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2017 Volume 33 Issue 8
2017, 33(8):
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2017, 33(8): 1499-1500
doi: 10.3866/PKU.WHXB201705122
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2017, 33(8): 1501-1502
doi: 10.3866/PKU.WHXB201705172
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2017, 33(8): 1503-1504
doi: 10.3866/PKU.WHXB201705086
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2017, 33(8): 1505-1507
doi: 10.3866/PKU.WHXB201705126
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2017, 33(8): 1510-1511
doi: 10.3866/PKU.WHXB201705171
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2017, 33(8): 1512-1513
doi: 10.3866/PKU.WHXB201705173
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2017, 33(8): 1520-1532
doi: 10.3866/PKU.WHXB201704271
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DNA possesses extraordinary molecular recognition properties and remarkable structural features in the nano-level material regulation fields, which have shown enormous applications in many areas. In this review, we focus on DNA nanotechnology, including aspects ranging from modular DNA self-assembly to DNA origami, in addition to the recently reported novel assembly methods. Moreover, we summarize some applications of DNA nanotechnology, such as DNA-directed nanoparticle spatial positioning and orientation, and well-defined assembly of proteins on the DNA structure, as well as its uses, such as in the biomedical field, etc. The development and potential applications of DNA nanotechnology are also discussed.
DNA possesses extraordinary molecular recognition properties and remarkable structural features in the nano-level material regulation fields, which have shown enormous applications in many areas. In this review, we focus on DNA nanotechnology, including aspects ranging from modular DNA self-assembly to DNA origami, in addition to the recently reported novel assembly methods. Moreover, we summarize some applications of DNA nanotechnology, such as DNA-directed nanoparticle spatial positioning and orientation, and well-defined assembly of proteins on the DNA structure, as well as its uses, such as in the biomedical field, etc. The development and potential applications of DNA nanotechnology are also discussed.
2017, 33(8): 1533-1547
doi: 10.3866/PKU.WHXB201704281
Abstract:
An important component in lithium-ion batteries, the separator consists of porous polyolefin polymeric materials; the corresponding electrolyte is a liquid one composed of organic carbonate solvents and lithium hexafluorophosphate. Although the liquid electrolyte shows high lithium ion conductivity, its flammability poses a risk to the lithium-ion battery. A gel polymer separator prepared from a polymer that can gel the liquid electrolyte combines the advantages of high conductivity of the liquid electrolyte system and the safety of the solid electrolyte. Examples include the simple microporous gel polymer separator, the gel polymer separator doped with a small amount of nano-inorganic particles, and the gel ceramic separator with a large amount of nanoparticles. In this review, the physical and chemical properties of these gel polymer separators and development trends of gel polymer separators are discussed in detail.
An important component in lithium-ion batteries, the separator consists of porous polyolefin polymeric materials; the corresponding electrolyte is a liquid one composed of organic carbonate solvents and lithium hexafluorophosphate. Although the liquid electrolyte shows high lithium ion conductivity, its flammability poses a risk to the lithium-ion battery. A gel polymer separator prepared from a polymer that can gel the liquid electrolyte combines the advantages of high conductivity of the liquid electrolyte system and the safety of the solid electrolyte. Examples include the simple microporous gel polymer separator, the gel polymer separator doped with a small amount of nano-inorganic particles, and the gel ceramic separator with a large amount of nanoparticles. In this review, the physical and chemical properties of these gel polymer separators and development trends of gel polymer separators are discussed in detail.
2017, 33(8): 1548-1572
doi: 10.3866/PKU.WHXB201704283
Abstract:
Organic light-emitting diodes (OLEDs) have been developing rapidly in terms of materials and design over the past 30 years. They have been applied on large scales in displays, especially in high-end smartphones. However, in the field of lighting, the industry is not sufficiently mature because of the low efficiency, short life, and high cost of OLEDs. The main reason for this is that the optical waveguide effect and surface plasmon losses lead to the consumption of most of the optical energy coupled to the non-radiative thermal energy, resulting in a huge gap between the internal and external quantum efficiency. It is also one of the main causes for the poor efficiency and longevity. Therefore, it is necessary to recover the part of the light trapped inside OLED lighting devices via light extraction technology. In this paper, we introduce optical analytic methods for OLEDs by analyzing the four modes of light coupling channels and the mechanisms of light energy loss based on the ray-optical model. Then, based on the research achievements of some scientific institutions and recent representative patents in the industry, we summarize the relevant light extraction technology considering two aspects:external light extraction and internal light extraction. Finally, we discuss the development route and prospects of the light extraction technology.
Organic light-emitting diodes (OLEDs) have been developing rapidly in terms of materials and design over the past 30 years. They have been applied on large scales in displays, especially in high-end smartphones. However, in the field of lighting, the industry is not sufficiently mature because of the low efficiency, short life, and high cost of OLEDs. The main reason for this is that the optical waveguide effect and surface plasmon losses lead to the consumption of most of the optical energy coupled to the non-radiative thermal energy, resulting in a huge gap between the internal and external quantum efficiency. It is also one of the main causes for the poor efficiency and longevity. Therefore, it is necessary to recover the part of the light trapped inside OLED lighting devices via light extraction technology. In this paper, we introduce optical analytic methods for OLEDs by analyzing the four modes of light coupling channels and the mechanisms of light energy loss based on the ray-optical model. Then, based on the research achievements of some scientific institutions and recent representative patents in the industry, we summarize the relevant light extraction technology considering two aspects:external light extraction and internal light extraction. Finally, we discuss the development route and prospects of the light extraction technology.
