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2017 Volume 33 Issue 6
2017, 33(6):
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2017, 33(6): 1071-1072
doi: 10.3866/PKU.WHXB201704061
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2017, 33(6): 1073-1074
doi: 10.3866/PKU.WHXB201704122
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2017, 33(6): 1075-1076
doi: 10.3866/PKU.WHXB201704062
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2017, 33(6): 1077-1078
doi: 10.3866/PKU.WHXB201704063
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2017, 33(6): 1079-1080
doi: 10.3866/PKU.WHXB201704121
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2017, 33(6): 1081-1082
doi: 10.3866/PKU.WHXB201704073
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2017, 33(6): 1083-1084
doi: 10.3866/PKU.WHXB201704134
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2017, 33(6): 1085-1107
doi: 10.3866/PKU.WHXB201704114
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Lithium-ion batteries have been extensively studied due to their excellent electrochemical performance as an effective energy storage device for sustainable energy sources. The key to the development and application of this technology is the improvement of electrode materials. LiFePO4 has captured the attention of researchers both home and abroad as a potential cathode material for lithium-ion batteries because of its long cycle life, energy density, stable charge/discharge performance, good thermal stability, high safety, light weight and low toxicity. However, there are still some technical bottlenecks in the application of LiFePO4, such as relatively low conductivity, low diffusion coefficient of lithium ions, and low tap density. Moreover, the cycle performance, low-temperature characteristics, and rate performance are not ideal, restricting its application and development. In recent years, researchers have sought to solve these problems by improving the preparation process and attempting related modifications. In this paper, we have provided a systemic review of the structure, electrochemical reaction mechanism, preparation, and modification of LiFePO4. The main problems associated with LiFePO4 cathode materials and possible solutions are discussed. We have also investigated the future research direction and application prospect of LiFePO4 cathode materials.
Lithium-ion batteries have been extensively studied due to their excellent electrochemical performance as an effective energy storage device for sustainable energy sources. The key to the development and application of this technology is the improvement of electrode materials. LiFePO4 has captured the attention of researchers both home and abroad as a potential cathode material for lithium-ion batteries because of its long cycle life, energy density, stable charge/discharge performance, good thermal stability, high safety, light weight and low toxicity. However, there are still some technical bottlenecks in the application of LiFePO4, such as relatively low conductivity, low diffusion coefficient of lithium ions, and low tap density. Moreover, the cycle performance, low-temperature characteristics, and rate performance are not ideal, restricting its application and development. In recent years, researchers have sought to solve these problems by improving the preparation process and attempting related modifications. In this paper, we have provided a systemic review of the structure, electrochemical reaction mechanism, preparation, and modification of LiFePO4. The main problems associated with LiFePO4 cathode materials and possible solutions are discussed. We have also investigated the future research direction and application prospect of LiFePO4 cathode materials.
2017, 33(6): 1108-1113
doi: 10.3866/PKU.WHXB201703222
Abstract:
Based on zero-order Bragg-Williams approximation, a new statistic thermodynamic model is presented herein. The distinctive feature of the new model is that an apparent compressibility factor α is introduced to correct the volume change of high-pressure gases and ensure no loop-like curves are obtained in the fitting results. The new model is successfully applied to investigate hydrogen absorption on metal powders. Our results indicate that the model works very well and can be used to predict PCT curves at different temperatures. Hence, our new model exhibits significant potential for application in practical systems.
Based on zero-order Bragg-Williams approximation, a new statistic thermodynamic model is presented herein. The distinctive feature of the new model is that an apparent compressibility factor α is introduced to correct the volume change of high-pressure gases and ensure no loop-like curves are obtained in the fitting results. The new model is successfully applied to investigate hydrogen absorption on metal powders. Our results indicate that the model works very well and can be used to predict PCT curves at different temperatures. Hence, our new model exhibits significant potential for application in practical systems.
2017, 33(6): 1114-1122
doi: 10.3866/PKU.WHXB201702213
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The SRC-100 type solution-reaction calorimeter was improved to a more precise and versatile isoperibol combustion-solution-reaction microcalorimeter. The energy equivalent of the calorimeter was calibrated to be Ccalor=（987.63±0.61）J·K-1 by the electric calibration method. The standard massic energy of combustion of benzoic acid and succinic acid were determined by the developed isoperibol combustion-solution-reaction microcalorimeter as △CUm,Bθ（cr,T=298.15K）=-（26425.99±10.70）J·g-1 and △CUm,Sθ（cr,T=298.15K）=-（12621.97±5.30）J·g-1, respec-tively. The uncertainty of the measurement was less than 0.04% and the accuracy was higher than 0.05%.
The SRC-100 type solution-reaction calorimeter was improved to a more precise and versatile isoperibol combustion-solution-reaction microcalorimeter. The energy equivalent of the calorimeter was calibrated to be Ccalor=（987.63±0.61）J·K-1 by the electric calibration method. The standard massic energy of combustion of benzoic acid and succinic acid were determined by the developed isoperibol combustion-solution-reaction microcalorimeter as △CUm,Bθ（cr,T=298.15K）=-（26425.99±10.70）J·g-1 and △CUm,Sθ（cr,T=298.15K）=-（12621.97±5.30）J·g-1, respec-tively. The uncertainty of the measurement was less than 0.04% and the accuracy was higher than 0.05%.
