Science and Engineering of Graphene Oxide

Functional and synthesis diversity of graphene oxide (GO) has led to various fundamental and applied scientific explorations. GO can be viewed as an in‐plane, hybrid 2D lattice consisting of sp2 and sp3 carbon regions. Engineering the type and distribution of sp3 regions can tune the physical properties of resultant GO. This article reviews the development in the field of GO since the 19th century, with a thorough discussion on its status after the discovery of graphene in last decade. Detailed structure, optical properties, electrochemical behavior, and its viability for biological applications are discussed from both a scientific and technological perspective and a future outlook for GO research is presented.     

Graphene and Graphene‐Based Materials in Biomedical Science

Graphene and its composite materials are very important in many disciplines of science and have been used enormously by researchers since their discovery in 2004. These are a new group of compounds, and are also wonderful model systems for quantum behavior studies. Their properties like exceptional conductivity, biocompatibility, surface area, mechanical strength, and thermal properties make them rising stars in the scientific community. Graphene and its composite compounds are utilized widely in different medical applications, for example, biosensing of biological compounds responsible for disease development, bioimaging of various cells, tissues, microorganisms, animal models, etc. In addition, they are used for enhancing and supporting the stem cell differentiation, i.e., regenerative medicine for regeneration studies of various human organs, tissue engineering in biology for the development of carrier materials, as well as in bone reformation. This review focuses on the modification procedure involved in the fabrication of graphene‐based biomaterials for various applications and recent developments in research related to graphene and graphene‐based materials in biosensing, optical sensing, gas sensing, drug, gene, protein delivery, tissue engineering, and bioimaging. In addition, the potential toxicological effects of graphene‐based biomaterials are discussed.     

News and Views: Perspectives on Graphene and Other 2D Materials Research and Technology Investments

With the actual experimental realization of graphene samples, it became possible not only to exploit the special physical properties of graphene but also to exploit its technological applications. As the field developed, the discovery of other 2D materials occurred and this opened up access to a plethora of combinations of a large variety of electrical, optical, mechanical, and chemical properties. Now there are large investments being made around the world to develop the graphene research area and to boost graphene use in technology. Here, we discuss current research and some future prospects for this area of layered nanomaterials.     

新型机械解理方法在二维材料研究中的应用

自从石墨烯被发现以来,机械解理技术已经成为制备高质量二维材料的重要方法之一,在二维材料本征物性的研究方面展现出了独特的优势.然而传统机械解理方法存在明显的不足,如制备效率低、样品尺寸小等,阻碍了二维材料领域的研究进展.近些年我们在机械解理技术方面取得了一系列的突破,独立发展了一套具有普适性的新型机械解理方法.这种新型机械解理方法的核心在于通过改变解理过程中的多个参数,增强层状材料与基底之间的范德瓦耳斯相互作用,从而提高单层样品的产率和面积.本文着重以石墨烯为例,介绍了该技术的过程和机理.相比于传统机械解理方法,石墨烯的尺寸从微米量级提高到毫米量级,面积提高了十万倍以上,产率大于95%,同时石墨烯依然保持着非常高的质量.这种新型机械解理方法具有良好的普适性,目前已经在包括MoS₂,WSe₂,MoTe₂,Bi2212等几十种材料体系中得到了毫米量级以上的高质量单层样品.更重要的是,在解理过程中,通过调控不同的参数,可以在层状材料中实现一些特殊结构的制备,如气泡、褶皱结构等,为研究这些特殊材料体系提供了重要的物质保障.未来机械解理技术还有很多值得深入研究的科学问题,该技术的突破将会极大地推动二维材料领域的研究进展.     