2017, 33(8): 1573-1588
doi: 10.3866/PKU.WHXB201704284
Abstract:
In addition to being the energy powerhouse of the cell, mitochondria are an important source of reactive oxygen species (ROS) during the process of molecular oxygen metabolism. Mitochondrial ROS are closely associated with normal physiological functions as well as human diseases, and participate in cell signaling, nucleic acid and protein damage, and oxidative stress induction. However, the complicated interplay between mitochondrial ROS and the cellular pathological state has not been fully elucidated. It is expected that research on the mitochondrial ROS undertaking in the molecular pathogenesis of human diseases would benefit from development of efficient tools for the detection of these ROS. In recent years, an increasing number of fluorescent probes for mitochondrial ROS with high sensitivity and selectivity have been developed. Here, we present a review of the recent advances in small molecular fluorescent probes for selective detection of ROS inside the mitochondria. In this review, the design, synthesis, characteristics, and applications of the published fluorescent probes for mitochondrial ROS are discussed in detail.
In addition to being the energy powerhouse of the cell, mitochondria are an important source of reactive oxygen species (ROS) during the process of molecular oxygen metabolism. Mitochondrial ROS are closely associated with normal physiological functions as well as human diseases, and participate in cell signaling, nucleic acid and protein damage, and oxidative stress induction. However, the complicated interplay between mitochondrial ROS and the cellular pathological state has not been fully elucidated. It is expected that research on the mitochondrial ROS undertaking in the molecular pathogenesis of human diseases would benefit from development of efficient tools for the detection of these ROS. In recent years, an increasing number of fluorescent probes for mitochondrial ROS with high sensitivity and selectivity have been developed. Here, we present a review of the recent advances in small molecular fluorescent probes for selective detection of ROS inside the mitochondria. In this review, the design, synthesis, characteristics, and applications of the published fluorescent probes for mitochondrial ROS are discussed in detail.
2017, 33(8): 1589-1598
doi: 10.3866/PKU.WHXB201704142
Abstract:
Nano self-assembled γ-Al2O3, having two kinds of nano-scale pore structures, which can be used as a catalyst carrier suitable for large molecule diffusion and shale gas reservoir models. Characterization of the pore structures in nanomaterials are scanning electron microscopy, nitrogen adsorption method, mercury injection method, etc. These characterization techniques have their own limitations. This paper utilized nuclear magnetic resonance (NMR) relaxation measurements to study and quantitatively characterize the pore structures of nano self-assembled γ-Al2O3. Random walker simulation and error function analysis were used to explore the surface relaxation strength and pore size distribution of nano self-assembled γ-Al2O3. The random walker simulation results show that the main apertures of nano self-assembled γ-Al2O3 are 5-7 nm and 30-42 nm; NMR experiments through error function analysis show that the main apertures of the nano self-assembled material are 5-9 nm and 29-47 nm. Nitrogen adsorption only characterized the microporous, mesoporous, and part of the macroporous structures. The pore diameters greater than 100 nm cannot be detected by the nitrogen adsorption method. The mercury injection method characterizes apertures of size less than 10 nm relatively inaccurately. Nuclear magnetic relaxation can comprehensively characterize bimodal pore system of nano self-assembled γ-Al2O3 of size 2.8-315 nm. As one of the NMR measurements, the T2 spectrum signal amplitude ratio of three samples, S-1, S-2 and S-3 are 0.603, 1.15, 1.84, directly reflect the variety of their micropores and mesopores chemical Al2O3 material ratio 0.85, 1.38, 1.7 respectively. The suggested method can be applied to the investigation for shale gas pore structure and associated mechanisms.
Nano self-assembled γ-Al2O3, having two kinds of nano-scale pore structures, which can be used as a catalyst carrier suitable for large molecule diffusion and shale gas reservoir models. Characterization of the pore structures in nanomaterials are scanning electron microscopy, nitrogen adsorption method, mercury injection method, etc. These characterization techniques have their own limitations. This paper utilized nuclear magnetic resonance (NMR) relaxation measurements to study and quantitatively characterize the pore structures of nano self-assembled γ-Al2O3. Random walker simulation and error function analysis were used to explore the surface relaxation strength and pore size distribution of nano self-assembled γ-Al2O3. The random walker simulation results show that the main apertures of nano self-assembled γ-Al2O3 are 5-7 nm and 30-42 nm; NMR experiments through error function analysis show that the main apertures of the nano self-assembled material are 5-9 nm and 29-47 nm. Nitrogen adsorption only characterized the microporous, mesoporous, and part of the macroporous structures. The pore diameters greater than 100 nm cannot be detected by the nitrogen adsorption method. The mercury injection method characterizes apertures of size less than 10 nm relatively inaccurately. Nuclear magnetic relaxation can comprehensively characterize bimodal pore system of nano self-assembled γ-Al2O3 of size 2.8-315 nm. As one of the NMR measurements, the T2 spectrum signal amplitude ratio of three samples, S-1, S-2 and S-3 are 0.603, 1.15, 1.84, directly reflect the variety of their micropores and mesopores chemical Al2O3 material ratio 0.85, 1.38, 1.7 respectively. The suggested method can be applied to the investigation for shale gas pore structure and associated mechanisms.
