Size-dependent ligand exchange of colloidal CdSe nanocrystals with S2- ions
Size-dependent ligand exchange of colloidal CdSe nanocrystals with S2- ions
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胶体 CdSe 纳米晶体与 S2- 离子的尺寸依赖性配体交换
DOI：
10.1039/c5ra18192e
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发表时间：
2015
期刊：
影响因子：
3.9
通讯作者：
Dong Angang
中科院分区：
文献类型：
--
作者：
Liu Limin;Zhang Xianfeng;Ji Li;Li Hanwen;Yu Huijuan;Xu Fangjie;Hu Jianhua;Yang Dong;Dong Angang
在胶体纳米晶体（NC）的表面处理中，S2−离子已被广泛用作无金属原子配体，以有效地取代原始的长烃配体。先前的研究专门表明，S2−离子大大淬灭了半导体NC的光致发光（PL）（例如，CdSe和PbS）。在这里，我们报告的影响，S2-处理的发光性能的CdSe纳米粒子是高度依赖于NC的大小。我们观察到一个意想不到的PL增亮现象时，小的CdSe NC（<4 nm）进行S2−处理，然后在空气和光照射的存在下孵育，而PL增强没有观察到在大的CdSe NC（>4 nm）在相同的条件下处理。系统的表征建立了小的CdSe NC中Se 2-和S2-之间的阴离子交换所产生的CdSe/CdS核-壳结构的演变，这与随后的孵育过程一起解释了PL增强。值得注意的是，用（NH 4）2S处理的2.1 nm CdSe NC在孵育2天后表现出高达约40%的PL量子产率（QY），这与在高温下合成的常规疏水CdSe/CdS核-壳NC相当。我们的研究表明，S2−离子除了取代表面涂层配体外，还可以基本上取代小CdSe NC中的Se 2 −，从而在室温下实现高度发光的亲水性CdSe/CdS核壳NC。
In the surface treatment of colloidal nanocrystals (NCs), S2− ions have been widely employed as metal-free atomic ligands to efficiently replace the original long hydrocarbon ligands. Prior studies exclusively show that S2− ions considerably quench the photoluminescence (PL) of semiconductor NCs (e.g., CdSe and PbS) during ligand exchange. Here we report that the influence of S2− treatment on the luminescent properties of CdSe NCs is highly dependent on the NC size. We observe an unexpected PL brightening phenomenon when small CdSe NCs (<4 nm) are subject to S2− treatment followed by incubation in the presence of air and light irradiation, whereas PL enhancement is not observed in large CdSe NCs (>4 nm) treated under the same conditions. Systematic characterization establishes the evolution of CdSe/CdS core–shell structures in small CdSe NCs arising from anion exchange between Se2− and S2−, which in conjunction with the subsequent incubation process accounts for the PL enhancement. Notably, 2.1 nm CdSe NCs treated with (NH4)2S exhibit a PL quantum yield (QY) as high as ∼40% after 2 days of incubation, which is comparable to that of conventional hydrophobic CdSe/CdS core–shell NCs synthesized at high temperatures. Our studies demonstrate that S2− ions can substantially substitute Se2− in small CdSe NCs in addition to replacing the surface-coating ligands, enabling highly luminescent, hydrophilic CdSe/CdS core–shell NCs at room temperature.