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Graphene (Graphene) consists of a single layer of carbon atoms to form a new type of two -dimensional bees nest construction materials. 2004 , AKGeim England Manchester University team lead with tape stripping method was prepared by mechanical single-atom thick layer of graphene and found that it has electric controlled carrier performance. Its discoverer AK Geim and K. Novoselov for the discovery of graphene and its unique electrical properties and the 2010 Nobel Prize in Physics . Simple naming into graphene (graphene), bilayer graphene (bilayer graphene), less layer graphene (Few layer graphene ,2-5 layers ) , multilayer graphene (Multilayergraphene, 5-10 layer ) , graphite ene microchip (Graphene nanoplatelet), collectively referred to as graphene -related materials (Graphene nanomaterials).
Graphene has excellent electrical properties, the temperature of the carrier mobilities of up to 105cm2 / V × s, Si electron mobility is 100 times and 300 times the hole mobility , the carrier concentration from 0-1013/cm2 height adjustable, current-carrying ability超过108 A/cm2, is a thousand times more copper. Saturated drift velocity of up to 108 cm / s (Si 6 to 7 times ) ; graphene thermal conductivity of up to 5000 W / m ∙ K, three times at room temperature for pure diamond ; graphene from UV- visible to near -infrared a wide range of wavelengths of light have excellent 97% light transmission. Graphene mechanical strength up 130 GPa; large specific surface area ~ 2600 m2 / g, a wide electrochemical window . Compared with the traditional two-dimensional electron gas semiconductor graphene is truly one-atom -dimensional electron system , the zero band gap energy band structure, with a neutral point (Dirac point ) , the Dirac point , the electronic performance massless relativistic Dirac fermion behavior that is unique linear energy dispersion relation . Graphene triangular lattice crystal structure composed of two carbon atoms , the wave functions of two components , electrons and holes have opposite chirality. Carriers in graphene through a vertical barrier with full transmission of Klein tunneling behavior. The bottom-up method is considered to be one of the future nano- constructed electronic circuit of the most promising materials in the future is expected to speed nanoelectronics , optoelectronic devices , energy conversion devices, functional components of the composite filler , biochemical sensors and other aspects of the application . Graphene unique structure and excellent performance makes it possible to obtain a significant practical applications in many fields, providing a powerful new growth point for future economic and social development , the scope of application covering energy, environment , information, biomedical , new materials and other fields , particularly in the automotive , electronics , aerospace, medical and other industries.
2010 Nobel Prize winner in physics AK Geim and K. Novoselov
1、An international research projects related to the direction of developed countries and research specific hot spots:
Graphene its superior variety of electrical, thermal, and mechanical properties has caused a tremendous passion for the international development of the industry as a new energy and new materials in a new generation of information technology has a very important application prospect. Graphene as an industrial base material to play a variety of superior performance, will inevitably lead to changes in the entire human industrial system, whether it is new energy, electronic information, consumer electronics (flexible displays), military aerospace equipment in its coverage of in the United States, Europe, Japan, Korea, Singapore and other government agencies, many famous universities, research institutions and industry to invest heavily in research and development of graphene field.
In 2011, the media reported the EU launched the "flagship" plans to invest 1 billion euros, focusing on graphene preparation and application of information and communication technology. Including 130 research team. Based on the order in which the same from Chalmers University team led by nine first implementation of graphene-CA plans to May 1, 2011, based on both traditional and new information and communication technologies, the development of graphene in which the potential applications, understanding of the characteristics of graphene and graphene preparation techniques to master. In 2011, the British government announced £ 50 million investment in the establishment of Graphene Global Research Technology Center at the University of Manchester, aims to develop new graphene technology applications.
U.S. military and major companies such as IBM, Intel, 3M, SEMATECH also has an associated project. Some industry invested heavily in the establishment of a number of companies engaged in large-scale preparation of graphene powder and film, as well as applications in electronics, energy fields. IBM and Berkley in graphene-based integrated circuits, high-frequency FET amplifiers, broadband high-speed optical modulators and photodetectors aspects of the layout and carry out research and development related projects. In addition, graphene nanoribbons has a unique energy band structure and the nature of the edge states has important potential applications in electronics, optoelectronics and spintronics, the United States and France in the preparation of graphene nanoribbons and electron spin device applications launched a three-year collaborative research.
