Login In
2005 Volume 21 Issue 6
2005, 21(06): 583-585
doi: 10.3866/PKU.WHXB20050601
Abstract:
Laser induced reaction of Ca+--tertbutylamine complex was studied by reflection time of flight spectrum (RTOF). Different photodissociation spectra, the action spectrum as function of laser wavelength, and ratio curve of different channels were obtained. Two channels were found, one was Ca+- cation separation channel, the other one was reactive channel for product Ca+-NH2. Product Ca+- was dominant in the whole region studied and the only one in the region 530～595 nm. The action spectrum shows pronounced structureless peaks, which are relevant to the transition of complex. The dynamics of the reaction was discussed at the end.
Laser induced reaction of Ca+--tertbutylamine complex was studied by reflection time of flight spectrum (RTOF). Different photodissociation spectra, the action spectrum as function of laser wavelength, and ratio curve of different channels were obtained. Two channels were found, one was Ca+- cation separation channel, the other one was reactive channel for product Ca+-NH2. Product Ca+- was dominant in the whole region studied and the only one in the region 530～595 nm. The action spectrum shows pronounced structureless peaks, which are relevant to the transition of complex. The dynamics of the reaction was discussed at the end.
2005, 21(06): 586-590
doi: 10.3866/PKU.WHXB20050602
Abstract:
The surface modification of potassium titanate whiskers (PTW) with n-octadecyltrichlorosilane (OTS) through self-assembly process was investigated. The surface free energies and polar components of PTW modified with OTS were calculated by measuring contact angles of benzene, ethylene glycol, water on the palletized surfaces. The results showed that the surface free energies and polar components of PTW modified with OTS were lower than those of PTW modified with traditional ways, such as covered with PMMA or modified with silane coupling agent (KH560), thus PTW modified with OTS had more conspicuous lipophilicity and hydrophobicity. Moreover, the results of IR spectrum and apolar component of surface free energy showed that the alkyl chains of OTS tilted on the surface of PTW after the modification.
The surface modification of potassium titanate whiskers (PTW) with n-octadecyltrichlorosilane (OTS) through self-assembly process was investigated. The surface free energies and polar components of PTW modified with OTS were calculated by measuring contact angles of benzene, ethylene glycol, water on the palletized surfaces. The results showed that the surface free energies and polar components of PTW modified with OTS were lower than those of PTW modified with traditional ways, such as covered with PMMA or modified with silane coupling agent (KH560), thus PTW modified with OTS had more conspicuous lipophilicity and hydrophobicity. Moreover, the results of IR spectrum and apolar component of surface free energy showed that the alkyl chains of OTS tilted on the surface of PTW after the modification.
2005, 21(06): 591-595
doi: 10.3866/PKU.WHXB20050603
Abstract:
The phase transition behaviors of poly(N,N-diethylacrylamide)(PDEA) and P(N,N-diethylacrylamideco-N-hydroxymethylacrylamide) (P(DEA-co-NHMAA)) aqueous solutions were studied by UV-Vis spectrophotometer. The results suggest that when the mass fraction of NHMAA is below 5.25%, the lower critical solution temperature (TLCS) decreases with the increasing of mass fraction of NHMAA. In contrast, TLCS increases with the increasing of mass fraction of NHMAA when it is higher than 5.25%. Due to the stronger hydrogen bonds between side chains of the copolymer and water, as well as between two side chains of the copolymer in aqueous solution, the phase transition of P(DEA-co-NHMAA) aqueous solution, compared with the phase transition of PDEA aqueous solution, shows less dependence on the concentration. For PDEA and P(DEA-co-NHMAA) aqueous solutions, the abrupt transition from coil to globular and the gradual transition from globular to coil may involve different mechanisms. A model has been proposed for the structure of P(DEA-co-NHMAA) formed in dilute aqueous solution.
The phase transition behaviors of poly(N,N-diethylacrylamide)(PDEA) and P(N,N-diethylacrylamideco-N-hydroxymethylacrylamide) (P(DEA-co-NHMAA)) aqueous solutions were studied by UV-Vis spectrophotometer. The results suggest that when the mass fraction of NHMAA is below 5.25%, the lower critical solution temperature (TLCS) decreases with the increasing of mass fraction of NHMAA. In contrast, TLCS increases with the increasing of mass fraction of NHMAA when it is higher than 5.25%. Due to the stronger hydrogen bonds between side chains of the copolymer and water, as well as between two side chains of the copolymer in aqueous solution, the phase transition of P(DEA-co-NHMAA) aqueous solution, compared with the phase transition of PDEA aqueous solution, shows less dependence on the concentration. For PDEA and P(DEA-co-NHMAA) aqueous solutions, the abrupt transition from coil to globular and the gradual transition from globular to coil may involve different mechanisms. A model has been proposed for the structure of P(DEA-co-NHMAA) formed in dilute aqueous solution.
