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2008 Volume 24 Issue 5
2008, 24(05):
Abstract:
2008, 24(05): 737-742
doi: 10.1016/S1872-1508(08)60030-3
Abstract:
Isosteric heats and adsorption isotherms of methane on nanometer active carbon were measured at supercritical temperature (273-373 K) and pressure from 0 to 10 MPa. The measured data agreed well with Dubinin-Astakhov (DA) model at lower pressure but failed when pressure exceeded a special range. General Freundlich (GF) equation was used to modify the DA equation at high pressure and thus formed a combined bisection model GFDA. The adsorption mechanism of methane on nanometer active carbon was raised according to GFDA model and the heterogeneous energy distribution of the adsorbent was analyzed.
Isosteric heats and adsorption isotherms of methane on nanometer active carbon were measured at supercritical temperature (273-373 K) and pressure from 0 to 10 MPa. The measured data agreed well with Dubinin-Astakhov (DA) model at lower pressure but failed when pressure exceeded a special range. General Freundlich (GF) equation was used to modify the DA equation at high pressure and thus formed a combined bisection model GFDA. The adsorption mechanism of methane on nanometer active carbon was raised according to GFDA model and the heterogeneous energy distribution of the adsorbent was analyzed.
2008, 24(05): 743-748
doi: 10.1016/S1872-1508(08)60031-5
Abstract:
Achiral spin state of (N+H) in D- and L-alanine was established by monitoring the temperature dependence of dc-magnetic susceptibility (dc: direct current) under the external magnetic field of 1 T. An intrinsic spin chirality of electrons in the atomic magnetic dipole moment of (N+H) was also supported by polarized Raman spectroscopy. Magnetic chirality was associated with a strongly correlated electron system that was related to spin rigidity. Raman vibrational spectra were unrelated to structural chirality but could reflect spin chirality due to the reversal of motion breaking. The spin transition of (N+H) occured at 270 K without bond breaking but was assisted by an intermediate hydrogen bond elongation, splitting and reformation with NH+3 torsion. The energy difference of spin chirality transitions between D- and L-alanine was around 10-4-10-5 eV·molecule-1.
Achiral spin state of (N+H) in D- and L-alanine was established by monitoring the temperature dependence of dc-magnetic susceptibility (dc: direct current) under the external magnetic field of 1 T. An intrinsic spin chirality of electrons in the atomic magnetic dipole moment of (N+H) was also supported by polarized Raman spectroscopy. Magnetic chirality was associated with a strongly correlated electron system that was related to spin rigidity. Raman vibrational spectra were unrelated to structural chirality but could reflect spin chirality due to the reversal of motion breaking. The spin transition of (N+H) occured at 270 K without bond breaking but was assisted by an intermediate hydrogen bond elongation, splitting and reformation with NH+3 torsion. The energy difference of spin chirality transitions between D- and L-alanine was around 10-4-10-5 eV·molecule-1.
2008, 24(05): 749-754
doi: 10.3866/PKU.WHXB20080503
Abstract:
DNA/CdS nanoparticle composites (DNA/CdS NPC) containing single or double strands and different concentrations of DNA were constructed in aqueous solutions. The effect of DNA on the photoelectrochemical properties of DNA/CdS NPC was investigated and the spectroscopic properties of DNA/CdS NPC were characterized by TEM, UV-Vis, IR, and fluorescent spectrometry. The results showed that CdS nanoparticles (CdS NPs)were combined with DNA strands through the electrostatic interaction; DNA templates did not affect the band gap of CdS NPs; DNA-templated CdS NPs had a higher density of surface states than that stabilized by Na4P2O7, which enhanced the photoluminescence (PL) intensity whereas restrained the photocurrent response of CdS NPs. Besides, there was certain dependency of both the increase of PL intensity and the decrease of photocurrent response on DNA concentrations in DNA/CdS NPC. The composites were hopeful for applications in both fluorescent tagged detections and quantitative analysis of DNA.
DNA/CdS nanoparticle composites (DNA/CdS NPC) containing single or double strands and different concentrations of DNA were constructed in aqueous solutions. The effect of DNA on the photoelectrochemical properties of DNA/CdS NPC was investigated and the spectroscopic properties of DNA/CdS NPC were characterized by TEM, UV-Vis, IR, and fluorescent spectrometry. The results showed that CdS nanoparticles (CdS NPs)were combined with DNA strands through the electrostatic interaction; DNA templates did not affect the band gap of CdS NPs; DNA-templated CdS NPs had a higher density of surface states than that stabilized by Na4P2O7, which enhanced the photoluminescence (PL) intensity whereas restrained the photocurrent response of CdS NPs. Besides, there was certain dependency of both the increase of PL intensity and the decrease of photocurrent response on DNA concentrations in DNA/CdS NPC. The composites were hopeful for applications in both fluorescent tagged detections and quantitative analysis of DNA.
2008, 24(05): 755-759
doi: 10.3866/PKU.WHXB20080504
Abstract:
The structures, energies, harmonic vibrational frequencies, and nucleus independent chemical shifts (NICS) of As-5 , [As5M]- and [As5MAs5]2-(M=Ti, Zr, Hf) were calculated by the density functional theory (DFT) . The dissected NICS of these species were computed to discuss the NICS contributions of the σ bonds, π bonds, lone pairs, and core electrons of As and M atoms. The calculations showed that the ground states of As-5, [As5M]-, and [As5MAs5]2- were in D5h, C5v, and D5h symmetries, respectively, and they were aromatic with negative NICS values. The dissected NICS indicated that the aromaticity of As-5 (D5h) mainly arised fromthe contributions of As—As π and As—As σ bonds, and the total NICS of [As5M]-(C5v) were dominated by the contributions of As—M bonds with the As—As σ bond followed. The total NICS of [As5TiAs5]2-(D5h) arised mainly from the As—As π bonds, and in the [As5ZrAs5]2-(D5h), the contribution of the As—As π bonds reduced while the contribution of the As—Zr bond increased relatively. In the [As5HfAs5]2- (D5h), the aromaticity mainly owed to the effects of the As—Hf bonds.
The structures, energies, harmonic vibrational frequencies, and nucleus independent chemical shifts (NICS) of As-5 , [As5M]- and [As5MAs5]2-(M=Ti, Zr, Hf) were calculated by the density functional theory (DFT) . The dissected NICS of these species were computed to discuss the NICS contributions of the σ bonds, π bonds, lone pairs, and core electrons of As and M atoms. The calculations showed that the ground states of As-5, [As5M]-, and [As5MAs5]2- were in D5h, C5v, and D5h symmetries, respectively, and they were aromatic with negative NICS values. The dissected NICS indicated that the aromaticity of As-5 (D5h) mainly arised fromthe contributions of As—As π and As—As σ bonds, and the total NICS of [As5M]-(C5v) were dominated by the contributions of As—M bonds with the As—As σ bond followed. The total NICS of [As5TiAs5]2-(D5h) arised mainly from the As—As π bonds, and in the [As5ZrAs5]2-(D5h), the contribution of the As—As π bonds reduced while the contribution of the As—Zr bond increased relatively. In the [As5HfAs5]2- (D5h), the aromaticity mainly owed to the effects of the As—Hf bonds.
2008, 24(05): 760-766
doi: 10.1016/S1872-1508(08)60032-7
Abstract:
A new coordination compound [Ni(CHZ)3]SO4·3H2O (CHZ = carbohydrazide) was synthesized and characterized by elemental analysis and fourier transforminfrared (FTIR) spectra, and its crystal structure was determined by X-ray single crystal diffraction. The crystal belonged to the triclinic system, space group P1 with a=0.85237(1) nm, b=0.90964(1) nm, c=1.22559(2) nm, β=96.731(2)°, V=0.8849(2) nm3, Z=2, Dc=1.798 g·cm-3. In the asymmetric unit, three carbohydrazide (CHZ) bidentate ligands were coordinated with a Ni(II) cation by carbonyl O atoms and terminal N atoms of the hydrazine groups to form three planar chelate rings which were vertical to one another. Ni(II) cations, CHZ ligand molecules, sulfate anions, and lattice water molecules were jointed to a complicated three-dimensional network structure through coordination bonds, electrostatic forces and extensive hydrogen bonds. Natural bond orbital (NBO) atomic charges of CHZ were obtained from the density functional theory (DFT) method at the B3LYP/6-311+G* level to interpret the reason why the coordination sites in carbohydrazide molecule were the oxygen atom of the carbonyl group and terminal N atoms of the hydrazine group. The thermal decomposition mechanism was tested through differential scanning calorimetry (DSC), thermogravimetric analyses, and Fourier transform infrared spectra. The kinetic parameters of the two exothermic processes of the title compound were studied applying the Kissinger’s and Ozawa-Doyle’s methods. The results indicated that the title complex possessed high energy and od thermal stability.
