共查询到20条相似文献,搜索用时 617 毫秒
1.
Yue Lin Maxwell Thomas Dylla Jimmy Jiahong Kuo James Patrick Male Ian Anthony Kinloch Robert Freer Gerald Jeffery Snyder 《Advanced functional materials》2020,30(12)
Grain boundaries critically limit the electronic performance of oxide perovskites. These interfaces lower the carrier mobilities of polycrystalline materials by several orders of magnitude compared to single crystals. Despite extensive effort, improving the mobility of polycrystalline materials (to meet the performance of single crystals) is still a severe challenge. In this work, the grain boundary effect is eliminated in perovskite strontium titanate (STO) by incorporating graphene into the polycrystalline microstructure. An effective mass model provides strong evidence that polycrystalline graphene/strontium titanate (G/STO) nanocomposites approach single crystal‐like charge transport. This phenomenological model reduces the complexity of analyzing charge transport properties so that a quantitative comparison can be made between the nanocomposites and STO single crystals. In other related works, graphene composites also optimize the thermal transport properties of thermoelectric materials. Therefore, decorating grain boundaries with graphene appears to be a robust strategy to achieve “phonon glass–electron crystal” behavior in oxide perovskites. 相似文献
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Jian Sheng Zhen Han Guodong Jia Sheng Zhu Yifan Xu Xinrui Zhang Yixi Yao Yan Li 《Advanced functional materials》2023,33(43):2306785
Integrating 1D carbon nanotubes (CNTs) and 2D graphene with covalent bonds can inherit the outstanding properties of both components and obtain additional advantages. Here, this work reports the preparation of covalently bonded graphene/CNT (G/CNT) structure by a normal chemical vapor deposition method. Specifically, the pre-synthesized defects on the sidewall of CNTs act as nucleation sites for the growth of graphene sheets to form a branch-leaf structure. Graphene leaves restrict the sliding and re-stacking of CNTs, endowing G/CNT hybrid demonstrates excellent anti-agglomeration properties that are not present in either graphene or CNTs. In addition, the covalently bonded structure and high graphitization degree of graphene sheets and CNTs significantly enhance the comprehensive properties of the G/CNT hybrid material, such as large specific surface area, excellent thermal stability, and high electrical conductivity. Consequently, the microwave absorption properties of G/CNT are significantly enhanced compared with CNTs. This work provides a feasible pathway to synthesize high-performance covalently bonded G/CNT hybrids. 相似文献
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Facile Doping and Work‐Function Modification of Few‐Layer Graphene Using Molecular Oxidants and Reductants 下载免费PDF全文
Ahmed E. Mansour Marcel M. Said Sukumar Dey Hanlin Hu Siyuan Zhang Rahim Munir Yadong Zhang Karttikay Moudgil Stephen Barlow Seth R. Marder Aram Amassian 《Advanced functional materials》2017,27(7)
Doping of graphene is a viable route toward enhancing its electrical conductivity and modulating its work function for a wide range of technological applications. In this work, the authors demonstrate facile, solution‐based, noncovalent surface doping of few‐layer graphene (FLG) using a series of molecular metal‐organic and organic species of varying n‐ and p‐type doping strengths. In doing so, the authors tune the electronic, optical, and transport properties of FLG. The authors modulate the work function of graphene over a range of 2.4 eV (from 2.9 to 5.3 eV)—unprecedented for solution‐based doping—via surface electron transfer. A substantial improvement of the conductivity of FLG is attributed to increasing carrier density, slightly offset by a minor reduction of mobility via Coulomb scattering. The mobility of single layer graphene has been reported to decrease significantly more via similar surface doping than FLG, which has the ability to screen buried layers. The dopant dosage influences the properties of FLG and reveals an optimal window of dopant coverage for the best transport properties, wherein dopant molecules aggregate into small and isolated clusters on the surface of FLG. This study shows how soluble molecular dopants can easily and effectively tune the work function and improve the optoelectronic properties of graphene. 相似文献
