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2016 Volume 32 Issue 9
2016, 32(9):
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2016, 32(9): 2125-2126
doi: 10.3866/PKU.WHXB201608081
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2016, 32(9): 2127-2128
doi: 10.3866/PKU.WHXB201608301
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2016, 32(9): 2129-2130
doi: 10.3866/PKU.WHXB201608082
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2016, 32(9): 2131-2132
doi: 10.3866/PKU.WHXB20160825
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2016, 32(9): 2133-2145
doi: 10.3866/PKU.WHXB201606162
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Semiconducting, two-dimensional (2D) transition metal dichalcogenides (TMDCs) such as molybdenum disulfide (MoS2) have attracted significant attention because of their unique properties and promising applications in electronic and optoelectronic devices. However, the controllable tuning of the properties of 2D MoS2 remains a key challenge with regard to its practical application. Among various approaches to addressing this issue, chemical doping is one of the most efficient. This review focuses on three major doping strategies, which are surface charge transfer, in-plane substitution and interlayer intercalation. We discuss the principles, latest progress and limitations of these doping approaches. Finally, we summarize the current challenges and opportunities associated with the chemical doping of 2D MoS2.
Semiconducting, two-dimensional (2D) transition metal dichalcogenides (TMDCs) such as molybdenum disulfide (MoS2) have attracted significant attention because of their unique properties and promising applications in electronic and optoelectronic devices. However, the controllable tuning of the properties of 2D MoS2 remains a key challenge with regard to its practical application. Among various approaches to addressing this issue, chemical doping is one of the most efficient. This review focuses on three major doping strategies, which are surface charge transfer, in-plane substitution and interlayer intercalation. We discuss the principles, latest progress and limitations of these doping approaches. Finally, we summarize the current challenges and opportunities associated with the chemical doping of 2D MoS2.
2016, 32(9): 2146-2158
doi: 10.3866/PKU.WHXB201605243
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Graphene aerogels are obtained from graphene sheets through wet chemical assembly or vaporphase chemical growth. They have a three dimensional graphene architecture that has an interconnected network with a high specific surface area, good electric conductivity and other physicochemical properties and thus has important applications in electrochemical energy storage, adsorption, catalysis and sensing. In this review, we will highlight the assembly strategies and structural designs used to introduce the controlled assembly of the graphene sheets in graphene aerogel materials, such as graphene oxide-, reduced graphene oxide-, CVDgrown graphene and composite graphene aerogels. The current challenges and future development of the grapheme aerogels are also discussed.
Graphene aerogels are obtained from graphene sheets through wet chemical assembly or vaporphase chemical growth. They have a three dimensional graphene architecture that has an interconnected network with a high specific surface area, good electric conductivity and other physicochemical properties and thus has important applications in electrochemical energy storage, adsorption, catalysis and sensing. In this review, we will highlight the assembly strategies and structural designs used to introduce the controlled assembly of the graphene sheets in graphene aerogel materials, such as graphene oxide-, reduced graphene oxide-, CVDgrown graphene and composite graphene aerogels. The current challenges and future development of the grapheme aerogels are also discussed.
2016, 32(9): 2159-2170
doi: 10.3866/PKU.WHXB201606072
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In recent years, significant breakthroughs have been achieved in the development of organicinorganic halide lead perovskite solar cells, with reported power conversion efficiency (PCE) values of up to 22.1%. This value is comparable to the efficiencies obtained using CdTe (22.1%) and CuInGaSn (CIGS) (22.3%) solar cells, and close to the value associated with crystalline silicon solar cells (approximately 25%). However, the limited long-term output efficiency stability and lead toxicity issues associated with organic-inorgan lead halide perovskite cells have limited their commercial applications. This review focuses on these issues and corresponding solutions for halide lead hybrid perovskite solar cells, and discusses advances and developments in Pb-free inorganic perovskite solar cells. We also examine the current body of knowledge regarding perovskite solar cells and discuss critical points and expectations regarding further performance improvements.
In recent years, significant breakthroughs have been achieved in the development of organicinorganic halide lead perovskite solar cells, with reported power conversion efficiency (PCE) values of up to 22.1%. This value is comparable to the efficiencies obtained using CdTe (22.1%) and CuInGaSn (CIGS) (22.3%) solar cells, and close to the value associated with crystalline silicon solar cells (approximately 25%). However, the limited long-term output efficiency stability and lead toxicity issues associated with organic-inorgan lead halide perovskite cells have limited their commercial applications. This review focuses on these issues and corresponding solutions for halide lead hybrid perovskite solar cells, and discusses advances and developments in Pb-free inorganic perovskite solar cells. We also examine the current body of knowledge regarding perovskite solar cells and discuss critical points and expectations regarding further performance improvements.
2016, 32(9): 2171-2184
doi: 10.3866/PKU.WHXB201606131
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The properties of Pd nanocrystals (NCs) intended for use in electrocatalytic applications greatly depend on their surface structures and morphologies. Recent developments in the shape-controlled synthesis of polyhedral Pd NCs represent a promising means of precisely tuning their electrocatalytic properties, and thus may enable the performance enhancement of electrocatalytic Pd NCs. In this comprehensive review, we concentrate on the most important current research concerning the shape-controlled synthesis of polyhedral Pd NCs and their electrocatalytic applications in fuel cells. After a brief introduction to the general NC growth mechanisms and the relationship between their surface structures and shapes, we focus on a variety of shapecontrolled synthesis strategies that have been explored to control the fabrication of polyhedral Pd NCs. This review also examines the applications of Pd NCs to the electrocatalytic oxidation of formic acid, methanol, and ethanol as well as the reduction of O2, with an emphasis on their use in fuel cells. Finally, we outline our personal perspectives on future research directions that are underway with regard to catalytic uses of polyhedral Pd NCs.
The properties of Pd nanocrystals (NCs) intended for use in electrocatalytic applications greatly depend on their surface structures and morphologies. Recent developments in the shape-controlled synthesis of polyhedral Pd NCs represent a promising means of precisely tuning their electrocatalytic properties, and thus may enable the performance enhancement of electrocatalytic Pd NCs. In this comprehensive review, we concentrate on the most important current research concerning the shape-controlled synthesis of polyhedral Pd NCs and their electrocatalytic applications in fuel cells. After a brief introduction to the general NC growth mechanisms and the relationship between their surface structures and shapes, we focus on a variety of shapecontrolled synthesis strategies that have been explored to control the fabrication of polyhedral Pd NCs. This review also examines the applications of Pd NCs to the electrocatalytic oxidation of formic acid, methanol, and ethanol as well as the reduction of O2, with an emphasis on their use in fuel cells. Finally, we outline our personal perspectives on future research directions that are underway with regard to catalytic uses of polyhedral Pd NCs.
2016, 32(9): 2185-2196
doi: 10.3866/PKU.WHXB201605255
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The crystal facet effect of photocatalysts has aroused increasing attention owing to its importance for the synthesis of novel photocatalysts, understanding photocatalytic mechanisms, and enhancing photocatalytic efficiency. In this paper, the research approaches, recently discovered phenomena, and the application of the facet effect of TiO2 are reviewed. The prospects and challenges of using the crystal facet effect of TiO2 photocatalysts are discussed.