A new coordination compound [Ni(CHZ)3]SO4·3H2O (CHZ = carbohydrazide) was synthesized and characterized by elemental analysis and fourier transforminfrared (FTIR) spectra, and its crystal structure was determined by X-ray single crystal diffraction. The crystal belonged to the triclinic system, space group P1 with a=0.85237(1) nm, b=0.90964(1) nm, c=1.22559(2) nm, β=96.731(2)°, V=0.8849(2) nm3, Z=2, Dc=1.798 g·cm-3. In the asymmetric unit, three carbohydrazide (CHZ) bidentate ligands were coordinated with a Ni(II) cation by carbonyl O atoms and terminal N atoms of the hydrazine groups to form three planar chelate rings which were vertical to one another. Ni(II) cations, CHZ ligand molecules, sulfate anions, and lattice water molecules were jointed to a complicated three-dimensional network structure through coordination bonds, electrostatic forces and extensive hydrogen bonds. Natural bond orbital (NBO) atomic charges of CHZ were obtained from the density functional theory (DFT) method at the B3LYP/6-311+G* level to interpret the reason why the coordination sites in carbohydrazide molecule were the oxygen atom of the carbonyl group and terminal N atoms of the hydrazine group. The thermal decomposition mechanism was tested through differential scanning calorimetry (DSC), thermogravimetric analyses, and Fourier transform infrared spectra. The kinetic parameters of the two exothermic processes of the title compound were studied applying the Kissinger’s and Ozawa-Doyle’s methods. The results indicated that the title complex possessed high energy and od thermal stability.
2008, 24(05): 767-771
doi: 10.1016/S1872-1508(08)60033-9
Abstract:
The mechanism of solid-solid reaction between BaCO3 and Co3O4/Fe2O3/Nb2O5 has been investigated by means of non-isothermal thermogravimetry and differential scanning calorimetry (DSC) under flowing air gas conditions at atmospheric pressure with a new solid-solid reaction model. The effects of high speed agitating mixing and ball-milling mixing processes on the synthesis kinetics were also studied. The synthesis kinetics of Ba1.0Co0.7Fe0.2Nb0.1O3-δ from the BaCO3 and Co3O4/Fe2O3/Nb2O5 particles was calculated by applying the modified model. The results indicated that the overall reaction process was considered involving two stages: addition reaction between BaCO3 and Co3O4/Fe2O3/Nb2O5 particles in the first stage and solution reaction between BaCoO3, BaFeO3, and BaNbO3 to form a homogeneous Ba1.0Co0.7Fe0.2Nb0.1O3-δ phase in the second stage. The new model matched well with the experimental data. The apparent activation energy of addition reaction stage of the high speed agitating mixing sample was estimated to be 376.76 kJ·mol-1, which was only 3/4 of that of the ball-milling mixing sample (494.76 kJ·mol-1). These results indicated that the high-speed agitating process could enhance atomic diffusion and facilitate the subsequent reaction, thus it is believed as a more effective, energy saving, and environmentally benign mixing process.
The mechanism of solid-solid reaction between BaCO3 and Co3O4/Fe2O3/Nb2O5 has been investigated by means of non-isothermal thermogravimetry and differential scanning calorimetry (DSC) under flowing air gas conditions at atmospheric pressure with a new solid-solid reaction model. The effects of high speed agitating mixing and ball-milling mixing processes on the synthesis kinetics were also studied. The synthesis kinetics of Ba1.0Co0.7Fe0.2Nb0.1O3-δ from the BaCO3 and Co3O4/Fe2O3/Nb2O5 particles was calculated by applying the modified model. The results indicated that the overall reaction process was considered involving two stages: addition reaction between BaCO3 and Co3O4/Fe2O3/Nb2O5 particles in the first stage and solution reaction between BaCoO3, BaFeO3, and BaNbO3 to form a homogeneous Ba1.0Co0.7Fe0.2Nb0.1O3-δ phase in the second stage. The new model matched well with the experimental data. The apparent activation energy of addition reaction stage of the high speed agitating mixing sample was estimated to be 376.76 kJ·mol-1, which was only 3/4 of that of the ball-milling mixing sample (494.76 kJ·mol-1). These results indicated that the high-speed agitating process could enhance atomic diffusion and facilitate the subsequent reaction, thus it is believed as a more effective, energy saving, and environmentally benign mixing process.
2008, 24(05): 772-780
doi: 10.1016/S1872-1508(08)60034-0
Abstract:
The fuzzy symmetry characteristics for the internal-rotation of propadine were analyzed using the fuzzy symmetry theory for molecule and molecular orbital (MO). In the process of rotation, three different symmetry point groups D2h, D2d, and D2 were considered. Using the D4h point group, which is the minimal point group including all symmetry elements of D2h, D2d, and D2, we can analyze the fuzzy symmetry for this process. The elements included in D4h point group can be classified to four subsets of (i) G0——it includes all the elements in D2 point group, also belongs to all the above three point groups of D2h, D2d, and D2; (ii) G1——it includes the elements in D2h point group, but not in D2d point group; (iii) G2——it includes the elements in D2d point group, but not in D2h point group; (iv) G3——it includes the elements in D4h point group, but not in D2h or D2d point group. On the basis of the above four subsets, we analyzed the membership functions and the regularity of variation in MOs for the internal-rotation of propadine.
The fuzzy symmetry characteristics for the internal-rotation of propadine were analyzed using the fuzzy symmetry theory for molecule and molecular orbital (MO). In the process of rotation, three different symmetry point groups D2h, D2d, and D2 were considered. Using the D4h point group, which is the minimal point group including all symmetry elements of D2h, D2d, and D2, we can analyze the fuzzy symmetry for this process. The elements included in D4h point group can be classified to four subsets of (i) G0——it includes all the elements in D2 point group, also belongs to all the above three point groups of D2h, D2d, and D2; (ii) G1——it includes the elements in D2h point group, but not in D2d point group; (iii) G2——it includes the elements in D2d point group, but not in D2h point group; (iv) G3——it includes the elements in D4h point group, but not in D2h or D2d point group. On the basis of the above four subsets, we analyzed the membership functions and the regularity of variation in MOs for the internal-rotation of propadine.
2008, 24(05): 781-787
doi: 10.3866/PKU.WHXB20080508
Abstract:
Multi-twinned silver nanoparticles and nanowires were synthesized by polyol process in the presence of surfactant poly (vinyl pyrrolidone) (PVP) K30. In order to study the growth mechanism, silver nanowires were synthesized under various conditions by changing n(PVP)/n(AgNO3) and the state of agitation. A comparative study of these nanowires was performed by means of transmission electron microscopy (TEM) and optical absorption spectra. The results showed that there coexisted two different growth modes, and hence the competition between them. According to one mode, the as-synthesized nanowires grew along {111} faces, by which the penta nal pyramid-shaped tip was enclosed, as the active facets. By another mode, the nanowires grew layer by layer along{110} face, which was perpendicular to the wire axis [110], as the active facet. There weremany stacking faults and dislocations in the nanowires deformed plastically during the preparation of the nanowires. The fresh fracture surfaces of the nanowires were the favorable positions where the nucleation and growth of newly formed crystals might take place.
