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Kiana Montazeri Marc Currie Louisiane Verger Pouya Dianat Michel W. Barsoum Bahram Nabet 《Advanced materials (Deerfield Beach, Fla.)》2019,31(43)
2D transition metal carbides, known as MXenes, are transparent when the samples are thin enough. They are also excellent electrical conductors with metal‐like carrier concentrations. Herein, these characteristics are exploited to replace gold (Au) in GaAs photodetectors. By simply spin‐coating transparent Ti3C2‐based MXene electrodes from aqueous suspensions onto GaAs patterned with a photoresist and lifted off with acetone, photodetectors that outperform more standard Au electrodes are fabricated. Both the Au‐ and MXene‐based devices show rectifying contacts with comparable Schottky barrier heights and internal electric fields. The latter, however, exhibit significantly higher responsivities and quantum efficiencies, with similar dark currents, hence showing better dynamic range and detectivity, and similar sub‐nanosecond response speeds compared to the Au‐based devices. The simple fabrication process is readily integratable into microelectronic, photonic‐integrated circuits and silicon photonics processes, with a wide range of applications from optical sensing to light detection and ranging and telecommunications. 相似文献
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Hsin‐Yi Wang Fang‐Xing Xiao Le Yu Bin Liu Xiong Wen Lou 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(15):3181-3186
A facile two‐step solution‐phase method has been developed for the preparation of hierarchical α‐MnO2 nanowires@Ni1‐xMnxOy nanoflakes core–shell nanostructures. Ultralong α‐MnO2 nanowires were synthesized by a hydrothermal method in the first step. Subsequently, Ni1‐xMnxOy nanoflakes were grown on α‐MnO2 nanowires to form core–shell nanostructures using chemical bath deposition followed by thermal annealing. Both solution‐phase methods can be easily scaled up for mass production. We have evaluated their application in supercapacitors. The ultralong one‐dimensional (1D) α‐MnO2 nanowires in hierarchical core–shell nanostructures offer a stable and efficient backbone for charge transport; while the two‐dimensional (2D) Ni1‐xMnxOy nanoflakes on α‐MnO2 nanowires provide high accessible surface to ions in the electrolyte. These beneficial features enable the electrode with high capacitance and reliable stability. The capacitance of the core–shell α‐MnO2@Ni1‐xMnxOy nanostructures (x = 0.75) is as high as 657 F g?1 at a current density of 250 mA g?1, and stable charging‐discharging cycling over 1000 times at a current density of 2000 mA g?1 has been realized. 相似文献
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Creating Graphitic Carbon Nitride Based Donor‐π–Acceptor‐π–Donor Structured Catalysts for Highly Photocatalytic Hydrogen Evolution
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Conjugated polymers with tailored donor–acceptor units have recently attracted considerable attention in organic photovoltaic devices due to the controlled optical bandgap and retained favorable separation of charge carriers. Inspired by these advantages, an effective strategy is presented to solve the main obstructions of graphitic carbon nitride (g‐C3N4) photocatalyst for solar energy conversion, that is, inefficient visible light response and insufficient separation of photogenerated electrons and holes. Donor‐π–acceptor‐π–donor polymers are prepared by incorporating 4,4′‐(benzoc 1,2,5 thiadiazole‐4,7‐diyl) dianiline (BD) into the g‐C3N4 framework (UCN‐BD). Benefiting from the visible light band tail caused by the extended π conjugation, UCN‐BD possesses expanded visible light absorption range. More importantly, the BD monomer also acts as an electron acceptor, which endows UCN‐BD with a high degree of intramolecular charge transfer. With this unique molecular structure, the optimized UCN‐BD sample exhibits a superior performance for photocatalytic hydrogen evolution upon visible light illumination (3428 µmol h?1 g?1), which is nearly six times of that of the pristine g‐C3N4. In addition, the photocatalytic property remains stable for six cycles in 3 d. This work provides an insight into the synthesis of g‐C3N4‐based D‐π–A‐π–D systems with highly visible light response and long lifetime of intramolecular charge carriers for solar fuel production. 相似文献