2017, 33(6): 1123-1129
doi: 10.3866/PKU.WHXB201703301
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Bimetallic Fe-Co, Fe-Ni, Mo-Co, and Mo-Ni catalysts, with total metal contents of 10 wt% and bimetallic molar ratios of 1:1, were prepared by the incipient wetness impregnation method and their activities for ammonia decomposition in the presence of plasma were studied. The Fe-Ni bimetallic catalyst exhibited a better synergistic effect than the other three bimetallic catalysts. The effect of the Fe/Ni molar ratio on its catalytic activity was also investigated. A 6:4 Fe/Ni molar ratio resulted in the highest ammonia decomposition activity and stability. The catalysts were characterized by N2 adsorption-desorption, XRD, H2-TPR, and HRTEM. The characterization results indicated that NiFe2O4 with a spinel structure was formed in the optimal Fe-Ni bimetallic catalysts and this structure favors the reduction of Fe and Ni. In other words, it is easy to achieve the metallic state of active components for the Fe-Ni bimetallic catalysts, which could be the reason for the high catalytic activity of bimetallic catalysts for NH3 decomposition.
Bimetallic Fe-Co, Fe-Ni, Mo-Co, and Mo-Ni catalysts, with total metal contents of 10 wt% and bimetallic molar ratios of 1:1, were prepared by the incipient wetness impregnation method and their activities for ammonia decomposition in the presence of plasma were studied. The Fe-Ni bimetallic catalyst exhibited a better synergistic effect than the other three bimetallic catalysts. The effect of the Fe/Ni molar ratio on its catalytic activity was also investigated. A 6:4 Fe/Ni molar ratio resulted in the highest ammonia decomposition activity and stability. The catalysts were characterized by N2 adsorption-desorption, XRD, H2-TPR, and HRTEM. The characterization results indicated that NiFe2O4 with a spinel structure was formed in the optimal Fe-Ni bimetallic catalysts and this structure favors the reduction of Fe and Ni. In other words, it is easy to achieve the metallic state of active components for the Fe-Ni bimetallic catalysts, which could be the reason for the high catalytic activity of bimetallic catalysts for NH3 decomposition.
2017, 33(6): 1130-1139
doi: 10.3866/PKU.WHXB201703221
Abstract:
Configuration interaction calculation in complete active space is related to the numbers of active electrons and orbitals. However, configuration interaction energy is not a monotonically decreasing function of these two variables. Thus, the numbers of active electrons and orbitals are not proper variables to extrapolate the configuration interaction energy. In order to address this problem, we defined a new variable:maximum number of unoccupied orbitals in the complete active space. We performed a series of configuration interaction calculations on singlet, doublet, and triplet molecules, and simulated their ground state energies with the number of active electrons and the number of maximum unoccupied orbitals. The mean square root errors of these simulations were on the order of 10-6. The accuracy of the extrapolated energies was better than that of MP4 and than that of CCSD for small molecules. The extrapolated full configuration interaction energies were very close to the energy values of full configuration interactions. Furthermore, the extrapolated energies were exploited to optimize the bond distances of several diatomic molecules and to compute harmonic vibrational frequencies. Their accuracies were better than that of the complete active space self-consistent field.
Configuration interaction calculation in complete active space is related to the numbers of active electrons and orbitals. However, configuration interaction energy is not a monotonically decreasing function of these two variables. Thus, the numbers of active electrons and orbitals are not proper variables to extrapolate the configuration interaction energy. In order to address this problem, we defined a new variable:maximum number of unoccupied orbitals in the complete active space. We performed a series of configuration interaction calculations on singlet, doublet, and triplet molecules, and simulated their ground state energies with the number of active electrons and the number of maximum unoccupied orbitals. The mean square root errors of these simulations were on the order of 10-6. The accuracy of the extrapolated energies was better than that of MP4 and than that of CCSD for small molecules. The extrapolated full configuration interaction energies were very close to the energy values of full configuration interactions. Furthermore, the extrapolated energies were exploited to optimize the bond distances of several diatomic molecules and to compute harmonic vibrational frequencies. Their accuracies were better than that of the complete active space self-consistent field.
2017, 33(6): 1140-1148
doi: 10.3866/PKU.WHXB201702242
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In an attempt to explain the co-solvent effect on the shape of β-HMX crystals, molecular dynamics simulations were applied to systematically investigate the interactions of β-HMX crystal faces and the co-solvents (acetone/γ-butyrolactone, dimethylformamide/H2O) by varying the volume ratio from 1:3 to 3:1. The growth habit of β-HMX in co-solvent was predicted using the modified attachment energy model. The results indicated that the (020) face of the β-HMX crystal has the weakest interaction with solvent molecule, and the binary solvent effects on different crystal faces varied such that the crystal morphology was affected significantly. The comparison of the β-HMX crystal aspect ratios grown from co-solvents with different volume ratios revealed that dimethylformamide/H2O with volume ratio of 1:3 favors the spheroidization of β-HMX.
In an attempt to explain the co-solvent effect on the shape of β-HMX crystals, molecular dynamics simulations were applied to systematically investigate the interactions of β-HMX crystal faces and the co-solvents (acetone/γ-butyrolactone, dimethylformamide/H2O) by varying the volume ratio from 1:3 to 3:1. The growth habit of β-HMX in co-solvent was predicted using the modified attachment energy model. The results indicated that the (020) face of the β-HMX crystal has the weakest interaction with solvent molecule, and the binary solvent effects on different crystal faces varied such that the crystal morphology was affected significantly. The comparison of the β-HMX crystal aspect ratios grown from co-solvents with different volume ratios revealed that dimethylformamide/H2O with volume ratio of 1:3 favors the spheroidization of β-HMX.
