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2016 Volume 32 Issue 11
2016, 32(11):
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2016, 32(11): 2645-2646
doi: 10.3866/PKU.WHXB201610271
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2016, 32(11): 2647-2648
doi: 10.3866/PKU.WHXB201610141
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2016, 32(11): 2649-2650
doi: 10.3866/PKU.WHXB201610102
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2016, 32(11): 2651-2651
doi: 10.3866/PKU.WHXB201610101
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2016, 32(11): 2652-2662
doi: 10.3866/PKU.WHXB201608262
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Aqueous foams are a typical type of soft matter that are widely used in detergents, cosmetics, food engineering, and oil and gas production because of their relatively small particle size, large superficial area and good fluidity. The stability of a foam plays a crucial role in determining its performance in practical applications. Smart foams, with controllable stability, have been developed recently and their stability can be regulated by external stimuli. This review article mainly focuses on the recent progress in intelligent aqueous foams. To date, smart aqueous foams with temperature, light, magnetic field, pH and CO2-responsive behaviors have been obtained by introducing sensitive groups into foaming agent molecules or adding stimuli-responsive particles to foaming systems. The formation mechanism and properties of different types of smart aqueous foams are summarized and discussed. The potential applications and future prospects of smart foams are also considered.
Aqueous foams are a typical type of soft matter that are widely used in detergents, cosmetics, food engineering, and oil and gas production because of their relatively small particle size, large superficial area and good fluidity. The stability of a foam plays a crucial role in determining its performance in practical applications. Smart foams, with controllable stability, have been developed recently and their stability can be regulated by external stimuli. This review article mainly focuses on the recent progress in intelligent aqueous foams. To date, smart aqueous foams with temperature, light, magnetic field, pH and CO2-responsive behaviors have been obtained by introducing sensitive groups into foaming agent molecules or adding stimuli-responsive particles to foaming systems. The formation mechanism and properties of different types of smart aqueous foams are summarized and discussed. The potential applications and future prospects of smart foams are also considered.
2016, 32(11): 2663-2670
doi: 10.3866/PKU.WHXB201607292
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A new theory has been developed to evaluate the Walden product, W, of ionic liquids using an ion exchange transition model. This model showed that the product (Walden) of molar conductivity and dynamic viscosity is related to the average diameters of the ion pairs and ion clusters of ionic liquids (ILs) with 1:1 charge ratios, namely, different ILs have different W values. Several experiments were conducted to evaluate the validity of this model. Eight different ILs, including five N-alkyl-pyridinium dicyanamide ILs[Cnpy] [DCA] (n=2-6) and three N-alkyl-3-methyllimidazolium serine ILs[Cnmim] [Ser] (n=2-4) were successfully synthesized and evaluated in terms of their conductivity and dynamic viscosity properties. The W values of 33 different ILs were calculated based on their experimentally determined molar conductivity and dynamic viscosity values, and the results revealed that these values were consistent with those of the ion exchange transition model. Taken together, these results demonstrate that W is a key physical parameter for ILs.
A new theory has been developed to evaluate the Walden product, W, of ionic liquids using an ion exchange transition model. This model showed that the product (Walden) of molar conductivity and dynamic viscosity is related to the average diameters of the ion pairs and ion clusters of ionic liquids (ILs) with 1:1 charge ratios, namely, different ILs have different W values. Several experiments were conducted to evaluate the validity of this model. Eight different ILs, including five N-alkyl-pyridinium dicyanamide ILs[Cnpy] [DCA] (n=2-6) and three N-alkyl-3-methyllimidazolium serine ILs[Cnmim] [Ser] (n=2-4) were successfully synthesized and evaluated in terms of their conductivity and dynamic viscosity properties. The W values of 33 different ILs were calculated based on their experimentally determined molar conductivity and dynamic viscosity values, and the results revealed that these values were consistent with those of the ion exchange transition model. Taken together, these results demonstrate that W is a key physical parameter for ILs.
2016, 32(11): 2671-2677
doi: 10.3866/PKU.WHXB201608122
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1H NMR longitudinal relaxation times (T1,exp of the hydroxyl and methyl group) of methanol in supercritical and subcritical gas-like and liquid-like CO2+methanol mixtures were obtained as a function of pressure up to 25 MPa and at 293.15 and 308.15 K, respectively. This study was designed to investigate the mechanism of the spin-lattice relaxation (SLR) time T1 in different phase regions of CO2+methanol as homogenous gas-like, and liquid-like mixtures, and the influence of pressure, temperature, and composition on the relaxation rate was examined. Moreover, the density dependent isotherms of the SLR rates 1/T1,exp were comparatively studied between gas-like and liquid-like binary mixtures. There exists an obvious phase dependent SLR mechanism within the temperature and pressure range carried out herein, that is, the SLR process is dominated by the dipole-dipole (DD) interaction mechanism for both liquid-like mixture and methanol, whereas by the spin-rotation (SR) mechanism for gas-like mixture. Measurement of nuclear magnetic relaxation times can offer micro-dynamic and micro-structural information and are very useful for the study of fluids of strongly interacting molecules. Mutual influence of electric dipoles as well as hydrogen bonds helps determine the structure of the fluid and its molecular dynamics. The present work increases our knowledge of molecular dynamics of alcohols in sub-and supercritical CO2.
1H NMR longitudinal relaxation times (T1,exp of the hydroxyl and methyl group) of methanol in supercritical and subcritical gas-like and liquid-like CO2+methanol mixtures were obtained as a function of pressure up to 25 MPa and at 293.15 and 308.15 K, respectively. This study was designed to investigate the mechanism of the spin-lattice relaxation (SLR) time T1 in different phase regions of CO2+methanol as homogenous gas-like, and liquid-like mixtures, and the influence of pressure, temperature, and composition on the relaxation rate was examined. Moreover, the density dependent isotherms of the SLR rates 1/T1,exp were comparatively studied between gas-like and liquid-like binary mixtures. There exists an obvious phase dependent SLR mechanism within the temperature and pressure range carried out herein, that is, the SLR process is dominated by the dipole-dipole (DD) interaction mechanism for both liquid-like mixture and methanol, whereas by the spin-rotation (SR) mechanism for gas-like mixture. Measurement of nuclear magnetic relaxation times can offer micro-dynamic and micro-structural information and are very useful for the study of fluids of strongly interacting molecules. Mutual influence of electric dipoles as well as hydrogen bonds helps determine the structure of the fluid and its molecular dynamics. The present work increases our knowledge of molecular dynamics of alcohols in sub-and supercritical CO2.