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L.‐M. Berger F.‐L. Toma S. Scheitz R. Trache T. Börner 《Materialwissenschaft und Werkstofftechnik》2014,45(6):465-475
With exception of ZrO2, the individual oxides and binary compositions in the system Al2O3–Cr2O3–TiO2 are the most important oxide materials for the preparation of thermally sprayed coatings. In this contribution selected results of recent own research activities are summarized. This includes the comparison of microstructures, phase compositions, and properties of coatings, deposited by atmospheric plasma spraying (APS) and high velocity oxy‐fuel (HVOF) spraying. The possibilities arriving from the use of suspensions as feedstock are reviewed. Special attention is paid to the advantage of use of binary compositions in this system. Tribological, electrical and corrosion properties of the coatings are discussed. 相似文献
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Yolk–Shell MnO@ZnMn2O4/N–C Nanorods Derived from α‐MnO2/ZIF‐8 as Anode Materials for Lithium Ion Batteries
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Ming Zhong Donghui Yang Chenchao Xie Zhang Zhang Zhen Zhou Xian‐He Bu 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(40):5564-5571
Manganese oxides (MnOx) are promising anode materials for lithium ion batteries, but they generally exhibit mediocre performances due to intrinsic low ionic conductivity, high polarization, and poor stability. Herein, yolk–shell nanorods comprising of nitrogen‐doped carbon (N–C) coating on manganese monoxide (MnO) coupled with zinc manganate (ZnMn2O4) nanoparticles are manufactured via one‐step carbonization of α‐MnO2/ZIF‐8 precursors. When evaluated as anodes for lithium ion batteries, MnO@ZnMn2O4/N–C exhibits an reversible capacity of 803 mAh g?1 at 50 mA g?1 after 100 cycles, excellent cyclability with a capacity of 595 mAh g?1 at 1000 mAg?1 after 200 cycles, as well as better rate capability compared with those non‐N–C shelled manganese oxides (MnOx). The outstanding electrochemical performance is attributed to the unique yolk–shell nanorod structure, the coating effect of N–C and nanoscale size. 相似文献
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Architecture of β‐Graphdiyne‐Containing Thin Film Using Modified Glaser–Hay Coupling Reaction for Enhanced Photocatalytic Property of TiO2
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Jiaqiang Li Ziqian Xie Yan Xiong Zhenzhu Li Qunxing Huang Shuqing Zhang Jingyuan Zhou Rong Liu Xin Gao Changguo Chen Lianming Tong Jin Zhang Zhongfan Liu 《Advanced materials (Deerfield Beach, Fla.)》2017,29(19)
β‐Graphdiyne (β‐GDY) is a member of 2D graphyne family with zero band gap, and is a promising material with potential applications in energy storage, organic electronics, etc. However, the synthesis of β‐GDY has not been realized yet, and the measurement of its intrinsic properties remains elusive. In this work, β‐GDY‐containing thin film is successfully synthesized on copper foil using modified Glaser–Hay coupling reaction with tetraethynylethene as precursor. The as‐grown carbon film has a smooth surface and is continuous and uniform. Electrical measurements reveal the conductivity of 3.47 × 10?6 S m?1 and the work function of 5.22 eV. TiO2@β‐GDY nanocomposite is then prepared and presented with an enhancement of photocatalytic ability compared to pure TiO2. 相似文献
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Haiqing Dong Yongyong Li Jinhai Yu Yanyan Song Xiaojun Cai Jiaqiang Liu Jiaming Zhang Rodney C. Ewing Donglu Shi 《Small (Weinheim an der Bergstrasse, Germany)》2013,9(3):446-456