The crystal facet effect of photocatalysts has aroused increasing attention owing to its importance for the synthesis of novel photocatalysts, understanding photocatalytic mechanisms, and enhancing photocatalytic efficiency. In this paper, the research approaches, recently discovered phenomena, and the application of the facet effect of TiO2 are reviewed. The prospects and challenges of using the crystal facet effect of TiO2 photocatalysts are discussed.
2016, 32(9): 2197-2208
doi: 10.3866/PKU.WHXB201605301
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It is the goal of density functional theory (DFT) researchers to develop the functional formalism of exchange-correlation (XC) with high accuracy and efficiency. Conventional functionals have issues when predicting the properties of the ground and excited states of atomic and molecular systems, and they do not show universal predictions. On the other hand, high-level theory methods such as the couple-cluster (CC) method and many-body perturbation theory (MBPT) based on GW (i.e., the dressed Green's function (G) and the dynamically screened Coulomb interaction (W)) approximation require very expensive computational cost and therefore the size of the systems studied and the practicability are limited. Recently, the optimally tuned range-separated (RS) functional has been developed to partly alleviate the above issues and has attracted great attention because it can achieve a level of accuracy comparable to the high-level method but with low computational cost. In this review, we first provide an overview of the theory in this field and then introduce the optimal tuning concept based on the RS functional. We combine the recent theoretical studies to evaluate their performance in practical calculations. Finally, we give some prospects for the future development and application of the optimally tuned approach.
It is the goal of density functional theory (DFT) researchers to develop the functional formalism of exchange-correlation (XC) with high accuracy and efficiency. Conventional functionals have issues when predicting the properties of the ground and excited states of atomic and molecular systems, and they do not show universal predictions. On the other hand, high-level theory methods such as the couple-cluster (CC) method and many-body perturbation theory (MBPT) based on GW (i.e., the dressed Green's function (G) and the dynamically screened Coulomb interaction (W)) approximation require very expensive computational cost and therefore the size of the systems studied and the practicability are limited. Recently, the optimally tuned range-separated (RS) functional has been developed to partly alleviate the above issues and has attracted great attention because it can achieve a level of accuracy comparable to the high-level method but with low computational cost. In this review, we first provide an overview of the theory in this field and then introduce the optimal tuning concept based on the RS functional. We combine the recent theoretical studies to evaluate their performance in practical calculations. Finally, we give some prospects for the future development and application of the optimally tuned approach.
2016, 32(9): 2209-2215
doi: 10.3866/PKU.WHXB201605262
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Reduced and skeletal mechanisms with high fidelity are urgently required for multi-dimensional computational fluid dynamics (CFD) combustion simulations. In this study, a series of reduced mechanisms were obtained by reducing a detailed mechanism of primary reference fuel (PRF) using the directed relation graphaided error propagation and sensitivity analysis (DRGEPSA) method for different reduction targets. By analyzing the structures of the reduced mechanisms, it is found that the mechanism structure significantly changes with the variation of the reduction target. Then, the performance of the reduced mechanism is evaluated based on the uncertainty quantification. It indicates that a small relative error should be used in the mechanism reduction method to avoid distorted predictions from the reduced mechanisms. Finally, the decoupling methodology is proposed to construct the skeletal mechanism of PRF. The results show that both the ignition delay time and the laminar flame speed can be satisfactorily reproduced by the skeletal mechanism with a detailed H2/CO/C1 and a skeletal C4-Cn sub-mechanism.
Reduced and skeletal mechanisms with high fidelity are urgently required for multi-dimensional computational fluid dynamics (CFD) combustion simulations. In this study, a series of reduced mechanisms were obtained by reducing a detailed mechanism of primary reference fuel (PRF) using the directed relation graphaided error propagation and sensitivity analysis (DRGEPSA) method for different reduction targets. By analyzing the structures of the reduced mechanisms, it is found that the mechanism structure significantly changes with the variation of the reduction target. Then, the performance of the reduced mechanism is evaluated based on the uncertainty quantification. It indicates that a small relative error should be used in the mechanism reduction method to avoid distorted predictions from the reduced mechanisms. Finally, the decoupling methodology is proposed to construct the skeletal mechanism of PRF. The results show that both the ignition delay time and the laminar flame speed can be satisfactorily reproduced by the skeletal mechanism with a detailed H2/CO/C1 and a skeletal C4-Cn sub-mechanism.
2016, 32(9): 2216-2222
doi: 10.3866/PKU.WHXB201605162
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The ignition delay times of gas-phase n-undecane/air mixtures in a heated shock tube were measured over a wide range of temperatures, from 731 to 1399 K, at pressures of approximately 2.02 × 105 and 10.10 × 105 Pa, and at equivalence ratios of 0.5, 1.0, and 2.0. This study represents the first-ever investigation of the shock tube ignition delay times of the n-undecane/air. The ignition delay times were determined by monitoring the reflected shock pressure and OH* emission at a location on the sidewall of the shock tube. The results show that the ignition delay time increases as the temperature is decreased above 910 K, then decreases with decreasing temperature between 910 and 780 K (thus exhibiting a negative temperature coefficient behavior), and finally increases again as the temperature is further reduced below 780 K. An increase in pressure was found to decrease the ignition delay time. The effect of the equivalence ratio on the ignition delay is different at the two experimental pressures, and the ignition delay is evidently highly sensitive to the equivalence ratio in the low temperature region compared with the high temperature region. The results obtained in this work are in good agreement with theoretical predictions generated using the LLNL (Lawrence Livermore National Laboratory) mechanism over the entire temperature range. The present data for the n-undecane/air were also compared with previously reported experimental ignition delay times for n-heptane/air, n-decane/air and ndodecane/ air, demonstrating that the ignition delay time decreases with increases in the number of carbon atoms in the n-alkane. Sensitivity analysis indicated that the reactions that primarily affect the ignition delay of nundecane at high and low temperatures are dramatically different. The most important reaction at high temperatures is H + O2 = O + OH, while at low temperatures the peroxy undecyl (C11H23O2) isomerization reactions predominate.
The ignition delay times of gas-phase n-undecane/air mixtures in a heated shock tube were measured over a wide range of temperatures, from 731 to 1399 K, at pressures of approximately 2.02 × 105 and 10.10 × 105 Pa, and at equivalence ratios of 0.5, 1.0, and 2.0. This study represents the first-ever investigation of the shock tube ignition delay times of the n-undecane/air. The ignition delay times were determined by monitoring the reflected shock pressure and OH* emission at a location on the sidewall of the shock tube. The results show that the ignition delay time increases as the temperature is decreased above 910 K, then decreases with decreasing temperature between 910 and 780 K (thus exhibiting a negative temperature coefficient behavior), and finally increases again as the temperature is further reduced below 780 K. An increase in pressure was found to decrease the ignition delay time. The effect of the equivalence ratio on the ignition delay is different at the two experimental pressures, and the ignition delay is evidently highly sensitive to the equivalence ratio in the low temperature region compared with the high temperature region. The results obtained in this work are in good agreement with theoretical predictions generated using the LLNL (Lawrence Livermore National Laboratory) mechanism over the entire temperature range. The present data for the n-undecane/air were also compared with previously reported experimental ignition delay times for n-heptane/air, n-decane/air and ndodecane/ air, demonstrating that the ignition delay time decreases with increases in the number of carbon atoms in the n-alkane. Sensitivity analysis indicated that the reactions that primarily affect the ignition delay of nundecane at high and low temperatures are dramatically different. The most important reaction at high temperatures is H + O2 = O + OH, while at low temperatures the peroxy undecyl (C11H23O2) isomerization reactions predominate.