2017, 33(6): 1149-1159
doi: 10.3866/PKU.WHXB201703291
Abstract:
A novel DFT-D method, B972-PFD, has been found by combining the B972 hybrid density functional with the empirical dispersion correction based on the spherical atom model (SAM). The performance of the B972-PFD method is assessed on the S66, S66x8, and S22 standard data sets, atmospheric hydrogen-bonded clusters, the Adenine-Thymine π…π stacked, Watson-Crick hydrogen-bonded complexes, and the methane to (H2O)20 water cluster. The benchmark results of the S66 test set show that B972-PFD and three recently developed density functionals, ωB97X-V, B97M-V, and ωB97M-V developed by the Head-Gordon group, are at the same level of accuracy, and have an root-mean-square deviation (RMSD) of binding energies less than 1 kJ·mol-1 relative to the CCSD(T)/CBS gold standard. The B972-PFD method also showed excellent accuracy in other data set tests. The basis set effect of the B972-PFD method has been benchmarked, and we recommend that the favorable price/performance ratios basis set is Pople's 6-311++G(2d,p).
A novel DFT-D method, B972-PFD, has been found by combining the B972 hybrid density functional with the empirical dispersion correction based on the spherical atom model (SAM). The performance of the B972-PFD method is assessed on the S66, S66x8, and S22 standard data sets, atmospheric hydrogen-bonded clusters, the Adenine-Thymine π…π stacked, Watson-Crick hydrogen-bonded complexes, and the methane to (H2O)20 water cluster. The benchmark results of the S66 test set show that B972-PFD and three recently developed density functionals, ωB97X-V, B97M-V, and ωB97M-V developed by the Head-Gordon group, are at the same level of accuracy, and have an root-mean-square deviation (RMSD) of binding energies less than 1 kJ·mol-1 relative to the CCSD(T)/CBS gold standard. The B972-PFD method also showed excellent accuracy in other data set tests. The basis set effect of the B972-PFD method has been benchmarked, and we recommend that the favorable price/performance ratios basis set is Pople's 6-311++G(2d,p).
2017, 33(6): 1160-1170
doi: 10.3866/PKU.WHXB201704051
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The purpose of this study was to develop a quantitative structure-property relationship (QSPR) model based on the enhanced replacement method (ERM) and support vector machine (SVM) to predict the blood-to-brain barrier partitioning behavior (logBB) of various drugs and organic compounds. Different molecular descriptors were calculated using a dragon package to represent the molecular structures of the compounds studied. The enhanced replacement method (ERM) was used to select the variables and construct the SVM model. The correlation coefficient, R2, between experimental results and predicted logBB was 0.878 and 0.986, respectively. The results obtained demonstrated that, for all compounds, the logBB values estimated by SVM agreed with the experimental data, demonstrating that SVM is an effective method for model development, and can be used as a powerful chemometric tool in QSPR studies.
The purpose of this study was to develop a quantitative structure-property relationship (QSPR) model based on the enhanced replacement method (ERM) and support vector machine (SVM) to predict the blood-to-brain barrier partitioning behavior (logBB) of various drugs and organic compounds. Different molecular descriptors were calculated using a dragon package to represent the molecular structures of the compounds studied. The enhanced replacement method (ERM) was used to select the variables and construct the SVM model. The correlation coefficient, R2, between experimental results and predicted logBB was 0.878 and 0.986, respectively. The results obtained demonstrated that, for all compounds, the logBB values estimated by SVM agreed with the experimental data, demonstrating that SVM is an effective method for model development, and can be used as a powerful chemometric tool in QSPR studies.
2017, 33(6): 1171-1180
doi: 10.3866/PKU.WHXB201704071
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Accurate prediction of the energy levels (i.e. ionization potential and electronic affinity) of organic semiconductors is essential for understanding related mechanisms and for designing novel organic semiconductor materials. From a theoretical point of view, a major challenge arises from the lack of a reliable method that can provide not only qualitative but also quantitative predictions at an acceptable computational cost. In this study, we demonstrate an approach, combining the polarizable continuum model (PCM) and the optimally tuned range-separated (RS) functional method, which provides the ionization potentials (IPs), electron affinities (EAs), and polarization energies of a series of molecular semiconductors in good agreement with available experimental values. Importantly, this tuning method can enforce the negative frontier molecular orbital energies (-εHOMO, -εLUMO) that are very close to the corresponding IPs and EAs. The success of this tuning method can be further attributed to the fact that the tuned RS functional can provide a good balance for the description of electronic localization and delocalization effects according to various molecular systems or the same molecule in different phases (i.e. gas and solid). In comparison, other conventional functionals cannot give reliable predictions because the functionals themselves include too low (i.e. PBE) or too high (i.e. M06HF and non-tuned RS functionals) HF%. Therefore, we believe that this PCM-tuned approach represents an easily applicable and computationally efficient theoretical tool to study the energy levels of more complex organic electronic materials.