2005, 21(06): 596-601
doi: 10.3866/PKU.WHXB20050604
Abstract:
The mechanism and affecting factors of the glass transition for polymers have been analyzed. The structural units of thirty-eight polyacrylates have been optimized and their quantum chemical descriptors have been obtained by DFT/6-31G(d) method. The calculated results indicate that the length of side chain, number of side chains, polarizability, dipole moment, EHOMO, heat capacity at constant volume, and thermal energy are the main factors affecting glass transition temperature (Tg). The regularity of Tg for polyacrylates is discussed by the pattern recognition method (PLS) with quantum chemical descriptors as features. The two classes of polymers with different Tg distribute in different regions. The quantitative relationship have been studied between these descriptors and Tg by stepwise regression and BP-ANN(back propagation artificial neural network) methods. The correlation coefficients between the predicted and experimental Tg for the two methods are 0.9753 and 0.9985, and the standard deviations are 18.42 and results 4.25, respectively.
The mechanism and affecting factors of the glass transition for polymers have been analyzed. The structural units of thirty-eight polyacrylates have been optimized and their quantum chemical descriptors have been obtained by DFT/6-31G(d) method. The calculated results indicate that the length of side chain, number of side chains, polarizability, dipole moment, EHOMO, heat capacity at constant volume, and thermal energy are the main factors affecting glass transition temperature (Tg). The regularity of Tg for polyacrylates is discussed by the pattern recognition method (PLS) with quantum chemical descriptors as features. The two classes of polymers with different Tg distribute in different regions. The quantitative relationship have been studied between these descriptors and Tg by stepwise regression and BP-ANN(back propagation artificial neural network) methods. The correlation coefficients between the predicted and experimental Tg for the two methods are 0.9753 and 0.9985, and the standard deviations are 18.42 and results 4.25, respectively.
2005, 21(06): 602-606
doi: 10.3866/PKU.WHXB20050605
Abstract:
The arrays of Pd-Ni nanowires were prepared on highly oriented pyrolytic graphite by electrochemical step-edge decoration under the control of successive potentiostatic triple-pulse. The affecting factors on the composition of Pd-Ni alloy were investigated. The experimental results showed that the alloy composition of palladium and nickel could be adjusted by changing the ratio of Ni2+ and Pd2+ concentrations. The diameters of nanowires were controlled by adjusting the growing time and the growing potential. In the mixture of 7 mmol•L-1 PdCl2， 3 mmol•L-1 NiSO4 and 0.2 mol•L-1 NH4Cl，at pH 8.5，the arrays of Pd-Ni alloy nanowires with mean diameter of 210 nm, length about 400 μm and composition of Ni mass fraction of 12.4% were synthesized with the nucleating pulse of -2.0 V, 0.2 s and growing pulse of -0.4 V, 1 h.
The arrays of Pd-Ni nanowires were prepared on highly oriented pyrolytic graphite by electrochemical step-edge decoration under the control of successive potentiostatic triple-pulse. The affecting factors on the composition of Pd-Ni alloy were investigated. The experimental results showed that the alloy composition of palladium and nickel could be adjusted by changing the ratio of Ni2+ and Pd2+ concentrations. The diameters of nanowires were controlled by adjusting the growing time and the growing potential. In the mixture of 7 mmol•L-1 PdCl2， 3 mmol•L-1 NiSO4 and 0.2 mol•L-1 NH4Cl，at pH 8.5，the arrays of Pd-Ni alloy nanowires with mean diameter of 210 nm, length about 400 μm and composition of Ni mass fraction of 12.4% were synthesized with the nucleating pulse of -2.0 V, 0.2 s and growing pulse of -0.4 V, 1 h.
2005, 21(06): 607-611
doi: 10.3866/PKU.WHXB20050606
Abstract:
Nano-sized TiO2 doped with different percentage of Fe3+was prepared quickly by sol-gel process and was first used as photocatalyst to degrade polyethylene(PE) film under UV (intensity of 60 W) irradiation for 240 h in the ambient air. Some properties of photocatalysts and PE films were characterized by the means of XRD, FT-IR and SEM. The results claimed that PE lost only 8.43%(w) of its mass under UV irradiation for 240 h, anatase TiO2 made PE film lost 30.66%(w). 0.5% Fe2O3/TiO2, 1.0%Fe2O3/TiO2 and 2.0% Fe2O3/TiO2 made PE lost their weights 35.91%(w), 20.72%(w), and 13.30%(w), respectively. Photocatalysts speeded the PE macromolecular chains scission and photo oxidation. SEM morphology of PE film after photodegradation showed that there were numerous pits and holes in the film. The XRD patterns indicated that products contained more wax in PE film than that in PE film without photocatalysts. There was an optimal content of doping Fe3+ in anatase TiO2. 0.5%Fe2O3/TiO2 had a higher activity in photdegradation of PE film than other TiO2 photocatalysts.