2017, 33(8): 1599-1604
doi: 10.3866/PKU.WHXB201704194
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Quantification and characterization of hydrate formation and dissociation in sediments are highly important in the study of the physical properties of hydrate-bearing sediments. In this paper, the behavior of CO2 hydrate formation and dissociation in sand is studied using the nuclear magnetic resonance (NMR) technique. The components of the pore space, including gas, liquid water, and hydrate, were quantified using a convenient method by which the hydration number was determined. No abrupt change in the relaxation behavior of the sample was found during hydrate formation and dissociation. In addition, the value of mean-log T22 appeared to be proportional to the liquid water content of the sample with or without the pore hydrate. A straightforward explanation is that the liquid water in the pore space remains in contact with grain surfaces, and relaxation occurs mainly at the grain surface. The results suggest that, rather than coating the grains, the hydrate is pore-filling or cementing.
Quantification and characterization of hydrate formation and dissociation in sediments are highly important in the study of the physical properties of hydrate-bearing sediments. In this paper, the behavior of CO2 hydrate formation and dissociation in sand is studied using the nuclear magnetic resonance (NMR) technique. The components of the pore space, including gas, liquid water, and hydrate, were quantified using a convenient method by which the hydration number was determined. No abrupt change in the relaxation behavior of the sample was found during hydrate formation and dissociation. In addition, the value of mean-log T22 appeared to be proportional to the liquid water content of the sample with or without the pore hydrate. A straightforward explanation is that the liquid water in the pore space remains in contact with grain surfaces, and relaxation occurs mainly at the grain surface. The results suggest that, rather than coating the grains, the hydrate is pore-filling or cementing.
2017, 33(8): 1605-1613
doi: 10.3866/PKU.WHXB201704145
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In this work, we present a new design for a surface protective layer formed by a facile aqueous solution process in which a nano-architectured layer of LiFePO4 is grown on a Li-rich cathode material, Li1.2Mn0.54Ni0.13Co0.13O2. The coated samples are then calcined at 400 or 500℃ for 5 h. The sample after calcination at 400℃ demonstrates a high initial columbic efficiency of 91.9%, a large reversible capacity of 295.0 mAh·g-1 at 0.1C (1C=300 mA·g-1), and excellent cyclability with a capacity of 206.7 mAh·g-1after 100 cycles at 1C. Meanwhile, voltage fading of the coated sample is effectively suppressed by protection offered by a LiFePO4 coating layer. These superior electrochemical performances are attributed to the coating layer, which not only protects the Li-rich cathode material from side reaction with the electrolyte and maintains the stability of the interface structure, but also provides excess reversible capacity.
In this work, we present a new design for a surface protective layer formed by a facile aqueous solution process in which a nano-architectured layer of LiFePO4 is grown on a Li-rich cathode material, Li1.2Mn0.54Ni0.13Co0.13O2. The coated samples are then calcined at 400 or 500℃ for 5 h. The sample after calcination at 400℃ demonstrates a high initial columbic efficiency of 91.9%, a large reversible capacity of 295.0 mAh·g-1 at 0.1C (1C=300 mA·g-1), and excellent cyclability with a capacity of 206.7 mAh·g-1after 100 cycles at 1C. Meanwhile, voltage fading of the coated sample is effectively suppressed by protection offered by a LiFePO4 coating layer. These superior electrochemical performances are attributed to the coating layer, which not only protects the Li-rich cathode material from side reaction with the electrolyte and maintains the stability of the interface structure, but also provides excess reversible capacity.
2017, 33(8): 1614-1620
doi: 10.3866/PKU.WHXB201704181
Abstract:
A direct carbon solid oxide fuel cell (DC-SOFC) stack was prepared with 3 tubular cells electrically connected in series. To increase carbon storage in the stack, the anode was fabricated outside the tubular cells so that carbon fuel can be loaded at the exterior of the stack, which is more spacious than the interior. The 3-cell-stack is operated directly with carbon as the fuel and oxygen in ambient air as the oxidant. With a total effective area of 10.2 cm2 and a 5% (w) Fe-loaded activated carbon fuel of 17 g, the stack reveals a peak power of 4.1 W at 800℃. The stack discharged at a constant current of 1.0 A for 19 h, giving a charge capacity of 19 A·h and an energy capacity of 31.6 W·h, which are much higher than those of a similar stack with anode on the inside and carbon loaded at the interior. The high capacity of our DC-SOFC opens up potential applications in portable devices.
A direct carbon solid oxide fuel cell (DC-SOFC) stack was prepared with 3 tubular cells electrically connected in series. To increase carbon storage in the stack, the anode was fabricated outside the tubular cells so that carbon fuel can be loaded at the exterior of the stack, which is more spacious than the interior. The 3-cell-stack is operated directly with carbon as the fuel and oxygen in ambient air as the oxidant. With a total effective area of 10.2 cm2 and a 5% (w) Fe-loaded activated carbon fuel of 17 g, the stack reveals a peak power of 4.1 W at 800℃. The stack discharged at a constant current of 1.0 A for 19 h, giving a charge capacity of 19 A·h and an energy capacity of 31.6 W·h, which are much higher than those of a similar stack with anode on the inside and carbon loaded at the interior. The high capacity of our DC-SOFC opens up potential applications in portable devices.