2016, 32(11): 2678-2684
doi: 10.3866/PKU.WHXB201608084
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Cubic nano-cuprous oxides, with four types of particle sizes ranging from 40 to 120 nm, were synthesized via a liquid-phase reduction method. The composition, morphology and structure of the nano-Cu2O particles were characterized by X-ray diffractometry (XRD), Raman microscopy and field emission scanning electronic microscopy (FE-SEM). In-situ microcalorimetry was used to obtain thermodynamic information about the reaction between HNO3 and bulk Cu2O or nano-Cu2O. The surface thermodynamic functions of cubic nano-Cu2O were calculated by a combination of thermodynamic principle and kinetic transition state theory. We develop a thermodynamic model for the cubic nanoparticles based on the thermodynamic model of spherical nanoparticles without bore developed by XUE Yong-Qiang et al. The particle size and temperature effects of surface thermodynamic functions are discussed by comparing the theoretical model with the experimental results. The molar surface Gibbs free energy, molar surface enthalpy and molar surface entropy increased with decreasing particle sizes. Linear trends were found between the reciprocal of particle size and surface thermodynamic functions, which agreed well with the theoretical model for a cube. The molar surface enthalpy and molar surface entropy were increased with rising temperature, whereas the molar surface Gibbs free energy decreased. This work not only enriches and develops the basic theory of nano-thermodynamics, but also provides a novel method and idea for investigating surface thermodynamic functions of nanomaterials and their applications.
Cubic nano-cuprous oxides, with four types of particle sizes ranging from 40 to 120 nm, were synthesized via a liquid-phase reduction method. The composition, morphology and structure of the nano-Cu2O particles were characterized by X-ray diffractometry (XRD), Raman microscopy and field emission scanning electronic microscopy (FE-SEM). In-situ microcalorimetry was used to obtain thermodynamic information about the reaction between HNO3 and bulk Cu2O or nano-Cu2O. The surface thermodynamic functions of cubic nano-Cu2O were calculated by a combination of thermodynamic principle and kinetic transition state theory. We develop a thermodynamic model for the cubic nanoparticles based on the thermodynamic model of spherical nanoparticles without bore developed by XUE Yong-Qiang et al. The particle size and temperature effects of surface thermodynamic functions are discussed by comparing the theoretical model with the experimental results. The molar surface Gibbs free energy, molar surface enthalpy and molar surface entropy increased with decreasing particle sizes. Linear trends were found between the reciprocal of particle size and surface thermodynamic functions, which agreed well with the theoretical model for a cube. The molar surface enthalpy and molar surface entropy were increased with rising temperature, whereas the molar surface Gibbs free energy decreased. This work not only enriches and develops the basic theory of nano-thermodynamics, but also provides a novel method and idea for investigating surface thermodynamic functions of nanomaterials and their applications.
2016, 32(11): 2685-2692
doi: 10.3866/PKU.WHXB201607212
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In this paper, we have used the MP2/6-311++G(2d,2p) method to conduct a detailed investigation of the potential energy surface for the unimolecular dissociation reaction of methyl butanoate (MB). We have also used the Rice-Ramsperger-Kassel-Marcus (RRKM) theory to calculate the rate constants of the canonical and microcanonical systems at temperatures and total energies ranging from 1000 to 5000 K and 451.92 to 1519.52 kJ·mol-1, respectively. The results indicated that there was an obvious anharmonic effect for the TS2, TS4 and TS5 pathways, and that this effect was too pronounced to be neglected for the unimolecular dissociation reactions of MB.
In this paper, we have used the MP2/6-311++G(2d,2p) method to conduct a detailed investigation of the potential energy surface for the unimolecular dissociation reaction of methyl butanoate (MB). We have also used the Rice-Ramsperger-Kassel-Marcus (RRKM) theory to calculate the rate constants of the canonical and microcanonical systems at temperatures and total energies ranging from 1000 to 5000 K and 451.92 to 1519.52 kJ·mol-1, respectively. The results indicated that there was an obvious anharmonic effect for the TS2, TS4 and TS5 pathways, and that this effect was too pronounced to be neglected for the unimolecular dissociation reactions of MB.
2016, 32(11): 2693-2708
doi: 10.3866/PKU.WHXB201608121
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3C-like protease is an extremely important protease involved in the multiplicative process of coronaviruses, including the deadlyMiddle East respiratory syndrome coronavirus (MERS-CoV). 3C-like protease has become a hot research topic in the field of coronavirology. For the first time, a set of ligand-and receptorbased three-dimensional quantitative structure-activity relationships (3D-QSAR) models were carried out via comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) to explore the structure-activity correlation of 43 peptidomimetic inhibitors of the 3C-like protease of the bat coronavirus HKU4 (HKU4-CoV), which belongs to the same 2c lineage as MERS-CoV and shows high sequence similarity with MERS-CoV. Based on the ligand-based alignment, an optimal CoMSIAmodel (yielded by steric, electrostatic, H-bond donor and H-bond acceptor fields) was obtained with good predictive power of Q2=0.522, R2 ncv=0.996 and R2 pre=0.904 (Q2:cross-validated correlation coefficient, R2 ncv:non-cross-validated correlation coefficient, R2 pre:predicted correlation coefficient for the test set of compounds). Molecular docking and molecular dynamics simulations were performed according to this model to further determine the interaction mechanism between ligands and the receptor. The experimental results show:(1) based on the optimal CoMSIAmodel, the 3D contour maps vividly illustrate that the molecular biological activity is influenced by the steric, electrostatic, H-bond donor and H-bond acceptor interactions of molecular groups. (2) Based on the docking analysis, hydrophobicity, crystal water, His166 andGlu169 have important roles in the ligands and receptor binding process. (3) Molecular dynamics (MD) simulations were carried out for further verification of the reliability of the docking model, and provide two new key residues, Ser24 and Gln192, which have two strong hydrogen bonds with the ligands. Some new compounds were obtained based on the modeling that are potential peptidomimetic inhibitors of 3C-like protease. These results help establish the binding mechanism between 3C-like protease and peptidomimetic inhibitors, and provide a valuable reference for future anti-MERS-CoV drug design.