2016, 32(9): 2223-2231
doi: 10.3866/PKU.WHXB201607152
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For thermal degradation of forest fuels, the optimization of kinetic parameters is a crucial step for the construction of comprehensive pyrolysis model. Traditional gradient- based optimization methods are characterized by strong converging speed, but with weak global optimization capability. The Darwinian survivalof- the-fittest theory based genetic algorithm (GA) is a good tool for global optimization, but with weak converging speed because of the general principles of this algorithm. In this study we evaluated the dependence of the pure GA on the setting of the initial values (IVs), and found that the use of the correct initial values accelerated the converging speed and stabilized the results of the GA. A hybrid genetic algorithm (HGA) was used when the IVs were unknown. This algorithm shares the merits of iterative algorithms and GA. Thermogravimetric experiments were performed using the branches of Pinus Sylvestris and the results were used to compare the converging performances of GA and HGA under the assumption of a three-step, first-order pyrolysis model. The results of these analyses verified the validity and reliability of the HGA.
For thermal degradation of forest fuels, the optimization of kinetic parameters is a crucial step for the construction of comprehensive pyrolysis model. Traditional gradient- based optimization methods are characterized by strong converging speed, but with weak global optimization capability. The Darwinian survivalof- the-fittest theory based genetic algorithm (GA) is a good tool for global optimization, but with weak converging speed because of the general principles of this algorithm. In this study we evaluated the dependence of the pure GA on the setting of the initial values (IVs), and found that the use of the correct initial values accelerated the converging speed and stabilized the results of the GA. A hybrid genetic algorithm (HGA) was used when the IVs were unknown. This algorithm shares the merits of iterative algorithms and GA. Thermogravimetric experiments were performed using the branches of Pinus Sylvestris and the results were used to compare the converging performances of GA and HGA under the assumption of a three-step, first-order pyrolysis model. The results of these analyses verified the validity and reliability of the HGA.
2016, 32(9): 2232-2240
doi: 10.3866/PKU.WHXB201605263
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Two novel ternary rare earth complexes [Ln(3,4-DEOBA)3DIPY]2DIPY (Ln = Er (1), Gd (2); 3,4- DEOBA = 3,4-diethoxybenzoate; DIPY = 2,2'-bipyridine) were synthesized and characterized by elemental analysis, infrared spectroscopy and X- ray single crystal diffraction. The experiments show that the two complexes are isomorphous with dinuclear structures, and adjacent structure units are stitched together through π-π interactions to form 1D chains and 2D-layered supramolecular structures. Simultaneous thermal analysis and Fourier transform infrared detection (TG-FTIR) was used to study the process of the thermal decomposition of the complexes. The molar heat capacity of the two complexes was obtained by differential scanning calorimetry (DSC). The smoothed values of the average molar heat capacity and thermodynamic functions of the complexes were calculated by the fitted polynomial and thermodynamic equations.
Two novel ternary rare earth complexes [Ln(3,4-DEOBA)3DIPY]2DIPY (Ln = Er (1), Gd (2); 3,4- DEOBA = 3,4-diethoxybenzoate; DIPY = 2,2'-bipyridine) were synthesized and characterized by elemental analysis, infrared spectroscopy and X- ray single crystal diffraction. The experiments show that the two complexes are isomorphous with dinuclear structures, and adjacent structure units are stitched together through π-π interactions to form 1D chains and 2D-layered supramolecular structures. Simultaneous thermal analysis and Fourier transform infrared detection (TG-FTIR) was used to study the process of the thermal decomposition of the complexes. The molar heat capacity of the two complexes was obtained by differential scanning calorimetry (DSC). The smoothed values of the average molar heat capacity and thermodynamic functions of the complexes were calculated by the fitted polynomial and thermodynamic equations.
2016, 32(9): 2241-2254
doi: 10.3866/PKU.WHXB201606132
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The stereochemical structures and absolute configuration-pharmacological activity relationship of chiral l,4-dihydropyridines (1,4-DHPs) calcium channel drugs were summarized. Additionally, the polymorphic forms of nimodipine were investigated. The absolute configurations of a pair of chiral nimodipines as a conglomerate prepared by spontaneous resolution under chiral crystallization were confirmed via X- ray crystallographic analysis directly correlated with their solid-state and solution electronic circular dichroism (ECD) spectra. The solid-state and solution ECD spectra of chiral l,4-DHPs were obtained for the first time. This comprehensive method can be used to determine the absolute configurations of small organic molecules. Furthermore, it can be extended to correlate the absolute configurations of other series of chiral l,4-DHP derivatives in the future. We also presented some effective techniques to distinguish polymorphs of chiral active pharmaceutical ingredients (APIs), which differ from the non-chiral conventional methods, to allow qualitative identification of different chiral crystalline states of APIs in pharmaceutical preparations.
The stereochemical structures and absolute configuration-pharmacological activity relationship of chiral l,4-dihydropyridines (1,4-DHPs) calcium channel drugs were summarized. Additionally, the polymorphic forms of nimodipine were investigated. The absolute configurations of a pair of chiral nimodipines as a conglomerate prepared by spontaneous resolution under chiral crystallization were confirmed via X- ray crystallographic analysis directly correlated with their solid-state and solution electronic circular dichroism (ECD) spectra. The solid-state and solution ECD spectra of chiral l,4-DHPs were obtained for the first time. This comprehensive method can be used to determine the absolute configurations of small organic molecules. Furthermore, it can be extended to correlate the absolute configurations of other series of chiral l,4-DHP derivatives in the future. We also presented some effective techniques to distinguish polymorphs of chiral active pharmaceutical ingredients (APIs), which differ from the non-chiral conventional methods, to allow qualitative identification of different chiral crystalline states of APIs in pharmaceutical preparations.
2016, 32(9): 2255-2263
doi: 10.3866/PKU.WHXB201605264
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5-(Benzyloxy)-isophthalic acid (BIC) derivatives and heptanol (HA) molecules adsorb on a highly oriented pyrolytic graphite (HOPG) surface. The surface forms a 2D network structure through weak hydrogen bond interactions. We used molecular dynamics to simulate this adsorption process and perform quantitative analysis of the characteristic parameters, such as the structure geometry, amount of energy, and the number, length and angle of the hydrogen bonds. We compared these results with the experimental result and performed correlational research on the forming tendency and stability between the hydrogen bonds and the chiral selfassembled structure.