2017, 33(8): 1621-1627
doi: 10.3866/PKU.WHXB201704191
Abstract:
SnS2 is considered as an attractive anode material to substitute commercial graphite anodes of lithium-ion batteries due to its high specific capacity of 645 mAh·g-1 as well as low cost. Nevertheless, it suffers poor large volume expansion during the lithiation/delithiation processes, leading to the loss of electrical contact and rapid capacity fading. Herein, by using a facile one-step solvothermal method, SnS2 nanoflower/graphene nanocomposites (SnS2 NF/GNs) were prepared, where flower-like SnS2 hierarchical nanostructures consisting of ultrathin nanoplates, are tightly enwrapped in graphene nanosheets. As anode materials for lithium-ion batteries, the SnS2 NF/GNs electrode exhibit superior electrochemical performance, with a reversible capacity of 523 mAh·g-1 after 200 charge-discharge cycles. The enhanced Li storage performance was attributed to the synergistic effect of SnS2 and graphene. The SnS2 NF can effectively accommodate the volume change and shorten Li+ diffusion distance, while graphene nanosheets can further alleviate the volume expansion of SnS2 and improve the electronic conductivity.
SnS2 is considered as an attractive anode material to substitute commercial graphite anodes of lithium-ion batteries due to its high specific capacity of 645 mAh·g-1 as well as low cost. Nevertheless, it suffers poor large volume expansion during the lithiation/delithiation processes, leading to the loss of electrical contact and rapid capacity fading. Herein, by using a facile one-step solvothermal method, SnS2 nanoflower/graphene nanocomposites (SnS2 NF/GNs) were prepared, where flower-like SnS2 hierarchical nanostructures consisting of ultrathin nanoplates, are tightly enwrapped in graphene nanosheets. As anode materials for lithium-ion batteries, the SnS2 NF/GNs electrode exhibit superior electrochemical performance, with a reversible capacity of 523 mAh·g-1 after 200 charge-discharge cycles. The enhanced Li storage performance was attributed to the synergistic effect of SnS2 and graphene. The SnS2 NF can effectively accommodate the volume change and shorten Li+ diffusion distance, while graphene nanosheets can further alleviate the volume expansion of SnS2 and improve the electronic conductivity.
2017, 33(8): 1628-1634
doi: 10.3866/PKU.WHXB201704242
Abstract:
This work describes the preparation of three kinds of PtPd/graphene (PtPd/G) nanocatalysts. Graphene oxide was first prepared as the carrier precursor by the Hummers method, and subsequently, the simultaneous reduction of graphene oxide and the metal precursor led to the in situ loading of PtPd on graphene. The fabrication procedure involving liquid phase co-reduction and successive reduction methods utilized the block copolymer P123 as a reducing agent, stabilizer, and morphology control agent. The morphology, structure, and composition of the obtained catalysts were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). It was found that the catalysts synthesized by the co-reduction method possess a nanodendritic structure, while those prepared by successive reduction exhibit a hollow structure. Cyclic voltammetry and chronoamperometry investigations revealed that the PtPd/G catalyst with a hollow structure displayed the best anti-CO poisoning properties. In contrast, the catalyst with a dendritic structure that had been prepared at 100℃ showed the highest electrocatalytic performance towards methanol oxidation, which was 1.5 times that of the commercial Pt/C electrocatalyst.
This work describes the preparation of three kinds of PtPd/graphene (PtPd/G) nanocatalysts. Graphene oxide was first prepared as the carrier precursor by the Hummers method, and subsequently, the simultaneous reduction of graphene oxide and the metal precursor led to the in situ loading of PtPd on graphene. The fabrication procedure involving liquid phase co-reduction and successive reduction methods utilized the block copolymer P123 as a reducing agent, stabilizer, and morphology control agent. The morphology, structure, and composition of the obtained catalysts were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). It was found that the catalysts synthesized by the co-reduction method possess a nanodendritic structure, while those prepared by successive reduction exhibit a hollow structure. Cyclic voltammetry and chronoamperometry investigations revealed that the PtPd/G catalyst with a hollow structure displayed the best anti-CO poisoning properties. In contrast, the catalyst with a dendritic structure that had been prepared at 100℃ showed the highest electrocatalytic performance towards methanol oxidation, which was 1.5 times that of the commercial Pt/C electrocatalyst.
