Department of Chemistry, The University of Western Ontario , London, Ontario N6A 5B7, Canada.
Institute of Nanotechnology and Karlsruhe NanoMicro Facility, Karlsruhe Institute of Technology , 76344 Eggenstein-Leopoldshafen, Germany.
J Am Chem Soc. 2017 Jan 25;139(3):1129-1144. doi: 10.1021/jacs.6b10490. Epub 2017 Jan 13.
Superstructures, combining nanoscopic constituents into micrometer-size assemblies, have a great potential for utilization of the size-dependent quantum-confinement properties in multifunctional electronic and optoelectronic devices. Two diverse superstructures of nanoscopic CdSe were prepared using solvothermal conversion of the same cadmium selenophenolate precursor (MeN)[Cd(SePh)]: the first is a superlattice of monodisperse [CdSe(SePh)(dmf)] nanoclusters; the second is a unique porous CdSe crystal. Nanoclusters were crystallized as cubic crystals (≤0.5 mm in size) after solvothermal treatment at 200 °C in DMF. UV-vis absorption and PLE spectra of the reported nanoclusters are consistent with previously established trends for the known families of tetrahedral CdSe frameworks. In contrast to these, results of PL spectra are rather unexpected, as distinct room temperature emission is observed both in solution and in the solid state. The porous CdSe crystals were isolated as red hexagonal prisms (≤70 μm in size) via solvothermal treatment under similar conditions but with the addition of an alkylammonium salt. The presence of a three-dimensional CdSe network having a coherent crystalline structure inside hexagonal prisms was concluded based on powder X-ray diffraction, selected area electron diffraction and electron microscopy imaging. Self-assembly via oriented attachment of crystalline nanoparticles is discussed as the most probable mechanism of formation.
超结构将纳米尺度的成分组合成微米大小的组件，在多功能电子和光电设备中具有利用尺寸相关的量子限制性质的巨大潜力。使用相同的硒化镉硒酚盐（MeN）[Cd（SePh）]前体通过溶剂热转化制备了两种不同的纳米硒的超结构：第一种是单分散[CdSe（SePh）（dmf）]纳米团簇的超晶格；第二种是独特的多孔 CdSe 晶体。纳米团簇在 DMF 中 200°C 的溶剂热处理后结晶为立方晶体（≤0.5mm 大小）。所报道的纳米团簇的 UV-vis 吸收和 PLE 光谱与先前建立的已知四面体 CdSe 框架家族的趋势一致。与这些相反，PL 光谱的结果相当出人意料，因为在溶液和固态中都观察到明显的室温发射。通过在类似条件下但添加烷基铵盐的溶剂热处理，分离出多孔 CdSe 晶体，其为红色六方棱镜（≤70μm 大小）。基于粉末 X 射线衍射、选区电子衍射和电子显微镜成像，得出了六方棱镜内部存在具有连贯晶体结构的三维 CdSe 网络的结论。通过结晶纳米颗粒的取向附着的自组装被讨论为最可能的形成机制。