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Single-layer graphene (SLG) has drawn considerable interest in photoelectrochemical (PEC) cells due to its atomically flat pinhole-free structure and remarkable in-plane carrier mobility. It is challenging, however, to obtain efficient SLG-modified photoelectrodes for PEC water splitting mainly due to the inefficient charge transfer interface. Here, a transition metal oxide/SLG/transition metal sandwich structure modified n-Si-based model photoanode is constructed to regulate the interfacial charge transfer behavior for enhanced PEC water oxidation performance. In this sandwich configuration, SLG tailors the morphology, structure, and work function properties of surface metal electrocatalysts to obtain both higher thermodynamic photovoltage and faster kinetical charge transfer at the semiconductor/electrolyte interface. In addition, SLG promotes the surface catalytic reaction as an effective charge trap and storage layer. This study provides a new structural design to engineer the SLG interfacial properties for high-performance energy conversion devices. 相似文献
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The remarkable thermal properties of graphene and carbon nanotubes (CNTs) have been the subject of intensive investigations for the thermal management of integrated circuits. However, the small contact area of CNTs and the large anisotropic heat conduction of graphene have hindered their applications as effective thermal interface materials (TIMs). Here, a covalently bonded graphene–CNT (G‐CNT) hybrid is presented that multiplies the axial heat transfer capability of individual CNTs through their parallel arrangement, while at the same time it provides a large contact area for efficient heat extraction. Through computer simulations, it is demonstrated that the G‐CNT outperforms few‐layer graphene by more than 2 orders of magnitude for the c‐axis heat transfer, while its thermal resistance is 3 orders of magnitude lower than the state‐of‐the‐art TIMs. We show that heat can be removed from the G‐CNT by immersing it in a liquid. The heat transfer characteristics of G‐CNT suggest that it has the potential to revolutionize the design of high‐performance TIMs. 相似文献
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Interfacial engineering is crucial for the stability and efficiency of organic solar cells. PEDOT:PSS, which has been widely used as a hole transport layer, has stability issues when exposed to air because of its acidic and hygroscopic nature. Herein, we investigated the electrical properties of reduced graphene oxide covered with an F4TCNQ interfacial layer as an alternative and its effect on the photovoltaic performance. Using an array of charge transport, spectroscopic and imaging techniques we found that the reduced graphene oxide film is efficiently hole-doped through an interfacial charge transfer, which enhances its electrical properties and favorably modifies its work function. Consequently, the open-circuit voltage and fill factor of solar cells incorporating such films are improved. P3HT might also be hole-doped by F4TCNQ, due to the formation of an intermixed interfacial layer, resulting in an increase of power conversion efficiency. 相似文献
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Sustainable Synthesis and Assembly of Biomass‐Derived B/N Co‐Doped Carbon Nanosheets with Ultrahigh Aspect Ratio for High‐Performance Supercapacitors 下载免费PDF全文
Zheng Ling Zhiyu Wang Mengdi Zhang Chang Yu Gang Wang Yanfeng Dong Shaohong Liu Yuwei Wang Jieshan Qiu 《Advanced functional materials》2016,26(1):111-119
