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2017 Volume 33 Issue 1
2017, 33(1):
Abstract:
2017, 33(1): 1-2
doi: 10.3866/PKU.WHXB201612071
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2017, 33(1): 3-4
doi: 10.3866/PKU.WHXB201612161
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2017, 33(1): 5-6
doi: 10.3866/PKU.WHXB201612151
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2017, 33(1): 7-7
doi: 10.3866/PKU.WHXB201612121
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2017, 33(1): 8-8
doi: 10.3866/PKU.WHXB201612163
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2017, 33(1): 9-17
doi: 10.3866/PKU.WHXB201609202
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The high cost of platinum in catalyst layers hinders the commercialization of proton exchange membrane fuel cells. This Account reviews recent progress on core-shell nanostructures for oxygen reduction reaction (ORR) in acidic media, which is the cathodic reaction in fuel cells. The synthesis, characterization and evaluation of different types of core-shell electrocatalysts are summarized. Various strategies to improve the performance of core-shell electrocatalysts, including dealloying, morphology control, and surface modification are presented. The issues of mass production and fuel cell performance of core-shell electrocatalysts are also discussed.
The high cost of platinum in catalyst layers hinders the commercialization of proton exchange membrane fuel cells. This Account reviews recent progress on core-shell nanostructures for oxygen reduction reaction (ORR) in acidic media, which is the cathodic reaction in fuel cells. The synthesis, characterization and evaluation of different types of core-shell electrocatalysts are summarized. Various strategies to improve the performance of core-shell electrocatalysts, including dealloying, morphology control, and surface modification are presented. The issues of mass production and fuel cell performance of core-shell electrocatalysts are also discussed.
2017, 33(1): 18-27
doi: 10.3866/PKU.WHXB201609214
Abstract:
Micro-energy storage devices are suitable for use in a range of potential applications, such as wearable electronics and micro-self-powered sensors, and also provide an ideal platform to explore the inner relationship among the electrode structure, electron/ion conductivity and electrochemical kinetics. Self-roll-up technology is an approach to rearrange automatically two-dimensional membrane materials because of residual stress. Compared with the conventional micro-nano fabrication technique, the self-roll-up technology realizes the ordered array of two-dimensional membranes, offering an effective and convenient way to fabricate microenergy storage devices. In this article, we review the recent important progresses of the self-roll-up technology for micro-energy storage devices, including the theory of the self-roll-up technology, and self-roll-up electrodes and their energy storage properties. Importantly, we highlight the practical applications of the self-roll-up technology for fabrication of single tubular micro lithium-ion batteries and capacitor arrays. Finally, future challenges and important opportunities of the self-roll-up technology for micro-energy storage devices are summarized and prospected.
Micro-energy storage devices are suitable for use in a range of potential applications, such as wearable electronics and micro-self-powered sensors, and also provide an ideal platform to explore the inner relationship among the electrode structure, electron/ion conductivity and electrochemical kinetics. Self-roll-up technology is an approach to rearrange automatically two-dimensional membrane materials because of residual stress. Compared with the conventional micro-nano fabrication technique, the self-roll-up technology realizes the ordered array of two-dimensional membranes, offering an effective and convenient way to fabricate microenergy storage devices. In this article, we review the recent important progresses of the self-roll-up technology for micro-energy storage devices, including the theory of the self-roll-up technology, and self-roll-up electrodes and their energy storage properties. Importantly, we highlight the practical applications of the self-roll-up technology for fabrication of single tubular micro lithium-ion batteries and capacitor arrays. Finally, future challenges and important opportunities of the self-roll-up technology for micro-energy storage devices are summarized and prospected.
2017, 33(1): 28-39
doi: 10.3866/PKU.WHXB201609213
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Graphitic nanomaterials, which possess unique optical properties, have attracted significant attention in biochemical sensing. Herein, we summarize and discuss recent progress of such materials as optical probes, photothermal materials and signal transduction substrates for biosensing applications. The most attractive optical property of graphitic nanomaterials is their strong and unique Raman signals. As a Raman probe, these nanomaterials have remarkable applications, especially in detecting complex biological samples, quantitative surface enhanced Raman scattering (SERS) detection and detection under extreme conditions. Besides Raman, the unique intrinsic fluorescence emission of single-walled carbon nanotubes (SWNTs) in the long wavelength and second near-infrared window (NIR-II window, 1000-1700 nm) has facilitated deep-tissue high-resolution fluorescence imaging in vivo. Additionally, graphitic nanomaterials have efficient photothermal conversion capability. Together with the large surface area, graphitic nanomaterials are used in photothermal synergy therapy for cancer treatment. Furthermore, because of their particular physical and chemical properties, graphitic nanomaterials are established as an efficient signal transduction substrate, which can quench an excited chromophore and photosensitizer, showing high selectivity and sensitivity in biosensing and nanomedicine.
