氧化石墨烯纳米带杂化粒子和石墨烯纳米带的研究进展

氧化石墨烯纳米带杂化粒子是将氧化石墨烯纳米带(GONRs)与其他纳米粒子经π-π键、氢键等结合方式复合在一起,通过这种特殊的结合形态一方面可以有效地防止GONRs的聚积,另一方面新的纳米粒子的引入能够赋予该杂化材料某些特殊的性能,从而有利于充分发挥GONRs杂化材料在聚合物改性等领域的综合性能。本文综述了氧化石墨烯纳米带杂化粒子的制备方法、性能和应用现状。此外,针对GONRs的还原产物石墨烯纳米带(GNRs)的结构、性能、制备方法及其应用领域也进行了系统性地论述。相关研究表明,氧化石墨烯纳米带杂化粒子的设计与制备是氧化石墨烯纳米带迈向实用领域的一个有效途径,而石墨烯纳米作为石墨烯的一种特殊结构的二维变体,继承了石墨烯优良的导电和导热等性能,同时特殊的边缘效应,因而呈现出了更广阔的应用潜力。     

Graphene Nanoribbons: On-Surface Synthesis and Integration into Electronic Devices

Graphene nanoribbons (GNRs) are quasi-1D graphene strips, which have attracted attention as a novel class of semiconducting materials for various applications in electronics and optoelectronics. GNRs exhibit unique electronic and optical properties, which sensitively depend on their chemical structures, especially the width and edge configuration. Therefore, precision synthesis of GNRs with chemically defined structures is crucial for their fundamental studies as well as device applications. In contrast to top-down methods, bottom-up chemical synthesis using tailor-made molecular precursors can achieve atomically precise GNRs. Here, the synthesis of GNRs on metal surfaces under ultrahigh vacuum (UHV) and chemical vapor deposition (CVD) conditions is the main focus, and the recent progress in the field is summarized. The UHV method leads to successful unambiguous visualization of atomically precise structures of various GNRs with different edge configurations. The CVD protocol, in contrast, achieves simpler and industry-viable fabrication of GNRs, allowing for the scale up and efficient integration of the as-grown GNRs into devices. The recent updates in device studies are also addressed using GNRs synthesized by both the UHV method and CVD, mainly for transistor applications. Furthermore, views on the next steps and challenges in the field of on-surface synthesized GNRs are provided.     

Recent Advances of Porous Graphene: Synthesis,Functionalization, and Electrochemical Applications

Graphene is a 2D sheet of sp² bonded carbon atoms and tends to aggregate together, due to the strong π–π stacking and van der Waals attraction between different layers. Its unique properties such as a high specific surface area and a fast mass transport rate are severely blocked. To address these issues, various kinds of 2D holey graphene and 3D porous graphene are either self‐assembled from graphene layers or fabricated using graphene related materials such as graphene oxide and reduced graphene oxide. Porous graphene not only possesses unique pore structures, but also introduces abundant exposed edges and accelerates mass transfer. The properties and applications of these porous graphenes and their composites/hybrids have been extensively studied in recent years. Herein, recent progress and achievements in synthesis and functionalization of various 2D holey graphene and 3D porous graphene are reviewed. Of special interest, electrochemical applications of porous graphene and its hybrids in the fields of electrochemical sensing, electrocatalysis, and electrochemical energy storage, are highlighted. As the closing remarks, the challenges and opportunities for the future research of porous graphene and its composites are discussed and outlined.     

Modified Engineering of Graphene Nanoribbons Prepared via On-Surface Synthesis

1D graphene nanoribbons (GNRs) have a bright future in the fabrication of next-generation nanodevices because of their nontrivial electronic properties and tunable bandgaps. To promote the application of GNRs, preparation strategies of miscellaneous GNRs have to be developed. The GNRs prepared by top-down approaches are accompanied by uncontrolled edges and structures. In order to overcome the difficulties, bottom-up methods are widely used in the growth of various GNRs due to controllability of GNRs' features. Among those bottom-up methods, the on-surface synthesis is a promising approach to prepare GNRs with distinct widths, edge/backbone structures, and so forth. Therefore, modified engineering of the GNRs prepared via on-surface synthesis is of great significance in controllable preparation of GNRs and their potential applications. In the past decade, there have been a lot of reports on controllable preparation of GNRs using on-surface synthesis approach. Herein, the advances of GNRs grown via on-surface growth strategy are described. Several growth parameters, the latest advances in the modification of the GNR structure and width, the GNR doping/co-doping with heteroatoms, a variety of GNR heterojunctions, and the device application of GNRs are reviewed. Finally, the opportunities and challenges are discussed.     