Nano-sized TiO2 doped with different percentage of Fe3+was prepared quickly by sol-gel process and was first used as photocatalyst to degrade polyethylene(PE) film under UV (intensity of 60 W) irradiation for 240 h in the ambient air. Some properties of photocatalysts and PE films were characterized by the means of XRD, FT-IR and SEM. The results claimed that PE lost only 8.43%(w) of its mass under UV irradiation for 240 h, anatase TiO2 made PE film lost 30.66%(w). 0.5% Fe2O3/TiO2, 1.0%Fe2O3/TiO2 and 2.0% Fe2O3/TiO2 made PE lost their weights 35.91%(w), 20.72%(w), and 13.30%(w), respectively. Photocatalysts speeded the PE macromolecular chains scission and photo oxidation. SEM morphology of PE film after photodegradation showed that there were numerous pits and holes in the film. The XRD patterns indicated that products contained more wax in PE film than that in PE film without photocatalysts. There was an optimal content of doping Fe3+ in anatase TiO2. 0.5%Fe2O3/TiO2 had a higher activity in photdegradation of PE film than other TiO2 photocatalysts.
2005, 21(06): 612-615
doi: 10.3866/PKU.WHXB20050607
Abstract:
This paper investigates reaction mechanism and electrochemical behavior of ZnO thin films deposited on transparent conducting glass from a simple aqueous zinc nitrate solution. Nanocrystalline ZnO films with grain sizes of 10～15 nm are obtained by controlling the growth rate of ZnO. XRD analysis demonstrates that the nanocrystalline ZnO thin film has phase purity and wurtzite structure. Optical characterizations show that such film has high optical transmittance (up to 90%) in the visible wavelength range and its band gap is 3.37 eV.
This paper investigates reaction mechanism and electrochemical behavior of ZnO thin films deposited on transparent conducting glass from a simple aqueous zinc nitrate solution. Nanocrystalline ZnO films with grain sizes of 10～15 nm are obtained by controlling the growth rate of ZnO. XRD analysis demonstrates that the nanocrystalline ZnO thin film has phase purity and wurtzite structure. Optical characterizations show that such film has high optical transmittance (up to 90%) in the visible wavelength range and its band gap is 3.37 eV.
2005, 21(06): 616-621
doi: 10.3866/PKU.WHXB20050608
Abstract:
In this paper, we conducted a series of experiments on zeolite in water and in acidic solutions using a continuous stirred tank reactor(CSTR) of an open system. We measured the reaction rates for zeolite with water and with low pH solutions at room temperature, and conducted associated studies of mineral surfaces by using SEM and SIMS. The results showed that incongruent dissolution of zeolite was related to the surface chemical modifications.
In this paper, we conducted a series of experiments on zeolite in water and in acidic solutions using a continuous stirred tank reactor(CSTR) of an open system. We measured the reaction rates for zeolite with water and with low pH solutions at room temperature, and conducted associated studies of mineral surfaces by using SEM and SIMS. The results showed that incongruent dissolution of zeolite was related to the surface chemical modifications.
2005, 21(06): 622-626
doi: 10.3866/PKU.WHXB20050609
Abstract:
An alumina film(AAO/Al) was prepared on Al plate surface by anodic oxidation. The photodecompositions of oleic acid and C2H4 were examined on the AAO/Al and a nude Al piece with FTIR-ATR and a batch reactor, respectively. The function of AAO film in the photodecomposition was discussed by combination of the activity studies with the results of characterizations of UV-DRS and FTIR. It was showed that the AAO/Al could absorb UV light of wavelength ＜ 265 nm, and the nude Al piece didn't absorb the light of wavelength ＞ 220 nm. The AAO/Al could enhance the photodecomposition of oleic acid and ethylene by irradiation of 254 nm UV light but the nude Al piece couldn't. For on AAO/Al, the conversions of oleic acid and ethylene were 70% (upon the illumination for 3 h) and 9% (upon the illumination for 4 h ), respectively；while for on the nude Al piece, the conversion of oleic acid was 30% and no oxidation of ethylene occurred. AAO/Al didn't present any enhancement to the photodecomposition under irradiation of 365 nm light, the conversion of oleic acid was ca 20% which was comparable with that on nude Al, and the photodecomposition of ethylene didn't occur on both samples. It was suggested that the AAO film could be excited by 254 nm light so as to present photocatalytic function, which resulted from the superfluous Al atoms and oxygen-deficient defects in its structure.