Accurate prediction of the energy levels (i.e. ionization potential and electronic affinity) of organic semiconductors is essential for understanding related mechanisms and for designing novel organic semiconductor materials. From a theoretical point of view, a major challenge arises from the lack of a reliable method that can provide not only qualitative but also quantitative predictions at an acceptable computational cost. In this study, we demonstrate an approach, combining the polarizable continuum model (PCM) and the optimally tuned range-separated (RS) functional method, which provides the ionization potentials (IPs), electron affinities (EAs), and polarization energies of a series of molecular semiconductors in good agreement with available experimental values. Importantly, this tuning method can enforce the negative frontier molecular orbital energies (-εHOMO, -εLUMO) that are very close to the corresponding IPs and EAs. The success of this tuning method can be further attributed to the fact that the tuned RS functional can provide a good balance for the description of electronic localization and delocalization effects according to various molecular systems or the same molecule in different phases (i.e. gas and solid). In comparison, other conventional functionals cannot give reliable predictions because the functionals themselves include too low (i.e. PBE) or too high (i.e. M06HF and non-tuned RS functionals) HF%. Therefore, we believe that this PCM-tuned approach represents an easily applicable and computationally efficient theoretical tool to study the energy levels of more complex organic electronic materials.
2017, 33(6): 1181-1188
doi: 10.3866/PKU.WHXB201703151
Abstract:
Titanium nitride nanowires (TiN NWs) were directly prepared on a Ti foil by a hydrothermal method followed by nitridation in ammonia atmosphere. The composition, microstructure, and electrochemical properties of the TiN NWs were characterized using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry(CV), and electrochemical impedance spectroscopy (EIS). The results show that the nanowires have diameters of 20-50 nm and are 5 μm long. The surfaces of the TiN NWs comprise Ti-N, Ti-O, and O-Ti-N chemical states. The electrochemical activity and reversibility for the electrode processes of V(II)/V(III) couple on the TiN NWs are significantly improved due to the introduced Ti-N, Ti-O, and O-Ti-N chemical states. The transfer resistance for the cathodic reduction of V(III) on the TiN NWs is about 20 times and 10 times smaller than on TiO2 NWs and graphite electrodes, respectively. The rate constant of charge transfer on the TiN NWs electrode was determined to be 5.21×10-4 cm·s-1, which is about 5 times larger than the rate constant on graphite electrodes (9.63×10-5 cm·s-1).
Titanium nitride nanowires (TiN NWs) were directly prepared on a Ti foil by a hydrothermal method followed by nitridation in ammonia atmosphere. The composition, microstructure, and electrochemical properties of the TiN NWs were characterized using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry(CV), and electrochemical impedance spectroscopy (EIS). The results show that the nanowires have diameters of 20-50 nm and are 5 μm long. The surfaces of the TiN NWs comprise Ti-N, Ti-O, and O-Ti-N chemical states. The electrochemical activity and reversibility for the electrode processes of V(II)/V(III) couple on the TiN NWs are significantly improved due to the introduced Ti-N, Ti-O, and O-Ti-N chemical states. The transfer resistance for the cathodic reduction of V(III) on the TiN NWs is about 20 times and 10 times smaller than on TiO2 NWs and graphite electrodes, respectively. The rate constant of charge transfer on the TiN NWs electrode was determined to be 5.21×10-4 cm·s-1, which is about 5 times larger than the rate constant on graphite electrodes (9.63×10-5 cm·s-1).
2017, 33(6): 1189-1196
doi: 10.3866/PKU.WHXB201702221
Abstract:
In this work, a series of Li-rich layered metal oxides (LLMO) as cathode materials for lithium ion batteries were prepared by the coprecipitation method. Various surfactants were introduced into the preparation of Al2O3-modified LLMO. The roles of surfactants were systematically investigated to reveal the mechanism of Al2O3 modification. The microstructure, morphology and electrochemical performance of the as-prepared samples were studied by the X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), galvanostatic discharge/charge measurement, cycling stability, rate capability and electrochemical impedance spectroscopies. The experimental results showed that Al2O3 nanoparticles were uniformly dispersed on the surface of LLMO by using N,N,N-trimethyl-1-dodecanaminium bromide (DTAB) as the surfactant. Al2O3-modified LLMO used DTAB as surfactant delivered the initial discharge capacity of 186 mAh·g-1 at the current density of 600 mA·g-1. After 500 cycles, the reversible discharge capacity was 132 mAh·g-1 with a satisfactory capacity retention of 71%. Moreover, the voltage fade of LLMO was greatly suppressed after Al2O3 modification, which exhibited superior electrochemical performances.
In this work, a series of Li-rich layered metal oxides (LLMO) as cathode materials for lithium ion batteries were prepared by the coprecipitation method. Various surfactants were introduced into the preparation of Al2O3-modified LLMO. The roles of surfactants were systematically investigated to reveal the mechanism of Al2O3 modification. The microstructure, morphology and electrochemical performance of the as-prepared samples were studied by the X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), galvanostatic discharge/charge measurement, cycling stability, rate capability and electrochemical impedance spectroscopies. The experimental results showed that Al2O3 nanoparticles were uniformly dispersed on the surface of LLMO by using N,N,N-trimethyl-1-dodecanaminium bromide (DTAB) as the surfactant. Al2O3-modified LLMO used DTAB as surfactant delivered the initial discharge capacity of 186 mAh·g-1 at the current density of 600 mA·g-1. After 500 cycles, the reversible discharge capacity was 132 mAh·g-1 with a satisfactory capacity retention of 71%. Moreover, the voltage fade of LLMO was greatly suppressed after Al2O3 modification, which exhibited superior electrochemical performances.
