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2008 Volume 24 Issue 3
2008, 24(03):
Abstract:
2008, 24(03): 359-363
doi: 10.1016/S1872-1508(08)60014-5
Abstract:
Anionic polypeptide, the poly(sodium L-glutamate), was applied to fabricate microporous silica hollow nanospheres templated by the secondary structures of the polypeptide as porogens. In the synthesis, 3-aminopropyltrimethoxysilane (APMS) and tetraethyl orthosilicate (TEOS) were used as the silica sources, and the coassembly followed the mechanism of the anionic surfactant-templated mesoporous silica (AMS) through a S-N+-I pathway, where S indicates the anionic polypeptide, I indicates inorganic precursors (TEOS), and N indicates costructure-directing agent (APMS), which interacted with the negatively charged anionic polypeptide secondary structures electrostatically and cocondensed with silica source to form the silica framework. The product was subjected to characterizations of X-ray diffraction (XRD), infrared (IR) spectroscopy, thermogravimetric (TG) analysis, scanning electron microscopy (SEM), transmitted electron microscopy (TEM), and nitrogen adsorption-desorption measurement. It was found that the pH value of the synthesis solution was an important factor to the morphological control of the silica products. Besides the microporous hollow nanospheres, microporous submicron silica solid and hollow spheres were also obtained facilely by changing the synthesis parameters. Our study further implied that anionic polypeptides, which were able to control mineralization of calcium carbonate and calcium phosphate, could also induce silica condensation in the presence of proper silica precursors. It was also expected that functional calcium carbonate (phosphate)/silica-nanocomposite materials would be fabricated under the control of the anionic polypeptide.
Anionic polypeptide, the poly(sodium L-glutamate), was applied to fabricate microporous silica hollow nanospheres templated by the secondary structures of the polypeptide as porogens. In the synthesis, 3-aminopropyltrimethoxysilane (APMS) and tetraethyl orthosilicate (TEOS) were used as the silica sources, and the coassembly followed the mechanism of the anionic surfactant-templated mesoporous silica (AMS) through a S-N+-I pathway, where S indicates the anionic polypeptide, I indicates inorganic precursors (TEOS), and N indicates costructure-directing agent (APMS), which interacted with the negatively charged anionic polypeptide secondary structures electrostatically and cocondensed with silica source to form the silica framework. The product was subjected to characterizations of X-ray diffraction (XRD), infrared (IR) spectroscopy, thermogravimetric (TG) analysis, scanning electron microscopy (SEM), transmitted electron microscopy (TEM), and nitrogen adsorption-desorption measurement. It was found that the pH value of the synthesis solution was an important factor to the morphological control of the silica products. Besides the microporous hollow nanospheres, microporous submicron silica solid and hollow spheres were also obtained facilely by changing the synthesis parameters. Our study further implied that anionic polypeptides, which were able to control mineralization of calcium carbonate and calcium phosphate, could also induce silica condensation in the presence of proper silica precursors. It was also expected that functional calcium carbonate (phosphate)/silica-nanocomposite materials would be fabricated under the control of the anionic polypeptide.
2008, 24(03): 364-368
doi: 10.1016/S1872-1508(08)60015-7
Abstract:
The catalysts for the combustion of ethyl acetate were prepared using Fe, Co, Cu, Cr, andMn metal oxides as active components supported on Al2O3-Ce0.5Zr0.5O2 mixed oxides and characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), oxygen storage capacity measurement, BET surface area, XPS measurement, and activity test. According to the results of characterization, it was found that Cu/Al2O3-Ce0.5Zr0.5O2 (1:2, mass ratio) andMn/Al2O3-Ce0.5Zr0.5O2 (1:2) catalysts presented excellent activity for the catalytic combustion of ethyl acetate, because of the more reducible species and high reducibility of the catalysts. For ethyl acetate oxidation, more than 99% conversion was achieved at 245 ℃ over catalysts Cu/Al2O3-Ce0.5Zr0.5O2 (1:2) and Mn/Al2O3-Ce0.5Zr0.5O2 (1:2, mass ratio), indicating that the catalysts had great potential for wide use.
The catalysts for the combustion of ethyl acetate were prepared using Fe, Co, Cu, Cr, andMn metal oxides as active components supported on Al2O3-Ce0.5Zr0.5O2 mixed oxides and characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), oxygen storage capacity measurement, BET surface area, XPS measurement, and activity test. According to the results of characterization, it was found that Cu/Al2O3-Ce0.5Zr0.5O2 (1:2, mass ratio) andMn/Al2O3-Ce0.5Zr0.5O2 (1:2) catalysts presented excellent activity for the catalytic combustion of ethyl acetate, because of the more reducible species and high reducibility of the catalysts. For ethyl acetate oxidation, more than 99% conversion was achieved at 245 ℃ over catalysts Cu/Al2O3-Ce0.5Zr0.5O2 (1:2) and Mn/Al2O3-Ce0.5Zr0.5O2 (1:2, mass ratio), indicating that the catalysts had great potential for wide use.
2008, 24(03): 369-374
doi: 10.1016/S1872-1508(08)60016-9
Abstract:
It was found that Si-MCM-41 mesoporous molecular sieves as a support of noble metal Pt could be used for the selective catalytic reduction of NO by hydrogen (H2-SCR) under lean-burn conditions. Pt/Si-MCM-41, together with Pt/Si-ZSM-5 and Pt/SiO2, was characterized by X-ray diffraction analysis (XRD), nitrogen adsorption/desorption, hydrogen adsorption, and transmission electron microscopy (TEM). The results indicated that Pt/Si-MCM-41 had the best H2-SCR activity in comparison with Pt/Si-ZSM-5 and Pt/SiO2 catalysts and that the maximum conversion of NO was up to 60.1%at 100 ℃ and a gas hourly space velocity (GHSV) of 80000 h-1 under lean-burn conditions. Characterization showed that the large surface area and pore volume of MCM-41 favored the dispersion of Pt. The maximum NO conversion of Pt/Si-MCM-41 catalyst decreased obviously to 15% at 120 ℃ when the pore structure of Si-MCM-41 support was destroyed. The reaction mechanism over Pt/Si-MCM-41 was investigated using in situ diffuse reflectance infrared spectroscopy (DRIFTS), which revealed that the main reaction intermediates should be nitrate species during NO reduction.
It was found that Si-MCM-41 mesoporous molecular sieves as a support of noble metal Pt could be used for the selective catalytic reduction of NO by hydrogen (H2-SCR) under lean-burn conditions. Pt/Si-MCM-41, together with Pt/Si-ZSM-5 and Pt/SiO2, was characterized by X-ray diffraction analysis (XRD), nitrogen adsorption/desorption, hydrogen adsorption, and transmission electron microscopy (TEM). The results indicated that Pt/Si-MCM-41 had the best H2-SCR activity in comparison with Pt/Si-ZSM-5 and Pt/SiO2 catalysts and that the maximum conversion of NO was up to 60.1%at 100 ℃ and a gas hourly space velocity (GHSV) of 80000 h-1 under lean-burn conditions. Characterization showed that the large surface area and pore volume of MCM-41 favored the dispersion of Pt. The maximum NO conversion of Pt/Si-MCM-41 catalyst decreased obviously to 15% at 120 ℃ when the pore structure of Si-MCM-41 support was destroyed. The reaction mechanism over Pt/Si-MCM-41 was investigated using in situ diffuse reflectance infrared spectroscopy (DRIFTS), which revealed that the main reaction intermediates should be nitrate species during NO reduction.
2008, 24(03): 375-378
doi: 10.1016/S1872-1508(08)60017-0
Abstract:
The nanocrystalline LaCoxFe1 -xO3 with different concentrations of Co was prepared by polyethylene glycol (PEG) sol-gel method and characterized by differential thermal analysis and thermal gravimetric analysis (DTA-TGA), X-ray diffraction (XRD), and scanning electron microscope (SEM). It was found that the crystal structure of perovskite-type could be obtained at 600 ℃, and the concentration of Co had significant effects on the solid-state reaction and the average particle size of the obtained nanocrystals. Furthermore, the humidity-sensitive properties of nanocrystalline LaCoxFe1 -xO3 were investigated, and it was found that LaCo0.3Fe0.7O3 exhibited higher sensitivity to humidity compared with other samples. The addition of Na2CO3 improved the humidity-sensitive properties of this sample, and made its response to humidity od in the whole humidity range of 11%-95%relative humidity (RH).