An alumina film(AAO/Al) was prepared on Al plate surface by anodic oxidation. The photodecompositions of oleic acid and C2H4 were examined on the AAO/Al and a nude Al piece with FTIR-ATR and a batch reactor, respectively. The function of AAO film in the photodecomposition was discussed by combination of the activity studies with the results of characterizations of UV-DRS and FTIR. It was showed that the AAO/Al could absorb UV light of wavelength ＜ 265 nm, and the nude Al piece didn't absorb the light of wavelength ＞ 220 nm. The AAO/Al could enhance the photodecomposition of oleic acid and ethylene by irradiation of 254 nm UV light but the nude Al piece couldn't. For on AAO/Al, the conversions of oleic acid and ethylene were 70% (upon the illumination for 3 h) and 9% (upon the illumination for 4 h ), respectively；while for on the nude Al piece, the conversion of oleic acid was 30% and no oxidation of ethylene occurred. AAO/Al didn't present any enhancement to the photodecomposition under irradiation of 365 nm light, the conversion of oleic acid was ca 20% which was comparable with that on nude Al, and the photodecomposition of ethylene didn't occur on both samples. It was suggested that the AAO film could be excited by 254 nm light so as to present photocatalytic function, which resulted from the superfluous Al atoms and oxygen-deficient defects in its structure.
2005, 21(06): 627-631
doi: 10.3866/PKU.WHXB20050610
Abstract:
PAn-PEG-PAn rod-coil triblock copolymers were prepared by chemical oxidation copolymerization of aniline and α,ω-bis(p-aminophenyl) poly(ethylene glycol)( BAPPEG) and were characterized by IR, elemental analysis, UV-Vis absorption spectroscopy, thermogravimetric analysis and TEM. The results showed that with increasing the molar ratio of feed An to feed BAPPEG(r), the PAn segment length in the copolymer increased, which was indicated by the red shift of the UV-Vis characteristic absorption peak corresponding to the PAn segment, and the thermal stabilities were enhanced. The rod-coil-rod triblock copolymers in water self-assembled into such different nano-structures as coreshell micelles, rods or rods-based net structures, depending on the PAn segment length.
PAn-PEG-PAn rod-coil triblock copolymers were prepared by chemical oxidation copolymerization of aniline and α,ω-bis(p-aminophenyl) poly(ethylene glycol)( BAPPEG) and were characterized by IR, elemental analysis, UV-Vis absorption spectroscopy, thermogravimetric analysis and TEM. The results showed that with increasing the molar ratio of feed An to feed BAPPEG(r), the PAn segment length in the copolymer increased, which was indicated by the red shift of the UV-Vis characteristic absorption peak corresponding to the PAn segment, and the thermal stabilities were enhanced. The rod-coil-rod triblock copolymers in water self-assembled into such different nano-structures as coreshell micelles, rods or rods-based net structures, depending on the PAn segment length.
2005, 21(06): 632-636
doi: 10.3866/PKU.WHXB20050611
Abstract:
A novel quantum Monte Carlo(QMC) differential approach was proposed, which can be used to directly compute the energy difference between two systems on the basis of accurate fixednode QMC al rithm, allowing the statistical error in the order of 10-5 hartree and the electroncorrelation energy over 90% for the computation results. By using a “rigid move” model and Jacobi transformation, a od positive correlation between energies of two configurations for a molecule was obtained, and thus the acquisition of accurate energy differences and molecules’ potential energy surfaces for two investigated systems is feasible.
A novel quantum Monte Carlo(QMC) differential approach was proposed, which can be used to directly compute the energy difference between two systems on the basis of accurate fixednode QMC al rithm, allowing the statistical error in the order of 10-5 hartree and the electroncorrelation energy over 90% for the computation results. By using a “rigid move” model and Jacobi transformation, a od positive correlation between energies of two configurations for a molecule was obtained, and thus the acquisition of accurate energy differences and molecules’ potential energy surfaces for two investigated systems is feasible.
2005, 21(06): 637-640
doi: 10.3866/PKU.WHXB20050612
Abstract:
ZnO nanocables were synthesized on ld coated silicon(100) substrate by zinc powder evaporation at 550 ℃. The source materials were pure zinc and tin powders with mass ratio of 1∶1 and the experiment was carried out under a constant flow of Ar(98%)/O2(2%) gas mixture(300 sccm(standard cubic centimeters per minute) in a quartz tube. SEM images showed that the nanocables were obtained in large-scale and the diameters and lengths of the nanocables were about 50 nm and several micrometers respectively. XRD, TEM and EDX investigations confirmed the core-shell structure, i.e. the core zone was single crystalline ZnO and the shell zone was SiOx amorphous layer. Interestingly, the ZnO core was grown along a unique direction of [2021], which was quite different from the conventional fast growth direction of〈0001〉,〈0110〉 and 〈2110〉of 1D ZnO nanoscale materials. A possible mechanism was also proposed. Firstly, ld film served as catalyst and the nanocables grew out from the surface of Au-Si-Zn liquid alloys；secondly, tin powders were used as inhibitor to keep a low partial pressure of zinc vapor.