Asia, except for China, including Korea, Japan and Singapore, they intensify start preparation of graphene from graphene to carry out a number of applications. Which the South Korean government, businesses and individuals plan the next six years, $ 200 million into the budget, in addition, also plans to invest several hundred million dollars to graphene-related research institutions from nine aspects of the full implementation of graphene applications, including graphite alkenyl touch screen, an organic light emitting diode, smart windows, secondary batteries, super capacitors, composite materials, high performance gas barrier film, a battery, and iron oxidation mask layer. Singapore plans to invest $ 50 billion in 2020 in terms of a transparent conductive coating. From 2010 graphene research center was established, has invested $ 100 million.
Graphene Applications (Source: Nanowerk) and graphene market expectations (source, BCC research)
2. the status of various research and technology development trends
(1) large-scale preparation and electrical conductivity, thermal conductivity applications
Several techniques have been prepared graphene materials: mechanical peeling , epitaxial growth , CVD and liquid-phase chemical, thermal expansion or the like. However, to date , these methods are graphene certain disadvantages. Mechanical peeling method to obtain a different number of layers of graphene sheet , with high quality but can not be achieved for mass production. SiC epitaxial graphene grown , high quality can be obtained , the larger graphene substrate but expensive to produce graphene substrate is influenced by the performance of the peeling difficult. Large area can be synthesized using CVD graphene film with obvious advantages in terms of production of the device , but is also limited by the amount of production of the CVD apparatus and a thin film structure , while the uniformity to be improved . Phase chemical synthesis of graphene can scale synthesis, and to achieve dispersion of the aqueous solution and preservation , however , the defects caused during the synthesis and oxygen-containing group , resulting in poor electrical performance. Rapid thermal expansion of the thin layer to obtain a large number of graphene sheets , but the use of expanded graphite starting materials are oxygen-containing functional groups , obtained by thin-layer graphene sheet also has oxygen-containing group , the conductive performance is not satisfactory .
Currently, the U.S. has become Vorbeck Materials, XG Sciences, AngstronMaterials, were announced to achieve several tons / year capacity . Britain set up the Graphene Industries Limited company . China has also established a number of graphene preparation and application of industrial development of the company. Although the application of export graphene remains to be clear, but these companies to carry out industrial -scale preparation , looking for industrial applications of graphene first step . However , the size of the graphene prepared by these companies are also limited to micro graphene sheet thickness ( a few nanometers thick) , and the reduction of graphene oxide . Thus , an inevitable trend in controllable preparation of graphene are the following : ( 1 ) macro preparation of thin, high-quality graphene powder ; ( 2 ) a large area , high quality , layers of graphene films can be controlled control equipment ; ( 3 ) for different application requirements, to achieve size control, control, preparation of functionalized graphene modulation band . ( 4 ) the edges smooth , high-quality graphene and graphene nano patterning technology zone.
Grenada HSBC team and domestic teams in the field of graphite ene progress
(2) application of optoelectronic devices and information and communication
Because of its unique graphene Sp2 structure having excellent electrical and optical properties, the temperature up to the intrinsic mobility of 105 cm2 / V × s, the carrier type, concentration height adjustable . Optics , ultraviolet, visible, near -infrared wavelength range is very wide have excellent light transmittance , such as graphene band in the visible light transmittance was 97.7%. Thus , carbon nanomaterials have important applications in high-frequency electronics, broadband optoelectronic devices in the future , become an important material for the next generation of IT systems .