5-(Benzyloxy)-isophthalic acid (BIC) derivatives and heptanol (HA) molecules adsorb on a highly oriented pyrolytic graphite (HOPG) surface. The surface forms a 2D network structure through weak hydrogen bond interactions. We used molecular dynamics to simulate this adsorption process and perform quantitative analysis of the characteristic parameters, such as the structure geometry, amount of energy, and the number, length and angle of the hydrogen bonds. We compared these results with the experimental result and performed correlational research on the forming tendency and stability between the hydrogen bonds and the chiral selfassembled structure.
2016, 32(9): 2264-2270
doi: 10.3866/PKU.WHXB201606141
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The adsorption behavior of radioiodine (I2) molecules on three different low-index surfaces of cuprous oxide (Cu2O) was systematically investigated using first-principles density functional calculations with periodic slab models. The role of typical surface adsorption sites was evaluated by calculating structural parameters of the adsorption configurations and energy features. Moderate geometry relaxation of the three low-index surfaces was observed. The results of geometry optimization and total energy calculations indicated that the Cu2O(100) and (111) surfaces exhibit higher reactivity towards I2 adsorption than the Cu2O(110) surface. The surface oxygen site (OS) was determined to be the most favorable adsorption site on the Cu2O(100) surface, while the coordinatively unsaturated copper site (CuCUS) was energetically preferred on the Cu2O(111) surface. In addition, the electronic structure information for several typical configurations were explored to explain the detailed interaction mechanism of adsorbed systems.
The adsorption behavior of radioiodine (I2) molecules on three different low-index surfaces of cuprous oxide (Cu2O) was systematically investigated using first-principles density functional calculations with periodic slab models. The role of typical surface adsorption sites was evaluated by calculating structural parameters of the adsorption configurations and energy features. Moderate geometry relaxation of the three low-index surfaces was observed. The results of geometry optimization and total energy calculations indicated that the Cu2O(100) and (111) surfaces exhibit higher reactivity towards I2 adsorption than the Cu2O(110) surface. The surface oxygen site (OS) was determined to be the most favorable adsorption site on the Cu2O(100) surface, while the coordinatively unsaturated copper site (CuCUS) was energetically preferred on the Cu2O(111) surface. In addition, the electronic structure information for several typical configurations were explored to explain the detailed interaction mechanism of adsorbed systems.
2016, 32(9): 2271-2279
doi: 10.3866/PKU.WHXB201606071
Abstract:
Black micro-arc oxide film layers were prepared on AZ40M magnesium alloy substrates by twostep micro-arc oxidation in a phosphate electrolyte with ferric citrate. The morphologies and compositions of these films were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) to provide details regarding the film formation mechanism. The results showed that the main component of the oxide films was magnesium oxide, with various iron compounds also being present, including ferroferric oxide, ferrous oxide, and metallic iron. These results indicate that the formation of black film can be attributed to the precipitation of these species during the oxidation of iron ions by ferric citrate in the electrolyte.
Black micro-arc oxide film layers were prepared on AZ40M magnesium alloy substrates by twostep micro-arc oxidation in a phosphate electrolyte with ferric citrate. The morphologies and compositions of these films were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) to provide details regarding the film formation mechanism. The results showed that the main component of the oxide films was magnesium oxide, with various iron compounds also being present, including ferroferric oxide, ferrous oxide, and metallic iron. These results indicate that the formation of black film can be attributed to the precipitation of these species during the oxidation of iron ions by ferric citrate in the electrolyte.
2016, 32(9): 2280-2286
doi: 10.3866/PKU.WHXB201605124
Abstract:
A highly ordered mesoporous Si/C composite was prepared by magnesiothermic reduction method, using SBA-15 as the precursor at 660 ℃ with subsequent carbon coating. This Si/C composite preserved the ordered honeycomb pore channels of SBA-15 and exhibited a lotus root-like structure with high packing density. A liquid ambient reaction model is proposed to explain the reaction between SBA-15 and magnesium powder at 660 ℃ as well as the mechanism by which the highly ordered mesoporous structure is generated. The phase composition and morphology of this material were analyzed by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption- desorption and Raman spectroscopy. The excellent electrochemical performance of the as- prepared material suggests potential applications as an anode material in second-generation Li-ion batteries.
A highly ordered mesoporous Si/C composite was prepared by magnesiothermic reduction method, using SBA-15 as the precursor at 660 ℃ with subsequent carbon coating. This Si/C composite preserved the ordered honeycomb pore channels of SBA-15 and exhibited a lotus root-like structure with high packing density. A liquid ambient reaction model is proposed to explain the reaction between SBA-15 and magnesium powder at 660 ℃ as well as the mechanism by which the highly ordered mesoporous structure is generated. The phase composition and morphology of this material were analyzed by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption- desorption and Raman spectroscopy. The excellent electrochemical performance of the as- prepared material suggests potential applications as an anode material in second-generation Li-ion batteries.
2016, 32(9): 2287-2292
doi: 10.3866/PKU.WHXB201605164
Abstract:
In this work, Li1.2Mn0.54Co0.13Ni0.13NaxO2 was prepared via an ion-exchange process combined with a solid- state reaction. Aberration- corrected scanning transmission electron microscopy (STEM), energydispersive X-ray spectroscopy (EDS), and electron energy loss spectroscopy (EELS) were all used to study the surface structure and chemical distribution of the resulting material. Nickel (Ni) was found to be enriched at the surface in regions perpendicular to the lithium diffusion channels (that is, the (200) surfaces) and also exhibited a tendency to diffuse into the lithium (Li) layers, generating a Fm3m rocksalt phase. In contrast, cobalt (Co) segregated along the transition metal (TM) layers of the (001) and (200) surfaces. The results of aging trials demonstrated that Co-enriched layers lead to surface structure instability, as evidenced by the formation of a large number of antisite defects (Li-TM) and rocksalt phase structures at the (001) surface during aging.
In this work, Li1.2Mn0.54Co0.13Ni0.13NaxO2 was prepared via an ion-exchange process combined with a solid- state reaction. Aberration- corrected scanning transmission electron microscopy (STEM), energydispersive X-ray spectroscopy (EDS), and electron energy loss spectroscopy (EELS) were all used to study the surface structure and chemical distribution of the resulting material. Nickel (Ni) was found to be enriched at the surface in regions perpendicular to the lithium diffusion channels (that is, the (200) surfaces) and also exhibited a tendency to diffuse into the lithium (Li) layers, generating a Fm3m rocksalt phase. In contrast, cobalt (Co) segregated along the transition metal (TM) layers of the (001) and (200) surfaces. The results of aging trials demonstrated that Co-enriched layers lead to surface structure instability, as evidenced by the formation of a large number of antisite defects (Li-TM) and rocksalt phase structures at the (001) surface during aging.