2017, 33(8): 1635-1643
doi: 10.3866/PKU.WHXB201704244
Abstract:
In this study, two novel difluorobenzothiadiazole (DFBT)-based polymeric donors, poly[(5,6-difluoro-benzo[c][1,2,5]thiadiazol-4,7-yl)-alt-((E)-2,3-bis(3'-(2-octyldodecyl)-(2,2'-bithiophen)-5,5'-yl) acrylonitrile)] (DFBT812) and poly[(5,6-difluoro-benzo[c][1,2,5]thiadiazol-4,7-yl)-alt-((E)-2,3-bis(3'-(2-decyltetradecyl)-(2,2'-bithiophen)-5,5'-yl) acrylonitrile)] (DFBT1014), possessing 2-octyldodecyl and 2-decyltetradecyl side chains, respectively, were designed, synthesized, and applied for polymer solar cells. Alkyl chains of 2-octyldodecyl and 2-decyltetradecyl were incorporated into the polymer to tune the solubility and crystallization of the polymers and morphology of the blend films. Morphological study showed that the blend film of DFBT812 with PC61BM presented much better phase separation domain, which is beneficial for charge transport and collection of charge carriers in the blend film. Photovoltaic devices based on DFBT812 exhibited a power conversion efficiency (PCE) of 6.25%, outperforming those based on DFBT1014. Moreover, DFBT812-based photovoltaic devices exhibited a PCE over 6% even when the thickness of the active layer was 220 nm.
In this study, two novel difluorobenzothiadiazole (DFBT)-based polymeric donors, poly[(5,6-difluoro-benzo[c][1,2,5]thiadiazol-4,7-yl)-alt-((E)-2,3-bis(3'-(2-octyldodecyl)-(2,2'-bithiophen)-5,5'-yl) acrylonitrile)] (DFBT812) and poly[(5,6-difluoro-benzo[c][1,2,5]thiadiazol-4,7-yl)-alt-((E)-2,3-bis(3'-(2-decyltetradecyl)-(2,2'-bithiophen)-5,5'-yl) acrylonitrile)] (DFBT1014), possessing 2-octyldodecyl and 2-decyltetradecyl side chains, respectively, were designed, synthesized, and applied for polymer solar cells. Alkyl chains of 2-octyldodecyl and 2-decyltetradecyl were incorporated into the polymer to tune the solubility and crystallization of the polymers and morphology of the blend films. Morphological study showed that the blend film of DFBT812 with PC61BM presented much better phase separation domain, which is beneficial for charge transport and collection of charge carriers in the blend film. Photovoltaic devices based on DFBT812 exhibited a power conversion efficiency (PCE) of 6.25%, outperforming those based on DFBT1014. Moreover, DFBT812-based photovoltaic devices exhibited a PCE over 6% even when the thickness of the active layer was 220 nm.
2017, 33(8): 1644-1654
doi: 10.3866/PKU.WHXB201704272
Abstract:
Nanostructured surfaces similar to those found in nasturtium leaf waxes were prepared by organic vapor deposition on a silicon wafer, with a range of crystal densities. The nanostructured surface consisting of 200 nm thick nonacosane showed the lowest adhesion. Bionic shark skin-like surfaces with different heights were prepared by reactive ion etching. Surfaces with a hierarchical structure were prepared by organic vapor deposition on the bionic shark skin with a thickness of 200 nm. 3,4-dihydroxyphenylalanine (DOPA) showed lower adhesion on the hierarchical structures as compared to the nanostructured surfaces, indicating that the surfaces with a hierarchical structure were strongly anti-adhesive and hydrophobic, with excellent resistance to water adhesion.
Nanostructured surfaces similar to those found in nasturtium leaf waxes were prepared by organic vapor deposition on a silicon wafer, with a range of crystal densities. The nanostructured surface consisting of 200 nm thick nonacosane showed the lowest adhesion. Bionic shark skin-like surfaces with different heights were prepared by reactive ion etching. Surfaces with a hierarchical structure were prepared by organic vapor deposition on the bionic shark skin with a thickness of 200 nm. 3,4-dihydroxyphenylalanine (DOPA) showed lower adhesion on the hierarchical structures as compared to the nanostructured surfaces, indicating that the surfaces with a hierarchical structure were strongly anti-adhesive and hydrophobic, with excellent resistance to water adhesion.
2017, 33(8): 1655-1664
doi: 10.3866/PKU.WHXB201704193
Abstract:
This report details the synthesis of a series of special magnetic cationic surfactants that contained two asymmetric alkyl chains, cetylpentyldimethylammonium trichloromonobromoferrate (C16C5DMA+[FeCl3Br]-). The fabrication of magnetic, adhesive, poly-morphological bilayer vesicle gels with unpredictable curvature and high flexibility was investigated in detail. These colloidal bilayer nano-transformers self-adhered to form a string; they also exhibited transformable morphologies that were investigated using cryo-transmission electron microspcopy (TEM), freezing-fracture transmission electron microscopy (FF-TEM), rheological analysis, Fourier transform infrared spectrometry (FT-IR), and superconducting quantum interference device (SQUID) techniques. Significantly, the deformed vesicles cohered to the gibbous bilayer protrusions, which closely resembled the pseudopodia of Proteus. These bilayer nano-transformers were capable of imitating structures and outlines of the natural world that, through human imagination, ranged from the island of Sicily in Italy to the larva of the Clanis bilineata and the common peanut. Most of the bilayer nano-transformers were endowed with unpredictable multi-curvature and high flexibility. A mechanism for the interlocking of the long and short alkyl chains in a bilayer arrangement was proposed in this study. The short chains departed from the bilayer to protrude externally; then, they associated non-covalently into inter-vesicular patches because of their hydrophobic interactions. Consequently, the hydrophobic inter-vesicular patches could supersede the repulsion between the vesicle membranes and allowed the vesicles to cohere. Of equal importance was that the anions[FeCl3Br]- could not only impart magnetism to the transformable vesicles, but could also tune the organization through the arrangements of the alkyl chains during the assembly process. Thus, the poly-morphology, adhesiveness, and curvature protrusions of this astounding colloidal "proteus" are eminently exploitable. This not only revealed the rudimentary regulatory mechanism of the membrane curvature, but also provided clues for the advancement of artificial cell fabrication.