Graphitic nanomaterials, which possess unique optical properties, have attracted significant attention in biochemical sensing. Herein, we summarize and discuss recent progress of such materials as optical probes, photothermal materials and signal transduction substrates for biosensing applications. The most attractive optical property of graphitic nanomaterials is their strong and unique Raman signals. As a Raman probe, these nanomaterials have remarkable applications, especially in detecting complex biological samples, quantitative surface enhanced Raman scattering (SERS) detection and detection under extreme conditions. Besides Raman, the unique intrinsic fluorescence emission of single-walled carbon nanotubes (SWNTs) in the long wavelength and second near-infrared window (NIR-II window, 1000-1700 nm) has facilitated deep-tissue high-resolution fluorescence imaging in vivo. Additionally, graphitic nanomaterials have efficient photothermal conversion capability. Together with the large surface area, graphitic nanomaterials are used in photothermal synergy therapy for cancer treatment. Furthermore, because of their particular physical and chemical properties, graphitic nanomaterials are established as an efficient signal transduction substrate, which can quench an excited chromophore and photosensitizer, showing high selectivity and sensitivity in biosensing and nanomedicine.
2017, 33(1): 40-62
doi: 10.3866/PKU.WHXB201609192
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In recent years, ultrafast multiple-dimensional vibrational spectroscopy has been widely applied to studies of molecular structures and ultrafast dynamics in various condensed phases, and is expected to become a new generation of routine analytical tool for determining microstructures and ultrafast behaviors in molecular systems. In this review, we introduce in detail a method of determining three-dimensional (3D) molecular conformations with ultrafast multiple-dimensional vibrational spectroscopy. The introduction of our research follows two directions:(1) obtaining relative spatial orientations of different groups in a molecular system and finally determining molecular conformations by measuring cross angles of vibrational transition dipole moments; and (2) exploring the nature of vibrational energy transfers and determining molecular distances with experimentally measured vibrational energy transfer rates.
In recent years, ultrafast multiple-dimensional vibrational spectroscopy has been widely applied to studies of molecular structures and ultrafast dynamics in various condensed phases, and is expected to become a new generation of routine analytical tool for determining microstructures and ultrafast behaviors in molecular systems. In this review, we introduce in detail a method of determining three-dimensional (3D) molecular conformations with ultrafast multiple-dimensional vibrational spectroscopy. The introduction of our research follows two directions:(1) obtaining relative spatial orientations of different groups in a molecular system and finally determining molecular conformations by measuring cross angles of vibrational transition dipole moments; and (2) exploring the nature of vibrational energy transfers and determining molecular distances with experimentally measured vibrational energy transfer rates.
2017, 33(1): 63-79
doi: 10.3866/PKU.WHXB201608233
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Nanomaterials have excellent properties and have been used widely in chemical engineering, electronics, mechanics, environment, energy, aerospace, and many other fields in recent years. Besides, nanomaterials have attracted increasing attention in the biomedical field. The interactions between nanomaterials and protein molecules are not only significant to the basic science of the biomedical field, but also crucial for the evaluation of biomedical applications and biosafety of nanomaterials. The interfacial interactions between proteins and nanomaterials could induce a series of changes to the structures and functions of proteins, such as the transformation of protein conformations, and the modulation of aggregation states, which would influence the functions of the protein molecules. Interfacial interactions can also influence the physicochemical features of nanomaterials, including morphology, size, hydrophilicity/hydrophobicity, and surface charge density. In this review we explained the molecular level mechanisms for the interactions between nanomaterials and proteins at the interface based on the detection technologies, and discussed the changes in physical and chemical features, structures, and functions. We envision this review could be helpful for the deeper understanding of the complicated interactions between nanomaterials and proteins, and could be beneficial for promoting the healthy, safe, and sustainable development and application of nanomaterials in the biological and medical fields.
