graphene
graphene
CAS: 1034343-98-0
Molecular Formula: CH4
graphene - Names and Identifiers
graphene - Physico-chemical Properties
| Molecular Formula | CH4 |
| Molar Mass | 16.04246 |
| Density | 2.259 at 20℃ |
| Water Solubility | Insoluble in water |
| Appearance | powder |
| Color | transparent |
| Odor | Transparent |
| Storage Condition | Room Temprature |
| Sensitive | light sensitive, store cold |
graphene - Risk and Safety
| HS Code | 38019090 |
graphene - What is graphene?
Graphene, also known as "single-layer graphite sheet", refers to a layer of dense, wrapped in the honeycomb crystal lattice of carbon atoms, carbon atoms arranged in a two-dimensional structure, similar to the single atomic layer of graphite.
In 2004, the discovery of graphene with a two-dimensional structure overturned the understanding that "Thermodynamic fluctuations do not allow two-dimensional crystals to exist freely at a finite temperature" and shocked the entire physical world, its discoverer, Geim and Novoselov from the Department of Physics and Astronomy at the University of Manchester, UK, was also nominated for the Nobel Prize in Physics in 2008. Compared with carbon nanotubes, graphene has a perfect hybrid structure, large conjugated system to make its electron transport ability is very strong, and the raw material for the synthesis of graphene is graphite, the price is low, this indicates that graphene will be superior to carbon nanotubes in application. Compared with silicon, graphene also has a unique advantage: a silicon-based microcomputer processor can only perform a certain number of operations per second at room temperature, but electrons pass through graphene with almost no resistance, the amount of heat generated is also very low. In addition, graphene itself is a good thermal conductor, which can quickly emit heat. Due to the excellent performance, if an electronic product is manufactured from graphene, the speed of operation can be greatly improved. Speed is not the only advantage of graphene. Silicon can not be divided into small pieces less than 10nm, otherwise it will lose attractive electronic properties; Compared with silicon, graphene is divided when its basic physical properties do not change, and its electronic properties may also be abnormal. Thus, when Silicon can no longer be divided into smaller ones, graphene, which is smaller than silicon, can continue to maintain Moore's law, and thus it is very likely to be a substitute for silicon to promote the development of microelectronics technology.
In 2004, the discovery of graphene with a two-dimensional structure overturned the understanding that "Thermodynamic fluctuations do not allow two-dimensional crystals to exist freely at a finite temperature" and shocked the entire physical world, its discoverer, Geim and Novoselov from the Department of Physics and Astronomy at the University of Manchester, UK, was also nominated for the Nobel Prize in Physics in 2008. Compared with carbon nanotubes, graphene has a perfect hybrid structure, large conjugated system to make its electron transport ability is very strong, and the raw material for the synthesis of graphene is graphite, the price is low, this indicates that graphene will be superior to carbon nanotubes in application. Compared with silicon, graphene also has a unique advantage: a silicon-based microcomputer processor can only perform a certain number of operations per second at room temperature, but electrons pass through graphene with almost no resistance, the amount of heat generated is also very low. In addition, graphene itself is a good thermal conductor, which can quickly emit heat. Due to the excellent performance, if an electronic product is manufactured from graphene, the speed of operation can be greatly improved. Speed is not the only advantage of graphene. Silicon can not be divided into small pieces less than 10nm, otherwise it will lose attractive electronic properties; Compared with silicon, graphene is divided when its basic physical properties do not change, and its electronic properties may also be abnormal. Thus, when Silicon can no longer be divided into smaller ones, graphene, which is smaller than silicon, can continue to maintain Moore's law, and thus it is very likely to be a substitute for silicon to promote the development of microelectronics technology.
