge-transfer) absorption at 386 and 507 nm, respectively. The complex also gives rise to a strong photoluminescence at 549 nm at room temperature. These results suggest the complex to be a promising phosphorescent material.
The aim of this study is to explore new phosphorescent materials as highly efficient electroluminescent (EL) emitters in organic light emitting diodes (OLEDs).Iridium (III) complexes were selected as the target compounds for their strong spin orbit coupling that may result in high efficient electro-phosphorescence in OLED at room temperature. Thus, a new iridium pyrazine complex, Ir(MDPP)2(acac)(MDPP=5-methyl-2,3-diphenylpyrazine; acac= acetylacetone) was synthesized by reaction of 5-methyl-2,3-diphenylpyrazine with iridium trichloride hydrate. The procedure of synthesis is simple and easy control. The complex was characterized by elemental analysis, 1H NMR, and mass spectroscopy. The complex shows strong 1MLCT (singlet metal to ligand charge-transfer) and 3MLCT (triplet metal to ligand charge-transfer) absorption at 386 and 507 nm, respectively. The complex also gives rise to a strong photoluminescence at 549 nm at room temperature. These results suggest the complex to be a promising phosphorescent material.
2003, 19(10): 892-895
doi: 10.3866/PKU.WHXB20031002
Abstract:
Cu/Co superlattice multilayer were prepared on the p-type Si substrate by electrochemical deposition. The cross-section profile of the multilayer was examined by SEM.XRD analysis indicates that the multilayers grow epitaxially when the modulate wavelength (λ) ranges 20 nm to 160 nm. Further decrease of λ, the epitaxial growth becomes more prominent. When λ is smaller than 20 nm, satellite peaks in the XRD patterns indicate that the multilayer has formed a superlattice structure. In addition, the GMR performance of the multilayers increases with the increase of the number of periods and keeps steady when the number of periods is above 300,that is to say, its effect on GMR performance can be ignored.
Cu/Co superlattice multilayer were prepared on the p-type Si substrate by electrochemical deposition. The cross-section profile of the multilayer was examined by SEM.XRD analysis indicates that the multilayers grow epitaxially when the modulate wavelength (λ) ranges 20 nm to 160 nm. Further decrease of λ, the epitaxial growth becomes more prominent. When λ is smaller than 20 nm, satellite peaks in the XRD patterns indicate that the multilayer has formed a superlattice structure. In addition, the GMR performance of the multilayers increases with the increase of the number of periods and keeps steady when the number of periods is above 300,that is to say, its effect on GMR performance can be ignored.
2003, 19(10): 896-901
doi: 10.3866/PKU.WHXB20031003
Abstract:
The electron structures of MB molecule and MB adsorbed on the mica surface were measured by XPS to determine how the chemical environment is changed when MB was adsorbed on the mica surface. We concluded that the nitrogen atom of the dimethylamino- is the adsorption site for the MB molecule. From AFM image of MB adsorbed on the mica surface, its corresponding height averages to 0.820 nm. This agrees well with the model proposed by Hähner, that the MB molecules are tilted with their largest face inclined at 65～70° with respect to the surface of mica.
The electron structures of MB molecule and MB adsorbed on the mica surface were measured by XPS to determine how the chemical environment is changed when MB was adsorbed on the mica surface. We concluded that the nitrogen atom of the dimethylamino- is the adsorption site for the MB molecule. From AFM image of MB adsorbed on the mica surface, its corresponding height averages to 0.820 nm. This agrees well with the model proposed by Hähner, that the MB molecules are tilted with their largest face inclined at 65～70° with respect to the surface of mica.
2003, 19(10): 902-906
doi: 10.3866/PKU.WHXB20031004
Abstract:
Ni/Ce-Zr-Al-O catalysts were prepared by hydrothermal synthesis method. The effect of NiO content on the basicity of catalyst was investigated by using H2-TPD (temperature programmed desorption), DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy), and CO2-TPD.The catalytic performance was tested and the amount of coke deposition was measured. The H2-TPD result shows that the amount of Ni on the catalyst surface increases with the NiO content. DRIFT and CO2-TPD results show that the bicarbonate and carbonate are the predominant species of the CO2 chemisorptions. The addition of few Ni can promote obviously CO2 chemisorptions and weaken the intensity of basicity. While Ni metal is preferable to reside on stronger basic site, the increase of NiO content can weaken the basicity, decrease the amount of basic site and weaken the CO2 adsorption performance. It weakens the performance of eliminating coke by mobile oxygen originated from CO2.So the catalytic activity of the sample with 7.0％(w) NiO decreases during reaction, the amount of coke deposition is much higher than that of the sample with 4.0％(w) NiO.
