电化学还原法制备石墨烯膜电极

采用电化学还原法成功将氧化石墨烯还原,得到具有一定柔性的石墨烯膜。利用扫描电子显微镜法(SEM)、透射电子显微镜法(TEM)、拉曼光谱、X射线光电子光谱法(XPS)等测试手段对石墨烯材料的结构和形貌进行了表征;结果表明,所制备的石墨烯形貌较好、表面平整、无褶皱;通过测试其电化学性能对其还原电位、膜层厚度等制备条件进行了优化;当伏安循环电压范围为-2.0~2.0 V、膜厚度为1μm时,得到的石墨烯膜电化学性能优异,电流密度为0.1 A/g时,比电容可以达到123.8 F/g。     

两步法制备多孔石墨烯的电化学性能

通过两步法,以氧化石墨烯(GO)为前驱体,先采用抗坏血酸(VC)、KMn O4和Na2CO3为还原剂,水热反应还原氧化石墨烯,再分别利用化学刻蚀法和硝酸超声波法,制备多孔石墨烯。通过XRD、SEM、傅里叶转换红外光谱(FT-IR)、拉曼光谱(Raman)和热重(TG)等测试分析材料的表面微观结构和还原程度;采用循环伏安(CV)、恒流充放电及电化学阻抗谱(EIS)测试材料的电化学性能。以VC为还原剂,制得还原程度较好且孔结构明显的石墨烯,用硝酸超声波处理后的石墨烯孔径小而且均匀,以1 A/g的电流在0~0.56 V循环,电极材料的比电容为87.50 F/g。     

A multilayer graphene-based absorber for the sub-THz regime

Journal of Computational Electronics - This work presents a four-layer absorber based on graphene patterns. Periodic arrays of biased graphene nanodisks and ribbons are exploited, while a graphene...     

石墨烯的制备及其电化学性能

以石墨为原料,采用改进的Hummers方法制备氧化石墨,在水中经超声分散得到氧化石墨烯水溶胶,经硼氢化钠还原得到石墨烯聚集物。采用扫描电镜、原子力显微镜、激光粒度分析仪、BET氮气吸附仪对样品的形态、粒度分布和比表面积进行了表征。采用恒流充放电和循环伏安法研究了样品的充放电性能。结果表明,氧化石墨在水溶液中可以剥离成单片层结构,石墨烯聚集物比表面积为358m2/g,在10mA恒流下充放电,比电容为138.6F/g,充放电容量效率为98%。以5～50mV/s扫描速率进行循环伏安测试,石墨烯电极表现出良好的双电层电容器性能。     

基于ZnO/Graphene纳米复合材料紫外光探测器的制备与实现

利用化学气相沉积法制备氧化锌（ZnO）纳米线,通过微加工工艺获得了基于 ZnO 纳米线与ZnO石墨烯量子点纳米复合材料的紫外光探测器。ZnO 石墨烯纳米复合材料的结构和表面形貌通过 X 射线电子衍射和扫描电镜来表征,结果表明,ZnO 纳米线的直径约为33 nm,与石墨烯量子点很好地复合在了一起。利用紫外可见吸收谱对样品的光吸收进行了记录,实验表明,基于ZnO复合石墨烯量子点纳米复合材料的紫外探测器在 UV 照射下显示出良好的光响应行为,该类型基于ZnO复合石墨烯量子点探测器可能在ZnO紫外探测的应用方面具有潜在的意义。     

Coherent electron transport through freestanding graphene junctions with metal contacts: a materials approach

In this article we highlight recent work in which we computed the spin unpolarized coherent electron transport through two terminal nanoscale graphene/metal junctions using equilibrium Green’s functions coupled to Density functional theory, capturing in detail the important electronic effects created at metal/graphene interfaces. In those calculations the metal contacts may or may not bind covalently to graphene. Along the way, connections to other models for coherent transport on graphene junctions with metal contacts are given as well. As it may be known, the computation of the electronic dispersion at the interface between graphene and binding metals in a transport setup is extremely time-consuming, and it is perhaps for this reason that effects of metals are neglected or are captured only qualitatively in the theoretical and computational modeling of graphene devices. It thus seems to us that a methodology to go past this stumbling block may be well-received. We outline an approach to obtain tight-binding parameters describing the electronic dispersion at interfaces between titanium leads and graphene. The deployment of those tight-binding parameters is new, and it constitutes the main contribution on the present paper.     