Graphene has rapidly controlled electric Fermi energy regulation , enabling the absorption of light reaching the light amplitude adjustment control function , the advantage is that it can achieve broadband , the process is simple , stable temperature performance. With its materials, optimization, performance of the device, will play an important role in high-speed optical interconnects in next generation broadband . IBM researchers have successfully developed a cutoff frequency up to 100 GHz RF graphene transistors , the project is the U.S. Defense Advanced Research Projects Agency "Carbon Electronics for RF Applications Project ", the progress of research and development of next-generation communication devices paved the way. University of California , Berkeley research team used Zhang Xiang Si waveguides in graphene has been initially achieved modulation speed of 1GHz . Production process is simple, performance improvement potential. However , with graphene theoretical achievable performance indicators are still far away .
Using light with a strong interaction of graphene, a high performance high transconductance graphene electron temperature, the hole mobility and the characteristics of graphene device, through the graphene structure, band regulation, and graphene and metal touch-control electrode, the development of next-generation optical communications room temperature infrared, THz detectors. IBM in 1.5mm optical communications band to achieve a 0.2 mA and 10Gbit / s photocurrent detection. These advances make up for the high-speed infrared conventional semiconductor defect THz detector aspects play an important role. However, the light and the dark current response rate targets to be further improved.
Therefore, the design of new optoelectronic devices and the development of new optoelectronic devices based on graphene technology to improve performance in high-frequency graphene optoelectronic devices, as well as conduct graphene nanoribbons transistor performance, the new electronics (Valley Electronics) , spintronics devices, is an important trend in graphite ene development.
(3) graphene energy storage, sensing applications
Due to the large specific surface area and high electrical conductivity , graphene has important applications in supercapacitors . R. Ruoff team first produced a reduction of graphene oxide -based super capacitors, Tianjin University, Chen Yongsheng team after redox graphene supercapacitor aqueous phase than the capacity up to 205 F / g, Li Dan team will wet graphene Supercapacitors film used high power density obtained was 777 kW / kg ( ionic liquid ) and 414kW/kg ( aqueous phase ) , the energy density of 150.9 Wh / kg ( ionic liquid ) . Recently R. Ruoff group also in the reduction of the alkylene oxide graphite punch to give excellent performance supercapacitor having ultrahigh surface area graphene (3100 m2 / g), and obtained . More progress in Table 1. Graphene is currently visible in the super capacitor application is mainly the reduction of graphene oxide . However, reduction of graphene oxide is introduced in the process of making a large number of hetero atoms and defects , the conductivity was lower than the intrinsic graphene , but also greatly affect the ratio of the capacitance of supercapacitors and cycle stability. At the same surface area, high-quality defect-free graphene was superior in the reduction of the conductive graphene oxide , and therefore whether the macro preparation is the key to the future of high-quality graphene Graphene storage device performance improvement .
Lithium-ion batteries have a high open-circuit voltage , energy density, long life , no memory effect , no pollution , and self-discharge rate , etc, quickly became one of a new generation of research and development in recent years, a secondary battery . According to IHS 's batteries special report , because the price is gradually becoming low , and demand from the electric and hybrid car market , driven to become the world's leading lithium-ion rechargeable battery technology. The new two-dimensional material graphene discovery of lithium-ion batteries broader application has opened up a new path. Ohio Nanotek Instruments researchers used a large number of lithium ions can rapidly shuttle between the movement characteristics and the electrode surface of the graphene , the development of a new energy storage device , the ratio of the new battery power 100 kW / kg, compared commercial lithium-ion battery high 100 times, 10 times higher than the super capacitor . The new lithium battery charging time will be less than 1 min, the electric car can be fully charged battery life over hundreds of kilometers . This is undoubtedly a great way to break the existing battery charging time is too long endurance short application bottlenecks, and this will undoubtedly promote the development and popularization of electric vehicles .
Development of high-performance , flexible storage , sensing is an important development trend of graphene applications to replace conventional ITO transparent conductive films and flexible flexible sensors, capacitive battery put forward new demands . Early work has demonstrated an important basis of the nano -carbon material in these areas will be based on this , while focusing on the development of nano -carbon material having a large area of the transparent conductive film and the conductive properties of the ink , combined printing , coating film processing techniques , etc. development of low-cost carbon nanotubes or graphene transparent conductive film to achieve its practical application in the smart Touch devices ; detection technology using micro- nano nano-carbon material morphology, stress , life and other performance lithium storage in a unique test ; combination of traditional micro- nanofabrication means to achieve flexible sensor and battery , a capacitor element , is an important application of emerging nano-carbon material information in the next generation , the environment, energy in .