2017, 33(6): 1197-1204
doi: 10.3866/PKU.WHXB201703293
Abstract:
Multi-walled carbon nanotube constrained SnS2 (SnS2@MWCNT) nanostructure is successfully realized through a facile 2-step process. Firstly, DC arc-discharge method is applied to fabricate Sn@MWCNT nanoparticles as the precursor that is subsequently converted into SnS2@MWCNT through low-temperature vulcanization. Various analytical methods, including powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy, are used to ascertain the microstructure and morphology of the SnS2@MWCNT nanoparticles. The results show that the SnS2@MWCNT nanoparticles have a uniform structure of SnS2 half-filled MWCNTs with average thickness of 10 nm and average length of ~400 nm. The electrochemical properties of the as-prepared SnS2@MWCNT nanoparticles are studied using the nanoparticles as anode materials in Li-ion batteries. The SnS2@MWCNT electrode presents high initial Coulombic efficiency of 71% and maintains a capacity of 703 mAh·g-1 after 50 cycles. Excellent performance of the batteries benefits from the active electrochemical reactions of various chemical components, multi-step lithiation/delithiation behaviors, and the structural constraint from the MWCNTs.
Multi-walled carbon nanotube constrained SnS2 (SnS2@MWCNT) nanostructure is successfully realized through a facile 2-step process. Firstly, DC arc-discharge method is applied to fabricate Sn@MWCNT nanoparticles as the precursor that is subsequently converted into SnS2@MWCNT through low-temperature vulcanization. Various analytical methods, including powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy, are used to ascertain the microstructure and morphology of the SnS2@MWCNT nanoparticles. The results show that the SnS2@MWCNT nanoparticles have a uniform structure of SnS2 half-filled MWCNTs with average thickness of 10 nm and average length of ~400 nm. The electrochemical properties of the as-prepared SnS2@MWCNT nanoparticles are studied using the nanoparticles as anode materials in Li-ion batteries. The SnS2@MWCNT electrode presents high initial Coulombic efficiency of 71% and maintains a capacity of 703 mAh·g-1 after 50 cycles. Excellent performance of the batteries benefits from the active electrochemical reactions of various chemical components, multi-step lithiation/delithiation behaviors, and the structural constraint from the MWCNTs.
2017, 33(6): 1205-1213
doi: 10.3866/PKU.WHXB201702222
Abstract:
Because of good biocompatibility using Se atom as the redox-responsive group has aroused considerable attention. However, only a few efforts have been devoted to Se-containing surfactant, especially for smart control of interfacial properties. This paper focuses on the redox-responsive behaviors of molecular structure, Krafft temperature, Surface/interfacial tension, foaming and emulsification of Se-containing zwitterionic surfactant, benzylselanyl-undecyl-dimethyl ammonium propane sulfonate (BSeUSB). The results show that after oxidization with a trace of H2O2 (≤0.056% of total mass), reduced form BSeUSB with one hydrophilic head and one hydrophobic tail transformed to Bola-type oxidized form BSeUSB-Ox due to the presence of a new hydrophilic group (selenoxide). And thus Krafft temperature decreased from (23.5±0.5)℃ to less than 0℃. The surface/interfacial tension at 5.00 mmol·L-1 increased from 45.15, 5.52 mN·m-1 to 61.63, 18.38 mN·m-1, respectively. Macroscopically, reduced form BSeUSB has good foaming and emulsification properties, while the foaming and emulsification abilities of oxidized form BSeUSB-Ox almost disappeared. Interestingly the molecular structure and the solution properties re-turned the initial states after reduction with a trace of Na2SO3 (≤0.060% of total mass). In a word, by the addition trace amounts of H2O2 and Na2SO3 alternately, we have achieved the smart control of the interfacial properties of the surfactant.
Because of good biocompatibility using Se atom as the redox-responsive group has aroused considerable attention. However, only a few efforts have been devoted to Se-containing surfactant, especially for smart control of interfacial properties. This paper focuses on the redox-responsive behaviors of molecular structure, Krafft temperature, Surface/interfacial tension, foaming and emulsification of Se-containing zwitterionic surfactant, benzylselanyl-undecyl-dimethyl ammonium propane sulfonate (BSeUSB). The results show that after oxidization with a trace of H2O2 (≤0.056% of total mass), reduced form BSeUSB with one hydrophilic head and one hydrophobic tail transformed to Bola-type oxidized form BSeUSB-Ox due to the presence of a new hydrophilic group (selenoxide). And thus Krafft temperature decreased from (23.5±0.5)℃ to less than 0℃. The surface/interfacial tension at 5.00 mmol·L-1 increased from 45.15, 5.52 mN·m-1 to 61.63, 18.38 mN·m-1, respectively. Macroscopically, reduced form BSeUSB has good foaming and emulsification properties, while the foaming and emulsification abilities of oxidized form BSeUSB-Ox almost disappeared. Interestingly the molecular structure and the solution properties re-turned the initial states after reduction with a trace of Na2SO3 (≤0.060% of total mass). In a word, by the addition trace amounts of H2O2 and Na2SO3 alternately, we have achieved the smart control of the interfacial properties of the surfactant.
