文献精选——2D片状量子点材料
本期内容简介：
最新四篇关于二维片状量子点材料的文献分享（InSe，CdSe，PbS）。
2D片状量子点合成方面的经典文献汇总。
文献速递：
The rise of two-dimensional (2D) graphene-cognated crystals with nonzero band gaps like transition metal dichalcogenides has led to a rapidly increasing interest in their dimensionality dependent anisotropic properties, which bear high potential for ultrathin electronics. 2D crystals of the III–VI metal chalcogenide InSe represent a new kind of material class predestined for the use in optoelectronic applications as highly responsive photodetectors and field-effect transistors. We present a solution-processable method for 2D ultrathin InSe nanosheets (≤5 nm with ligands, lateral sizes up to ∼800 μm) with a detailed characterization of the sheet formation by a lamellar ligand templated growth. Optical and electrical transport properties, as well as in depth analysis of the crystal structure and stoichiometry of the colloidal nanosheets by electron and atomic force microscopy, X-ray photoelectron spectroscopy, and scattering methods complete this comprehensive study on a wet-chemical alternative to produce ultrathin InSe nanosheets.
简析：
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首先InSe纳米片是一种新型二维半导体材料，文中提及经典的合成方法是Top-Down的方法。本文运用了更方便的Bottom-Up方法。（个人猜测本文并不是第一个运用Bottom-Up方法，不然应该是JACs了。此外，如果是首创文中必定会特别指出。）
结构表征很完整，文中一再强调。（优点需要反复强调）
PbS nanoplatelets (NPLs) are proposed as robust materials for novel optoelectronic devices. Compared to quantum dot assemblies, ab initio simulations are employed to show that such pseudo-two-dimensional systems may provide stronger absorption and higher carrier mobility due to the distinct wave function distributions, large electronic couplings, and small hopping barriers. More importantly, both energetic and spatial traps are absent in conditions far from charge balance, indicating an extraordinary robustness against off-stoichiometry as a result of surface homogeneity and sufficient cross-linking. Based on our findings, we present several types of optoelectronic device architectures spanning photovoltaics and photodetectors that could take advantage of the superior properties found in NPLs.
同样是关于纳米片，第二篇文章重心则是计算。文中利用ab initio计算方法，分别计算 PbS Quantum Dots和PbS Nano Platelet的能带及电子结构。计算结果表明NPL吸光能力更强，载流子扩散范围更宽，更为重要的是NPL材料能够有效抑制因为Pb ：S非化学计量比而引起的Traps。
In this paper we present a simple method for the preparation of highly stable colloidal solutions of individual nanoplatelets (NPls) with increased fluorescence quantum yield and a versatile procedure of NPls self-assembly into stacks of controlled size. Dynamic light scattering technique has been demonstrated to be simple and accurate method for in situ studies of the growth kinetics of NPls aggregates. The self-assembly method introduced in this work is based on the exchange of ligands on the surface of CdSe nanoplatelets. Hexadecylphosphonic acid allows control of the average size (length) of NPls stacks in a broad range by varying its concentration and reaction time. The main mechanism governing controlled formation of NPls stacks is based on strong van der Waals interaction between rigid brushes of alkyl chains on the surface of neighboring NPls. The interaction strength and, consequently, the length and colloidal stability of stacks have been shown to be dependent on type and concentration of different ligands.
第三篇文献是基于CdSe NanoPlatelets，进行自组装。重点在于对于纳米片材料在溶液中的组装行为。
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利用配体交换的方法实现CdSe纳米片的自组装。不同配体类型，浓度，反应时间对组装行为有着重要的影响。（对于量子点材料，配体的作用尤为重要，无论是合成过程中，还是组装中）
成功的利用DLS（动态光散射）方法原位跟踪自组装过程，并进行动力学分析。
The rational synthesis of hierarchical three-dimensional nanostructures with specific compositions, morphologies and functionalities is important for applications in a variety of fields ranging from energy conversion and electronics to biotechnology. Here, we report a seeded growth approach for the controlled epitaxial growth of three types of hierarchical one-dimensional (1D)/two-dimensional (2D) nanostructures, where nanorod arrays of II–VI semiconductor CdS or CdSe are grown on the selective facets of hexagonal-shaped nanoplates, either on the two basal facets of the nanoplate, or on one basal facet, or on the two basal facets and six side facets. The seed engineering of 2D hexagonal-shaped nanoplates is the key factor for growth of the three resulting types of 1D/2D nanostructures. The wurtzite- and zinc-blende-type polymorphs of semiconductors are used to determine the facet-selective epitaxial growth of 1D nanorod arrays, resulting in the formation of different hierarchical three-dimensional (3D) nanostructures.
最后这篇Natrue Chemitry，作者以纳米片为晶种，在其表面选择性生长纳米柱。我认为最大的亮点是照片很 “酷炫”。（请原谅我的无知）看到文章中的电镜照片和模拟图，不得不感叹控制之精细。可以选择性的生长在纳米片的一面或两面，甚至还可以生长到侧面。（如果你对纳米结构的可控合成很感兴趣，值得仔细研究；如果你是搞催化的，呵呵。）
分享几篇关于片状量子点材料合成的经典文献：
1. Colloidal Synthesis of Ultrathin Two-Dimensional Semiconductor Nanocrystals，Adv. Mater. 2011, 23, 3214–3219.
2. Continuous Transition from 3D to 1D Confinement Observed during the Formation of CdSe Nanoplatelets，J. Am. Chem. Soc., 2011, 133 (9), 3070–3077.
3. Large-Scale Soft Colloidal Template Synthesis of 1.4 nm Thick CdSe Nanosheets,Angew. Chem. Int. Ed. 2009, 48, 6861 –6864.
4. Synthesis, Internal Structure, and Formation Mechanism of Monodisperse Tin Sulfide Nanoplatelets,J. Am. Chem. Soc., 2015, 137 (31), 9943–9952.
5. Thickness-Controlled Synthesis of Colloidal PbS Nanosheets and Their Thickness-Dependent Energy Gaps，Chem. Mater. 2014, 26, 5433−5436.
6. Size/Shape-Controlled Synthesis of Colloidal CdSe Quantum Disks: Ligand and Temperature Effects, J. Am. Chem. Soc., 2011, 133 (17), 6578–6586
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