Abstract: graphene is the thinnest and hardest nanomaterial known in the world. Its appearance has aroused wide discussion in academic circles. Graphene has been found to be unusually conductive, exceeding steel's dozens of times strength and excellent transmittance, and its emergence could lead to a revolution in modern electronics technology. Graphene is a crystal with only one atom thick, which has the characteristics of ultra-thin, ultra-strong and ultra-strong conductivity. Its excellent electrical, thermal and mechanical properties, and its potential application value in nano electronic devices, energy storage materials, photoelectric materials and other aspects, have caused a new round of "carbon" craze in the scientific community.
Structure and properties of graphene
Graphene is the thinnest and most solid material known. It is a two-dimensional, single-layer graphite tightly arranged by the hexagonal structure of carbon atoms. It is the basic unit for constructing other dimensional carbon materials. The structure of graphene is very stable, and the connections between the carbon atoms in it are very flexible. When external mechanical forces are applied, the carbon atomic surface will be bent and deformed, so that the carbon atoms do not have to be rearranged to adapt to external forces, and the structure remains stable. This stable lattice structure gives carbon atoms excellent conductivity.
Preparation of 2 graphene
The preparation of graphene is mainly based on the following two principles: one is to take graphite as raw material, and to peel graphene by weakening and destroying the van der Waals force between graphene layers; the other is based on the directional assembly of activated carbon atoms, which "limits" the growth of carbon atoms along the plane direction. Therefore, the preparation methods commonly used nowadays are mainly divided into physical and chemical preparation. Physical methods mainly include: micro-mechanical stripping, seal cutting transfer printing, template method, chemical methods mainly include: REDOX method, solution stripping method, heating SiC method, chemical meteorological deposition method and so on.
Application of graphene
(1) application of graphene in analytical science
Graphene has a wide range of applications. First, the applications of graphene in analytical science are reviewed. Because graphene has a large specific surface area and is an electron-rich hydrophobic material, it is very suitable as an adsorbent for solid phase extraction. With the deepening of graphene research, especially the development of functional modification methods, graphene will become another new material for sample pretreatment after carbon nanotubes. Because graphene has unique structure and electronic properties, it has good application prospects in fluorescence spectrum analysis.
(2) application of graphene in nanoelectronic devices
In 2005, Geim team with Kim team found at room temperature of graphene has 10 times the commercial silicon high carrier mobility, and is affected by temperature and doping effect is very small, showing the ballistic propagation properties of room temperature submicron scale, this is the most prominent as the nano electronic devices graphene advantage, make the electronic engineering field attractive ballistic field effect tube at room temperature. Dutch scientists reported on the first graphene-based superconducting field-effect tube, and found that graphene can still transmit a certain amount of current at zero charge density, which may lead to a breakthrough in low energy consumption and fast switching time of nanoscale superconducting electronic devices. Compared with one-dimensional nanomaterials, the significant advantage of graphene-based electronic devices is that the whole circuit, including conductive channels, quantum dots, electrodes, potential barrier, molecular switches and connectors, can be obtained on the same piece of graphene, which may avoid the difficult integration problems in one-dimensional material-based devices. At present, IBM, lntel and other companies have invested heavily in the application of graphene in nano electronic devices.
(3) application of graphene materials in the field of electrochemistry
Carbon materials are the earliest studied and commercialized cathode materials for lithium ion batteries, and are still one of the focuses of attention and research. Graphene, as a new type of carbon materials prepared from graphite, has the potential of single-layer or thin-layer graphene application in lithium ion batteries. Because of graphene has special atomic structure and electronic structure, make its have some structure in composite material and performance advantages, especially in ACTS as an anode material in lithium-ion batteries, in the process of lithium ions to take off the plug, can to a certain extent, the buffer material volume "telescopic movement", extend the cycle life of the material to enhance its performance. The above research indicates that although graphene-based composites are still in the research stage, they have a good application prospect in lithium ion battery cathode materials. Carbon materials are the earliest and most widely used super capacitor electrode materials. Since the successful preparation of graphene, the possibility of using the sp2 carbon material in supercapacitors has been explored. Experiments have shown that the pores formed during the superposition of graphene sheet to form macroscopic bodies are concentrated at more than 100mm, which is conducive to the diffusion of electrolyte.
(4) other potential applications of graphene
With the development of low cost and large scale production technology of graphene, many applications have appeared one after another, and more and more attention has been paid to them. Among them, composites are one of the most promising applications of graphene. Graphene has excellent hydrogen adsorption and is expected to be used in hydrogen storage materials. For example, in 2006, Ruoff's team reported in Nature that the first graphene-based composite had a seepage threshold similar to that of the nanocarbon pipe polystyrene composite, with high thermal conductivity and high strength, and could be made into conductive plastics for heat dissipation in solar panels or computers. Recently, the team has used fluid-oriented methods to assemble discrete graphene oxide into high strength, high hardness and high toughness paper materials, laying the foundation for its applications in supercapacitors, molecular storage materials and permeable membranes with controllable performance. In addition, graphene is expected to be widely used in field emission materials, quantum computers and ultra-sensitive sensors due to the thickness of atomic scale, excellent electrical quality, extremely weak spin-orbit coupling, lack of ultra-fine interaction, and the sensitivity of electrical properties to external fields. Schedin et al. made the first chemical sensor to accurately detect individual gas molecules using graphene, greatly improving the sensitivity of rapid detection of trace gases.