The nanocrystalline LaCoxFe1 -xO3 with different concentrations of Co was prepared by polyethylene glycol (PEG) sol-gel method and characterized by differential thermal analysis and thermal gravimetric analysis (DTA-TGA), X-ray diffraction (XRD), and scanning electron microscope (SEM). It was found that the crystal structure of perovskite-type could be obtained at 600 ℃, and the concentration of Co had significant effects on the solid-state reaction and the average particle size of the obtained nanocrystals. Furthermore, the humidity-sensitive properties of nanocrystalline LaCoxFe1 -xO3 were investigated, and it was found that LaCo0.3Fe0.7O3 exhibited higher sensitivity to humidity compared with other samples. The addition of Na2CO3 improved the humidity-sensitive properties of this sample, and made its response to humidity od in the whole humidity range of 11%-95%relative humidity (RH).
2008, 24(03): 379-387
doi: 10.1016/S1872-1508(08)60018-2
Abstract:
Fluorescence quenching and synchronous fluorescence methods were used to study the interactions of fluorescence-active quercetin (Qct) with casein (Cas) and bovine serum albumin (BSA) in phosphate buffer solution (PBS, pH=7.4) with or without coexisting carbon nanotubes (CNTs). Formulae for binding constant (K) and molar binding ratio (n)were established formethods 1 (fixing protein concentration, changing Qct concentration, andmonitoring the fluorescence of protein) and 2 (fixing Qct concentration, changing protein concentration, and monitoring the fluorescence of Qct), to which values of K and n were calculated via nonlinear least-square fitting of the experimental data, and the“optical inner filtering induced fluorescence quenching”effect was thus quantitatively evaluated. The quenching effects of coexisting CNTs on the fluorescence of Qct, BSA, and Cas, as well as the effects of coexisting CNTs on Qct-BSA and Qct-Cas interactions, were examined. Synchronous fluorescence was also used to examine the effects of coexisting CNTs and Qct on conformations of BSA and Cas, with relevant K and n values for tyrosine (Tyr) and tryptophan (Trp) residues estimated. It was concluded that the CNTs mainly interact with the Trp residues locating near the protein surfaces, but small-sized Qct molecules could further interact with the Tyr residues locating inside the protein molecules.
Fluorescence quenching and synchronous fluorescence methods were used to study the interactions of fluorescence-active quercetin (Qct) with casein (Cas) and bovine serum albumin (BSA) in phosphate buffer solution (PBS, pH=7.4) with or without coexisting carbon nanotubes (CNTs). Formulae for binding constant (K) and molar binding ratio (n)were established formethods 1 (fixing protein concentration, changing Qct concentration, andmonitoring the fluorescence of protein) and 2 (fixing Qct concentration, changing protein concentration, and monitoring the fluorescence of Qct), to which values of K and n were calculated via nonlinear least-square fitting of the experimental data, and the“optical inner filtering induced fluorescence quenching”effect was thus quantitatively evaluated. The quenching effects of coexisting CNTs on the fluorescence of Qct, BSA, and Cas, as well as the effects of coexisting CNTs on Qct-BSA and Qct-Cas interactions, were examined. Synchronous fluorescence was also used to examine the effects of coexisting CNTs and Qct on conformations of BSA and Cas, with relevant K and n values for tyrosine (Tyr) and tryptophan (Trp) residues estimated. It was concluded that the CNTs mainly interact with the Trp residues locating near the protein surfaces, but small-sized Qct molecules could further interact with the Tyr residues locating inside the protein molecules.
2008, 24(03): 388-392
doi: 10.1016/S1872-1508(08)60019-4
Abstract:
The equilibrium structure, electronic structure, and formation heat of Pu3M (PuM3) (M=Ga, In, Sn and Ge) compounds with AuCu3 structure have been calculated using full potential linear augmented plane wave (FPLAPW) method with generalized-gradient approximation (GGA) including spin-orbit coupling (SOC) and spin polarized (SP). The calculated lattice parameters are in od agreement with experimental values.Density of state analysis shows hybridization effects between Pu andMare verned by the competitions depending on the M amount: Pu 6d-Pu 5f, M p-Pu 6d, and M sp-M sp interactions. Electronegativity difference and electronic hybridization effect are two important factors to influence the formation heat and stability of Pu3M(PuM3) compounds. The larger the electronegativity difference and the lower the M s-band or p-band center relative to the Fermi heat, the more negative is the formation energy and the more stable are Pu3M(PuM3) compounds.
The equilibrium structure, electronic structure, and formation heat of Pu3M (PuM3) (M=Ga, In, Sn and Ge) compounds with AuCu3 structure have been calculated using full potential linear augmented plane wave (FPLAPW) method with generalized-gradient approximation (GGA) including spin-orbit coupling (SOC) and spin polarized (SP). The calculated lattice parameters are in od agreement with experimental values.Density of state analysis shows hybridization effects between Pu andMare verned by the competitions depending on the M amount: Pu 6d-Pu 5f, M p-Pu 6d, and M sp-M sp interactions. Electronegativity difference and electronic hybridization effect are two important factors to influence the formation heat and stability of Pu3M(PuM3) compounds. The larger the electronegativity difference and the lower the M s-band or p-band center relative to the Fermi heat, the more negative is the formation energy and the more stable are Pu3M(PuM3) compounds.
2008, 24(03): 393-399
doi: 10.3866/PKU.WHXB20080307
Abstract:
The corrosion morphology, the corrosion film composition, and corrosion electrochemical characteristics of X60 steel soaking in CO2 and sulfate reducing bacteria (SRB) coexistence environment for different times were investigated respectively. Results showed that the potential of X60 steel increased with the increase of biofilm covering extent, and then decreased with the increase of the content of corrosion product FeS and FeCO3. According to the analytical results of EIS, only a time constant related to electrode potential existed when the content of corrosion product in the film forming on the surface of X60 steel was low, and then an additional time constant related to the corrosion film appeared with the increase of the content of corrosion product in the film. The transferring resistance increased with the increase of the covering extend of biofilm in the early soaking stage. And then the transferring resistance first decreased, and then increased with the increase of the content of corrosion product. With the increase of soaking time, both electrical double-layer capacitance and filmcapacitance increased.
The corrosion morphology, the corrosion film composition, and corrosion electrochemical characteristics of X60 steel soaking in CO2 and sulfate reducing bacteria (SRB) coexistence environment for different times were investigated respectively. Results showed that the potential of X60 steel increased with the increase of biofilm covering extent, and then decreased with the increase of the content of corrosion product FeS and FeCO3. According to the analytical results of EIS, only a time constant related to electrode potential existed when the content of corrosion product in the film forming on the surface of X60 steel was low, and then an additional time constant related to the corrosion film appeared with the increase of the content of corrosion product in the film. The transferring resistance increased with the increase of the covering extend of biofilm in the early soaking stage. And then the transferring resistance first decreased, and then increased with the increase of the content of corrosion product. With the increase of soaking time, both electrical double-layer capacitance and filmcapacitance increased.
2008, 24(03): 400-404
doi: 10.3866/PKU.WHXB20080308
Abstract:
Two kinds of equations of the surface tension vs the concentration for ideal binary mixtures of surfactants were acquired with Newton iterative method. The accuracy could be verified by comparison among the values obtained respectively from the iterative, the numerical and observable approaches for surface tension of the ideal binary mixed homology systems C12H25PO(CH3)2/C10H21PO(CH3)2, C12H25 (CH3)3NBr/C16H33 (CH3)3NBr in aqueous solutions (25 ℃), C8F15O2NH4/C9F17O2NH4 in 0.1 mol·L-1 ammonium chloride solution (25 ℃). The results indicated that the astringency velocity of the two kinds of iterative methods was very fast and the relative error of expression was below 1%.