Ni/Ce-Zr-Al-O catalysts were prepared by hydrothermal synthesis method. The effect of NiO content on the basicity of catalyst was investigated by using H2-TPD (temperature programmed desorption), DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy), and CO2-TPD.The catalytic performance was tested and the amount of coke deposition was measured. The H2-TPD result shows that the amount of Ni on the catalyst surface increases with the NiO content. DRIFT and CO2-TPD results show that the bicarbonate and carbonate are the predominant species of the CO2 chemisorptions. The addition of few Ni can promote obviously CO2 chemisorptions and weaken the intensity of basicity. While Ni metal is preferable to reside on stronger basic site, the increase of NiO content can weaken the basicity, decrease the amount of basic site and weaken the CO2 adsorption performance. It weakens the performance of eliminating coke by mobile oxygen originated from CO2.So the catalytic activity of the sample with 7.0％(w) NiO decreases during reaction, the amount of coke deposition is much higher than that of the sample with 4.0％(w) NiO.
2003, 19(10): 907-912
doi: 10.3866/PKU.WHXB20031005
Abstract:
Mesoporous aluminosilicates were synthesized through S＋X－I＋ route using preformed β zeolitic nanoclusters as building units in acidic media and subsequent ammonia hydrothermal treatment. The ordered mesoporous aluminosilicates were characterized by XRD, N2 adsorption and desorption, HRTEM, SEM, NMR and NH3-TPD methods. The results indicated that the sample had the same hexa nal mesostructures as normal MCM-41 synthesized in acidic media. The presence of strongly acidic sites was substantiated by NH3-TPD study, and the hexa nal mesoporous structure was maintained even after 120 h treatment in boiling water. The synthesized materials were superior to conventional MCM-41 with respect to their stronger acidity and higher hydrothermal stability. The short period of assembly in acidic media and the ambient temperature reduced the dealumination effect considerably. The retention of zeolite-like connectivity of tetrahedral AlO4 and SiO4 units upon assembling the nanoclusters into mesostructured materials and the thicker framework pore walls contributed to the especially od hydrothermal stability greatly, which also gave rise to the presence of strong acidity.
Mesoporous aluminosilicates were synthesized through S＋X－I＋ route using preformed β zeolitic nanoclusters as building units in acidic media and subsequent ammonia hydrothermal treatment. The ordered mesoporous aluminosilicates were characterized by XRD, N2 adsorption and desorption, HRTEM, SEM, NMR and NH3-TPD methods. The results indicated that the sample had the same hexa nal mesostructures as normal MCM-41 synthesized in acidic media. The presence of strongly acidic sites was substantiated by NH3-TPD study, and the hexa nal mesoporous structure was maintained even after 120 h treatment in boiling water. The synthesized materials were superior to conventional MCM-41 with respect to their stronger acidity and higher hydrothermal stability. The short period of assembly in acidic media and the ambient temperature reduced the dealumination effect considerably. The retention of zeolite-like connectivity of tetrahedral AlO4 and SiO4 units upon assembling the nanoclusters into mesostructured materials and the thicker framework pore walls contributed to the especially od hydrothermal stability greatly, which also gave rise to the presence of strong acidity.
2003, 19(10): 913-916
doi: 10.3866/PKU.WHXB20031006
Abstract:
The ion exchange kinetics with changing bulk concentration of Mg2＋ on strong acid resins(001×7×7) was studied. Increasing the initial concentration of Mg2＋ and reducing the particle radius can accelerate the exchange rate of Mg2＋ .After reaching 315 r•min－1,the stirring speed has little effect on the exchange rate. An integrating equation of moving boundary model was used to describe the kinetics with changing bulk concentration of Mg2＋,and the overall kinetically equation was obtained. The ion exchange process of Mg2＋ is controlled by ion diffusion through particles. The apparent activation energy is calculated to be 23.45 kJ•mol－1, and apparent reaction order of Mg2＋ is 0.68.