3C-like protease is an extremely important protease involved in the multiplicative process of coronaviruses, including the deadlyMiddle East respiratory syndrome coronavirus (MERS-CoV). 3C-like protease has become a hot research topic in the field of coronavirology. For the first time, a set of ligand-and receptorbased three-dimensional quantitative structure-activity relationships (3D-QSAR) models were carried out via comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) to explore the structure-activity correlation of 43 peptidomimetic inhibitors of the 3C-like protease of the bat coronavirus HKU4 (HKU4-CoV), which belongs to the same 2c lineage as MERS-CoV and shows high sequence similarity with MERS-CoV. Based on the ligand-based alignment, an optimal CoMSIAmodel (yielded by steric, electrostatic, H-bond donor and H-bond acceptor fields) was obtained with good predictive power of Q2=0.522, R2 ncv=0.996 and R2 pre=0.904 (Q2:cross-validated correlation coefficient, R2 ncv:non-cross-validated correlation coefficient, R2 pre:predicted correlation coefficient for the test set of compounds). Molecular docking and molecular dynamics simulations were performed according to this model to further determine the interaction mechanism between ligands and the receptor. The experimental results show:(1) based on the optimal CoMSIAmodel, the 3D contour maps vividly illustrate that the molecular biological activity is influenced by the steric, electrostatic, H-bond donor and H-bond acceptor interactions of molecular groups. (2) Based on the docking analysis, hydrophobicity, crystal water, His166 andGlu169 have important roles in the ligands and receptor binding process. (3) Molecular dynamics (MD) simulations were carried out for further verification of the reliability of the docking model, and provide two new key residues, Ser24 and Gln192, which have two strong hydrogen bonds with the ligands. Some new compounds were obtained based on the modeling that are potential peptidomimetic inhibitors of 3C-like protease. These results help establish the binding mechanism between 3C-like protease and peptidomimetic inhibitors, and provide a valuable reference for future anti-MERS-CoV drug design.
2016, 32(11): 2709-2716
doi: 10.3866/PKU.WHXB201609132
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Austin-Petersson-Frisch (APF) is a new hybrid density functional method that combines B3PW91 and PBE0. APF-D provides an additional empirical dispersion correction method based on a spherical atom model (SAM), which is different from the Grimme's empirical dispersion correction method. APF-D accurately describes the binding energy and the potential energy surfaces of complexes of noble gas atoms and small hydrocarbon dimers. However, APF-D is not accepted as a standard method to study intermolecular interactions because the results often show a large deviation from the normal range when using the APF-D method to calculate the binding energy of hydrogen bonded complexes, C-H…π and π…π interactions. Our research identified that such a deviation arises from some long-range dispersion that has been double counted by the APF function and the SAM dispersion correction. Therefore, we propose an improved APF-D method, termed APF-D*. By taking advantage of ζ, which is independent of SAM dispersion, we were able to solve effectively the problem of excessive dispersion compensation in APF-D. By comparing the results from S66 and L7 benchmark sets, we find that APF-D* greatly improved the precision of calculations over the traditional APF-D method. The overall accuracy of APF-D* was found to be comparable to or better than current leading DFT methods, such as B3LYP-D3 and ωB97X-D. However, both B3LYP-D3 and ωB97X-D have a much larger computational cost than APF-D*. We believe that APF-D* is a better method to calculate of the intermolecular energy of large molecules.
Austin-Petersson-Frisch (APF) is a new hybrid density functional method that combines B3PW91 and PBE0. APF-D provides an additional empirical dispersion correction method based on a spherical atom model (SAM), which is different from the Grimme's empirical dispersion correction method. APF-D accurately describes the binding energy and the potential energy surfaces of complexes of noble gas atoms and small hydrocarbon dimers. However, APF-D is not accepted as a standard method to study intermolecular interactions because the results often show a large deviation from the normal range when using the APF-D method to calculate the binding energy of hydrogen bonded complexes, C-H…π and π…π interactions. Our research identified that such a deviation arises from some long-range dispersion that has been double counted by the APF function and the SAM dispersion correction. Therefore, we propose an improved APF-D method, termed APF-D*. By taking advantage of ζ, which is independent of SAM dispersion, we were able to solve effectively the problem of excessive dispersion compensation in APF-D. By comparing the results from S66 and L7 benchmark sets, we find that APF-D* greatly improved the precision of calculations over the traditional APF-D method. The overall accuracy of APF-D* was found to be comparable to or better than current leading DFT methods, such as B3LYP-D3 and ωB97X-D. However, both B3LYP-D3 and ωB97X-D have a much larger computational cost than APF-D*. We believe that APF-D* is a better method to calculate of the intermolecular energy of large molecules.