( 4 ) conductive ink printed electronics applications
Printed electronics since found so far , with its extremely low cost and fast processing methods combining printed to promote the formation of relevant professional industries , development and progress . Currently many emerging companies and well-known foreign companies have given the film printed electronics industry a great deal of attention. Because graphene has high electrical performance , high mechanical strength , good flexibility , chemical stability, and good light resistance, so that graphene is very suitable as a conductive additive to the emerging conductive ink , thereby promoting the printed electronics further development of the industry. Andrea Ferrari of Cambridge University , led the research team for the first time with an ordinary printer to print out the graphene film circuit , its mobility reached ~ 95cm2V-1s-1, higher than the conductive polymer 0.02-0.5 cm2/Vs, its stability has also been greatly improved. Korea Jyongsik Jang et al inkjet print restored graphene oxide (rGO) demonstrates the 500 MHz dipole antenna RFID Performance (Adv. Mater. 2011, 23, 2113), they are also used printing method to achieve a transparent graphene electrodes speaker (Chem. Comm. 47, 8527 (2011)). The new material can also create an important role in promoting flexible displays play . In recent years , Vorbeck Materials Corporation and Innophene new companies are committed to the development of graphene preparation and application of conductive ink , and is expected to achieve a breakthrough in the preparation of graphene-based smart label printing ink applications . Vorbeck last year graphene production start plan conductive ink , they found that with Vor-ink and the conductor circuit composed of graphene fully integrated , it shows a competitive price excellent conductivity , and may also get bent wrinkled not damage the circuit , can be widely used in anti-theft packaging. Based on MD-Vorbeck Materials plans to begin production in late 2011 the first graphene -based conductive ink for stamping on the RFID antenna substrate . Domestic graphene-based electronics is still in print laboratory research stage , the scale has not yet formed .
( 5 ) graphene transparent conductive film and touch system applications:
In the development process of graphene thin films , the 2004 University of Manchester Geim group first got graphene films using mechanical exfoliation method , the disadvantage is only get micrometer -sized graphene films , therefore only suitable for laboratory research , not industrialized mass production. In 2008 , the University of Houston first officially released by chemical vapor deposition (CVD) method on nickel and copper base growth method for the synthesis of graphene , and successfully grown the world's first large-size , high-quality graphene films . In December MIT MIT researchers have published a growing CVD method using graphene on a nickel substrate . Then Dr. BH Hong 2009年Sungkyunkwan University , the University of Texas at Austin , Dr. R. Ruoff 's team have also reported the results after further optimization of the growth conditions . 2010 Samsung , the first graphene thin film materials used in touch technology , the introduction of graphene resistive touch screen .
Currently, the latest trends in graphene films are as follows: high-quality transparent electrode material requirements to ensure high transmittance also have low sheet resistance of ITO films for industrial use different materials depending on the requirements , the sheet resistance of 200 to 1000 ohms , the transmittance of 80 % ~ 90% ( data are from publicly reported ) . Therefore , the graphene film material must also meet these two indicators to adopt in touch technology .
3、Each application prospect of future research directions
According to Lux Research 2009 Report, 2008 Graphene market $ 196,000, up $ 59 million in 2015, the relevant product market is expected to reach $ 53 billion, will be widely used in energy, automotive, aerospace, electronics, display, medical and other fields.
(1) large-scale preparation and electrical conductivity, thermal conductivity applications
Preparation of low-cost high-quality graphene breakthrough macro after the amount of preparation, due to its excellent electrical conductivity, thermal conductivity, mechanical properties, graphene as the application of new materials: graphene itself and add material as a composite system, play a mechanical, electrical, thermal enhanced role in the electrical conductivity, thermal conductivity, antistatic, electromagnetic shielding, mechanical enhancements, and many other important applications.