Nanomaterials have excellent properties and have been used widely in chemical engineering, electronics, mechanics, environment, energy, aerospace, and many other fields in recent years. Besides, nanomaterials have attracted increasing attention in the biomedical field. The interactions between nanomaterials and protein molecules are not only significant to the basic science of the biomedical field, but also crucial for the evaluation of biomedical applications and biosafety of nanomaterials. The interfacial interactions between proteins and nanomaterials could induce a series of changes to the structures and functions of proteins, such as the transformation of protein conformations, and the modulation of aggregation states, which would influence the functions of the protein molecules. Interfacial interactions can also influence the physicochemical features of nanomaterials, including morphology, size, hydrophilicity/hydrophobicity, and surface charge density. In this review we explained the molecular level mechanisms for the interactions between nanomaterials and proteins at the interface based on the detection technologies, and discussed the changes in physical and chemical features, structures, and functions. We envision this review could be helpful for the deeper understanding of the complicated interactions between nanomaterials and proteins, and could be beneficial for promoting the healthy, safe, and sustainable development and application of nanomaterials in the biological and medical fields.
2017, 33(1): 80-102
doi: 10.3866/PKU.WHXB201607293
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Photoelectrochemical water splitting is to utilize collected photo-generated carrier for direct water cleavage for hydrogen production. It is a system combining photoconversion and energy storage since converted solar energy is stored as high energy-density hydrogen gas. According to intrinsic properties and band bending situation of a photoelectrode, hydrogen tends to be released at photocathode while oxygen at photoanode. In a tandem photoelectrochemical chemical cell, current passing through one electrode must equals that through another and electrode with lower conversion rate will limit efficiency of the whole device. Therefore, it is also of research interest to look into the common strategies for enhancing the conversion rate at photoanode. Although up to 15% of solar-to-hydrogen efficiency can be estimated according to some semiconductor for solar assisted water splitting, practical conversion ability of state-of-the-art photoanode has yet to approach that theoretical limit. Five major steps happen in a full water splitting reaction at a semiconductor surface:light harvesting with electron excitations, separated electron-hole pairs transferring to two opposite ends due to band bending, electron/hole injection through semiconductor-electrolyte interface into water, recombination process and mass transfer of products/reactants. They are closely related to different proposed parameters for solar water splitting evaluation and this review will first help to give a fast glance at those evaluation parameters and then summarize on several major adopted strategies towards high-efficiency oxygen evolution at photoanode surface. Those strategies and thereby optimized evaluation parameter are shown, in order to disclose the importance of modifying different steps for a photoanode with enhanced output.
Photoelectrochemical water splitting is to utilize collected photo-generated carrier for direct water cleavage for hydrogen production. It is a system combining photoconversion and energy storage since converted solar energy is stored as high energy-density hydrogen gas. According to intrinsic properties and band bending situation of a photoelectrode, hydrogen tends to be released at photocathode while oxygen at photoanode. In a tandem photoelectrochemical chemical cell, current passing through one electrode must equals that through another and electrode with lower conversion rate will limit efficiency of the whole device. Therefore, it is also of research interest to look into the common strategies for enhancing the conversion rate at photoanode. Although up to 15% of solar-to-hydrogen efficiency can be estimated according to some semiconductor for solar assisted water splitting, practical conversion ability of state-of-the-art photoanode has yet to approach that theoretical limit. Five major steps happen in a full water splitting reaction at a semiconductor surface:light harvesting with electron excitations, separated electron-hole pairs transferring to two opposite ends due to band bending, electron/hole injection through semiconductor-electrolyte interface into water, recombination process and mass transfer of products/reactants. They are closely related to different proposed parameters for solar water splitting evaluation and this review will first help to give a fast glance at those evaluation parameters and then summarize on several major adopted strategies towards high-efficiency oxygen evolution at photoanode surface. Those strategies and thereby optimized evaluation parameter are shown, in order to disclose the importance of modifying different steps for a photoanode with enhanced output.