2016, 32(11): 2717-2723
doi: 10.3866/PKU.WHXB201607271
Abstract:
Mercury emission from coal during chemical-looping combustion (CLC) is an inevitable process, which can lead to adverse interactions with the surface of the oxygen carrier, thereby affecting the interfacial redox reactions. Density functional theory calculations were performed to investigate the mechanism of elemental mercury (Hg0) adsorption and the synergetic effect of Hg0 on the catalytic decomposition of CO over a perfect surface (Fe2O3[001]), as well as a series of reduced surfaces (Fe2O2.75, Fe2O2.5, Fe2O2.25, Fe2O1.625, Fe2O0.875, Fe2O0.375 and Fe) during a deep CLC process. In this study, Hg0 was physically adsorbed on to a perfect Fe2O3 surface, and then chemically adsorbed on to a series of reduced surfaces. The adsorption of Hg0 inhibited the formation of meaningful interactions between CO and Fe2O3[Fe2O2.75, Fe2O2.5 and Fe2O2.25] and hindered the efficient transport of oxygen to oxidize CO into CO2. In contrast, this process promoted the interactions between CO and Fe2O1.625[Fe2O0.875, Fe2O0.375, and Fe], favoring the catalytic decomposition of CO on these surfaces, which accelerated the carbon deposit reducing CLC efficiency. Rationally controlling the reduction degree of the oxygen carrier could therefore be used to either decrease the adsorption of Hg0 or depress the deposition of carbon, which are both crucial for the optimization of CLC processes.
Mercury emission from coal during chemical-looping combustion (CLC) is an inevitable process, which can lead to adverse interactions with the surface of the oxygen carrier, thereby affecting the interfacial redox reactions. Density functional theory calculations were performed to investigate the mechanism of elemental mercury (Hg0) adsorption and the synergetic effect of Hg0 on the catalytic decomposition of CO over a perfect surface (Fe2O3[001]), as well as a series of reduced surfaces (Fe2O2.75, Fe2O2.5, Fe2O2.25, Fe2O1.625, Fe2O0.875, Fe2O0.375 and Fe) during a deep CLC process. In this study, Hg0 was physically adsorbed on to a perfect Fe2O3 surface, and then chemically adsorbed on to a series of reduced surfaces. The adsorption of Hg0 inhibited the formation of meaningful interactions between CO and Fe2O3[Fe2O2.75, Fe2O2.5 and Fe2O2.25] and hindered the efficient transport of oxygen to oxidize CO into CO2. In contrast, this process promoted the interactions between CO and Fe2O1.625[Fe2O0.875, Fe2O0.375, and Fe], favoring the catalytic decomposition of CO on these surfaces, which accelerated the carbon deposit reducing CLC efficiency. Rationally controlling the reduction degree of the oxygen carrier could therefore be used to either decrease the adsorption of Hg0 or depress the deposition of carbon, which are both crucial for the optimization of CLC processes.
2016, 32(11): 2724-2730
doi: 10.3866/PKU.WHXB201607272
Abstract:
Mixed halide perovskites of MAPbI3-xBrx and MAPbI3-xClx (MA=CH3NH3) with film thickness of about 300 nm were synthesized through the Br or Cl doping, thanks to the two steps deposition of controlled concentration of the precursor solution and the intramolecular exchange of DMSO molecules intercalated in PbI2 (PbI2(DMSO) complex) with MAX (X=I, Br) or MAX (X=I, Cl), respectively. The doping of Br or Cl in the perovskite film can improve the photovoltaic performance of PSCs with the precursor of MAX contains 5% (in mole fraction, same below) MABr or 15% MACl, respectively, while further increase in the content of MABr or MACl in the precursor did not lead to significant changes in doping amounts, but small white particles or pin-holes were formed in mixed perovskite materials, therefore resulted in adverse effects on the performance of solar cells. The MAPbI3-xBrx perovskite solar cells with 5% MABr in precursor solution showed a power conversion efficiency (PCE) of 13.2%, and the MAPbI3-xClx perovskite solar cells with 15% MACl in precursor solution showed the highest PCE of 13.5%.
Mixed halide perovskites of MAPbI3-xBrx and MAPbI3-xClx (MA=CH3NH3) with film thickness of about 300 nm were synthesized through the Br or Cl doping, thanks to the two steps deposition of controlled concentration of the precursor solution and the intramolecular exchange of DMSO molecules intercalated in PbI2 (PbI2(DMSO) complex) with MAX (X=I, Br) or MAX (X=I, Cl), respectively. The doping of Br or Cl in the perovskite film can improve the photovoltaic performance of PSCs with the precursor of MAX contains 5% (in mole fraction, same below) MABr or 15% MACl, respectively, while further increase in the content of MABr or MACl in the precursor did not lead to significant changes in doping amounts, but small white particles or pin-holes were formed in mixed perovskite materials, therefore resulted in adverse effects on the performance of solar cells. The MAPbI3-xBrx perovskite solar cells with 5% MABr in precursor solution showed a power conversion efficiency (PCE) of 13.2%, and the MAPbI3-xClx perovskite solar cells with 15% MACl in precursor solution showed the highest PCE of 13.5%.
2016, 32(11): 2731-2736
doi: 10.3866/PKU.WHXB201608232
Abstract:
Asemiconductor heterostructure of TiO2/CdS/cobalt phosphate water oxidation catalyst (Co-Pi WOC) photoanode was fabricated by the successive ionic layer adsorption and reaction (SILAR) procedure and photoassisted electro-deposition. The structure, morphologys and magnetic properties of the resultant particles were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). CdS and Co-Pi quantum dots loaded on to the TiO2 nanofilm. The TiO2/CdS/Co-Pi photoanode had an initial photocurrent of 1.3 mA·cm-2 and a stable level of 0.5 mA·cm-2. A relatively stable level was maintained under visible light irradiation in neutral solution, especially at the low bias voltage of 0 V (vs Ag/AgCl). In this system, CdS quantum dots serve as the light absorber and generate electron holes; the Co-Pi WOC acts as a hole transfer layer that can transfer the hole for water oxidation; and the TiO2 is the electron conductor for efficient charge transfer to the cathode to actualize proton reduction.