Multi-twinned silver nanoparticles and nanowires were synthesized by polyol process in the presence of surfactant poly (vinyl pyrrolidone) (PVP) K30. In order to study the growth mechanism, silver nanowires were synthesized under various conditions by changing n(PVP)/n(AgNO3) and the state of agitation. A comparative study of these nanowires was performed by means of transmission electron microscopy (TEM) and optical absorption spectra. The results showed that there coexisted two different growth modes, and hence the competition between them. According to one mode, the as-synthesized nanowires grew along {111} faces, by which the penta nal pyramid-shaped tip was enclosed, as the active facets. By another mode, the nanowires grew layer by layer along{110} face, which was perpendicular to the wire axis [110], as the active facet. There weremany stacking faults and dislocations in the nanowires deformed plastically during the preparation of the nanowires. The fresh fracture surfaces of the nanowires were the favorable positions where the nucleation and growth of newly formed crystals might take place.
2008, 24(05): 788-792
doi: 10.3866/PKU.WHXB20080509
Abstract:
Multi-body interaction and atomic charge transfer played essential roles in depicting the ionic-covalent bonds of Si—O systems. The limitations of 3-body terms in interatomic potentials for silica glass were analyzed according to molecular dynamics studies at high temperature, and it was found that pair-wise ionic potentials were better in simulating the microstructure evolution of silica glass than multi-body potentials. Moreover, the effects of atomic charge transfer on atomic self-diffusion were investigated, which showed that the activation temperature of atomic self-diffusion calculated with the Morse potential was lower than that calculated with the BKS potential due to the less atomic charge transfer in Morse potential. It was also found that the atomic self-diffusion coefficients calculated increased with the decrease in atomic charge transfer at the same temperature. Therefore, the pair-wise potentials with less atomic charge transfer should be in favor of investigating the dynamic properties of silica glass at high temperature.
Multi-body interaction and atomic charge transfer played essential roles in depicting the ionic-covalent bonds of Si—O systems. The limitations of 3-body terms in interatomic potentials for silica glass were analyzed according to molecular dynamics studies at high temperature, and it was found that pair-wise ionic potentials were better in simulating the microstructure evolution of silica glass than multi-body potentials. Moreover, the effects of atomic charge transfer on atomic self-diffusion were investigated, which showed that the activation temperature of atomic self-diffusion calculated with the Morse potential was lower than that calculated with the BKS potential due to the less atomic charge transfer in Morse potential. It was also found that the atomic self-diffusion coefficients calculated increased with the decrease in atomic charge transfer at the same temperature. Therefore, the pair-wise potentials with less atomic charge transfer should be in favor of investigating the dynamic properties of silica glass at high temperature.
2008, 24(05): 793-798
doi: 10.1016/S1872-1508(08)60035-2
Abstract:
Aligned Zn1-xMgxO nanowire arrays were successfully prepared on Si(111) substrates via the chemical vapor deposition (CVD) method with a mixture of ZnO, Mg, and activated carbon powders as reactants. The microstructures and optical properties of the synthesized Zn1-xMgxO nanowire arrays were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis X-ray (EDAX), and photoluminescence (PL) spectrum analytic apparatus, respectively. While Mg content was achieved or less approximately 0.29 (x, atomic ratio) in ZnO lattice, the crystal lattice of the synthesized samples exhibited wurtzite structure. The Mg atoms were distributed into the ZnO crystal as the interstitial and displaced atoms, and there was no phase separation in preparing Zn1-xMgxO nanowire arrays. However, as the Mg content was up to 0.53 (x) in the fabricated Zn1-xMgxO samples, a clear phase separation phenomena appeared in the Zn1-xMgxO crystal. Compared with the PL spectrum of the pure ZnO nanowire arrays, the analytic results showed that a blue-shift of the near-band edge emission with increasing Mg content was observed in the Zn1-xMgxO arrays. And the relative intensities of green peak at ca 535 nm and UV emission peak at ca 376 nmwere all restrained.
Aligned Zn1-xMgxO nanowire arrays were successfully prepared on Si(111) substrates via the chemical vapor deposition (CVD) method with a mixture of ZnO, Mg, and activated carbon powders as reactants. The microstructures and optical properties of the synthesized Zn1-xMgxO nanowire arrays were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis X-ray (EDAX), and photoluminescence (PL) spectrum analytic apparatus, respectively. While Mg content was achieved or less approximately 0.29 (x, atomic ratio) in ZnO lattice, the crystal lattice of the synthesized samples exhibited wurtzite structure. The Mg atoms were distributed into the ZnO crystal as the interstitial and displaced atoms, and there was no phase separation in preparing Zn1-xMgxO nanowire arrays. However, as the Mg content was up to 0.53 (x) in the fabricated Zn1-xMgxO samples, a clear phase separation phenomena appeared in the Zn1-xMgxO crystal. Compared with the PL spectrum of the pure ZnO nanowire arrays, the analytic results showed that a blue-shift of the near-band edge emission with increasing Mg content was observed in the Zn1-xMgxO arrays. And the relative intensities of green peak at ca 535 nm and UV emission peak at ca 376 nmwere all restrained.
2008, 24(05): 799-804
doi: 10.3866/PKU.WHXB20080511
Abstract:
Two synthetical ashless phosphorus/sulfur-containing compouds were used as additives in biodegradable rapeseed oil (RSO). Their anti-wear and friction-reduction performances as lubricating oil additives were evaluated using four-ball tester. The chemistry of their tribofilms and thermal films was analyzed with X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES), The results showed that the two phosphorus/sulfur-containing compounds possessed rather od anti-wear properties and friction-reducing performances. According to the XPS and XANES analytic results, the tribofilms and thermal films generated from the additives were mainly composed of adsorbed-film and reaction film, in which phosphate and pyrophosphate were main existence form of P, FeSO4 was the main existence form of S. The results also showed that tribo-heat played different roles in the formation of tribofilms generated fromthe two different additives.
Two synthetical ashless phosphorus/sulfur-containing compouds were used as additives in biodegradable rapeseed oil (RSO). Their anti-wear and friction-reduction performances as lubricating oil additives were evaluated using four-ball tester. The chemistry of their tribofilms and thermal films was analyzed with X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES), The results showed that the two phosphorus/sulfur-containing compounds possessed rather od anti-wear properties and friction-reducing performances. According to the XPS and XANES analytic results, the tribofilms and thermal films generated from the additives were mainly composed of adsorbed-film and reaction film, in which phosphate and pyrophosphate were main existence form of P, FeSO4 was the main existence form of S. The results also showed that tribo-heat played different roles in the formation of tribofilms generated fromthe two different additives.
2008, 24(05): 805-809
doi: 10.3866/PKU.WHXB20080512
Abstract:
Photoelectrochemical and AC impedance measurements were conducted to study the effects of environment-friendly inhibitors poly-aspartate(PASP), Na2WO4 and their complex on the corrosion of cupronickel B10 in a borax-buffer solution. The photoelectrochemical measurement results indicated that PASP or Na2WO4 increased the p-type photocurrent which came fromthe Cu2O layer on the B10 surface. It showed that the inhibitors increased the thickness of the Cu2O layer and decreased the corrosion speed. The optimal concentrations of PASP and Na2WO4 was 3 and 5 mg·L-1, respectively. Na2WO4 increased photocurrent more than mono PASP did. Combined use of PASP and Na2WO4 in a total concentration of 5 mg·L-1, when the mass ratio(PASP: Na2WO4) was 1:1 or 1:3, increased the photocurrent more than their individual use did. The bigger the photocurrent was, the better the inhibition efficiency was. When the mass ratio (PASP: Na2WO4) was 3:1, the combined use increased photocurrent less than their individual use did, the inhibition effect decreased. AC impedance measurement results were well agreed to the photo-electrochemical results.
Photoelectrochemical and AC impedance measurements were conducted to study the effects of environment-friendly inhibitors poly-aspartate(PASP), Na2WO4 and their complex on the corrosion of cupronickel B10 in a borax-buffer solution. The photoelectrochemical measurement results indicated that PASP or Na2WO4 increased the p-type photocurrent which came fromthe Cu2O layer on the B10 surface. It showed that the inhibitors increased the thickness of the Cu2O layer and decreased the corrosion speed. The optimal concentrations of PASP and Na2WO4 was 3 and 5 mg·L-1, respectively. Na2WO4 increased photocurrent more than mono PASP did. Combined use of PASP and Na2WO4 in a total concentration of 5 mg·L-1, when the mass ratio(PASP: Na2WO4) was 1:1 or 1:3, increased the photocurrent more than their individual use did. The bigger the photocurrent was, the better the inhibition efficiency was. When the mass ratio (PASP: Na2WO4) was 3:1, the combined use increased photocurrent less than their individual use did, the inhibition effect decreased. AC impedance measurement results were well agreed to the photo-electrochemical results.
