My scientists have made a series of progress in graphene research
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Graphene is a new carbonaceous material that is closely packed into a two-dimensional honeycomb lattice structure by a single layer of carbon atoms. It is a carbonaceous material of other dimensions (such as zero-dimensional fullerene, one-dimensional carbon nanotubes, The basic unit of three-dimensional graphite). Graphene has excellent electrical, thermal and mechanical properties and is expected to be widely used in high performance nanoelectronic devices, composite materials, field emission materials, gas sensors and energy storage. Due to its unique two-dimensional structure and excellent crystallographic quality, graphene contains rich and novel physical phenomena, which provides an ideal platform for the study of quantum electrodynamic phenomena and has important theoretical research value. Therefore, graphene has rapidly become one of the research hotspots in the field of materials science and condensed matter physics in recent years.
Researchers in the Advanced Carbon Materials Division of the National (Joint) Laboratory of Materials Science at the Institute of Materials Science, Chinese Academy of Sciences have included the following three aspects.
Controlled high quality graphene. Depending on the number of layers, the electronic structure of graphene changes significantly, so it is critical to control the number of graphene layers. Compared with micromechanical stripping and epitaxial growth methods, chemical stripping is an effective method for achieving low-cost macro-preparation of graphene, but the graphene prepared is mostly a mixture of single-layer, double-layer and multi-layer graphene. Based on the analysis of the process of preparing graphene by chemical stripping method, they proposed a strategy to control the number of graphene layers by using the difference in size and crystallinity of graphite raw materials. Macroscopic control prepared high monolayer, double layer and three layers. The quality of graphene, considered by reviewers, is "a significant advance in the research and application of graphene." In order to further improve the quality of the graphene prepared by the chemical stripping method, they are characterized by high hydrogen arc discharge reaction temperature, rapid heating and in-situ reduction, and arc-heating cleavage of cleavage graphite to remove oxygen-containing functional groups and healing structural defects. This further improves the quality of graphene. Compared with the conventional rapid heating method, the oxidation temperature of graphene prepared by the hydrogen arc method is increased by nearly 100 ° C, and the conductivity is improved by nearly two orders of magnitude.
A new method for characterizing graphene structure was proposed. The establishment of graphene characterization method is the premise and basis for its rapid and effective characterization, control preparation and application. Based on the calculation of reflectivity, they introduce the concept of color space, and propose a method for total color difference of graphene layer with fast, accurate and non-destructive characterization. It explains the reason why graphene is visible only on a specific substrate, and uses this method. The substrate and light source were optimized, and the substrate and light source which are more conducive to the optical characterization of graphene were proposed and experimentally improved, which improved the accuracy of optical characterization and laid a foundation for the rapid and accurate characterization, control preparation and physical properties of graphene layers.
The paper was selected by the American Chemical Society's ACS Nano magazine as the highlight of the period. It was also selected by Nature-China as a prominent scientific research achievement from China and Hong Kong. Commentator Dr. Vicki Cleave wrote: "Ren Wencai, Cheng Huiming and his collaborators from the Chinese Academy of Sciences have proposed a fast, non-destructive optical method for large-area graphene characterization that helps determine and Prepare ideal graphene samples for your application."
In addition, in view of the current problem that the graphene Raman spectrum signal is weak and it is difficult to characterize its fine structure, the research group also invented an enhanced Raman scattering technique, which not only improves the signal intensity of graphene Raman spectroscopy, but also Fine structural features of graphene which are not obtained by ordinary Raman spectroscopy are obtained.
In the application of graphene, researchers in the laboratory have explored the application of graphene in field emitters, supercapacitors, lithium-ion batteries and transparent conductive films on the basis of graphene macro-preparation.
In order to give full play to the structural and performance advantages of graphene, they developed an electrophoretic deposition method to prepare a single-layer graphene film with uniform surface and rich boundary protrusions, which achieved good contact between the film and the substrate. Studies have shown that graphene films have field emission characteristics compared with carbon nanotube films: low on-field and threshold, good field emission stability and uniformity, demonstrating the application prospects of graphene in flat panel display.