Asemiconductor heterostructure of TiO2/CdS/cobalt phosphate water oxidation catalyst (Co-Pi WOC) photoanode was fabricated by the successive ionic layer adsorption and reaction (SILAR) procedure and photoassisted electro-deposition. The structure, morphologys and magnetic properties of the resultant particles were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). CdS and Co-Pi quantum dots loaded on to the TiO2 nanofilm. The TiO2/CdS/Co-Pi photoanode had an initial photocurrent of 1.3 mA·cm-2 and a stable level of 0.5 mA·cm-2. A relatively stable level was maintained under visible light irradiation in neutral solution, especially at the low bias voltage of 0 V (vs Ag/AgCl). In this system, CdS quantum dots serve as the light absorber and generate electron holes; the Co-Pi WOC acts as a hole transfer layer that can transfer the hole for water oxidation; and the TiO2 is the electron conductor for efficient charge transfer to the cathode to actualize proton reduction.
2016, 32(11): 2737-2744
doi: 10.3866/PKU.WHXB201609072
Abstract:
Fe3O4/rGO nanocomposites were prepared by hydrothermal method using Fe(OH)3 as precursor of magnetite nanoparticles, graphene oxide (GO) as precursor of reduced graphene oxide (rGO), hydrazine and trisodium citrate as mixed reducing agent. The morphologies, structures and compositions of the products were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The electrochemical characteristics of assembled coin-type cells versus metallic lithium were evaluated by cyclic voltammetry and galvanostatic charge-discharge. The uniform morphology, high reductive level of rGO and the role of rGO buffering the volume changes of Fe3O4 nanoparticles in the charging-discharging process can be responsible for the good electrochemical performance of Fe3O4/rGO nanocomposites.
Fe3O4/rGO nanocomposites were prepared by hydrothermal method using Fe(OH)3 as precursor of magnetite nanoparticles, graphene oxide (GO) as precursor of reduced graphene oxide (rGO), hydrazine and trisodium citrate as mixed reducing agent. The morphologies, structures and compositions of the products were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The electrochemical characteristics of assembled coin-type cells versus metallic lithium were evaluated by cyclic voltammetry and galvanostatic charge-discharge. The uniform morphology, high reductive level of rGO and the role of rGO buffering the volume changes of Fe3O4 nanoparticles in the charging-discharging process can be responsible for the good electrochemical performance of Fe3O4/rGO nanocomposites.
2016, 32(11): 2745-2752
doi: 10.3866/PKU.WHXB201608083
Abstract:
We devised and fabricated a Pd/Ni(OH)2 composite catalyst with low noble metal content that grows in situ on nickel foam (NF) using the hydrothermal synthesis method. The morphology and microstructure of the catalyst were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The hydrogen evolution performance of the composite catalyst was evaluated by linear scanning voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CP). The composite catalyst exhibited a special nanostructure consisting of an ultra-thin Ni(OH)2 film growth on the surface of the nickel foam with palladium nanoparticles uniformly embedded in the Ni(OH)2 thin film. The Ni(OH)2 on the surface of the catalyst might considerably promote the dissociation of water and the formation of hydrogen intermediates (Had) that subsequently adsorbed on the nearby Pd and quickly recombined into hydrogen molecules. The composite catalyst exhibits a synergistic effect for the hydrogen evolution reaction (HER), which might decrease the over-potential of hydrogen evolution and enhance the activity of the hydrogen evolution reaction. Growing the composite catalyst in situ on the nickel foam effectively improved the stability of the catalyst for the HER in alkaline solutions.
We devised and fabricated a Pd/Ni(OH)2 composite catalyst with low noble metal content that grows in situ on nickel foam (NF) using the hydrothermal synthesis method. The morphology and microstructure of the catalyst were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The hydrogen evolution performance of the composite catalyst was evaluated by linear scanning voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CP). The composite catalyst exhibited a special nanostructure consisting of an ultra-thin Ni(OH)2 film growth on the surface of the nickel foam with palladium nanoparticles uniformly embedded in the Ni(OH)2 thin film. The Ni(OH)2 on the surface of the catalyst might considerably promote the dissociation of water and the formation of hydrogen intermediates (Had) that subsequently adsorbed on the nearby Pd and quickly recombined into hydrogen molecules. The composite catalyst exhibits a synergistic effect for the hydrogen evolution reaction (HER), which might decrease the over-potential of hydrogen evolution and enhance the activity of the hydrogen evolution reaction. Growing the composite catalyst in situ on the nickel foam effectively improved the stability of the catalyst for the HER in alkaline solutions.
2016, 32(11): 2753-2760
doi: 10.3866/PKU.WHXB201608231
Abstract:
Bio-based surfactants have attracted increasing attention because they are made from renewable resources and have excellent surface/interfacial properties. In this study we prepared a novel bio-based branched alkylbenzene sulfonate surfactant by a four-step route using renewable oleic acids as starting materials. We evaluated the surface behavior, wettability, and biodegradability of our surfactant. The surfactant, 4-(1-heptadecyl) benzene sodium sulfonate (9ΦC17S), was synthesized using a facile four-step route involving alkylation, decarboxylation, sulfonation and neutralization, respectively. The chemical structure of 4-(1-heptadecyl) benzene sodium sulfonate was confirmed by infrared (IR) spectroscopy, electrospray ionization high resolution mass spectrometry (ESI HRMS) and 1H nuclear magnetic resonance (1H NMR) spectroscopy. The surfactant demonstrated an excellent surface tension of 32.54 mN·m-1 at the critical micelle concentration (CMC) of 317.5 mg·L-1 and outstanding interfacial tension of ~10-2 mN·m-1 at 8.36×104 mg·L-1 with 8.48×104 mg·L-1 Na2CO3. The surfactant also showed good biodegradability with an ultimate biodegradation score of 2.99. The surfactant had good wettability with an air/water/solid contact angle (θaverage) of 63.08° for a 0.500 g·L-1 9ΦC17S solution. This novel bio-based branched surfactant contributes to the structural diversity of biobased surfactants from renewable feedstock.
