As heavy-metal-free alternatives to Cd- and Pb-containing semiconductor nanocrystals (NCs), ternary I–III–VI₂ compounds NCs have been actively studied, especially the CuInS₂ NCs. Recently, it has been found that thick ZnS shelling can greatly improve the photochemical stability of such NCs, which undoubtedly enhances their application potential although it is still limited by the development of synthetic methods. This paper provides a facile method for preparation of thick-shell CuInS₂/ZnS NCs. The effects of reaction temperatures (220∘C and 300∘C) and sulfur precursors (dodecanethiol and sulfur powder) on the shell overgrowth are discussed in detail. When low reaction temperature (220∘C) and inactive sulfur precursor are used, the overgrowth of ZnS shell is considerably slow and raising temperature have a limited impact on the particles’ size. On the contrary, high reaction temperature and reactive sulfur precursor can effectively improve the overgrowth rate of ZnS shell, and then thick-shell CuInS₂/ZnS NCs can be received. Furthermore, a high-speed centrifugation method is used to screen out product NCs with a relatively uniform size.

中文翻译：

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厚壳 CuInS2/ZnS 纳米晶体的合成：温度和硫前体的影响

作为含 Cd 和 Pb 的半导体纳米晶体 (NCs) 的无重金属替代品，三元 I-III-VI ₂化合物 NCs 已得到积极研究，尤其是 CuInS ₂ NCs。最近，人们发现厚的 ZnS 壳层可以极大地提高这种 NCs 的光化学稳定性，这无疑增强了它们的应用潜力，尽管它仍然受到合成方法发展的限制。本文提供了一种制备厚壳CuInS ₂ /ZnS NCs的简便方法。反应温度的影响 (220∘C 和300∘C）和硫前体（十二烷硫醇和硫粉）对壳过度生长进行了详细讨论。当反应温度低（220∘C) 和惰性硫前驱体，ZnS 壳层的过度生长相当缓慢，并且升高温度对颗粒尺寸的影响有限。相反，高反应温度和活性硫前驱体可以有效提高ZnS壳层的过度生长速率，进而可以得到厚壳CuInS ₂ /ZnS NCs。此外，采用高速离心法筛选出尺寸相对均匀的产品NC。