Magical Allotropes of Carbon: Prospects and Applications

The invention of carbon and its allotropes have transformed the electronic and optoelectronic industry due to their encouraging properties in a large spectrum of applications. The interesting characteristic of carbon is its ability to form many allotropes due to its valency. In recent decades, various allotropes and forms of carbon have been invented, including fullerenes, carbon nanotubes (CNTs), and graphene (GR). Since the inception of nanotechnology, carbon allotropes-based nanocomposites have become a leading sector of research and advancement due to their unique bonding properties. Fullerenes and CNTs-based polymer nanocomposites have attracted significant research interest due to their vast applications in every sphere of science and technology. Current research impetus reveals that carbon and its allotropes have revolutionized the industry and academia due to their fascinated properties. Recent advances in various aspects of graphene, CNTs, graphene nanoribbons, fullerenes, carbon encapsulates, and their nanocomposites with polymeric materials and their different applications are reported in this review article. Also, current status and future prospects of graphene-based polymer nanocomposites are presented in common along with proper citations extracted from the scientific literature. Moreover, this article is a unique collection of vital information about GR, CNTs, fullerenes, and graphene-based polymer nanocomposites in a single platform.     

Transfer-Free Graphene Growth on Dielectric Substrates: A Review of the Growth Mechanism

Ever since the more-than-decade-old discovery of application of mechanical exfoliation to obtain graphene, this 2-dimensional material was known for its soaring promise in various applications, owing to its excellent properties. Graphene, most popularly grown on metallic substrates by chemical vapour deposition, needs to be transferred onto dielectric substrates for multiple optical and electronic applications. During such complex and expensive transfer steps, defects are introduced into graphene, which deteriorates the quality and thus, properties of graphene. An alternative approach to surmount these problems is the elimination of the transfer process and to directly grow graphene on dielectric substrates, for future electronic and optical applications. This review presents a comprehensive and an up-to-date account of the development of synthesis methods, challenges and future directions for transfer-free graphene growth on dielectric substrates. Special emphasis is given on the fundamentals of growth mechanisms of various transfer-free graphene synthesis processes on dielectric materials.     

石墨烯射频器件研究进展

石墨烯因具有优良的电学特性,在半导体行业中受到广泛关注,特别因其具有超薄的结构和极高的载流子迁移率,为解决短沟道效应提供了可能,并且在高速电子领域具有应用前景.近年来,使用石墨烯作为沟道材料制备射频晶体管及射频电路是发挥石墨烯材料优势的一个重要研究方向.制造高性能的射频器件,首先要制备出高性能的石墨烯材料.在金属衬底上沉积均匀的单层石墨烯材料或者在绝缘衬底上外延生长单层、双层石墨烯材料都是获得高质量石墨烯材料的常用方法.器件结构及工艺流程的设计也是提升晶体管射频性能的重要因素,多指栅结构、T型栅结构、埋栅结构以及自对准工艺的发展能够有效改善石墨烯射频晶体管的截止频率及最大振荡频率.石墨烯晶体管独特的电学特性使得其除了可以构造与其他半导体材料电路相似的射频电路结构,还可以构造出功能完整并且结构更加简单的新型射频电路结构.     

氧化石墨烯的多色发光及其在荧光成像中的应用

氧化石墨烯作为石墨烯的一种带隙打开的衍生物,极大地丰富了其光学性质,并拓展了它在传感和成像方面的应用,特别是氧化石墨烯限域的π共轭结构对构建发光碳材料提供了十分便利的条件。目前,有大量的研究工作报道了氧化石墨烯及其衍生物能够产生多种颜色的荧光信号,然而,系统地总结这些研究去揭示氧化石墨烯发光机理的相关工作还比较少。本文总结了关于发光氧化石墨烯纳米材料的合成及其在光学成像方面应用的大量研究工作,为进一步开发新型的发光氧化石墨烯材料提供一些建设性意见。     