ZnO nanocables were synthesized on ld coated silicon(100) substrate by zinc powder evaporation at 550 ℃. The source materials were pure zinc and tin powders with mass ratio of 1∶1 and the experiment was carried out under a constant flow of Ar(98%)/O2(2%) gas mixture(300 sccm(standard cubic centimeters per minute) in a quartz tube. SEM images showed that the nanocables were obtained in large-scale and the diameters and lengths of the nanocables were about 50 nm and several micrometers respectively. XRD, TEM and EDX investigations confirmed the core-shell structure, i.e. the core zone was single crystalline ZnO and the shell zone was SiOx amorphous layer. Interestingly, the ZnO core was grown along a unique direction of [2021], which was quite different from the conventional fast growth direction of〈0001〉,〈0110〉 and 〈2110〉of 1D ZnO nanoscale materials. A possible mechanism was also proposed. Firstly, ld film served as catalyst and the nanocables grew out from the surface of Au-Si-Zn liquid alloys；secondly, tin powders were used as inhibitor to keep a low partial pressure of zinc vapor.
2005, 21(06): 641-645
doi: 10.3866/PKU.WHXB20050613
Abstract:
Highly ordered amorphous Co-Pt alloy nanowire arrays are prepared by electrodepositing it into anodized aluminum disks with nanosized pores. SEM and TEM images reveal that the nanowires of array are uniform, well isolated, and parallel to each other. The average length of the Co-Pt alloy nanowires is about 10 μm and the typical diameter is about 35 nm. Its microstructures and magnetic properties are also investigated by XRD and VSM (vibrating sample magnetometer), respectively. The sample prepared by the electrodeposition shows perpendicular anisotropy, but the as-annealed sample does not show. These different magnetic behaviors before and after annealing can be attributed to their different microstructures. X-ray diffraction evidences show that the sample before annealing is amorphous, but it changes to be polycrystalline after annealing. In the poly-crystalline sample, due to the competition of shape anisotropy and magnetocrystal anisotropy, the sample does not display perpendicular anisotropy. But magnetocrystal anisotropy is very small in amorphous sample， there-fore, shape anisotropy plays a dominant role which leads to strong perpendicular anisotropy.
Highly ordered amorphous Co-Pt alloy nanowire arrays are prepared by electrodepositing it into anodized aluminum disks with nanosized pores. SEM and TEM images reveal that the nanowires of array are uniform, well isolated, and parallel to each other. The average length of the Co-Pt alloy nanowires is about 10 μm and the typical diameter is about 35 nm. Its microstructures and magnetic properties are also investigated by XRD and VSM (vibrating sample magnetometer), respectively. The sample prepared by the electrodeposition shows perpendicular anisotropy, but the as-annealed sample does not show. These different magnetic behaviors before and after annealing can be attributed to their different microstructures. X-ray diffraction evidences show that the sample before annealing is amorphous, but it changes to be polycrystalline after annealing. In the poly-crystalline sample, due to the competition of shape anisotropy and magnetocrystal anisotropy, the sample does not display perpendicular anisotropy. But magnetocrystal anisotropy is very small in amorphous sample， there-fore, shape anisotropy plays a dominant role which leads to strong perpendicular anisotropy.
2005, 21(06): 646-652
doi: 10.3866/PKU.WHXB20050614
Abstract:
Thirty coordination polyhedra, reflecting the presence of a stereoactive lone electron pair, in the crystal structures of antimony(III) aminopolycarboxylic complexonates reported in the literature, have been revised. The presence of the lone pair has been acknowledged by including secondary bonded ligand atom(s) in the vicinity of the lone pair of each antimony(III). The resulted polyhedra are discussed in terms of their dihedral angles. In order to focus on the inherent coordination geometry of the central Sb(III) the vertices of the overall polyhedron are moved to the surface of a unit sphere. Inclusion of secondary bonding ligand atom(s) is supported by the valence bond calculations.