Bio-based surfactants have attracted increasing attention because they are made from renewable resources and have excellent surface/interfacial properties. In this study we prepared a novel bio-based branched alkylbenzene sulfonate surfactant by a four-step route using renewable oleic acids as starting materials. We evaluated the surface behavior, wettability, and biodegradability of our surfactant. The surfactant, 4-(1-heptadecyl) benzene sodium sulfonate (9ΦC17S), was synthesized using a facile four-step route involving alkylation, decarboxylation, sulfonation and neutralization, respectively. The chemical structure of 4-(1-heptadecyl) benzene sodium sulfonate was confirmed by infrared (IR) spectroscopy, electrospray ionization high resolution mass spectrometry (ESI HRMS) and 1H nuclear magnetic resonance (1H NMR) spectroscopy. The surfactant demonstrated an excellent surface tension of 32.54 mN·m-1 at the critical micelle concentration (CMC) of 317.5 mg·L-1 and outstanding interfacial tension of ~10-2 mN·m-1 at 8.36×104 mg·L-1 with 8.48×104 mg·L-1 Na2CO3. The surfactant also showed good biodegradability with an ultimate biodegradation score of 2.99. The surfactant had good wettability with an air/water/solid contact angle (θaverage) of 63.08° for a 0.500 g·L-1 9ΦC17S solution. This novel bio-based branched surfactant contributes to the structural diversity of biobased surfactants from renewable feedstock.
2016, 32(11): 2761-2768
doi: 10.3866/PKU.WHXB201608261
Abstract:
(3-Acrylamidopropyl)trimethylammonium chloride (ATC), acrylamide and montmorillonite (MMT) without organic modification were synthesized through free radical polymerization to strengthen the mechanical properties of hydrogels. MMT platelets were considered as chemical "plane" cross-linkers different from "point" cross-linkers because of the cation-exchange reaction between MMT and ATC (cationic monomer) during the synthesis of hydrogels, while a double network was used to improve the mechanical properties of the hydrogels. Investigations of compressive and tensile properties indicated that compressive modulus and stress, fracture stress, ultimate strain and Young's modulus were significantly improved in the presence of MMT. The mechanical properties of double-network hydrogels improved with increasing monomer concentration of the first network. Scanning electron microscopy (SEM) revealed that large quantities of micro-network structures were located in the pores and the formation of embedded micro-network structures led to an increase in the compressive strength and toughness. Moreover, the gels with ATC exhibited good antibacterial effects against E. coli and S. aureus. These developments provide a new route to prepare hydrogels with high mechanical properties.
(3-Acrylamidopropyl)trimethylammonium chloride (ATC), acrylamide and montmorillonite (MMT) without organic modification were synthesized through free radical polymerization to strengthen the mechanical properties of hydrogels. MMT platelets were considered as chemical "plane" cross-linkers different from "point" cross-linkers because of the cation-exchange reaction between MMT and ATC (cationic monomer) during the synthesis of hydrogels, while a double network was used to improve the mechanical properties of the hydrogels. Investigations of compressive and tensile properties indicated that compressive modulus and stress, fracture stress, ultimate strain and Young's modulus were significantly improved in the presence of MMT. The mechanical properties of double-network hydrogels improved with increasing monomer concentration of the first network. Scanning electron microscopy (SEM) revealed that large quantities of micro-network structures were located in the pores and the formation of embedded micro-network structures led to an increase in the compressive strength and toughness. Moreover, the gels with ATC exhibited good antibacterial effects against E. coli and S. aureus. These developments provide a new route to prepare hydrogels with high mechanical properties.
2016, 32(11): 2769-2775
doi: 10.3866/PKU.WHXB201607262
Abstract:
Rh, Mn and Li were supported on SBA-15 samples that had been calcined at 550, 700, 800, and 900℃, using an incipient co-impregnation technique. The catalytic performances of these materials were subsequently evaluated for the hydrogenation of carbon monoxide. The catalysts were characterized by means of N2 adsorption-desorption, X-ray diffraction, transmission electron microscopy, H2 chemisorption, and Fourier transform infrared spectroscopy. The structure of the SBA-15 support remained unchanged even after its calcination at 900℃. However, the specific surface area, pore size, and total pore volume of SBA-15 decreased from 842.6 m2·g-1, 9.57 nm, and 1.18 cm3·g-1 to 246.4 m2·g-1, 5.62 nm, and 0.34 cm3·g-1, respectively, when the calcination temperature increased from 550 to 900℃. In addition, the Rh particle size increased in the range of 1.5-4.0 nm with increasing calcination temperature. Furthermore, the Rh particles showed a greater tendency towards the mesopores of support when they were calcined at high temperatures, which could be attributed to the reduced number of micropores. These changes therefore made it easier for H2 and CO to interact with the Rh particles immobilized on the supports calcined at high temperatures. High levels of activity and selectivity towards C2+ oxygenates were therefore obtained on the Rh-Mn-Li/SBA-15 prepared using the SBA-15 calcined at 900℃.
Rh, Mn and Li were supported on SBA-15 samples that had been calcined at 550, 700, 800, and 900℃, using an incipient co-impregnation technique. The catalytic performances of these materials were subsequently evaluated for the hydrogenation of carbon monoxide. The catalysts were characterized by means of N2 adsorption-desorption, X-ray diffraction, transmission electron microscopy, H2 chemisorption, and Fourier transform infrared spectroscopy. The structure of the SBA-15 support remained unchanged even after its calcination at 900℃. However, the specific surface area, pore size, and total pore volume of SBA-15 decreased from 842.6 m2·g-1, 9.57 nm, and 1.18 cm3·g-1 to 246.4 m2·g-1, 5.62 nm, and 0.34 cm3·g-1, respectively, when the calcination temperature increased from 550 to 900℃. In addition, the Rh particle size increased in the range of 1.5-4.0 nm with increasing calcination temperature. Furthermore, the Rh particles showed a greater tendency towards the mesopores of support when they were calcined at high temperatures, which could be attributed to the reduced number of micropores. These changes therefore made it easier for H2 and CO to interact with the Rh particles immobilized on the supports calcined at high temperatures. High levels of activity and selectivity towards C2+ oxygenates were therefore obtained on the Rh-Mn-Li/SBA-15 prepared using the SBA-15 calcined at 900℃.