2017, 33(6): 1214-1222
doi: 10.3866/PKU.WHXB201704075
Abstract:
The aggregation behavior of the double-chained anionic surfactant 1-alkyl-decyl sodium sulfonate (1-Cm-C9-SO3-Na) at the air/liquid interface was investigated using molecular dynamics simulation. The influences of the m value on the interfacial properties of the surfactant were compared using density profile and radial distribution function (RDF). The results showed that the hydrophobic ability of the surfactant increase and the slant angles of hydrophobic carbon chains decrease with increasing m. For m=4, the 1-C4-C9-SO3Na form aggregates by lying on the interface; the S-S and S-Na+ interactions are the highest for m=4 among all systems studied, while the hydration ability of its polar head is the weakest. The simulation and experimental results show that the interfacial performance is the best for 1-C4-C9-SO3Na.
The aggregation behavior of the double-chained anionic surfactant 1-alkyl-decyl sodium sulfonate (1-Cm-C9-SO3-Na) at the air/liquid interface was investigated using molecular dynamics simulation. The influences of the m value on the interfacial properties of the surfactant were compared using density profile and radial distribution function (RDF). The results showed that the hydrophobic ability of the surfactant increase and the slant angles of hydrophobic carbon chains decrease with increasing m. For m=4, the 1-C4-C9-SO3Na form aggregates by lying on the interface; the S-S and S-Na+ interactions are the highest for m=4 among all systems studied, while the hydration ability of its polar head is the weakest. The simulation and experimental results show that the interfacial performance is the best for 1-C4-C9-SO3Na.
2017, 33(6): 1223-1229
doi: 10.3866/PKU.WHXB201702282
Abstract:
Nanoporous gold films (NPGFs) are chemically robust and thermally stable, possessing large specific area and salient surface plasmon resonance (SPR) effect. With these features NPGFs are quite applicable for high-sensitivity SPR sensors. In this work, the SPR effect of NPGFs was theoretically analyzed and the dispersion relation of propagating surface plasmons at the NPGF/air interface was obtained. The optimal thickness of NPGF required for optimizing its SPR sensing performance was achieved to be about 60 nm. Large-area, uniform and ultrathin NPGFs were prepared by a two-step approach consisting of sputtering deposition and chemical dealloying. The SPR resonance band in the visible-near-infrared region and the sensing properties of NPGF were measured with the Kretschmann prism-coupling configuration. Porosity of the NPGF is determined to be about 0.38 by fitting the measured resonance wavelengths based on the combination of the Fresnel formula and the Bruggeman dielectric constant approximation theory. Since the non-modified NPGFs are hydrophilic and enable effective enrichment of bisphenol A (BPA) molecules in water, the NPGF-SPR sensor can easily detect BPA with concentrations as low as 5 nmol·L-1. After hydrophobilization of NPGFs, the sensor enables detection of trace benzo[a]pyrene (BaP) in water, with the detection limit of 1 nmol·L-1.
Nanoporous gold films (NPGFs) are chemically robust and thermally stable, possessing large specific area and salient surface plasmon resonance (SPR) effect. With these features NPGFs are quite applicable for high-sensitivity SPR sensors. In this work, the SPR effect of NPGFs was theoretically analyzed and the dispersion relation of propagating surface plasmons at the NPGF/air interface was obtained. The optimal thickness of NPGF required for optimizing its SPR sensing performance was achieved to be about 60 nm. Large-area, uniform and ultrathin NPGFs were prepared by a two-step approach consisting of sputtering deposition and chemical dealloying. The SPR resonance band in the visible-near-infrared region and the sensing properties of NPGF were measured with the Kretschmann prism-coupling configuration. Porosity of the NPGF is determined to be about 0.38 by fitting the measured resonance wavelengths based on the combination of the Fresnel formula and the Bruggeman dielectric constant approximation theory. Since the non-modified NPGFs are hydrophilic and enable effective enrichment of bisphenol A (BPA) molecules in water, the NPGF-SPR sensor can easily detect BPA with concentrations as low as 5 nmol·L-1. After hydrophobilization of NPGFs, the sensor enables detection of trace benzo[a]pyrene (BaP) in water, with the detection limit of 1 nmol·L-1.
2017, 33(6): 1230-1235
doi: 10.3866/PKU.WHXB201703311
Abstract:
A composite hydrogel consisting of well-dispersed Pt-Cu nanoparticles (NPs) supported on three-dimensional (3D) graphene (Pt-Cu@3DG) was successfully prepared by mild chemical reduction. The 3D interconnected macroporous structure of the graphene framework not only possesses large specific surface area that allows high metal loadings, but also facilitates mass transfer during the catalytic reaction. The Pt-Cu bimetallic alloy NPs show good catalytic activity compared with Pt NPs and reduce the content of Pt NPs used, thereby lowering costs. The morphology and composition of the Pt-Cu@3DG composite were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX). The catalysis studies indicate that the resulting composites can be used as an efficient, inexpensive, recyclable, and stable catalyst for the reduction of 4-nitrophenol to 4-aminophenol under mild conditions.
A composite hydrogel consisting of well-dispersed Pt-Cu nanoparticles (NPs) supported on three-dimensional (3D) graphene (Pt-Cu@3DG) was successfully prepared by mild chemical reduction. The 3D interconnected macroporous structure of the graphene framework not only possesses large specific surface area that allows high metal loadings, but also facilitates mass transfer during the catalytic reaction. The Pt-Cu bimetallic alloy NPs show good catalytic activity compared with Pt NPs and reduce the content of Pt NPs used, thereby lowering costs. The morphology and composition of the Pt-Cu@3DG composite were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX). The catalysis studies indicate that the resulting composites can be used as an efficient, inexpensive, recyclable, and stable catalyst for the reduction of 4-nitrophenol to 4-aminophenol under mild conditions.
