Among cadmium-free quantum dots (QDs), ternary or quaternary chalcogenide semiconductor QDs composed of groups 11, 13, and 16 elements have extensively been studied. Herein, monodispersed quaternary nanoparticles of silver indium gallium sulfide (AgIn_xGa_1–xS₂) are synthesized by a new route that specifically produces the target product without solid byproducts. The difference in the reactivity between groups 11 and 13 metals with chalcogen is a common issue in synthesizing the groups 11, 13, and 16 ternary or quaternary semiconductor QDs. Instead of a common approach to suppress the reactivity of group 11 metals, this study utilizes their high reactivity; rapid injection of a Ag source into the solution containing a thiocarboxylate produced small Ag₂S nanoparticles. These Ag₂S nanoparticles are then exposed to indium-, gallium-, and sulfur-containing species in situ and then converted into quaternary nanoparticles comprising AgIn_xGa_1–xS₂. Due to the well-controlled reaction steps, the product yield based on Ag was increased to 60%, which significantly exceeds that obtained using our previous approach of heating all-mixed raw materials (5–15%). After coating with gallium sulfide (GaS_y) shells, the core/shell QDs exhibited an intense, green-colored band-edge emission with a tunable peak wavelength between 499 and 543 nm. The excellent uniformity of the core nanoparticles in terms of size and composition demonstrated a quite narrow band-edge emission with the full width at half maximum of 31 nm, which is equal to the record-narrow values of green-emitting cadmium-free QDs. Additionally, a near-unity photoluminescence quantum yield was achieved after postsynthetic surface treatment by alkylphosphines, indicating the defect-free nature of the prepared AgIn_xGa_1–xS₂/GaS_y core/shell QD system.

中文翻译：

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Ag-In-Ga-S 季量子点的简便高产合成和硫化镓壳涂层的窄带边发射

在无镉量子点 (QD) 中，由第 11、13 和 16 族元素组成的三元或四元硫族化物半导体 QD 已得到广泛研究。在此，银铟镓硫化物的单分散四元纳米颗粒（AgIn _x Ga _{1– x} S ₂) 是通过一条新路线合成的，该路线专门生产目标产品，没有固体副产品。第 11 族和第 13 族金属与硫属元素的反应性差异是合成第 11、13 和 16 族三元或四元半导体 QD 的常见问题。这项研究没有采用抑制第 11 族金属反应性的常用方法，而是利用了它们的高反应性；将 Ag 源快速注入含有硫代羧酸盐的溶液中会产生小的 Ag ₂ S 纳米颗粒。然后将这些 Ag ₂ S 纳米粒子原位暴露于含铟、镓和硫的物质，然后转化为包含 AgIn _x Ga _{1– x} S _{2的四元纳米粒子}. 由于控制良好的反应步骤，基于 Ag 的产品收率增加到 60%，这大大超过了我们之前使用加热全混合原料的方法获得的收率 (5-15%)。涂上硫化镓（GaS _y) 壳，核/壳 QD 表现出强烈的绿色带边发射，可调谐峰值波长在 499 和 543 nm 之间。核心纳米颗粒在尺寸和组成方面的出色均匀性表明其带边发射非常窄，半峰全宽为 31 nm，这与无镉绿色量子点的创纪录窄值相当。_{此外，在用烷基膦进行合成后表面处理后，实现了接近统一的光致发光量子产率，表明所制备的 AgIn x} Ga _{1– x} S ₂ /GaS _y核/壳 QD 系统具有无缺陷的特性。