We developed a three-step colloidal synthesis of near-infrared (NIR) active Cu–In–Se (CISe)-based nanocrystals (NCs) via a sequential partial cation exchange realized in one pot. In the first step, binary highly copper deficient Cu_2–xSe NCs were synthesized, followed by a partial cation exchange of copper to indium ions, yielding CISe NCs. This reaction allows for a precise control of the composition of the resulting NCs through a simple variation of the ratio between guest-cation precursors and parent NCs. To enhance the stability and the photoluminescence (PL) properties of the NCs, a subsequent ZnS shell was grown in the third step, resulting in CISeS/ZnS core/shell particles. These core/shell hetero-NCs exhibited a dramatic increase in size and a restructuring to trigonal pyramidal shape. The shell growth performed at a relatively high temperature (250 °C) also led to anion exchange, in which sulfur replaced part of selenium atoms close to the surface of the NCs, forming alloyed CISeS core structure. This efficient anion exchange is rarely reported for I–III–VI-based nanomaterials. Furthermore, we demonstrated that at higher reaction temperature, it is possible to obtain In-rich CISeS/ZnS NCs whose emission was shifted to the visible region. Therefore, a careful tuning of the reaction parameters, such as the Cu:Se and Cu:In ratios, temperature, and time, enables a distinct control over the size and composition of the NCs while maintaining their crystal structure. By varying the size of the CISeS/ZnS NCs from 9 to 18 nm, the PL spectra could be tuned, covering a wide NIR range with maxima from 990 to 1210 nm. Thus, in these experiments, we demonstrated a clear dependence of the optical properties of these materials on their size and extended the PL range of CISe-based NCs further to the infrared part of the spectrum. The results obtained might be important not only to elucidation of fundamentals of ion exchange reactions but also may provide a general preparative approach to a wide variety of copper chalcogenide-based NCs with well-controlled size, shape, composition, and even crystal structure.

中文翻译：

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通过阳离子交换的近红外基于Cu-In-Se的胶体纳米晶体

我们通过在一个罐中实现顺序的部分阳离子交换，开发了一个三步胶体合成近红外（NIR）活性Cu-In-Se（CISe）基纳米晶体（NCs）。第一步，二元高度缺铜的Cu _{2- x}合成了Se NCs，然后将铜部分阳离子交换为铟离子，得到CISe NCs。该反应可通过简单改变客体阳离子前体与母体NC的比例来精确控制所得NC的组成。为了增强NC的稳定性和光致发光（PL）特性，在第三步中生长了后续的ZnS壳，得到CISeS / ZnS核/壳颗粒。这些核/壳异质NC的尺寸显着增加，并重组为三角锥形状。在相对较高的温度（250°C）下进行的壳生长还导致阴离子交换，其中硫取代了接近NCs表面的部分硒原子，形成了合金化的CISeS核结构。对于基于I–III–VI的纳米材料，很少有这种有效的阴离子交换的报道。此外，我们证明了在较高的反应温度下，可以获得富In的CISeS / ZnS NCs，其发射移至可见区。因此，仔细调整反应参数（例如Cu：Se和Cu：In的比例，温度和时间），可以在控制NC晶体结构的同时，对NC的尺寸和组成进行独特的控制。通过将CISeS / ZnS NCs的大小从9 nm更改为18 nm，可以调谐PL光谱，覆盖很大的NIR范围，最大值从990 nm到1210 nm。因此，在这些实验中，我们证明了这些材料的光学特性对它们尺寸的明显依赖，并将基于CISe的NC的PL范围进一步扩展到了光谱的红外部分。