Hefei National Laboratory for Physical Sciences at the Microscale and Collaborative Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China , Hefei, Anhui 230026, People's Republic of China.
Acc Chem Res. 2015 Jan 20;48(1):3-12. doi: 10.1021/ar500164g. Epub 2014 Dec 9.
The ultimate goal of solid state chemistry is to gain a clear correlation between atomic, defect, and electronic structure and intrinsic properties of solid state materials. Solid materials can generally be classified as amorphous, quasicrystalline, and crystalline based on their atomic arrangement, in which crystalline materials can be further divided into single crystals, microcrystals, and nanocrystals. Conventional solid state chemistry mainly focuses on studying single crystals and microcrystals, while recently nanocrystals have become a hot research topic in the field of solid state chemistry. As more and more nanocrystalline materials have been artificially fabricated, the solid state chemistry for studying those nanosolids has become a new subdiscipline: solid state nanochemistry. However, solid state nanochemistry, usually called "nanochemistry" for short, primarily studies the microstructures and macroscopic properties of a nanomaterial's aggregation states. Due to abundant microstructures in the aggregation states, it is only possible to build a simple but imprecise correlation between the microscopic morphology and the macroscopic properties of the nanostructures. Notably, atomically thin two-dimensional inorganic materials provide an ideal platform to establish clear structure-property relationships in the field of solid state nanochemistry, thanks to their homogeneous dispersion without the assistance of a capping ligand. In addition, their atomic structures including coordination number, bond length, and disorder degree of the examined atoms can be clearly disclosed by X-ray absorption fine structure spectroscopy. Also, their more exposed interior atoms would inevitably induce the formation of various defects, which would have a non-negligible effect on their physicochemical properties. Based on the obtained atomic and defect structural characteristics, density-functional calculations are performed to study their electronic structures. Then, after the properties of the individual ultrathin two-dimensional materials or their assembled highly oriented thin film-based nanodevices are measured, the explicit relationship between atomic, defect, and electronic structure and intrinsic properties could be established. In this Account, we focus on our recent advances in the field of solid state nanochemistry, including atomic structure characterization of ultrathin two-dimensional inorganic materials by X-ray absorption fine structure spectroscopy, characterization of their different types of structural defects by positron annihilation spectra and electron spin resonance, and investigation of their electronic structure by density-functional calculations. In addition, we summarize the close correlation between atomic, defect, and electronic structure variations and the optoelectronic, electrical, magnetic, and thermal properties of ultrathin two-dimensional materials. Finally, we also propose the major challenges and opportunities that face solid state nanochemistry. We believe that all the past achievements in ultrathin two-dimensional materials could bring new opportunities for solid state nanochemistry.
固态化学的最终目标是在原子、缺陷和电子结构与固态材料的固有性质之间建立明确的相关性。固态材料通常根据其原子排列分为无定形、准晶和晶体，其中晶体材料可进一步分为单晶、微晶和纳米晶。传统的固态化学主要集中在研究单晶和微晶，而最近纳米晶已成为固态化学领域的热门研究课题。随着越来越多的纳米晶材料被人工制备，研究这些纳米固体的固态化学已成为一个新的分支学科：固态纳米化学。然而，固态纳米化学通常简称为“纳米化学”，主要研究纳米材料聚集态的微观结构和宏观性质。由于聚集态中存在丰富的微观结构，只能在纳米结构的微观形态和宏观性质之间建立一个简单但不精确的相关性。值得注意的是，原子层厚的二维无机材料为在固态纳米化学领域建立明确的结构-性质关系提供了一个理想的平台，这要归功于它们在没有封端配体辅助的情况下均匀分散。此外，通过 X 射线吸收精细结构光谱可以清楚地揭示其原子结构，包括被考察原子的配位数、键长和无序度。此外，其更多暴露的内部原子将不可避免地导致各种缺陷的形成，这将对其物理化学性质产生不可忽视的影响。基于所获得的原子和缺陷结构特征，通过密度泛函计算来研究其电子结构。然后，在测量了单个超薄二维材料或其组装的高度取向薄膜基纳米器件的性能之后，可以建立原子、缺陷和电子结构与固有性质之间的明确关系。在本综述中，我们重点介绍了我们在固态纳米化学领域的最新进展，包括通过 X 射线吸收精细结构光谱对超薄二维无机材料的原子结构进行表征、通过正电子湮没谱和电子自旋共振对其不同类型结构缺陷进行表征以及通过密度泛函计算对其电子结构进行研究。此外，我们总结了原子、缺陷和电子结构变化与超薄二维材料的光电、电学、磁学和热学性质之间的密切关系。最后，我们还提出了固态纳米化学面临的主要挑战和机遇。我们相信，超薄二维材料的所有过去成就都将为固态纳米化学带来新的机遇。