The ion exchange kinetics with changing bulk concentration of Mg2＋ on strong acid resins(001×7×7) was studied. Increasing the initial concentration of Mg2＋ and reducing the particle radius can accelerate the exchange rate of Mg2＋ .After reaching 315 r•min－1,the stirring speed has little effect on the exchange rate. An integrating equation of moving boundary model was used to describe the kinetics with changing bulk concentration of Mg2＋,and the overall kinetically equation was obtained. The ion exchange process of Mg2＋ is controlled by ion diffusion through particles. The apparent activation energy is calculated to be 23.45 kJ•mol－1, and apparent reaction order of Mg2＋ is 0.68.
2003, 19(10): 917-921
doi: 10.3866/PKU.WHXB20031007
Abstract:
11 methanofullerenes have been investigated using cyclic voltammetry(CV) systematically and comparatively. The influence of the nature of groups introduced and chain length of substituents on the electron-accepting ability of methanofullerenes was observed. It was found that introducing electron-donating groups, such as alkyls, weaken the electron- accepting ability of C60 and make its first reduction wave shifted to more negative position. Introducing electron-withdrawing groups, such as carboxylic ester groups, compensate part of negative shift of the reduction wave due to the effect of the saturation of a fullerene double bond. It was also found that increasing the chain length of substituents would not obviously change the electron-accepting ability of C60. Furthermore, the split of reduction peaks of some methanofullerenes induced by electrochemical isomerization was explained.
11 methanofullerenes have been investigated using cyclic voltammetry(CV) systematically and comparatively. The influence of the nature of groups introduced and chain length of substituents on the electron-accepting ability of methanofullerenes was observed. It was found that introducing electron-donating groups, such as alkyls, weaken the electron- accepting ability of C60 and make its first reduction wave shifted to more negative position. Introducing electron-withdrawing groups, such as carboxylic ester groups, compensate part of negative shift of the reduction wave due to the effect of the saturation of a fullerene double bond. It was also found that increasing the chain length of substituents would not obviously change the electron-accepting ability of C60. Furthermore, the split of reduction peaks of some methanofullerenes induced by electrochemical isomerization was explained.
2003, 19(10): 922-926
doi: 10.3866/PKU.WHXB20031008
Abstract:
The synergism between cerium salt and lithium salt in the sealing of anodized film of aluminum has been investigated by using electrochemical impedance spectroscopy (EIS),scanning electron microscopy with a field-emission gun as electron source(FEG-SEM), X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS). It was revealed that the pores of anodized film of aluminum were covered with the sealing products and the corrosion resistance of the film was improved evidently by sealing process. The sealed films exhibited amorphous nature and mainly consisted of hydrous aluminum oxide and hydroxides of cerium and lithium. Some and anions of sealing solutions also existed in the films. Based on the experimental results, it could be inferred that the cerium and lithium species in the sealing solution have some kind of synergism, which can make the sealing products more compact and effectively improve the corrosion resistance of the film.
The synergism between cerium salt and lithium salt in the sealing of anodized film of aluminum has been investigated by using electrochemical impedance spectroscopy (EIS),scanning electron microscopy with a field-emission gun as electron source(FEG-SEM), X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS). It was revealed that the pores of anodized film of aluminum were covered with the sealing products and the corrosion resistance of the film was improved evidently by sealing process. The sealed films exhibited amorphous nature and mainly consisted of hydrous aluminum oxide and hydroxides of cerium and lithium. Some and anions of sealing solutions also existed in the films. Based on the experimental results, it could be inferred that the cerium and lithium species in the sealing solution have some kind of synergism, which can make the sealing products more compact and effectively improve the corrosion resistance of the film.