(2) application of optoelectronic devices and information and communication
In the field of microelectronics materials for devices with high-frequency, high-speed, low power consumption, miniaturization, high integration and other performance requirements escalating and silicon material itself lower carrier mobility and the limits of silicon transistors processed restrictions, an urgent need to develop a higher mobility as well as new material system is compatible with planar technology device processing techniques to solve the bottleneck problem faced by the further development of the integrated circuit chip performance and power of mutual restraint. Carbon-based materials and carbon-based electronic devices are expected to complement traditional Si and III-V group semiconductor device and circuit performance. Electronics, graphene-based optoelectronic devices is expected in the high frequency FET amplifier member, the graphene-speed broadband optical modulator and infrared, THz light detector having important applications.
( 3 ) graphene energy storage, sensing applications
Method to obtain a large number of high quality graphene graphene for achieving significant in terms of energy storage applications , such as improving the reversible specific capacity , rate capacity , improved cycle stability . Currently in redox graphene in lithium-ion battery system, redox graphene as a lithium-ion battery anode , poor conductivity, structural defects are more restricted further improved lithium-ion battery capacity and cycle performance. Application of high-quality graphene research on lithium-ion battery has only just begun , very little experimental work has been reported in the international arena . Mainly based on the use of high-quality graphene prepared by CVD , found graphene layer graphene with less lithium storage mechanism is different. Since the presence of a lithium -ion adsorption after Coulomb repulsion , resulting in a large specific surface area not larger graphene and graphene layers is less than the specific capacity . Thus high-quality thin-layer graphene sheet , due to the difficult preparation , the current lithium reserves or for inter-layer edge and surface adsorption and who dominated with a thin layer of graphite structure-activity relationship is unclear.
Emerging graphene is a two-dimensional honeycomb structure of carbon atoms to form a hybrid formed SP2 , all atoms are in the graphene surface having a large surface area , to maximize adsorption of gas molecules having excellent graphene conductivity , the unique two-dimensional structure to make it compatible with existing micro-machining processes. Relative to the carbon nanotubes, graphene has a larger specific surface area and low cost , easy to disperse and other advantages , so Graphene is a promising material gas response , graphene-based gas sensors become a hot topic .年2007, Geim first group prepared graphene monomolecular NO2 sensor (NatureMaterials 6, 652 (2007)), so far , to detect NH3, H2, O2, H2O , etc. have been reported graphene sensor (Nano Letters 9, 1472 (2009); ACS Nano 3, 301 (2009); Advanced Materials, ASAP (2010); NanoLetters 8,3137 (2008)). We propose to use graphene-based sensors, optimizing the device structure , based on direct measurement of NO graphene to achieve room temperature , high sensitivity , low power , portable gas sensors , the project early on to improve breathing sensor sensitivity and asthma attacks diagnosis has important scientific and practical value .
( 4 ) conductive ink printed electronics applications
An ink-jet printing technology is an effective method capable of shape , size, thickness, control controllable printing print patterns . Several conductive ink material making metal nanoparticles , carbon-based semiconductor material and a conductive polymer . Metal nanoparticles having a good conductivity, the relatively high cost and easy oxidation. Conductive polymer has the advantage of flexible handling and lower conductivity. The carbon nanomaterials with a wide range of raw materials , good conductivity and other advantages, is a great potential for application to print electronic materials. NanoMarkets forecasts printing ink in 2017 based nano-carbon materials have to reach nearly $ 815 million U.S. dollars .
(5) graphene transparent conductive film and touch system applicationsGraphene transparent conductive film for its excellent electrical conductivity , transmittance and flexibility, and low manufacturing costs and potential for recovery of green will replace the current mainstream transparent electrode material ITO film. Indium tin oxide ITO glass , indium as rare metal reserves are limited , and has a strong toxicity , with the continuous expansion of the touch screen industry, which led to increased consumption , raw material costs continue to rise, as countries control the exploitation of rare elements , will enable industry large-scale use sector gradually restricted. Preparation of graphene films simple , adequate materials and easy to recycle , environmental friendly. Graphene films can replace existing indium tin oxide (ITO) transparent electrodes applied to the new information terminals , solar cells, electronic paper, smart glass, organic LED and other areas , especially with its unique advantages in flexible electronic devices .