Two kinds of equations of the surface tension vs the concentration for ideal binary mixtures of surfactants were acquired with Newton iterative method. The accuracy could be verified by comparison among the values obtained respectively from the iterative, the numerical and observable approaches for surface tension of the ideal binary mixed homology systems C12H25PO(CH3)2/C10H21PO(CH3)2, C12H25 (CH3)3NBr/C16H33 (CH3)3NBr in aqueous solutions (25 ℃), C8F15O2NH4/C9F17O2NH4 in 0.1 mol·L-1 ammonium chloride solution (25 ℃). The results indicated that the astringency velocity of the two kinds of iterative methods was very fast and the relative error of expression was below 1%.
2008, 24(03): 405-410
doi: 10.3866/PKU.WHXB20080309
Abstract:
Based on our previous researchwork of closo-hedral cluster (HAlNH)12, the geometries, natural bond orbital, vibrational frequency, energetic parameters, magnetic shielding constants, and nucleus independent chemical shifts of stable endohedral X@(HAlNH)12 complexes (X=Be, Mg, Ca, Zn, Al+, Ga+) were studied at the B3LYP/6-31G(d) level of density functional theory. The transition states (TS) of guest X shifting from the cage center toward a face of six-membered ring were investigated by the QST3 method of Gaussian 03 package and demonstrated with intrinsic reaction coordinate (IRC). It was found that the X@(HAlNH)12 complexes (X=Be,Mg, Zn, Al+, Ga+) were kinetically stable structures, and the complex Ga+@(HAlNH)12 was energetically favorable than the other complexes in thermodynamics.
Based on our previous researchwork of closo-hedral cluster (HAlNH)12, the geometries, natural bond orbital, vibrational frequency, energetic parameters, magnetic shielding constants, and nucleus independent chemical shifts of stable endohedral X@(HAlNH)12 complexes (X=Be, Mg, Ca, Zn, Al+, Ga+) were studied at the B3LYP/6-31G(d) level of density functional theory. The transition states (TS) of guest X shifting from the cage center toward a face of six-membered ring were investigated by the QST3 method of Gaussian 03 package and demonstrated with intrinsic reaction coordinate (IRC). It was found that the X@(HAlNH)12 complexes (X=Be,Mg, Zn, Al+, Ga+) were kinetically stable structures, and the complex Ga+@(HAlNH)12 was energetically favorable than the other complexes in thermodynamics.
2008, 24(03): 411-415
doi: 10.1016/S1872-1508(08)60020-0
Abstract:
The effect of electrolytes on the micellar behavior of an amphiphilic drug, chlorpromazine (CPZ) hydrochloride, was studied using cloud point (CP) and dye solubilization techniques. In the presence of KBr, increase in pH led to decrease in the CP of 50 mmol·L-1 drug solution (prepared in 10 mmol·L-1 sodium phosphate (SP) buffer) because of deprotonation of drug molecules at high pH. The visible absorbance increased (due to dye solubilization) with the increase in pHfrom6.5 to 6.9, which indicated micellar growth. At fixed pH(6.7), addition of inorganic salts (KF, KCl, and KBr) to drug solutions (50 mmol·L-1) caused an increase in the CP as well as in the visible absorbance, with effectiveness being in the order: F-Na+>K+, which was explained by considering cognizance of their hydrated radii. Compared with anions, their effect was small. Increase in [CPZ] caused micellar growth and hence the CP as well as the visible absorbance increased. The overall behavior was discussed in terms of electrostatic interactions and micellar growth.
The effect of electrolytes on the micellar behavior of an amphiphilic drug, chlorpromazine (CPZ) hydrochloride, was studied using cloud point (CP) and dye solubilization techniques. In the presence of KBr, increase in pH led to decrease in the CP of 50 mmol·L-1 drug solution (prepared in 10 mmol·L-1 sodium phosphate (SP) buffer) because of deprotonation of drug molecules at high pH. The visible absorbance increased (due to dye solubilization) with the increase in pHfrom6.5 to 6.9, which indicated micellar growth. At fixed pH(6.7), addition of inorganic salts (KF, KCl, and KBr) to drug solutions (50 mmol·L-1) caused an increase in the CP as well as in the visible absorbance, with effectiveness being in the order: F-Na+>K+, which was explained by considering cognizance of their hydrated radii. Compared with anions, their effect was small. Increase in [CPZ] caused micellar growth and hence the CP as well as the visible absorbance increased. The overall behavior was discussed in terms of electrostatic interactions and micellar growth.
2008, 24(03): 416-422
doi: 10.3866/PKU.WHXB20080311
Abstract:
Codeposition and costripping models for bimetal from Ag+, Cu2+, Pb2+, Sn2+, and Cd2+, on boron-doped diammond (BDD) surface were studied with differential pulse anodic stripping voltammetry. The results showed that bimetal codeposition and costripping models on BDD surface were determined by deposition potential of metals, mutual inferences between two kinds of metals, interactions of metal and electrolytic solution and so on. In addition, four types of codeposition and costripping models for bimetal were summarized: (1) metal 1 stripping-metal 2 stripping; (2) metal 1 stripping-hydrogen evolution-metal 2 stripping; (3) metal 1 stripping-alloy striping-metal 2 stripping; (4) metal 1 stripping-hydrogen evolution-complex forming-metal 2 stripping.
Codeposition and costripping models for bimetal from Ag+, Cu2+, Pb2+, Sn2+, and Cd2+, on boron-doped diammond (BDD) surface were studied with differential pulse anodic stripping voltammetry. The results showed that bimetal codeposition and costripping models on BDD surface were determined by deposition potential of metals, mutual inferences between two kinds of metals, interactions of metal and electrolytic solution and so on. In addition, four types of codeposition and costripping models for bimetal were summarized: (1) metal 1 stripping-metal 2 stripping; (2) metal 1 stripping-hydrogen evolution-metal 2 stripping; (3) metal 1 stripping-alloy striping-metal 2 stripping; (4) metal 1 stripping-hydrogen evolution-complex forming-metal 2 stripping.
2008, 24(03): 423-427
doi: 10.3866/PKU.WHXB20080312
Abstract:
The NaAlH4 complex hydride was prepared by hydrogenation of the ball-milled (NaH/Al+Ti) and (NaH/Al+Ti-Zr) composites. The influences of Ti and Ti-Zr catalysts, different hydriding temperatures and pressures on its reversible hydrogen storage behaviors were investigated. It was found that the catalysis of Ti-Zr powders as co-catalysts on the dehydriding/hydriding characteristics of NaH/Al was better than that of Ti alone as catalyst. As the hydriding temperature increased from 85 ℃ to 140 ℃, the hydrogen absorption capacity increased first and then decreased, and reached the highest value at 120 ℃. The composite co-doped with Ti-Zr catalysts had the best reversible hydrogen storage properties, its hydrogen storage capacities were 4.61%(w) at 120 ℃ and 3.52%(w) at 85 ℃, which were 0.40% and 0.70%(w) higher than that doped with Ti alone as catalyst in the same hydriding condition, respectively. The hydrogen storage performance of (NaH/Al+Ti-Zr) composite was enhanced with the increase of hydriding pressure. XRD and DSC analyses showed that the dehydriding process of NaAlH4 system took place in two steps. The composite co-doped with Ti-Zr catalysts could improve the dehydriding/hydriding kinetics of NaAlH4 systemand reduced its dehydriding temperature. That was the main reason of the hydrogen storage characteristic of the composites co-doped with Ti-Zr catalysts better than that doped with Ti catalyst alone.