2003, 19(10): 927-932
doi: 10.3866/PKU.WHXB20031009
Abstract:
The geometric configurations, electronic structures and vibrational frequency of the AlmN(m=2～9)clusters were calculated with B3LYP method at 6-31G* level. The calculations show that the ground states of AlmN clusters can be rapidly obtained by adding an N atom to the different positions of Alm clusters. Analysis of the geometrical parameters of ground states structure reveals that there are only Al－N bonds in the chained and planar structures with m＜4, while there coexist Al－N bonds and Al－Al bonds in the structures with m≥4. Analysis of the energy of ground states structure shows the Al2N and Al3N clusters are more stable.
The geometric configurations, electronic structures and vibrational frequency of the AlmN(m=2～9)clusters were calculated with B3LYP method at 6-31G* level. The calculations show that the ground states of AlmN clusters can be rapidly obtained by adding an N atom to the different positions of Alm clusters. Analysis of the geometrical parameters of ground states structure reveals that there are only Al－N bonds in the chained and planar structures with m＜4, while there coexist Al－N bonds and Al－Al bonds in the structures with m≥4. Analysis of the energy of ground states structure shows the Al2N and Al3N clusters are more stable.
2003, 19(10): 933-937
doi: 10.3866/PKU.WHXB20031010
Abstract:
The effects of calcination temperatures and extractants on the structure and chemical stability of LiMn2O4 were examined by XRD, βLi (degree of Li＋ extraction) and γMn(degree of Mn2＋ dissolution) analyses, the results show that MnO2(Li) prepared at 750 ℃ for 2 h has larger exchange capacities using (NH4)2S2O8 as extractant. In addition, the mechanism of ion exchange reaction was studied by distribution coefficient measurement and kinetic experiment, and the mathematical model for ion exchange reaction kinetics in a finite solution has been established. The results indicate that this ion exchange process is controlled by particle diffusion; ion exchange reaction mainly occurs in the outer layer of MnO2(Li). The experimental results are in od agreement with the calculated values.
The effects of calcination temperatures and extractants on the structure and chemical stability of LiMn2O4 were examined by XRD, βLi (degree of Li＋ extraction) and γMn(degree of Mn2＋ dissolution) analyses, the results show that MnO2(Li) prepared at 750 ℃ for 2 h has larger exchange capacities using (NH4)2S2O8 as extractant. In addition, the mechanism of ion exchange reaction was studied by distribution coefficient measurement and kinetic experiment, and the mathematical model for ion exchange reaction kinetics in a finite solution has been established. The results indicate that this ion exchange process is controlled by particle diffusion; ion exchange reaction mainly occurs in the outer layer of MnO2(Li). The experimental results are in od agreement with the calculated values.
2003, 19(10): 938-943
doi: 10.3866/PKU.WHXB20031011
Abstract:
Quantitative structure-retention relationships(QSRR ,retention factors k1 and k2 for the first and second eluted enantiomer) as well as quantitative enantioselective retention relationships (QSERR, separation factor α) for a series of 50 chiral 5-arylhydantoins on the Pirkle-type chiral stationary phases are derived by the multiple linear regression analyses calculations using 2D and 3D molecular descriptors including those obtained by quantum chemical calculations. Different interactions between the different configuration and the CSP (chiral state phase) have been detected. The models will be useful to speculate the combining mode between the CSP and the analogues as well as to quantitatively prognosticate the separation of other 5-arylhydanoin analogues on Pirkle type chiral stationary phases.
Quantitative structure-retention relationships(QSRR ,retention factors k1 and k2 for the first and second eluted enantiomer) as well as quantitative enantioselective retention relationships (QSERR, separation factor α) for a series of 50 chiral 5-arylhydantoins on the Pirkle-type chiral stationary phases are derived by the multiple linear regression analyses calculations using 2D and 3D molecular descriptors including those obtained by quantum chemical calculations. Different interactions between the different configuration and the CSP (chiral state phase) have been detected. The models will be useful to speculate the combining mode between the CSP and the analogues as well as to quantitatively prognosticate the separation of other 5-arylhydanoin analogues on Pirkle type chiral stationary phases.