基于石墨烯薄膜的静电扬声器理论建模与仿真分析

针对基于石墨烯薄膜的新型静电扬声器设计缺乏理论指导的问题,对石墨烯静电扬声器进行了理论建模和仿真分析研究。在静电扬声器原理的基础上,采用质量-弹簧-阻尼系统建模分析了石墨烯薄膜在工作时的振动特性,研究了薄膜半径,厚度和应力对其振动特性的影响,利用COMSOL软件建立了石墨烯静电扬声器的有限元模型,对比分析了不同薄膜半径、厚度和应力对应的石墨烯静电扬声器的频率响应特性,验证了理论模型的准确性。结果表明,石墨烯薄膜半径越大,厚度越薄,应力越小,相应的石墨烯静电扬声器频率响应特性越好。     

Quantum transport of pseudospin-polarized Dirac fermions in gapped graphene nanostructures

We investigate the unusual features of the quantum transport in gapped monolayer graphene, which is in a pseudospin symmetry-broken state with a net perpendicular pseudomagnetization. Using these pseudoferromagnets (PFs), we propose a perfect pseudospin valve effect that can be used for realizing pseudospintronics in monolayer graphene. The peculiarity of the associated effects of pseudospin injection and pseudospin accumulation are also studied. We further demonstrate the determining effect of the sublattice pseudospin degree of freedom on Andreev reflection and the associated proximity effect in hybrid structures of PFs and a superconductor in S/PF and PF/S/PF geometries. In particular, we find a peculiar Andreev reflection that is associated with an inversion of the z component of the carriers pseudospin vector. Our results show that the gapped normal graphene behaves like a ferromagnetic graphene and the effect of the pseudospin degree of freedom in gapped graphene is as important as the spin in a ferromagnetic graphene.     

石墨烯在锂离子电池中的应用研究

概述了石墨烯作为锂离子电池常用正极LiFePO4、LiMn2O4和负极Si、金属氧化物等电极材料的添加剂对材料性能的改善,以及其本身作为负极材料对锂离子电池性能的影响,并提出了石墨烯作为锂离子电池电极导电剂新的研究方向。     

Microstructure and Spectral Characteristics of Graphene Oxide during Reduction

In the paper, graphite oxide was prepared with the improved Hummers Method and then dispersed in water via ultrasonic dispersion to produce dispersion liquid. After the reduction with hydrazine hydrate, graphene colloidal dispersion liquid with different reduced degrees was obtained via controlling reaction time. Microstructure and crystal structure evolution were characterized via UV-visible absorption spectroscopy, infrared spectroscopy and scanning probe microscopy from the samples during the transition from graphene oxide to graphene. Here, we analyzed the time-variation relationship of graphene oxide surface functional groups, conjugated π bond, the single-layer thickness and particle size during the reduction. The obtained results showed that microstructure and surface structure had certain correlation and regularity that functional groups on graphene oxide surface, conjugated π bond, the single-layer thickness and sheet diameter had the identical evolution process.     

Terahertz absorption characteristics of multilayer graphene/polymer

Abstract

In this article, we fabricated two different graphene structure samples, composed of single-layer graphene and multilayer graphene/PMMA structures. When w samples are pumped by the 980?nm laser with different powers, we measure the time-domain and frequency domain spectra of the terahertz transmission using the terahertz time domain spectroscopy system. The measured results show that the average terahertz transmission can be actively controlled by changing the pump power or the layer number of graphene, which exhibits potential applications in the terahertz absorption devices.     

石墨烯添加剂对铅酸电池性能影响的研究

将石墨烯作为添加剂添加到铅酸蓄电池负极活性物质中,探究其对铅酸蓄电池性能的影响。无论是添加水性浆料状还是粉末状石墨烯,电池的容量都没有明显增加,并且随着石墨烯含量增加,电池容量降低,电池低温性能变差,但是充电接受性能提高。水性浆料状石墨烯含量为 1 % 的样品电池充电接受能力提升近 41 %。交流阻抗测试显示,加入水性浆料状石墨烯使蓄电池阻抗变大,但石墨烯与炭黑混合使用时,阻抗最小。     

Phonon bottleneck effects in rectangular graphene quantum dots

For a graphene sheet with confining structures in the orthogonal directions of zigzag- and armchair-edge, the confined carrier states are determined. These wavefunctions and eigenvalues are used to study carrier-longitudinal optical (LO)-phonon interactions in these graphene quantum dots. The optical deformation potential is derived for these graphene quantum dots as the basis for the study of these carrier-LO-phonon interactions. Phonon bottleneck effects are identified and the Fermi golden rule transition rates are formulated.     

