Graphene nanoribbons (GNRs)─quasi-one-dimensional graphene cutouts─have drawn growing attention as promising candidates for next-generation electronic and spintronic materials. Theoretical and experimental studies have demonstrated that the electronic and magnetic properties of GNRs critically depend on their widths and edge topologies. Thus, the preparation of structurally defined GNRs is highly desirable not only for their fundamental physicochemical studies but also for their future technological development in carbon-based nanoelectronics. In the past decade, significant efforts have been made to construct a wide variety of GNRs with well-defined widths and edge structures via bottom-up synthesis. In addition to extensively studied planar GNRs consisting of armchair, zigzag, or gulf edges, curved GNRs (cGNRs) bearing cove ([4]helicene unit) or fjord ([5]helicene unit) regions along the ribbon edges have received increasing interest after we presented the first attempt to synthesize the fully cove-edged GNRs in 2015. Profiting from their novel edge topologies, cGNRs usually exhibit an unprecedented narrow band gap and high carrier transport mobility in comparison to the planar GNRs with similar widths. Moreover, cGNRs with particular out-of-plane-distorted structures are expected to provide further opportunities in nonlinear optics and asymmetric catalysis. However, the synthesis of cGNRs bearing cove or fjord edges remains underdeveloped due to the absence of efficient synthetic strategies/methods and suitable molecular precursor design.

中文翻译：

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弯曲石墨烯纳米带的精确结构调控和带隙工程

石墨烯纳米带 (GNR)——准一维石墨烯切口——作为下一代电子和自旋电子材料的有前途的候选者而受到越来越多的关注。理论和实验研究表明，GNR 的电子和磁性特性主要取决于它们的宽度和边缘拓扑结构。因此，结构定义的 GNR 的制备不仅对于它们的基础物理化学研究而且对于它们在碳基纳米电子学中的未来技术发展都是非常可取的。在过去的十年中，人们做出了重大努力，通过自下而上的合成来构建各种具有明确宽度和边缘结构的 GNR。除了广泛研究的由扶手椅、之字形或海湾边缘组成的平面 GNR 之外，在我们于 2015 年首次尝试合成完全凹边的 GNR 后，沿着带状边缘的弯曲 GNR (cGNR) 轴承湾（[4] 螺旋单元）或峡湾（[5] 螺旋单元）区域受到越来越多的关注。从其新颖的边缘拓扑结构来看，与具有相似宽度的平面 GNR 相比，cGNR 通常表现出前所未有的窄带隙和高载流子传输迁移率。此外，具有特定平面外扭曲结构的 cGNR 有望在非线性光学和不对称催化方面提供更多机会。然而，由于缺乏有效的合成策略/方法和合适的分子前体设计，带有海湾或峡湾边缘的 cGNRs 的合成仍然不发达。