The NaAlH4 complex hydride was prepared by hydrogenation of the ball-milled (NaH/Al+Ti) and (NaH/Al+Ti-Zr) composites. The influences of Ti and Ti-Zr catalysts, different hydriding temperatures and pressures on its reversible hydrogen storage behaviors were investigated. It was found that the catalysis of Ti-Zr powders as co-catalysts on the dehydriding/hydriding characteristics of NaH/Al was better than that of Ti alone as catalyst. As the hydriding temperature increased from 85 ℃ to 140 ℃, the hydrogen absorption capacity increased first and then decreased, and reached the highest value at 120 ℃. The composite co-doped with Ti-Zr catalysts had the best reversible hydrogen storage properties, its hydrogen storage capacities were 4.61%(w) at 120 ℃ and 3.52%(w) at 85 ℃, which were 0.40% and 0.70%(w) higher than that doped with Ti alone as catalyst in the same hydriding condition, respectively. The hydrogen storage performance of (NaH/Al+Ti-Zr) composite was enhanced with the increase of hydriding pressure. XRD and DSC analyses showed that the dehydriding process of NaAlH4 system took place in two steps. The composite co-doped with Ti-Zr catalysts could improve the dehydriding/hydriding kinetics of NaAlH4 systemand reduced its dehydriding temperature. That was the main reason of the hydrogen storage characteristic of the composites co-doped with Ti-Zr catalysts better than that doped with Ti catalyst alone.
2008, 24(03): 428-432
doi: 10.3866/PKU.WHXB20080313
Abstract:
2,2,2-trifluoroethanol (TFE) aqueous solution is a special associate system. Molecular dynamics (MD) simulations combined with the chemical shifts in NMR were used to investigate the hydrogen-bond network in TFE-water system. The strong hydrogen bonds and weak C—H…O contacts were found existing in the TFE-water mixtures from the information of radial distribution function (RDF). And the TFE-water mixtures could be divided into three different regions from the analysis of the hydrogen-bonding network. In the water rich region, water molecules prefer to form the hydrogen bonds with themselves and establish the stable clusters. With the concentration of TFE increasing, the stable structure of water molecules was broken down. In the TFE rich region, the self-associated clusters of TFE were dominant. In addition, the chemical shifts were adopted to study the interactions in the mixtures. The varieties of the average hydrogen bond numbers fromMD simulations and the chemical shifts in NMR showed od agreement.
2,2,2-trifluoroethanol (TFE) aqueous solution is a special associate system. Molecular dynamics (MD) simulations combined with the chemical shifts in NMR were used to investigate the hydrogen-bond network in TFE-water system. The strong hydrogen bonds and weak C—H…O contacts were found existing in the TFE-water mixtures from the information of radial distribution function (RDF). And the TFE-water mixtures could be divided into three different regions from the analysis of the hydrogen-bonding network. In the water rich region, water molecules prefer to form the hydrogen bonds with themselves and establish the stable clusters. With the concentration of TFE increasing, the stable structure of water molecules was broken down. In the TFE rich region, the self-associated clusters of TFE were dominant. In addition, the chemical shifts were adopted to study the interactions in the mixtures. The varieties of the average hydrogen bond numbers fromMD simulations and the chemical shifts in NMR showed od agreement.
2008, 24(03): 433-436
doi: 10.3866/PKU.WHXB20080314
Abstract:
Fumed silica suspensions in polyethylene glycol (PEG200) exhibited shear-thickening behavior under dynamic oscillatory strain amplitude. Two regimes of shear-thickening behavior were obtained: the first occured at critical strain amplitude γc and different constant frequencies, and the second occured at critical frequency and constant strain amplitude γ0=500%. For the first, the relationships of both of the moduli (G’ and G’’) versus strain amplitude were investigated. The strain amplitude as a function of different constant frequencies was observed. In the linear viscoelastic region, the storage (G’) and the loss (G’’)moduli depended stronglyon frequencywith the power-law: G’∝ω0.57, G’’∝ω0.7. In the second regime, the moduli (G’ and G’’) and complex viscosity η* showed strong dependence on frequency. The behaviors could be qualitatively explained using the cluster theory, which attributed the phenomena to the formation of metastable, flow induced clusters.
Fumed silica suspensions in polyethylene glycol (PEG200) exhibited shear-thickening behavior under dynamic oscillatory strain amplitude. Two regimes of shear-thickening behavior were obtained: the first occured at critical strain amplitude γc and different constant frequencies, and the second occured at critical frequency and constant strain amplitude γ0=500%. For the first, the relationships of both of the moduli (G’ and G’’) versus strain amplitude were investigated. The strain amplitude as a function of different constant frequencies was observed. In the linear viscoelastic region, the storage (G’) and the loss (G’’)moduli depended stronglyon frequencywith the power-law: G’∝ω0.57, G’’∝ω0.7. In the second regime, the moduli (G’ and G’’) and complex viscosity η* showed strong dependence on frequency. The behaviors could be qualitatively explained using the cluster theory, which attributed the phenomena to the formation of metastable, flow induced clusters.
2008, 24(03): 437-442
doi: 10.3866/PKU.WHXB20080315
Abstract:
Adsorption of O atom on Al low index surfaces was inverstigated with the 5-parameter Morse potential (5-MP). All critical characteristics of this system, such as adsorption site, adsorption geometry, binding energy, and eigenvalue for vibration, were obtained. All critical characteristics were regarded as probe to analysis the adsorption system systematically, the comprehensive adsorption characters were found out. The calculated results showed that O atoms were located at the three-fold hollowsite and the octahedral site of the Al(111) with the perpendicular vibrational mode 621(619) cm-1 and 464 cm-1, the parallel vibrational mode 880 (887) cm-1 and 437 cm-1. For Al(100) system, O atoms were located at the four-fold hollow site and the tetrahedral site. With respect to Al(110) system, the preferential adsorption states were the quasi-3-fold site and the octahedral site rather than the long bridge site.
Adsorption of O atom on Al low index surfaces was inverstigated with the 5-parameter Morse potential (5-MP). All critical characteristics of this system, such as adsorption site, adsorption geometry, binding energy, and eigenvalue for vibration, were obtained. All critical characteristics were regarded as probe to analysis the adsorption system systematically, the comprehensive adsorption characters were found out. The calculated results showed that O atoms were located at the three-fold hollowsite and the octahedral site of the Al(111) with the perpendicular vibrational mode 621(619) cm-1 and 464 cm-1, the parallel vibrational mode 880 (887) cm-1 and 437 cm-1. For Al(100) system, O atoms were located at the four-fold hollow site and the tetrahedral site. With respect to Al(110) system, the preferential adsorption states were the quasi-3-fold site and the octahedral site rather than the long bridge site.
2008, 24(03): 443-447
doi: 10.3866/PKU.WHXB20080316
Abstract:
Long-chain alkanol, 1-C18H37OH, adsorbed from solution onto highly oriented pyrolytic graphite (HOPG) and formed ordered, oriented monolayer films at room temperature in air. The formation and structure of 1-octadecanol self-assembledmonolayers (SAMs) on HOPGwere examined using scanning tunneling microscopy (STM), contact angle measurement, and X-ray photoelectron spectroscopy (XPS). Our experimental results indicated that 1-octadecanol SAMs grew in domains, with molecules arranged either horizontally or vertically on the substrate. Moreover, the permutation means of the molecule showed relevance to the surface coverage of 1-octadecanol SAMs on the HOPG.
Long-chain alkanol, 1-C18H37OH, adsorbed from solution onto highly oriented pyrolytic graphite (HOPG) and formed ordered, oriented monolayer films at room temperature in air. The formation and structure of 1-octadecanol self-assembledmonolayers (SAMs) on HOPGwere examined using scanning tunneling microscopy (STM), contact angle measurement, and X-ray photoelectron spectroscopy (XPS). Our experimental results indicated that 1-octadecanol SAMs grew in domains, with molecules arranged either horizontally or vertically on the substrate. Moreover, the permutation means of the molecule showed relevance to the surface coverage of 1-octadecanol SAMs on the HOPG.