Last Update：2024-01-02 23:10:35
graphene - Discovery History
In the past 20 years, carbon has aroused great interest among researchers around the world. Since the discovery of fullerene and carbon nanotubes by scientists, three-dimensional diamond, "two-dimensional" graphite, one-dimensional carbon nanotubes, and zero-dimensional fullerene spheres have formed a complete carbon family. Among them, graphite has always been a hot research topic due to its special lamellar structure. The graphite body is not a real two-dimensional material, and a single-layer graphite carbon atom layer is a quasi-two-dimensional carbon material. A single layer of graphite carbon atomic layer refers to a layer of graphite with a C atomic layer thickness, C- C of which are connected by covalent bonds in a honeycomb structure. People have been trying to find a method to prepare carbon element quasi-two-dimensional materials.
there has been a debate in the scientific community about the existence of quasi-two-dimensional crystals. As early as 1934, Peierls et al. believed that quasi-two-dimensional crystal materials would rapidly decompose or disassemble at room temperature due to their own thermodynamic instability. Mer-min and Wagner put forward the Mermin-Wagner theory, also claimed that there is no two-dimensional crystalline material. However, single-layer graphene as a theoretical model for the study of carbon nanotubes has received extensive attention. It was not until 2004 that a single-layer graphene crystal was obtained by a very simple micromechanical force stripping method, which caused a new round of "carbon" boom in the scientific community. With the use of a nano-sized gold "scaffold", Geim et al. manufactured a single-layer graphene film suspended on it, and found that the suspended graphene film was not a "two-dimensional flat structure", instead, it has a "microwave-like monolayer structure" and attributes the stability of the graphene monolayer structure to its "microscopic distortion on the nano-scale".
there has been a debate in the scientific community about the existence of quasi-two-dimensional crystals. As early as 1934, Peierls et al. believed that quasi-two-dimensional crystal materials would rapidly decompose or disassemble at room temperature due to their own thermodynamic instability. Mer-min and Wagner put forward the Mermin-Wagner theory, also claimed that there is no two-dimensional crystalline material. However, single-layer graphene as a theoretical model for the study of carbon nanotubes has received extensive attention. It was not until 2004 that a single-layer graphene crystal was obtained by a very simple micromechanical force stripping method, which caused a new round of "carbon" boom in the scientific community. With the use of a nano-sized gold "scaffold", Geim et al. manufactured a single-layer graphene film suspended on it, and found that the suspended graphene film was not a "two-dimensional flat structure", instead, it has a "microwave-like monolayer structure" and attributes the stability of the graphene monolayer structure to its "microscopic distortion on the nano-scale".
Last Update：2023-08-16 21:48:54
graphene - Physical properties
Partoens et al. found that when the number of graphite layers is less than 10 layers, it will show a different electronic structure than ordinary three-dimensional graphite. We will be less than 10 layers of graphite materials (Graphene and Few-layergraphenes) are collectively referred to as Graphene materials (Graphene). Graphene (graphene) decomposition can become zero-dimensional fullerene, curl can form one-dimensional carbon nanotubes, superposition can form three-dimensional graphite. The theoretical specific surface area of graphene materials is as high as 2600/g, which has outstanding thermal conductivity (3000W/(m.K) and mechanical properties (1060GPa), as well as high electron mobility at room temperature (15000/(V.s)). The special structure of graphene makes it have a series of properties, such as perfect quantum tunneling effect, half-integer quantum Hall effect, and never disappear conductivity, which has aroused great interest in the scientific community, graphene is creating a research boom. Since 2004, research reports on graphene have sprung up, with more than 400 reports on Science and Nature. Another revolution in carbon chemistry is emerging.
Last Update：2023-08-16 21:48:54
graphene - Preparation of graphene
The research on graphene began in the 70s of the 20th century. Clar and others used chemical methods to synthesize a series of compounds with large conjugated systems, namely graphene sheets. Since then, scientists such as Schmidt have improved their method and synthesized many graphene derivatives containing different edge modification groups, but this method cannot obtain graphene with a larger planar structure.
The preparation of graphene can be divided into physical methods and chemical methods. Among them, the chemical method was studied earlier, mainly using benzene ring or other aromatic system as the core, and the six carbons on the benzene ring were replaced by the coupling reaction, then the adjacent substituents are dehydrogenated to form new aromatic rings, so that the aromatic system is enlarged by multi-step reaction, but this method cannot synthesize graphene with large planar structure; the physical method mainly uses graphite as the raw material to synthesize, not only the raw material is cheap and easy to obtain, but also the graphene with larger planar structure can be obtained. Therefore, there are many researches on this aspect at present.
