Salzmann Bastiaan B V, Vliem Jara F, Maaskant D Nicolette, Post L Christiaan, Li Chen, Bals Sara, Vanmaekelbergh Daniel
Condensed Matter & Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, 3508TA Utrecht, The Netherlands.
EMAT and Nanolab Centre of Excellence, Antwerp University, 2020 Antwerp, Belgium.
Chem Mater. 2021 Sep 14;33(17):6853-6859. doi: 10.1021/acs.chemmater.1c01618. Epub 2021 Aug 24.
The variation in the shape of colloidal semiconductor nanocrystals (NCs) remains intriguing. This interest goes beyond crystallography as the shape of the NC determines its energy levels and optoelectronic properties. While thermodynamic arguments point to a few or just a single shape(s), terminated by the most stable crystal facets, a remarkable variation in NC shape has been reported for many different compounds. For instance, for the well-studied case of CdSe, close-to-spherical quantum dots, rods, two-dimensional nanoplatelets, and quantum rings have been reported. Here, we report how two-dimensional CdSe nanoplatelets reshape into quantum rings. We monitor the reshaping in real time by combining atomically resolved structural characterization with optical absorption and photoluminescence spectroscopy. We observe that CdSe units leave the vertical sides of the edges and recrystallize on the top and bottom edges of the nanoplatelets, resulting in a thickening of the rims. The formation of a central hole, rendering the shape into a ring, only occurs at a more elevated temperature.
胶体半导体纳米晶体（NCs）形状的变化一直引人关注。这种关注超越了晶体学范畴，因为纳米晶体的形状决定了其能级和光电特性。虽然热力学观点表明，纳米晶体通常具有少数几种或仅仅一种由最稳定晶面终止的形状，但已报道许多不同化合物的纳米晶体形状存在显著差异。例如，对于研究充分的CdSe而言，已报道有接近球形的量子点、棒状、二维纳米片以及量子环等。在此，我们报告二维CdSe纳米片如何重塑为量子环。我们通过将原子分辨结构表征与光吸收和光致发光光谱相结合，实时监测这种重塑过程。我们观察到，CdSe单元从纳米片边缘的垂直侧面脱离，并在纳米片的顶部和底部边缘重新结晶，导致边缘增厚。仅在更高温度下才会形成中心孔，从而使形状变为环形。