Thirty coordination polyhedra, reflecting the presence of a stereoactive lone electron pair, in the crystal structures of antimony(III) aminopolycarboxylic complexonates reported in the literature, have been revised. The presence of the lone pair has been acknowledged by including secondary bonded ligand atom(s) in the vicinity of the lone pair of each antimony(III). The resulted polyhedra are discussed in terms of their dihedral angles. In order to focus on the inherent coordination geometry of the central Sb(III) the vertices of the overall polyhedron are moved to the surface of a unit sphere. Inclusion of secondary bonding ligand atom(s) is supported by the valence bond calculations.
2005, 21(06): 653-657
doi: 10.3866/PKU.WHXB20050615
Abstract:
The addition of propylene oxide with methanol was carried out over M and a detailed mechanism of the reaction was investigated by using FT-IR method. In-situ FT-IR revealed that methanol dissociation into methoxide and proton took place readily on M , and propylene oxide adsorbed on M could generate propylenelike species via carbanion intermediate. As a result, methanol dissociated into adsorbed methoxide and reacted with the propylenelike species in antiMarkownikov fashion, which led to the high selectivity to 1-methoxy-2-propanol on M .
The addition of propylene oxide with methanol was carried out over M and a detailed mechanism of the reaction was investigated by using FT-IR method. In-situ FT-IR revealed that methanol dissociation into methoxide and proton took place readily on M , and propylene oxide adsorbed on M could generate propylenelike species via carbanion intermediate. As a result, methanol dissociated into adsorbed methoxide and reacted with the propylenelike species in antiMarkownikov fashion, which led to the high selectivity to 1-methoxy-2-propanol on M .
Analytical Potential Energy Functions for the Electronic States X 1Σ+, A 1Π and B 1Σ+ of BH Molecule
2005, 21(06): 658-662
doi: 10.3866/PKU.WHXB20050616
Abstract:
The energies, equilibrium geometries and harmonic frequencies of three electronic states (the ground state X 1Σ+, the first degenerate state A 1Π and the second state B 1Σ+）of BH molecule have been calculated using the GSUM (group sum of operators) method of SAC/ SAC-CI with the basis sets D95++, 6-311++g and cc-PVTZ. Comparing among the above mentioned three basis sets, the conclusion is gained that the basis set cc-PVTZ is the most suitable for the energy calculation of BH molecule. The whole potential curves for these three electronic states are further scanned using SAC/cc-PVTZ method for the ground state and SAC-CI/cc-PVTZ methods for the excited states, then having a least square fitting to Murrell-Sorbie function, and last the spectroscopy constants (Be, αe, ωe, andωeχe) are calculated, which are in better agreement with the experimental data. It is believed that Murrell-Sorbie function form and SAC/ SAC-CI method are suitable not only for the ground state, but for the low-lying excited states as well.
The energies, equilibrium geometries and harmonic frequencies of three electronic states (the ground state X 1Σ+, the first degenerate state A 1Π and the second state B 1Σ+）of BH molecule have been calculated using the GSUM (group sum of operators) method of SAC/ SAC-CI with the basis sets D95++, 6-311++g and cc-PVTZ. Comparing among the above mentioned three basis sets, the conclusion is gained that the basis set cc-PVTZ is the most suitable for the energy calculation of BH molecule. The whole potential curves for these three electronic states are further scanned using SAC/cc-PVTZ method for the ground state and SAC-CI/cc-PVTZ methods for the excited states, then having a least square fitting to Murrell-Sorbie function, and last the spectroscopy constants (Be, αe, ωe, andωeχe) are calculated, which are in better agreement with the experimental data. It is believed that Murrell-Sorbie function form and SAC/ SAC-CI method are suitable not only for the ground state, but for the low-lying excited states as well.
2005, 21(06): 663-667
doi: 10.3866/PKU.WHXB20050617
Abstract:
The defect behaviors, such as defect complex formation and oxygen vacancy migration in ceria doped with alkaline earth oxides, including M , CaO, SrO, and BaO, were studied on the basis of energy minimization calculations. The result showed that CaO and SrO dissolve in CeO2 easier than M and BaO via an oxygen vacancy compensation mechanism. The association energy of neutral [CaCe″•VO••]× pair is the highest. The [VO•••MCe″•VO••]•• defect complex is not stable in ceria. The favorable route for oxygen vacancy, with the lowest migration energy, is between the second neighbor sites.
The defect behaviors, such as defect complex formation and oxygen vacancy migration in ceria doped with alkaline earth oxides, including M , CaO, SrO, and BaO, were studied on the basis of energy minimization calculations. The result showed that CaO and SrO dissolve in CeO2 easier than M and BaO via an oxygen vacancy compensation mechanism. The association energy of neutral [CaCe″•VO••]× pair is the highest. The [VO•••MCe″•VO••]•• defect complex is not stable in ceria. The favorable route for oxygen vacancy, with the lowest migration energy, is between the second neighbor sites.