2008, 24(05): 810-816
doi: 10.1016/S1872-1508(08)60036-4
Abstract:
Kinetics of D-mannose oxidation by cerium (IV) was studied in a sulfuric acid medium at 40 ℃ both in absence and presence of ionic micelles. In both cases, the rate of the reaction was first-order in D-mannose and in cerium (IV), which decreased with increasing [H2SO4]. This suggested that the redox reaction followed the same mechanism. The reaction proceeded through formation of an intermediate complex, which was proved by kinetic method. The complex underwent slow unimolecular decomposition to a free radical that reacted with cerium (IV) to afford the product. The catalytic role of cationic cetyltrimethylammonium bromide (CTAB) micelles was best explained by the Menger-Portnoy model. The study of the effect of CTAB also indicated that a negatively charged species was reactive form of cerium (IV). From the kinetic data, micelle-cerium (IV) binding and rate constants in micellar medium were evaluated. The anionic micelle of sodiumdodecyl sulfate plays no catalytic role. The oxidation has the rate expression: -d[Ce(IV)]=k1Kc1[D-mannose][Ce(IV)]dt Different activation parameters for micelle catalyzed and uncatalyzed paths were also calculated and discussed.
Kinetics of D-mannose oxidation by cerium (IV) was studied in a sulfuric acid medium at 40 ℃ both in absence and presence of ionic micelles. In both cases, the rate of the reaction was first-order in D-mannose and in cerium (IV), which decreased with increasing [H2SO4]. This suggested that the redox reaction followed the same mechanism. The reaction proceeded through formation of an intermediate complex, which was proved by kinetic method. The complex underwent slow unimolecular decomposition to a free radical that reacted with cerium (IV) to afford the product. The catalytic role of cationic cetyltrimethylammonium bromide (CTAB) micelles was best explained by the Menger-Portnoy model. The study of the effect of CTAB also indicated that a negatively charged species was reactive form of cerium (IV). From the kinetic data, micelle-cerium (IV) binding and rate constants in micellar medium were evaluated. The anionic micelle of sodiumdodecyl sulfate plays no catalytic role. The oxidation has the rate expression: -d[Ce(IV)]=k1Kc1[D-mannose][Ce(IV)]dt Different activation parameters for micelle catalyzed and uncatalyzed paths were also calculated and discussed.
2008, 24(05): 817-822
doi: 10.3866/PKU.WHXB20080514
Abstract:
The crystallization of nano TiO2 prepared by adsorption phase reaction technique and the influence of crystallization on photo-catalytic activity of TiO2 were explored. XRD was employed to study the change of crystalline form and gain size of TiO2 under different sintering temperatures and times. The results indicated that there was also pure anatase TiO2 in samples, even when the sintering temperature reached 900 ℃. With increase of sintering temperature, grain size of TiO2 was below 7 nm and changed little. Whereas the peak area of anatase TiO2 increased with sintering temperature and remained unchanged when temperature reached 700 ℃. However change of sintering time influenced little on crystalline form and grain size of TiO2, so its photo-catalytic activity also changed little with sintering time increasing. Photo-degradation of gaseous toluene indicated that the sample sintered under 700 ℃ had the highest photo-catalytic activity and its activity was better than P25.
The crystallization of nano TiO2 prepared by adsorption phase reaction technique and the influence of crystallization on photo-catalytic activity of TiO2 were explored. XRD was employed to study the change of crystalline form and gain size of TiO2 under different sintering temperatures and times. The results indicated that there was also pure anatase TiO2 in samples, even when the sintering temperature reached 900 ℃. With increase of sintering temperature, grain size of TiO2 was below 7 nm and changed little. Whereas the peak area of anatase TiO2 increased with sintering temperature and remained unchanged when temperature reached 700 ℃. However change of sintering time influenced little on crystalline form and grain size of TiO2, so its photo-catalytic activity also changed little with sintering time increasing. Photo-degradation of gaseous toluene indicated that the sample sintered under 700 ℃ had the highest photo-catalytic activity and its activity was better than P25.
2008, 24(05): 823-826
doi: 10.3866/PKU.WHXB20080515
Abstract:
We extended the Davidson method, which was used to solve the standard eigenvalue problem, to solve the generalized eigenvalue problem and proposed the corresponding block iterative al rithm. Through theoretical analysis and numerical calculation, we found that the block iterative al rithm was doomed to converge after finite iterations if the process of iteration was not divergent. If the dimension of the matrix is n, the number of the eigenvalues and corresponding eigenvectors to be calculated is k, the size of the initial subspace is r(r≥k), the number of iteration is m, then they will fit in with the equation n=r+km. The positive integer root m could be obtained by regulating the size of the subspace.
We extended the Davidson method, which was used to solve the standard eigenvalue problem, to solve the generalized eigenvalue problem and proposed the corresponding block iterative al rithm. Through theoretical analysis and numerical calculation, we found that the block iterative al rithm was doomed to converge after finite iterations if the process of iteration was not divergent. If the dimension of the matrix is n, the number of the eigenvalues and corresponding eigenvectors to be calculated is k, the size of the initial subspace is r(r≥k), the number of iteration is m, then they will fit in with the equation n=r+km. The positive integer root m could be obtained by regulating the size of the subspace.
2008, 24(05): 827-832
doi: 10.3866/PKU.WHXB20080516
Abstract:
To investigate physical chemical behaviors of dielectric barrier discharge at atmospheric pressure in oxygen, the chemical active species which might exist in plasma were analyzed with the diagnosis technique of optical emission spectroscopy (OES) in oxygen discharge system. Fromthe oxygen atom emission spectra in 500-950 nm, the electronic temperature was calculated by some atomic lines to be (1.02±0.03) eV. The oxygen atmospheric band O2 (b1∑+g-X3∑-g) in 760 nm was analyzed, and the rotational temperature (gas temperature) was calculated by its rotational structure to be (650±20) K. The first negative system O+2(b4∑-g-a4∏u) in 500-700 nm and the Hopfield system O+2 (c4∑+u-b4∑-g) in 190-240 nm were observed. The research showed that there were various reactive species in plasma of dielectric barrier discharge at atmospheric pressure in oxygen, such as a series excited oxygen atoms, excited oxygen molecules, ground and excited states of oxygen molecular ions. The formation of reactive species concerned many procedures of excitation, dissociation and ionization of oxygen, many energy transfer steps were included in every procedure. The oxygen atoms produced from oxygen molecule dissociation were ruling factor leading to generate reactive species besides electron.
To investigate physical chemical behaviors of dielectric barrier discharge at atmospheric pressure in oxygen, the chemical active species which might exist in plasma were analyzed with the diagnosis technique of optical emission spectroscopy (OES) in oxygen discharge system. Fromthe oxygen atom emission spectra in 500-950 nm, the electronic temperature was calculated by some atomic lines to be (1.02±0.03) eV. The oxygen atmospheric band O2 (b1∑+g-X3∑-g) in 760 nm was analyzed, and the rotational temperature (gas temperature) was calculated by its rotational structure to be (650±20) K. The first negative system O+2(b4∑-g-a4∏u) in 500-700 nm and the Hopfield system O+2 (c4∑+u-b4∑-g) in 190-240 nm were observed. The research showed that there were various reactive species in plasma of dielectric barrier discharge at atmospheric pressure in oxygen, such as a series excited oxygen atoms, excited oxygen molecules, ground and excited states of oxygen molecular ions. The formation of reactive species concerned many procedures of excitation, dissociation and ionization of oxygen, many energy transfer steps were included in every procedure. The oxygen atoms produced from oxygen molecule dissociation were ruling factor leading to generate reactive species besides electron.
