Mokoloko Lerato L, Forbes Roy P, Coville Neil J
DSI-NRF Centre of Excellence in Catalysis and the Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa.
Nanomaterials (Basel). 2022 Jul 22;12(15):2515. doi: 10.3390/nano12152515.
Carbon dots (CDs) represent a relatively new type of carbon allotrope with a 0-D structure and with nanoparticle sizes < 10 nm. A large number of research articles have been published on the synthesis, characteristics, mechanisms and applications of this carbon allotrope. Many of these articles have also shown that CDs can be synthesized from “bottom-up” and “top-down” methods. The “top-down” methods are dominated by the breaking down of large carbon structures such as fullerene, graphene, carbon black and carbon nanotubes into the CDs. What is less known is that CDs also have the potential to be used as carbon substrates for the synthesis of larger carbon structures such as 1-D carbon nanotubes, 2-D or 3-D graphene-based nanosheets and 3-D porous carbon frameworks. Herein, we present a review of the synthesis strategies used to convert the 0-D carbons into these higher-dimensional carbons. The methods involve the use of catalysts or thermal procedures to generate the larger structures. The surface functional groups on the CDs, typically containing nitrogen and oxygen, appear to be important in the process of creating the larger carbon structures that typically are formed via the generation of covalent bonds. The CD building blocks can also ‘aggregate’ to form so called supra-CDs. The mechanism for the formation of the structures made from CDs, the physical properties of the CDs and their applications (for example in energy devices and as reagents for use in medicinal fields) will also be discussed. We hope that this review will serve to provide valuable insights into this area of CD research and a novel viewpoint on the exploration of CDs.
碳点（CDs）是一种相对新型的具有零维结构且纳米颗粒尺寸小于10 nm的碳同素异形体。关于这种碳同素异形体的合成、特性、机理及应用，已发表了大量研究文章。其中许多文章还表明，碳点可通过“自下而上”和“自上而下”的方法合成。“自上而下”的方法主要是将诸如富勒烯、石墨烯、炭黑和碳纳米管等大型碳结构分解成碳点。鲜为人知的是，碳点还有潜力用作合成更大碳结构的碳基底，如一维碳纳米管、二维或三维基于石墨烯的纳米片以及三维多孔碳骨架。在此，我们对用于将零维碳转化为这些更高维碳的合成策略进行综述。这些方法涉及使用催化剂或热程序来生成更大的结构。碳点上的表面官能团通常含有氮和氧，在创建通常通过共价键生成而形成的更大碳结构的过程中似乎很重要。碳点构建块也可以“聚集”形成所谓的超碳点。还将讨论由碳点制成的结构的形成机理、碳点的物理性质及其应用（例如在能量装置中以及作为医药领域使用的试剂）。我们希望这篇综述将有助于为碳点研究领域提供有价值的见解，并为碳点的探索提供新的视角。
