核/壳结构CdSe/CdS厚壳各向异性骨状纳米晶发光材料
Core/Shell CdSe/CdS Bone-Shaped Nanocrystals with a Thick and Anisotropic Shell as Optical Emitters
摘要：
胶体核/壳纳米晶体是光电子学的关键材料，能够通过精确设计其壳的形状、厚度和晶格结构来控制基本特性。在这里，我们应用生长协议的CdS分支的纳米晶体的CdSe nanoplatite种子，并获得骨形的异质结构具有高度各向异性的外壳。令人惊讶的是，纳米片耐受350 °C的高生长温度，并且我们获得了具有CdSe纳米片芯的结构，所述CdSe纳米片芯被立方CdS壳包覆，在立方CdS壳的顶部形成具有六方晶格的四面体CdS结构。这些复杂的核/壳纳米晶体显示出约657 nm的带边发射，光致发光量子产率为约1000 nm。42%在溶液中，其也保留在薄膜中。有趣的是，纳米晶体表现出同时的红色和绿色的发射，和相对较长的绿色发射波长表明在CdS壳的立方/六方界面的电荷复合。当材料沉积在合适的光栅上时，薄膜显示出放大的自发发射、随机激光和分布反馈激光。我们的工作刺激设计和制造更奇特的核/壳异质结构，其中载流子离域，偶极矩，和其他光学和电学性能可以工程。
英文摘要：
Colloidal core/shell nanocrystals are key materials for optoelectronics, enabling control over essential properties via precise engineering of the shape, thickness, and crystal lattice structure of their shell. Here, we apply the growth protocol for CdS branched nanocrystals on CdSe nanoplatelet seeds and obtain bone-shaped heterostructures with a highly anisotropic shell. Surprisingly, the nanoplatelets withstand the high growth temperature of 350 °C and we obtain structures with a CdSe nanoplatelet core that is overcoated by a shell of cubic CdS, on top of which tetrahedral CdS structures with hexagonal lattice are formed. These complex core/shell nanocrystals show a bandedge emission around 657 nm with a photoluminescence quantum yield of ca. 42 % in solution, which is also retained in thin films. Interestingly, the nanocrystals manifest simultaneous red and green emission, and the relatively long wavelength of the green emission indicates charge recombination at the cubic/hexagonal interface of the CdS shell. The nanocrystal films show amplified spontaneous emission, random lasing, and distributed feedback lasing when the material is deposited on suitable gratings. Our work stimulates the design and fabrication of more exotic core/shell heterostructures where charge carrier delocalization, dipole moment, and other optical and electrical properties can be engineered.
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