2008, 24(05): 833-838
doi: 10.3866/PKU.WHXB20080517
Abstract:
The influences of zinc and manganese promoters on the structure and reaction behavior of CuFe catalyst for higher alcohol synthesis were investigated by N2 adsorption, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), in situ diffuse reflectance infrared spectroscopy (DRIFT) and CO+H2 reaction. It was found that the zinc additive suppressed the dispersion of active phases but improved their activation ability towards CO molecule due to the formation of a new spinel phase, ZnFe2O4. The presence of manganese showed a more favorable effect on the dispersion of active phases and then promoted the synergistic effect between copper and iron although the adsorption tendency towards CO declined due to the dilution effect of manganese. Compared with binary CuFe catalyst, CuZnFe catalyst had a higher activity with the decreasing of C2+OH selectivity, and CuFeMn catalyst showed improved total alcohol selectivity although both CO conversion and C2+OH selectivity decreased. The results of the doubly promoted CuFe catalyst evidently indicated the existence of synergistic effect between zinc and manganese, which modified the texture parameters, decreased the reduction temperature of Cu and altered the reduction behavior of Fe. More importantly, the abundance of CO adsorption on the CuFe catalyst was greatly increased due to the co-addition of zinc and manganese. Therefore, the overall catalytic performance of doubly promoted CuFe catalyst was superior to that of the single promoted CuFe catalyst.
The influences of zinc and manganese promoters on the structure and reaction behavior of CuFe catalyst for higher alcohol synthesis were investigated by N2 adsorption, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), in situ diffuse reflectance infrared spectroscopy (DRIFT) and CO+H2 reaction. It was found that the zinc additive suppressed the dispersion of active phases but improved their activation ability towards CO molecule due to the formation of a new spinel phase, ZnFe2O4. The presence of manganese showed a more favorable effect on the dispersion of active phases and then promoted the synergistic effect between copper and iron although the adsorption tendency towards CO declined due to the dilution effect of manganese. Compared with binary CuFe catalyst, CuZnFe catalyst had a higher activity with the decreasing of C2+OH selectivity, and CuFeMn catalyst showed improved total alcohol selectivity although both CO conversion and C2+OH selectivity decreased. The results of the doubly promoted CuFe catalyst evidently indicated the existence of synergistic effect between zinc and manganese, which modified the texture parameters, decreased the reduction temperature of Cu and altered the reduction behavior of Fe. More importantly, the abundance of CO adsorption on the CuFe catalyst was greatly increased due to the co-addition of zinc and manganese. Therefore, the overall catalytic performance of doubly promoted CuFe catalyst was superior to that of the single promoted CuFe catalyst.
2008, 24(05): 839-843
doi: 10.1016/S1872-1508(08)60037-6
Abstract:
The influence of hierarchical porosity on electrocatalytic property was investigated with Pt nanoparticles supported on three types of carbon materials, namely, commercial Vulcan XC-72, ordered mesoporous carbon CMK-5, and hierarchical carbon aerogel (HCA). The electrocatalytic activity of carbon supported Pt nanoparticles was verified by cyclic voltammetry in H2SO4 and CH3OH solution. Pt/HCA presented superior performance with higher peak current (7.5 mA·cm-2) and electrochemical active area (128.0 m2·g-1). This could be attributed to the carbon aerogel with continuous but nonperiodical mesopore structure, which facilitated dispersion of Pt nanoparticles and mass transport around reactants and products.
The influence of hierarchical porosity on electrocatalytic property was investigated with Pt nanoparticles supported on three types of carbon materials, namely, commercial Vulcan XC-72, ordered mesoporous carbon CMK-5, and hierarchical carbon aerogel (HCA). The electrocatalytic activity of carbon supported Pt nanoparticles was verified by cyclic voltammetry in H2SO4 and CH3OH solution. Pt/HCA presented superior performance with higher peak current (7.5 mA·cm-2) and electrochemical active area (128.0 m2·g-1). This could be attributed to the carbon aerogel with continuous but nonperiodical mesopore structure, which facilitated dispersion of Pt nanoparticles and mass transport around reactants and products.
2008, 24(05): 844-848
doi: 10.3866/PKU.WHXB20080519
Abstract:
The Photodissociation dynamics of C6H11Br was investigated near 234 nm. A two-dimensional photofragment ion-velocity imaging technique coupled with a (2+1) resonance-enhancedmultiphoton (REMPI) ionization scheme was utilized to obtain the angular and translational energy distributions of the nascent Br(2P3/2) and Br*(2P1/2) atoms. The relative quantum yields were obtained from (2+1) resonance-enhanced multiphoton ionization (REMPI) of the photofragment Br*(2P1/2) and Br(2P3/2). It was suggested that Br* came fromthe direct dissociation of S1 state mostly, while Br atom was produced by non-adiabatic transition between the S2 and T3 states. Consequently, the higher internal energy distribution and the broader translational energy distribution of Br channel than those of Br* formation channel can be explained well. The results indicated that a large fraction of the available energy translated into the internal energy of the fragments, which can be explained using the soft impulsive model. However, comparing with other long-chain bromoalkane, more available energy was translated into the kinetic energy. The relationship between the energy partition and the cyclohexyl radical structure were analyzed.
The Photodissociation dynamics of C6H11Br was investigated near 234 nm. A two-dimensional photofragment ion-velocity imaging technique coupled with a (2+1) resonance-enhancedmultiphoton (REMPI) ionization scheme was utilized to obtain the angular and translational energy distributions of the nascent Br(2P3/2) and Br*(2P1/2) atoms. The relative quantum yields were obtained from (2+1) resonance-enhanced multiphoton ionization (REMPI) of the photofragment Br*(2P1/2) and Br(2P3/2). It was suggested that Br* came fromthe direct dissociation of S1 state mostly, while Br atom was produced by non-adiabatic transition between the S2 and T3 states. Consequently, the higher internal energy distribution and the broader translational energy distribution of Br channel than those of Br* formation channel can be explained well. The results indicated that a large fraction of the available energy translated into the internal energy of the fragments, which can be explained using the soft impulsive model. However, comparing with other long-chain bromoalkane, more available energy was translated into the kinetic energy. The relationship between the energy partition and the cyclohexyl radical structure were analyzed.
2008, 24(05): 849-854
doi: 10.3866/PKU.WHXB20080520
Abstract:
Perovskite type oxides supported nickel catalysts NiO/LaMnO3 were prepared by citric-complexing and impregnation method and used for H2 production by steam reforming of ethanol. The influence of nickel content and the calcination temperature on the catalytic performance was investigated. The catalysts were characterized by temperature programmed reduction (TPR), X-ray diffraction (XRD), and thermal analysis techniques. The catalysts showed very od catalytic performance. The NiO/LaMnO3 catalyst with NiO content of 15% (mass fraction, w) in catalysts and calcined at 700 ℃ exhibited the highest activity. Nearly 100% conversion of ethanol was observed over this catalyst at reaction temperature of 400 ℃, in reaction mixtures of 20%(volume fraction, φ) C2H5OH+H2O and 80% (φ) N2 with a molar ratio of water and ethanol of 3:1 and at a gas hourly space velocity (QHSV) 80000 mL·h-1·g-1 cat. Bycombining catalytic performance and characterization results, it was proposed that the high activity was ascribed to the metal nickel reduced fromnickel ions in the lattice of perovskite type oxides.
Perovskite type oxides supported nickel catalysts NiO/LaMnO3 were prepared by citric-complexing and impregnation method and used for H2 production by steam reforming of ethanol. The influence of nickel content and the calcination temperature on the catalytic performance was investigated. The catalysts were characterized by temperature programmed reduction (TPR), X-ray diffraction (XRD), and thermal analysis techniques. The catalysts showed very od catalytic performance. The NiO/LaMnO3 catalyst with NiO content of 15% (mass fraction, w) in catalysts and calcined at 700 ℃ exhibited the highest activity. Nearly 100% conversion of ethanol was observed over this catalyst at reaction temperature of 400 ℃, in reaction mixtures of 20%(volume fraction, φ) C2H5OH+H2O and 80% (φ) N2 with a molar ratio of water and ethanol of 3:1 and at a gas hourly space velocity (QHSV) 80000 mL·h-1·g-1 cat. Bycombining catalytic performance and characterization results, it was proposed that the high activity was ascribed to the metal nickel reduced fromnickel ions in the lattice of perovskite type oxides.