2017, 33(1): 103-129
doi: 10.3866/PKU.WHXB201608303
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Lithium ion batteries (LiBs) have been widely utilized, but the limited lithium resource restricts development and application of LiBs in large-scale energy storage. Sodium has similar physicochemical characteristics to that of lithium and is suitable to transfer between two electrodes as a cation in the "rocking chair" mechanism of LiBs. Na-containing compounds have been proposed as the electrodes to store sodium ions and provide channels for diffusion. Polyanion Na3V2(PO4)3 is a Na-super-ionic conductor (NASICON) with specific Na sites in its crystal structure and three-dimensional open channels. Recently, Na3V2(PO4)3 has been demonstrated as potential electrode material with promising properties for energy storage. In this review we systematically summarize the structure of Na3V2(PO4)3, the application and mechanism in a specific energy system, and the recent development of Na3V2(PO4)3 structure for use as electrodes. The potential problems and trends of Na3V2(PO4)3 are also discussed.
Lithium ion batteries (LiBs) have been widely utilized, but the limited lithium resource restricts development and application of LiBs in large-scale energy storage. Sodium has similar physicochemical characteristics to that of lithium and is suitable to transfer between two electrodes as a cation in the "rocking chair" mechanism of LiBs. Na-containing compounds have been proposed as the electrodes to store sodium ions and provide channels for diffusion. Polyanion Na3V2(PO4)3 is a Na-super-ionic conductor (NASICON) with specific Na sites in its crystal structure and three-dimensional open channels. Recently, Na3V2(PO4)3 has been demonstrated as potential electrode material with promising properties for energy storage. In this review we systematically summarize the structure of Na3V2(PO4)3, the application and mechanism in a specific energy system, and the recent development of Na3V2(PO4)3 structure for use as electrodes. The potential problems and trends of Na3V2(PO4)3 are also discussed.
2017, 33(1): 130-148
doi: 10.3866/PKU.WHXB201609012
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As a new type of energy storage device, supercapacitors with high specific capacitance, fast charge and discharge, and long cycle life have attracted significant attention in the energy storage field. Electrode materials are a crucial factor defining the electrochemical performance of supercapacitors. The standard supercapacitor electrode materials used can be classified into three types:carbon-based materials, metal oxides and hydroxide materials, and conductive polymers. This review introduces the principles of supercapacitors and summarizes recent research progress of carbon-based electrode materials, including pure carbon materials, and the binary and ternary complex materials with carbon.
As a new type of energy storage device, supercapacitors with high specific capacitance, fast charge and discharge, and long cycle life have attracted significant attention in the energy storage field. Electrode materials are a crucial factor defining the electrochemical performance of supercapacitors. The standard supercapacitor electrode materials used can be classified into three types:carbon-based materials, metal oxides and hydroxide materials, and conductive polymers. This review introduces the principles of supercapacitors and summarizes recent research progress of carbon-based electrode materials, including pure carbon materials, and the binary and ternary complex materials with carbon.
2017, 33(1): 149-164
doi: 10.3866/PKU.WHXB201609143
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Metal organic frameworks (MOFs) have attracted tremendous attention in electrochemical energy storage and conversion because of their large surface area, high porosity, ordered structure and the tailorability of the structure. In this paper, the unique advantages of synthesizing electrocatalysts from MOFs are introduced. Then, the latest research progress of MOFs derived electrocatalysts in electrochemical energy conversion is mainly summarized. Finally, the application prospects, opportunities and challenges of MOF-based materials are briefly presented to provide an outlook for future research directions.
Metal organic frameworks (MOFs) have attracted tremendous attention in electrochemical energy storage and conversion because of their large surface area, high porosity, ordered structure and the tailorability of the structure. In this paper, the unique advantages of synthesizing electrocatalysts from MOFs are introduced. Then, the latest research progress of MOFs derived electrocatalysts in electrochemical energy conversion is mainly summarized. Finally, the application prospects, opportunities and challenges of MOF-based materials are briefly presented to provide an outlook for future research directions.
2017, 33(1): 165-182
doi: 10.3866/PKU.WHXB201609232
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Chemically modified carbon has attracted significant attention since our first report of its use in lithium/sulfur (Li/S) cells. Compared with traditional carbon materials, chemically modified carbon prevents the dissolution and diffusion of intermediate polysulfides. Therefore, it yields sulfur cathodes with long cycling stability, which has become the focus of current research in the field of Li/S batteries. This review summarizes the use of chemically modified carbon for highly efficient sulfur utilization and the synergistic chemical/physical trapping of sulfur species. The prospects of further developments of Li/S batteries using chemically modified carbon is also discussed.