A multi‐component nanosystem based on graphene and comprising individual cyclodextrins at its surface is assembled, creating hybrid structures enabling new and important functionalities: optical imaging, drug storage, and cell targeting for medical diagnosis and treatment. These nanohybrids are part of a universal system of interchangeable units, capable of mutilple functionalities. The surface components, made of individual β‐cyclodextrin molecules, are the “hosts” for functional units, which may be used as imaging agents, for anti‐cancer drug delivery, and as tumor‐specific ligands. Specifically, individual β‐cyclodextrin (β‐CD), with a known capability to host various molecules, is considered a module unit that is assembled onto graphene nanosheet (GNS). The cyclodextrin‐functionalized graphene nanosheet (GNS/β‐CD) enables “host–guest” chemistry between the nanohybrid and functional “payloads”. The structure, composition, and morphology of the graphene nanosheet hybrid have been investigated. The nanohybrid, GNS/β‐CD, is highly dispersive in various physiological solutions, reflecting the high biostability of cyclodextrin. Regarding the host capability, the nanohybrid is fully capable of selectively accommodating various biological and functional agents in a controlled fashion, including the antivirus drug amantadine, fluorescent dye [5(6)‐carboxyfluorescein], and Arg‐Gly‐Asp (RGD) peptide‐targeting ligands assisted by an adamantine linker. The loading ratio of 5(6)‐carboxyfluorescein is as high as 110% with a drug concentration of 0.45 mg mL?1. The cyclic RGD‐functionalized nanohybrid exhibits remarkable targeting for HeLa cells. 相似文献
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Investigating the Hybrid‐Structure‐Effect of CeO2‐Encapsulated Au Nanostructures on the Transfer Coupling of Nitrobenzene
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Jian Li Shuyan Song Yan Long Lanlan Wu Xiao Wang Yan Xing Rongchao Jin Xiaogang Liu Hongjie Zhang 《Advanced materials (Deerfield Beach, Fla.)》2018,30(7)
Due to the obvious distinctions in structure, core–shell nanostructures (CSNs) and yolk–shell nanostructures (YSNs) exhibit different catalytic behavior for specific organic reactions. In this work, two unique autoredox routes are developed to the fabrication of CeO2‐encapsulated Au nanocatalysts. Route A is the synthesis of well‐defined CSNs by a one‐step redox reaction. The process involves an interesting phenomenon in which Ce3+ can act as a weak acid to inhibit the hydrolysis of Ce4+ under the condition of OH? shortage. Route B is the fabrication of monodispersed YSNs by a two‐step redox reaction with amorphous Co3O4 as an in situ template. Furthermore, the transfer coupling of nitrobenzene is chosen as a probe reaction to investigate their catalytic difference. The CSNs can gradually achieve the conversion of nitrobenzene into azoxybenzene, while the YSNs can rapidly convert nitrobenzene into azobenzene. The different catalytic results are mainly attributed to their structural distinctions. 相似文献
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Core–Shell Structure and Interaction Mechanism of γ‐MnO2 Coated Sulfur for Improved Lithium‐Sulfur Batteries
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Lubin Ni Zhen Wu Gangjin Zhao Chunyu Sun Chuanqiang Zhou XiangXiang Gong Guowang Diao 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(14)
Lithium‐sulfur batteries have attracted worldwide interest due to their high theoretical capacity of 1672 mAh g?1 and low cost. However, the practical applications are hampered by capacity decay, mainly attributed to the polysulfide shuttle. Here, the authors have fabricated a solid core–shell γ‐MnO2‐coated sulfur nanocomposite through the redox reaction between KMnO4 and MnSO4. The multifunctional MnO2 shell facilitates electron and Li+ transport as well as efficiently prevents polysulfide dissolution via physical confinement and chemical interaction. Moreover, the γ‐MnO2 crystallographic form also provides one‐dimensional (1D) tunnels for the Li+ incorporation to alleviate insoluble Li2S2/Li2S deposition at high discharge rate. More importantly, the MnO2 phase transformation to Mn3O4 occurs during the redox reaction between polysulfides and γ‐MnO2 is first thoroughly investigated. The S@γ‐MnO2 composite exhibits a good capacity retention of 82% after 300 cycles (0.5 C) and a fade rate of 0.07% per cycle over 600 cycles (1 C). The degradation mechanism can probably be elucidated that the decomposition of the surface Mn3O4 phase is the cause of polysulfide dissolution. The recent work thus sheds new light on the hitherto unknown surface interaction mechanism and the degradation mechanism of Li‐S cells. 相似文献