This report details the synthesis of a series of special magnetic cationic surfactants that contained two asymmetric alkyl chains, cetylpentyldimethylammonium trichloromonobromoferrate (C16C5DMA+[FeCl3Br]-). The fabrication of magnetic, adhesive, poly-morphological bilayer vesicle gels with unpredictable curvature and high flexibility was investigated in detail. These colloidal bilayer nano-transformers self-adhered to form a string; they also exhibited transformable morphologies that were investigated using cryo-transmission electron microspcopy (TEM), freezing-fracture transmission electron microscopy (FF-TEM), rheological analysis, Fourier transform infrared spectrometry (FT-IR), and superconducting quantum interference device (SQUID) techniques. Significantly, the deformed vesicles cohered to the gibbous bilayer protrusions, which closely resembled the pseudopodia of Proteus. These bilayer nano-transformers were capable of imitating structures and outlines of the natural world that, through human imagination, ranged from the island of Sicily in Italy to the larva of the Clanis bilineata and the common peanut. Most of the bilayer nano-transformers were endowed with unpredictable multi-curvature and high flexibility. A mechanism for the interlocking of the long and short alkyl chains in a bilayer arrangement was proposed in this study. The short chains departed from the bilayer to protrude externally; then, they associated non-covalently into inter-vesicular patches because of their hydrophobic interactions. Consequently, the hydrophobic inter-vesicular patches could supersede the repulsion between the vesicle membranes and allowed the vesicles to cohere. Of equal importance was that the anions[FeCl3Br]- could not only impart magnetism to the transformable vesicles, but could also tune the organization through the arrangements of the alkyl chains during the assembly process. Thus, the poly-morphology, adhesiveness, and curvature protrusions of this astounding colloidal "proteus" are eminently exploitable. This not only revealed the rudimentary regulatory mechanism of the membrane curvature, but also provided clues for the advancement of artificial cell fabrication.
2017, 33(8): 1665-1671
doi: 10.3866/PKU.WHXB201704211
Abstract:
Herein, viscosity reduction is achieved for four different kinds of heavy oil based on the "generalized" cationic/anionic surfactants dodecanoic acid and dodecylamine. Two methods are employed in this work to reduce the oil viscosity of the oil. The first involves emulsifying the common heavy oil with an aqueous solution of "generalized" cationic/anionic surfactants, which can lead to an oil-in-water emulsion. The other requires dispersing the heavy oil in a mineral oil solution of "generalized" cationic/anionic surfactants. 95%-95% reduction is achieved for all heavy oils investigated thus treated.
Herein, viscosity reduction is achieved for four different kinds of heavy oil based on the "generalized" cationic/anionic surfactants dodecanoic acid and dodecylamine. Two methods are employed in this work to reduce the oil viscosity of the oil. The first involves emulsifying the common heavy oil with an aqueous solution of "generalized" cationic/anionic surfactants, which can lead to an oil-in-water emulsion. The other requires dispersing the heavy oil in a mineral oil solution of "generalized" cationic/anionic surfactants. 95%-95% reduction is achieved for all heavy oils investigated thus treated.
2017, 33(8): 1672-1680
doi: 10.3866/PKU.WHXB201704143
Abstract:
A series of Cu/Co/Mn/Al catalysts derived from hydrotalcite precursors with different Cu/Co molar ratios (0, 0.1, 0.5, 1.0, and 2.0) were prepared and used for the synthesis of higher alcohols from syngas. N2 physical adsorption desorption, inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD), scanning electron microscopy (SEM), hydrogen temperature-programmed reduction (H2-TPR), thermogravimetry (TG), and high-resolution transmission electron microscopy (HRTEM) techniques were employed to investigate the physical and chemical properties of the Cu/Co/Mn/Al catalysts. The results show that the optimum Cu content can increase specific surface area, improve reducibility, and form regular layered structure to provide more uniform distribution of active sites, thereby enhancing catalytic activity and alcohol selectivity. When the Cu/Co molar ratio was 0.5, the yield of alcohol and the alcohol selectivity reached the maximum values of 0.071 g·g-1·h-1 and 35.9%, respectively.
A series of Cu/Co/Mn/Al catalysts derived from hydrotalcite precursors with different Cu/Co molar ratios (0, 0.1, 0.5, 1.0, and 2.0) were prepared and used for the synthesis of higher alcohols from syngas. N2 physical adsorption desorption, inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD), scanning electron microscopy (SEM), hydrogen temperature-programmed reduction (H2-TPR), thermogravimetry (TG), and high-resolution transmission electron microscopy (HRTEM) techniques were employed to investigate the physical and chemical properties of the Cu/Co/Mn/Al catalysts. The results show that the optimum Cu content can increase specific surface area, improve reducibility, and form regular layered structure to provide more uniform distribution of active sites, thereby enhancing catalytic activity and alcohol selectivity. When the Cu/Co molar ratio was 0.5, the yield of alcohol and the alcohol selectivity reached the maximum values of 0.071 g·g-1·h-1 and 35.9%, respectively.