2003, 19(10): 944-947
doi: 10.3866/PKU.WHXB20031012
Abstract:
A new series of mesoporous silica materials containing nanodispersedα-Fe2O3were synthesized by different methods. X-ray diffraction patterns indicated thatα-Fe2O3/SAB-3 had a hexa nal array pore structure. The N2 adsorption and desorption showed that the materials had very high specific surface area.Fe3＋ entered into pore wall, which was confirmed by Fourier-transform infrared spectroscopy. The results of magnetic measurements showed that the coercive force(Hc) ofα-Fe2O3 decreased from 1 765 Oe to 87 Oe, specific saturation magnetization(Ms) increased by 75.4％ as compared with the conventional nanoα-Fe2O3 particles.
A new series of mesoporous silica materials containing nanodispersedα-Fe2O3were synthesized by different methods. X-ray diffraction patterns indicated thatα-Fe2O3/SAB-3 had a hexa nal array pore structure. The N2 adsorption and desorption showed that the materials had very high specific surface area.Fe3＋ entered into pore wall, which was confirmed by Fourier-transform infrared spectroscopy. The results of magnetic measurements showed that the coercive force(Hc) ofα-Fe2O3 decreased from 1 765 Oe to 87 Oe, specific saturation magnetization(Ms) increased by 75.4％ as compared with the conventional nanoα-Fe2O3 particles.
2003, 19(10): 948-951
doi: 10.3866/PKU.WHXB20031013
Abstract:
Two new niobates Sr5LaTi3Nb7O30 and Sr5YTi3Nb7O30 were synthesized by using high temperature solid state reaction in the SrO-Ln2O3-TiO2-Nb2O5 system. The crystal structure and dielectric properties were characterized by using X-ray powder diffraction, scanning electron microscope and dielectric measurements. The results show that Sr5LaTi3Nb7O30 belongs to paraelectric phase of fully filled tetra nal tungsten bronze structure at room temperature with unit cell parameters: a=1.233 60(4) nm, c= 0.388 01(2) nm. The room temperature dielectric constant (εr ) of Sr5LaTi3Nb7O30 ceramic reached 466 combined with a low dielectric loss of 0.005 at 1 MHz. While Sr5YTi3Nb7O30 belongs to ferroelectric phase of fully filled tetra nal tungsten bronze structure at room temperature with unit cell parameters: a=1.228 80(4) nm, c=0.387 05(2) nm. Sr5YTi3Nb7O30 has significant relaxor behaviors, and the phase transition from ferroelectric to paraelectric occurred at temperature 260 ℃ and frequency 10 kHz. The room temperature relative dielectric constant (εr) of Sr5YTi3Nb7O30 ceramic reached 290 at 1 MHz.
Two new niobates Sr5LaTi3Nb7O30 and Sr5YTi3Nb7O30 were synthesized by using high temperature solid state reaction in the SrO-Ln2O3-TiO2-Nb2O5 system. The crystal structure and dielectric properties were characterized by using X-ray powder diffraction, scanning electron microscope and dielectric measurements. The results show that Sr5LaTi3Nb7O30 belongs to paraelectric phase of fully filled tetra nal tungsten bronze structure at room temperature with unit cell parameters: a=1.233 60(4) nm, c= 0.388 01(2) nm. The room temperature dielectric constant (εr ) of Sr5LaTi3Nb7O30 ceramic reached 466 combined with a low dielectric loss of 0.005 at 1 MHz. While Sr5YTi3Nb7O30 belongs to ferroelectric phase of fully filled tetra nal tungsten bronze structure at room temperature with unit cell parameters: a=1.228 80(4) nm, c=0.387 05(2) nm. Sr5YTi3Nb7O30 has significant relaxor behaviors, and the phase transition from ferroelectric to paraelectric occurred at temperature 260 ℃ and frequency 10 kHz. The room temperature relative dielectric constant (εr) of Sr5YTi3Nb7O30 ceramic reached 290 at 1 MHz.