Graphene Application Roadmap (Nature 490, 192 (2012)
4. our current research status and development level
In recent years, the country has made in the preparation of graphene great progress , as well as basic research applications in energy , there are some good progress . In 2011, the CAS Shenyang metal , a research group will next use nickel foam as a template system out of the world's first three-dimensional structure of graphene new demo material with polymer composites with good mechanical and electrical properties . (Nat. Mater.10 ,424-428 (2011)). They DICP collaboration with the research team , made significant progress in the preparation of large single crystals and thin films of graphene and lossless transfer of (Nat. Commun. 1702 (2012)). They propose the use of the precious metal platinum as a growth substrate to achieve the preparation of millimeter -sized hexagonal single crystals of graphene in 2011 , Peking University, Academician Liu Zhong-Fan Study Group on non-noble metal substrates grown by segregation graphene chip size , and a detailed report segregation mechanism of graphene growth (Nano Lett. 11, 297-303 (2011). recent research team has grown 100% coverage of graphene on a nickel -molybdenum alloy (Nat. Commun. 2,522 ( 2012 ) ) . early Dalian Institute of Chemical Physics, Chinese Academy of Sciences research group package letter and academicians as silicon carbide carbon graphene (Adv. Mater., 22, 2168 (2010)), in addition to Ru as a catalyst for the growth of graphene important progress mechanism (J. Phys. Chem. C, 116, 2988 (2012)) and its use as a template for graphene supported catalysts (Angew. Chem.-Int. Edit., 50, 10236 (2011)) , etc. . Institute of Physics Gao Hongjun research group in the world's first single-crystal Ru Ru (0001) Preparation of high-quality single-crystal graphene films (Chin. Phys.16, 3151 (2007), Adv. Mater. 21, 2777 (2009) ) , get international attention . Tsinghua stone high full team graphene chemical synthesis and functional aspects engaged in a series of studies (ACS Nano 4, 1963-1970 (2010), J.Am.Chem.Soc. 131 ,13490 -13 497 ( 2009 ) ) , progress has been made , especially in graphene reinforced polymer composites, graphene modified electrode and conjugated molecules modified graphene , etc. in 2009, Tianjin University, Chen Yongsheng team will redox graphene the aqueous phase than the capacity of ultracapacitors 205F / g. (J. Phys.Chem.C, 113, 13103-13107 (2009)). they also designed and prepared to SPFGraphene as an electron acceptor , with a bulk heterojunction structure organic solar cells, photoelectric conversion efficiency under air conditions up to 1.4% of the team in Suzhou Institute of Nano -controlled graphene layers , graphene - Preparation and properties of optical thin-film semiconductor quantum dots composite system (Advanced Materials 22,638 (2010), Advanced Functional Materials 2012, AppliedPhysics Letters 2012), highly sensitive chemical sensor graphene production (ACS Nano 5,6955 (2011)), as well as an infrared light detector graphene transparent conductive film (NanoscaleResearch Letters, 6, 250 (2011)) made a series of research progress . In terms of domestic graphene prepared by the basic realization of some preliminary research progress in the preparation of sync with the international ink progress has been made , Liu Qi, a researcher of the Institute of Chemistry , etc. using the " coffee ring exposure " approach to achieve a high-resolution large-area graphene inkjet printing patterning (Adv. Mater. 24, 436 (2012)). Tianjin Nankai University, Professor Chen Yongsheng , such as the use of redox prepared graphene conductive ink , and printing method demonstrates the circuit and functional graphene -based chemical sensors for (Nano Res 2011, 4 (7):. 675-684675). These studies help scientists to break out a large-scale low-cost manufacturing of electronic equipment flexible wearable .
In summary , the domestic research institutes and universities has been considerable research on deep technical accumulation graphene . From the quality and quantity of published articles point of view, is not inferior to the well-known research groups in the world, and even beyond and reach the world advanced level in some areas. However , large-scale preparation capabilities, and industrial applications of graphene -based high-quality graphene in the country still remains to be improved.