2016, 32(11): 2776-2784
doi: 10.3866/PKU.WHXB201608302
Abstract:
Aseries of Y2O3-modified Ni/SiO2 catalysts were synthesized by a conventional impregnation method. Catalytic performances for the partial oxidation of methane (POM) to synthesis gas were investigated. The addition of Y2O3 promotes a decrease in size of Ni particles supported on silica, increased the dispersion of Ni particles, and enhanced the interaction between Ni and silica. These properties gave the catalysts increased anti-sintering and resistance to carbon deposits. The catalytic behaviors of the Ni-based catalysts for POM were significantly improved when Y2O3 was introduced.
Aseries of Y2O3-modified Ni/SiO2 catalysts were synthesized by a conventional impregnation method. Catalytic performances for the partial oxidation of methane (POM) to synthesis gas were investigated. The addition of Y2O3 promotes a decrease in size of Ni particles supported on silica, increased the dispersion of Ni particles, and enhanced the interaction between Ni and silica. These properties gave the catalysts increased anti-sintering and resistance to carbon deposits. The catalytic behaviors of the Ni-based catalysts for POM were significantly improved when Y2O3 was introduced.
2016, 32(11): 2785-2793
doi: 10.3866/PKU.WHXB201608304
Abstract:
A two-step method was developed for the selective synthesis of porous ZnO nanorods (undoped and Cu doped):first, Zn[C6H4(COO)2]·H2O and Cu doped Zn[C6H4(COO)2]·H2O nanorods were synthesized via the hydrothermal reaction of Zn(NO3)2·6H2O, NaOH, KHC8H4O4, and Cu(NO3)2·3H2O at 120℃ for 6 h; second, porous undoped and doped ZnO nanorods were obtained by thermal decomposition of the precursors in air at 500℃ for 2 h, respectively. The porous ZnO nanorods were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible (UV-Vis) spectroscopy. The photocatalytic degradation of rhodamine B (RhB) aqueous solution shows that the porous Cu-doped ZnO nanorods have the highest photodegradation performance with visible light and acetaldehyde (CH3CHO) gas degradation. These results are because of the special interface structures of the catalysts and fast separation of its photogenerated charge carriers. These favorable photocatalytic properties of the doped microstructures demonstrate their potential for degradation of wastewater and aldehydes.
A two-step method was developed for the selective synthesis of porous ZnO nanorods (undoped and Cu doped):first, Zn[C6H4(COO)2]·H2O and Cu doped Zn[C6H4(COO)2]·H2O nanorods were synthesized via the hydrothermal reaction of Zn(NO3)2·6H2O, NaOH, KHC8H4O4, and Cu(NO3)2·3H2O at 120℃ for 6 h; second, porous undoped and doped ZnO nanorods were obtained by thermal decomposition of the precursors in air at 500℃ for 2 h, respectively. The porous ZnO nanorods were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible (UV-Vis) spectroscopy. The photocatalytic degradation of rhodamine B (RhB) aqueous solution shows that the porous Cu-doped ZnO nanorods have the highest photodegradation performance with visible light and acetaldehyde (CH3CHO) gas degradation. These results are because of the special interface structures of the catalysts and fast separation of its photogenerated charge carriers. These favorable photocatalytic properties of the doped microstructures demonstrate their potential for degradation of wastewater and aldehydes.
2016, 32(11): 2794-2802
doi: 10.3866/PKU.WHXB201609073
Abstract:
Macroporous polymer foams (MPFs) were prepared through oil-in-water (O/W) Pickering high internal phase emulsions (HIPEs) stabilized by the natural clay halloysite nanotube (HNT) nanoparticles with the addition of small amounts of the nonionic surfactant Tween 85. The resulting MPFs were characterized, and the results showed an open cell structure with interconnected pores and a hydrophilic surface with a suspended state in aqueous solution. These features were beneficial for the adsorption of pyrethroids. Moreover, the adsorption of λ-cyhalothrin on MPFs was examined to determine the kinetic and equilibrium data of the adsorption process. The findings of the kinetic and equilibrium studies revealed that a pseudo-second-order kinetic model and the Langmuir isotherm were the best fitted models (R2>0.99), implying that the process of adsorption is a monolayer and chemically reactive. In addition, the maximum adsorption capacity and equilibrium time for λ-cyhalothrin on MPFs were estimated to be 23.98 μmol·g-1 and 240 min at 298 K. Increasing the temperature led to an increase in adsorption capacity. Increasing the initial concentration of λ-cyhalothrin led to an increase in clear adsorption capacity. Finally, the suspended MPFs represent a promising and reliable adsorbent for the removal of hydrophobic organic pollutants from aqueous solutions.
Macroporous polymer foams (MPFs) were prepared through oil-in-water (O/W) Pickering high internal phase emulsions (HIPEs) stabilized by the natural clay halloysite nanotube (HNT) nanoparticles with the addition of small amounts of the nonionic surfactant Tween 85. The resulting MPFs were characterized, and the results showed an open cell structure with interconnected pores and a hydrophilic surface with a suspended state in aqueous solution. These features were beneficial for the adsorption of pyrethroids. Moreover, the adsorption of λ-cyhalothrin on MPFs was examined to determine the kinetic and equilibrium data of the adsorption process. The findings of the kinetic and equilibrium studies revealed that a pseudo-second-order kinetic model and the Langmuir isotherm were the best fitted models (R2>0.99), implying that the process of adsorption is a monolayer and chemically reactive. In addition, the maximum adsorption capacity and equilibrium time for λ-cyhalothrin on MPFs were estimated to be 23.98 μmol·g-1 and 240 min at 298 K. Increasing the temperature led to an increase in adsorption capacity. Increasing the initial concentration of λ-cyhalothrin led to an increase in clear adsorption capacity. Finally, the suspended MPFs represent a promising and reliable adsorbent for the removal of hydrophobic organic pollutants from aqueous solutions.