The practical application of graphene has still been hindered by high cost and scarcity in supply. It boosts great interest in seeking for low‐cost substitute of graphene for upcoming usage where extremely physical properties are not absolutely critical. The conversion of renewable biomass offers a great opportunity for sustainable and economic fabrication of 2D carbon nanostructures. However, large‐scale production of carbon nanosheets with ultrahigh aspect ratio, satisfied electronic properties, and the capability of organized assembly like graphene has been rarely reported. In this work, a facile yet efficient approach for mass production of flexible boric/nitrogen co‐doped carbon nanosheets with very thin thickness of 5–8 nm and ultrahigh aspect ratio of over 6000–10 000 is demonstrated by assembling the biomass molecule in long‐range order on 2D hard template and subsequent annealing. The advantage of these doped carbon nanosheets over conventional products lies in that they can be readily assembled to multilevel architectures such as freestanding flexible thin film and ultralight aerogels with better electrical properties, which exhibit exceptional capacitive performance for supercapacitor application. The recyclability of boric acid template further reduces the discharge of the waste and processing cost, rendering high cost‐effectiveness and environmental benignity for scalable production. 相似文献
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Strain Modulation in Graphene/ZnO Nanorod Film Schottky Junction for Enhanced Photosensing Performance 下载免费PDF全文
Shuo Liu Qingliang Liao Shengnan Lu Zheng Zhang Guangjie Zhang Yue Zhang 《Advanced functional materials》2016,26(9):1347-1353
Strain modulation in flexible semiconductor heterojunctions has always been considered as an effective way to modulate the performance of nanodevices. In this work, a graphene/ZnO nanorods film Schottky junction has been constructed. It shows considerable responsivity and fast on‐off switch to the UV illumination. Through utilizing the piezopotential induced by the atoms displacement in ZnO under the compressive strain, 17% enhanced photosensing property is achieved in this hybrid structure when applying ?0.349% strain. This performance improvement can be ascribed to the Schottky barrier height modification by the strain‐induced piezopotential, which results in the facilitation of electron–hole separation in the graphene/ZnO interface. An energy band principle as well as a finite element analysis is proposed to understand this phenomenon. The results here provide a facile approach to boost the optoelectronic performance of graphene/ZnO heterostructure, which may also be applied to other Schottky junction based hybrid devices. 相似文献
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Kai Zhang Fung Ling Yap Kun Li Chang Tai Ng Lin Jun Li Kian Ping Loh 《Advanced functional materials》2014,24(6):731-738
Vertical integration of hexagonal boron nitride (h‐BN) and graphene for the fabrication of vertical field‐effect transistors or tunneling diodes has stimulated intense interest recently due to the enhanced performance offered by combining an ultrathin dielectric with a semi‐metallic system. Wafer scale fabrication and processing of these heterostructures is needed to make large scale integrated circuitry. In this work, by using remote discharged, radio‐frequency plasma chemical vapor deposition, wafer scale, high quality few layer h‐BN films are successfully grown. By using few layer h‐BN films as top gate dielectric material, the plasmon energy of graphene can be tuned by electrostatic doping. An array of graphene/h‐BN vertically stacked micrometer‐sized disks is fabricated by lithography and transfer techniques, and infrared spectroscopy is used to observe the modes of tunable graphene plasmonic absorption as a function of the repeating (G/h‐BN)n units in the vertical stack. Interestingly, the plasmonic resonances can be tuned to higher frequencies with increasing layer thickness of the disks, showing that such vertical stacking provides a viable strategy to provide wide window tuning of the plasmons beyond the limitation of the monolayer. 相似文献
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Da Zhan Li Sun Zhen Hua Ni Lei Liu Xiao Feng Fan Yingying Wang Ting Yu Yeng Ming Lam Wei Huang Ze Xiang Shen 《Advanced functional materials》2010,20(20):3504-3509
Graphene has attracted much attention since its first discovery in 2004. Various approaches have been proposed to control its physical and electronic properties. Here, it is reported that graphene‐based intercalation is an efficient method to modify the electronic properties of few‐layer graphene (FLG). FeCl3 intercalated FLGs are successfully prepared by the two‐zone vapor transport method. This is the first report on full intercalation for graphene samples. The features of the Raman G peak of such FLG intercalation compounds (FLGIC) are in good agreement with their full intercalation structures. The FLGICs present single Lorentzian 2D peaks, similar to that of single‐layer graphene, indicating the loss of electronic coupling between adjacent graphene layers. First principle calculations further reveal that the band structure of FLGIC is similar to single‐layer graphene but with a strong doping effect due to the charge transfer from graphene to FeCl3. The successful fabrication of FLGIC opens a new way to modify properties of FLG for fundamental studies and future applications. 相似文献
