Bera Suman, Behera Rakesh Kumar, Pradhan Narayan
School of Materials Sciences, Indian Association for the Cultivation of Science, Kolkata 700032 India.
J Am Chem Soc. 2020 Dec 9;142(49):20865-20874. doi: 10.1021/jacs.0c10688. Epub 2020 Nov 25.
Bright lead halide perovskite nanocrystals, which have been extensively studied in the past 5 years, are mostly confined to a six faceted hexahedron (cube/platelet) shape. With variations of ligand, precursor, reaction temperature, and surface modification, their brightness has been enhanced and phase became stable, but ultimate nanocrystals still retained the hexahedron cube or platelet shape in most of the hot injection reactions. In contrast, by exploration of α-halo ketone in amine as a halide precursor, different shaped nanocrystals without compromising the photoluminescence quantum yield (PLQY) are reported. Confining to orthorhombic CsPbBr, the obtained nanocrystals are stabilized by 12 facets ({200}, {020}, {112}) and led to 12 faceted rhombic dodecahedrons. These facets are absolutely different from six ({110}, {002}) equivalent facets of widely reported orthorhombic cube shaped CsPbBr nanocrystals. These also retained the colloidal and phase stability, as well as showed near unity PLQY. With further annealing, these are transformed to 26 faceted rhombicuboctahedrons by dissolving all their vertices. Importantly, these 12 faceted nanocrystals showed wide area self-assembly in most of the reactions. It has also been concluded that primary ammonium ions led to six faceted nanocrystals, but tertiary ammonium ions obtained in this case stabilized different group of facets. While perovskite nanocrystals were broadly confined to only nanocubes, these new nanocrystals with intense emission would certainly provide a new avenue for continuing their further research.
在过去5年中得到广泛研究的明亮的卤化铅钙钛矿纳米晶体，大多局限于六面的六面体（立方体/片状）形状。随着配体、前驱体、反应温度和表面改性的变化，它们的亮度得到了提高，相也变得稳定，但在大多数热注入反应中，最终的纳米晶体仍然保持六面体立方体或片状形状。相比之下，通过探索胺中的α-卤代酮作为卤化物前驱体，报道了在不降低光致发光量子产率（PLQY）的情况下得到的不同形状的纳米晶体。对于正交晶系的CsPbBr，所获得的纳米晶体由12个面（{200}、{020}、{112}）稳定，形成了12面的菱形十二面体。这些面与广泛报道的正交晶系立方体形状的CsPbBr纳米晶体的六个（{110}、{002}）等效面完全不同。它们还保持了胶体稳定性和相稳定性，并显示出接近单位的PLQY。通过进一步退火，通过溶解所有顶点，它们转变为26面的菱形立方八面体。重要的是，这些12面的纳米晶体在大多数反应中表现出大面积的自组装。还得出结论，伯铵离子导致形成六面的纳米晶体，但在这种情况下获得的叔铵离子稳定了不同组的面。虽然钙钛矿纳米晶体大多只局限于纳米立方体，但这些具有强烈发射的新型纳米晶体肯定会为继续深入研究提供一条新途径。