2017, 33(8): 1681-1688
doi: 10.3866/PKU.WHXB201704192
Abstract:
1% (w)Pd/γ-Al2O3 catalysts were prepared by the impregnation method using nano γ-Al2O3 (10 nm) and γ-Al2O3 (200-300 nm) as support materials. The catalysts were tested for catalytic oxidation of o-xylene and the difference of catalyst activity before and after hydrogen reduction was investigated. The results indicate that 1% (w)Pd/γ-Al2O3 (nano) has the highest catalytic activity for o-xylene oxidation after H2 reduction, and the T90 (The temperature of conversion rate of o-xylene reaches 90%) was 150℃. The structure-activity relationships of the catalysts were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), while the specific surface area was determined using the Brunauer-Emmett-Teller (BET) isotherm. The results show that the reduced Pd is the active species for catalytic oxidation of o-xylene. Pd particle size has a significant influence on the catalyst activity and a small Pd particle size is favorable. There is a strong interaction between the supporter (nano γ-Al2O3) and the Pd species, which facilitates the particle size control and Pd dispersion, thereby increasing the catalyst activity of the 1% (w)Pd/γ-Al2O3(nano) catalyst.
1% (w)Pd/γ-Al2O3 catalysts were prepared by the impregnation method using nano γ-Al2O3 (10 nm) and γ-Al2O3 (200-300 nm) as support materials. The catalysts were tested for catalytic oxidation of o-xylene and the difference of catalyst activity before and after hydrogen reduction was investigated. The results indicate that 1% (w)Pd/γ-Al2O3 (nano) has the highest catalytic activity for o-xylene oxidation after H2 reduction, and the T90 (The temperature of conversion rate of o-xylene reaches 90%) was 150℃. The structure-activity relationships of the catalysts were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), while the specific surface area was determined using the Brunauer-Emmett-Teller (BET) isotherm. The results show that the reduced Pd is the active species for catalytic oxidation of o-xylene. Pd particle size has a significant influence on the catalyst activity and a small Pd particle size is favorable. There is a strong interaction between the supporter (nano γ-Al2O3) and the Pd species, which facilitates the particle size control and Pd dispersion, thereby increasing the catalyst activity of the 1% (w)Pd/γ-Al2O3(nano) catalyst.
2017, 33(8): 1689-1698
doi: 10.3866/PKU.WHXB201704243
Abstract:
Rh/SiO2 and Rh-Sm2O3/SiO2 catalysts were synthesized by the conventional impregnation method using rhodium acetylacetonate (Rh(acac)3) and samarium acetylacetonate (Sm(acac)3) as precursors. The preparation and catalytic properties, as well as the interaction between Rh and Sm2O3, were characterized in detail by in situ infrared spectroscopy (IR), thermogravimetric analysis (TG), N2 physisorption (Brunauer-Emmett-Teller (BET) method), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The performance of the catalysts for the partial oxidation of methane (POM) to syngas was also investigated. The results showed that a sinter-resistant Rh-Sm2O3/SiO2 catalyst with an average Rh particle size of ~2.3 nm could be synthesized using the conventional impregnation method with Rh(acac)3 and Sm(acac)3 as precursors. The surface silanol groups of SiO2 acted as the centers to interact with M(acac)3 (M=Rh, Sm) molecules when SiO2 was impregnated in the M(acac)3 solution, leading to the formation of a hydrogen-bonded M(acac)3 layer on the SiO2 surface. In this experiment, the monolayer coverage of Sm(acac)3 on the SiO2 surface was equal to a Sm(acac)3 loading (mass fraction) of approximately 31%, which in turn corresponded to a Sm2O3 loading of approximately 15%. When a Sm(acac)3/SiO2 sample with Sm(acac)3 loading below 31% was heated in air to approximately 360℃, the monolayer Sm(acac)3 species decomposed into highly dispersed Sm2O3 species on the SiO2 surface, which displayed superior stability against sintering at high temperature. No aggregation of the Sm2O3 species was observed even when the sample was heated to 800℃ in air. The strong interaction between the highly dispersed Sm2O3 and Rh plays a key role in increasing the dispersion of Rh species in the catalyst and preventing the Rh species from sintering under high temperature conditions. This factor should also be responsible for the superior activity and stability of the Rh-Sm2O3/SiO2 catalyst with extremely low Rh loading for the catalytic partial oxidation of methane to syngas.
