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National Science and Technology Research Council

Graphene is composed of a planar structure with carbon atoms connected in a hexagonal shape, similar to a honeycomb. When the size of graphene is reduced to a few nanometers (nm), it becomes graphene quantum dots, showing fluorescence and semiconductor properties. As a new type of material, graphene quantum dots can be used in various applications, including display screens, solar cells, secondary batteries, biological imaging, lighting, photocatalysis, and sensors. Interest in graphene quantum dots is growing because recent studies have shown that controlling the proportion of heteroatoms (such as nitrogen, sulfur, and phosphorus) in the carbon structure of certain materials can enhance their optical, electrical, and catalytic properties.

The Korea Institute of Science and Technology (KIST, Dean of Seok-Jin Yoon) reported that a research team led by Dr. Byung-Joon Moon and Dr. Sukang Bae of the Functional Composite Materials Research Center has developed a technology to precisely control the bonded graphene quantum The structure of a single heteroatom in the dot is a zero-dimensional carbon nanomaterial, controlled by a simple chemical reaction; and they have determined the relevant reaction mechanism.

In order to control the incorporation of heteroatoms in graphene quantum dots, researchers have previously studied the use of additives to introduce heteroatoms into the dots after the dots themselves have been synthesized. This point must then be further purified, so this method adds several steps throughout the manufacturing process. Another method studied involves the simultaneous use of multiple organic precursors (they are the main components of point synthesis) and additives containing heteroatoms. However, these methods have obvious disadvantages, including reduced crystallinity of the final product and lower overall reaction yield, because several additional purification steps must be implemented. In addition, in order to obtain quantum dots with the chemical composition required by the manufacturer, various reaction conditions, such as the ratio of additives, must be optimized. This will inevitably lead to an increase in the duration of the entire process and unit manufacturing costs.

Traditional manufacturing methods use acidic precursors or solutions, so neutralization and purification steps are required. In contrast, the newly developed process uses weakly alkaline precursors that are neutralized during the synthesis process, which means that the advantage of this process is that the graphene quantum dots produced do not require additional processing before they are ready for use.

The research team also used computer modeling based on computational chemistry and found that the solvent used in the synthesis of graphene quantum dots affects the oxidation of the organic precursor fumaronitrile, which also contains heteroatoms (nitrogen). This means that the type of solvent ultimately determines the chemical composition of the final graphene quantum dot product. In addition, the theoretical oxidation energy value of the organic precursor calculated based on the specific solvent used has been experimentally proved to have the ability to predict the approximate chemical composition of the final graphene quantum dots.

Dr. Sukang Bae of KIST said: “We have developed a new platform technology that allows us to selectively adjust the chemical composition of heteroatoms to synthesize graphene quantum dots through a single synthesis process without using other organic precursors. Additives, such as fumaronitrile," and added, "because we have discovered a method for large-scale synthesis of graphene quantum dots without additional post-processing or purification, we can reduce the overall processing time and improve the synthesis process. Economic feasibility."

In addition, this achievement is expected to promote the development of nano-carbon materials, increase economic opportunities for small and medium-sized enterprises, and further promote the growth of human resources related to the expansion of the carbon material industry, which is a regional strategic industry in Jeollabuk-do.

This research was conducted as an institutional research plan and a material component technology development plan of the Ministry of Trade, Industry and Energy (Minister Wen Shengxu). The research results were published in the journal Nature Communications. Further explore the synthesis of single crystal hexagonal graphene quantum dots. For more information: Byung Joon Moon et al., the structure-controlled growth of nitrided graphene quantum dots through solvent catalysis for selective CN bond activation, Nature Communications (2021 year). DOI: 10.1038/s41467-021-26122-0 Journal information: Nature Communications

Citation provided by the National Science and Technology Research Committee: Development of a single process platform for manufacturing graphene quantum dots (2021, December 3) Retrieved on December 6, 2021 from https://phys.org/news/2021-12- single-process-platform-graphene-quantum-dots.html This document is protected by copyright. Except for any fair transaction for private learning or research purposes, no part may be copied without written permission. The content is for reference only.

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