2016, 32(9): 2293-2300
doi: 10.3866/PKU.WHXB201605201
Abstract:
Nitrile-modified 2,5-di-tert-butyl-hydroquinones were synthesized and investigated as redox shuttle overcharge additives for LiFePO4/Li cells. The cyanoethylation reaction was utilized to synthesize the target molecules 2,5-di-tert-butyl-1,4-di(β-cyanoethoxyl)benzene (RS-DCN) and 2,5-di-tert-butyl-1-(β-cyanoethoxyl)- 4-methoxybenzene (RS-MCN) in high efficiency from 2,5-di-tert-butyl-hydroquinone and acrylonitrile. The solubility, cyclic voltammetric measurements, 5 V overcharge test, 100% overcharge test, high rate performance under 100% overcharge conditions, and cycle performance under normal conditions were studied in detail for the electrolyte with the addition of RS-DCN or RS-MCN. The RS-MCN compounds with the asymmetric structure delivered better solubility (with max. 0.3 mol·L-1 in 1.0 mol·L-1 LiPF6/EC+DEC+EMC, 1 : 1 : 1, in vol.), higher overcharge protection life (over 1200 h for the 5 V overcharge test), and excellent rate performance under 100% overcharge conditions (specific discharge capacity reached 153.5 mAh·g-1 at 2.5C). The addition of RS-MCN also improved the cycling performance of the LiFePO4/Li cell under the charge-discharge voltage range of 2.5-3.8 V.
Nitrile-modified 2,5-di-tert-butyl-hydroquinones were synthesized and investigated as redox shuttle overcharge additives for LiFePO4/Li cells. The cyanoethylation reaction was utilized to synthesize the target molecules 2,5-di-tert-butyl-1,4-di(β-cyanoethoxyl)benzene (RS-DCN) and 2,5-di-tert-butyl-1-(β-cyanoethoxyl)- 4-methoxybenzene (RS-MCN) in high efficiency from 2,5-di-tert-butyl-hydroquinone and acrylonitrile. The solubility, cyclic voltammetric measurements, 5 V overcharge test, 100% overcharge test, high rate performance under 100% overcharge conditions, and cycle performance under normal conditions were studied in detail for the electrolyte with the addition of RS-DCN or RS-MCN. The RS-MCN compounds with the asymmetric structure delivered better solubility (with max. 0.3 mol·L-1 in 1.0 mol·L-1 LiPF6/EC+DEC+EMC, 1 : 1 : 1, in vol.), higher overcharge protection life (over 1200 h for the 5 V overcharge test), and excellent rate performance under 100% overcharge conditions (specific discharge capacity reached 153.5 mAh·g-1 at 2.5C). The addition of RS-MCN also improved the cycling performance of the LiFePO4/Li cell under the charge-discharge voltage range of 2.5-3.8 V.
2016, 32(9): 2301-2308
doi: 10.3866/PKU.WHXB201606032
Abstract:
To investigate the electrochemical co-reduction mechanism associated with the formation of Mg- Zr alloys, the electrochemical behaviors of Zr(IV) in KCl-MgCl2-K2ZrF6 and KCl-MgCl2-K2ZrF6-ZrO2 melts were studied on a molybdenum electrode at 1023 K. Cyclic voltammograms (CVs) and square-wave voltammograms (SWVs) showed that Zr(IV) was reduced to Zr metal by a two-step mechanism consisting of the Zr(IV)/Zr(II) and Zr(II)/Zr(0) pairs in the KCl-MgCl2-K2ZrF6 melt. The dissolution of ZrO2 in the KCl-MgCl2-K2ZrF6 melt was ascertained from CVs, while the Zr(IV) concentration in the melt was assessed by inductively coupled plasma atomic emission spectrometry (ICP-AES). Mg-Zr alloys were obtained by galvanostatic electrolysis in KCl-MgCl2- K2ZrF6- KF- ZrO2 melts and subsequently characterized by X- ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). The Zr concentrations in the alloys as determined by ICP-AES were as high as 7.2% (w). The formation of Mg-Zr alloys could be controlled by varying both the reaction time and the melt composition. These results confirm the feasibility of the direct electrolysis of ZrO2 to obtain Mg-Zr alloys in KCl-MgCl2-K2ZrF6-ZrO2 melts.
To investigate the electrochemical co-reduction mechanism associated with the formation of Mg- Zr alloys, the electrochemical behaviors of Zr(IV) in KCl-MgCl2-K2ZrF6 and KCl-MgCl2-K2ZrF6-ZrO2 melts were studied on a molybdenum electrode at 1023 K. Cyclic voltammograms (CVs) and square-wave voltammograms (SWVs) showed that Zr(IV) was reduced to Zr metal by a two-step mechanism consisting of the Zr(IV)/Zr(II) and Zr(II)/Zr(0) pairs in the KCl-MgCl2-K2ZrF6 melt. The dissolution of ZrO2 in the KCl-MgCl2-K2ZrF6 melt was ascertained from CVs, while the Zr(IV) concentration in the melt was assessed by inductively coupled plasma atomic emission spectrometry (ICP-AES). Mg-Zr alloys were obtained by galvanostatic electrolysis in KCl-MgCl2- K2ZrF6- KF- ZrO2 melts and subsequently characterized by X- ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). The Zr concentrations in the alloys as determined by ICP-AES were as high as 7.2% (w). The formation of Mg-Zr alloys could be controlled by varying both the reaction time and the melt composition. These results confirm the feasibility of the direct electrolysis of ZrO2 to obtain Mg-Zr alloys in KCl-MgCl2-K2ZrF6-ZrO2 melts.
2016, 32(9): 2309-2317
doi: 10.3866/PKU.WHXB201605125
Abstract:
Surfactant structure is known to have a significant effect on the formation and properties of wormlike micelles. In the present study, a new trimeric anionic surfactant (sodium 2,2',2"-(benzene-1,3,5-triyltris(oxy)) tritetradecanoate, abbreviated as Ph-TrisC14Na) was synthesized from myristic acid and m-trihydroxybenzene. The viscoelastic properties of single component Ph-TrisC14Na and Ph-TrisC14Na/cationic additive systems were subsequently investigated by steady state and dynamic rheological measurements, using butyltrimethyl ammonium bromide (C4TAB), hexyltrimethyl ammonium bromide (C6TAB), and octyltrimethyl ammonium bromide (C8TAB) as the additives. The results show that the unique molecular structure of Ph-TrisC14Na enables the formation of wormlike micelles when this compound is the sole component of the solution, and generates solutions with significant viscoelasticity. The addition of cationic species further optimizes the molecular geometry of the Ph-TrisC14Na and promotes the rapid growth of wormlike micelles. Additives with longer hydrophobic chains have a marked effect on the viscoelasticity and the microstructure of the mixed solution systems. A 50 mmol·L-1 Ph-TrisC14Na solution exhibits a zero shear viscosity of 1535 Pa·s together with micelle lengths in the range of 4.0 to 7.5 μm at a C8TAB to Ph-TrisC14Na molar ratio of 0.5. The present system shows the advantage of using an oligomeric surfactant in viscoelastic surfactant solutions. The information obtained from this work should be beneficial with regard to expanding the scope of highly viscoelastic anionic wormlike micellar systems.