Chemically modified carbon has attracted significant attention since our first report of its use in lithium/sulfur (Li/S) cells. Compared with traditional carbon materials, chemically modified carbon prevents the dissolution and diffusion of intermediate polysulfides. Therefore, it yields sulfur cathodes with long cycling stability, which has become the focus of current research in the field of Li/S batteries. This review summarizes the use of chemically modified carbon for highly efficient sulfur utilization and the synergistic chemical/physical trapping of sulfur species. The prospects of further developments of Li/S batteries using chemically modified carbon is also discussed.
2017, 33(1): 183-197
doi: 10.3866/PKU.WHXB201609282
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Atomic force microscopy (AFM) is used to investigate surface structures by measuring the interaction force between the tip and sample. Non-contact AFM (NC-AFM) that incorporates a qPlus sensor further enhances the spatial resolution of scanning probe microscopy based on traditional AFM principles. In this perspective, we give a brief introduction to the mechanisms of high-resolution imaging and force measurements using NC-AFM. We then summarize recent applications of NC-AFM in the fields of on-surface chemical reactions, low-dimensional materials, surface charge distribution in molecules, as well as technical improvements and developments of NC-AFM technologies. The opportunities and challenges for NC-AFM technologies are also presented.
Atomic force microscopy (AFM) is used to investigate surface structures by measuring the interaction force between the tip and sample. Non-contact AFM (NC-AFM) that incorporates a qPlus sensor further enhances the spatial resolution of scanning probe microscopy based on traditional AFM principles. In this perspective, we give a brief introduction to the mechanisms of high-resolution imaging and force measurements using NC-AFM. We then summarize recent applications of NC-AFM in the fields of on-surface chemical reactions, low-dimensional materials, surface charge distribution in molecules, as well as technical improvements and developments of NC-AFM technologies. The opportunities and challenges for NC-AFM technologies are also presented.
2017, 33(1): 198-210
doi: 10.3866/PKU.WHXB201609191
Abstract:
Developing highly efficient electrode catalysts with the four-electron oxygen reduction pathway has remained a research hotspot in fuel cell research. However, the pursuit of novel electrode catalysts possessing the specific two-electron reduction route for water treatment is challenging. In this review, we focus on recent progress in electrocatalytic treatment of refractory pollutants in water by palladium (Pd)-based noble metal electrodes. We highlight:(i) the degradation and mineralization of organic pollutants through electrocatalytic oxidation derived from the combination of Fe2+ and H2O2, which can be in-situ synthesized by Pd based electrodes; (ii) electrocatalytic reduction transformation from toxic organic pollutants and inorganic salts to harmless products by Pd-based electrodes; and (iii) removal of heavy metals by redox conversion via Pd-based electrodes. The future opportunities and prospects of applying noble metal nanocatalysts in water treatment are discussed.
Developing highly efficient electrode catalysts with the four-electron oxygen reduction pathway has remained a research hotspot in fuel cell research. However, the pursuit of novel electrode catalysts possessing the specific two-electron reduction route for water treatment is challenging. In this review, we focus on recent progress in electrocatalytic treatment of refractory pollutants in water by palladium (Pd)-based noble metal electrodes. We highlight:(i) the degradation and mineralization of organic pollutants through electrocatalytic oxidation derived from the combination of Fe2+ and H2O2, which can be in-situ synthesized by Pd based electrodes; (ii) electrocatalytic reduction transformation from toxic organic pollutants and inorganic salts to harmless products by Pd-based electrodes; and (iii) removal of heavy metals by redox conversion via Pd-based electrodes. The future opportunities and prospects of applying noble metal nanocatalysts in water treatment are discussed.
2017, 33(1): 211-241
doi: 10.3866/PKU.WHXB201610111
Abstract:
Sodium ion batteries (SIBs) have attracted increasing attention for energy storage systems because of abundant and low cost sodium resources. However, the large ionic radius of sodium and its slow electrochemical kinetics are the main obstacles for the development of suitable electrodes for high-performance SIBs. The development of high-performance cathode materials is the key to improving the energy density of SIBs and facilitating their commercialization. Herein, we review the latest advances and progress of cathode materials for SIBs, including transition metal oxides, polyanions, ferrocyanides, organic materials and polymers, and amorphous materials. Additionally, we have summarized our previous works in this area, explore the relationship between structure and electrochemical performance, and discuss effective ways to improve the reversibility, working potential and structural stability of these cathode materials.
