功能化石墨烯材料:定义、分类及制备策略

Functionalized Graphene Materials: Definition, Classification, and Preparation Strategies

自2004年被成功制备后,石墨烯因其独特迷人的性质在近十几年来备受关注,同时也引发了二维纳米材料的研究热潮。单原子层厚度的二维结构赋予石墨烯非同寻常的光学、电子学、磁学及力学等性质,使得石墨烯在生物学、医学、化学、物理学和环境科学等多个领域展现出极大的应用潜力。制得注意的是,石墨烯在应用时通常需要进行功能化,调节其组成、大小、形状和结构等,以便于加工处理或满足不同的应用需求。石墨烯功能化方法多样,功能化产物也是种类繁多。然而,到目前为止,石墨烯功能化产物并没有系统全面的分类和精确的定义。因此,本文在系统总结现有石墨烯功能化研究的基础上,给出了石墨烯功能化产物的系统分类、各类的精确定义和相应的制备策略,并通过典型示例进行了详细地阐述。石墨烯功能化的产物统称为"功能化石墨烯材料",分为两类:"功能化石墨烯"和"功能化石墨烯复合材料"。功能化石墨烯材料的制备可由"自上而下"和"自下而上"两种策略实现。制备策略的选择取决于应用需求。系统分类、精确命名和制备策略的归纳必将有助于功能化石墨烯材料的进一步发展。

Since its emergence in 2004, graphene has attracted enormous attention because of its unique and fantastic properties, which signals the birth of two-dimensional(2 D) nanomaterials. The strictly atomic-layered 2 D structure endows graphene with unconventional optical, electronic, magnetic, and mechanical properties. Owing to these extraordinary features, graphene has exhibited great potential in various fields, such as biology, medicine, chemistry, physics, and the environment. Notably, when graphene is used in these fields, it is always functionalized to facilitate its manipulation or meet the different area demands. After functionalization, the properties of graphene, such as its composition, size, shape, and structure, are modified, leading to changes in its electronic structure, surface chemistry, solubility, and mechanical and chemical properties. Functionalization of graphene can be achieved through various approaches, including chemical oxidation, doping, covalent and non-covalent modification, and hybridization with other materials, yielding various products(i.e., graphene oxide, nano graphene, graphene nanoribbons(GNRs), graphene nanomeshes, and graphene-polymer hybrids). However, these resulting products have not been systematically classified or strictly defined until now;although they have been classified as covalent and non-covalent functionalized graphene, graphene-based polymer composites, and graphene-based composites. Systematic classification and exact definition will benefit research on functionalizing graphene. In this review, based on research on functionalization of graphene, we propose a systematic classification of the products from graphene functionalization, their corresponding definitions, and preparation strategies, which are illustrated by representative examples. All the products from graphene functionalization are defined as functionalized graphene materials, which fall into two categories: functionalized graphene and functionalized graphene composite. Functionalized graphene is the product of modifying graphene by tuning its composition, framework, dimension, and morphology, and functionalized graphene composites are hybrids of graphene(or functionalized graphene) with other materials, including small molecules, polymers, metals, inorganic compounds, and carbon nanotubes(CNTs). Functionalized graphene materials are prepared through two strategies: “top-down” and “bottom-up,” each of which has its advantages and shortcomings and includes many corresponding preparation methods. The selection of preparation strategies depends on the application requirements, as different applications require different types of graphene. Both strategies are elucidated with detailed examples through an extensive analysis of the literature. Finally, the major challenges and perspectives of functionalized graphene materials are discussed. This review presents the proposed systematic classification and exact definition of functionalized graphene materials, which can enhance their development. It is believed that functionalized graphene materials will achieve significant progress in the future.