The preparation of graphene can be divided into physical methods and chemical methods. Among them, the chemical method was studied earlier, mainly using benzene ring or other aromatic system as the core, and the six carbons on the benzene ring were replaced by the coupling reaction, then the adjacent substituents are dehydrogenated to form new aromatic rings, so that the aromatic system is enlarged by multi-step reaction, but this method cannot synthesize graphene with large planar structure; the physical method mainly uses graphite as the raw material to synthesize, not only the raw material is cheap and easy to obtain, but also the graphene with larger planar structure can be obtained. Therefore, there are many researches on this aspect at present.
Last Update：2023-08-16 21:48:54
graphene - Graphite oxide reduction pathway
Graphite is a hydrophobic substance, and graphite oxide (figure 3) has a large number of hydroxyl groups, carboxyl groups and other groups, is a hydrophilic substance. The interlayer spacing (0.7~1.2nm) is also larger than that of graphite (0.335nm). There are three kinds of oxidation methods commonly used for graphite, namely, the stand Maier method, the Brodie method and the Hummers method. The C atom on graphite oxide is sp3 hybrid, and the conductivity of graphite oxide is very poor compared with graphite. However, compared with graphite, the surface of graphite oxide layer contains a large number of functional groups, so graphite oxide and modified graphite oxide have better compatibility with many polymer matrices. The application of graphite oxide and modified graphite oxide in anode materials and flame retardant composites for lithium ion batteries has attracted much attention.
Reaction with some chemical substances to obtain modified graphite. The organic modification of the graphite oxide can also change the surface of the graphite oxide from hydrophilic to lipophilic and reduce the surface energy, thereby improving the compatibility with the polymer monomer or polymer. Thus, the adhesion between the graphite oxide and the polymer is enhanced. Graphite oxide is easily dispersed into a uniform single-layer graphene oxide solution in an aqueous solution or an organic solvent after appropriate ultrasonic shock treatment, which provides the possibility for people to prepare a large number of single-layer graphene.
Reaction with some chemical substances to obtain modified graphite. The organic modification of the graphite oxide can also change the surface of the graphite oxide from hydrophilic to lipophilic and reduce the surface energy, thereby improving the compatibility with the polymer monomer or polymer. Thus, the adhesion between the graphite oxide and the polymer is enhanced. Graphite oxide is easily dispersed into a uniform single-layer graphene oxide solution in an aqueous solution or an organic solvent after appropriate ultrasonic shock treatment, which provides the possibility for people to prepare a large number of single-layer graphene.
Last Update：2023-08-16 21:48:54
graphene - Preparation of graphene by micromechanical force exfoliation
In 2004, Geim et al used a very simple method-micro mechanical stripping method (micro mechanical stripping) to successfully peel off from highly oriented pyrolytic graphite and observed single layer graphene.
with 1mm thick high-oriented high-temperature pyrolytic graphite as raw material, a 5Lm deep platform (20Lm in size) 2mm in size is etched on the graphite sheet by dry oxygen plasma, the surface of the platform was coated with a 2LM thick fresh photoresist. After curing, the surface of the platform was attached to the photoresist layer and peeled off the graphite sheet. The graphite flakes can be repeatedly stripped from the graphite platform with a transparent photoresist, and the graphite flakes left in the photoresist are released in acetone, and the silicon wafer is immersed in it, then it is washed with a certain amount of water and acetone. Thus, some of the graphite flakes are attached to the silicon wafer. Place the silicon wafer in acetone and ultrasonically remove the thicker graphite flakes and the thinner graphite flakes (d<10nm) it is strongly retained on the SiO2 surface (due to the strong van der Waals forces and capillary forces between them).
The micromechanical exfoliation method was originally used as a physical method for the preparation of graphene. The disadvantages of this method are: time-consuming and laborious, difficult to accurately control, poor repeatability, and difficult to prepare on a large scale.
with 1mm thick high-oriented high-temperature pyrolytic graphite as raw material, a 5Lm deep platform (20Lm in size) 2mm in size is etched on the graphite sheet by dry oxygen plasma, the surface of the platform was coated with a 2LM thick fresh photoresist. After curing, the surface of the platform was attached to the photoresist layer and peeled off the graphite sheet. The graphite flakes can be repeatedly stripped from the graphite platform with a transparent photoresist, and the graphite flakes left in the photoresist are released in acetone, and the silicon wafer is immersed in it, then it is washed with a certain amount of water and acetone. Thus, some of the graphite flakes are attached to the silicon wafer. Place the silicon wafer in acetone and ultrasonically remove the thicker graphite flakes and the thinner graphite flakes (d<10nm) it is strongly retained on the SiO2 surface (due to the strong van der Waals forces and capillary forces between them).
