Pirquitasite Ag₂ZnSnS₄ (AZTS) nanocrystals (NCs) are emergent, lead-free emissive materials in the coinage chalcogenide family with applications in optoelectronic technologies. Like many multinary nanomaterials, their phase-pure synthesis is complicated by the generation of impurities, e.g., binary/ternary chalcogenides and reducedmetals. Here, we develop a stepwise synthetic procedure that controls the size, morphology, and transformations of acanthite-like (Ag₂S) and canfieldite-like (Ag₈SnS₆) intermediates. This reaction scheme grants the production of small AZTS NCs (diameter: 2.1–4.0 nm) that we cannot achieve through established single-injection procedures─expanding the accessible range of quantum-confined AZTS emission to shorter wavelengths (λ: 650–740 nm). We show that the initial sulfur stoichiometry is the key handle for template-size tunability and reveal that temporally separating transformation steps is crucial to obtaining phase-pure AZTS NCs with emission λ < 740 nm. We then use NMR and optical spectroscopies to demonstrate that the installation of thiol ligands improves colloidal stability, while exposure to carboxylic acids does not. Finally, facilitated by this enhanced synthetic control, we show that our ultrasmall AZTS NCs can act as effective, less-toxic sensitizers for red-to-blue triplet fusion upconversion. Our results highlight transferrable insights for the synthesis and postsynthetic treatment of complex, less-toxic quaternary nanocrystalline systems.

中文翻译：

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逐步反应获得超小的 Ag2ZnSnS4 纳米晶


Pirquitasite Ag₂ZnSnS₄ （AZTS） 纳米晶体 （NC） 是造币硫属化物家族中的新兴无铅发射材料，应用于光电技术。与许多多元纳米材料一样，它们的相纯合成因杂质的产生而变得复杂，例如二元/三元硫属化物和还原金属。在这里，我们开发了一种逐步合成程序，用于控制棘石类 （Ag₂S） 和坎菲尔德石类 （Ag₈SnS₆） 中间体的大小、形态和转化。该反应方案允许产生我们无法通过既定的单次注射程序实现的小 AZTS NC（直径：2.1-4.0 nm）——将量子限制 AZTS 发射的可及范围扩展到更短的波长（λ：650-740 nm）。我们表明初始硫化学计量是模板大小可调性的关键手柄，并揭示了时间分离的转化步骤对于获得发射 λ < 740 nm 的相纯 AZTS NCs 至关重要。然后，我们使用 NMR 和光谱来证明硫醇配体的安装可以提高胶体稳定性，而暴露于羧酸则不会。最后，在这种增强的合成对照的促进下，我们表明我们的超小 AZTS NCs 可以作为红到蓝三重态融合上转换的有效、毒性较小的敏化剂。我们的结果突出了复杂、低毒的季纪纳米晶系统的合成和合成后处理的可转移见解。