2008, 24(03): 448-452
doi: 10.3866/PKU.WHXB20080317
Abstract:
The ultrasoft pseudopotential wave method with the generalized gradient approximation to the density functional theory was adopted to study the electronic structures and magnetism of Sr2-xLaxCrReO6 (x=0, 0.25, 0.5, 1). Through the geometry optimization of the Sr2-xLaxCrReO6 system, lattice parameters, electron-and spin-distributions, and magnetic moments were obtained. It was found that for low doping level (x<1), the spin-up electronic density just below the Fermi energy increases, the band gap between the valence and conductive bands in the down-spin channel was enlarged, and the magnetic moment decreased with the increasing of La-doped level; at a certain concentration of La atoms (x=1) the Sr2-xLaxCrReO6 changed fromhalf-metallic to metallic and fromferrimagnetic to ferromagnetic.
The ultrasoft pseudopotential wave method with the generalized gradient approximation to the density functional theory was adopted to study the electronic structures and magnetism of Sr2-xLaxCrReO6 (x=0, 0.25, 0.5, 1). Through the geometry optimization of the Sr2-xLaxCrReO6 system, lattice parameters, electron-and spin-distributions, and magnetic moments were obtained. It was found that for low doping level (x<1), the spin-up electronic density just below the Fermi energy increases, the band gap between the valence and conductive bands in the down-spin channel was enlarged, and the magnetic moment decreased with the increasing of La-doped level; at a certain concentration of La atoms (x=1) the Sr2-xLaxCrReO6 changed fromhalf-metallic to metallic and fromferrimagnetic to ferromagnetic.
2008, 24(03): 453-458
doi: 10.3866/PKU.WHXB20080318
Abstract:
The kinetic behaviour of the exothermic decomposition reaction and the specific heat capacity of N-guanylurea dinitramide (GUDN) were determined by DSC and mircocalorimeter. Its kinetic parameters of the major exothermic decomposition reaction in a temperature-programmed mode [the apparent activation energy (Ea) and pre-exponential factor (A)], self-accelerating decomposition temperature (TSADT), time to maximum rate (tTMrad), and time-to-ignition (tTIad) under adiabatic conditions were calculated. The results showed that under non-isothermal DSCconditions, the thermal decomposition of GUDN could be described by the empiric-order autocatalytic equation: dα/dt=1018.49exp(-195500/RT)(1-α)0.81+1018.00exp (-177000/RT)α1.29 (1-α)0.71, and the value of the critical rate of temperature rise in GUDN was 0.1236 K·h-1 when the decomposition reaction converted into thermal explosion. The values of TSADT, tTMRad, and tTIad were 473.95 K, 2.24 s, and 3.51 s, respectively.
The kinetic behaviour of the exothermic decomposition reaction and the specific heat capacity of N-guanylurea dinitramide (GUDN) were determined by DSC and mircocalorimeter. Its kinetic parameters of the major exothermic decomposition reaction in a temperature-programmed mode [the apparent activation energy (Ea) and pre-exponential factor (A)], self-accelerating decomposition temperature (TSADT), time to maximum rate (tTMrad), and time-to-ignition (tTIad) under adiabatic conditions were calculated. The results showed that under non-isothermal DSCconditions, the thermal decomposition of GUDN could be described by the empiric-order autocatalytic equation: dα/dt=1018.49exp(-195500/RT)(1-α)0.81+1018.00exp (-177000/RT)α1.29 (1-α)0.71, and the value of the critical rate of temperature rise in GUDN was 0.1236 K·h-1 when the decomposition reaction converted into thermal explosion. The values of TSADT, tTMRad, and tTIad were 473.95 K, 2.24 s, and 3.51 s, respectively.
2008, 24(03): 459-464
doi: 10.3866/PKU.WHXB20080319
Abstract:
Combined with supercritical ethanol drying, anatase Au/TiO2 and Au-TiO2 with 0.2%(atom fraction) Au content were synthesized by the deposition-precipitation (DP) and the coprecipitation (CP) respectively, and characterized with XRD, BET, Raman, XPS, and TEM. The activity was investigated using the photocatalytical degradation of methyl orange as probe. The results showed that the Au/TiO2 dried at 110 ℃ had a very high photocatalytic activity, the first-order reaction rate constans were 3.2 and 4.1 times higher than those of pure TiO2 and commercial Degussa-P25 photocatalyst respectively. The activity of Au/TiO2 decreased after thermal treatment or reduction in hydrogen due to the reduction of Au3+. A suitable amount of Au3+ on the surface of TiO2 as a trap for photogenerated electron can be beneficial to improving the efficiency of the photocatalytic oxidation process. The Au-TiO2 did not improve the photocatalytic activity of TiO2. The sample with higher crystallization degree after thermal treatment had the higher activity. But when the sample was treated in 800 ℃, the Au would be reduced and moved from the bulk to the surface of TiO2, which resulted in the increase of lattice oxygen vacancy and the decrease of activity.
Combined with supercritical ethanol drying, anatase Au/TiO2 and Au-TiO2 with 0.2%(atom fraction) Au content were synthesized by the deposition-precipitation (DP) and the coprecipitation (CP) respectively, and characterized with XRD, BET, Raman, XPS, and TEM. The activity was investigated using the photocatalytical degradation of methyl orange as probe. The results showed that the Au/TiO2 dried at 110 ℃ had a very high photocatalytic activity, the first-order reaction rate constans were 3.2 and 4.1 times higher than those of pure TiO2 and commercial Degussa-P25 photocatalyst respectively. The activity of Au/TiO2 decreased after thermal treatment or reduction in hydrogen due to the reduction of Au3+. A suitable amount of Au3+ on the surface of TiO2 as a trap for photogenerated electron can be beneficial to improving the efficiency of the photocatalytic oxidation process. The Au-TiO2 did not improve the photocatalytic activity of TiO2. The sample with higher crystallization degree after thermal treatment had the higher activity. But when the sample was treated in 800 ℃, the Au would be reduced and moved from the bulk to the surface of TiO2, which resulted in the increase of lattice oxygen vacancy and the decrease of activity.
2008, 24(03): 465-470
doi: 10.3866/PKU.WHXB20080320
Abstract:
CuO nanoparticles were synthesized in a nanoreactor formed by adsorption layer on silica surface. Adsorption capacity measuration experiment with different water concentrations, solvent substitution experiment and reaction-before-adsorption experiment showed that the water adsorption layer existed on the SiO2 surface and served as a place reaction mainly occurring. The three-region distribution model of Cu2+ in this system was proposed according to the adsorption data. The increase of water concentration and NaOH concentration in system will both made more Cu2+ migrate to the adsorption layer region. XRD analysis indicated that the rise of temperature and the increase of NaOH concentration were both in favor of the smaller CuO grain formation. The growth of CuO grain was restricted by the adsorption layer, which became thinner with temperature rising. And the nucleation rate accelerated as the supersaturation degree in adsorption layer increased with the NaOH concentration rising.
CuO nanoparticles were synthesized in a nanoreactor formed by adsorption layer on silica surface. Adsorption capacity measuration experiment with different water concentrations, solvent substitution experiment and reaction-before-adsorption experiment showed that the water adsorption layer existed on the SiO2 surface and served as a place reaction mainly occurring. The three-region distribution model of Cu2+ in this system was proposed according to the adsorption data. The increase of water concentration and NaOH concentration in system will both made more Cu2+ migrate to the adsorption layer region. XRD analysis indicated that the rise of temperature and the increase of NaOH concentration were both in favor of the smaller CuO grain formation. The growth of CuO grain was restricted by the adsorption layer, which became thinner with temperature rising. And the nucleation rate accelerated as the supersaturation degree in adsorption layer increased with the NaOH concentration rising.