2008, 24(05): 855-860
doi: 10.3866/PKU.WHXB20080521
Abstract:
Sulfonated poly(ether imide) (SPEI) and poly(ether sulfone) (PES) blend membranes for application in the direct methanol fuel cells (DMFC) were successfully prepared by solution blend technique. The structure and performance of the obtained blend membranes were characterized using TGA, AFM, and SEM. The results showed that the blend membranes had higher thermal stability, lower swelling property, and od mechanical strength both in dry and wet states at ambient conditions. The morphology of blend membranes showed that its structure became more compact than that of pure SPEI, which might lead to decrease the methanol diffusion. The proton conductivity and the methanol permeability were determined by A.C. impedance spectrometry and diaphragm diffusion, respectively. The results showed that the SPEI/PES (mass ratio of 50/50) membrane still exhibited adequate conductivity (5.5 mS·cm-1) for application as proton exchange membranes. Meanwhile, the methanol permeability of the blend membranes decreased dramatically and was only 5% of that of Nafion 112 membrane. This tremendous reduction of methanol crossover could indicate a potential feasibility as a promising electrolyte for DMFC.
Sulfonated poly(ether imide) (SPEI) and poly(ether sulfone) (PES) blend membranes for application in the direct methanol fuel cells (DMFC) were successfully prepared by solution blend technique. The structure and performance of the obtained blend membranes were characterized using TGA, AFM, and SEM. The results showed that the blend membranes had higher thermal stability, lower swelling property, and od mechanical strength both in dry and wet states at ambient conditions. The morphology of blend membranes showed that its structure became more compact than that of pure SPEI, which might lead to decrease the methanol diffusion. The proton conductivity and the methanol permeability were determined by A.C. impedance spectrometry and diaphragm diffusion, respectively. The results showed that the SPEI/PES (mass ratio of 50/50) membrane still exhibited adequate conductivity (5.5 mS·cm-1) for application as proton exchange membranes. Meanwhile, the methanol permeability of the blend membranes decreased dramatically and was only 5% of that of Nafion 112 membrane. This tremendous reduction of methanol crossover could indicate a potential feasibility as a promising electrolyte for DMFC.
2008, 24(05): 861-867
doi: 10.3866/PKU.WHXB20080522
Abstract:
The optimized stable (CH3)2S…HOO and (CH3)2O…HOO hydrogen bond complexes were found on the potential energy surface at B3LYP/6-311++G** level. The obvious red shifts of the H10-O11 stretch vibration in the two hydrogen bond complexes were obtained by frequency analysis, and the red shift values were 424.21 and 374.22 cm-1, respectively. The hydrogen bond of S1(O1)…H10 interaction energy were -24.68 and 31.01 kJ·mol-1, which was calculated with basis set superposition error (BSSE) and zero point vibrational energy (ZPVE) correction at MP2 level. Natural bond orbit (NBO) theory analysis showed that two kinds of charge transfer exist in (CH3)2S…HOO hydrogen bond complex: (1) LP(S1)1→σ*(H10-O11); (2) LP(S1)2→σ*(H10-O11), and the natural population of the σ*(H10-O11) increased by 37.27 me. Analo us charge transfers existed in (CH3)2O…HOO hydrogen bond complex. Bond order analysis with nature resonance theory (NRT) showed that H10-O11 bond order decreased both in (CH3)2S…HOO and (CH3)2O…HOO hydrogen bond complexes. This agreed with the charge transfer discussion and frequency analysis. The topological properties of the hydrogen bond structures were also investigated by the atom-in-molecules (AIM) theory, and the results showed that there exist bond critical points between S1(O1) and H10.
The optimized stable (CH3)2S…HOO and (CH3)2O…HOO hydrogen bond complexes were found on the potential energy surface at B3LYP/6-311++G** level. The obvious red shifts of the H10-O11 stretch vibration in the two hydrogen bond complexes were obtained by frequency analysis, and the red shift values were 424.21 and 374.22 cm-1, respectively. The hydrogen bond of S1(O1)…H10 interaction energy were -24.68 and 31.01 kJ·mol-1, which was calculated with basis set superposition error (BSSE) and zero point vibrational energy (ZPVE) correction at MP2 level. Natural bond orbit (NBO) theory analysis showed that two kinds of charge transfer exist in (CH3)2S…HOO hydrogen bond complex: (1) LP(S1)1→σ*(H10-O11); (2) LP(S1)2→σ*(H10-O11), and the natural population of the σ*(H10-O11) increased by 37.27 me. Analo us charge transfers existed in (CH3)2O…HOO hydrogen bond complex. Bond order analysis with nature resonance theory (NRT) showed that H10-O11 bond order decreased both in (CH3)2S…HOO and (CH3)2O…HOO hydrogen bond complexes. This agreed with the charge transfer discussion and frequency analysis. The topological properties of the hydrogen bond structures were also investigated by the atom-in-molecules (AIM) theory, and the results showed that there exist bond critical points between S1(O1) and H10.
2008, 24(05): 868-872
doi: 10.3866/PKU.WHXB20080523
Abstract:
Some newamino acid ionic liquids (ILs) derivedfromthreonine (Thr)were studied. The para-toluenesulfonic acid threonine and its methyl ester (ThrC1-TsOH) and ethyl ester (ThrC2-TsOH) derivatives were synthesized with one-step microwave synthesis method, and their physicochemical properties, including the IR spectra, melting points, and thermostability, were studied experimentally. Quantum chemistry calculations were also performed to study the influence of the esterification of cation on the melting point. Geometry optimizations on the single molecules of the Thr complex and its methyl and ethyl ester complexes in gas phase were performed with DFT B3LYP/6-311++G** method, and the vibration frequencies of each optimized molecule were analyzed at the same level method. The binding energies between ions were calculated and the basis set superposition error (BSSE) was corrected with counterpoise method (CP). It was found that the esterification of cation would weaken not only the intermolecular hydrogen bond interaction, but also the intramolecular interaction between ions obviously. And so the decrease of the melting point is caused by the two factors, and the weakenness of intramolecular interaction should be the main factor for the titled compound to be an ionic liquid.
Some newamino acid ionic liquids (ILs) derivedfromthreonine (Thr)were studied. The para-toluenesulfonic acid threonine and its methyl ester (ThrC1-TsOH) and ethyl ester (ThrC2-TsOH) derivatives were synthesized with one-step microwave synthesis method, and their physicochemical properties, including the IR spectra, melting points, and thermostability, were studied experimentally. Quantum chemistry calculations were also performed to study the influence of the esterification of cation on the melting point. Geometry optimizations on the single molecules of the Thr complex and its methyl and ethyl ester complexes in gas phase were performed with DFT B3LYP/6-311++G** method, and the vibration frequencies of each optimized molecule were analyzed at the same level method. The binding energies between ions were calculated and the basis set superposition error (BSSE) was corrected with counterpoise method (CP). It was found that the esterification of cation would weaken not only the intermolecular hydrogen bond interaction, but also the intramolecular interaction between ions obviously. And so the decrease of the melting point is caused by the two factors, and the weakenness of intramolecular interaction should be the main factor for the titled compound to be an ionic liquid.
2008, 24(05): 873-879
doi: 10.3866/PKU.WHXB20080524
Abstract:
Olivine LiFePO4 cathode materials were synthesized by a solid state method in an inert atmosphere. The thermal decomposition processes taking place in the solid state mixture of Li2CO3, FeC2O4·2H2O, and NH4H2PO4 were investigated using TG-DTA and XRD techniques. The dynamic study of the precursor was also investigated using TG-DTA at different heating rates. The decomposition proceeded through three well-defined steps while TG curves closely corresponded to the theoretical mass loss. The apparent activation energy of each stage was calculated using the Doyle-Ozawa and Kissinger methods. The calculated results were 134.3, 122.2, 173.2 kJ·mol-1 for Ozawa method and 102.4, 128.1, 145.3 kJ·mol -1 for Kissinger method. The coefficients of reaction order, frequency factor, and dynamic equations were also determined. Based on the results of the dynamic study, the cathode material LiFePO4 was synthesized by optimized step-sintering method. The crystal structure and the electrochemical performance were characterized by X-ray powder diffraction (XRD), scan electron microscopy (SEM), and galvanostatical charge-discharge testing. The results showed that the material had a single crystal olivine structure with homogeneous grain sizes, and exhibited excellent electrochemical performance at 0.1C rate.