Rh/SiO2 and Rh-Sm2O3/SiO2 catalysts were synthesized by the conventional impregnation method using rhodium acetylacetonate (Rh(acac)3) and samarium acetylacetonate (Sm(acac)3) as precursors. The preparation and catalytic properties, as well as the interaction between Rh and Sm2O3, were characterized in detail by in situ infrared spectroscopy (IR), thermogravimetric analysis (TG), N2 physisorption (Brunauer-Emmett-Teller (BET) method), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The performance of the catalysts for the partial oxidation of methane (POM) to syngas was also investigated. The results showed that a sinter-resistant Rh-Sm2O3/SiO2 catalyst with an average Rh particle size of ~2.3 nm could be synthesized using the conventional impregnation method with Rh(acac)3 and Sm(acac)3 as precursors. The surface silanol groups of SiO2 acted as the centers to interact with M(acac)3 (M=Rh, Sm) molecules when SiO2 was impregnated in the M(acac)3 solution, leading to the formation of a hydrogen-bonded M(acac)3 layer on the SiO2 surface. In this experiment, the monolayer coverage of Sm(acac)3 on the SiO2 surface was equal to a Sm(acac)3 loading (mass fraction) of approximately 31%, which in turn corresponded to a Sm2O3 loading of approximately 15%. When a Sm(acac)3/SiO2 sample with Sm(acac)3 loading below 31% was heated in air to approximately 360℃, the monolayer Sm(acac)3 species decomposed into highly dispersed Sm2O3 species on the SiO2 surface, which displayed superior stability against sintering at high temperature. No aggregation of the Sm2O3 species was observed even when the sample was heated to 800℃ in air. The strong interaction between the highly dispersed Sm2O3 and Rh plays a key role in increasing the dispersion of Rh species in the catalyst and preventing the Rh species from sintering under high temperature conditions. This factor should also be responsible for the superior activity and stability of the Rh-Sm2O3/SiO2 catalyst with extremely low Rh loading for the catalytic partial oxidation of methane to syngas.
2017, 33(8): 1709-1714
doi: 10.3866/PKU.WHXB201704171
Abstract:
Alkyl dinitrites with two functional groups, R2C(ONO)(CH2)nC(ONO)R2, can easily produce alkoxy radicals and nitric oxide in the atmosphere. Their high activity has led to issues such as photochemical air pollution and the greenhouse effect. Hence, unraveling the decomposition mechanism of alkyl dinitrites is of great significance in understanding their photochemical and thermochemical roles in the atmosphere. In this work, the dissociation process of six alkyl dinitrites was investigated by mass spectrometry under the electron impact energy of 70 eV. Our results indicated that the ruptured fragments had characteristic directivity for the structures of alkyl dinitrites. We detected not only the NO+ fragment ion, due to the common breakage of O-NO bond, but also R2C(ONO)+ resulting from the breakage of α C-C bond in the electron ionization mass spectra. The dissociation mechanism of alkyl dinitrites in which the O-NO or C-C bond directly dissociates is different from photolysis and pyrolysis.
Alkyl dinitrites with two functional groups, R2C(ONO)(CH2)nC(ONO)R2, can easily produce alkoxy radicals and nitric oxide in the atmosphere. Their high activity has led to issues such as photochemical air pollution and the greenhouse effect. Hence, unraveling the decomposition mechanism of alkyl dinitrites is of great significance in understanding their photochemical and thermochemical roles in the atmosphere. In this work, the dissociation process of six alkyl dinitrites was investigated by mass spectrometry under the electron impact energy of 70 eV. Our results indicated that the ruptured fragments had characteristic directivity for the structures of alkyl dinitrites. We detected not only the NO+ fragment ion, due to the common breakage of O-NO bond, but also R2C(ONO)+ resulting from the breakage of α C-C bond in the electron ionization mass spectra. The dissociation mechanism of alkyl dinitrites in which the O-NO or C-C bond directly dissociates is different from photolysis and pyrolysis.
2017, 33(8): 1715-1720
doi: 10.3866/PKU.WHXB201704174
Abstract:
To reduce the density of the absorbent Co3Fe7, a core-shell Co3Fe7@C microwave absorbent was synthesized by preparing an iron/cobalt-containing carbon precursor followed by high-temperature carbonization. According to the X-ray diffraction (XRD) and transmission electron microscopy (TEM) results, Co3Fe7 particles were coated with graphitized carbon layers to form a core-shell structure. Furthermore, the Co3Fe7@C composite with a surface area and density of 358.5 m2·g-1 and 2.25 g·cm-3, respectively, exhibited excellent microwave absorbability. A minimum reflection loss (RL) of -43.5 dB and an effective bandwidth (RL below -10 dB) of 4.1 GHz were obtained at the coating thickness of 2 mm, which could be mainly attributed to the effective impedance match and multiple interfacial polarizations. Owing to the low density and remarkable microwave absorption, we believe that the Co3Fe7@C composite can be a promising candidate for use as a lightweight and efficient microwave absorbent.
To reduce the density of the absorbent Co3Fe7, a core-shell Co3Fe7@C microwave absorbent was synthesized by preparing an iron/cobalt-containing carbon precursor followed by high-temperature carbonization. According to the X-ray diffraction (XRD) and transmission electron microscopy (TEM) results, Co3Fe7 particles were coated with graphitized carbon layers to form a core-shell structure. Furthermore, the Co3Fe7@C composite with a surface area and density of 358.5 m2·g-1 and 2.25 g·cm-3, respectively, exhibited excellent microwave absorbability. A minimum reflection loss (RL) of -43.5 dB and an effective bandwidth (RL below -10 dB) of 4.1 GHz were obtained at the coating thickness of 2 mm, which could be mainly attributed to the effective impedance match and multiple interfacial polarizations. Owing to the low density and remarkable microwave absorption, we believe that the Co3Fe7@C composite can be a promising candidate for use as a lightweight and efficient microwave absorbent.