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Defect‐Rich Ni3FeN Nanocrystals Anchored on N‐Doped Graphene for Enhanced Electrocatalytic Oxygen Evolution 下载免费PDF全文
Shulin Zhao Meng Li Min Han Dongdong Xu Jing Yang Yue Lin Nai‐En Shi Yanan Lu Rui Yang Bitao Liu Zhihui Dai Jianchun Bao 《Advanced functional materials》2018,28(18)
Owing to their unique optical, electronic, and catalytic properties, metal nitrides nanostructures are widely used in optoelectronics, clean energy, and catalysis fields. Despite great progress has been achieved, synthesis of defect‐rich (DR) bimetallic nitride nanocrystals or related nanohybrids remains a challenge, and their electrocatalytic application for oxygen evolution reaction (OER) has not been fully studied. Herein, the DR‐Ni3FeN nanocrystals and N‐doped graphene (N‐G) nanohybrids (DR‐Ni3FeN/N‐G) are fabricated through temperature‐programmed annealing and nitridation treatment of NiFe‐layered double hydroxides/graphene oxide precursors by controlling annealing atmosphere. In the nanohybrids, the DR‐Ni3FeN nanocrystals are anchored on N‐G, and mainly show twin crystal defects besides ≈10% of stacking faults. Such nanohybrids can efficiently catalyze OER in alkaline media with a small overpotential (0.25 V) to attain the current density of 10 mA cm?2 and a high turnover frequency (0.46 s?1), superior to their counterparts (the nearly defect‐free Ni3FeN/N‐G), commercial IrO2, and the‐state‐of‐art reported OER catalysts. Except for the superior activity, they show better durability than their counterparts yet. As revealed by microstructural, spectroscopic, and electrochemical analyses, the enhanced OER performance of DR‐Ni3FeN/N‐G nanohybrids originates from the abundant twin crystal defects in Ni3FeN active phase and the strong interplay between DR‐Ni3FeN and N‐G. 相似文献
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Jun Wan Liang Huang Jiabin Wu Liukang Xiong Zhimi Hu Huimin Yu Tianqi Li Jun Zhou 《Advanced functional materials》2018,28(22)
Porous graphene has been widely applied in energy storage, electrocatalysis, photoelectron devices, etc. However, the producing process for porous graphene usually needs long time and is a tedious step. In this work, porous graphene is prepared with controllable pore size by using active metal nanoparticles to catalytically oxidize carbon under microwave combustion process within tens of seconds. The ion exchange membrane based on porous graphene with ≈5 nm pore diameter exhibits a great performance for salinity gradient power generation application with a power density output of ≈1.15 W m?2. This work highlights a new strategy for the design and synthesis of pore‐size‐controllable porous graphene and provides new opportunities for 2D porous nanomaterials. 相似文献
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Diana Berman Sanket A. Deshmukh Subramanian K. R. S. Sankaranarayanan Ali Erdemir Anirudha V. Sumant 《Advanced functional materials》2014,24(42):6640-6646
During the last few years, graphene's unusual friction and wear properties have been demonstrated at nano to micro scales but its industrial tribological potential has not been fully realized. The macroscopic wear resistance of one atom thick graphene coating is reported by subjecting it to pin‐on‐disc type wear testing against most commonly used steel against steel tribo‐pair. It is shown that when tested in hydrogen, a single layer of graphene on steel can last for 6400 sliding cycles, while few‐layer graphene (3–4 layers) lasts for 47 000 cycles. Furthermore, these graphene layers are shown to completely cease wear despite the severe sliding conditions including high contact pressures (≈0.5 GPa) observed typically in macroscale wear tests. The computational simulations show that the extraordinary wear performance originates from hydrogen passivation of the dangling bonds in a ruptured graphene, leading to significant stability and longer lifetime of the graphene protection layer. Also, the electronic properties of these graphene sheets are theoretically evaluated and the improved wear resistance is demonstrated to preserve the electronic properties of graphene and to have significant potential for flexible electronics. The findings demonstrate that tuning the atomistic scale chemical interactions holds the promise of realizing extraordinary tribological properties of monolayer graphene coatings. 相似文献