Sodium ion batteries (SIBs) have attracted increasing attention for energy storage systems because of abundant and low cost sodium resources. However, the large ionic radius of sodium and its slow electrochemical kinetics are the main obstacles for the development of suitable electrodes for high-performance SIBs. The development of high-performance cathode materials is the key to improving the energy density of SIBs and facilitating their commercialization. Herein, we review the latest advances and progress of cathode materials for SIBs, including transition metal oxides, polyanions, ferrocyanides, organic materials and polymers, and amorphous materials. Additionally, we have summarized our previous works in this area, explore the relationship between structure and electrochemical performance, and discuss effective ways to improve the reversibility, working potential and structural stability of these cathode materials.
2017, 33(1): 242-248
doi: 10.3866/PKU.WHXB201610103
Abstract:
Anovel four-fold interpenetrating metal-organic framework (MOF) (1) was obtained following reaction between Zn2+ and benzene-1,3,5-tribenzoate (H3BTB). Single crystal analysis demonstrated that the framework featured a three-dimensional (10, 3) net anionic framework with dimethyl formamide (DMF) and H2NMe2+ encapsulated in channels along the b axis. Alternating current impedance measurements revealed an unusual temperature-dependent conductance. As the temperature was increased from 20℃ the conductance value increased from 0.36×10-6 S·cm-1 to a maximum value of 2.24×10-5 S·cm-1 at 160℃, and then began to decrease. A combination of molecular dynamics (MD) simulations and dielectric property measurements demonstrated that this conductance behavior could be attributed to the synergic effect of the enhanced mobility of the H2NMe2+ cation and removal of DMF as the temperature was increased. Furthermore, the transporting energy barrier was determined to be 0.20 eV, which confirmed that the conductance was caused by proton conductivity. This work indicated that the confinement of H2NMe2+ within the pores of MOFs is a promising method to induce electrical conductivity. Interestingly, the emission peak of 1 was blue-shifted when compared with that of H3BTB. Density functional theory (DFT) calculations revealed that this phenomenon was caused by the disruption of delocalized π-bonds within the BTB3- ligand in 1.
Anovel four-fold interpenetrating metal-organic framework (MOF) (1) was obtained following reaction between Zn2+ and benzene-1,3,5-tribenzoate (H3BTB). Single crystal analysis demonstrated that the framework featured a three-dimensional (10, 3) net anionic framework with dimethyl formamide (DMF) and H2NMe2+ encapsulated in channels along the b axis. Alternating current impedance measurements revealed an unusual temperature-dependent conductance. As the temperature was increased from 20℃ the conductance value increased from 0.36×10-6 S·cm-1 to a maximum value of 2.24×10-5 S·cm-1 at 160℃, and then began to decrease. A combination of molecular dynamics (MD) simulations and dielectric property measurements demonstrated that this conductance behavior could be attributed to the synergic effect of the enhanced mobility of the H2NMe2+ cation and removal of DMF as the temperature was increased. Furthermore, the transporting energy barrier was determined to be 0.20 eV, which confirmed that the conductance was caused by proton conductivity. This work indicated that the confinement of H2NMe2+ within the pores of MOFs is a promising method to induce electrical conductivity. Interestingly, the emission peak of 1 was blue-shifted when compared with that of H3BTB. Density functional theory (DFT) calculations revealed that this phenomenon was caused by the disruption of delocalized π-bonds within the BTB3- ligand in 1.