2003, 19(10): 952-956
doi: 10.3866/PKU.WHXB20031014
Abstract:
Highly thermostable palladium catalysts have been prepared by sol-gel method. The possible effects of pH of alumina gel precursor on the final structure and thermal stability of catalyst have been investigated by the wide-angle X-ray diffraction, laser light scattering (LLS) and BET techniques. The results indicated that pore size distributions of catalyst are related with the gel particle size distributions, which were strongly dependent on the pH of the system. It was found that the Pd particles could be anchored within the relatively stable alumina host structure by sol-gel method and resulted in elevation of hydrothermal stability, as well as the enhancement of catalytic activity for CO and C3H6 oxidation over aged catalysts. In addition, it was found that the La2O3 additive could elevate the phase transfer temperature of alumina remarkably, whereas it promoted the sintering of Pd to form bigger particle size at high temperature. The experimental results showed the La2O3 additive could promote the catalytic activities for oxidation of CO and C3H6 over fresh Pd catalysts. However, the activities were a little lower than that of unmodified catalyst after aged at 1050 ℃ for 24 h due to more serious sintering of Pd metal on the surface.
Highly thermostable palladium catalysts have been prepared by sol-gel method. The possible effects of pH of alumina gel precursor on the final structure and thermal stability of catalyst have been investigated by the wide-angle X-ray diffraction, laser light scattering (LLS) and BET techniques. The results indicated that pore size distributions of catalyst are related with the gel particle size distributions, which were strongly dependent on the pH of the system. It was found that the Pd particles could be anchored within the relatively stable alumina host structure by sol-gel method and resulted in elevation of hydrothermal stability, as well as the enhancement of catalytic activity for CO and C3H6 oxidation over aged catalysts. In addition, it was found that the La2O3 additive could elevate the phase transfer temperature of alumina remarkably, whereas it promoted the sintering of Pd to form bigger particle size at high temperature. The experimental results showed the La2O3 additive could promote the catalytic activities for oxidation of CO and C3H6 over fresh Pd catalysts. However, the activities were a little lower than that of unmodified catalyst after aged at 1050 ℃ for 24 h due to more serious sintering of Pd metal on the surface.
2003, 19(10): 957-961
doi: 10.3866/PKU.WHXB20031015
Abstract:
Many features and disadvantages of reaction mechanisms and models suggested for BR (Briggs-Rauscher) oscillatory system are summarized briefly in this paper. Moreover, a simplified model for a nine-step reaction mechanism is proposed which can simulate concentration variations of the following four species HIO2, I2, I－ and O2.The model exhibits periodic oscillatory behavior in a wide range of initial concentrations of inflow species, and can be used to elucidate some special experimental phenomena. Additionally, limit cycle and bistabilty are observed in this model.
Many features and disadvantages of reaction mechanisms and models suggested for BR (Briggs-Rauscher) oscillatory system are summarized briefly in this paper. Moreover, a simplified model for a nine-step reaction mechanism is proposed which can simulate concentration variations of the following four species HIO2, I2, I－ and O2.The model exhibits periodic oscillatory behavior in a wide range of initial concentrations of inflow species, and can be used to elucidate some special experimental phenomena. Additionally, limit cycle and bistabilty are observed in this model.
2003, 19(10): 962-966
doi: 10.3866/PKU.WHXB20031016
Abstract:
A bis-8-hydroxyquinoline “open chain crown ether" derivative (QP3Q) and its aluminum or zinc complex are synthesized. The steady state spectroscopy properties and fluorescence decay processes for the complexes (QP3Q-Zn2＋ and QP3Q-Al3＋) are studied. The composition and stability of the complexes are determined by their UV-Vis absorption. Both aluminum and zinc ions coordinated with QP3Q are in the proportion of 1∶1 and the stability constant of QP3Q-Zn2＋ and QP3Q-Al3＋ are 620 and 1820 L•mol－1,respectively. For QP3Q-Zn2＋, the fluorescence emission peaks are at 436 nm with the quantum yield of 0.26 in methanol and 472 nm for the solid sample. The maximum wavelengths of the fluorescence of QP3Q-Al3＋ are at 486 nm with quantum yield of 0.11 in methanol and 476 nm for its powder. The fluorescence of the complexes shows two exponential decay processes and the lifetimes for the main component are 44.8 and 11.3 ns for QP3Q-Zn2＋ and QP3Q-Al3＋, respectively.