二维平面和范德瓦耳斯异质结的可控制备与光电应用

自石墨烯被发现以来,二维材料因其优异的特性获得了持续且深入的探索与发展,以石墨烯、六方氮化硼、过渡金属硫化物、黑磷等为代表的二维材料相关研究层出不穷.随着二维新材料制备与应用探索的不断发展,单一材料性能的不足逐渐凸显,研究者们开始考虑采用平面拼接和层间堆垛所产生的协同效应来弥补单一材料的不足,甚至获得一些新的性能.利用二维材料晶格结构的匹配构建异质结,实现特定的功能化,或利用范德瓦耳斯力进行堆垛,将不同二维材料排列组合,从而在体系里引入新的自由度,为二维材料的性质研究和实际应用打开了新的窗口.本文从原子制造角度,介绍了二维平面和范德瓦耳斯异质结材料的可控制备和光电应用.首先简要介绍了应用于异质结制备的常见二维材料的分类及异质结的相关概念,然后从原理上分类列举了常用的表征方法,随后介绍了平面和垂直异质结的制备方法,并对其光电性质及器件应用做了简要介绍.最后,对领域内存在的问题进行了讨论,对未来发展方向做出了展望.     

石墨烯纳米结构的制备及带隙调控研究

石墨烯在未来微电子学领域有极大的应用前景,但是其零带隙的特点阻碍了石墨烯在半导体领域的应用.研究发现,打开室温下可用的石墨烯带隙所需要的石墨烯纳米结构尺度在10 nm以下,这一尺度的纳米结构一方面制备比较困难,另一方面器件可承载的驱动电流较小.因此,如何实现亚10 nm石墨烯纳米结构的有效加工以及如何在有效调控带隙的基础上增大石墨烯器件可承载的驱动电流,还需要进一步的研究.本文首先研究了利用聚甲基丙烯酸甲酯/铬(PMMA/Cr)双层结构工艺,通过刻蚀时间的控制,利用电子束曝光及刻蚀工艺实现了亚10 nm石墨烯纳米结构的可控制备.同时设计并制备了单排孔石墨烯条带结构,该结构打开的带隙远大于相同特征宽度石墨烯纳米带所能打开带隙的大小.该结构在有效打开石墨烯带隙的同时,增加了石墨烯纳米结构可以承载的驱动电流,有利于石墨烯在未来微电子领域的应用.     

Large-area graphene synthesis and its application to interface-engineered field effect transistors

This article reviews recent advances in the large-area synthesis of graphene sheets and the applications of such sheets to graphene-based transistors. Graphene is potentially useful in a wide range of practical applications that could benefit from its exceptional electrical, optical, and mechanical properties. Tremendous effort has been devoted to overcoming several fundamental limitations of graphene, such as a zero band gap and a low direct current conductivity-to-optical conductivity ratio. The intrinsic properties of graphene depend on the synthetic and transfer route, and this dependence has been intensively investigated. Several representative reports describing the application of graphene as a channel and electrode material for use in flexible transparent transistor devices are discussed. A fresh perspective on the optimization of graphene as a 2D framework for crystalline organic semiconductor growth is introduced, and its effects on transistor performance are discussed. This critical review provides insights and a new perspective on the development of high-quality large-area graphene and the optimization of graphene-based transistors.     

Recent developments in hard magnetic materials

Summary Hard magnetic materials find ever-increasing uses in modern technology. Their importance is mainly in the domain of permanent magnets, but a variety of other applications is being offered to this class of materials, especially for what regards the areas of information storage, telecommunications and special electronic devices. These developments are connected to the emphasis that is more and more given to thin films having high magnetic anisotropy. The recernt advancement in the field of hard magnetic materials is among the best examples where technology depends to a great extent upon the continuous progress in the scientific knowledge. The research activity is characterized by the introduction of new classes of materials and continuous improvements in the preparation techniques both for what regards industrial processing and method for obtaining high quality materials in form of crystals, films or amorphous specimens. In this respect a special place must be reserved to rare earth transition metal compounds, a class of materals that attracted enormeous attention after the discovery by Hoffer and Strnat in 1966 of the large uniaxial magnetocrystalline anisotropy of the compound YCo₅. Beside the so called 1∶5 phase, other compositions of technical importance are the 2∶17 and the recently discovered Nd₂Fe₁₄B, which is a real new ternary phase having tetragonal crystal structure. Great efforts have been done to gain a better understanding of the magnetic anisotropy and its relationship to the coercivity is of leading importance for a further development in this important area of magnetism.     