Surfactant structure is known to have a significant effect on the formation and properties of wormlike micelles. In the present study, a new trimeric anionic surfactant (sodium 2,2',2"-(benzene-1,3,5-triyltris(oxy)) tritetradecanoate, abbreviated as Ph-TrisC14Na) was synthesized from myristic acid and m-trihydroxybenzene. The viscoelastic properties of single component Ph-TrisC14Na and Ph-TrisC14Na/cationic additive systems were subsequently investigated by steady state and dynamic rheological measurements, using butyltrimethyl ammonium bromide (C4TAB), hexyltrimethyl ammonium bromide (C6TAB), and octyltrimethyl ammonium bromide (C8TAB) as the additives. The results show that the unique molecular structure of Ph-TrisC14Na enables the formation of wormlike micelles when this compound is the sole component of the solution, and generates solutions with significant viscoelasticity. The addition of cationic species further optimizes the molecular geometry of the Ph-TrisC14Na and promotes the rapid growth of wormlike micelles. Additives with longer hydrophobic chains have a marked effect on the viscoelasticity and the microstructure of the mixed solution systems. A 50 mmol·L-1 Ph-TrisC14Na solution exhibits a zero shear viscosity of 1535 Pa·s together with micelle lengths in the range of 4.0 to 7.5 μm at a C8TAB to Ph-TrisC14Na molar ratio of 0.5. The present system shows the advantage of using an oligomeric surfactant in viscoelastic surfactant solutions. The information obtained from this work should be beneficial with regard to expanding the scope of highly viscoelastic anionic wormlike micellar systems.
2016, 32(9): 2318-2326
doi: 10.3866/PKU.WHXB201605181
Abstract:
A supramolecular polymer brush composed of polyvinylpyrrolidone-cholesterol (PVP-Chol) was fabricated based on intermolecular hydrogen bonding between the ketone groups of the PVP moieties and the hydroxyl groups of the cholesterol, both in solution and at the air/water interface. These confirmations were confirmed by Fourier transform infrared (FT-IR) spectroscopy, surface pressure versus molecular area (π-A) isotherms, and atomic force microscopy (AFM). At surface pressures up to 2.5 mN·m-1, the interfacial film was composed of cholesterol-enriched regions and PVP-Chol nanofibril domains. Interestingly, oversurface pressures, the structure of the PVP-Chol-enriched domains evolved frominitial irregular shapes, to crescent and heart-shaped zones, and then to circular shapes. This transition indicated the controllability of such domains during compression of a complex monolayer at relatively low surface pressures. Above 2.5 mN·m-1, the circular PVP-Chol domains disappeared and fibrous aggregates were formed at the air/water interface. The height of the comb-like PVP-Chol nanofibrils could be reversibly varied between approximately 4.3 and 1.8 nm by adjusting the voltage applied to piezoceramics during the AFM scanning process. These results demonstrate that the reversible structural transformation of the PVP-Chol complex from cylindrical to elliptic cylindrical is induced by the applied force of the AFM tip up to a value of 1.0 mN·m-1. These data provide important and useful information that improves our understanding of the relationship between the structures and performances of supramolecular polymer brushes, and should extend the range of applications of cholesterol-functionalized polymers fabricated via a simple mixing strategy.
A supramolecular polymer brush composed of polyvinylpyrrolidone-cholesterol (PVP-Chol) was fabricated based on intermolecular hydrogen bonding between the ketone groups of the PVP moieties and the hydroxyl groups of the cholesterol, both in solution and at the air/water interface. These confirmations were confirmed by Fourier transform infrared (FT-IR) spectroscopy, surface pressure versus molecular area (π-A) isotherms, and atomic force microscopy (AFM). At surface pressures up to 2.5 mN·m-1, the interfacial film was composed of cholesterol-enriched regions and PVP-Chol nanofibril domains. Interestingly, oversurface pressures, the structure of the PVP-Chol-enriched domains evolved frominitial irregular shapes, to crescent and heart-shaped zones, and then to circular shapes. This transition indicated the controllability of such domains during compression of a complex monolayer at relatively low surface pressures. Above 2.5 mN·m-1, the circular PVP-Chol domains disappeared and fibrous aggregates were formed at the air/water interface. The height of the comb-like PVP-Chol nanofibrils could be reversibly varied between approximately 4.3 and 1.8 nm by adjusting the voltage applied to piezoceramics during the AFM scanning process. These results demonstrate that the reversible structural transformation of the PVP-Chol complex from cylindrical to elliptic cylindrical is induced by the applied force of the AFM tip up to a value of 1.0 mN·m-1. These data provide important and useful information that improves our understanding of the relationship between the structures and performances of supramolecular polymer brushes, and should extend the range of applications of cholesterol-functionalized polymers fabricated via a simple mixing strategy.
2016, 32(9): 2327-2336
doi: 10.3866/PKU.WHXB201606225
Abstract:
The production of 2,3-pentanedione from lactic acid over SiO2-supported alkali metal nitrates under various conditions was investigated. Using nitrate (NO3-) as the anion, the effect of alkali metal cations on Claisen condensation of lactic acid into 2,3-pentanedione was focused on. Among precursors such as LiNO3, NaNO3, KNO3, and CsNO3, CsNO3 displayed the best catalytic performance. Characterization of the fresh and used catalysts by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy revealed that all MNO3 (M = Li, Na, K, Cs) salts were transformed into alkali metal lactates during the reaction. Alkali metal lactates were identified as active species for catalytic Claisen condensation of lactic acid into 2,3-pentanedione. CO2 temperature-programmed desorption (TPD) results of the used catalysts showed that the CsNO3/SiO2 catalyst was the most alkaline. For that reason, the CsNO3/SiO2 catalyst displayed the highest catalytic performance of those examined. The effects of reaction temperature and loading amount of CsNO3 on reaction performance were also discussed. Over the 4.4% (x, molar fraction) CsNO3/SiO2 catalyst, a 54.1% yield of 2,3-pentanedione was achieved at 300 ℃.
The production of 2,3-pentanedione from lactic acid over SiO2-supported alkali metal nitrates under various conditions was investigated. Using nitrate (NO3-) as the anion, the effect of alkali metal cations on Claisen condensation of lactic acid into 2,3-pentanedione was focused on. Among precursors such as LiNO3, NaNO3, KNO3, and CsNO3, CsNO3 displayed the best catalytic performance. Characterization of the fresh and used catalysts by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy revealed that all MNO3 (M = Li, Na, K, Cs) salts were transformed into alkali metal lactates during the reaction. Alkali metal lactates were identified as active species for catalytic Claisen condensation of lactic acid into 2,3-pentanedione. CO2 temperature-programmed desorption (TPD) results of the used catalysts showed that the CsNO3/SiO2 catalyst was the most alkaline. For that reason, the CsNO3/SiO2 catalyst displayed the highest catalytic performance of those examined. The effects of reaction temperature and loading amount of CsNO3 on reaction performance were also discussed. Over the 4.4% (x, molar fraction) CsNO3/SiO2 catalyst, a 54.1% yield of 2,3-pentanedione was achieved at 300 ℃.