Olivine LiFePO4 cathode materials were synthesized by a solid state method in an inert atmosphere. The thermal decomposition processes taking place in the solid state mixture of Li2CO3, FeC2O4·2H2O, and NH4H2PO4 were investigated using TG-DTA and XRD techniques. The dynamic study of the precursor was also investigated using TG-DTA at different heating rates. The decomposition proceeded through three well-defined steps while TG curves closely corresponded to the theoretical mass loss. The apparent activation energy of each stage was calculated using the Doyle-Ozawa and Kissinger methods. The calculated results were 134.3, 122.2, 173.2 kJ·mol-1 for Ozawa method and 102.4, 128.1, 145.3 kJ·mol -1 for Kissinger method. The coefficients of reaction order, frequency factor, and dynamic equations were also determined. Based on the results of the dynamic study, the cathode material LiFePO4 was synthesized by optimized step-sintering method. The crystal structure and the electrochemical performance were characterized by X-ray powder diffraction (XRD), scan electron microscopy (SEM), and galvanostatical charge-discharge testing. The results showed that the material had a single crystal olivine structure with homogeneous grain sizes, and exhibited excellent electrochemical performance at 0.1C rate.
2008, 24(05): 880-884
doi: 10.3866/PKU.WHXB20080525
Abstract:
According to the relationship between gravitational potential and electrostatic potential, and the physical meaning of the mass-to-electricity (mass of per unit electricity) Sr, the variation of ionic radius r with Sr and the phase difference factor of ion were studied. For positive ions, configuration the r varied directly with lgSr and the phase difference factor, and for negative ions with stable electronic configuration, the r varied quantitatively with as Sr and the phase difference factor. Calculating formulas for the positive ionic radius with stable and unstable electronic configurations, and the negative ionic radius with stable electronic configuration were obtained. The correlation coefficient R and test of significance (F) showed that r was closely relative to Sr and the phase difference factor. 138 radii of positive ions that contained 96 elements were fitted. The average absolute error of the 138 radii of positive ions was 2.0 pm compared with the representative radii of ions, and the relative error was 2.5%. 30 positive ionic radii of rare gases et al. were calculated by the formulas, and the calculated values were relatively reasonable. That was a new path of calculating the radi of ions, including complex ions.
According to the relationship between gravitational potential and electrostatic potential, and the physical meaning of the mass-to-electricity (mass of per unit electricity) Sr, the variation of ionic radius r with Sr and the phase difference factor of ion were studied. For positive ions, configuration the r varied directly with lgSr and the phase difference factor, and for negative ions with stable electronic configuration, the r varied quantitatively with as Sr and the phase difference factor. Calculating formulas for the positive ionic radius with stable and unstable electronic configurations, and the negative ionic radius with stable electronic configuration were obtained. The correlation coefficient R and test of significance (F) showed that r was closely relative to Sr and the phase difference factor. 138 radii of positive ions that contained 96 elements were fitted. The average absolute error of the 138 radii of positive ions was 2.0 pm compared with the representative radii of ions, and the relative error was 2.5%. 30 positive ionic radii of rare gases et al. were calculated by the formulas, and the calculated values were relatively reasonable. That was a new path of calculating the radi of ions, including complex ions.
2008, 24(05): 885-889
doi: 10.3866/PKU.WHXB20080526
Abstract:
An aqueous gel-casting of hydroxyapatite using a new polymeric system was investigated. The monomer, cross-linker, and initiator were dimethylacrylamide (DMAA), N,N’-methylenebisacrylamide (MBAM), and 2,2’-azobis [2-(2-imidazolin-2-yl)propane] (AZIP, respectively). The rheological properties of the gel-casting slurries and influencing factors were studied. The relative density, compressive strength, and flexural strength of green body were 57.5%, (37.0±6.5), and (13.8±1.0) MPa, respectively. After presureless sintering at 1250 ℃ for 2 h, the relative density of the final product is about 98.7%. Bending strength and elasticity modulus are (85.3±9.9) MPa and (133.0±10.2) GPa, respectively.
An aqueous gel-casting of hydroxyapatite using a new polymeric system was investigated. The monomer, cross-linker, and initiator were dimethylacrylamide (DMAA), N,N’-methylenebisacrylamide (MBAM), and 2,2’-azobis [2-(2-imidazolin-2-yl)propane] (AZIP, respectively). The rheological properties of the gel-casting slurries and influencing factors were studied. The relative density, compressive strength, and flexural strength of green body were 57.5%, (37.0±6.5), and (13.8±1.0) MPa, respectively. After presureless sintering at 1250 ℃ for 2 h, the relative density of the final product is about 98.7%. Bending strength and elasticity modulus are (85.3±9.9) MPa and (133.0±10.2) GPa, respectively.
2008, 24(05): 890-894
doi: 10.3866/PKU.WHXB20080527
Abstract:
Apparent molar volumes (Vφ) of myo-inositol in aqueous solutions of LiCl, NaCl, and KCl were obtained from densities, measured with a vibrating-tube densimeter, at 298.15 and 308.15 K. These data have been used to deduce limiting partial molar volumes Vθφ and limiting partial molar volumes of transfer ⊿trsVθφ from water to different salt solutions at different concentrations. The results indicated that influence of salt (LiCl, NaCl or KCl) on volumetric property of myo-inositol in aqueous solution was evident while temperature could only slightly change Vθφ and ⊿trsVθφ. The result was discussed in the light of interaction between the charged centers of myo-inositol and ions.
Apparent molar volumes (Vφ) of myo-inositol in aqueous solutions of LiCl, NaCl, and KCl were obtained from densities, measured with a vibrating-tube densimeter, at 298.15 and 308.15 K. These data have been used to deduce limiting partial molar volumes Vθφ and limiting partial molar volumes of transfer ⊿trsVθφ from water to different salt solutions at different concentrations. The results indicated that influence of salt (LiCl, NaCl or KCl) on volumetric property of myo-inositol in aqueous solution was evident while temperature could only slightly change Vθφ and ⊿trsVθφ. The result was discussed in the light of interaction between the charged centers of myo-inositol and ions.
2008, 24(05): 895-900
doi: 10.3866/PKU.WHXB20080528
Abstract:
Microbial-corrosion resistance of Cu-containing ferrite stainless steels after antibacterial treatment in heterotrophic bacteria culture medium was investigated by means of various electrochemical techniques and microbial methods. The results showed that corrosion potential changed orderly along with metabolism of heterotrophic bacteria. Antibacterial treatment helped to enhance the stability of passive film and reduce the pitting sensibility when stainless steel was immersed in culture medium. Dispersion distributed ε-Cu phase on the surface of antibacterial stainless steel depressed activity of heterotrophic bacteria, thereafter alleviated the heterotrophic bacteria corrosion and improved the microbiological corrosion resistance of antibacterial stainless steel.
Microbial-corrosion resistance of Cu-containing ferrite stainless steels after antibacterial treatment in heterotrophic bacteria culture medium was investigated by means of various electrochemical techniques and microbial methods. The results showed that corrosion potential changed orderly along with metabolism of heterotrophic bacteria. Antibacterial treatment helped to enhance the stability of passive film and reduce the pitting sensibility when stainless steel was immersed in culture medium. Dispersion distributed ε-Cu phase on the surface of antibacterial stainless steel depressed activity of heterotrophic bacteria, thereafter alleviated the heterotrophic bacteria corrosion and improved the microbiological corrosion resistance of antibacterial stainless steel.
2008, 24(05): 901-904
doi: 10.3866/PKU.WHXB20080529
Abstract:
The silylenoid H2SiClBeCl was studied using DFT B3LYP and QCISD methods. Geometry optimization calculations indicated that H2SiClBeCl had three equilibrium configurations, in which the tetrahedral structure was the lowest in energy and was the most stable structure. The transition states for isomerization reactions of H2SiClBeCl were located and the energy barriers were calculated. For the most stable one, the infrared spectrumhad been simulated.