Competing topological phases in few-layer graphene

We investigate the effect of spin-orbit coupling on the band structure of graphene-based two-dimensional Dirac fermion gases in the quantum Hall regime. Taking monolayer graphene as our first candidate, we show that a quantum phase transition between two distinct topological states—the quantum Hall and the quantum spin Hall phases—can be driven by simply tuning the Fermi level with a gate voltage. This transition is characterized by the existence of a chiral spin-polarized edge state propagating along the interface separating the two topological phases. We then apply our analysis to the more difficult case of bilayer graphene. Unlike in monolayer graphene, spin-orbit coupling by itself has indeed been predicted to be unsuccessful in driving bilayer graphene into a topological phase, due to the existence of an even number of pairs of spin-polarized edge states. While we show that this remains the case in the quantum Hall regime, we point out that by additionally breaking the layer inversion symmetry, a non-trivial quantum spin Hall phase can re-emerge in bilayer graphene at low energy. We consider two different symmetry-breaking mechanisms: inducing spin-orbit coupling only in the upper layer, and applying a perpendicular electric field. In both cases, the presence at low energy of an odd number of pairs of edge states can be driven by an exchange field. The related situation in trilayer graphene is also discussed.     

First principles modeling of disorder scattering in graphene

It is important to investigate impurity scattering phenomena when modeling graphene nanoscale devices, as impurities are invariably present in any realistic system and can significantly influence graphene carrier transport. We present a short review of quantum transport where density functional theory (DFT) is carried out within the nonequilibrium Green’s function formalism (NEGF), focusing on a recent extension of this framework in the form of nonequilibrium vertex correction (NVC) that captures random graphene impurity scattering in a systematic fashion. Our results show that disorder effects significantly alters the electronic and transport properties of graphene devices. We argue that disorder effects should not be ignored if one were to model graphene nanoscale devices in realistic situations, including arriving at fundamental electronic properties such as Ohm’s law.     

Geometric Stability,Electronic Structure and Reactivity of Pt4 Cluster Supported on Defective Graphene

The geometric stability, electronic structure and magnetic properties of the Pt₄ clusters on graphene substrates are investigated using the first-principles methods. It is found that the Pt₄ clusters on the defective graphene with a single vacancy defect (SV-graphene) have larger binding energies than that on the pristine graphene. The different position of SV sites can modulate the geometric stability of Pt₄ clusters. The Pt₄ clusters provide more transferred electrons to the SV-graphene and exhibit the positively charged, which helps to weaken the CO adsorption. The results would be important for understanding that the adsorption behavior of metal clusters on graphene.     

Short-range potential scattering and its effect on graphene mobility

Over the past few years, the amazing properties of graphene have led to predictions for its use in a variety of areas, not the least of which is in semiconductor devices. However, it appears that graphene is dominated by short-range potential scattering which can arise from intrinsic defects which limit the mobility to relatively low values, well below those predicted based upon its intrinsic band structure. Here, we examine the mobility in graphene on BN, SiC, and SiO₂ when it is dominated by these defects.     

High‐frequency modeling of Cu‐graphene heterogeneous interconnects

One novel interconnect scheme consisting of both Cu and graphene sheet is proposed in this paper, with the advantages of both materials exploited greatly. It is shown that the introduction of graphene layers in such heterogeneous interconnect scheme can reduce its effective resistance and thereby improve its transmission performance. On the other hand, it is also demonstrated that both coated and double‐coated structures possess better electrical performance than that of the sandwich one at high frequencies, because the graphene is placed at the interconnect surface where current is crowded. With the help of Partial Element Equivalent Circuit method, together with equivalent circuit technique, the transmission characteristics of some Cu‐graphene interconnects are captured and compared with that of Cu wire, and the advantages of such heterogeneous interconnects can be enlarged with the advanced technology. Copyright © 2015 John Wiley & Sons, Ltd.     

石墨烯在锂离子电池正极材料中应用的进展

综述了石墨烯与聚阴离子型、尖晶石型、层状结构的正极材料复合,改善锂离子电池电化学性能的研究进展。总结了石墨烯在锂离子电池正极材料中的应用所面临的问题。     

Active EIT-like Dependent on Polarization Angle with Graphene Metamaterial

Abstract

An active electromagnetically induced transparency (EIT) analog adopting graphene as microstructure of metamaterial is investigated. The analog consist interconnected graphene strip (GS) and graphene split ring resonator (GSRR), which can act as bright and dark elements alternately. The distinct EIT-like effect can be generated by bright-dark mode coupling in x and y polarization directions. Further investigations reveal that EIT peak can be actively controlled via Fermi level of graphene, and theoretical analysis based on two particles mode express the reason. Moreover, notable EIT-like effect can also be generated in a wide range of polarization angles, and impact of polarization angle on EIT peak is also discussed in detail. These characteristic paves the way for the applications of EIT-like in sensor device.