2016, 32(9): 2337-2345
doi: 10.3866/PKU.WHXB201605241
Abstract:
CeO2/NaY catalysts were prepared by incipient wetness impregnation. The influence of the calcination temperature and Ce content on the crystallinity and performance of the active species of the catalysts was studied in this paper. The synthesized catalysts were characterized by Raman spectroscopy, X- ray diffraction (XRD), low temperature nitrogen adsorption- desorption (Brunauer-Emmett-Teller (BET)), highresolution transmission electron microscopy (HR-TEM), and H2-temperature-programmed reduction (H2-TPR). The results indicate that the calcination temperature and the Ce content have an important influence on the morphology of the cerium species and whether they can be uniformly dispersed on the surface and channels of the zeolite, and on the interaction between the cerium species and zeolites, which affects the oxygenation and oxidation desulfurization properties of the cerium species of the catalysts. The oxygenation properties of the prepared catalysts are tested under normal temperature and atmospheric pressure. The maximum oxygen storage capacity is 1.44 mmol·g-1. The conversion rate of dibenzothiophene (DBT) reaches up to 90.10% within 240 min when a 20 mL mixture of octane and DBT as a model oil is treated by the addition of 0.20 g catalyst under 50 mL·min-1 of oxygen flow at 100 ℃. The initial concentration of DBT is 500 μg·g-1. The oxidation product is dibenzothiophene sulfone (DBTO2). Therefore, it is of great significance to develop zeolites modified by rare earth elements to complex as functionalized catalysts with molecular oxygen for deep desulfurization of fuel oil, which can be easily done by air or oxygen oxidation without secondary pollution.
CeO2/NaY catalysts were prepared by incipient wetness impregnation. The influence of the calcination temperature and Ce content on the crystallinity and performance of the active species of the catalysts was studied in this paper. The synthesized catalysts were characterized by Raman spectroscopy, X- ray diffraction (XRD), low temperature nitrogen adsorption- desorption (Brunauer-Emmett-Teller (BET)), highresolution transmission electron microscopy (HR-TEM), and H2-temperature-programmed reduction (H2-TPR). The results indicate that the calcination temperature and the Ce content have an important influence on the morphology of the cerium species and whether they can be uniformly dispersed on the surface and channels of the zeolite, and on the interaction between the cerium species and zeolites, which affects the oxygenation and oxidation desulfurization properties of the cerium species of the catalysts. The oxygenation properties of the prepared catalysts are tested under normal temperature and atmospheric pressure. The maximum oxygen storage capacity is 1.44 mmol·g-1. The conversion rate of dibenzothiophene (DBT) reaches up to 90.10% within 240 min when a 20 mL mixture of octane and DBT as a model oil is treated by the addition of 0.20 g catalyst under 50 mL·min-1 of oxygen flow at 100 ℃. The initial concentration of DBT is 500 μg·g-1. The oxidation product is dibenzothiophene sulfone (DBTO2). Therefore, it is of great significance to develop zeolites modified by rare earth elements to complex as functionalized catalysts with molecular oxygen for deep desulfurization of fuel oil, which can be easily done by air or oxygen oxidation without secondary pollution.
2016, 32(9): 2346-2354
doi: 10.3866/PKU.WHXB201605163
Abstract:
The solution-processable, anthraquinone-based, fluorene bipolar fluorescent material 2-(9,9'-bis (2-ethylhexyl)-9H-fluoren-2-yl)anthracene-9,10- dione (FAA) was synthesized via a Suzuki reaction. The photophysical properties of FAAwere subsequently investigated by acquiring absorption and photoluminescence spectra, and its optical properties were studied using computational density functional theory methods. Data obtained from single-carrier devices incorporating FAA demonstrated its well-matched bipolar charge-transport characteristics. The electroluminescence performance of this material was also examined by doping FAA into a 1,3-di(9H-carbazol-9-yl)benzene (mCP) matrix as the light-emitting layer via spin coating to produce an organic light-emitting diode (OLED) with an indiumtin oxide (ITO)/poly(3,4-ethylenedioxythiophene:poly(styrenesulfonate) (PEDOT:PSS)/mCP:FAA/3,3'-(5'-(3-(pyridin-3-yl)phenyl)-[1,1':3',1"-terphen-yl]-3,3"-diyl)dipyridine (TmPyPb)/ LiF/Al structure. This device exhibited a maximum luminance of 1719 cd·m-2 with a turn-on voltage of 7.4 V, along with maximum current and power efficiencies of 1.66 cd·A-1 and 0.56 lm·W-1, respectively. The electroluminescence mechanism of the OLED is discussed based on the energy level diagrams of the functional layers.
The solution-processable, anthraquinone-based, fluorene bipolar fluorescent material 2-(9,9'-bis (2-ethylhexyl)-9H-fluoren-2-yl)anthracene-9,10- dione (FAA) was synthesized via a Suzuki reaction. The photophysical properties of FAAwere subsequently investigated by acquiring absorption and photoluminescence spectra, and its optical properties were studied using computational density functional theory methods. Data obtained from single-carrier devices incorporating FAA demonstrated its well-matched bipolar charge-transport characteristics. The electroluminescence performance of this material was also examined by doping FAA into a 1,3-di(9H-carbazol-9-yl)benzene (mCP) matrix as the light-emitting layer via spin coating to produce an organic light-emitting diode (OLED) with an indiumtin oxide (ITO)/poly(3,4-ethylenedioxythiophene:poly(styrenesulfonate) (PEDOT:PSS)/mCP:FAA/3,3'-(5'-(3-(pyridin-3-yl)phenyl)-[1,1':3',1"-terphen-yl]-3,3"-diyl)dipyridine (TmPyPb)/ LiF/Al structure. This device exhibited a maximum luminance of 1719 cd·m-2 with a turn-on voltage of 7.4 V, along with maximum current and power efficiencies of 1.66 cd·A-1 and 0.56 lm·W-1, respectively. The electroluminescence mechanism of the OLED is discussed based on the energy level diagrams of the functional layers.
2016, 32(9): 2355-2363
doi: 10.3866/PKU.WHXB201605171
Abstract:
Protein kinases play critical roles in many biological processes, including signal transduction, gene transcription, and protein translation, and are therefore closely associated with various disease states. The screening of kinase inhibitors has become an important aspect of anti-tumor drug development, and has been refined to allow high-throughput, multi-target screening based on the entire human kinome. To reduce the experimental costs of large-scale inhibitor screening and to increase the success rate, our group has designed a multi-target molecular docking systemcapable of predicting kinase-inhibitor interactions. In this work we initially used homology modeling to construct three-dimensional (3D) models for approximately 500 catalytic domains of human kinase variants. We subsequently performed molecular docking to calculate the binding affinities of kinase-inhibitor pairs, employing the 3D models as receptors and kinase inhibitors as ligands. The results show that our multi-target docking system accurately predicts the interactions between known inhibitors and kinase variants, and that the calculated binding affinities are highly correlated with the experimental values. Thus, this molecular docking system could be used for computational screening of multi-target kinase inhibitors, thereby providing a theoretical basis for the development of kinase inhibitors and the design of anti-tumor drugs.
