Scientists find new ways to produce nanographene sheets on a large scale

According to a report by the American Physicist Network on March 26, researchers in South Korea and the United States recently said that by mixing solid carbon dioxide and corresponding solvents, high-quality nanographene sheets can be produced on a large scale in a simple and economical manner. The relevant research report was published online this week in the online edition of the National Academy of Sciences. Graphene is derived from graphite and is known for its excellent electrical conductivity, thermal conductivity and robustness. Scientists around the world believe that graphene will revolutionize the state of computing, electronics and medicine, but the inability to produce graphene sheets on a large scale has hampered its widespread use. The author of the paper, Professor Dai Liming of the Department of Polymer Science and Engineering at Case Western Reserve University, said that they have developed a low-cost, simple way to produce better-quality graphene sheets on a large scale. At present, the acid oxidation method is commonly used, and the promotion is affected by the need to use toxic chemicals. The study was led by Professor Bai Zhongfan of the Ulsan National Institute of Science and Technology in Korea. The researchers placed graphite and solid carbon dioxide in a canister filled with stainless steel balls. After two days, they were processed by carboxylic acid and mechanical force to produce graphite flakes with edges open to create a chemical reaction. The edge treated with the carboxylic acid dissolves the graphite in the protic solvent, including water and methanol; it is also soluble in polar aprotic solvents, including dimethyl sulfoxide and the like. Once dispersed in the solvent, the graphite flakes are separated into five or fewer layers of nanographene flakes. To test whether these materials directly form the molded objects needed for electronic applications, the researchers compressed the samples into pellets. After comparison, it was found that the conductivity of these pellets was 688 times higher than that of the conventional pellets produced by the acidic graphite oxide method. In order to form a large area of ​​nanographene film, the scientists heated the compressed pellets for up to 900 degrees Celsius for 2 hours based on a 3.5 cm x 5 cm silicon wafer. Subsequently, the edges of the milled flakes are decoupled from the carboxyl group, which means that the edges of the nanoflakes can be strongly hydrogen bonded to the adjacent flakes and remain bonded, while the acidic oxidized compressed nuggets will A condition of breakage occurs during heating. The researchers said that this process will only be limited by the size of the wafer, and the large-area film produced will have much higher conductivity than the acid oxidation process, while maintaining higher light transmittance. In addition, by switching to ammonia or sulfur trioxide as an alternative to dry ice and using different solvents, scientists can customize the edge of graphene sheets for different applications such as electronics, supercapacitors and metal-free catalysts that can replace platinum. Edges can also be customized to assemble 2D and 3D structures.

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