The silylenoid H2SiClBeCl was studied using DFT B3LYP and QCISD methods. Geometry optimization calculations indicated that H2SiClBeCl had three equilibrium configurations, in which the tetrahedral structure was the lowest in energy and was the most stable structure. The transition states for isomerization reactions of H2SiClBeCl were located and the energy barriers were calculated. For the most stable one, the infrared spectrumhad been simulated.
2008, 24(05): 905-908
doi: 10.3866/PKU.WHXB20080530
Abstract:
The effect of annealing treatment on the photoelectric properties of poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was analyzed by UV-Vis absorption spectroscopy, photoluminescence (PL) spectroscopy, X-ray diffraction, and solar cell performance. The UV-Vis absorption peaks of P3HT:PCBM thin filmshowed enhancement and a red-shift after thermal annealing. PL and XRD peak intensities increased by annealing treatment. A solar cell based on the blend of P3HT:PCBM was fabricated, and the device performance was significantly improved by thermal annealing. For devices heat-treated at 130 益, open circuit voltage of 0.55 V, short circuit current density of 9.87 mA·cm-2, fill factor of 60.1% and power conversion efficiency (PCE) of 3.26% were achieved under 100 mW·cm-2 air-mass 1.5 solar simulator illumination.
The effect of annealing treatment on the photoelectric properties of poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was analyzed by UV-Vis absorption spectroscopy, photoluminescence (PL) spectroscopy, X-ray diffraction, and solar cell performance. The UV-Vis absorption peaks of P3HT:PCBM thin filmshowed enhancement and a red-shift after thermal annealing. PL and XRD peak intensities increased by annealing treatment. A solar cell based on the blend of P3HT:PCBM was fabricated, and the device performance was significantly improved by thermal annealing. For devices heat-treated at 130 益, open circuit voltage of 0.55 V, short circuit current density of 9.87 mA·cm-2, fill factor of 60.1% and power conversion efficiency (PCE) of 3.26% were achieved under 100 mW·cm-2 air-mass 1.5 solar simulator illumination.
2008, 24(05): 909-914
doi: 10.3866/PKU.WHXB20080531
Abstract:
A series of iridium-supported catalysts with various Ir loadings were prepared by impregnation method. The support materials used were ZSM-5, γ-Al2O3, and SiO2. The Ir loadings examined were 0.02%, 0.1%, 1%, and 5% (w). The behavior of the catalysts for the NO reaction was analyzed by means of temperature programmed reaction (TPR) experiments. The reactions of NO over iridium include the oxidation of NO to NO2 and the reduction of NO to N2 or N2O. The iridium catalysts promote the reactions of NO and the catalytic activity increases with the increase of the Ir loadings. Further, support materials have a little effect on the catalytic activity. When the loading was less than 0.1%, the catalytic activity was found to be dependent on the property of support materials and the activity order was Ir/ZSM-5>Ir/γ-Al2O3>Ir/SiO2; when the loading was higher than 0.1%, the order of catalytic activity for NO oxidation was Ir/ZSM-5>Ir/SiO2>Ir/γ-Al2O3, which was correlated with Ir dispersion on the surface of support materials, and the order of catalytic activity for NO reduction was Ir/γ-Al2O3>Ir/SiO2>Ir/ZSM-5, which was attributed to the adsorbed-dissociation of NO2. Ir/γ-Al2O3 catalyst was more beneficial for the NO reduction than Pt/γ-Al2O3 catalyst.
A series of iridium-supported catalysts with various Ir loadings were prepared by impregnation method. The support materials used were ZSM-5, γ-Al2O3, and SiO2. The Ir loadings examined were 0.02%, 0.1%, 1%, and 5% (w). The behavior of the catalysts for the NO reaction was analyzed by means of temperature programmed reaction (TPR) experiments. The reactions of NO over iridium include the oxidation of NO to NO2 and the reduction of NO to N2 or N2O. The iridium catalysts promote the reactions of NO and the catalytic activity increases with the increase of the Ir loadings. Further, support materials have a little effect on the catalytic activity. When the loading was less than 0.1%, the catalytic activity was found to be dependent on the property of support materials and the activity order was Ir/ZSM-5>Ir/γ-Al2O3>Ir/SiO2; when the loading was higher than 0.1%, the order of catalytic activity for NO oxidation was Ir/ZSM-5>Ir/SiO2>Ir/γ-Al2O3, which was correlated with Ir dispersion on the surface of support materials, and the order of catalytic activity for NO reduction was Ir/γ-Al2O3>Ir/SiO2>Ir/ZSM-5, which was attributed to the adsorbed-dissociation of NO2. Ir/γ-Al2O3 catalyst was more beneficial for the NO reduction than Pt/γ-Al2O3 catalyst.
2008, 24(05): 915-920
doi: 10.3866/PKU.WHXB20080532
Abstract:
Nano Pt/dimercaptosuccinic amide copper (II) (CuL) modified electrode (Au/CuL/nano Pt CME) was prepared by electrodepositing nano crystalline Pt on the surface of CuL monolayer, which was self-assembled on Au electrode (Au/CuL CME). The electrode’s electrochemical response was studied by cyclic voltammetry (CV) and its surface was characterized by scanning electron micrograph (SEM), atomic force microscope (AFM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectrum(XPS). The results indicated that the biosensor displayed excellent electrocatalytical response to the reduction of H2O2 in 0.02 mol·L-1 PBS(pH=6.0). The electrode responsed to H2O2 in the concentration range of 0.00125-0.16mmol·L-1with detection limit of 0.3 μmol·L-1 (signal/noise ratio was 3). Meanwhile, the electrode showed od sensitivity (0.312 mA·cm-2·mmol-1·L in amperometric measurements), rapid response time (4.3 s), and reproducibility for long-termuse (the variation coefficients were 3.1%and 3.9% (n=10) at 46 μmol·L-1 and 2.8 mmol·L-1 H2O2, respectively; the current maintained 95%for at least more than 70 days to 10 μmol·L-1 H2O2).
Nano Pt/dimercaptosuccinic amide copper (II) (CuL) modified electrode (Au/CuL/nano Pt CME) was prepared by electrodepositing nano crystalline Pt on the surface of CuL monolayer, which was self-assembled on Au electrode (Au/CuL CME). The electrode’s electrochemical response was studied by cyclic voltammetry (CV) and its surface was characterized by scanning electron micrograph (SEM), atomic force microscope (AFM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectrum(XPS). The results indicated that the biosensor displayed excellent electrocatalytical response to the reduction of H2O2 in 0.02 mol·L-1 PBS(pH=6.0). The electrode responsed to H2O2 in the concentration range of 0.00125-0.16mmol·L-1with detection limit of 0.3 μmol·L-1 (signal/noise ratio was 3). Meanwhile, the electrode showed od sensitivity (0.312 mA·cm-2·mmol-1·L in amperometric measurements), rapid response time (4.3 s), and reproducibility for long-termuse (the variation coefficients were 3.1%and 3.9% (n=10) at 46 μmol·L-1 and 2.8 mmol·L-1 H2O2, respectively; the current maintained 95%for at least more than 70 days to 10 μmol·L-1 H2O2).
2008, 24(05): 921-926
doi: 10.3866/PKU.WHXB20080533
Abstract:
The progress in combinatorial chemistry approach screening for new phosphors under vacuum ultraviolet excitation, including the technique of parallel synthesis and high through-put characterization of materials library, was summarized. The design of combinatorial library was introduced with a special emphasis. Finally, the practical example of the material system which has been optimized with combinatorial chemistry approach for plasma display panel phosphors were given in summarily.
The progress in combinatorial chemistry approach screening for new phosphors under vacuum ultraviolet excitation, including the technique of parallel synthesis and high through-put characterization of materials library, was summarized. The design of combinatorial library was introduced with a special emphasis. Finally, the practical example of the material system which has been optimized with combinatorial chemistry approach for plasma display panel phosphors were given in summarily.