2016, 32(11): 2803-2810
doi: 10.3866/PKU.WHXB201607291
Abstract:
Highly dispersed Ni-Ce-Zr mixed oxides supported on mesoporous γ-alumina (Ni-Ce-Zr/γ-MA) were prepared by a citric acid (CA)-assisted impregnation method and evaluated as catalysts for the methanation of CO2 with H2. The effects of the CA content of the reaction solution on the physicochemical properties and the catalytic performance of the Ni-Ce-Zr/γ-MA catalysts were investigated in detail. The addition of CA promoted the dispersion of the Ni-Ce-Zr oxide species on the γ-alumina surface and improved the interactions between the Ni oxide species and the support, resulting in the formation of homogeneously dispersed Ni nanoparticles in the γ-MA frameworks upon reduction with H2. The resulting Ni-Ce-Zr/γ-MA catalysts were highly active and showed almost 100% selectivity for CH4 during the methanation of CO2 at temperatures in the range of 150-400℃. Notably, the catalytic activity increased as the molar ratio of CA/(Ni+Ce+Zr) increased in the range of 0-2. This effect was most likely caused by the associated decrease in the Ni particle size and the improved electronic and structural properties of the Ni-Ce-ZrOx species. The results of a stability test for the Ni-Ce-Zr/γ-MA catalyst prepared with a CA/(Ni+Ce+Zr) molar ratio of 1.0 showed that there was only a 7% decrease in the CO2 conversion following a reaction time of 300 h at 300℃ with negligible coke deposition, indicating excellent catalytic stability and good anti-coking ability of these systems for the methanation of CO2.
Highly dispersed Ni-Ce-Zr mixed oxides supported on mesoporous γ-alumina (Ni-Ce-Zr/γ-MA) were prepared by a citric acid (CA)-assisted impregnation method and evaluated as catalysts for the methanation of CO2 with H2. The effects of the CA content of the reaction solution on the physicochemical properties and the catalytic performance of the Ni-Ce-Zr/γ-MA catalysts were investigated in detail. The addition of CA promoted the dispersion of the Ni-Ce-Zr oxide species on the γ-alumina surface and improved the interactions between the Ni oxide species and the support, resulting in the formation of homogeneously dispersed Ni nanoparticles in the γ-MA frameworks upon reduction with H2. The resulting Ni-Ce-Zr/γ-MA catalysts were highly active and showed almost 100% selectivity for CH4 during the methanation of CO2 at temperatures in the range of 150-400℃. Notably, the catalytic activity increased as the molar ratio of CA/(Ni+Ce+Zr) increased in the range of 0-2. This effect was most likely caused by the associated decrease in the Ni particle size and the improved electronic and structural properties of the Ni-Ce-ZrOx species. The results of a stability test for the Ni-Ce-Zr/γ-MA catalyst prepared with a CA/(Ni+Ce+Zr) molar ratio of 1.0 showed that there was only a 7% decrease in the CO2 conversion following a reaction time of 300 h at 300℃ with negligible coke deposition, indicating excellent catalytic stability and good anti-coking ability of these systems for the methanation of CO2.
2016, 32(11): 2811-2818
doi: 10.3866/PKU.WHXB201609131
Abstract:
Human serum albumin (HSA) has two main drug binding sites termed Site I and Site II. Most small molecules like ibuprofen (a well-known anti-inflammatory drug) bind to Site II preferentially. In this study, molecular simulation methods were used to investigate the dynamic binding process of ibuprofen to Site II. A system of 50 ibuprofen molecules distributed randomly around HSA was constructed. After a 50-ns molecular dynamics simulation, one ibuprofen molecule bound stably to Site II. Based on trajectory analysis of this ibuprofen molecule, the binding process of ibuprofen onto Site II can be divided into four phases:(i) long-range attraction; (ii) adjustment on the surface; (iii) entering to Site II pocket; and (iv) stable binding at Site II. After evaluating van der Waals' and electrostatic interaction energies during the binding process, it was found that the initial major driving force involves electrostatic attractions. Subsequently, ibuprofen locks between two polar regions on the surface near Site II and then moves to Site II. Ibuprofen then enters the pocket of Site II by combinatorial effects of polar and hydrophobic residues nearby the entrance of Site II. Electrostatic and hydrophobic interactions form the stable binding of ibuprofen in Site II. The molecular surface near Site II was observed to change significantly during binding, which indicates an induced fit mechanism. The binding mode obtained with molecular simulations is consistent with the crystal structure of the ibuprofen-HSA complex. The results show that molecular simulations would help to evaluate the dynamic binding processes of small molecules to proteins and improve our understanding of the binding mechanisms at the molecular level.
Human serum albumin (HSA) has two main drug binding sites termed Site I and Site II. Most small molecules like ibuprofen (a well-known anti-inflammatory drug) bind to Site II preferentially. In this study, molecular simulation methods were used to investigate the dynamic binding process of ibuprofen to Site II. A system of 50 ibuprofen molecules distributed randomly around HSA was constructed. After a 50-ns molecular dynamics simulation, one ibuprofen molecule bound stably to Site II. Based on trajectory analysis of this ibuprofen molecule, the binding process of ibuprofen onto Site II can be divided into four phases:(i) long-range attraction; (ii) adjustment on the surface; (iii) entering to Site II pocket; and (iv) stable binding at Site II. After evaluating van der Waals' and electrostatic interaction energies during the binding process, it was found that the initial major driving force involves electrostatic attractions. Subsequently, ibuprofen locks between two polar regions on the surface near Site II and then moves to Site II. Ibuprofen then enters the pocket of Site II by combinatorial effects of polar and hydrophobic residues nearby the entrance of Site II. Electrostatic and hydrophobic interactions form the stable binding of ibuprofen in Site II. The molecular surface near Site II was observed to change significantly during binding, which indicates an induced fit mechanism. The binding mode obtained with molecular simulations is consistent with the crystal structure of the ibuprofen-HSA complex. The results show that molecular simulations would help to evaluate the dynamic binding processes of small molecules to proteins and improve our understanding of the binding mechanisms at the molecular level.