Broadband tunability of surface plasmon resonance in graphene-coating silica nanoparticles

Graphene decorated nanomaterials and nanostructures can potentially be used in military and medical science applications. In this article, we study the optical properties of a graphene wrapping silica core–shell spherical nanoparticle under illumination of external light by using the Mie theory. We find that the nanoparticle can exhibit surface plasmon resonance(SPR) that can be broadly tuned from mid infrared to near infrared via simply changing the geometric parameters. A simplified equivalent dielectric permittivity model is developed to better understand the physics of SPR, and the calculation results agree well qualitatively with the rigorous Mie theory. Both calculations suggest that a small radius of graphene wrapping nanoparticle with high Fermi level could move the SPR wavelength of graphene into the near infrared regime.     

Synthesis of reduced graphene oxide and enhancement of its electrical and optical properties by attaching Ag nanoparticles

Graphene has attracted the attention of the scientists and researchers because of its peculiar properties. Because of various unique properties, graphene can be used in sensing device applications, solar cells and liquid crystal display devices etc. In this research paper, we present a chemical route towards bulk production of r-GO (reduced graphene oxide). We have employed a modified method to achieve better results which is often termed as modified Hummer's and Offeman method. It is modified in terms of filtration technique. We have also attached silver nanoparticles (Ag-NP) to as synthesised r-GO. After successful growth, silver nanoparticles have been attached to r-GO by suitable treatment with AgNO₃ (aq.) N/50 solution. The as grown samples were characterised by FESEM, Raman Spectroscopy and EDS to make sure that r-GO and r-GO–Ag-NP have been successfully synthesised. The electrical and optical studies of the as grown samples were performed by dc conductivity measurements and UV visible spectroscopy. The conductivity was found to have increased with attachment of Ag-NP. The optical transmittance also improved to 90% as against 70% before Ag-NP attachment. The reduced graphene oxide attached with silver nanoparticles could find promising applications in synthesis of transparent electrode materials and optoelectronic devices.     

石墨烯/聚乙撑二氧噻吩薄膜储能特性（英）

为了有效利用石墨烯和导电聚合物材料,光雕石墨烯/聚3,4-乙撑二氧噻吩(LSG/PEDOT)复合薄膜通过一种灵巧的光雕工艺制备出来。在此复合薄膜中,每种组分对薄膜的电化学性能提升都有独特的贡献。循环伏安、交流阻抗及恒流充放电测试用来检测薄膜的电化学性能。结果显示,在引入PEDOT纳米颗粒后,LSG/PEDOT复合薄膜显示出更好的能量存储能力。复合薄膜的比容量达到64.33 F/cm3,是光雕石墨烯比容量(3.89 F/cm3)的20倍,复合薄膜经过1000次循环后仍能保持初始容量的94.6%。复合薄膜电化学性能的提升主要是由于引入的PEDOT纳米颗粒既阻挡了石墨烯的层层堆叠,又增加了整个薄膜的比表面积。此种灵活的光雕工艺还可以用来大规模制备超级电容器电极。     

Graphene in high magnetic fields

Carbon-based nano-materials, such as graphene and carbon nanotubes, represent a fascinating research area aiming at exploring their remarkable physical and electronic properties. These materials not only constitute a playground for physicists, they are also very promising for practical applications and are envisioned as elementary bricks of the future of the nano-electronics. As for graphene, its potential already lies in the domain of opto-electronics where its unique electronic and optical properties can be fully exploited. Indeed, recent technological advances have demonstrated its effectiveness in the fabrication of solar cells and ultra-fast lasers, as well as touch-screens and sensitive photo-detectors. Although the photo-voltaic technology is now dominated by silicon-based devices, the use of graphene could very well provide higher efficiency. However, before the applied research to take place, one must first demonstrates the operativeness of carbon-based nano-materials, and this is where the fundamental research comes into play. In this context, the use of magnetic field has been proven extremely useful for addressing their fundamental properties as it provides an external and adjustable parameter which drastically modifies their electronic band structure. In order to induce some significant changes, very high magnetic fields are required and can be provided using both DC and pulsed technology, depending of the experimental constraints. In this article, we review some of the challenging experiments on single nano-objects performed in high magnetic and low temperature. We shall mainly focus on the high-field magneto-optical and magneto-transport experiments which provided comprehensive understanding of the peculiar Landau level quantization of the Dirac-type charge carriers in graphene and thin graphite.     