On‐Surface Synthesis of 8‐ and 10‐Armchair Graphene Nanoribbons

Armchair graphene nanoribbons (AGNRs) with 8 and 10 carbon atoms in width (8‐ and 10‐AGNRs) are synthesized on Au (111) surfaces via lateral fusion of nanoribbons that belong to different subfamilies. Poly‐para‐phenylene (3‐AGNR) chains are pre‐synthesized as ladder ribbons on Au (111). Subsequently, synthesized 5‐ and 7‐AGNRs can laterally fuse with 3‐AGNRs upon annealing at higher temperature, producing 8‐ and 10‐AGNRs, respectively. The synthetic process, and their geometric and electronic structures are characterized by scanning tunneling microscopy/spectroscopy (STM/STS). STS investigations reveal the band gap of 10‐AGNR (2.0 ± 0.1 eV) and a large apparent band gap of 8‐AGNRs (2.3 ± 0.1 eV) on Au (111) surface.     

Electronic Property Modification of Single‐Walled Carbon Nanotubes by Encapsulation of Sulfur‐Terminated Graphene Nanoribbons

The use of carbon nanotubes (CNTs) as cylindrical reactor vessels has become a viable means for synthesizing graphene nanoribbons (GNRs). While previous studies demonstrated that the size and edge structure of the as‐produced GNRs are strongly dependent on the diameter of the tubes and the nature of the precursor, the atomic interactions between GNRs and surrounding CNTs and their effect on the electronic properties of the overall system are not well understood. Here, it is shown that the functional terminations of the GNR edges can have a strong influence on the electronic structure of the system. Analysis of SWCNTs before and after the insertion of sulfur‐terminated GNRs suggests a metallization of the majority of semiconducting SWCNTs. This is indicated by changes in the radial breathing modes and the D and G band Raman features, as well as UV–vis–NIR absorption spectra. The variation in resonance conditions of the nanotubes following GNR insertion make direct (n,m) assignment by Raman spectroscopy difficult. Thus, density functional theory calculations of representative GNR/SWCNT systems are performed. The results confirm significant changes in the band structure, including the development of a metallic state in the semiconducting SWCNTs due to sulfur/tube interactions. The GNR‐induced metallization of semiconducting SWCNTs may offer a means of controlling the electronic properties of bulk CNT samples and eliminate the need for a physical separation of semiconducting and metallic tubes.     

羧基功能化和表面活性剂修饰对石墨烯电化学性能的影响

通过简单的两步溶液法对石墨烯进行羧基接枝和表面活性剂修饰, 并研究其电化学性能。研究结果表明, 与纯石墨烯(比电容50 F/g)相比, 表面活性剂本身并不能有效提高石墨烯的比电容(45 F/g), 羧基功能化可以将石墨烯的比电容提高至130 F/g。而羧基功能化和表面活性剂修饰双处理工艺能够将石墨烯的比电容提高到230 F/g, 且经800次充放电循环后其比电容仍然具有95%的保持率, 表明该材料具有良好的循环稳定性。因此, 调控石墨烯的表面化学特性对提高其电化学性能具有重要的意义。     

Charge Transport in Polycrystalline Graphene: Challenges and Opportunities

Graphene has attracted significant interest both for exploring fundamental science and for a wide range of technological applications. Chemical vapor deposition (CVD) is currently the only working approach to grow graphene at wafer scale, which is required for industrial applications. Unfortunately, CVD graphene is intrinsically polycrystalline, with pristine graphene grains stitched together by disordered grain boundaries, which can be either a blessing or a curse. On the one hand, grain boundaries are expected to degrade the electrical and mechanical properties of polycrystalline graphene, rendering the material undesirable for many applications. On the other hand, they exhibit an increased chemical reactivity, suggesting their potential application to sensing or as templates for synthesis of one‐dimensional materials. Therefore, it is important to gain a deeper understanding of the structure and properties of graphene grain boundaries. Here, we review experimental progress on identification and electrical and chemical characterization of graphene grain boundaries. We use numerical simulations and transport measurements to demonstrate that electrical properties and chemical modification of graphene grain boundaries are strongly correlated. This not only provides guidelines for the improvement of graphene devices, but also opens a new research area of engineering graphene grain boundaries for highly sensitive electro‐biochemical devices.