2005, 21(06): 668-672
doi: 10.3866/PKU.WHXB20050618
Abstract:
ZnO nano/microstructures of different morphologies have been synthesized by using Zn(OH)42- and different ionic liquids with the aid of microwave irradiation. The as-prepared samples are characterized by X-ray diffraction (XRD), scanning electron microcopy (SEM), transmission electron microscopy (TEM), and photoluminescence(PL). The XRD pattern shows that the asprepared samples have hexa nal structures, SEM and TEM images demonstrate that sheet and rod aggregates of ZnO are formed. SAED(selected area electron diffraction) images of rods indicate the single crystal nature, and the PL spectrum of ZnO nanosheet aggregates exhibits a weak ultraviolet emission and a strong green emission at room temperature.
ZnO nano/microstructures of different morphologies have been synthesized by using Zn(OH)42- and different ionic liquids with the aid of microwave irradiation. The as-prepared samples are characterized by X-ray diffraction (XRD), scanning electron microcopy (SEM), transmission electron microscopy (TEM), and photoluminescence(PL). The XRD pattern shows that the asprepared samples have hexa nal structures, SEM and TEM images demonstrate that sheet and rod aggregates of ZnO are formed. SAED(selected area electron diffraction) images of rods indicate the single crystal nature, and the PL spectrum of ZnO nanosheet aggregates exhibits a weak ultraviolet emission and a strong green emission at room temperature.
2005, 21(06): 673-676
doi: 10.3866/PKU.WHXB20050619
Abstract:
Functional polymer microspheres with micron size, due to their excellent properties such as small size, narrow size distribution and kinds of functional groups, have gained broad applications in biomedicine, catalyst, bioengineering, separating engineering and information technology. In the present paper, uniform polystyrene (PS) microspheres with average size of 3.85 μm were prepared by dispersion polymerization. Through adding second monomer acrylonitrile (AN) to initiate dispersion copolymerization, uniform P(St-AN) copolymer microspheres with average size of 4.02 μm were prepared. These two kinds of polymer microspheres were characterized by morphology and size analysis, FT-IR and DSC. The results showed that acrylonitrile groups were uniformly grafted on the surfaces of polystyrene microspheres and enhanced the polarity of the surfaces. For the P(St-AN) copolymer micro-spheres, average diameter D=4.02 μm, standard deviation δ=0.30 μm, coefficient of variation ε=0.075 and glass transition temperature Tg=86.5 ℃.
Functional polymer microspheres with micron size, due to their excellent properties such as small size, narrow size distribution and kinds of functional groups, have gained broad applications in biomedicine, catalyst, bioengineering, separating engineering and information technology. In the present paper, uniform polystyrene (PS) microspheres with average size of 3.85 μm were prepared by dispersion polymerization. Through adding second monomer acrylonitrile (AN) to initiate dispersion copolymerization, uniform P(St-AN) copolymer microspheres with average size of 4.02 μm were prepared. These two kinds of polymer microspheres were characterized by morphology and size analysis, FT-IR and DSC. The results showed that acrylonitrile groups were uniformly grafted on the surfaces of polystyrene microspheres and enhanced the polarity of the surfaces. For the P(St-AN) copolymer micro-spheres, average diameter D=4.02 μm, standard deviation δ=0.30 μm, coefficient of variation ε=0.075 and glass transition temperature Tg=86.5 ℃.
2005, 21(06): 677-680
doi: 10.3866/PKU.WHXB20050620
Abstract:
The electronic absorption spectra of six different alkoxy substituted phthalocyaninatozincs in different solvents have been determined. It is found that a new band (named as X bands) appeared at the longer wavelength side of the Q band in some solvents, such as toluene and CH2Cl2. The band is assigned to the protonation of phthalocyaninatozincs by trace water in the solvent, and it is further proved by the fluorescence spectra and 1H NMR. By adding pyridine to the solution this X band vanishs, and by adding water to the desiccated solvent this X band recurs.
The electronic absorption spectra of six different alkoxy substituted phthalocyaninatozincs in different solvents have been determined. It is found that a new band (named as X bands) appeared at the longer wavelength side of the Q band in some solvents, such as toluene and CH2Cl2. The band is assigned to the protonation of phthalocyaninatozincs by trace water in the solvent, and it is further proved by the fluorescence spectra and 1H NMR. By adding pyridine to the solution this X band vanishs, and by adding water to the desiccated solvent this X band recurs.