2008, 24(03): 471-474
doi: 10.3866/PKU.WHXB20080321
Abstract:
The metastable phase equilibria of the quaternary system Na+, K+//Cl-, B4O2-
7-H2O were studied at 273 K by isothermal evaporation method. Solubilities and densities of the equilibrium solution of this system were determined. According to the experimental data, the metastable equilibrium phase diagram was plotted. The phase diagram of the system consists of five univariant curves, four crystallization fields and two invariant points. No double salt or solid solution was formed. The four crystallization fields were corresponding to single salt NaCl, KCl, K2B4O7·4H2O and Na2B4O7·10H2O, respectively. Invariant point E1 was saturated with salt KCl, NaCl and Na2B4O7·10H2O, the mass fraction composition of the equilibrium solution corresponding to E1 is w(Cl-)=29.15%, w(B4O2-7)=0.64%, w(K+)=5.97%, w(Na+)=15.55%, while that of point E2 was w(Cl-)=22.84%, w(B4O2-7)=10.98%, w(K+)=28.01%, w(Na+)=1.53%. Point E2 is saturated with salt KCl, Na2B4O7·10H2O and K2B4O7·4H2O. Compared with the stable phase diagram at 298 K, the crystallization field of Na2B4O7·10H2O became large at 273 K in this system, whereas the crystallization fields of K2B4O7·4H2O and NaCl became small.
The metastable phase equilibria of the quaternary system Na+, K+//Cl-, B4O2-
7-H2O were studied at 273 K by isothermal evaporation method. Solubilities and densities of the equilibrium solution of this system were determined. According to the experimental data, the metastable equilibrium phase diagram was plotted. The phase diagram of the system consists of five univariant curves, four crystallization fields and two invariant points. No double salt or solid solution was formed. The four crystallization fields were corresponding to single salt NaCl, KCl, K2B4O7·4H2O and Na2B4O7·10H2O, respectively. Invariant point E1 was saturated with salt KCl, NaCl and Na2B4O7·10H2O, the mass fraction composition of the equilibrium solution corresponding to E1 is w(Cl-)=29.15%, w(B4O2-7)=0.64%, w(K+)=5.97%, w(Na+)=15.55%, while that of point E2 was w(Cl-)=22.84%, w(B4O2-7)=10.98%, w(K+)=28.01%, w(Na+)=1.53%. Point E2 is saturated with salt KCl, Na2B4O7·10H2O and K2B4O7·4H2O. Compared with the stable phase diagram at 298 K, the crystallization field of Na2B4O7·10H2O became large at 273 K in this system, whereas the crystallization fields of K2B4O7·4H2O and NaCl became small.
2008, 24(03): 475-480
doi: 10.3866/PKU.WHXB20080322
Abstract:
Adouble-template (DT)method using hexadecyl trimethyl ammoniumbromide (CTAB) and dodecylamine (ODA) as templates and a homogeneous precipitation (HP) method were used to prepare mesoporous-SnO2. The BET characterization showed that the average diameter, total pore volume, and surface area of the DT-processed sample were 4.9 nm, 0.213 m3·g-1, and 172.9 m2·g-1, respectively. The sample prepared by the HP method had a considerably non-uniform distribution of pore size, while the total pore volume and surface area decreased to 66.0% and 21.8% of the corresponding value of the DT-processed material. Electrochemical impedance spectroscopy (EIS) was introduced to test the humidity sensing of the sensor made by the mesoporous-SnO2, using interdigitated electrodes as a working electrode. It was found that the charge transferring resistance, the electric double layer capacity, and the Warburg diffusive coefficient of the DT-processed sample generally exhibited a more significant change than that of the HP-processed sample, indicating that the DT-processed sample possessed a higher sensitivity to humidity. A closer look at the correlation between structural features and humidity sensing revealed that the humidity sensing of the sensor could be improved by obtaining the mesoporous SnO2 with higher pore volume and surface area.
Adouble-template (DT)method using hexadecyl trimethyl ammoniumbromide (CTAB) and dodecylamine (ODA) as templates and a homogeneous precipitation (HP) method were used to prepare mesoporous-SnO2. The BET characterization showed that the average diameter, total pore volume, and surface area of the DT-processed sample were 4.9 nm, 0.213 m3·g-1, and 172.9 m2·g-1, respectively. The sample prepared by the HP method had a considerably non-uniform distribution of pore size, while the total pore volume and surface area decreased to 66.0% and 21.8% of the corresponding value of the DT-processed material. Electrochemical impedance spectroscopy (EIS) was introduced to test the humidity sensing of the sensor made by the mesoporous-SnO2, using interdigitated electrodes as a working electrode. It was found that the charge transferring resistance, the electric double layer capacity, and the Warburg diffusive coefficient of the DT-processed sample generally exhibited a more significant change than that of the HP-processed sample, indicating that the DT-processed sample possessed a higher sensitivity to humidity. A closer look at the correlation between structural features and humidity sensing revealed that the humidity sensing of the sensor could be improved by obtaining the mesoporous SnO2 with higher pore volume and surface area.
2008, 24(03): 481-486
doi: 10.3866/PKU.WHXB20080323
Abstract:
(NaPO3)6 was added to Na2SiO3-KOH electrolyte system, and in-situ ceramic coatings were prepared on AZ91D magnesium alloy by micro-arc oxidation technique. Room temperature electrochemical behavior of the ceramic coatings, formed in electrolyte with and without (NaPO3)6, in NaCl (w=3.5%) solution was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the ceramic coating formed in electrolyte containing (NaPO3)6 indicated a considerable increase in corrosion potential and a remarkable decrease in corrosion current density compared to the bare AZ91D magnesium alloy. The main cause was that the addition of (NaPO3)6 increased oxygen vacancies on the Mg substrate surface and the content of PO3-4 in the electrolyte. As a result, the (NaPO3)6-addition speeded up the formation of Mg oxide at the interface between metal and ceramic film(coating) (M/F), and increased the thickness and compactness of the ceramic coating. Based on the studied electrochemical reaction system and the special structure of the ceramic coating, a reasonable equivalent circuit was established. Combining with the EIS data, the effect mechanismof (NaPO3)6-addition on improving the electrochemical corrosion resistance of the ceramic coatings was investigated.
(NaPO3)6 was added to Na2SiO3-KOH electrolyte system, and in-situ ceramic coatings were prepared on AZ91D magnesium alloy by micro-arc oxidation technique. Room temperature electrochemical behavior of the ceramic coatings, formed in electrolyte with and without (NaPO3)6, in NaCl (w=3.5%) solution was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the ceramic coating formed in electrolyte containing (NaPO3)6 indicated a considerable increase in corrosion potential and a remarkable decrease in corrosion current density compared to the bare AZ91D magnesium alloy. The main cause was that the addition of (NaPO3)6 increased oxygen vacancies on the Mg substrate surface and the content of PO3-4 in the electrolyte. As a result, the (NaPO3)6-addition speeded up the formation of Mg oxide at the interface between metal and ceramic film(coating) (M/F), and increased the thickness and compactness of the ceramic coating. Based on the studied electrochemical reaction system and the special structure of the ceramic coating, a reasonable equivalent circuit was established. Combining with the EIS data, the effect mechanismof (NaPO3)6-addition on improving the electrochemical corrosion resistance of the ceramic coatings was investigated.
2008, 24(03): 487-491
doi: 10.3866/PKU.WHXB20080324
Abstract:
Palladium nano-particles were synthesized by W/O microemulsion composed of nonionic surfactant (alkylpolyglycol ethers) named Marlipal O13/50, water and cyclohexane. The deposition of palladium nano-particles by chemicals demulsifying was investigated. The results showed that the sequence of deposition rate of palladium nano-particles from microemulsion under the action of different chemical demulsifier is 1,4-dioxane>THF>methanol>ethanol >n-butanol. The effects on interfacial tension and amphiphilicity of chemical demulsifier were studied. The results showed that the demulsifying process of microemulsion is also a process of interfacial tension increasing and a process gradually near to Lifschitz line.
Palladium nano-particles were synthesized by W/O microemulsion composed of nonionic surfactant (alkylpolyglycol ethers) named Marlipal O13/50, water and cyclohexane. The deposition of palladium nano-particles by chemicals demulsifying was investigated. The results showed that the sequence of deposition rate of palladium nano-particles from microemulsion under the action of different chemical demulsifier is 1,4-dioxane>THF>methanol>ethanol >n-butanol. The effects on interfacial tension and amphiphilicity of chemical demulsifier were studied. The results showed that the demulsifying process of microemulsion is also a process of interfacial tension increasing and a process gradually near to Lifschitz line.