Realization of Graphene Physics Through a Fully Optical System

The two-dimensional form of carbon known as graphene awaken the scientific community interest due to its exotic electronic properties, emerging from the behavior of electrons near the Fermi level as massless Dirac fermions in a (1+2)-dimensional “relativistic” space-time, which renders a bridge between condensed matter and relativistic quantum field theory. Optical systems are also prodigal in providing analogues of complex quantum mechanical systems. Here, it is proposed an optical realization capable of capturing the essential physics of the Dirac equation in (1+2)-D dimensions, simulating the properties of graphene through the use of lightwave technology.     

Graphene enterprise: mapping innovation and business development in a strategic emerging technology

This paper explores enterprise development and commercialization in the field of graphene. Firm characteristics and relationships, value chain positioning, and factors associated with product entry are examined for a set of 65 graphene-oriented small and medium-sized enterprises located in 16 different countries. As well as secondary sources and bibliometric methods to profile developments in graphene, we use computerized data mining and analytical techniques, including cluster and regression modeling, to identify patterns from publicly available online information on enterprise web sites. We identify groups of graphene small and medium-sized enterprises differentiated by how they are involved with graphene, the materials they target, whether they make equipment, and their orientation toward science and intellectual property. In general, access to finance and the firms’ location are significant factors that are associated with graphene product introductions. We also find that patents and scientific publications are not statistically significant predictors of product development in our sample of graphene enterprises. We further identify a cohort of graphene-oriented firms that are signaling plans to develop intermediate graphene products that should have higher value in the marketplace. Our findings suggest that policy needs to ensure attention to the introduction and scale-up of downstream intermediate and final graphene products and associated financial, intermediary, and market identification support. The paper demonstrates novel data methods that can be combined with existing information for real-time intelligence to understand and map enterprise development and commercialization in a rapidly emerging and growing new technology.     

Measuring science–technology interactions using patent citations and author-inventor links: an exploration analysis from Chinese nanotechnology

This article contributes to the growing study on the interactions between science and technology with China’s evidence in the field of nanotechnology, based on the database of United States Patent and Trademark Office. The analysis is focused during the period of 1991–2008, a rapid increasing period for the development of nanotechnology. Using the non-patent references cited by patents, we first investigate the science–technology connections in the context of Chinese nanotechnology, especially in institutional sectors and its application fields. Those patents, produced by academic researchers and directed towards basic scientific knowledge, generally cite more scientific references with a higher proportion of self-citations. It is interesting to find that patents contributed by collaborations between public organizations and corporations seldom contain scientific references. Following an interesting path on matching the data of publications and patents, we establish the author-inventor links in this emerging field. Author-inventors, who are co-active in publishing and patenting, are at the very top of the most prolific and highly cited researchers. Finally, we employ social network analysis to explore the characteristics of scientific and technological networks generated by co-authorship and co-invention data, to investigate the position and the role of patenting–publishing scientists in these research networks.     

A survey on HHL algorithm: From theory to application in quantum machine learning

The Harrow-Hassidim-Lloyd (HHL) algorithm is a method to solve the quantum linear system of equations that may be found at the core of various scientific applications and quantum machine learning models including the linear regression, support vector machines and recommender systems etc. After reviewing the necessary background on elementary quantum algorithms, we provide detailed account of how HHL is exploited in different quantum machine learning (QML) models, and how it provides the desired quantum speedup in all these models. At the end, we briefly discuss some of the remaining challenges ahead for HHL-based QML models and related methods.