A bis-8-hydroxyquinoline “open chain crown ether" derivative (QP3Q) and its aluminum or zinc complex are synthesized. The steady state spectroscopy properties and fluorescence decay processes for the complexes (QP3Q-Zn2＋ and QP3Q-Al3＋) are studied. The composition and stability of the complexes are determined by their UV-Vis absorption. Both aluminum and zinc ions coordinated with QP3Q are in the proportion of 1∶1 and the stability constant of QP3Q-Zn2＋ and QP3Q-Al3＋ are 620 and 1820 L•mol－1,respectively. For QP3Q-Zn2＋, the fluorescence emission peaks are at 436 nm with the quantum yield of 0.26 in methanol and 472 nm for the solid sample. The maximum wavelengths of the fluorescence of QP3Q-Al3＋ are at 486 nm with quantum yield of 0.11 in methanol and 476 nm for its powder. The fluorescence of the complexes shows two exponential decay processes and the lifetimes for the main component are 44.8 and 11.3 ns for QP3Q-Zn2＋ and QP3Q-Al3＋, respectively.
2003, 19(10): 967-969
doi: 10.3866/PKU.WHXB20031017
Abstract:
The copper doped titanium dioxide was prepared by immersion method. Photocatalytic activity was investigated with acetic acid as a model reactant, and the photocatalyst was analyzed by means of XPS. The enhanced degradation rate of acetic acid is attributed to increased charge separation and interfacial charge-transfer rate on the surface of the doped photocatalyst.
The copper doped titanium dioxide was prepared by immersion method. Photocatalytic activity was investigated with acetic acid as a model reactant, and the photocatalyst was analyzed by means of XPS. The enhanced degradation rate of acetic acid is attributed to increased charge separation and interfacial charge-transfer rate on the surface of the doped photocatalyst.
2003, 19(10): 970-973
doi: 10.3866/PKU.WHXB20031018
Abstract:
Amorphous NiB, NiB/Al2O3 and NiBSm/Al2O3 catalysts were prepared by chemical reduction method. The bulk compositions of catalysts were analyzed by inductively coupled plasma (ICP). Thermal stability of the catalyst was investigated by differential scanning calorimetry (DSC). The results showed that the content of boron in bulk composition of amorphous NiB alloy decreased with the introduction of support Al2O3. The thermal stability of amorphous NiB alloy was improved obviously after supported on γ-alumina and further enhanced by adding small amount of Sm. The data of activation energy for crystallization also showed the positive effects of support and Sm on thermal stability of amorphous NiB alloy. Support and Sm may change the thermal stability by different mechanisms.
Amorphous NiB, NiB/Al2O3 and NiBSm/Al2O3 catalysts were prepared by chemical reduction method. The bulk compositions of catalysts were analyzed by inductively coupled plasma (ICP). Thermal stability of the catalyst was investigated by differential scanning calorimetry (DSC). The results showed that the content of boron in bulk composition of amorphous NiB alloy decreased with the introduction of support Al2O3. The thermal stability of amorphous NiB alloy was improved obviously after supported on γ-alumina and further enhanced by adding small amount of Sm. The data of activation energy for crystallization also showed the positive effects of support and Sm on thermal stability of amorphous NiB alloy. Support and Sm may change the thermal stability by different mechanisms.
2003, 19(10): 974-977
doi: 10.3866/PKU.WHXB20031019
Abstract:
Based on quantum chemical calculation, the thermodynamic data and equilibrium constant of the NH＋O3→ONH＋O2 reaction are calculated using the statistical theory at 100～1600 K. On the basis of Eyring transition state theory with Wigner correction, the activation thermodynamic data, rate constant, and frequency factors of both reaction channels are obtained from 100 to 1600 K. The results show that, compared to reaction channel II, reaction channel I of the reaction between active free radical NH and ozone O3 is not only spontaneous but also easy to take place kinetically.
Based on quantum chemical calculation, the thermodynamic data and equilibrium constant of the NH＋O3→ONH＋O2 reaction are calculated using the statistical theory at 100～1600 K. On the basis of Eyring transition state theory with Wigner correction, the activation thermodynamic data, rate constant, and frequency factors of both reaction channels are obtained from 100 to 1600 K. The results show that, compared to reaction channel II, reaction channel I of the reaction between active free radical NH and ozone O3 is not only spontaneous but also easy to take place kinetically.
