Bright full-color silicon quantum dots (SiQDs) are promising heavy-metal-free light sources for displays, lighting, and biomedical imaging. However, the relationships linking the stability, ligand reactivity, and SiQD photoluminescence (PL) are not yet fully understood, and obtaining SiQDs that emit true green PL has proved difficult. Herein, we report the synthesis, via SiBr₄ reduction followed by ligand exchange with a carbazole derivative, of colloidal SiQDs that emit green PL. The PL and ligand stabilities were tracked over a period of 3 months using two-dimensional (2D) PL, Fourier-transform infrared (FTIR), 2D NMR, and time-resolved spectroscopies. True green PL (λ_PL = 530 nm) was emitted by the SiQDs upon excitation using a widely available blue light source (light-emitting diode (LED) flashlight, λ_ex = 450 nm), and the width of the emission band was narrow (∼60 nm). The PL quantum yield (PLQY) was 60%, and the radiative rate was nearly equal to the value expected for direct transitions of QDs. In acetone, the PLQY was constant, but storing the SiQDs in four different alcohols resulted in PLQY increases in the range of 10–50%. This positive aging effect was attributed to alkoxy ligand formation via the reaction between the Br ligands and alcohols. In addition, a blue PL band appeared as a result of aging, and its intensity was enhanced 7-fold after storage of the SiQDs in O₂-saturated ethanol; evidence of energy transfer between the PL bands was observed in frequency- and time-domain measurements. The findings and characterization of the long-term stability reported herein should prove invaluable for future research and applications of colloidal SiQDs.

中文翻译：

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绿色光致发光硅量子点的配体稳定性和反应性：溶液中的正老化


明亮的全彩硅量子点 (SiQD) 是一种有望用于显示器、照明和生物医学成像的无重金属光源。然而，稳定性、配体反应性和 SiQD 光致发光 (PL) 之间的关系尚未完全清楚，并且事实证明获得发射真正绿光 PL 的 SiQD 很困难。在此，我们报道了通过 SiBr ₄ 还原，然后与咔唑衍生物进行配体交换，合成了发出绿色 PL 的胶体 SiQD。使用二维 (2D) PL、傅里叶变换红外 (FTIR)、2D NMR 和时间分辨光谱在 3 个月的时间内跟踪 PL 和配体稳定性。 SiQD 在使用广泛使用的蓝色光源（发光二极管 (LED) 手电筒，λ _ex = 450 激发后发射出真正的绿色 PL (λ _PL = 530 nm) nm），发射带的宽度很窄（~60 nm）。 PL量子产率（PLQY）为60%，辐射率几乎等于QD直接跃迁的预期值。在丙酮中，PLQY 是恒定的，但将 SiQD 存储在四种不同的醇中会导致 PLQY 增加 10-50%。这种积极的老化效应归因于通过 Br 配体和醇之间的反应形成烷氧基配体。此外，SiQDs在O ₂ -饱和乙醇中保存后，老化后出现蓝色PL带，其强度增强了7倍。在频域和时域测量中观察到 PL 波段之间能量转移的证据。本文报告的长期稳定性的发现和表征对于胶体 SiQD 的未来研究和应用具有不可估量的价值。