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A chemical approach to controlling the work function of few‐layer graphene is investigated. Graphene films are synthesized on Cu foil by chemical vapor deposition. Six metal chlorides, AuCl3, IrCl3, MoCl3, OsCl3, PdCl2, and RhCl3, are used as dopants. The sheet resistance of the doped graphene decreases from 1100 Ω/sq to ≈500–700 Ω/sq and its transmittance at 550 nm also decreases from 96.7% to 93% for 20 mM AuCl3 due to the formation of metal particles. The sheet resistance and transmittance are reduced with increasing metal chloride concentration. The G peak in the Raman spectra is shifted to a higher wavenumber after metal chloride doping, which indicates a charge transfer from graphene to metal ions. The intensity ratio of IC?C/IC?C increases with doping, indicating an electron transfer from graphene sheets to metal ions. Ultraviolet photoemission spectroscopy data shows that the work function of graphene increases from 4.2 eV to 5.0, 4.9, 4.8, 4.68, 5.0, and 5.14 eV for the graphene with 20 mM AuCl3, IrCl3, MoCl3, OsCl3, PdCl2, and RhCl3, respectively. It is considered that spontaneous charge transfer occurs from the specific energy level of graphene to the metal ions, thus increasing the work function. 相似文献
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报道了使用石墨烯作为阳极材料的GaN肖特基型紫外探测器。介绍了光敏面为1mm×1mm的新型肖特基紫外探测器的制备过程。并对器件进行了响应光谱、I-V特性测试。器件的响应光谱较为平坦,峰值响应度为0.175A/W;通过对石墨烯进行化学修饰,使峰值响应度增加到0.23A/W。并根据热电子发射理论,计算出了器件掺杂前后的肖特基势垒高度分别为0.477eV和0.882eV,验证了器件性能的提高主要原因是石墨烯功函数的增加。 更多还原 相似文献
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Amorphous FeOOH Quantum Dots Assembled Mesoporous Film Anchored on Graphene Nanosheets with Superior Electrochemical Performance for Supercapacitors 下载免费PDF全文
Jiaqi Liu Mingbo Zheng Xiaoqin Shi Haibo Zeng Hui Xia 《Advanced functional materials》2016,26(6):919-930
Previous research on iron oxides/hydroxides has focused on the crystalline rather than the amorphous phase, despite that the latter could have superior electrochemical activity due to the disordered structure. In this work, a simple and scalable synthesis route is developed to prepare amorphous FeOOH quantum dots (QDs) and FeOOH QDs/graphene hybrid nanosheets. The hybrid nanosheets possess a unique heterostructure, comprising a continuous mesoporous FeOOH nanofilm tightly anchored on the graphene surface. The amorphous FeOOH/graphene hybrid nanosheets exhibit superior pseudocapacitive performance, which largely outperforms the crystalline iron oxides/hydroxides‐based materials. In the voltage range between ?0.8 and 0 V versus Ag/AgCl, the amorphous FeOOH/graphene composite electrode exhibits a large specific capacitance of about 365 F g?1, outstanding cycle performance (89.7% capacitance retention after 20 000 cycles), and excellent rate capability (189 F g?1 at a current density of 128 A g?1). When the lower cutoff voltage is extended to ?1.0 and ?1.25 V, the specific capacitance of the amorphous FeOOH/graphene composite electrode can be increased to 403 and 1243 F g?1, respectively, which, however, compromises the rate capability and cycle performance. This work brings new opportunities to design high‐performance electrode materials for supercapacitors, especially for amorphous oxides/hydroxides‐based materials. 相似文献
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石墨烯具有优异的物理化学性质,在MEMS器件、光电检测材料、柔性显示屏、新能源电池、复合材料等方面成为研究热点。目前大面积石墨烯制备主要依赖于化学气相沉积技术(chemical vapor deposition, CVD),但其生长的晶体质量直接影响到电化学特性和实际应用,因此需要一种快速而准确的表征方法。实验利用背向散射的偏振激光散射装置测量CVD生长的石墨烯拉曼光谱。通过分析实验获得的300 nm SiO2/Si基底上的单层、五层和十层左右的石墨烯角分辨偏振拉曼光谱,发现单层生长的石墨烯偏振特性与机械剥离单晶石墨烯一致;随着层数的增加,G峰偏振响应差异更加明显,表现出明显的椭圆特性;在不同石墨烯层数上的D峰也呈现出一定的偏振响应差异性。偏振拉曼测试结果表明目前CVD生长的缺陷和多晶特性与石墨烯层数呈现正相关特征。 相似文献