The micromechanical exfoliation method was originally used as a physical method for the preparation of graphene. The disadvantages of this method are: time-consuming and laborious, difficult to accurately control, poor repeatability, and difficult to prepare on a large scale.
Last Update：2023-08-16 21:48:54
graphene - Characterization of graphene
The reason why single-layer graphene has only been discovered so far is because of the limitation of characterization methods. At present, the effective means to characterize graphene are: Atomic force microscopy, optical microscopy, Raman spectroscopy.
The application of atomic force microscopy makes it possible to observe single-layer graphene. Single-layer graphene has a thickness of only 0.335nm, which is difficult to be observed in scanning electron microscopy (SEM) and can only be clearly observed in atomic force microscopy (AFM). Atomic force microscopy is the most direct and effective means to characterize graphene materials.
However, the yield of graphene prepared by micromechanical exfoliation method is very low, and many multilayer graphite sheets are doped in a small amount of exfoliation, which are directly observed by atomic force microscopy, and the efficiency is very low. EIM et al. found that a single layer of graphene was attached to a Si wafer with a surface covered with a certain thickness (300nm) of SiO2 layer, which could be observed under an optical microscope. This is because the single layer graphite layer and the substrate have a certain interference on the light and a certain contrast, so the single layer graphene can be distinguished under the optical microscope.
The observation of graphene by optical microscope provides a fast and simple means for the characterization of graphene, which makes it possible to obtain further accurate characterization of graphene.
The application of atomic force microscopy makes it possible to observe single-layer graphene. Single-layer graphene has a thickness of only 0.335nm, which is difficult to be observed in scanning electron microscopy (SEM) and can only be clearly observed in atomic force microscopy (AFM). Atomic force microscopy is the most direct and effective means to characterize graphene materials.
However, the yield of graphene prepared by micromechanical exfoliation method is very low, and many multilayer graphite sheets are doped in a small amount of exfoliation, which are directly observed by atomic force microscopy, and the efficiency is very low. EIM et al. found that a single layer of graphene was attached to a Si wafer with a surface covered with a certain thickness (300nm) of SiO2 layer, which could be observed under an optical microscope. This is because the single layer graphite layer and the substrate have a certain interference on the light and a certain contrast, so the single layer graphene can be distinguished under the optical microscope.
The observation of graphene by optical microscope provides a fast and simple means for the characterization of graphene, which makes it possible to obtain further accurate characterization of graphene.
Last Update：2023-08-16 21:48:54
graphene - Applications of graphene
Because graphene has the advantages of large specific surface area and high conductivity, it can be used as an electrode material, a sensor, a hydrogen storage material, and the like.
The oxygen-containing groups on the surface of graphene can form hydrogen bonds with water and OH-, and the 1-2-layer graphene of the Crystal epitaxial type can sensitively sense the ion density on the surface, so that it can be used as a good pH sensor.
The surface of graphene can adsorb gas molecules, and different gas molecules can act as electron donors or acceptors, causing changes in electrical conductivity, which is similar to the mechanism of solid gas sensors.
In the aspect of hydrogen storage materials, alloys such as LaNi5, TiFe, MgNi and the like all have hydrogen storage ability. Among them, La and Ti alloys are low temperature (<150e) hydrogen storage materials, but their hydrogen storage capacity is low (<2wt%);Mg alloys are high temperature hydrogen storage materials, although the theoretical hydrogen storage capacity is very high, but its adsorption P desorption kinetics is not stable. In addition, the alloy is not only expensive but also has a large proportion, which greatly limits its practical application. In the development and research of new hydrogen storage materials, it is found that carbon nanotubes and graphene have good hydrogen storage ability, and the price of these materials is low, which can greatly reduce the cost.
graphene has good electrical conductivity, and small contact resistance with organic materials (graphene P and five benzene: 0116)0118M8; Silver P and five benzene: 1156M8; copper Pentacene: 118M8), It is compatible with organic materials and is therefore a good electrode material.
The oxygen-containing groups on the surface of graphene can form hydrogen bonds with water and OH-, and the 1-2-layer graphene of the Crystal epitaxial type can sensitively sense the ion density on the surface, so that it can be used as a good pH sensor.