2017, 33(6): 1236-1241
doi: 10.3866/PKU.WHXB201703281
Abstract:
A CuY zeolite prepared by liquid phase ion exchange was characterized by X-ray photoelectron spectroscopy, pyridine in situ Fourier transform infrared (in situ FTIR) spectroscopy, and ammonia temperature programmed desorption. The effect of cyclohexene on the adsorption of thiophene over the prepared CuY zeolite was explored by in situ FTIR. In particular, the role of the zeolite's Brönsted acidity was investigated in the adsorption process. The results show that the percentage of Cu+ on the surface of the CuY zeolite can reach 77%. The surface acidity of the CuY zeolite mainly comprises medium and strong Brönsted acidity and Lewis acidity. According to the adsorption results, cyclohexene negatively influences thiophene adsorption on the Brönsted or Lewis acid sites in CuY by competitive adsorption. Although polymerization of thiophene and cyclohexene can occur easily on the HY or REY zeolites, the presence of Brönsted acids in the CuY zeolite was not sufficient to polymerize either thiophene or cyclohexene. This difference may be caused by an anti-synergistic effect between the Cu ions of the CuY zeolite and neighboring Brönsted acid sites, the result of which inhibits the polymerization of adsorbed thiophene and cyclohexene.
A CuY zeolite prepared by liquid phase ion exchange was characterized by X-ray photoelectron spectroscopy, pyridine in situ Fourier transform infrared (in situ FTIR) spectroscopy, and ammonia temperature programmed desorption. The effect of cyclohexene on the adsorption of thiophene over the prepared CuY zeolite was explored by in situ FTIR. In particular, the role of the zeolite's Brönsted acidity was investigated in the adsorption process. The results show that the percentage of Cu+ on the surface of the CuY zeolite can reach 77%. The surface acidity of the CuY zeolite mainly comprises medium and strong Brönsted acidity and Lewis acidity. According to the adsorption results, cyclohexene negatively influences thiophene adsorption on the Brönsted or Lewis acid sites in CuY by competitive adsorption. Although polymerization of thiophene and cyclohexene can occur easily on the HY or REY zeolites, the presence of Brönsted acids in the CuY zeolite was not sufficient to polymerize either thiophene or cyclohexene. This difference may be caused by an anti-synergistic effect between the Cu ions of the CuY zeolite and neighboring Brönsted acid sites, the result of which inhibits the polymerization of adsorbed thiophene and cyclohexene.
2017, 33(6): 1242-1252
doi: 10.3866/PKU.WHXB201703292
Abstract:
The catalytic activities for NO oxidation achieved by different amounts of CeO2-modified Pt/SiO2-Al2O3 catalysts Pt/SiO2-Al2O3-wCeO2 (the mass fraction w being 0%, 5%, 10%, 15%, 30%), prepared using step-wise impregnation, were investigated in the presence and absence of CO and C3H6. The results showed that the NO oxidation activity could be efficiently improved by modification of CeO2, wherein the 15%-CeO2-modified catalyst exhibited the maximum NO conversion of 61% even in the presence of CO and C3H6, which were proved to inhibit NO2 formation in this study. A series of characterization methods were performed over the as-prepared samples to correlate their surface and structural characteristics with their enhanced NO oxidation activities. CO-chemisorption illustrated that appropriate CeO2-loading was effective for enhancing Pt dispersion, thus enhancing Pt surface-to-volume ratio, confirmed by transmission electron microscope (TEM) images. X-Ray Diffraction (XRD) further suggested that ceria addition could suppress the growth of the Pt crystal, resulting in higher surface Pt atomic ratio. Further, H2 temperature-programmed reduction (H2-TPR), together with TEM results, implied that the presence of ceria could enhance the interaction between metal and supports, thus facilitating reducibility of both active platinum and ceria. Hence, this study displays that ceria could act as a dispersion promoter and a reducibility booster, both of which are beneficial to NO oxidation activity. The improved NO oxidation activity is significant for the efficient purification of diesel integrated catalytic system.
The catalytic activities for NO oxidation achieved by different amounts of CeO2-modified Pt/SiO2-Al2O3 catalysts Pt/SiO2-Al2O3-wCeO2 (the mass fraction w being 0%, 5%, 10%, 15%, 30%), prepared using step-wise impregnation, were investigated in the presence and absence of CO and C3H6. The results showed that the NO oxidation activity could be efficiently improved by modification of CeO2, wherein the 15%-CeO2-modified catalyst exhibited the maximum NO conversion of 61% even in the presence of CO and C3H6, which were proved to inhibit NO2 formation in this study. A series of characterization methods were performed over the as-prepared samples to correlate their surface and structural characteristics with their enhanced NO oxidation activities. CO-chemisorption illustrated that appropriate CeO2-loading was effective for enhancing Pt dispersion, thus enhancing Pt surface-to-volume ratio, confirmed by transmission electron microscope (TEM) images. X-Ray Diffraction (XRD) further suggested that ceria addition could suppress the growth of the Pt crystal, resulting in higher surface Pt atomic ratio. Further, H2 temperature-programmed reduction (H2-TPR), together with TEM results, implied that the presence of ceria could enhance the interaction between metal and supports, thus facilitating reducibility of both active platinum and ceria. Hence, this study displays that ceria could act as a dispersion promoter and a reducibility booster, both of which are beneficial to NO oxidation activity. The improved NO oxidation activity is significant for the efficient purification of diesel integrated catalytic system.