2008, 24(03): 492-496
doi: 10.3866/PKU.WHXB20080325
Abstract:
Thiol-functionalized nanosized mesoporous silica particles with a diameter of 50-200 nm were prepared and characterized by TEM, TG, and DTA. (3-mercaptopropyl) trimethoxy silane (MPTMS) was introduced into the silica networks through three synthesis routes. The mercapto group induces significant changes in the particle morphology, transforming highly ordered hexa nal particles into nanoscale bars. The size of mesoporous silica can be adjusted by controlling reacting time. The addition of triethanolamine instead of NaOH leads to the formation of functionalized spherical particles having a diameter of ca 100 nm. The template can be extracted by HCl-ethanol solution for protecting thiol functional group. In addition, the formation mechanism of the mesoporous silica particles was also discussed.
Thiol-functionalized nanosized mesoporous silica particles with a diameter of 50-200 nm were prepared and characterized by TEM, TG, and DTA. (3-mercaptopropyl) trimethoxy silane (MPTMS) was introduced into the silica networks through three synthesis routes. The mercapto group induces significant changes in the particle morphology, transforming highly ordered hexa nal particles into nanoscale bars. The size of mesoporous silica can be adjusted by controlling reacting time. The addition of triethanolamine instead of NaOH leads to the formation of functionalized spherical particles having a diameter of ca 100 nm. The template can be extracted by HCl-ethanol solution for protecting thiol functional group. In addition, the formation mechanism of the mesoporous silica particles was also discussed.
2008, 24(03): 497-501
doi: 10.3866/PKU.WHXB20080326
Abstract:
Aqueous structures with salt to water molar ratios of 1:30 (Rb2SO4) and 1:14 (Cs2SO4) were measured by X-ray scattering of synchrotron radiation. The radial distribution functions (RDF) of the two example solutions were obtained by analyzing the scattering data. RDF overlapped peaks near the first hydration shell were dealt with Gaussian multi-peak fitting. The fitting data were agreed well with the experimental data. The adscription of every fitting peak was determined by comparing the fitting data with hydrated ion and crystal structure data reported in literatures. The analysis of fitting result indicates that the coordination number of Rb+ and Cs+ is six in the first hydration shell, and the spatial structures are both distorted octahedrons. The contact ion pairs of metal ions with sulphate ion exist in two solutions where the characteristic distances of Rb—S and Cs—S were determined to be 0.407 and 0.427 nm, respectively. The study demonstrated that multi-peak fitting was useful for interpreting the hydrated structure of ions.
Aqueous structures with salt to water molar ratios of 1:30 (Rb2SO4) and 1:14 (Cs2SO4) were measured by X-ray scattering of synchrotron radiation. The radial distribution functions (RDF) of the two example solutions were obtained by analyzing the scattering data. RDF overlapped peaks near the first hydration shell were dealt with Gaussian multi-peak fitting. The fitting data were agreed well with the experimental data. The adscription of every fitting peak was determined by comparing the fitting data with hydrated ion and crystal structure data reported in literatures. The analysis of fitting result indicates that the coordination number of Rb+ and Cs+ is six in the first hydration shell, and the spatial structures are both distorted octahedrons. The contact ion pairs of metal ions with sulphate ion exist in two solutions where the characteristic distances of Rb—S and Cs—S were determined to be 0.407 and 0.427 nm, respectively. The study demonstrated that multi-peak fitting was useful for interpreting the hydrated structure of ions.
2008, 24(03): 502-506
doi: 10.3866/PKU.WHXB20080327
Abstract:
Theoretical studies on the halogen-bond in complexes of H2CO and dihalogen molecules (F2, Cl2, Br2, ClF, BrF, BrCl) were carried out at the levels of B3LYP/6-311++G(d,p) and MP2/6-311++G(d,p). O…X—Y type halogen-bonded complexes were obtained. The calculated results indicated that MP2/6-311++G(d,p) was the better method for the titled systems. After the corrections of ZPE and BSSE (basis set superposition error) by the counterpoise method, the interaction energies of the halogen-bonded complexes were calculated using the MP2 method. The topological properties of the bonds were investigated by the topological analysis of electronic density.
Theoretical studies on the halogen-bond in complexes of H2CO and dihalogen molecules (F2, Cl2, Br2, ClF, BrF, BrCl) were carried out at the levels of B3LYP/6-311++G(d,p) and MP2/6-311++G(d,p). O…X—Y type halogen-bonded complexes were obtained. The calculated results indicated that MP2/6-311++G(d,p) was the better method for the titled systems. After the corrections of ZPE and BSSE (basis set superposition error) by the counterpoise method, the interaction energies of the halogen-bonded complexes were calculated using the MP2 method. The topological properties of the bonds were investigated by the topological analysis of electronic density.
2008, 24(03): 507-512
doi: 10.3866/PKU.WHXB20080328
Abstract:
Molecular recognition of chiral zinc porphyrin [p-(L-Leu)C2O-TPPZn] with amino acid ester derivatives was investigated by UV-Vis spectrophotometric titration and CD spectroscopy. The experimental results suggested that the association constant was KD>KL for amino acid ester derivatives, and then increased following the order of K(AlaOCH3)<K(ValOCH3)<K(LeuOCH3)<K(PheOCH3). CD spectroscopy had also been used in order to elucidate the conformation of the host-guest complex, different chiral environments could come into being from CD spectroscopy when different guests coordinated to host. Moreover, the minimum energy conformations of the host-guest system were obtained by simulated annealing, and it was found that there was π-π* interaction between host and D,L-PheOCH3.
Molecular recognition of chiral zinc porphyrin [p-(L-Leu)C2O-TPPZn] with amino acid ester derivatives was investigated by UV-Vis spectrophotometric titration and CD spectroscopy. The experimental results suggested that the association constant was KD>KL for amino acid ester derivatives, and then increased following the order of K(AlaOCH3)<K(ValOCH3)<K(LeuOCH3)<K(PheOCH3). CD spectroscopy had also been used in order to elucidate the conformation of the host-guest complex, different chiral environments could come into being from CD spectroscopy when different guests coordinated to host. Moreover, the minimum energy conformations of the host-guest system were obtained by simulated annealing, and it was found that there was π-π* interaction between host and D,L-PheOCH3.
2008, 24(03): 513-519
doi: 10.3866/PKU.WHXB20080329
Abstract:
The powder of LiNi1/3Co1/3Mn1/3O2 were prepared directly without artificial grinding and washing by a eutectic molten-salt mixture (0.38LiOH·H2O-0.62LiNO3) method. According to this method, the eutectic molten-salt mixture was self-mixed with precursor thoroughly at low temperature, and then sintered at a certain temperature. The tap-density of the powder obtained was 2.87 g·cm-3. The well-layered 琢-NaFeO2 structure and regular morphology were confirmed by X-ray diffraction (XRD) and scanning electronmicroscopy (SEM).XPSstudies showed that the predominant oxidation states of Ni, Co, andMn in the compound were 2+, 3+, and 4+, respectively. Cathodic behaviour was examined by charge-discharge cycling. The synthesized powder showed a reversible capacity of 160 mAh·g -1 at a specific current of 0.2C in the rang 3.0-4.3 V up to 50 cycles without noticeable capacity-fading.
The powder of LiNi1/3Co1/3Mn1/3O2 were prepared directly without artificial grinding and washing by a eutectic molten-salt mixture (0.38LiOH·H2O-0.62LiNO3) method. According to this method, the eutectic molten-salt mixture was self-mixed with precursor thoroughly at low temperature, and then sintered at a certain temperature. The tap-density of the powder obtained was 2.87 g·cm-3. The well-layered 琢-NaFeO2 structure and regular morphology were confirmed by X-ray diffraction (XRD) and scanning electronmicroscopy (SEM).XPSstudies showed that the predominant oxidation states of Ni, Co, andMn in the compound were 2+, 3+, and 4+, respectively. Cathodic behaviour was examined by charge-discharge cycling. The synthesized powder showed a reversible capacity of 160 mAh·g -1 at a specific current of 0.2C in the rang 3.0-4.3 V up to 50 cycles without noticeable capacity-fading.
