Materials Science Institute and Department of Chemistry, University of Oregon , Eugene, Oregon 97403, United States.
ACS Nano. 2016 Jul 26;10(7):6942-51. doi: 10.1021/acsnano.6b02796. Epub 2016 Jul 1.
The ability to precisely control the composition of nanocrystals, similar to the way organic chemists control the structure of small molecules, remains an important challenge in nanoscience. Rather than dictating nanocrystal size through the nucleation event, growth of nanocrystals through continuous precursor addition would allow fine structural control. Herein, we present a method of growth for indium oxide nanocrystals that relies on the slow addition of an indium carboxylate precursor into hot oleyl alcohol. Nanocrystal size and structure can be governed at a subnanometer scale, and it is possible to precisely control core size over a range of three to at least 22 nm with dispersities as low as 7%. Growth can be stopped and restarted repeatedly without aggregation or passivation. We show that the volume of the nanocrystal core (and thus molecular weight) increases linearly with added monomer and the number of nanocrystals remains constant throughout the growth process, yielding an extremely predictable approach to size control. It is also possible to place metal oxide shells (e.g., Sn-doped In2O3 (ITO)) at various radial positions within the nanocrystal, and we use this approach to synthesize ITO/In2O3 core/shell nanocrystals as well as In2O3/ITO/In2O3 core/shell/shell nanocrystals.
精确控制纳米晶体组成的能力，类似于有机化学家控制小分子结构的方式，仍然是纳米科学的一个重要挑战。通过连续添加前体来控制纳米晶体的生长，而不是通过成核事件来决定纳米晶体的尺寸，可以实现精细的结构控制。本文介绍了一种通过缓慢添加铟羧酸盐前体制备氧化铟纳米晶体的方法，该方法依赖于在热辛醇中生长。纳米晶体的尺寸和结构可以在亚纳米尺度上进行控制，并且可以精确控制核心尺寸在 3nm 至至少 22nm 的范围内，分散度低至 7%。生长可以反复停止和重新开始，而不会发生聚集或钝化。我们表明，纳米晶核的体积（因此分子量）随单体的增加而线性增加，并且在整个生长过程中纳米晶的数量保持不变，从而提供了一种非常可预测的尺寸控制方法。也可以在纳米晶体的不同径向位置放置金属氧化物壳（例如，掺锡氧化铟（ITO）），我们使用这种方法合成了 ITO/In2O3 核/壳纳米晶体以及 In2O3/ITO/In2O3 核/壳/壳纳米晶体。
