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Chinese scientists first prepared single-layer graphene nanoribbons

2019-03-29 来源:亚科官网
On March 27th, Professor Feng Wei of Tianjin University made a single layer of graphene nanobelts for the first time in the world by cutting single-walled carbon nanotubes with fluorine radicals. This is the first time that a Chinese scientist has obtained a single-layer graphene nanobelt by a one-step method. Its energy density as a positive electrode material of a primary battery can be increased by 30% compared with imported products.
Fluorinated carbon is the solid state positive electrode material of the galvanic cell with the highest theoretical energy density in the world. Western developed countries have always regarded high-energy fluorocarbon preparation as the core technology, and it is strictly forbidden to export technology and open communication. At present, the widely used carbon fluoride materials in China mainly rely on foreign imports, which seriously restricts the scientific research and industrial development in related fields in China.
Graphene is a two-dimensional material with excellent properties and a honeycomb structure composed of a single layer of carbon atoms. Its thickness is only one-millionth of the diameter of human hair, but its strength is better than steel, and its electrical conductivity is better than copper, so it is very suitable for electronic devices. Graphene is a conductive material, but it can also become a nanostrip semiconductor. This means that you need to have enough energy or band gap, where no electronic state can exist: it can be turned on or off, making it a key component of nanotransistors.
The finest details in the graphene nanoribbon atomic structure have a huge impact on the band width of the transistor components and the suitability of the nanoribbons. In one aspect, the band width depends on the width of the graphene ribbon; on the other hand, it depends on the structure of the edge. Since graphene is composed of equilateral hexagonal carbon, it will have a zigzag shape on the side, or an armchair shape, depending on the direction of the belt. An energy band having a zigzag edge will be electrically conductive like a metal; and an energy band having an armchair shape will become a semiconductor.
This poses a major challenge for the production of nanoribbons: if the nanoribbons are cut by shearing the graphene layer, or by shearing the nanotube layer, these edges will be irregular, so graphene nanoribbons will not be able to present us Expected electrical characteristics.
Now, scientists have successfully grown a band of only 9 atoms wide with regular armchair-shaped edges. To achieve this, the previously prepared molecules are concentrated in an ultra-high vacuum. After a few steps, they are combined on a gold substrate like a puzzle to form the desired nanoribbon. The nanoribbon has a width of only 1 nanometer and a length of 50 nanometers.
However, due to its own structural limitations, the current international mainstream fluorocarbon materials also have pain points—it is difficult to achieve "high energy density" and "high power density". In 2008, Feng Wei team first proposed the development of a new type of fluorinated carbon material with a unique structure to achieve "double high" energy density and power density. After more than ten years of research, the team has overturned the existing covalent fluorocarbon structure based on graphene six-membered ring structure, and has taken the lead in the development of structural fluorinated carbon materials with high voltage and high capacity. According to laboratory tests, the energy density of this new material reached 2738Wh/kg, which is 30% higher than that of similar foreign products and reached the international leading level. At the same time, it can work stably under the condition of large discharge current. According to estimates, its cost can be significantly reduced compared to imported materials. At present, the team has achieved stable small batch production of new fluorinated carbon materials.
Edited by Suzhou Yacoo Science Co., Ltd.