Protein kinases play critical roles in many biological processes, including signal transduction, gene transcription, and protein translation, and are therefore closely associated with various disease states. The screening of kinase inhibitors has become an important aspect of anti-tumor drug development, and has been refined to allow high-throughput, multi-target screening based on the entire human kinome. To reduce the experimental costs of large-scale inhibitor screening and to increase the success rate, our group has designed a multi-target molecular docking systemcapable of predicting kinase-inhibitor interactions. In this work we initially used homology modeling to construct three-dimensional (3D) models for approximately 500 catalytic domains of human kinase variants. We subsequently performed molecular docking to calculate the binding affinities of kinase-inhibitor pairs, employing the 3D models as receptors and kinase inhibitors as ligands. The results show that our multi-target docking system accurately predicts the interactions between known inhibitors and kinase variants, and that the calculated binding affinities are highly correlated with the experimental values. Thus, this molecular docking system could be used for computational screening of multi-target kinase inhibitors, thereby providing a theoretical basis for the development of kinase inhibitors and the design of anti-tumor drugs.
2016, 32(9): 2364-2368
doi: 10.3866/PKU.WHXB201605182
Abstract:
Silicon surfaces are promising interfaces because they are mechanically and chemically resilient, able to resist wear in aqueous and organic environments, and display good electrical properties. There are a number of methods that are used to thiolate a silicon surface, notably through the attachment of molecules that contain terminal ―SH moieties. These methods usually suffer from long reaction times. In the present work, we developed an alternative method for thiolation of a silicon surface by introducing terminal thiol groups directly onto the silicon surface. The developed wet chemical process relies on chlorination and then surface thiolation and requires less time for grafting thiol groups on the silicon substrate. X-ray photoelectron spectroscopy (XPS) and contact angle measurement were employed for surface characterization after each step.
Silicon surfaces are promising interfaces because they are mechanically and chemically resilient, able to resist wear in aqueous and organic environments, and display good electrical properties. There are a number of methods that are used to thiolate a silicon surface, notably through the attachment of molecules that contain terminal ―SH moieties. These methods usually suffer from long reaction times. In the present work, we developed an alternative method for thiolation of a silicon surface by introducing terminal thiol groups directly onto the silicon surface. The developed wet chemical process relies on chlorination and then surface thiolation and requires less time for grafting thiol groups on the silicon substrate. X-ray photoelectron spectroscopy (XPS) and contact angle measurement were employed for surface characterization after each step.
2016, 32(9): 2369-2376
doi: 10.3866/PKU.WHXB201606031
Abstract:
Polymer light emitting devices incorporating poly(9-vinylcarbazole) (PVK):2,2'-(1,3-phenylene)-bis [5-(4-tert-butylphenyl)-1,3,4-oxadiazole] (OXD-7) as the co-host and the thermally activated delayed fluorescence compound 2,4,5,6-tetrakis(carbazol-9-yl)-1,3-dicyanobenzene (4CzIPN) as the emissive dopant exhibited a peak external quantum efficiency of 13%. In addition, 4CzIPN-sensitized (5,6,11,12)-tetraphenyl-naphthacene (Rubrene) devices gave a peak external quantum efficiency of 9.2%, a value that is 5.4 times that of analogous devices without 4CzIPN. Based on transient luminescence measurements, the working mechanism for 4CzIPN sensitization was determined to be Förster energy transfer from 4CzIPN to Rubrene. This work assessed the effects of the Rubrene concentration and the carrier transport balance in the emission layer on the device properties, and the results suggest that the self-aggregation of Rubrene may limit device efficiency.
Polymer light emitting devices incorporating poly(9-vinylcarbazole) (PVK):2,2'-(1,3-phenylene)-bis [5-(4-tert-butylphenyl)-1,3,4-oxadiazole] (OXD-7) as the co-host and the thermally activated delayed fluorescence compound 2,4,5,6-tetrakis(carbazol-9-yl)-1,3-dicyanobenzene (4CzIPN) as the emissive dopant exhibited a peak external quantum efficiency of 13%. In addition, 4CzIPN-sensitized (5,6,11,12)-tetraphenyl-naphthacene (Rubrene) devices gave a peak external quantum efficiency of 9.2%, a value that is 5.4 times that of analogous devices without 4CzIPN. Based on transient luminescence measurements, the working mechanism for 4CzIPN sensitization was determined to be Förster energy transfer from 4CzIPN to Rubrene. This work assessed the effects of the Rubrene concentration and the carrier transport balance in the emission layer on the device properties, and the results suggest that the self-aggregation of Rubrene may limit device efficiency.
2016, 32(9): 2377-2382
doi: 10.3866/PKU.WHXB201605242
Abstract:
ZIF-8 (zeolitic imidazolate framework-8), a kind of metal-organic framework material, is one of the most important energy materials and widely used in various fields because of its high specific surface area and excellent thermal stability. In this research, we synthesized ZIF-8 by the traditional hydrothermal synthesis method in a purely methanol system. The obtained particles were ~250 nm in diameter with a rhombic dodecahedron morphology. Moreover, the prepared ZIF-8 materials exhibited good thermal stability and a large surface area. We also found that the rhombic dodecahedral ZIF-8 enhanced the electro-optical (E-O) properties of nematic liquid crystal (N-LC) depending on the ZIF-8 doping concentrations. ZIF-8 in N-LC cells adsorbs ionic impurities and suppresses the screen effect, leading to a lower driving voltage and faster response time. At a ZIF-8 doping concentration of 0.05%(w, mass fraction), the N-LC cells showed the best E-O properties, including the lowest threshold voltage (Vth) of 0.92 V, the lowest saturation voltage (Vsat) of 1.31 V, and a short response time of 10.04 ms. However, above a doping concentration of 0.05%(w) ZIF-8 aggregated in N-LC cells, affecting the arrangement of the LC molecules and trapping less impurity ions, which deteriorated the E-O properties of N-LC.
ZIF-8 (zeolitic imidazolate framework-8), a kind of metal-organic framework material, is one of the most important energy materials and widely used in various fields because of its high specific surface area and excellent thermal stability. In this research, we synthesized ZIF-8 by the traditional hydrothermal synthesis method in a purely methanol system. The obtained particles were ~250 nm in diameter with a rhombic dodecahedron morphology. Moreover, the prepared ZIF-8 materials exhibited good thermal stability and a large surface area. We also found that the rhombic dodecahedral ZIF-8 enhanced the electro-optical (E-O) properties of nematic liquid crystal (N-LC) depending on the ZIF-8 doping concentrations. ZIF-8 in N-LC cells adsorbs ionic impurities and suppresses the screen effect, leading to a lower driving voltage and faster response time. At a ZIF-8 doping concentration of 0.05%(w, mass fraction), the N-LC cells showed the best E-O properties, including the lowest threshold voltage (Vth) of 0.92 V, the lowest saturation voltage (Vsat) of 1.31 V, and a short response time of 10.04 ms. However, above a doping concentration of 0.05%(w) ZIF-8 aggregated in N-LC cells, affecting the arrangement of the LC molecules and trapping less impurity ions, which deteriorated the E-O properties of N-LC.