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Yi‐nan Wu Meimei Zhou Shu Li Zehua Li Jie Li Baozhen Wu Guangtao Li Fengting Li Xiaohong Guan 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(14):2927-2936
A general one‐step in situ pyrolysis route for the construction of metal–organic frameworks encapsulating superparamagnetic γ‐Fe2O3 NPs dispersed in the confined cavities of MOFs homogeneously is described. The integration of γ‐Fe2O3 NPs or clusters into MOFs can endow these porous materials with superparamagnetic element. By the combination of the thermal stability of MOFs and pyrolysis of metal triacetylacetonate complex at matched conditions, the porous structure of MOFs are well maintained while the size‐induced superparamagnetic property of nano γ‐Fe2O3 is obtained. As a proof of concept, both the γ‐ Fe2O3@ZIF‐8 and γ‐Fe2O3@MIL‐53(Al) were successfully prepared, and the latter was chosen to demonstrate its potential drug delivery as a magnetic MOF. 相似文献
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Ran Bi Guoxue Liu Cheng Zeng Xinping Wang Lei Zhang Shi‐Zhang Qiao 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(10)
Lithium–oxygen (Li–O2) batteries are attracting more attention owing to their superior theoretical energy density compared to conventional Li‐ion battery systems. With regards to the catalytically electrochemical reaction on a cathode, the electrocatalyst plays a key role in determining the performance of Li–O2 batteries. Herein, a new 3D hollow α‐MnO2 framework (3D α‐MnO2) with porous wall assembled by hierarchical α‐MnO2 nanowires is prepared by a template‐induced hydrothermal reaction and subsequent annealing treatment. Such a distinctive structure provides some essential properties for Li–O2 batteries including the intrinsic high catalytic activity of α‐MnO2, more catalytic active sites of hierarchical α‐MnO2 nanowires on 3D framework, continuous hollow network and rich porosity for the storage of discharge product aggregations, and oxygen diffusion. As a consequence, 3D α‐MnO2 achieves a high specific capacity of 8583 mA h g?1 at a current density of 100 mA g?1, a superior rate capacity of 6311 mA h g?1 at 300 mA g?1, and a very good cycling stability of 170 cycles at a current density of 200 mA g?1 with a fixed capacity of 1000 mA h g?1. Importantly, the presented design strategy of 3D hollow framework in this work could be extended to other catalytic cathode design for Li–O2 batteries. 相似文献
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Nazir Ahmad Hussein A. Younus Zhang Gaoke Kristof Van Hecke Francis Verpoort 《Advanced materials (Deerfield Beach, Fla.)》2019,31(19)
Synthesis of metal–organic materials is often dependent on the reaction conditions of suitable solvent/solvent mixture and temperature. A new finding based on a previously described protocol is reported: instead of obtaining metal–organic polyhedra (MOP), a metal–organic framework (MOF) with a 2D layered structure is obtained, following the same reported protocol. The 2D Cu(II)–5‐prop‐2‐ynoxyisophthlate MOF, crystallized in a kagomé‐type structure, is synthesized using different solvent systems at room temperature, as well as under solvothermal (nonhydrothermal) conditions. Under harsh reaction conditions, alkyne functional groups maintain their integrity and the copper does not catalyze the oxidative coupling of the terminal alkyne groups. X‐ray diffraction analyses confirm the structure and phase purity of the product. Based on the present results and the previous work reported by Zhao et al., it seems that two products, namely 0D MOP and 2D MOF, are equally possible when using the same reactants under same reaction conditions. However, the materials obtained in all the trials are MOF instead of MOP. From the structure point of view, there is a difference in connectivity of the initial building units that determines whether the product is MOP or MOF. 相似文献