2008, 24(03): 520-526
doi: 10.3866/PKU.WHXB20080330
Abstract:
The super gravity field was applied to chlor-alkali electrolysis. The effects of super gravity on hydrogen evolution reaction (HER) and chlorine evolution reaction (CER) were investigated by linear sweep voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS). The relationship between the cell voltages and gravity coefficient was studied. The results indicated that, the gas evolution reactions were intensified by super gravity and gas product was easier to spillover fromsolution. The solution resistance would reduce with the increase of gravity coefficient. The cell voltages also decreased with the increase of gravity coefficient, and the higher the current density, the larger the degree of cell voltage reduction.
The super gravity field was applied to chlor-alkali electrolysis. The effects of super gravity on hydrogen evolution reaction (HER) and chlorine evolution reaction (CER) were investigated by linear sweep voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS). The relationship between the cell voltages and gravity coefficient was studied. The results indicated that, the gas evolution reactions were intensified by super gravity and gas product was easier to spillover fromsolution. The solution resistance would reduce with the increase of gravity coefficient. The cell voltages also decreased with the increase of gravity coefficient, and the higher the current density, the larger the degree of cell voltage reduction.
2008, 24(03): 527-532
doi: 10.3866/PKU.WHXB20080331
Abstract:
The carbon nanotubes were added to the cathode to prepare SC high-power Ni/MH batteries. The capacity, large-current discharging performance and cycle life were investigated. It was found that adding carbon nanotubes was greatly advantageous to enhance the batteries’ overall performance, especially the large-rate discharge performance and cycle life. When the weight ratio of the MWNTs in the compound electrode was 0.8%(w), the overall performance of the battery was the best, which showed a highest capacity of 3369 mAh in the condition of 3000 mA charge current and 6000 mA discharge current (2C-rate discharge), and the cycle life surpassed 600 times, the capacities passed 3280 mAh (97% DOD (depth of discharge)). Especially in the condition of 5C-rate large-current discharge (3000 mAh charge current and 15000 mA discharge current), its cycle life surpassed 180 times (89.1% DOD).
The carbon nanotubes were added to the cathode to prepare SC high-power Ni/MH batteries. The capacity, large-current discharging performance and cycle life were investigated. It was found that adding carbon nanotubes was greatly advantageous to enhance the batteries’ overall performance, especially the large-rate discharge performance and cycle life. When the weight ratio of the MWNTs in the compound electrode was 0.8%(w), the overall performance of the battery was the best, which showed a highest capacity of 3369 mAh in the condition of 3000 mA charge current and 6000 mA discharge current (2C-rate discharge), and the cycle life surpassed 600 times, the capacities passed 3280 mAh (97% DOD (depth of discharge)). Especially in the condition of 5C-rate large-current discharge (3000 mAh charge current and 15000 mA discharge current), its cycle life surpassed 180 times (89.1% DOD).
2008, 24(03): 533-538
doi: 10.3866/PKU.WHXB20080332
Abstract:
With the aim of investigating the effect of pore structure of activated carbon (AC) on the photocatalytic activity of TiO2/AC composite photocatalyst, 4 kinds of AC with similar surface chemical characteristics and different pore structures were used and compared. Phenol degradation was used for photocatalytic activity test. N2 adsorption isotherm (77 K) was used for BET surface area (SBET), pore volume, and pore size distribution measurement. Boehm titration and elemental analysis were used for surface chemical characteristics determination. XRD, DRS, and SEM were used to characterize the crystal structure, spectra characteristics, and surface properties. The results showed that the pore structure of AC had significant effect on the photocatalytic activity of TiO2/AC. The synergistic coefficients for the activity enhancement of AC1, AC2, AC3, and AC4 were 1.55, 2.03, 1.28, and 1.43, respectively, which exhibited the similar tendency with the contact interface (⊿S). AC with both developed micropore and mesopore structures exhibited the highest activity when composited with TiO2. The developed micropore structure can provide more adsorption sites for pollutant molecules. More mesopore can be beneficial to the transfer of adsorbed phenol from adsorption sites to active TiO2. Also, the mesopore can inhibit the aggregation of nano-size TiO2, improve its dispersion and increase the contact interface between AC and TiO2.
With the aim of investigating the effect of pore structure of activated carbon (AC) on the photocatalytic activity of TiO2/AC composite photocatalyst, 4 kinds of AC with similar surface chemical characteristics and different pore structures were used and compared. Phenol degradation was used for photocatalytic activity test. N2 adsorption isotherm (77 K) was used for BET surface area (SBET), pore volume, and pore size distribution measurement. Boehm titration and elemental analysis were used for surface chemical characteristics determination. XRD, DRS, and SEM were used to characterize the crystal structure, spectra characteristics, and surface properties. The results showed that the pore structure of AC had significant effect on the photocatalytic activity of TiO2/AC. The synergistic coefficients for the activity enhancement of AC1, AC2, AC3, and AC4 were 1.55, 2.03, 1.28, and 1.43, respectively, which exhibited the similar tendency with the contact interface (⊿S). AC with both developed micropore and mesopore structures exhibited the highest activity when composited with TiO2. The developed micropore structure can provide more adsorption sites for pollutant molecules. More mesopore can be beneficial to the transfer of adsorbed phenol from adsorption sites to active TiO2. Also, the mesopore can inhibit the aggregation of nano-size TiO2, improve its dispersion and increase the contact interface between AC and TiO2.
2008, 24(03): 539-542
doi: 10.3866/PKU.WHXB20080333
Abstract:
Hexa nal cone-shaped ZnO nanoparticles were synthesized by the esterification between zinc acetate and alcohol with non-basic solution route. For the formation process of ZnO nanoparticles, no bases, surfactants, or catalysts were used. Transmission electron microscopy (TEM), selected area electron diffraction (SAED), and scanning electron microscopy (SEM) measurements were used to investigate the morphology and structure. The synthesized ZnO nanoparticles were singlecrystal with hexa nal phase. Furthermore, the as-prepared ZnO particles showed a strong UV emission at 378 nm due to the annihilation of excitons, indicating that the ZnO nanostructure was promising as a high-performance optical material.
Hexa nal cone-shaped ZnO nanoparticles were synthesized by the esterification between zinc acetate and alcohol with non-basic solution route. For the formation process of ZnO nanoparticles, no bases, surfactants, or catalysts were used. Transmission electron microscopy (TEM), selected area electron diffraction (SAED), and scanning electron microscopy (SEM) measurements were used to investigate the morphology and structure. The synthesized ZnO nanoparticles were singlecrystal with hexa nal phase. Furthermore, the as-prepared ZnO particles showed a strong UV emission at 378 nm due to the annihilation of excitons, indicating that the ZnO nanostructure was promising as a high-performance optical material.
2008, 24(03): 543-546
doi: 10.3866/PKU.WHXB20080334
Abstract:
The interaction between cinnamic acid and bovine serumalbumin (BSA) has been studied with fluorimeter under physiological conditions. The experimental results demonstrated that the combination reaction of cinnamic acid and BSA was a static quenching process because of forming 1:1 complex, and the dominant binding force was hydrophobic interaction. At 310 K, the binding constant and the number of binding sites were 3.07×104 L·mol-1 and 1.10, respectively. And the conformation of BSA was changed due to the presence of cinnamic acid. Furthermore, the binding constant and the number of binding sites would decrease due to adding alcohol.
The interaction between cinnamic acid and bovine serumalbumin (BSA) has been studied with fluorimeter under physiological conditions. The experimental results demonstrated that the combination reaction of cinnamic acid and BSA was a static quenching process because of forming 1:1 complex, and the dominant binding force was hydrophobic interaction. At 310 K, the binding constant and the number of binding sites were 3.07×104 L·mol-1 and 1.10, respectively. And the conformation of BSA was changed due to the presence of cinnamic acid. Furthermore, the binding constant and the number of binding sites would decrease due to adding alcohol.