2005, 21(06): 681-685
doi: 10.3866/PKU.WHXB20050621
Abstract:
The isothermal cure kinetics of the epoxy resin (EP)/montmorillionite composites, with anhydride as curing agent, was studied by means of differential scanning calorimetry (DSC), and the effects of original montmorillionite (MMT) and organic montmorillion (OMMT) on cure kinetics of epoxy resin were investigated. Analysis of DSC data indicated that curing process of the epoxy resin contains autocatalytic mechanism, the addition of the montmorillionite to the epoxy resin does not change the cure reaction mechanism. The curing process of the EP/montmorillionite composites was simulated by Kamal equation. Two reaction orders, m and n, and two rate constants, k1 and k2 were obtained. The overall reaction order, m + n, is in the range 2.4～3.0. The addition of the MMT to the epoxy resin decreases rate constants k1 and k2, but the OMMT makes rate constants k1 and k2 complicated. The cure activation energy of the epoxy resin varies slightly by the addition of montmorillionite.
The isothermal cure kinetics of the epoxy resin (EP)/montmorillionite composites, with anhydride as curing agent, was studied by means of differential scanning calorimetry (DSC), and the effects of original montmorillionite (MMT) and organic montmorillion (OMMT) on cure kinetics of epoxy resin were investigated. Analysis of DSC data indicated that curing process of the epoxy resin contains autocatalytic mechanism, the addition of the montmorillionite to the epoxy resin does not change the cure reaction mechanism. The curing process of the EP/montmorillionite composites was simulated by Kamal equation. Two reaction orders, m and n, and two rate constants, k1 and k2 were obtained. The overall reaction order, m + n, is in the range 2.4～3.0. The addition of the MMT to the epoxy resin decreases rate constants k1 and k2, but the OMMT makes rate constants k1 and k2 complicated. The cure activation energy of the epoxy resin varies slightly by the addition of montmorillionite.
2005, 21(06): 686-689
doi: 10.3866/PKU.WHXB20050622
Abstract:
The full potential linear augmented plane wave（FLAPW） method is used to study geometric and electronic structure of δ-Pu monolayers corresponding to the (100) and (111) surfaces in the generalized-gradient approximation(GGA). The results show that spin-orbit coupling has a stronger effect on the equilibrium structure and there is a significant compression of monolayer compared to the bulk. It should be possible to grow a thin film of δ-Pu on a substrate whose lattice constant is smaller than that of δ-Pu. For the surface atoms, due to the reduced nearest neighbors, the contribution to the bonding from 5f electrons is reduced and 5f electrons appear to be more localized with a stronger degree for (100) surface than (111) surface.
The full potential linear augmented plane wave（FLAPW） method is used to study geometric and electronic structure of δ-Pu monolayers corresponding to the (100) and (111) surfaces in the generalized-gradient approximation(GGA). The results show that spin-orbit coupling has a stronger effect on the equilibrium structure and there is a significant compression of monolayer compared to the bulk. It should be possible to grow a thin film of δ-Pu on a substrate whose lattice constant is smaller than that of δ-Pu. For the surface atoms, due to the reduced nearest neighbors, the contribution to the bonding from 5f electrons is reduced and 5f electrons appear to be more localized with a stronger degree for (100) surface than (111) surface.
2005, 21(06): 690-696
doi: 10.3866/PKU.WHXB20050623
Abstract:
This paper summarized our recent results in the construction of organic molecular nanostructures on metal surfaces. The so-prepared nanostructures were tuned by photochemical reaction and observed by scanning tunneling microscopy. The electronic characteristics of the nanostructures are measured by capillary tunneling junction method. Furthermore, the tendency of constructing, controlling and characterizing nanostructures on metal surfaces is pointed out.
This paper summarized our recent results in the construction of organic molecular nanostructures on metal surfaces. The so-prepared nanostructures were tuned by photochemical reaction and observed by scanning tunneling microscopy. The electronic characteristics of the nanostructures are measured by capillary tunneling junction method. Furthermore, the tendency of constructing, controlling and characterizing nanostructures on metal surfaces is pointed out.
2005, 21(06): 697-702
doi: 10.3866/PKU.WHXB20050624
Abstract:
The development and application of electrolyte based on ionic liquids in dye-sensitized solar cells (hereafter DSCs) were reviewed. The performances of DSCs with different ionic liquid electrolytes were compared. The solidification of ionic liquids with different types of gelators was also discussed. Finally, the application of ionic liquid electrolytes used in dye-sensitized solar cell module was introduced and the further development of ionic liquid electrolytes was predicted.
The development and application of electrolyte based on ionic liquids in dye-sensitized solar cells (hereafter DSCs) were reviewed. The performances of DSCs with different ionic liquid electrolytes were compared. The solidification of ionic liquids with different types of gelators was also discussed. Finally, the application of ionic liquid electrolytes used in dye-sensitized solar cell module was introduced and the further development of ionic liquid electrolytes was predicted.