Effect of Morphological Structure and Photoelectric Properties on Photocatalytic Performance of TiO2
2003, 19(10): 978-981
doi: 10.3866/PKU.WHXB20031020
Abstract:
TiO2 photocatalysts prepared by sol-gel method were characterized by X-ray diffraction (XRD), UV diffuse reflectance spectroscopy (DRS), N2 adsorption BET method, surface photovoltage spectroscopy (SPS). A test compound ethylene in the gas phase was employed in the heterogeneous photocatalytic oxidation to investigate the effects of properties of TiO2 nanoparticles on photocatalytic performance. The results showed that crystal size of TiO2 increased slowly and its surface area downgraded with the increasing of calcination temperature; the crystal phase of TiO2 changed from anatase to rutile, the threshold of SPS decreased and the band edge red-shifted to yield smaller redox potential, leading to the significantly decreased of photocatalytic activity.
TiO2 photocatalysts prepared by sol-gel method were characterized by X-ray diffraction (XRD), UV diffuse reflectance spectroscopy (DRS), N2 adsorption BET method, surface photovoltage spectroscopy (SPS). A test compound ethylene in the gas phase was employed in the heterogeneous photocatalytic oxidation to investigate the effects of properties of TiO2 nanoparticles on photocatalytic performance. The results showed that crystal size of TiO2 increased slowly and its surface area downgraded with the increasing of calcination temperature; the crystal phase of TiO2 changed from anatase to rutile, the threshold of SPS decreased and the band edge red-shifted to yield smaller redox potential, leading to the significantly decreased of photocatalytic activity.
2003, 19(10): 982-985
doi: 10.3866/PKU.WHXB20031021
Abstract:
The effects of various kinds of sodium carboxylates such as glycollate(NaGly), tartrate（Na2Tart）, citrate（Na3Cit） and the disodium of EDTA(Na2EDTA) on the phase compositions of calcium oxalate (CaC2O4) were studied in aqueous solution and X-ray powder diffraction was used to characterize the products. The results are all showed in Table 1. It can be seen that in the presence of sodium carboxylates, the percentages of the calcium oxalate monohydrate (COM), dihydrate (COD) and trihydrate (COT) in the crystals depend on the concentration of the carboxylates. In lower concentration range only COM was precipited. In higher concentration range COD and COT were induced. The ability to inhibit the formation of COM but favor that of COD and COT follows the order: Na3Cit >Na2Tart >Na2EDTA >NaGly. So citrate is considered to be an effective inhibitor of curing urolithiasis. Our study can give a reference for clinical therapy.
The effects of various kinds of sodium carboxylates such as glycollate(NaGly), tartrate（Na2Tart）, citrate（Na3Cit） and the disodium of EDTA(Na2EDTA) on the phase compositions of calcium oxalate (CaC2O4) were studied in aqueous solution and X-ray powder diffraction was used to characterize the products. The results are all showed in Table 1. It can be seen that in the presence of sodium carboxylates, the percentages of the calcium oxalate monohydrate (COM), dihydrate (COD) and trihydrate (COT) in the crystals depend on the concentration of the carboxylates. In lower concentration range only COM was precipited. In higher concentration range COD and COT were induced. The ability to inhibit the formation of COM but favor that of COD and COT follows the order: Na3Cit >Na2Tart >Na2EDTA >NaGly. So citrate is considered to be an effective inhibitor of curing urolithiasis. Our study can give a reference for clinical therapy.
2003, 19(10): 986-992
doi: 10.3866/PKU.WHXB20031022
Abstract:
According to the size of time and space of computer simulation about surfactant solution behavior, three methods, such as atomistic simulation, coarse-grain simulation and mesoscopic simulation, were introduced. Applications of these simulation methods on surfactant monomer, surfactant aggregates, and the interaction between surfactants and polymers are summarized. The futural development of the application of computer simulation to study surfactants is also referred to.
According to the size of time and space of computer simulation about surfactant solution behavior, three methods, such as atomistic simulation, coarse-grain simulation and mesoscopic simulation, were introduced. Applications of these simulation methods on surfactant monomer, surfactant aggregates, and the interaction between surfactants and polymers are summarized. The futural development of the application of computer simulation to study surfactants is also referred to.