2017, 33(1): 249-254
doi: 10.3866/PKU.WHXB201610142
Abstract:
Organic-inorganic hybrid perovskite methylammonium lead iodide (CH3NH3PbI3) generally tends to show n-type semiconductor properties. In this work, a field-effect transistor (FET) device based on a CH3NH3PbI3 single crystal with tantalum pentoxide (Ta2O5) as the top gate dielectric was fabricated. The p-type field-effect transport properties of the device were observed in the dark. The hole mobility of the device extracted from transfer characteristics in the dark was 8.7×10-5 cm2·V-1·s-1, which is one order of magnitude higher than that of polycrystalline FETs with SiO2 as the bottom gate dielectric. In addition, the effect of light illumination on the CH3NH3PbI3 single-crystal FET was studied. Light illumination strongly influenced the field effect of the device because of the intense photoelectric response of the CH3NH3PbI3 single crystal. Different from a CH3NH3PbI3 polycrystalline FET with a bottom gate dielectric, even with the top gate dielectric shielding, light illumination of 5.00 mW·cm-2 caused the hole current to increase by one order of magnitude compared with that in the dark (VGS (gate-source voltage)=VDS (drain-source voltage)=20 V) and the photoresponsivity reached 2.5 A·W-1. The introduction of Ta2O5 as the top gate dielectric selectively enhanced hole transport in the single-crystal FET, indicating that in the absence of external factors, by appropriate device design, CH3NH3PbI3 also has potential for use in ambipolar transistors.
Organic-inorganic hybrid perovskite methylammonium lead iodide (CH3NH3PbI3) generally tends to show n-type semiconductor properties. In this work, a field-effect transistor (FET) device based on a CH3NH3PbI3 single crystal with tantalum pentoxide (Ta2O5) as the top gate dielectric was fabricated. The p-type field-effect transport properties of the device were observed in the dark. The hole mobility of the device extracted from transfer characteristics in the dark was 8.7×10-5 cm2·V-1·s-1, which is one order of magnitude higher than that of polycrystalline FETs with SiO2 as the bottom gate dielectric. In addition, the effect of light illumination on the CH3NH3PbI3 single-crystal FET was studied. Light illumination strongly influenced the field effect of the device because of the intense photoelectric response of the CH3NH3PbI3 single crystal. Different from a CH3NH3PbI3 polycrystalline FET with a bottom gate dielectric, even with the top gate dielectric shielding, light illumination of 5.00 mW·cm-2 caused the hole current to increase by one order of magnitude compared with that in the dark (VGS (gate-source voltage)=VDS (drain-source voltage)=20 V) and the photoresponsivity reached 2.5 A·W-1. The introduction of Ta2O5 as the top gate dielectric selectively enhanced hole transport in the single-crystal FET, indicating that in the absence of external factors, by appropriate device design, CH3NH3PbI3 also has potential for use in ambipolar transistors.
2017, 33(1): 255-261
doi: 10.3866/PKU.WHXB201610181
Abstract:
In this article, we used coal-derived carbon foam (CCF) as a skeleton material to encapsulate the solid-to-solid phase change material polyurethane (PU) to provide PU@CCF composites for functional applications. The obtained PU@CCF composites were characterized by field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and thermal conductivity measurements. The results illustrated that the most preferred ratio of polyethylene glycol (PEG-6000) to hexamethylene diisocyanate (HDI) to synthesize PU was 1:2 and the CCF skeleton prevented PU leakage during the phase change process. Compared with PEG-6000, the thermal conductivity of the PU@CCF composite was raised by 54%, its cycle thermal stability was remarkable after 2000 cycles, and its supercooling degree was lowered by more than 10℃. For electro-to-heat energy conversion, the phase transition behavior of the obtained PU@CCF could be induced under an electron voltage as low as 0.8 V with 75% conversion efficiency at 1.1 V. This functional phase change composite realizes electric-heat conversion under the lowest loading voltage reported to date, providing an important benchmark for the preparation and functionalization of low-cost phase change composites.
In this article, we used coal-derived carbon foam (CCF) as a skeleton material to encapsulate the solid-to-solid phase change material polyurethane (PU) to provide PU@CCF composites for functional applications. The obtained PU@CCF composites were characterized by field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and thermal conductivity measurements. The results illustrated that the most preferred ratio of polyethylene glycol (PEG-6000) to hexamethylene diisocyanate (HDI) to synthesize PU was 1:2 and the CCF skeleton prevented PU leakage during the phase change process. Compared with PEG-6000, the thermal conductivity of the PU@CCF composite was raised by 54%, its cycle thermal stability was remarkable after 2000 cycles, and its supercooling degree was lowered by more than 10℃. For electro-to-heat energy conversion, the phase transition behavior of the obtained PU@CCF could be induced under an electron voltage as low as 0.8 V with 75% conversion efficiency at 1.1 V. This functional phase change composite realizes electric-heat conversion under the lowest loading voltage reported to date, providing an important benchmark for the preparation and functionalization of low-cost phase change composites.