2017, 33(6): 1253-1260
doi: 10.3866/PKU.WHXB201702212
Abstract:
Siloles constitute an important emerging class of photoluminescent materials. A series of compounds consisting of silole cores and fused naphthalene were synthesized and characterized:6,6-dimethyl-1,2,3,4,8,9,10,11-octapropyl-6H-dinaphtho[2,3-b:2',3'-d]silole, 1,2,3,4,8,9,10,11-octabutyl-6,6-dimethyl-6H-dinaphtho[2,3-b:2',3'-d]silole, 6,6-diphenyl-1,2,3,4,8,9,10,11-octapropyl-6H-dinaphtho[2,3-b:2',3'-d]silole, and 1,2,3,4,8,9,10,11-octabutyl-6,6-diphenyl-6H-dinaphtho[2,3-b:2',3'-d]silole. These dinaphthalene-fused siloles were synthesized from diiodonaphthalene, which was prepared by a direct coupling method. Subsequent reaction in the presence of n-butyllithium yielded 3,3'-diiodo-2,2'-binaphthalene. Direct substitution of two chloride ions from Ph2SiCl2 or Me2SiCl2 with 3,3'-dilithio-2,2'-binaphthalene then yielded the multi-substituted silole. Nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry were used to characterize the structures of the siloles. Their optical and electronic properties were investigated using ultraviolet-visible absorption spectroscopy, photoluminescence spectroscopy, cyclic voltammetry, and density functional theory calculations. The dinaphthalene-fused siloles exhibited similar absorption and emission peaks. Their deep highest occupied molecular orbital level at approximately -5.5 eV indicated that they were chemically stable. Differential scanning calorimetry and thermogravimetric analysis indicated that the siloles were stable up to 309℃. A multilayer electroluminescent device was fabricated using 1,2,3,4,8,9,10,11-octabutyl-6,6-dimethyl-6H-dinaphtho[2,3-b:2',3'-d]silole as a light-emitting layer. The resulting device produced bright blue emission, indicating that these siloles may be suitable materials in organic light-emitting devices.
Siloles constitute an important emerging class of photoluminescent materials. A series of compounds consisting of silole cores and fused naphthalene were synthesized and characterized:6,6-dimethyl-1,2,3,4,8,9,10,11-octapropyl-6H-dinaphtho[2,3-b:2',3'-d]silole, 1,2,3,4,8,9,10,11-octabutyl-6,6-dimethyl-6H-dinaphtho[2,3-b:2',3'-d]silole, 6,6-diphenyl-1,2,3,4,8,9,10,11-octapropyl-6H-dinaphtho[2,3-b:2',3'-d]silole, and 1,2,3,4,8,9,10,11-octabutyl-6,6-diphenyl-6H-dinaphtho[2,3-b:2',3'-d]silole. These dinaphthalene-fused siloles were synthesized from diiodonaphthalene, which was prepared by a direct coupling method. Subsequent reaction in the presence of n-butyllithium yielded 3,3'-diiodo-2,2'-binaphthalene. Direct substitution of two chloride ions from Ph2SiCl2 or Me2SiCl2 with 3,3'-dilithio-2,2'-binaphthalene then yielded the multi-substituted silole. Nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry were used to characterize the structures of the siloles. Their optical and electronic properties were investigated using ultraviolet-visible absorption spectroscopy, photoluminescence spectroscopy, cyclic voltammetry, and density functional theory calculations. The dinaphthalene-fused siloles exhibited similar absorption and emission peaks. Their deep highest occupied molecular orbital level at approximately -5.5 eV indicated that they were chemically stable. Differential scanning calorimetry and thermogravimetric analysis indicated that the siloles were stable up to 309℃. A multilayer electroluminescent device was fabricated using 1,2,3,4,8,9,10,11-octabutyl-6,6-dimethyl-6H-dinaphtho[2,3-b:2',3'-d]silole as a light-emitting layer. The resulting device produced bright blue emission, indicating that these siloles may be suitable materials in organic light-emitting devices.
2017, 33(6): 1261-1266
doi: 10.3866/PKU.WHXB201702281
Abstract:
Ferroelectric polymers are particularly attractive for applications in flexible electronic devices, and controlling its crystalline phase growth is crucial for obtaining optimized ferroelectric properties. Herein we report that a very low introduction (0.2% (w)) of single-domain ferroelectric PbTiO3 nanoplates can effectively mediate the nucleation and subsequent growth of a crystalline phase within P(VDF-TrFE) (denoted by PVTF), forming highly oriented films and significantly improving the ferroelectric properties due to an alignment of the polarization directions of the polymer and the nanoplates.
Ferroelectric polymers are particularly attractive for applications in flexible electronic devices, and controlling its crystalline phase growth is crucial for obtaining optimized ferroelectric properties. Herein we report that a very low introduction (0.2% (w)) of single-domain ferroelectric PbTiO3 nanoplates can effectively mediate the nucleation and subsequent growth of a crystalline phase within P(VDF-TrFE) (denoted by PVTF), forming highly oriented films and significantly improving the ferroelectric properties due to an alignment of the polarization directions of the polymer and the nanoplates.