The surface of graphene can adsorb gas molecules, and different gas molecules can act as electron donors or acceptors, causing changes in electrical conductivity, which is similar to the mechanism of solid gas sensors.
In the aspect of hydrogen storage materials, alloys such as LaNi5, TiFe, MgNi and the like all have hydrogen storage ability. Among them, La and Ti alloys are low temperature (<150e) hydrogen storage materials, but their hydrogen storage capacity is low (<2wt%);Mg alloys are high temperature hydrogen storage materials, although the theoretical hydrogen storage capacity is very high, but its adsorption P desorption kinetics is not stable. In addition, the alloy is not only expensive but also has a large proportion, which greatly limits its practical application. In the development and research of new hydrogen storage materials, it is found that carbon nanotubes and graphene have good hydrogen storage ability, and the price of these materials is low, which can greatly reduce the cost.
graphene has good electrical conductivity, and small contact resistance with organic materials (graphene P and five benzene: 0116)0118M8; Silver P and five benzene: 1156M8; copper Pentacene: 118M8), It is compatible with organic materials and is therefore a good electrode material.
Last Update：2023-08-16 21:48:54
graphene - Market Prospects
With the deepening of the research on graphene and the improvement of its preparation methods, graphene has received extensive attention in the fields of composite materials, nano devices and hydrogen storage materials. The conductivity of graphene is good, it is expected to replace the silicon production of supercomputers; Its light weight, high strength, not only can be used to develop a paper-like thin ultra-light aircraft materials, ultra-tough body armor, could even make the 2.13 million-mile-long space elevator that scientists long for a reality. However, in order to make the graphene material product, it is necessary to be able to obtain a large number of high quality graphene with complete structure. This requires an increase in the level of existing manufacturing processes. The micro-mechanical method obviously cannot meet the requirements of the future industrialization. Although the graphite oxide reduction method can produce a large number of graphene at a relatively low cost, it has a great application prospect in the fields of composite materials and anti-static coatings, however, the electronic structure and crystal integrity of graphene are seriously damaged by strong oxidants, which will affect its electronic properties, which limits its application in the field of precision Microelectronics to a certain extent. The chemical growth method can be used to prepare large-area continuous graphene thin film semiconductor materials with excellent performance, and the existing semiconductor processing technology can also be used to tailor and modify the graphene thin film materials, the graphene materials prepared by chemical growth method have great application potential in the field of microelectronics. However, the way to prepare graphene by chemical deposition is still under further exploration and improvement. The immature process and high cost at this stage limit its large-scale application. How to prepare high quality graphene materials in large quantities and at low cost should be a focus of future research. Although scientists have made a lot of efforts in this area, but still can not achieve its industrial production, therefore, the synthesis of graphene is still a research hotspot. In addition, scientists will pay more attention to how to modify it by chemical methods to further improve its performance in all aspects and promote the process of device, industrialization and commercialization.
Last Update：2023-08-16 21:48:54
graphene - Reference Information
| Usage | Mono graph films are ready to use in various research purposes, photoluminesence and Raman spectroscopy studies. Graphene paw-layer films can also be transferred to other substrates. |
Last Update：2024-04-09 21:04:16
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graphene
alpha-Glucosidase (from Yeast) 100kU pack
Chloro(4-cyanophenyl){(R)-1-[(S)-2-(dicyclohexylphosphino)ferrocenyl]ethyl (diphenylphosphine)}nickel(II)
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3-bromo-4-(trifluoromethoxy)phenol
(S)-2-Amino-2-(4-fluorophenyl)ethanol
2-FLUORO-3-(TRIFLUOROMETHYL)PHENYLBORON
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4-chloro-2-fluorophenol
119942-99-3
alpha-Glucosidase (from Yeast) 100kU pack
Chloro(4-cyanophenyl){(R)-1-[(S)-2-(dicyclohexylphosphino)ferrocenyl]ethyl (diphenylphosphine)}nickel(II)
67719-69-1
3-bromo-4-(trifluoromethoxy)phenol
(S)-2-Amino-2-(4-fluorophenyl)ethanol
2-FLUORO-3-(TRIFLUOROMETHYL)PHENYLBORON
2573217-06-6
4-chloro-2-fluorophenol
119942-99-3