Kaur Harneet, Coleman Jonathan N
School of Physics, CRANN & AMBER Research Centres, Trinity College Dublin, Dublin, D02 PN40, Ireland.
Adv Mater. 2022 Sep;34(35):e2202164. doi: 10.1002/adma.202202164. Epub 2022 Jul 24.
For nearly 15 years, researchers have been using liquid-phase exfoliation (LPE) to produce 2D nanosheets from layered crystals. This has yielded multiple 2D materials in a solution-processable form whose utility has been demonstrated in multiple applications. It was believed that the exfoliation of such materials is enabled by the very large bonding anisotropy of layered materials where the strength of intralayer chemical bonds is very much larger than that of interlayer van der Waals bonds. However, over the last five years, a number of papers have raised questions about our understanding of exfoliation by describing the LPE of nonlayered materials. These results are extremely surprising because, as no van der Waals gap is present to provide an easily cleaved direction, the exfoliation of such compounds requires the breaking of only chemical bonds. Here the progress in this unexpected new research area is examined. The structure and properties of nanoplatelets produced by LPE of nonlayered materials are reviewed. A number of unexplained trends are found, not least the preponderance of isotropic materials that have been exfoliated to give high-aspect-ratio nanoplatelets. Finally, the applications potential of this new class of 2D materials are considered.
近15年来，研究人员一直使用液相剥离法（LPE）从层状晶体中制备二维纳米片。这已产生了多种可溶液加工形式的二维材料，其效用已在多种应用中得到证明。人们认为，此类材料的剥离是由层状材料非常大的键合各向异性实现的，其中层内化学键的强度远大于层间范德华键的强度。然而，在过去五年中，一些论文通过描述非层状材料的液相剥离法，对我们对剥离的理解提出了质疑。这些结果极其令人惊讶，因为由于不存在范德华间隙来提供易于裂解的方向，此类化合物的剥离仅需要破坏化学键。本文考察了这一意外新研究领域的进展。综述了通过非层状材料的液相剥离法制备的纳米片的结构和性能。发现了一些无法解释的趋势，尤其是大量各向同性材料被剥离成高纵横比纳米片的情况。最后，考虑了这类新型二维材料的应用潜力。
